cosmopterix lienigiella is a moth of the cosmopterigidae family .

it is found from fennoscandia to spain , the alps and greece and from ireland to ukraine .

it is also present in eastern russia and japan .

it is the type species of the cosmopterix genus .

the wingspan is 10 – 13 mm .

adults are on wing from september to april .

the larvae feed on phragmites australis .

they mine the leaves of their host plant .

the mine starts as a gallery , but soon widens to a broad blotch , entirely or partly running upwards , in the end half as wide as the leaf .

most frass is concentrated in the first section .

pupation takes place in a cocoon in the top section of the mine .

cosmopterix lienigiella

cosmopterix lienigiella ( fen cosmet ) - norfolk micro moths - the micro moths of norfolk .
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most habitats where foodplant grows , preference for large reed beds in fresh and brackish water .
recorded in 15 ( 22 % ) of 69 10k squares . first recorded in 1874 . last recorded in 2017 .
underlying maps using digital map data © norfolk online lepidoptera archive - nola™ 2018 . © james wheeler - n o r f o l k m o t h s 2007 - 2018 . data © nola™ 2018
species , which all have variations of blackish , bright orange and silver metallic markings , this species is rather more reserved in coloration , whilst having similar patterning .
it occurs in southern and south - east england , inhabiting reedbeds , and moths are on the wing between late may and october .
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leaf - miner : makes an elongate mine with frass heaped at the start and then dispersed thoughout . it does not make a silken shelter and so may be seen in the mine ( british leafminers ) .
at first a gallery , but soon widened to a broad blotch , entirely or partly running upwards , in the end half as wide as the leaf . the mine is widened without consideration for the length veins , making the mine less sharply delineated than in c . scribaiella . most frass in the first section , but higher up still some scattered frass visible . unlike c . scribaiella the larva does not spin a shelter for retreat in the mine ; this makes the larva easily visible in the unopened mine . cocoon in the top section of the mine . the pupa lies head - upwards , just below an opening that has been prepared as an exit for the later moth ( bladmineerders van europa ) .
larva : the larvae of moths have a head capsule and chewing mouthparts with opposable mandibles ( see video of a gracillarid larva feeding ) , six thoracic legs and abdominal legs ( see examples ) .
pupa : the pupae of moths have visible head appendages , wings and legs which lie in sheaths ( see examples ) .
adult : the adult is illustrated in ukmoths by alan drewitt . the species is included in urltoken .
distribution in great britain and ireland : britain including cambridgeshire , dorset , east kent , east norfolk , east suffolk , huntingdonshire , isle of wight , north essex , north hampshire , north somerset , south devon , south essex , south hampshire and west norfolk ( nbn atlas ) .
found in large reed beds in fresh and brackish water . found in southern england and norfolk and suffolk ( british leafminers ) .
also recorded in the republic of ireland ( karsholt and van nieukerken in fauna europaea ) . see also ireland ' s nbdc interactive map .
distribution elsewhere : widespread in continental europe including austria , belarus , belgium , bulgaria , czech republic , danish mainland , estonia , finland , french mainland , germany , greek mainland , hungary , latvia , lithuania , norwegian mainland , poland , spanish mainland , sweden , switzerland and the netherlands ( karsholt and van nieukerken in fauna europaea ) .
if you have images for this taxon that you would like to share with nbn atlas , please upload using the upload tools .
ws : 10 - 13 ; may - oct ; common reed ( phragmites australis ) ; local in se . england from dorset to norfolk
§1 snettisham , norfolk ; 12 / 06 / 2014 ; male ; fw 6 . 1mm §2 strumpshaw fen , norfolk ; 10 / 07 / 2015 ; male ; fw 6 . 1mm ; to light all images © chris lewis
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a rare species in belgium , only known from the provinces of oost - vlaanderen and antwerpen .
the adults fly in june and july . they fly around the foodplant at dusk and later come to light .
belgium , antwerpen , viersel , 20 june 2005 . ( photo © maarten jacobs )


poloma angulata is a moth in the eupterotidae family .

it was described by walker in 1855 .

it is found in south africa ( kwazulu-natal , western cape ) .

adults are brown , reddish ferruginous beneath .

the wings have two zigzag slender middle brown bands , the outer one with a testaceous border on the outer side .

these bands are more undulating on the underside .

the forewings are several shades of brown , with a slightly curved testaceous band at one-fourth of the length , and with a very large reddish ferruginous patch along the middle part of the costa .

this patch is deeply notched on its hind side , and contains a brown dot and a zigzag brown streak .

the underside and hindwings are reddish ferruginous .

the larvae feed on olinia ventosa and canthium ventosum .

poloma angulata

poloma walker , 1855 ; list spec . lepid . insects colln br . mus . 4 : 858 ; ts : poloma angulata walker
poloma angulata walker , 1855 ; list spec . lepid . insects colln br . mus . 4 : 858 ; tl : port natal , cape
poloma ( eupteronini ) ; forbes , 1955 , tijdschr . ent . 98 : 130
type species : poloma angulata walker , 1855 . list of the specimens of lepidopterous insects in the collection of the british museum . part iv . – lepidoptera heterocera : 858–859 . by monotypy .
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nb : the taxon name search is for single names only . for example , to locate dysodia vitrina flammata warren , 1904 you should enter flammata only .
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distant w . l . 1903 . insecta transvaaliensia : a contribution to a knowledge of the entomology of south africa . order lepidoptera . suborder heterocera . - — : 49–96 , pls . iii–viii .
vári l . , kroon d . m . & krüger m . 2002 . classification and checklist of the species of lepidoptera recorded in southern africa . - — : i–xxi , 1–385 .
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[ south africa , kwazulu - natal ] , port natal [ durban ] , leg . gueinzius ; cape [ cape province ] , leg . dergé , zoolu country , leg . g . f . angas .
walker f . 1855b . list of the specimens of lepidopterous insects in the collection of the british museum . part iv . — lepidoptera heterocera . - — 4 : i—iv , 777—976 .
taylor j . s . 1949b . notes on lepidoptera in the eastern cape province ( part i ) . - journal of the entomological society of southern africa 12 : 78—95 , 2 pls . .
pinhey e . c . g . 1975 . moths of southern africa . descriptions and colour illustrations of 1183 species . - — : i—iv , 1—273 , pls . 1—63 .
observation - multimammate mouse - southern africa . description : only caught at night in both grasslands and thicket ( added as a separate record ) .
only caught at night in both grasslands and thicket ( added as a separate record ) .
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walker , 1855 list of the specimens of lepidopterous insects in the collection of the british museum list spec . lepid . insects colln br . mus . 1 : 1 - 278 ( 1854 ) , 2 : 279 - 581 ( 1854 ) , 3 : 583 - 775 ( 1855 ) , 4 : 777 - 976 ( 1855 ) , 5 : 977 - 1258 ( 1855 ) , 6 : 1259 - 1508 ( 1855 ) , 7 : 1509 - 1808 ( 1856 )
if you have corrections , comments or information to add into these pages , just send mail to markku savela keep in mind that the taxonomic information is copied from various sources , and may include many inaccuracies . expert help is welcome .
walker f . 1855b . list of the specimens of lepidopterous insects in the collection of the british museum . part iv . – lepidoptera heterocera . - — 4 : i–iv , 777–976 .
aurivillius c . 1901b . on the ethiopean genera of the family striphnopterygidae . - bihang till kongliga svenska vetenskaps akademiens handlingar 27 ( 7 ( suppl . ) ) : 1–33 , pls . 1–5 .
walker f . 1865b . list of the specimens of lepidopterous insects in the collection of the british museum . part xxxii . – supplement part 2 . - — 32 : i–iv , 323–706 .
felder c . , felder r . & rogenhofer a . f . 1865–1875 . reise der österreichischen fregatte novara um die erde in den jahren 1857 , 1858 , 1859 unter den befehlen des commodore b . von wüllerstorf - urbair . zoologischer theil . zweiter band . abtheilung 2 , heft 4 , lepidoptera . atlas der heterocera . - — 2 ( 4 ) : 1–20 , pls . 1–140 .
druce h . 1896 . descriptions of some new species of heterocera from tropical africa . - annals and magazine of natural history ( 6 ) 17 ( 101 ) : 350–356 .
aurivillius c . 1893 . diagnosen neuer lepidopteren aus afrika . - entomologisk tidskrift 14 ( 3 ) : 199–214 .
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to cite this page : myers , p . , r . espinosa , c . s . parr , t . jones , g . s . hammond , and t . a . dewey . 2018 . the animal diversity web ( online ) . accessed at https : / / animaldiversity . org .
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noctueliopsis virula is a moth in the crambidae family .

