bluuebunny/crossref_metadata_2025 huggingface dataset:
Localization of Carbonic Anhydrase in the Plumula of the Tooth of Lytechinus variegatus (Echinodermata: Echinoidea)
Authors: Chen Chang‐Po , Lawrence John M.
Published: April 2010

Labeled inhibitor autoradiography showed that carbonic anhydrase (CA) occurs in (1) the epithelium, (2) free odontoblasts and fibroblasts, (3) row odontoblasts and their membranes surrounding the calcareous parts and (4) extracellular areas. Extracellular CA occurs in areas where fibroblasts and collagen fibers are abundant. The localization of CA suggests that CA facilitates the movement of CO2 through the membrane and/or extracellular spaces to promote calcification.
The Ultrastructure of the Plumula of the Tooth of Lytechinus variegatus (Echinodermata: Echinoidea)
Authors: Chen Chang‐Po , Lawrence John M.
Published: April 2010

The plumula is enclosed by a single layer of epithelial cells. There are two types of odontoblasts: syncytial and free odontoblasts. Syncytial odontoblasts are arranged linearly on the abaxial side and have a highly active Golgi complex, rough endoplasmic reticulum, large and round mitochondria, and small coated vesicles indicative of a high level of secretory activity. Free odontoblasts cluster on the adaxial side and have patchy chromatin and little cytoplasm. The free odontoblasts migrate to the abaxial side, where their structure changes to that of syncytial odontoblasts. Calcareous deposits are formed intracellularly by syncytial odontoblasts within two membranes: an outer plasma membrane and an inner vacuolar membrane. The vacuolar membrane has organic particles on the surface of the membrane. There is no trace of organic matter within the calcareous deposit. Fibroblasts are located on the adaxial side. Collagen fibers are located primarily on the adaxial side adjacent to the calcareous depositing membranes and between free odontoblasts, but they are not located in the deposits. Collagen fibers may play a role in cell migration and thus in calcification. The morphological changes of the plumulae are closely related to calcification.
The Ultrastructure of the Gastrodermal Gland Cells in the Freshwater Planarian Dugesia gonocephala s.l.
Authors: Garcia‐Corrales Pedro , Gamo Jacinto
Published: April 2010

Light and transmission electron microscopy have been used to study the gastrodermal gland cells of the triclad Dugesia gonocephala s.l. The events involved in the ultrastructural transformation and the secretion process in these cells were followed at four different stages in both fasted and fed animals. During the feeding stage their secretory granules are directly discharged into the intestinal lumen by means of a secretion process of the holocrine type that is described in this paper. It is suggested that such secretions contribute to extracellular digestion and that disintegration of the gland cells is accompanied by a differentiation of neoblasts into new gland cells, reflecting a turnover of gland cells during the triclad digestive stages.
Ultrastructural Aspects of the Endolymphatic Organ in the Frog Rana esculenta
Authors: Marmo Francesco , Balsamo Giuseppe , Crispino Paola
Published: April 2010

Morphological evidence indicates that the endolymphatic sac of anuran amphibians is involved in the morphogenesis of most statoconia (aragonite crystals). The cells frequently show the aspect of an intense secretory activity, their cytoplasm being totally occupied by a number of vesicles the contents of which might be expelled into the lumen forming the organic—or at times mineral—components of statoconia. Moreover, evidence is presented that another function of the endolymphatic sac might be involvement in a resorptive mechanism for endolymph and for CaCO3 mobilization from aragonite crystals. In fact, these show clear signs of erosion, consistent with a role as a labile calcium deposit played by the calcareous formations of the endolymphatic sac.
Fine Structure of the Fat Body and its Bacteroids in Blattella germanica (Blattodea)
Authors: De Piceis Polver Paola , Sacchi Luciano , Grigolo Aldo , Laudani Ugo
Published: April 2010

The abdominal fat body of the cockroach Blattella germanica contains three characteristic cell types—trophocytes, bacteriocytes and urate cells—which have been investigated by electron microscopy. The trophocytes are rich in lipid droplets of different sizes; glycogen, rough endoplasmic reticulum and mitochondria are also abundant. In females immediately after eclosion, the trophocytes contain a greater number of lipid droplets, some of which have different electron density; glycogen and cytoplasmic organelles are clearly reduced. The bacteriocytes hold rod‐like and spherical bacteroids, which are encapsulated by a vacuolar membrane; they show a thin cytoplasmic membrane and an evident cell wall surrounded by a membrane‐like outer envelope. The bacteroids appear to be dividing either by transverse partition or by budding. The urate cells, adjacent to the bacteriocytes, are characterized by complex urate vacuoles delimited by a double layer‐structure.
Fine Structural Observations on the Extracellular Matrix (ECM) of Xenoturbella bocki Westblad, 1949
Authors: Pedersen Knud Jørgen , Pedersen Lars Ryde
Published: April 2010

