agelas conifera , also known as the brown tube sponge , is a species of sponge .

its color is brown , tan , or greyish brown with a lighter interior .

it is common in the caribbean and bahamas , and occasional in florida .

agelas conifera contains bromopyrrole alkaloids , notably sceptrin and oroidin , and levels of these feeding-deterrents increase upon predation .

agelas conifera

hans - martin braun added the german common name
brauner tubenschwamm
to
agelas conifera ( schmidt , 1870 )
.
atlanto - mediterranean agelas species ( 18 ) seems to possess only acanthostrongyles , including the uncertain agelas fascicularis , agelas flabelliformis , agelas inaequalis , and agelas rudis not redescribed by parra - velandia et al . ( 2014 ) .
hans - martin braun added the english common name
brown tube sponge
to
agelas conifera ( schmidt , 1870 )
.
several species ( 14 ) are reported only once from the type locality i . e . agelas axifera hentschel , 1911 ; agelas bispiculata vacelet , vasseur & lévi , 1976 ; agelas braekmani thomas , 1998 ( 1997 ) ; agelas carpenteri ( gray , 1867 ) ; agelas cavernosa thiele , 1903 ; agelas citrina gotera & alcolado , 1987 ; agelas dendromorpha lévi , 1993 ; agelas inaequalis pulitzer - finali , 1986 ; agelas linnaei de voogd , parra - velandia & van soest , 2008 ; agelas nakamurai hoshino , 1985 ; agelas nemoechinata hoshino , 1985 ; agelas novaecaledoniae lévi & lévi , 1983 ; agelas robusta , pulitzer - finali 1982 ; agelas semiglaber pulitzer - finali , 1996 .
kathryn hall marked the classification from
world register of marine species ( worms )
as preferred for
agelas conifera ( schmidt , 1870 )
.
bromoageliferin and dibromoageliferin , secondary metabolites from the marine sponge agelas conifera , inhibit voltage - operated , but not store - operated calcium entry in pc12 cells .
brominated pyrrole alkaloids from marine agelas sponges reduce depolarization - induced cellular calcium elevation .
effects of agelas oroides and petrosia ficiformis crude extracts on human neuroblastoma cell survival .
ageladine a an anti angiogenetic matrix metalloproteinase inhibitor from the marine sponge agelas nakamurai .
agelas nemoechinata . a skeleton architecture b spicular complement ( modified from hoshino 1985 ) .
concise synthesis of clarhamnoside , a novel glycosphingolipid isolated from the marine sponge agelas clathrodes .
total synthesis of ageladine a , an angiogenesis inhibitor from the marine sponge agelas nakamurai .
reef sponges of the genus agelas ( porifera : demospongiae ) from the greater caribbean .
some pharmacological activities of novel adenine - related compounds isolated from a marine sponge agelas mauritiana .
from anti - fouling to biofilm inhibition : new cytoitoxic secondary metabolites from two indonesian agelas sponges .
agelas sansibarica sp . n . spicular complement of verticillate acanthostyles , acanthoxeas and acanthostrongyles ( sem ) .
agelas sansibarica sp . n . spicular complement of verticillate acanthostyles , acanthoxeas and acanthostrongyles ( lm ) .
agelas cavernosa . the original illustration of verticillate acanthostyles ornate by spiny whorls by thiele ( 1903 ) .
a new agelas ( demospongiae : agelasida : agelasidae ) from the thousand islands , west–java , indonesia .
enzyme - catalyzed reactions of 3d with cell - free preparations from a . conifera ( ac ) , a . sceptrum ( as ) , and s . caribica ( sc ) . [ a ]
agelas bispiculata . spicular complement of acanthostyles of two size categories ( modified from vacelet et al . 1976 ) .
glycolipids from sponges . part 17 . 1 clathrosides and isoclathrosides , unique glycolipids from the caribbean sponge agelas clathrodes .
description of two new species in the genus agelas ( demospongiae ) from zamami island , the ryukyus , japan .
debromodispacamides b and d : isolation from the marine sponge agelas mauritiana and stereoselective synthesis using a biomimetic proline route .
agelas novaecaledoniae . a type specimen b spicular complement with two spicular types ( modified from lévi and lévi 1983 ) .
a study on the mechanism of action of sceptrin , an antimicrobial agent isolated from the south pacific sponge agelas mauritiana .