it was described by barnes and mcdunnough in 1918 .

it is found in north america , where it has been recorded from arizona , california and nevada .

the length of the forewings is 5 – 6 mm .

the forewings are olivaceous brown with a slight ruddy tinge .

there is a white shade at the base above the inner margin .

the lines are black .

the hindwings are pure white with faint brown terminal dots in males .

the hindwings of the females have a brown terminal line .

adults are on wing from march to april and in june .

noctueliopsis virula

the original description as noctuelia virula barnes & mcdunnough is available online in the print references below .
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powell , j . a . & p . a . opler , moths of western north america , pl . 22 . 3m ; p . 171 . book review and ordering
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upcoming events 2018 bugguide gathering in virginia july 27 - 29 : registration and discussion photos of insects and people from the 2015 gathering in wisconsin , july 10 - 12 photos of insects and people from the 2014 gathering in virginia , june 4 - 7 . photos of insects and people from the 2013 gathering in arizona , july 25 - 28 photos of insects and people from the 2012 gathering in alabama photos of insects and people from the 2011 gathering in iowa photos from the 2010 workshop in grinnell , iowa photos from the 2009 gathering in washington
barnes & mcdunnough 1918 . contributions to the natural history of the lepidoptera of north america , 4 : 168 , pl . 23 , fig . 9 .
munroe , e . g . 1961 : synopsis of the north american odontiinae , with descriptions of new genera and species ( lepidoptera : pyralidae ) . – memoirs of the entomological society of canada , ottawa 93 ( 24 ) : 49 .
powell , j . a . , & p . a . opler 2009 . moths of western north america . p . 171 , pl . 22 . 3 .
synopsis of the north american odontiinae , with descriptions of new genera and species ( lepidoptera : pyralidae ) eugene g . munroe . 1961 . memoirs of the entomological society of canada . 93 ( 24 ) : 1 - 93 .
contributed by maury j . heiman on 20 october , 2011 - 11 : 38pm additional contributions by kyhl austin last updated 17 may , 2016 - 7 : 53pm
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memoirs of the entomological society of canada . 93 ( 24 ) : 1 - 93 , 1961
contributed by maury j . heiman on 22 april , 2013 - 12 : 29pm
kearfott , w . d . 1909 . descriptions of new species of north american crambid moths . proceedings of the united states national museum 35 : 367 - 393 .
a generic revision of the aquatic moths of north america : ( lepidoptera : pyralidae , nymphulinae ) .
solis m . a . , 2009 . transfer of all western hemisphere cybalomiinae to other subfamilies ( crambidae pyraloidea : lepidoptera ) : elusia schaus , dichochroma forbes , schacontia dyar , cybalomia extorris warren , and c . lojanalis ( dognin ) . proceedings of the entomological society of washington . 111 : 493–504 download at researchgate here
studies on the crambidae ( lepidoptera ) . part 41 . on some tropical crambidae with descriptions of new genera and species .
nacoleia charesalis ( walker , 1859 ) ( pyraloidea : crambidae : spilomelinae ) is a medium - sized brown moth with a native range from the southeast asian tropics to northern australia . it was first detected in southern florida , usa , in 2012 and known to be spreading rapidly northward . it resembles some native north american pyraustine species . this paper summarizes its current distribution , diagnostic characters and known behavior . download pdf here
description of last - instar larvae of 22 species of north american spilomelini ( lepidoptera : pyralidae : pyraustinae ) . . .
description of last - instar larvae of 22 species of north american spilomelini ( lepidoptera : pyralidae : pyraustinae ) with a key to species . abstract and access
contributed by maury j . heiman on 11 june , 2013 - 3 : 18pm
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a planarian is one of many flatworms of the turbellaria class .

it is also the common name for a member of the genus planaria within the family planariidae .

sometimes it also refers to the genus dugesia .

planaria are common to many parts of the world , living in both saltwater and freshwater ponds and rivers .

some species are terrestrial and are found under logs , in or on the soil , and on plants in humid areas .

planaria exhibit an extraordinary ability to regenerate lost body parts .

for example , a planarian split lengthwise or crosswise will regenerate into two separate individuals .

some planarian species have two eye-spots ( also known as ocelli ) that can detect the intensity of light , while others have several eye-spots .

the eye-spots act as photoreceptors and are used to move away from light sources .

planaria have three germ layers ( ectoderm , mesoderm , and endoderm ) , and are acoelomate ( they have a very solid body with no body cavity ) .

they have a single-opening digestive tract ; in tricladida planarians this consists of one anterior branch and two posterior branches .

planarians move by beating cilia on the ventral dermis , allowing them to glide along on a film of mucus .

some also may move by undulations of the whole body by the contractions of muscles built into the body membrane .

triclads play an important role in watercourse ecosystems and are often very important as bio-indicators .

the most frequently used planarian in high school and first-year college laboratories is the brownish girardia tigrina .

other common species used are the blackish planaria maculata and girardia dorotocephala .