Fine structural observations on the extracellular matrix (ECM) and connective tissue system of the enigmatic vermiform animal Xenoturbella bocki have demonstrated a complex and interesting organization of the ECM. Most conspicuous is the subepidermal membrane complex (SMC), and the major part of the ECM is present in this structure, which consists of a limiting basal lamina on each side of a central thick filamentous layer, probably of a collagenous nature. Distinct anchoring filaments are found as part of the SMC. A basal lamina is also observed in connection with the gastrodermal cells. The mesoderm is represented by a loose, ill‐defined parenchyma, without filaments. The SMC is discussed in relation to subepidermal basal matrices occurring in turbellarians and enteropneusts, the two groups to which a relationship to Xenoturbella previously has been suggested. Comparisons between the ECM in Xenoturbella and in turbellarians do not support the notion of a relationship between these groups. Conversely, the present study strengthens previous indications of distinct similarities between certain characteristics of the epidermis and the SMC present in both enteropneusts and in Xenoturbella.
Fine Structure of Spermatozoa in Perkinsiana rubra and Pseudopotamilla reniformis (Sabellidae: Polychaeta)
Authors: Chughtai Iffat
Published: April 2010

The Perkinsiana acrosome is elongated, pointed and tapering, strengthened anteriorly by cortical rings of longitudinally running units. The Pseudopotamilla acrosome is cap‐like and its apical region contains a laminar body with two electron densities, the laminae crossed by occasional lines of dislocation, as in a crystal. These apparently solid regions are closely followed by peripherally situated lucent zones. The zone in Pseudopotamilla contains tubules, which are very like those in Sabella sperm, except that they lack connections with the acrosome base. Both species are probably broadcast spawners and have nuclei, mitochondria, centrioles and flagella of the primitive type. This may, however, be a secondary reversion through neoteny.
A Scanning Electron Microscope Study on the Internal Structure of the Peritreme of the Female Mite Varroa jacobsoni (Oudemans, 1904)
Authors: Liu T. P.
Published: April 2010

The peritreme of the adult female mite Varroa jacobsoni is located laterally above coxa III and is enclosed within a peritrematal shield which has a slit at the end. The peritrematal shield is cuticular in nature. The peritreme is lined with a thick inner membrane which has numerous tooth‐like projections. The outer membrane of the peritreme is thin and smooth. In between these two membranes is a layer of columnar cells. The internal structure of the peritreme in relation to the female mite's ability to adjust to different atmospheric conditions is discussed.
Phagocytic Cells in the Peripheral Blood of the Dogfish Scyliorhinus canicula L. II. In Vivo Studies
Authors: Parish N. , Wrathmell A. , Hart S. , Harris J. E.
Published: April 2010

In vivo phagocytosis by peripheral blood leucocytes of the dogfish Scyliorhinus canicula L. was examined by monitoring the fate of a variety of injected materials, both particulate and soluble, in normal and immunised fish. Carbon, yeasts and bacteria were phagocytosed by monocytes, thrombocytes and type 1 granulocytes (neutrophils). Quantitative in vivo antigen clearance studies employed five species of bacteria, yeast and KLH. After an initial significant decrease of these antigens in the circulation, low numbers of viable bacteria and yeasts and low concentrations of KLH persisted for long periods after injection. Previous exposure to several of these antigens had little or no effect.
A Motorneurone Cell Body Located Either Dorsally or Ventrally within a Crustacean Abdominal Ganglion
Authors: Maitland D. P. , Heitler W. J.
Published: April 2010

In the last abdominal ganglion of the squat lobster Galathea strigosa (Decapoda, Anomura) a unique pair of flexor motorneurones exist whose medial cell bodies occur paired either on the ventral or the dorsal surface of the ganglion or else are located separately, one dorsal and the other ventral. In 60 squat lobsters (30 ♂ 30 ♀), this pair of medial dorsal/ventral (MDV) cell bodies was found in 4 distinct cell pair configurations: ventral/ventral, 24; dorsal/dorsal, 5; right ventral/left dorsal, 14; right dorsal/left ventral, 17. MDV cell bodies were never found lying midway between the dorsal and ventral surfaces. The distribution of configurations was approximately the same for both sides of the ganglion and for both sexes, and whether a cell occurred ventrally or dorsally was found to be independent of the position of its partner. The determination of cell body location appears not to be influenced by any cell‐cell interaction, despite an apparent ‘point of close association’ between the two soma neurites and a strong bias overall towards the ventral location (dorsal 1/3, ventral 2/3).
The Ultrastructure of the Protonephridium of the Actinotroch Larva (Phoronida)
Authors: Hay‐Schmidt Anders
Published: April 2010

The actinotroch larva of Phoronis muelleri has a pair of protonephridia located beneath the tentacle ring and draining the blastocoel; each protonephridium is composed of about 25 solenocytes and a nephroduct which opens in a nephropore on the ventral side of the metasome. The neck of the solenocytes consists of bars, mutually interconnected by a fenestration lamina. Inside the neck microvilli originate proximally in the proximal intrachoanal field and extend through the neck into the nephroduct. There is no canal cell. In cross section the nephroduct is composed of 5–7 monociliary cells, with the cilium protruding through a border of microvilli and extending into the nephroduct. The whole protonephridium is surrounded by a basal lamina. Comparisons of the actinotroch protonephridium with those of other groups have not revealed any convincing homologies. The protonephridia of the protostomians are all considered to be of ectodermal origin, while the cyrtopodocytes of Branchiostoma are mesodermal. The protonephridium of the actinotroch is ectodermal.
Differential Effect of Sodium and Magnesium on the Pituitary of Goldfish Adapted to Calcium‐Free Environments
Authors: Olivereau Madeleine , Olivereau Jean‐Michel , Lambert Jean‐François
Published: April 2010