representative pais from sponges agelas spp . and stylissa , and unnatural chlorinated analogs ( 3d , e , 4d ) .
agelas sansibarica sp . n . type specimen ( alcohol preserved , colour different from in vivo ) from the zanzibar archipelago .
agelas marmarica . a – b spicular complement ( a modified from vacelet and vasseur 1965 b modified from lévi 1958 ) .
agelas carpenteri . drawing of the reticulate network with spongin fibres echinated by verticillate spicules perpendicularly arranged ( modified from carpenter 1856 ) .
agelas nakamurai . a skeleton architecture b close up of spicules insertion in the spongin fibres c acanthostyles ( modified from hoshino 1985 ) .
growth dynamics and bioactivity variation of the mediterranean demosponges agelas oroides ( agelasida , agelasidae ) and petrosia ficiformis ( haplosclerida , petrosiidae ) .
agelas with unique spicular complement composed of three spicular categories , oxeas , styles and strongyles with spines arranged in a variable number of verticilles .
a secondary metabolite , 4 , 5 - dibromopyrrole - 2 - carboxylic acid , from marine sponges of the genus agelas alters cellular calcium signals .
agelorins a and b , and 11 - epifistularin - 3 , three new antibacterial fistularin - 3 derivatives from the tropical marine sponge agelas oroides .
agelas semiglabra . spicular complement with two dimensional categories of acanthostyles ; long acanthostyles spiny only at the tips ( modified from pulitzer - finali 1996 ) .
genus agelas . biogeographic pattern ( grey areas ) . the red dot indicates the type locality of the new species agelas sansibarica sp . n . at jambiani ( 06°18 ' 44 . 8
s , 39°33 ' 32
e ) , eastern coast of unguja island , zanzibar archipelago , united republic of tanzania .
agelas robusta . a type specimen ( dry ) b spicular complement of acanthostyles very stout , verticillate by blunt spines ( modified from pulitzer - finali 1982 ) .
agelas mauritiana . a drawing of a massive specimen b skeleton fragment c – g spicular complement b–d agelas mauritiana var . oxeata a modified from van soest 1989 ; b – d modified from thomas 1979 c modified from carter 1883 e modified from vacelet and vasseur 1965 f modified from lévi 1964 g modified from lévi 1961 ) .
( of chalinopsis conifera schmidt , 1870 ) schmidt , o . ( 1870 ) . grundzüge einer spongien - fauna des atlantischen gebietes . ( wilhelm engelmann : leipzig ) : iii - iv , 1 - 88 , pls i - vi . page ( s ) : 60 ; pl v fig 2b [ details ]
these colonies appear identical to agelas conifera , and have a similar growth form , whereby chains of tubes may form antler - like growths . however , there are two main differences . firstly , their colour is more pale being cream to reddish brown in colour . secondly , their outer surface is pitted with small but deep depressions , most of which are inhabited ( possibly etched by ) by a zoanthid . the two forms are likely to be the same species ( s . zea ) although they are clearly distinguishable .
agelas braekmani . a schematic drawings of two specimens b spicular complement of verticillate acanthostyles c skeleton architecture with echinate fibres , sponge surface on the right ( modified from thomas 1998 ) .
the indo - pacific species of agelas number 18 , including the new species here described . the most widespread species is agelas mauritiana ( including its oxeata variety ) recorded in the australian western pacific , and the indian ocean from the mascarenes archipelago ( type locality ) , seychelles archipelago , madagascar , and mozambique channel to the southern red sea and east to sri lanka .
agelas gracilis . a ramose slim dry specimen b – c spicular complement of verticillate acanthostyles of different dimensional categories ( a–b modified from lévi and lévi 1983 c modified from whitelegge 1897 ) .
the widespread genus agelas , including until now 35 valid species , was established by duchassaing and michelotti ( 1864 : 76 ) describing the type species agelas dispar from the caribbean sea . agelas oroides is the only mediterranean species , and is endemic . the western atlantic ( gulf of mexico , caribbean , and brazil ) hosts 17 species . the majority of the latter ( 13 ) were recently revised while the remaining four species were considered dubious or suggested as synonyms ( van soest 2002 , muricy et al . 2011 , parra - velandia et al . 2014 ) .
agelas linnaei . a type series specimens ( liquid preserved ) b a living shallow water specimen c spongin skeleton with spicules d verticillate acanthostyles ( modified from de voogd et al . 2008 ) .
the new species is characterized by the co - presence of three categories of spicules never recorded in other agelas species . acanthostrongyles are abundant , ca . 20–30 % of the total number of spicules .