recently , however , the species schmidtea mediterranea has emerged as the species of choice for modern molecular biological and genomic research due to its diploid chromosomes and the existence of both asexual and sexual strains .

recent genetic screens utilizing double-stranded rna technology have uncovered 240 genes that affect regeneration in s. mediterranea .

many of these genes have orthologs in the human genome .

planarian

the maintenance and regeneration of the planarian excretory system are regulated by egfr signaling .
structure of the planarian central nervous system ( cns ) revealed by neuronal cell markers .
[ regulation of asexual reproduction in the planarian dugesia tigrina ] . - pubmed - ncbi
existence of two sexual races in the planarian species switching between asexual and sexual reproduction .
mead , r . and christman , j . , proportion regulation in the planarian ,
that ' s exactly what happened with earlier attempts to sequence the planarian and axolotl genomes .
below are summarized the function and structure of the brain of a planarian , dugesia japonica .
planarian regeneration : achievements and future directions after 20 years of research . - pubmed - ncbi
the maintenance and regeneration of the planarian excretory system are regulated by egfr signaling . - pubmed - ncbi
structure of the planarian central nervous system ( cns ) revealed by neuronal cell markers . - pubmed - ncbi
existence of two sexual races in the planarian species switching between asexual and sexual reproduction . - pubmed - ncbi
- positive neurons ( magenta ) in the planarian brain ( a , b ) . a is a horizontal view of planarian whole brain . b shows the dorsal region at high magnification . white arrowheads indicate the colocalization of
hori , i . and kishida , y . , a fine structural study of regeneration after fission in the planarian
hori , i . and kishida , y . , further observation on the early regeneration after fission in the planarian
switching from asexual to sexual reproduction in the planarian dugesia ryukyuensis : change of the fissiparous capacity along with the sexualizing process .
the planarian will swim in a shallow petri dish by undulating its body across the surface of the dish . most will stay close to the bottom or the edge of the dish . if given a choice , the planarian will actively seek an area of the dish that is dark or has some kind of cover . the eyespots can in fact , detect changes in light in the planarian ' s environment . if you shine a flashlight on the planarian , it will attempt to move out of the light .
for the planarian , the researchers were able to identify roughly 1 , 000 likely genes that are probably specific to these organisms .
is the name of one genus , but the name planarian is used to designate any member of the family planariidae and related families .
in the planarian ( an aquatic , ciliated flatworm ) , on the other hand , the kinetic response affects only the rate at which the planarian changes its direction . because planaria tend to stay in or return to darker areas , an increase in light intensity causes an increase in their turning…
what made you want to look up planarian ? please tell us where you read or heard it ( including the quote , if possible ) .
nicolas c , abramson c , levin m . analysis of behavior in the planarian model in : raffa r , rawls s . , eds .
expression patterns of xenopus fgf receptor - like 1 / nou - darake in early xenopus development resemble those of planarian nou - darake and xenopus fgf8 .
- positive region may work as a signal processing center of the brain . the domain structure of the planarian brain is summarized in fig . 2 .
tazaki , a . , gaudieri , s . , ikeo , k . , gojobori , t . , watanabe , k . , agata k ( 1999 ) neural network in planarian revealed by an antibody against planarian synaptotagmin homologue : biochem . biophys . res . cmmun . , 260 , 426 - 432
cebrià f . ( 2008 ) organization of the nervous system in the model planarian schmidtea mediterranea : an immunocytochemical study : neurosci . res . , in press
switching from asexual to sexual reproduction in the planarian dugesia ryukyuensis : change of the fissiparous capacity along with the sexualizing p . . . - pubmed - ncbi
a mini - documentary discussing the remarkable regenerative capabilities of the planarian , and how hhmi researcher alejandro sánchez alvarado uses them to study the biology of stem cells .
sheiman , i . m . , kreshchenko , n . d . , sedel’nikov , z . v . , and groznyi , a . v . , morphogenesis in planarian
expression patterns of xenopus fgf receptor - like 1 / nou - darake in early xenopus development resemble those of planarian nou - darake and xenopus fgf8 . — physiology , anatomy and genetics
during sexual reproduction , planarians mate with each other and then—since planarians are hermaphrodites—each planarian lays a cocoon , a small circular egg sac , tethered to a fixed surface in the environment .
agata k . and umesono y . ( 2008 ) brain regeneration from pluripotent stem cells in planarian : phil . trans . r . soc . b . , 363 , 2071 - 2078
planarian regeneration was one of the first models in which the gradient concept was developed . morphological studies based on the analysis of the regeneration rates of planarian fragments from different body regions , the generation of heteromorphoses , and experiments of tissue transplantation led t . h . morgan ( 1901 ) and c . m child ( 1911 ) to postulate different kinds of gradients responsible for the regenerative process in these highly plastic animals . however , after a century of research , the role of morphogens in planarian regeneration has yet to be demonstrated . this may change soon , as the sequencing of the planarian genome and the possibility of performing gene functional analysis by rna interference ( rnai ) have led to the isolation of elements of the bone morphogenetic protein ( bmp ) , wnt , and fibroblast growth factor ( fgf ) pathways that control patterning and axial polarity during planarian regeneration and homeostasis . here , we discuss whether the actions of these molecules could be based on morphogenetic gradients .
okamoto , k . , takeuchi , k . , agata , k . ( 2005 ) neural projections in planarian brain revealed by fluorescent dye tracing : zoolog . sci . , 22 , 535 - 546
newmark , p . a . , and a . sànchez alvarado . 2002 . not your father ' s planarian : a classic model enters the era of functional genomics . nature reviews 3 : 210–19 .
thompson received his degree and went to louisiana state university to work with rats , while mcconnell , upon his arrival at michigan , stuck with worms . he knew that by cutting a planarian across the middle into head and tail sections , each part would regenerate its missing half . but , he wondered , if you conditioned a planarian , which half of the bisected beast would retain the conditioned response ? working with two students in the newly formed planarian research group , mcconnell found , to his astonishment and delight , that the regenerated tails showed as much retention — and in some cases more — than the regenerated heads .
there is a large variety of freshwater planarian species . different species and even different strains within a species reproduce in different ways . some planarians reproduce sexually , others asexually , and some are capable of both .
we have established the first uk laboratory to utilize the planarian model system . the group remains , to our knowledge , the only group in the uk dedicated to exploiting planarians for biomedical and evolutionary studies . our research programme leverages the planarian model system to study basic questions in relation to regeneration and stem cell biology . furthermore , i believe we can use planarians to study the molecular mechanisms related to both aging and cancer
in this primer article , we review the state - of - the - art of planarian research , focusing on stem cells , neural regeneration and reestablishment of polarity , and discuss how the knowledge gained from planarian research might be translated to higher organisms . we aim to bring the attention of the broader scientific community to these amazingly plastic animals as a promising model organism for the rapidly progressing fields of regenerative medicine and bioengineering .