Adaptation to deionized water (DW) affects several cell types in the goldfish. The pars intermedia PAS‐positive cells are highly stimulated. Their low response or the absence of changes in goldfish kept in 1/3 Ca‐free seawater (SW) and in Ca‐free SW‐adapted eels, respectively, suggest that sodium and/or magnesium are interfering. To test this hypothesis, young goldfish were adapted to DW supplemented or not with sodium (50 and 140 mM) for 8 and 16 days or with magnesium (16.5 and 50 mM) for 16 and 30 days. Cytological and morphometric studies of the pituitary showed that prolactin (PRL) cell activity was reduced by sodium. Thyrotropic (TSH) cells were stimulated. The activity of melanocyte‐stimulating (MSH) cells increased in DW + Na+. Stimulation of the pars intermedia PAS+ cells in DW was partly inhibited by adding sodium; the cellular and nuclear areas increased only moderately, the endoplasmic reticulum (ER) was not conspicuous and mitotic activity disappeared.

In DW + Mg2+ the activity of PRL, TSH and MSH cells tended to be lower after a long‐term adaptation. The response of the PAS+ cells was as high as that noted in DW; complete degranulation, enlargement of the ER and important mitotic activity. Differential responses to Na+ and Mg2+ are not due to pH differences in the solutions.

External sodium is able then to reduce the response of the PAS+ cells in a Ca‐free environment, while magnesium is not inhibitory. Other cell types are also affected by high levels of Na+ and Mg2+.
Tunicate Endostyles: Histochemistry of Acidic Glycoproteins Re‐examined in Ciona intestinalis and Styela plicata
Authors: Hohenleitner Frank J. , Caso Louis V.
Published: April 2010

Previous reports of tunicate endostyles have suggested that they contain little or no acidic glycoproteins in the glandular zones. The endostyles of Ciona intestinalis and Styela plicata were examined after anhydrous fixation with cyanuric chloride. Polyanions were stained with alcian blue (AB) at pH 2.5 or azure A, while sulfomucins were stained with high‐iron diamine (HID) or AB at pH 1.0. Endostyles were also tested for sensitivity to acid hydrolysis (AH) and saponification. In Ciona zones 2 and 4 sometimes demonstrated positive HID and AB 1.0 responses. Almost invariably zone 6 was AB+ at pH 2.5; zones 2 and 4 were frequently responsive to AB, but less intense. Each of these 3 zones, when AB+, was sensitive to AH. Responses by zones 3 and 5 to AB (pH 2.5), azure A and saponification suggest that these zones contain mostly nuclear material. In secretory zones 2, 4 and 6 histological responses are consistent with the histochemistry of sialomucins. Zones 1 and 8 had sulfated material in the apical edges in both animal groups. Among the fixatives used for Ciona, only anhydrous fixation demonstrated most of the positive responses to polyanion‐sensitive stains.
Estrogens in Plasma of the Hagfish, Myxine glutinosa (Cyclostomata)
Authors: Schützinger S. , Choi H.S. , Patzner R.A. , Adam H.
Published: April 2010

Concentrations of estrogens in the plasma of Myxine glutinosa were measured in an attempt to determine whether different stages of reproduction are connected with certain levels of steroid concentration. After extraction with diethylether and column chromatography on Sephadex LH‐20, the plasma was radioimmunoassayed for estrogens. Samples were subdivided into 9 groups according to the gonadal conditions of the animals. There appears to be a positive correlation in females between plasma estrogen concentration and egg size (taken as an indication of reproductive stage). After ovulation the level of plasma estrogens fell appreciably. Estrogen levels of most of the samples from male animals were also determined.
Ultrastructure of Adult Gonads and Development and Structure of the Larva of Rhabdopleura normani (Hemichordata: Pterobranchia)
Authors: Lester Susan M.
Published: April 2010

Sexually mature adults, embryos and larvae of the pterobranch Rhabdopleura normani from Bermuda were studied with light and electron microscopy. The sexes are separate among the zooids of a colony, but a given colony may contain females and males. In zooids of either sex the single gonad is associated with a large haemal sinus in the trunk sac and is displaced laterally (to the right or to the left). The wall of the gonad is composed of three layers: an outer metasomal peritoneum, an internal lining of germinal epithelium and an intervening genital haemal sinus. The mature gametes lie in the lumen within the gonad. The spermatozoon is characterized by an elongate nucleus, no obvious acrosome, a long mitochondrial filament in a midpiece appendix and a single flagellum with a 9+2 axoneme. Females brood 200 μm eggs and embryos in their distinctive, basally coiled tubes. The yolky eggs undergo radial cleavage and develop into ciliated, lecithotrophic, oblong larvae (400 μm in length) that are characterized by: (1) yellow coloration peppered with black pigment spots; (2) a deep ventral depression; (3) a posterior adhesive organ; (4) an anterior apical sensory organ; (5) an evenly ciliated epitdermis. The ventral depression is not invaginating endoderm, but is instead a glandular epithelium that evidently secretes the larval cocoon and the adult tube. Internally, the peritoneum of the coelomic cavities begins to split from the periphery of a large, central mass of yolky mesenchyme cells. The larva swims using cilia, but also undergoes contractions, evidently powered by the peritoneal cells, which constitute a myoepithelium. The discussion considers pterobranch affinities with other deuterostomes and with lophophorates.
Ultrastructure of Cytotoxic Cells in Frogs
Authors: Smith C. T. , Ghoneum M. , Cooper E. L.
Published: April 2010