[ a ] [ 3d ] = 20 mm in 1 : 4 ch 3 cn–0 . 1m sodium phosphate buffer , 0 . 2 mg / ml total protein ( bradford assay ) of cell - free enzyme preparation ( cfp ) from either s . caribica ( sc ) , a . conifera ( ac ) , or a . sceptrum ( as ) ( for preparation , see supporting information ) .
summarizing spicular complements and spicular morphotraits of 36 agelas species : i ) 32 species show only acanthostyles from atlantic ( 17 ) , mediterranean ( 1 ) , and the majority ( 14 ) of the indo - pacific areas ; ii ) three indo - pacific species show acanthostyles and acanthoxeas ; iii ) only one species agelas sansibarica sp . n . from the western indian ocean show a spicular component composed of acanthostyles , acanthoxeas , and acanthostrongyles .
the present paper aims to report the discovery of a new species of agelas from the zanzibar archipelago comparing it to all species belonging to the genus . to support global sharing of information on faunistics and taxonomy of porifera from not widely accessible data sources an updated overview on the morphology and geographic distribution of agelas species from the indo - pacific area is also provided together with a brief description and exhaustive iconography , as well as a dichotomous key to indo - pacific species .
the new species agelas sansibarica is characterized by the unique morphotrait of three categories of megascleres , i . e . acanthostyles , acanthoxeas , and acanthostrongyles with spines arranged in verticilles regularly scattered along the entire spicule . no other agelas species exhibit this spicular combination . acanthostrongyles , well identifiable and abundant , represent an exclusive diagnostic trait of the new species . the functional role of acanthostrongyles is doubled since echinanting spicules arm both the fibres surface and the core of the axial part of fibres .
agelas axifera . a living specimen b skeleton fragment with two spicular types , axially embedded in a fibre and arming the surface c acanthostyles d acanthoxea ( a modified from an original underwater shot by j . hooper b–d modified from hentschel 1911 ) .
manconi r , pronzato r , perino e ( 2016 ) a new species of agelas from the zanzibar archipelago , western indian ocean ( porifera , demospongiae ) . zookeys 553 : 1–31 . doi : 10 . 3897 / zookeys . 553 . 5999
( of chalinopsis conifera schmidt , 1870 ) van soest , r . w . m . ( 2002 ) . family agelasidae verrill , 1907 . pp . 819 - 823 . in : hooper , j . n . a . & van soest , r . w . m . ( eds ) systema porifera . a guide to the classification of sponges . 1 ( kluwer academic / plenum publishers : new york , boston , dordrecht , london , moscow ) . [ details ]
agelas dendromorpha . a the sponge specimens of the type series b spicular complement of two spicular types , acanthostyles and acanthoxeas ; small oxea - like spicules ( bottom , right ) are not reported in the original description ( modified from lévi 1993 ) .
the sponge fauna of the zanzibar archipelago is poorly studied and data are reported almost exclusively in very old papers ( lendenfeld 1897 , baer 1906 , jenkin 1908 , sollas 1908 , thomas 1976 ) . in none of these papers species belonging to the genus agelas duchassaing & michelotti , 1864 ( porifera : demospongiae : agelasida : agelasidae ) are reported . the presence of agelas mauritiana ( carter , 1883 ) along the zanzibar coasts was recently recorded ( said et al . 2010 ) as producer of bioactive compounds .
agelas sansibarica sp . n . a skeletal network of spongin fibres echinated by spicules ( sem ) b detail of fibres surface echinated by verticillate spicules ( sem ) c section of a primary fibre cored by a verticillate acanthostrongyle d–e skeletal network ( lm ) .