in his book , the first brain , dr . oné r . pagán , a neurobiology and pharmacology specialist from west chester university , discusses how the planarian has played a key role in biological , neuropharmacological , and zoological research ( and how it has made appearances in a few unexpected places in popular culture ) . ultimately , he shows us why the planarian truly is one of the most extraordinary and influential organisms in scientific research today .
reader terri shofner then alerted us to ho ' s video of the odd - looking creature , which experts say is likely an unknown species of the genus bipalium , known by the common names hammerhead worm and broadhead planarian .
kobayashi c . , saito y . , ogawa k . and agata k . ( 2007 ) wnt signaling is required for antero - posterior patterning of the planarian brain : dev . biol . , 306 , 714 - 724
they are also unique among invertebrates in that they display addiction - like behaviors to many drugs that are abused by humans . because of these distinct traits , the planarian is often used as an animal model in neurological research .
cebrià f . , guo t . , jopek j . and newmark p . a . ( 2007b ) regeneration and maintenance of the planarian midline is regulated by a slit orthologue dev . biol . , 307 , 394 - 406
sarnat , h . b . , netsky , m . g . ( 1985 ) the brain of the planarian as the ancestor of the human brain : can . j . neurol . sci . , 12 , 196 - 302
a mini - documentary discussing the remarkable regenerative capabilities of the planarian , and how hhmi researcher alejandro sánchez alvarado uses them to study the biology of stem cells . to download this film or to find related materials , go to urltoken
these example sentences are selected automatically from various online news sources to reflect current usage of the word ' planarian . ' views expressed in the examples do not represent the opinion of merriam - webster or its editors . send us feedback .
cebrià f . and newmark p . a . ( 2005 ) planarian homologs of netrin and netrin receptor are required for proper regeneration of the central nervous system and the maintenance of nervous system architecture : development , 132 , 3691 - 3703
koinuma , s . , umesono , y . , watanabe , k . , agata , k . ( 2003 ) the expression of planarian brain factor homologs , djfoxg and djfoxd : gene expr . patterns , 3 , 21 - 27
classical morphological studies revealed that planarian neurons more closely resemble the neurons of vertebrates than those of higher invertebrates ( sarnat and netsky , 1985 ) . planarian neurons have a large egg - shaped nucleus , scattered agglomerated chromatin and large nuclear bodies . synaptic vesicles are observed in the neuropile . the synaptic structure observed in the brain and peripheral ganglia is basically similar to the chemo - synapse of vertebrates . in both synaptic structures , thickened pre - and post - synaptic membranes and accumulation of clear vesicles in the pre - synaptic region are observed ( oosaki et al . , 1965 ) . extensive molecular studies showed that the planarian brain is composed of functionally diverse neurons which express homologs of specific genes seen in mammalian neurons .
umesono , y . , watanabe , k . , agata , k . ( 1999 ) distinct structural domains in the planarian brain defined by the expression of evolutionarily conserved homeobox genes : dev . genes . evol , 209 , 31 - 39
the functional conservation of signal transduction pathways – exemplified by the roles of wnt / β - catenin and bmp pathways in axis polarity in both planarians and vertebrates – offers the opportunity to study mammalian development and disease using planarian regeneration as a model .
umesono , y . , watanabe , k . , agata , k . ( 1997 ) a planarian orthopedia homolog is specifically expressed in the branch region of both the mature and regenerating brain : dev . growth differ . , 39 , 723 - 727
before arriving at a graduate program next fall , i will have the chance to continue research in planarian regeneration under the supervision of prof . robert major . specifically , i am investigating the interactions of the highly conserved wnt signaling pathway and a protein implicated in aging , sir2 , in order to explore the molecular interface between injury and a regenerative response . the planarian is an interesting organism in that developmental and regenerative processes largely overlap , and , to me , this perfectly mirrors and encapsulates my broader research interests .
( dugesia japonica pro - hormone convertase 2 ) rna probe as a pan - neural marker . anterior is up and posterior is down . the white region in the center of the body is a pharynx . ( b ) a model of the planarian brain .
when planarian flatworms are cut in half , each piece grows back the end that is missing . cells in essentially identical regions of the body where the cut was made form blastemas , which , in one case gives rise to a head and in the other becomes a…
cut a planarian in half and you get two planarians . these non - parasitic flatworms live in water or moist environments on land . there are thousands of species , ranging in size from less than a millimetre to the 60 - centimetre predatory flatworm bipalium kewense . planarians regenerate their tissues by cell proliferation and by remodelling existing tissues with undifferentiated stem cells called neoblasts that are distributed throughout the animal ' s body . pieces from almost any part of a planarian called stenostomum , for example , can develop into completely new worms . this makes them an excellent model organism to study regeneration in the lab . the freshwater planarian dugesia , pictured here , has been experimentally split with a scalpel from the head to the pharynx , resulting in a two - headed animal . ( image : tom adams / getty )
hwang j . s . , kobayashi c . , agata k . , ikeo k . and gojobori t . ( 2004 ) detection of apoptosis during planarian regeneration by the expression of apoptosis - related genes and tunel assay : gene . , 333 , 15 - 25
agata , k . , soejima , y . , kato k . , kobayashi c . , umesono y . , watanabe k ( 1998 ) structure of the planarian central nervous system ( cns ) revealed by neuronal cell markers : zoolog . sci . , 15 , 433 - 440
nakazawa m . , cebrià f . , mineta k . , ikeo k . , agata k . , gojobori t . ( 2003 ) search for the evolutionary origin of a brain : planarian brain characterized by microarray : mol . biol . evol . , 20 , 784 - 791
planarian adult stem cells ( pascs ) , historically referred to as neoblasts , are small ( 5–10 μm diameter ) undifferentiated cells that localize in the parenchyma , a loose tissue that lies beneath the muscle layers and surrounds the organs . although definitive proof of their pluripotency has not yet been provided , planarian neoblasts are regarded as adult pluripotent stem cells ( reviewed in shibata et al . , 2010 ) and are responsible for the remarkable regeneration ability shown by these animals ( saló and baguñà , 1984 ; rossi et al . , 2008 ) ( fig . 2a ) .
neurons in the planarian brain more closely resemble those of vertebrates than those of advanced invertebrates , exhibiting typical vertebrate features of multipolar shape , dendritic spines with synaptic boutons , a single axon , expression of vertebrate - like neural proteins , and relatively slow spontaneously generated electrical activity . 74 therefore , the planarian is not only the first animal to possess a brain , but may be the ancestor of the vertebrate brain . 61 , 75 some of the most interesting and controversial data on the persistence of memories in regeneration thus came from studies of this model . 76 , 77
the ability of organisms to regenerate missing body parts is one of the great mysteries of biology . planarians are freshwater flatworms that have been a classic regeneration model for more than a century . the regenerative abilities of planarians astound : following decapitation , a new head can be regenerated in under a week , and an entire animal can be regenerated from a body fragment approximately 1 / 300th the size of the original animal . regeneration involves formation of a tissue outgrowth at wound sites ( a blastema ) . planarian regeneration requires a population of adult pluripotent stem cells , enabling in vivo study of how stem cells can be regulated to replace aged , damaged , and missing tissues . because greater than 50 percent of examined planarian genes have counterparts throughout the animal kingdom , including in humans , genetic study of planarian regeneration stands to broadly increase our understanding of stem cell and regenerative biology .