Our previous work gave evidence that leopard frogs (Rana pipiens) possess inducible killer (IK) cells (CTL‐like) and spontaneous killer (SK) cells (NK‐like) that can destroy allogeneic RBC. To further characterize these cytotoxic cells we have examined their ultrastructural morphology and effector cell‐target cell membrane contacts. We also studied the sensitivity of these two effector cells to low temperature (4°C). Our results showed that SK effector cells are lymphocytes (10 μm) which contain numerous vacuoles and osmiophilic granules, while IK effectors are another lymphocyte population (up to 12 μm) with a small amount of cytoplasm and few mitochondria. Both IK‐ and SK‐mediated lytic responses were suppressed significantly by low temperature. These observations allow us to propose that frog SK and IK cells may be homologous to mammalian NK and CTL.
Ultrastructural Study of Haemocytes of the Freshwater Snail Planorbarius corneus (L.) (Gastropoda, Pulmonata)
Authors: Ottaviani Enzo , Franchini Antonella
Published: April 2010

Ultrastructural studies were performed on the blood cells of Planorbarius corneus. Spreading and round cell forms were observed. The spreading form can be distinguished from the round form by its abundant cytoplasm, pseudopods and irregularly shaped nucleus. Electron dense granules in the mitochondrial matrix are found in the round form and are lacking in the spreading form. Moreover, cellular apoptosis is observed in the round form. The ultrastructural findings and the previously described characteristics support the idea that the two cell forms belong to two basic cell types.
In vitro Excystation of Metacercariae of Clinostomum complanatum (Rudolphi, 1819) (Digenea: Clinostomatidae)
Authors: Kalantan A. M. N. , Arfin M.
Published: April 2010

In vitro excystation of metacercariae of Clinostomum complanatum (Rudolphi, 1819) was studied. Excystation was an active process, initiated by a rise in temperature. The metacercariae excysted in enzymic as well as non enzymic medium, but the rate of excystation was affected by the temperature and/or pH of the medium. The optimal excystation was obtained in pepsin‐Tyrode at pH 2.3‐3.5 and a temperature of 42°C. Trypsin treatment was not required.
Autoradiographic Investigations on Cell Proliferation in the Digestive Mucosa of Fishes
Authors: Kiss Robert , de Launoit Yvan , Lenglet Georges , Danguy Andre
Published: April 2010

The labelling index (TLI) of the digestive mucosa of some fish species was determined following a pulse labelling with tritiated thymidine ([3H]TdR) and light microscopic autoradiography. In the oesophageal epithelium, proliferation was observed to occur in non mucus‐secreting cells. In the intestine, both undifferentiated and absorptive cells incorporated [3H)TdR within 1 h after injection. Statistically significant differences in [3H]TdR incorporation were observed between the upper intestine region and both the middle and lower parts on the one hand, and between the middle and lower parts on the other hand. Mucus‐secreting cells seemed unable to proliferate. In the stomach, significantly fewer labelled nuclei were counted; they were located in the isthmus epithelium. No significant difference was observed between the TLI of these regions in the different species.
Cypris Ultrastructure, Metamorphosis and Sex in Seven Families of Parasitic Barnacles (Crustacea: Cirripedia: Rhizocephala)
Authors: Glenner H. , Høeg J. T. , Klysner A. , Larsen B. Brodin
Published: April 2010

Cypris morphology in the Rhizocephala differs both between the sexes of individual species and between the species. The large aesthetasc on the third antennular segment is unique to male cyprids of the Lernaeodiscidae, Peltogasteridae and Sacculinidae (suborder Kentrogonida) and Mycetomorpha vancouverensis (suborder Akentrogonida). A fourth segmental aesthetasc, common to both sexes, is much longer in males than in females. A spinous process on the attachment disc is another male‐specific character, but is absent altogether in the Lernaeodiscidae.

It is argued that these aesthetascs help locate the settlement targets.

Except in Mycetomorpha vancourverensis, aesthetascs have been secondarily lost in cyprids of the suborder Akentrogonida, and there are no other morphological means for separating the male and female settling stage. In cyprids of Sylon hippolytes (Sylonidae) and of Mycetomorpha vancouverensis and Thompsonia sp. (Akentrogonidae) the long and slender antennules are probably used in penetration without formation of a kentrogon, as already reported for Clistosaccus paguri (Clistosaccidae). Cyprids of Sylon hippolytes and Clistosaccus paguri are almost morphologically identical.
Cirral Structure of the Pedunculated Marine Barnacle Lepas anatifera L. (Crustacea, Cirripedia) — I. Ultrastructure of the Neuromuscular Apparatus
Authors: Pfeiffer C. J. , Lowe K. J.
Published: April 2010

Lepas anatifera L. is a common pedunculated marine barnacle with well developed, articulated cirri which gather water‐suspended food particles, aid in predatory food capturing and may facilitate respiratory function by creating water currents through the mantle. The present data are the first ultrastructural findings of the neuromuscular apparatus which supports rhythmic cirral contraction.