( of chalinopsis conifera schmidt , 1870 ) van soest , r . w . m . ( 2002 ) . family agelasidae verrill , 1907 . pp . 819 - 823 . in : hooper , j . n . a . & van soest , r . w . m . ( eds ) systema porifera . a guide to the classification of sponges . 1 ( kluwer academic / plenum publishers : new york , boston , dordrecht , london , moscow ) . [ details ] available for editors [ request ]
agelas ceylonica . a very low quality image of the specimen studied by dendy 1921 b schematic drawing of a branched specimen by van soest 1989 c skeleton architecture with echinate fibres d–e spicular complement of verticillate acanthostyles ( c modified from thomas 1981 d modified from dendy 1921 e modified from lévi 1961 ) .
activated defense mechanisms have been widely recognized in terrestrial plants [ 21 , 28 ] and to a lesser extent in marine algae [ 23 , 29 , 30 ] . however , examples of activated defense in marine sessile invertebrates have been very limited , with two examples from the verongid sponges aplysina spp . [ 31 , 32 ] and aplysinella sp . [ 33 ] and the hydroid species tridentata marginata [ 34 ] . despite these examples , the existence of activated defense in sponges has been discussed very controversially ( see [ 31 , 35 ] ) . similar patterns have been described with induced defenses . defense induction is widely known in terrestrial plants [ 21 ] and marine macroalgae [ 18 , 19 ] , but studies on on marine invertebrates are scarce . while the sponge chondrilla nucula did not induce defense [ 36 ] , the sponge agelas conifera increased concentrations of feeding deterrent compounds after simulated predation [ 37 ] .
to discriminate between all 36 agelas species by diverging diagnostic morphotraits is notably difficult , as highlighted in the previous section . morphotraits of the genus are extremely conservative and different species appear very similar . focusing on the indo - pacific species our attempt was not as completely successful as is also the case for the atlantic species by parra - velandia et al . ( 2014 ) .
the enzyme - catalyzed dimerization of dichloroclathrodin ( 3d ) is specifically linked to pai - producing sponges . cell - free enzyme preparations of several pai - producing agelas sponges all converted 3d to 4d / 7d , while incubation of 3d similarly prepared extracts of five co - occurring sponges that do not produce pais failed to generate 4d / 7d or oxidize 3d at all ( table s1 ) .
notes : browhish / pinkish / cinnamon orange , laterally fused tubes , running on branches or growing on one another , and usually arising from a single base , forming antlers or clubs . often with darker zoanthids livion on the skin . may be confused with agelas tubulata lehnert & van soest , 1996 , also pictured here , in which the tubes usually arise from the base close to the substratum . spicules are acanthostyles .
several findings from the seychelles archipelago ( thomas 1973 ) and kenya ( pulitzer - finali 1993 ) . the revisitation of the 11 agelas specimens slides of the pulitzer - finali collection from east africa highlighted the presence of only styles in the spicular complement with notable variability of thickness , length , and spinosity . this confirms his opinion : ‘it would be inappropriate at the moment to try to identify some of them with established species and to propose new species . ’ also in this case the original material is not available after damaging of types during the recent genova flood in 2014 ( october ) .
description ( modified from pulitzer - finali 1996 ) . growth form encrusting , very small . skeleton architecture not reported . megascleres of single category and two size classes . acanthostyles type i verticillate ( 230–375 × 11–16 μm ) , spiny only towards the tips . acanthostyles type ii ( 75–100 × 3 . 5 μm ) verticillate , entirely spiny . habitat . shallow water . geographic distribution . pacific ocean . recorded from bismarck sea , known only from papua new guinea ( type locality ) . remarks . the specific epithet ending with – er is masculine despite the gender agelas is feminine , as a consequence the ending must be changed into – ra . because of the overlap in spicule dimension de voogd et al . ( 2008 ) report that is not possible to distinguish different size categories .
growth form massive , thick , rounded , 6–10 cm in diameter . colour in life purple to orange and light brown . consistency firm and elastic . surface rough to the touch , finely hispid , finely conulose for tips of ascending fibres supporting the dermal membrane , with regularly scattered circular and convoluted depressions ( 0 . 5 cm in diameter ) very similar to those of agelas cerebrum . oscules few , small , irregularly scattered . choanosomal skeleton as an irregularly reticulate network of spongin fibres . primary fibres 50–110 ( 71 . 67 ±17 . 63 ) μm in diameter , strongly echinate by single , scattered spicules to groups of diverging spicules ; ascending primary fibres cored by spicules also present . secondary fibres 20–50 ( 35 ± 9 ) μm in diameter notably echinate and cored by spicules . tertiary network not observed .