inoue t . , kumamoto h . , okamoto k . , umesono y . , sakai m . , sánchez a . a . and agata k . ( 2004 ) morphological and functional recovery of the planarian photosensing system during head regeneration : zoolog . sci . , 21 , 275 - 283
planarians are fascinating animals best known for their ability to regenerate from even very small pieces of their bodies . a common classroom lab involves cutting planarians into an anterior and a posterior half and watching them regenerate . what some people don ' t realize is that splitting in half—voluntarily ! —is also a planarian reproductive strategy . devising experiments to learn more about this reproductive strategy is a great hands - on inquiry opportunity for students . have students design and set up experiments to determine what conditions prompt planarians to reproduce in this manner . first have them do background research on planarian care and reproduction .
nishimura k . , kitamura y . , umesono y . , takeuchi k . , takata k . , taniguchi t . , agata k . ( 2008 ) identification of glutamic acid decarboxylase gene and distribution of gabaergic nervous system in the planarian dugesia japonica : neuroscience , 153 , 1103 - 1114 .
planarians are free - living platyhelminthes that can regenerate any part of the body , including the central nervous system ( cns ) . in addition to dugesia japonica and girardia tigrina , schmidtea mediterranea is one of the most commonly used species in planarian research . this freshwater planarian is small in size ( 0 . 1–2 cm ) , has a diploid genome of about 800 mb distributed on four chromosomes , which accounts for about 30 , 000 predicted genes ( cantarel et al . , 2008 ) , and can reproduce sexually as well as asexually by fission . the regenerative abilities of planarians depend on a large population of somatic stem cells ( reviewed in handberg - thorsager et al . , 2008 ) . this feature , which , among bilaterians , is unique to planarian flatworms , means that planarians can serve as an in vivo petri dish for the study and manipulation of stem cells in their natural environment .
molecular analyses of the mechanisms by which neural networks may exchange information with surrounding tissues ( as would be required for the regenerating planarian brain to be imprinted with information by the remaining body fragment ) . such studies could test non - neural bioelectrical signaling 178 , 189 and cytoskeletal computation 190 , 191 ;
since different reproduction processes in plants , as described above , do not require passage through an embryonic step ( that defines which individual is the ‘parent’ and which is the ‘child’ ) , the relationship between the two resulting individuals is somewhat ambiguous , and bears many similarities to the relationship between two regenerated planarian fragments .
cebrià , f . , nakazawa , m . , mineta , k . , ikeo , k . , gojobori , t . , agata , k . ( 2002b ) dissecting planarian central nervous system regeneration by the expression of neural - specific genes : dev . growth differ . , 44 , 135 - 146
nishimura k . , kitamura y . , inoue t . , umesono y . , yoshimoto k . , taniguchi t . , agata k . ( 2007b ) identification and distribution of tryptophan hydroxylase ( tph ) - positive neurons in the planarian dugesia japonica : neurosci . res . , 59 , 101 - 106
the maintenance of organs and their regeneration in case of injury are crucial to the survival of all animals . high rates of tissue turnover and nearly unlimited regenerative capabilities make planarian flatworms an ideal system with which to investigate these important processes , yet little is known about the cell biology and anatomy of their organs . here we focus on the planarian excretory system , which consists of internal protonephridial tubules . we find that these assemble into complex branching patterns with a stereotyped succession of cell types along their length . organ regeneration is likely to originate from a precursor structure arising in the blastema , which undergoes extensive branching morphogenesis . in an rnai screen of signaling molecules , we identified an egf receptor ( smed - egfr - 5 ) as a crucial regulator of branching morphogenesis and maintenance . overall , our characterization of the planarian protonephridial system establishes a new paradigm for regenerative organogenesis and provides a platform for exploring its functional and evolutionary homologies with vertebrate excretory systems .
asami , m . , nakatsuka , t . , hayashi , t . , kou , k . , kagawa , h . , agata , k . ( 2002 ) cultivation and characterization of planarian neuronal cells isolated by fluorescence activated cell sorting ( facs ) : zoolog . sci . , 19 , 1257 - 1265
the source of new cells : adult pluripotent stem cells promote regeneration a cellular explanation for planarian regeneration has been sought since the late 1800s , when a population of proliferative cells ( neoblasts ) was identified . a key unanswered question has been whether planarian regeneration is explained by a cell type displaying pluripotency ( capacity to produce all cell types of the soma ) at the single - cell level or by the collective action of multiple dividing cell types that each has limited and different potential . to address this question , we developed single - cell assays and determined that certain individual cells from the neoblast population could divide to clonally generate many similar dividing cells and displayed broad differentiation potential . these cells could restore regenerative capacity to lethally irradiated hosts lacking all other cell division . we named such cells
clonogenic neoblasts
( cneoblasts ) . these experiments indicated that pluripotent stem cells persist in planarian adulthood , providing a cellular basis for the remarkable regenerative abilities of planarians .
the answer came in march 1960 when fellow worm runner jay boyd best wrote mcconnell about the cannibalistic tendencies of a particular planarian species . mcconnell and the prg ran pilot studies in april and obtained positive results . each of the next four replications — each run blind to guard against experimenter bias — also produced promising results .
the body size of planarians along the anterior - posterior axis ranges from 3 to 20 millimeters . the planarian cns is composed of a brain in the head region and a pair of ventral nerve cords ( vncs ) that extend the length of the body ( fig . 1a ) ( agata et al . , 1998 ; tazaki et al . , 1999 ) . the brain consists of two lobes , forming an inverted u - shaped structure , and nine branches on the outer side of each lobe that project to the surface of the head region , forming sensory organs ( fig . 1b ) ( okamoto et al . , 2005 ) . a pair of eyes is located on the dorsal side of the brain . the size and number of brain neurons vary depending on the size of the planarian’s body . the minimum size of the brain ( in a planarian with body size about 0 . 7mm ) consists of about 8 , 000 neurons ( okamoto et al . , unpublished ) .
ogawa k . , ishihara s . , saito y . , mineta k . , nakazawa m . , ikeo k . , gojobori t . , watanabe k . and agata k ( 2002 ) induction of a noggin - like gene by ectopic dv interaction during planarian regeneration : dev . biol . , 250 , 59 - 70