A single large striated flexor muscle extending the length of the cirus contains mostly one type of myofibril (Type A) but is accompanied by a small band of more compact myofibrils (Type B). A well developed T‐tubular system with extensive sarcoplasmic cisternae and dyads is found, in addition to subsarcolemmal membranous whorls. A central neural complex innervates this muscle and electron‐lucent axons containing large membranous elements and small vesicles and surrounded by supporting cells with extensive rough endoplasmic reticula are present. Intimate association of nerve processes with the flexor muscle consists of neuromuscular junctions with synaptic‐type vesicles, and a well developed mode of sarcolemmal vesicular transport. These focally compacted vesicles communicate directly with the muscle tubular system. Rhythmic movement of cirri is probably controlled by alternating contraction of the flexor muscle followed by relaxation with pulsatile filling of the afferent hemocoel with blood.
Monoaminergic Systems in the Hypothalamus of the Acanthopterygian Chelon labrosus (Risso, 1826), with Special Reference to the Organon Vasculosum Hypothalami
Authors: Gómez‐Segade Pablo , Anadón Ramón , Gómez‐Segade Luis
Published: April 2010

Distribution of biogenic amines in the diencephalon of the advanced teleost Chelon labrosus was investigated by formaldehyde‐induced fluorescence. We have found three closely interrelated bright yellow‐green fluorescent monoaminergic cell groups having numerous cerebrospinal fluid‐contacting cells with dendritic processes that protrude into the lumen of the third ventricle. The most rostral of them, the organon vasculosum hypothalami, located dorsally at the mid and caudal hypothalamus level, showed under electron microscopy some monoaminergic cells and others with an abundant smooth endoplasmic reticulum. The cerebrospinal fluid‐contacting processes of both cell types, in association with numerous fibres, terminal buttons and some capillaries, constitute a thick and complex intraventricular mat. The other two fluorescent regions, nucleus recessi lateralis and nucleus recessi posterioris, border the lateral and posterior recesses of the hypothalamus.

The ultrastructural characteristics of the organon vasculosum hypothalami and its intraventricular mat suggest a function in the regulation of chemical changes in the cerebrospinal fluid. These monoaminergic regions probably represent three cell masses originated from a single region in primitive fish.
The Ulrastructure of the Gill of the Lugworm Arenicola marina (L.) (Annelida, Polychaeta)
Authors: Jouin Claude , Toulmond André
Published: April 2010

Arenicola marina gills are hollow, branched, body outgrowths with a central coelomic cavity and afferent and efferent vessels. The gill surface area per unit body weight is about 4 cm2/g wet weight. The blood vascular system anatomy differs from the tip to the base of the gill. In the distal branches of the gill the superficial afferent and efferent vessels are joined by connecting vessels. All vessels arise as spacings between the basal laminae of the thin epidermis and of the coelomic myoepithelium. The contractile part of this epithelium mainly borders the afferent and efferent vessels, whereas pedicel‐like cytoplasmic processes extend from the cell bodies and mainly line the connecting vessels. In the proximal branches of the gill the afferent and efferent vessels located in the coelomic cavity are surrounded by the coelomic myoepithelium, and a peripheral blood plexus is present below the epidermis. The gill epidermis is everywhere thin and does not exhibit the characters of a transporting epithelium. The gill coelomic myoepithelium has several functions: (i) periodic contractions of the gill, propelling blood and coelomic fluid toward the central vascular and coelomic compartments; (ii) blood ultrafilration toward the coelomic cavity; (iii) probably transport, suggested by the specialized structures of the lateral membranes of the cells.
Duplex Retina in the Mesopelagic Deep‐Sea Teleost Lestidiops affinis (Ege, 1930)
Authors: Munk Ole
Published: April 2010

The eye of the deep‐sea teleost Lestidiops affinis has been examined primarily by light microscopy and found to possess a duplex retina consisting of two main divisions, a pure‐cone and a pure‐rod region, with a narrow zone of transition, possessing both cones and rods, joining the two. The pure‐cone region is located in the temporal (caudal) part of the retina subserving binocular vision in the rostral direction. It has an area temporalis retinae with particularly long and densely packed single cones arranged in a regular hexagonal mosaic. Joined (double or twin) cones have not been recognized with certainty in the pure‐cone region. The pure‐rod region, comprising the larger part of the retina, contains rods grouped in bundles separated by retinal pigment epithelium (RPE) processes with pigmented cores. The synaptic endings of the rods are arranged in separate clusters in the outer plexiform layer, there being apparently a separate rod pedicle cluster beneath (vitread to) each rod bundle. Structural comparisons with certain other deep‐sea teleosts suggest the likely presence of a retinal tapetum in L. affinis, i.e. each single cone or rod bundle is situated in a reflecting pit formed by the RPE, with a discrete reflector apposed to the tip of each cone outer segment and the tips of the outer segments of each square‐cut rod bundle.
The Structure of a Sessile, Stalkless Crinoid (Holopus rangii)
Authors: Grimmer John C. , Holland Nicholas D.
Published: April 2010

Specimens of Holopus rangii (order Cyrtocrinida) were collected by submersible at depths of several hundred meters in the Caribbean and fixed for light and electron microscopy. The presence of an anus is confirmed. However, the chambered organ and glandular axial organ peculiar to crinoids are lacking. The gut lumen sometimes includes partially digested prey items up to several hundred micrometers in diameter, and we propose that Holopus may feed raptorially by rapidly closing its arms over demersal zooplankton. Electron microscopy of the arm reveals a radial nerve and a radial haemal channel, which light microscopy previously failed to demonstrate. The cuticle includes bacteria that are probably symbiotic. The ten brachial nerves of the aboral nervous system unite pairwise to form five calyx nerves. The calyx nerves, one in each radial position, are connected by a pentagonal, interradial commissure and then continue to the attached end of the body where they end blindly without forming an aboral nerve center. The absence of the aboral nerve center and related internal organs strengthens the argument that no basal ossicles are included in the skeleton of the calyx and suggests that Holopus may have evolved from stalked cyrtocrinid ancestors by saltatory loss of major body parts.
The Eyes of Mesostoma ehrenbergi (Focke, 1836) (Platyhelminthes, Rhabdocoela). Fine Structure and Photoreceptor Membrane Turnover
Authors: Bedini Celina , Lanfranchi Alberto
Published: April 2010