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citation : rohde s , nietzer s , schupp pj ( 2015 ) prevalence and mechanisms of dynamic chemical defenses in tropical sponges . plos one 10 ( 7 ) : e0132236 . urltoken
copyright : © 2015 rohde et al . this is an open access article distributed under the terms of the creative commons attribution license , which permits unrestricted use , distribution , and reproduction in any medium , provided the original author and source are credited
data availability : all relevant data are within the paper and its supporting information files .
funding : this work was supported by the german academic exchange service to sr and the national institutes of health mbrs score grant s06 - gm - 44796 to pjs . the funders had no role in study design , data collection and analysis , decision to publish , or preparation of the manuscript .
sponges and other sessile invertebrates are lacking behavioural escape or defense mechanisms and rely therefore on morphological or chemical defenses . already in the 1950s it was discovered that sponges yield a wide array of biologically active secondary metabolites [ 1 ] . since then more than 5300 chemical compounds have been described in sponges [ 2 ] . marine natural products research has been driven mainly by pharmacological screening programs , which aim at the discovery of new chemical structures with pharmacological activity , neglecting the ecological functions of these compounds . studies in the field of marine chemical ecology focus on chemically mediated ecological interactions and revealed a pronounced bioactivity of many sponge compounds , e . g . defense against predation , fouling or pathogen attack [ 3 – 6 ] .
while past studies in chemical ecology have treated sponges mainly as whole organisms neglecting their ability to house high numbers of microbial symbionts ( up to 40 % of the sponge biomass [ 7 ] ) , recent studies are more and more trying to evaluate the role of microbial symbionts in the production of biologically active secondary metabolites . so far , only a few studies have identified the actual producers of secondary metabolites of interest , implicating either the sponge itself [ 8 , 9 ] , or the associated bacteria [ 10 – 12 ] . regardless of the actual producer of bioactive secondary metabolites , the sponge itself , or the associated microorganisms , sponge holobionts ( sponge plus the associated microorganisms ) often defend themselves against predation by producing feeding - deterrent compounds ( e . g . [ 3 , 13 , 14 ] ) .
constitutive defense , should be favoured when the sessile organisms ( e . g . sponges ) live under constant predation pressure and / or predators are dominated by highly motile macropredators ( e . g . fish ) . given the example of sponges , macropredators are capable to consume large amounts of sponge biomass in short time periods and are fast moving animals that do not spend much time at one prey individual . an induction of chemical defensive compounds could include high rates of biomass loss during the induction period .
activated defense , can be regarded as specialised form of a constitutive defense . precursors of bioactive compounds are produced , stored and following wounding , converted to potent defensive products [ 23 ] . the conversion is fast ( e . g . seconds ) and often enzyme catalysed . by converting inactive or less active precursors to highly active defense metabolites only upon tissue damage and locally restricted to the wounded tissue , the risk of autotoxicity by the conversion products can be alleviated .
induced defense , is defined as the ‘de novo’ production of defensive compounds activated by predator attack . induction of defense includes that defensive compounds are only produced on demand , thereby saving resources and increasing the prey’s chemical variability [ 18 , 21 , 24 , 25 ] . a disadvantage of induced defenses is however , that the induction process requires several days to weeks during which the sponge is undefended and could suffer from high biomass loss . induced defense is therefore regarded as favourable under variable grazing conditions and / or the dominance of mesopredators like small crustaceans or gastropods that feed at slow rates and biomass loss within the induction period is tolerable [ 18 , 24 ] .
defensive strategies should have evolved in response to the dominant regional predation patterns . consequently , in regions with constant predation pressure and a dominance of macropredators like fish ( e . g . coral reefs ) , sponges should display constitutive or activated defenses [ 26 ] . in the marine environment , research on activated chemical defenses is just beginning . so far , most activated defenses have been discovered in algae , while very few examples of this strategy have been described in sessile marine invertebrates [ 27 ] . however , having reviewed defensive strategies in sponges , thoms & schupp ( 2007 ) hypothesized that activated defenses may have been overlooked in the past due to traditional and restricted methodological approaches by marine chemical ecologists and that “various factors could possibly have led to underreporting of activated chemical defenses in the past , bolstering constitutive defense as the status quo in sponge chemical defense . ”
in contrast , in regions where sponges experience variable predation pressure and mesopredators like crustaceans or sea urchins are the major consumers ( e . g . temperate rocky reefs ) , inducible defenses are discussed as favored defensive strategy , since the slow grazing rates of the regional predators allows to tolerate the low biomass loss within the induction period [ 18 , 24 , 26 ] .