species capable of regenerating lost body parts occur throughout the animal kingdom , yet close relatives are often regeneration incompetent 1 , 2 . why in the face of ‘survival of the fittest’ some animals regenerate but others do not remains a fascinating question 3 . planarian flatworms are well known and studied for their ability to regenerate from minute tissue pieces , yet species with limited regeneration abilities have been described even amongst planarians 4 . here we report the characterization of the regeneration defect in the planarian dendrocoelum lacteum and its successful rescue . tissue fragments cut from the posterior half of the body of this species are unable to regenerate a head and ultimately die 5 . we find that this defect originates during the early stages of head specification , which require inhibition of canonical wnt signalling in other planarian species 6 , 7 , 8 . notably , rna interference ( rnai ) - mediated knockdown of dlac - β - catenin - 1 , the wnt signal transducer , restored the regeneration of fully functional heads on tail pieces , rescuing d . lacteum ’s regeneration defect . our results demonstrate the utility of comparative studies towards the reactivation of regenerative abilities in regeneration - deficient animals . furthermore , the availability of d . lacteum as a regeneration - impaired planarian model species provides a first step towards elucidating the evolutionary mechanisms that ultimately determine why some animals regenerate and others do not .
freshwater planarians are an emerging model in which to study regeneration at the molecular level . these animals can regenerate a complete central nervous system ( cns ) in only a few days . in recent years , hundreds of genes expressed in the nervous system have been identified in two popular planarian species used by several laboratories : dugesia japonica and schmidtea mediterranea . functional analyses of some of those neural genes have allowed the process of cns regeneration to begin to be elucidated in those animals . however , additional work is required to characterize the different neuronal populations . thus , the identification or generation of antibodies that act as markers for specific neuronal cell types would be extremely useful not only in obtaining a more detailed characterization of the planarian nervous system but also for the analysis of phenotypes obtained by rna interference . here , i have used five different antibodies to describe different neuronal populations in the freshwater planarian s . mediterranea . this study represents a first step in characterizing the organization of the nervous system of this species at the cellular level .
cebrià , f . , kudome , t . , nakazawa , m . , mineta , k . , ikeo , k . , gojobori , t . , agata k . ( 2002a ) the expression of neural - specific genes reveals the structural and molecular complexity of the planarian central nervous system : mech . dev . , 116 , 199 - 204
nishimura k . , kitamura y . , inoue t . , umesono y . , sano s . , yoshimoto k . , inden m . , takata k . , taniguchi t . , shimohama s . , agata k . ( 2007a ) reconstruction of dopaminergic neural network and locomotion function in planarian regenerates : dev neurobiol . , 67 , 1059 - 1078
the planarian brain contains gaba ( γ - aminobutyric acid ) synthetic neurons ( gabaergic neurons ) . gad ( glutatamic acid decarbocylase ) is the rate - limiting enzyme for gaba biosynthesis , and converts glutamic acid into gaba . recently , the planarian gad gene ( djgad ) was isolated ( nishimura et al . , 2008 ) , and it was found that in the head region , djgad - expressing cells are distributed in a dotted pattern in the brain . some of them are aligned in an inverted u - shape , while others are distributed in the medial part of the brain . the distribution pattern of djgad - immunopositive cells is very similar to that of djgad - mrna stained by in situ hybridization ( fig . 5b ) .
more than 100 years ago , early workers realized that planarians offer an excellent system for regeneration studies . another unique aspect of planarians is that they occupy an interesting phylogenetic position with respect to the nervous system in that they possess an evolutionarily primitive brain structure and can regenerate a functional brain from almost any tiny body fragment . recent molecular studies have revisited planarian regeneration and revealed key information about the cellular and molecular mechanisms underlying brain regeneration in planarians . one of our great advances was identification of a gene , nou - darake , which directs the formation of a proper extrinsic environment for pluripotent stem cells to differentiate into brain cells in the planarian dugesia japonica . our recent findings have provided mechanistic insights into stem cell biology and also evolutionary biology .
any of various small , chiefly freshwater flatworms of the class turbellaria , having soft , broad , ciliated bodies shaped like a leaf . planarians have a mouth on their lower side that is often closer to the tail than the head , and a three - branched digestive cavity . if a planarian is cut into several pieces , each piece can grow into a whole new organism .
to investigate the complexity of neural cells in planarians , a new method was developed for gene profiling of single neurons obtained using cell sorting . in this method , brain neurons are collected as single cells using facs ( asami et al . , 2002 ) . after the collection of single neurons , rna is extracted , and cdna is synthesized and amplified by pcr . each cdna sample is then used as a template for semi - quantitative pcr analysis using specific primers . the results of such analyses were overlaid on a 3d planarian brain model and a 3d model based on the single - cell pcr database of the expression of about 1 , 000 genes in the planarian brain was created on a scale of about 1 to 10 and is available on the web ( urltoken ) .
planarian flatworms are an exception among bilaterians in that they possess a large pool of adult stem cells that enables them to promptly regenerate any part of their body , including the brain . although known for two centuries for their remarkable regenerative capabilities , planarians have only recently emerged as an attractive model for studying regeneration and stem cell biology . this revival is due in part to the availability of a sequenced genome and the development of new technologies , such as rna interference and next - generation sequencing , which facilitate studies of planarian regeneration at the molecular level . here , we highlight why planarians are an exciting tool in the study of regeneration and its underlying stem cell biology in vivo , and discuss the potential promises and current limitations of this model organism for stem cell research and regenerative medicine .
planarians are considered to be among the most primitive animals which developed the central nervous system ( cns ) . to understand the origin and evolution of the cns , we have isolated a neural marker gene from a planarian , dugesia japonica , and analyzed the structure of the planarian cns by in situ hybridization . the planarian cns is located on the ventral side of the body , and composed of a mass of cephalic ganglions in the head region and a pair of ventral nerve cords ( vnc ) . cephalic ganglions cluster independently from vnc , are more dorsal than vnc , and form an inverted u - shaped brain - like structure with nine branches on each outer side . two eyes are located on the dorsal side of the 3 ( rd ) branch and visual axons form optic chiasma on the dorsal - inside region of the inverted u - shaped brain . the 6 ( th ) - 9 ( th ) branches cluster more closely and form auricles on the surface which may function as the sensory organ of taste . we found that the gross structure of the planarian cns along the anterior - posterior ( a - p ) axis is strikingly similar to the distribution pattern of the
primary
neurons of vertebrate embryos which differentiate at the neural plate stage to provide a fundamental nervous system , although the vertebrate cns is located on the dorsal side . these data suggest that the basic plan for the cns development along the a - p axis might have been acquired at an early stage of evolution before conversion of the location of the cns from the ventral to the dorsal side .
after nearly a year of mcconnell’s wrangling with referees , the paper appeared in the journal of comparative and physiological psychology . in his next experiments , mcconnell and the prg showed that each regenerated part of trained worms cut in several pieces retained the initial training and , more important , a planarian that , after several regenerations , contained none of the structure of the originally trained animal also retained the memory .