Abstract Each pigment‐cup eye of Mesostoma ehrenbergi consists of two photoreceptor cells, the anterior cell being bilobate. the posterior almost linear, and of a multicellular pigment cup. The nuclei of the photoreceptor cells are located inside the medial region of the brain. Thin cytoplasmic photoreceptor projections provided with neurosecretory‐like granules are interposed between the inner surface of the eye cup and the distal extremity of the microvilli.

The breakdown and renewal of microvillar membranes was analysed. Membrane turnover is a continuous process. At dusk and during the night abscission of photoreceptive membranes occurs. At dawn the membrane fragments are degraded to granular material, which is then endocytosed into the submicrovillar cytoplasm as coated vesicles. These vesicles form multivesicular bodies. The degradation of multivesicular body content occurs during the following light hours. The dark period is correlated with membrane synthesis for elongation of reticular membranes, which are converted into ellipsoid bodies. The formation of new microvillar membranes occurs at the base of the microvillar border, and involves the fusion with the old microvillar membranes of small vesicles detached from the tubular endoplasmic membranes and from the flattened concentric cisternae of ellipsoid bodies. The correlations with daily cycles of other invertebrates are discussed.
The Ultrastructural Characteristics of the Pheromone Gland Cells of Dendrolimus pini (Insecta: Lepidoptera)
Authors: Hallberg Eric , Reschke Maria
Published: April 2010

Abstract In the females of Dendrolimus pini the pheromone‐producing epithelium is present ventrally between the 8th and 9th abdominal segments. The epithelium is about 40 μm thick. The cells possess extensive microvillar borders, both apically towards the cuticle and laterally, towards the adjoining cells. In the spaces between the cells in the upper half of the epithelium there are loosely arranged cuticular lamellae adjacent to the microvillous borders. The epithelial cells have large, basally situated nuclei, whereas the apical parts have extensive arrangements of tightly packed and orderly arranged smooth endoplasmic reticulum. Clear vesicles and microbod–ies are present in the cytoplasm. The gland has a structural potential for high pheromone‐producing capacity (the well‐developed endoplasmic reticulum) as well as an effective emission apparatus (the microvillous borders/cuticular lamellae). These two elements could facilitate a pulsed pheromone emission that is effective in arousing the sensory system of males.
The Development of the Brachiopod Crania (Neocrania) anomala (O. F. Müller)and its Phylogenetic Significance
Authors: Nielsen Claus
Published: April 2010

The freely spawned eggs of Crania go through radial cleavage, embolic gastrulation, and the posteroventral part of the archenteron forms mesoderm through modified enterocoely. The blastopore closes in the posterior end of the larva. The ciliated, lecithotrophic larva has four pairs of coelomic pouches and three pairs of dorsal setal bundles. At metamorphosis, the larva curls ventrally by contraction of a pair of midventral muscles, which are extensions of the first pair of coelomic sacs; the larva attaches by the epithelium just behind the closed blastopore. The brachial valve is secreted by the middle part of the dorsal epithelium and the pedicle valve is secreted by the attachment epithelium. The second pair of coelomic sacs develop small attachment areas at the edge of the dorsal valve and become the lophophore coelom (mesocoel); the third pair of coelomic sacs become the body coelom (metacoel) with the adductor muscles. The posterior position of the closing blastopore is characteristic of deuterostomes. The ventral curving of the settling larva and the formation of both valves from dorsal epithelial areas indicate that the brachiopods have a very short ventral side as opposed to the phoronids. It is concluded that both groups have originated from a creeping ancestor with a straight gut.
Ultrastructural Study of Spermatogenesis in Gamasid Mites (Acari, Gamasida)
Authors: Witaliński W. , Dallai R.
Published: April 2010

Structural alterations accompanying the development of germ cells in representatives of two families of gamasid mites: Pergamasidae (Pergumasus barbarus. P. truatellus) and Parasitidae (Porrhostaspis lunulata) were examined by scanning electron microscopy. Spermatogenesis occurs in cysts containing two (P. lunuluta) or four spermatogonia (P. barbarus and P. truatellus) prior to meiosis. later arranged in a tetrahedral pattern. Meiosis produces 8 and 16 spermatids per cyst, respectively. Spermatids are located radially and elongate synchronously. Dimples appear at their acrosomal ends, soon replaced by peg‐like structures surrounded by superficial ridges. The number of ridges which correspond to longitudinal ribbons can vary between and within species as well as between spermatids occupying one cyst. Our observations suggest some unknown mechanism which allows the spermatozoa to enter vasa deferentia in a unidirectional orientation.
Fine Structure of the Tentacles of Phoronis australis Haswell (Phoronida, Lophophorata)
Authors: Pardos F. , Roldán C. , Benito J. , Emig C. C.
Published: April 2010