tropical and temperate benthic systems differ with regard to dominant consumption regimes . while in tropical regions fishes are the dominant predators on reefs , temperate systems are predominantly characterised by a mesopredator community of crustaceans , sea urchins or gastropods [ 26 ] . in guam , which is surrounded by fringing coral reefs , the major sponge consumers are fish . due to the tropical conditions , where seasonal changes in water temperature and light intensities are almost lacking , the variability in grazer density is low . these prerequisites should favour activated or constitutive defense .
antimicrobial activity is a very common feature of sponge extracts [ 38 , 39 ] . however , induced antimicrobial activity has not been found in sponges , and activated antimicrobial activity was demonstrated in only one sponge species [ 31 ] .
from terrestrial studies we know that induced defenses can impact both consumers and pathogens [ 40 ] , and are in fact even caused by microbial pathogens [ 41 ] . this has also been shown in a freshwater macrophyte , where induced antifeeding defense was accompanied by an induction of antimicrobial defense [ 42 ] .
the effects of predator feeding versus invasion by microbial pathogens via grazing scars on the induction process is unclear [ 42 ] . induced responses could be due to feeding or to pathogens that infect the prey via wounds made by predators [ 41 , 43 ] . thus , predation may not only harm prey organisms directly , but could also increase the risk of pathogen infection . microbial attacks are especially likely in aquatic systems , where microbial densities are much higher ( 10 4 - 10 7 cells ml - 1 ) than atmospheric densities [ 44 ] .
this study tried to evaluate chemical defense mechanisms in eight different sponge species . experiments were run under controlled conditions to exclude multiple factors in the field that increase chemical variability [ 45 ] . specifically , we tested for presence of constitutive defenses , induced and activated defenses by examining the feeding deterrence and antimicrobial activity of sponge extracts .
the results of this study will provide extensive insight in the prevalence of induced and activated chemical defense mechanisms of sponges and identify whether induced or activated responses also suppress co - occurring microbes that might function as pathogens .
two experiments were carried out with the sponge species . the first experiment was designed to test for defense induction , the second to test for defense activation . after both experiments , feeding assays with two spongivorous species were conducted .
bacteria from the natural environment were isolated to identify differences in antimicrobial activity among sponge extracts . bacterial strains were isolated from hydrolithon reinboldii , a crustose coralline alga ( cca ) . those cca form an abundant reef substrate on which many sessile organisms settle . cca were collected in luminao , which is located outside of apra harbor , guam , usa ( 13°27 ' 53 . 57
n , 144°38 ' 54 . 81
e ) . we inoculated different media swabs from the cca shortly after the algae were collected . the media were incubated at 27°c and strains picked based on their morphology and color to establish a broad range of environmental bacterial isolates . picked colonies were transferred at least three times to obtain pure isolates . in order to identify the isolates , dna of each strain was extracted and dna was purified using the qiaquick pcr purification kit ( qiagen , gaithersburg , md ) . pcr products were sequenced by macrogen inc . high - quality sequences ( defined as > 600 bp ) were compared to the national center for biotechnology information ( ncbi ) database ( urltoken ) by using blast .
to preserve the isolates , cryo cultures were established for every pure strain . we chose 38 strains over a wide phylogenetic range and included all isolated strains with known pathogenic activities ( mostly pseudoalteromonas spp . and vibrio spp . ) in our assays . the selected strains were used in disc diffusion assays to identify bacterial growth inhibition of sponge extracts .
general deterrence was tested by feeding assays with extracts of untreated sponges . all tested sponge species were chemically defended against predation compared to solvent controls ( wilcoxon , p < 0 . 05 ) , except for h . altus , that showed no antipredatory defenses ( wilcoxon , p = 0 . 35 , figs 1 and 2 ) . the feeding assays with the pufferfish and the urchins produced highly congruent results .
food pellets contained organic extracts at natural volumetric concentrations ( white bars ) or solvent only ( black bars ) . p - values indicate the result of the pair wise analysis ( wilcoxon ' s signed rank test ) .
comparisons of the deterrence of induced sponges by simulated predation with non - induced sponges revealed that inducible defense was apparent only in the sponges s . massa and m . sarasinorum ( figs 3 and 4 ) . while the induced defense of s . massa was effective on both the pufferfish and the urchins , the induced defense of m . sarasinorum was only effective in the pufferfish assays . the species aplysinella sp . , cacospongia sp . , d . granulosa , and iotrochota sp . showed no difference in palatability in response to induction ( wilcoxon , p > 0 . 05 ) . n . carbonaria was even preferred by the pufferfish when it was induced compared to non - induced extracts ( wilcoxon , p = 0 . 02 ) , but this effect was absent in the urchin assay .