next , they tried grinding up trained worms and injecting them into naïve recipients , but that didn’t work , either . the hypodermic needles were too big — getting one inside a flatworm was like trying to impale a prune with a javelin — and if , by chance , the needle was positioned well enough to inject the planarian - puree , it either oozed out or caused the worm to explode .
uncovering the mechanisms that control size , growth , and division rates of systems reproducing through binary division means understanding basic principles of their life cycle . recent work has focused on how division rates are regulated in bacteria and yeast , but this question has not yet been addressed in more complex , multicellular organisms . we have acquired a unique large - scale data set on the growth and asexual reproduction of two freshwater planarian species , dugesia japonica and dugesia tigrina , which reproduce by transverse fission and succeeding regeneration of head and tail pieces into new planarians . we show that generation - dependent memory effects in planarian reproduction need to be taken into account to accurately capture the experimental data . to achieve this , we developed a new additive model that mixes multiple size control strategies based on planarian size , growth , and time between divisions . our model quantifies the proportions of each strategy in the mixed dynamics , revealing the ability of the two planarian species to utilize different strategies in a coordinated manner for size control . additionally , we found that head and tail offspring of both species employ different mechanisms to monitor and trigger their reproduction cycles . thus , we find a diversity of strategies not only between species but also between heads and tails within species . our additive model provides two advantages over existing 2d models that fit a multivariable splitting rate function to the data for size control : firstly , it can be fit to relatively small data sets and can thus be applied to systems where available data is limited . secondly , it enables new biological insights because it explicitly shows the contributions of different size control strategies for each offspring type .
planarian eyes are composed of two cell types : pigment cells and visual neurons ( photoreceptor cells ) . the pigment cells are arranged into a crescent - shaped eyecup , while the visual neurons are located outside of the eyecup . studies using a monoclonal antibody specific to planarian photoreceptors ( called vc - 1 ) showed that dendrites from the visual neurons are distributed inside of the pigment eyecup to form a rhabdomeric structure containing opsins , and that the axons of the visual neurons project to the medial region of the main lobes ( agata et al . , 1998 ; sakai et al . , 2000 ) . they form an optic chiasma in the dorso - medial region of the brain . each lateral branch neuron ( chemosensory neuron ) projects onto the lateral region of the brain ( inoue et al . , 2007 ) .
we recently tested the ability of gap junctional communication in somatic cell networks to implement somatic memory in planaria ( reviewed in durant et al . , 2016 ) by transiently reducing gap junctional connectivity among cells . this can be accomplished by rnai targeting 3 distinct innexin proteins ( oviedo et al . , 2010 ) , which resulted in a bipolar two - headed planarian ; posterior wounds of middle fragments grew heads instead of tails . the same result can be achieved by a transient ( 2 - day ) inhibition of gap junction communication using a blocker such as octanol ( nogi and levin , 2005 ) . the benefit of this approach is that unlike rnai , which persists in tissues for long periods of time , octanol leaves planarian tissues within 24 h ( as shown by hplc ) ( oviedo et al . , 2010 ) .
all planarians used in the present study were dugesia japonica ichikawa & kawakatsu 1964 . after examining three planarian species : dugesia japonica , dugesia dorotocephala and schmidtea mediterranea , we found dugesia japonica to be the most suitable for this project . it has remarkable regenerating capabilities , high tolerance for training and dissection procedures , and is very active . before experiments , planarian colonies were stored in rectangular plastic containers , filled with poland springs natural spring water ( oviedo et al . , 2008a ) . dugesia japonica has a high tendency to undergo spontaneously fission . in order to prevent spontaneous fission and allow worms to reach a suitable size for the experiment ( 1–1 . 5 cm ) , containers were stored in an incubator at 10°c in continuous darkness ( morita and best , 1984 ) and fed once or twice a week with organic beef liver .
takano , t . , pulvers , j . n . , inoue , t . , tarui , h . , sakamoto , h . , agata , k . , umesono , y . ( 2007 ) regeneration - dependent conditional gene knockdown ( readyknock ) in planarian : demonstration of requirement for djsnap - 25 expression in the brain for negative phototactic behavior : dev . growth differ . , 49 , 383 - 394
the planarian does not have gills or lungs , it obtains its oxygen by simple diffusion over its flat body . the dugesia cannot survive outside of the water , so biologists studying it must make sure that the specimen has plenty of water that is aerated . the dugesia does have an excretory system to remove wastes . tiny cells , called flame cells , line the lateral edge of the organism and function to remove waste .
planarian brain regeneration . the cns of the planarian d . japonica , visualized by whole - mount in situ hybridization against a pan - neural marker ( a receptor protein tyrosine phosphatase ) ( cebrià et al . , 2002c ) in intact ( a ) and regenerating ( b ) animals . planarians were decapitated ( dashed line in a ) and allowed to regenerate for the indicated time points ( as indicated in b ) . note that de novo brain regeneration is complete after less than 7 days . dashed line in b corresponds to the original amputation site marked in a . scale bar : 0 . 5 mm . panel a is adapted from mineta et al . ( mineta et al . , 2003 ) , ©2003 national academy of sciences , usa ; and panels b ( 1–3 days ) are adapted from cebrià et al . ( cebrià et al . , 2002c ) .
students may find both sexual and asexual forms of reproduction intriguing ; however , studying the asexual form of reproduction is easier . the laying of egg sacs by planarians has been observed to typically , but not always , be a seasonal phenomenon that occurs during the spring . the relative unpredictability of the egg sac laying , and the fragility of the worms during this phase , make studies of planarian sexual reproduction difficult for students in a classroom setting .
the provocative idea , which demands additional study , that certain memories in planaria survive decapitation , presents a useful opportunity for debate . we present a few hypothetical scenarios , not mutually exclusive , that will allow us to ask whether upon fission a planarian that is derived from the head fragment can consider the regenerated fragment that arises from its cut - off tail fragment as ‘my twin’ , ‘my sibling’ , ‘my child’ or ‘myself’ ( fig . 1 ) .
molecular studies showed that the brain is composed of structurally distinct and functionally diverse domains , which have been defined by morphological observations using a variety of molecular markers . in the first study on the organization of the planarian brain , a homolog of the homeobox - containing gene orthopedia ( otp ) from planaria , djotp , was isolated . djotp is specifically expressed in the branch structures of the brain ( umesono et al . , 1997 ) . in a subsequent study , two otd / otx - related homeobox genes , djotxa and djotxb , were isolated from the planarian dugesia japonica . within the cns , expression of both these genes appear to be restricted to the brain . djotxa is expressed in the medial region of the brain and in visual cells . djotxb is expressed in the major region of the brain ( called the sponge region or main lobes ) just lateral to the djotxa - positive domain , but not in the more lateral branch structures , where djotp is expressed . these expression data for djotxa , djotxb and djotp suggest a molecular basis for subdivision of the mature planarian brain into at least four regions : a djotxa - positive region , a djotxb - positive region , a djotp - positive region ( branch regions ) , and a region lateral to the branches and negative for djotp ( fig . 2 ) ( umesono et al . , 1999 ) .