The epidermis of the tentacles of Phoronis australis consists of six cell types: supporting cells, choanocyte‐like sensory cells, both types monociliated, secretory A‐cells with a mucous secretion, and three kinds of B‐cells with mucoprotein secretions. On cross‐sections of the tentacle, one can distinguish four faces: the frontal one, heavily ciliated and located between the two frontolateral rows of sensory cells, the lateral and the abfrontal ones. The orientation of the basal structures of the cilia is related to the direction of their beat. The basiepidermal nervous system is grouped mainly at the frontal and abfrontal faces. The basement membrane is thickest on the frontal face and consists of circular collagen fibrils near the epidermis and longitudinal ones near the peritoneum. All peritoneal cells surrounding the mesocoel are provided with smooth longitudinal myofibrils, and isolated axons are situated between these cells and the basement membrane. The wall of the single blood capillary in each tentacle consists of epitheliomuscular cells with circular myofilaments, lying on a thin internal basal lamina; there is no endothelium.
Invited Review: Structure and Composition of Basement Membranes and Other Basal Matrix Systems in Selected Invertebrates
Authors: Pedersen Knud Jørgen
Published: April 2010

Abstract Problems concerning terminology and relationships of basement membranes to extracellular matrices (ECMs) and connective tissue systems in invertebrates are discussed, and recommendations regarding nomenclature are presented. It is suggested to use ‘basal matrix’ as a comprehensive term for various basal ECM structures, and apply the term ‘basement membrane’ (BM) for a unique ECM structure that is fully resolved only by electron microscopy and as a general and descriptive word in both light microscopy, biochemistry and electron microscopy. When possible and relevant it is recommended to apply the subdivisions: ‘lamina lucida’, ‘lamina densa’ (= ‘basal lamina’) and ‘lamina fibroreticularis’ (sometimes missing). A brief and non‐technical account of the recent concepts of BM macromolecules and their assembly is given, based on mammalian models. Basement membranes probably first appeared in cnidarians, and from then on became obligatory ECM structures. It is emphasized that this event was crucial for evolution of the multicellular state, and for construction and morphogenesis of tissues and organs. Lower worms, such as turbellarians and nemertines, display the most varied and complex basal matrices. First, in annelids, complete correlation between BM structure and composition has been demonstrated, with isolation and consecutive localization of basement‐specific molecules such as, for example, collagen IV and laminin. Both in arthropods, especially insects, and echinoderms, the introduction of modern techniques corresponding to those used in mammalian BM research has now given equally valid results. An interesting and fundamental outcome of the reviewed work on invertebrate BMs is the realization of the early evolution of BM components. Macromolecules such as laminin, collagen IV and fibronectin are highly conserved, but with fine modulations, and in lower invertebrates they may exist without being assembled into true BM structures. Laminin and fibronectin are expressed with certainty in cnidarians, and fibronectin possibly already in sponges.
Ultrastructure of Spermatozoa and Spermatids in Bonellia viridis and Hamingia arctica (Echiura) With Some Phylogenetic Considerations
Authors: Franzén Åke , Ferraguti Marco
Published: April 2010

Spermatozoa of the echiurans Bonellia viridis and Hamingia arctica show a similar ultrastructure. They are of a modified type. The head consists of a roughly cylindrical nucleus, which has a cover of electron‐dense material. The acrosome is very large and consists of an acrosomal vesicle and a rod‐shaped perforatorium or acrosomal rod. In close association with the nucleus, one or two mitochondria are found forming an irregular ring around the posterior tip of the nucleus and the centriolar apparatus. There are two centrioles, the proximal one with the conventional triplet microtubular structure. The tail flagellum is about 50 μm long and has the 9+2 axonemal structure. The oblique attachment of the acrosome to the anterior part of the nucleus gives the spermatozoon a bilateral symmetry. However, in the nuclear morphology, the arrangement of electron‐dense material around the nucleus, in the mitochondria, and in the attachment of the tail flagellum, the spermatozoon shows asymmetric organization. The sperm structure in bonelliids is unique but its genesis and the morphology of the mitochondrial midpiece support the theory that the echiurans are related to the annelids. The main results of the study are summarized in Fig. 11.
Ultrastructure of the Spermatozoa and Spermatophores of the Zuwai Crab, Chionoecetes opilio (Majidae, Brachyura)
Authors: Chiba A. , Kon T. , Honma Y.
Published: April 2010

The fine structure of the spermatozoa and spermatophores of the zuwai crab, Chionoecetes opilio, was examined electron microscopically. The spermatophores embedded in the secretory droplets within the vasa deferentia showed a spherical structure with an extremely wrinkled envelope and contained numerous spermatozoa. The mature spermatozoa of this crab, similar to those of other brachyurans, were stellate in shape and had a globular acrosome surrounded by a cup‐like nucleus with several radiating processes. The acrosome was ultrastructurally complex and its apical part was characterized by an electron‐dense discoid structure, whereas its innermost part was occupied by an electron‐lucent cylindrical structure containing assemblies of thin tubules and a reticular formation of electron‐dense material. The cytoplasm interposed between the nucleus and acrosome was remarkably reduced in volume and displayed a membranous lamellar complex, few mitochondria, and a centriole. The nuclear chromatin was not condensed but represented by finely flocculent material. The morphological aspects of the zuwai crab spermatozoa are discussed in comparison with those of other decapod crustaceans.
The Oldest Arthropods and the Origin of the Crustacea
Authors: Bergström Jan
Published: April 2010