food pellets contained organic extracts of induced specimen ( hatched bars ) or non - induced specimen ( black bars ) . p - values indicate the result of the pair wise analysis ( wilcoxon ' s signed rank test ) .
defense activation was indicated in the sponge m . sarasinorum . the pufferfish preferred non - activated extracts compared to activated ones ( fig 5 ; wilcoxon , p = 0 . 05 ) . this preference was not supported in the urchin assay , which could be due to the fact that the feeding rates of the urchins in this assay were very low ( fig 6 ) . aplysinella sp . , cacospongia sp . , d . granulosa , h . altus , iotrochota sp . , s . massa , and n . carbonaria revealed no activated defense mechanisms . activated extracts of cacospongia sp . and iotrochota sp . were even preferred by the pufferfish ( wilcoxon , p < 0 . 01 ) , but not by the urchins .
food pellets contained organic extracts of activated specimen ( dotted bars ) or intact specimen ( black bars ) . p - values indicate the result of the pair wise analysis ( wilcoxon ' s signed rank test ) .
food pellets contained organic extracts of activated specimen ( dotted bars ) or non - activated specimen ( black bars ) . p - values indicate the result of the pair wise analysis ( wilcoxon ' s signed rank test ) .
disc diffusion assays investigated the antimicrobial activity of sponge extracts ( fig 7 ) . comparisons between sponge species showed very variable antimicrobial effects . h . altus and iotrochota sp . showed very low antimicrobial activity , m . sarasinorum and aplysinella sp . medium and d . granulosa , s . massa and n . carbonaria rather strong antimicrobial activity . induction treatment increased microbial inhibition significantly in four of the eight tested sponge species ( fig 8 ) , with aplysinella sp . , cacospongia sp . , m . sarasinorum , and s . massa yielding higher antimicrobial activity ( wilcoxon , p < 0 . 01 ) . n . carbonaria showed a similar trend ( wilcoxon , p = 0 . 07 ) , while d . granulosa , h . altus and iotrochota sp . showed no difference between induced and non - induced state . activation treatment increased microbial inhibition in d . granulosa and h . altus significantly ( wilcoxon , p = 0 . 04 , p = 0 . 02 , resp . ) , decreased antimicrobial activity in s . massa and n . carbonaria ( wilcoxon , p = 0 . 01 , p = 0 . 02 , resp . ) and did not change in aplysinella sp . , cacospongia sp . , iotrochota sp . , and m . sarasinorum ( fig 9 , wilcoxon , p > 0 . 05 ) .
difference in microbial inhibition between induced and non - induced sponge extracts in disc diffusion assays .
positive values reflect higher inhibition in induced extracts , negative values reflect higher inhibition in non - induced extracts . p - values indicate the result of the pair wise analysis ( wilcoxon ' s signed rank test ) .
difference in microbial inhibition between activated and non - activated sponge extracts in disc diffusion assays .
positive values reflect higher inhibition in induced extracts ; negative values reflect higher inhibition in non - induced extracts . p - values indicate the result of the pair wise analysis ( wilcoxon ' s signed rank test ) .
until the 1990s , marine ecologists commonly assumed that predation had little effects on sponge populations , since very few predators had been observed to feed on sponges [ 51 , 52 ] . later on , studies conducted in the caribbean established that low predation rates were mainly a result of sponge chemical defenses [ 14 ] , a fact that was also supported by other studies from the pacific , mediterranean , red sea and antarctica [ 53 – 55 ] . in our study , 87 % of the tested species were chemically defended , which is comparable to the results of the studies cited above and confirms the importance of chemical defenses to persist in predator rich environments such as tropical coral reefs .
m . sarasinorum was the other sponge that demonstrated induced defense . numerous secondary metabolites have previously been isolated from m . sarasinorum for pharmacological research ( e . g . [ 68 , 69 ] ) , but nothing is known about the compound’s ecological functions . however , m . sarasinorum is chemically defended , since its crude extract deterred feeding of pufferfish and a natural reef fish community [ 49 ] . the deterrent effect was also observed in this study , and furthermore , simulated predation increased the deterrent effect in the urchin assay . it is known that defensive compounds may not be active against all predator species , which could explain the species - specific predator response to induced defenses in this study [ 25 , 70 ] . apparently , the sea urchins responded with more sensitivity than the pufferfish to the induced changes in m . sarasinorum ’s chemistry .