therefore , are all clones created equal , or could epigenetic information survive splitting ? the answer depends on the capacity of asymmetric fission to maintain long - term variability – the ability of each cloning product ( each ‘individual’ ) to hold memories acquired by their ancestral body ( or the relevant part thereof ) in its lifetime . a few different mechanisms , which are not mutually exclusive , and could operate in tandem , could in theory establish asymmetry following planarian fission .
neurodegenerative and cardiovascular diseases , as well as stroke , infection and injury , require therapies that aim to replace lost , damaged or inoperative tissues . regenerative medicine is therefore a major focus of medical research . whereas regeneration in humans is limited , several vertebrates , such as salamanders and fish , can regenerate amputated body parts with high efficiency ( reviewed in stoick - cooper et al . , 2007 ) . the master of regeneration is , however , the planarian flatworm .
for many , these results were hard to swallow . that mcconnell first reported these results in the worm runners digest , a journal / magazine he edited that published a mixture of straight science and spoof , did not help his case . of more importance , the planarian work was not easily replicable . the beasts were difficult to train , and various experimenters — most notably a team working under the patronage of nobel laureate mac calvin at berkeley — reported their failure to do so .
one possible locus for the cellular basis of memory are the planarian neoblasts ( stem cells 114 ) , which could be modified through epigenetic changes induced by learning . 22 , 115 , 116 when the new brain develops , neoblasts could potentially imprint the cns through self - organization mechanisms . 117 - 119 a second possibility is that non - coding rnas implement inheritance . 99 , 100 regardless of the molecular mechanisms required for this process , a complete answer to this question will also require an understanding of the mapping of cognitive content to specific molecular states ( encoding and decoding of learned information within rna , protein , cell networks , or some other mechanism ) . it is clear that modern techniques and recent findings show great potential for the planarian as an animal model in learning and memory research . investigating this unique animal , which displays complex behavior and can regenerate its entire brain in only a few days , may provide answers to the enigma of acquisition , storage , and retrieval of memories .
in certain planarian species that are able to switch between asexual and sexual reproduction , determining whether a sexual has the ability to switch to the asexual state is problematic , which renders the definition of sexuals controversial . we experimentally show the existence of two sexual races , acquired and innate , in the planarian dugesia ryukyuensis . acquired sexuals used in this study were experimentally switched from asexuals . inbreeding of acquired sexuals produced both innate sexuals and asexuals , but inbreeding of innate sexuals produced innate sexuals only and no asexuals . acquired sexuals , but not innate sexuals , were forced to become asexuals by ablation and regeneration ( asexual induction ) . this suggests that acquired sexuals somehow retain asexual potential , while innate sexuals do not . we also found that acquired sexuals have the potential to develop hyperplastic and supernumerary ovaries , while innate sexuals do not . in this regard , acquired sexuals were more prolific than innate sexuals . the differences between acquired and innate sexuals will provide a structure for examining the mechanism underlying asexual and sexual reproduction in planarians .
op : many people are sadly unaware of the true extent of earth’s biodiversity . one can spend a lifetime just learning about a certain type of organism , and even a lifetime is not enough . that’s why education is essential , if only to make people aware of what is “out there . ” i got into planarian research by an indirect route , namely by using them as animal models in pharmacology . as i learnt more about planarians , i became more interested in them in general ; the rest is history .
planaria are free - living flatworms that live in quiet ponds or bodies of water . in some areas you can even catch a few planarian by attaching a piece of liver to a fish hook and a sinker and dropping it into the water . wait a few minutes and pull the liver out and you may find tiny little black worms feasting on the meat . like all flatworms , planaria belong to the kingdom animalia , and the phylum platyhelminthes . this phylum also contains parasitic flatworms , like the tapeworm and the liver fluke .
the dugesia does have a simple nervous system that includes a ganglia located in its anterior region to serve as a brain . as such , the dugesia exhibits the trait of cephalization , where the majority of its sense organs are located in the anterior region . it has a triangular head with two prominent eyespots . upon closer inspection of the eyes , you can see that they have a curious cross - eyed expression to them . the presence of the two eyes and lateral horns on the head indicate that the planarian has bilateral symmetry .
disruption of the dorsoventral axis after bmp pathway silencing . ( a ) 21 - d - old regenerating head pieces after smed - smad1 rnai . white arrowheads mark the ectopic dorsoventral margin that delimits , which seems to be a second planarian differentiated on the dorsal side like a siamese twin . yellow arrows point to the original eyes . red arrows point to ectopic eyes . ( b ) 21 - d - old regenerating trunk piece after smed - bmp rnai . white arrowheads mark the duplicated body margin . bars , 0 . 5 mm .
we thank punita koustubhan for general laboratory assistance ; junji morokuma and wendy beane for advice and help with the planarian model system ; douglas blackiston and robert cook for many helpful discussions about behavioral paradigms ; durwood marshall , dany s . adams and laura vandenberg for assistance with statistics ; douglas blackiston , michael romero and philip starks for comments on early versions of the manuscript ; and ethan golden for fabrication of the rough - textured petri dishes . this work is dedicated to paul van oye and james v . mcconnell , two pioneers of learning and memory in planarians .
the flat - worm or planarian is a very simple invertebrate , nevertheless , in 1955 thompson and mcconnell showed that planaria could be classically conditioned to avoid light by pairing a light cs with an electric shock us . it becomes clear just how simple an animal a planarian is when you discover that if one is cut in half while alive the two halves regenerate into two complete flatworms - the tail - half grows a new head and the head - half a new tail ! mcconnell ' s initial discovery about memory in flatworms was that once a flatworm had been conditioned to avoid light if you cut it in half and allow the halves to regenerate both of the resulting worms show evidence of knowing the light - shock association . mcconnell interpreted this as evidence that memory in flatworms was not localised in the head but was , rather distributed throughout the animal . in 1962 mcconnell performed an experiment which appeared to be even more dramatic demonstration of this . after training some planaria he ground them up an fed them to other planaria . these animals were quicker at learning the light - shock association than controls who were fed ground - up untrained worms .
other studies showed more complex subdivision structures in the main lobes ( cebrià 2002b ) , but these small subdomains are not well characterized . among these studies , the finding on the expression of one planarian brain factor homolog , djfoxd , should be mentioned ( koinuma et al . , 2003 ) . the expression of djfoxd is highly restricted to the mid - apex of the head , between the two lobes of the brain , where brain neurons are not present . the djfoxd - expression domain clearly separates the right and left lobes ( saito et al . , 2003 ) .