In the last decade new finds in the Cambrian of well‐preserved faunas have given us a wealth of new material. This has meant a virtual explosion in our knowledge of the earliest arthropods, although only a fraction of the material has as yet been described. Most significantly, perhaps, the valuable descriptions of the Orsten material have shed some light on the origination of crustaceans through the sequential acquisition of crustacean characters in a group of ‘stemgroup crustaceans’ and even more basic forms. An attempt is made to outline an evolutionary tree leading on one side to trilobitomorphs and chelicerates, on the other to crustaceans and related forms. It involves numbers of synapomorphies added successively, and it appears unlikely that true crustaceans were present already in the earliest Cambrian.
Computerized Analysis of Crustacean Relationships
Authors: Wilson George D. F.
Published: April 2010

The strengths and weaknesses of phylogenetic analysis using computers are reviewed from the viewpoint of understanding crustacean evolution. Computerized methods require the explicit presentation of characters and character state homologies. New techniques allow investigators to design evolutionary models into a character data matrix, or to use evolutionary models that make minimal a priori assumptions. The computer analysis relieves the investigator from the highly repetitious testing of trees, allows the concentration on the character state data, and provides objective methods for comparing trees, primarily their length. These are regarded as the strengths of computerized methods. The weaknesses of these methods include the relatively inscrutable nature of the character data matrix compared with the overall ‘gestalt’ of resulting trees, the difficulties of defining discrete homologies within the Crustacea, especially for counts of segmentation, the lack of clear intermediate character states in some multistate segmental characters, and the inability to define evolutionary polarity. These difficulties may be overcome by analysing the data using the minimal assumption models of character evolution, and by a recognition that the trees are a result of the input data, and therefore the data should be criticized, rather than the trees themselves. A ‘consensus’ character data set, including most extant major groups of the Crustacea as well as several key fossils, was assembled and revised by the participants in the workshop. An artificial taxon, ‘ur‐crustacean characters’, was introduced to root the tree. Three observations may be made from parsimony analyses using several weighting and tree rooting methods. (1) The currently accepted large scale phylogeny and classification of the Crustacea is not corroborated. (2) The number of supposed plesiomorphic traits possessed by a taxon is not a good index for early derivation in crustacean evolution. (3) The taxon Maxillopoda is not supported by the arrangement of any of the trees.
Development of the Snout of the Australian Lungfish Neoceratodus forsteri (Krefft, 1870), with Special Reference to Cranial Nerves
Authors: Bartsch Peter
Published: April 2010

Abstract The anatomy and embryology of the dipnoan snout and olfactory organ play a major role in the discussion about the phylogenetic position of Dipnoi and the question of ancestry of Tetrapoda. This is primarily due to the fact that an internal nostril is regarded as an important preadaptive organ of the ancestors of tetrapods. Two conflicting scenarios of phylogenetic change were proposed in favour of different hypotheses of relationship. One emphasizes the similarities between Dipnoi and Chondrichthyes concerning this complex of characters. The other supports the idea of a close relationship of Dipnoi and Tetrapoda and a common origin of a ‘choana’ from the posterior external nostril of fishes. Accordingly, there is need for a detailed embryological and anatomical study which could help to clarify homologies and the basis of character evaluation. This, in the first place, concentrates on Neoceratodus forsteri. A plate reconstruction of the larval head provides many new insights which are important for comparison with the lepidosirenid lungfishes Protopterus and Lepidosiren and with other vertebrate taxa. The value of the peripheral nervous system as a topographical reference is critically reviewed. The results support the hypothesis that lungfish form a ‘primitive’ teleostomate group, closely adjoining Chondrichthyes in many characteristics of the snout formation. The relations between cranial nerves in the snout and the developing nasal sac, however, do not support the conclusion that the recent selachian condition is the exceptional ancestral character state of the lungfish snout. Dipnoi lack a ‘choana’, but nevertheless a closer relationship to tetrapods is not excluded. A vestigial and transitory naso‐buccal connection in larvae of Neoceratodus might indicate such common ancestry, but has a completely different functional significance among fishes. It is shared with several plagiostomes and is, therefore, probably not useful as a synapomorphy of Dipnoi and Tetrapoda.
Differentiation of B‐cells in the Hepatopancreas of the Prawn Penaeus monodon
Authors: Vogt Günter
Published: April 2010

Abstract The genealogy of B‐cells in the hepatopancreas of decapod crustaceans is still a matter of intense debate. According to widely accepted two‐cell‐line concepts, B‐cells are supposed to originate either from secretory F‐cells or absorptive R‐cells. These concepts are based on the putative lack of B‐cells in the differentiation zone of the hepatopancreas tubules. In the giant tiger prawn Penaeus monodon I could clearly identify differentiating B‐cells in that zone by using an ultrastructural distinguishing mark, the apical complex, that is much more sensitive than markers used before. Tracking of this feature from mature B‐cells through the differentiation zone up to the embryonic E‐cells revealed that B‐cells directly originate from E‐cells. The recognition of B‐cells as a separate cell line calls for a new functional interpretation. Ultrastructural and histochemical data suggest a degrading function. B‐cells may clear the hepatopancreas tubules from remnants of digestion in the time span between nutrient absorption and secretion of new digestive enzymes.