reducing investments in defense mechanisms ( e . g . secondary metabolite production ) should increase metabolic resources for other processes like reproduction . reproductive parameters were not analyzed in this study . however , sponges that are highly defended against predation appear to have a lower reproductive output compared to less defended species [ 17 ] , indicating the costs of defenses and the potential advantage of inducible defenses .
nearly all sponge species tested were feeding deterrent ( except h . altus ) , preventing fish feeding and therefore natural induction by spongivorous fishes in aquarium experiments . as a consequence , clipping was used as defense inducing treatment . several studies on macroalgae used clipping as a method to simulate herbivory ( e . g . [ 25 , 70 , 74 ] ) . however , earlier reviews have already cautioned that clipping does not simulate herbivory adequately and it should not be assumed to do so without proper testing [ 75 , 76 ] . prey organisms may rely on specific chemical cues to ensure that defenses are only induced when predation risk is high [ 43 ] . it is possible that the simulated predation in our study lacked specific chemical cues , therefore not triggering defense induction in the tested species .
m . sarasinorum was the only species that revealed activated antipredatory defense mechanisms . the effect was only detectable in the pufferfish assay ; the urchins did not distinguish between activated and non - activated extracts . one reason that an activated defense mechanism was not detected in the urchin assays can be the low feeding rates of the urchins , which could have masked any differences in this particular assay . activated defense was not tested in aplysinella sp . since it had been described in this species in detail before [ 33 ] .
while cost saving is a clear advantage for induced defense systems , the advantages of activated defenses are less obvious . in activated defense systems , biologically active compounds are stored in different compartments . during wounding and disruption of compartmentalization by predators , the biologically less active compounds are converted to potent compounds . therefore the organisms can avoid or reduce autotoxicity , as they only store less active compounds for bioconversion [ 59 ] . the high number of constitutive defenses in this and other studies suggests that sponges deal well with potential autotoxic effects of defensive compounds . further studies on the autotoxic effects of precursor and converted defensive compounds could reveal whether constitutive defenses are more common due to ecological or physiological reasons .
sponges are known to produce more than 5000 secondary metabolites [ 77 ] and it is recognized that many species have elaborate chemical defenses to deter possible predators and also to inhibit the colonization , growth , or pathogenicity of harmful microbes [ 78 ] . in the present study , 75 % of all tested sponge species demonstrated antimicrobial activity .
interestingly , 50 % of the tested sponge species demonstrated induced antimicrobial defense . simulated predation increased the antimicrobial activity of aplysinella sp . , cacospongia sp . , m . sarasinorum , and s . massa . with increased wounding intensity , the risk of pathogen infection via feeding scars rises , while it can also lead to increased antimicrobial defenses through induced or activated defense mechanisms . these results can have consequences for future ecological and pharmaceutical studies on antimicrobial compounds from sponges . we demonstrated that wounding frequently can alter antimicrobial chemistry in sponges , which needs to be addressed in the handling of sponges and the design of ecological experiments . pharmaceutical studies that are interested in the extraction and isolation of bioactive compounds could increase amounts of antimicrobial compounds by inducing compound production prior to collection and extraction .
in conclusion , we could demonstrate that both induced and activated antipredatory defenses are present in tropical sponges . however , constitutive defense appears to outweigh induced or activated mechanisms in tropical sponges . future studies should reveal if ecological factors like predator community composition or variability in predation intensity are the driving force in that pattern , or whether physiological constraints limit facultative defenses in sponges . furthermore , we could show that the production of antimicrobial compounds was also increased by induced and activated defenses in many sponge species . to identify the underlying signaling pathways for these responses could be a rewarding task for future studies and give more insights in the immune systems of marine invertebrates .
we would like to thank uog marine laboratory staff and students for their assistance during the experiments . sr was supported by the german academic exchange service ( daad ) .
conceived and designed the experiments : sr pjs . performed the experiments : sr sn . analyzed the data : sr . contributed reagents / materials / analysis tools : sr pjs . wrote the paper : sr sn pjs .
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