bluuebunny/crossref_metadata_2025 huggingface dataset:
Intestinal Ultrastructure of Nerita picea (Mollusca: Gastropoda), an Intertidal Marine Snail of Hawaii
Authors: Pfeiffer Carl J.
Published: April 2010

The neritid snail Nerita picea is a marine prosobranch mollusc which resides high in the intertidal zone on the Hawaiian Islands. Since other studies have shown considerable variations in molluscan gut histology and the relatively few recent ultrastructural reports have revealed novel cellular structures in the molluscan gastrointestinal tract, this investigation was directed toward ultrastructural clarification of the neritid intestine.

Seven principal cell types constituted the intestinal architecture, including absorptive cells, zymogen cells, neural and endocrine cells, myocytes, pigment and gland cells. The intestinal epithelium was composed mainly of tall ciliated (9 plus 2 complement of microtubules) columnar absorptive cells which also possessed microvilli, extensive deposits of non‐membrane‐bound lipid‐like droplets, and large reservoirs of glycogen‐like granules. Less frequent, columnar zymogen cells contained numerous large zymogen secretory granules and possessed microvilli but not cilia. Small endocrine‐like cells with secretory granules were observed basolaterally between some absorptive cells, resembling mammalian gut endocrine cells. Nerve fibers were prevalent in close association with the epithelial cells. A thin layer of non‐striated muscle was present, as well as a serosally located gland composed of storage cells with a granular matrix and large granules.
A Systematic Survey of the Occurrence of the Hypothalamic Saccus Vasculosus in Teleost Fish
Authors: Tsuneki Kazuhiko
Published: April 2010

The saccus vasculosus (SV) was examined histologically in more than 200 species of teleosts. The Atherinomorpha (Cyprinodontiformes and Atheriniformes) completely lack the SV. Many primary freshwater teleosts (Osteoglossiformes, Cypriniformes, Characiformes, Siluriformes, Gymnotiformes, and Synbranchiformes) possess none or a reduced SV. Some secondary freshwater teleosts also possess a reduced SV, but other secondary freshwater teleosts have a well‐developed SV. Some marine teleosts swimming in the surface water, for example, the Clupeiformes and Scombridae, possess a somewhat reduced SV. Bathypelagic teleosts also possess a rather reduced SV. On the other hand, most marine teleosts, benthic or nektonic in the subsurface water, have a well‐developed SV. The examples are the Anguilliformes, Scorpaeniformes, Perciformes, Pleuronectiformes, and Tetraodontiformes. Since all non‐teleostean actinopterygians possess a well‐deveoped SV, it is assumed that the earliest teleosts also possessed a SV. In the course of adaptive radiation, some teleost groups certainly have reduced or lost the SV while others developed it to various degrees. Reduction or development of the SV might be influenced more easily by environments in certain groups and might be constrained more strongly by phylogenetic lineages in other groups.
The Electrosensory Cells of the Ampullary Organ of the Transparent Catfish (Kryptopterus bicirrhus)
Authors: Jørgensen J. Mørup
Published: April 2010

An easy method to demonstrate epidermal sensory organs is described. With the dye Daspei, sensory cells as well as their nerves are visible in the fluorescence microscope. Actin filaments in pore cells and sensory cells are demonstrated with rhodamine‐labelled phalloidin, and the distribution of microtubules is described after fixation in albumin‐osmium tetroxide‐glutaral‐dehyde fixation.
Ultrastructure and Development of the Eyes of Larval Kronborgia isopodicola (Platyhelminthes, Fecampiidae)
Authors: Watson N. A. , Williams J. B. , Rohde K.
Published: April 2010

The structure and development of the paired eyes of the larva of Kronborgia isopodicola were studied by electron microscopy. Each ocellus, located anterolateral to the brain, is of the inverse rhabdomeric type. A supportive cell contains 10–12 rows of concentrically arranged crystalline plates forming a cup‐shaped reflective structure (mirror), the opening of which faces laterally. Three large dendritic processes penentrate the opening and each terminates in a rhabdomere. The cell body of each dendrite lies slightly behind the margin of the mirror cell. Cytoplasmic extensions of the supportive/mirror cell project across the opening, interposing between the dendritic processes. A secretory process (possibly neurosecretory) passes in front of the eyecup in contact with dendritic processes and the extensions of the supportive cell. Reflective layers consisting of rows of crystalline platelets are widely distributed in the animal kingdom, but among the Platyhelminthes this type of reflective ocellus has previously been reported only from Polystomatidae (Monogenea).
The Ultrastructure of the Spermatozoa of Three Species of Myobatrachid Frogs (Anura, Amphibia) with Phylogenetic Considerations
Authors: Lee Michael S. Y. , Jamieson Barrie G. M.
Published: April 2010

Comparison of the spermatozoa of three genera of limnodynastines (Myobatrachidae: Anura) with those of 42 other species of frogs (in 11 families) previously examined allows the following phylogenetic inferences. The bufonoid neobatrachians (corresponding with the Arcifera of some classifications) form a monophyletic assemblage which is characterized by the possession, unique for the Anura, of a conical perforatorium; the rod‐like perforatorium, which is plesiomorphic for tetrapods, is absent. Of the taxa investigated, the myobatrachids appear to be the sister‐group of the remaining bufonoids, here termed eubufonoids (leptodactylids, rhinodermatids, hylids, and bufonids). The spermatozoa of the myobatrachids Limnodynastes, Neobatrachus, and Mixophyes are very similar to each other despite extremely varied fertilization biology. Symplesiomorphies for the Anura which they exhibit include the conical acrosome with subacrosomal material, the elongate, cylindrical nucleus, single flagellum and, paralleling this, an undulating membrane which is supported by a longitudinal element, the axial (major) fibre, the latter being accompanied in the midpiece by mitochondria. A myobatrachid synapomorphy appears to be the presence of a periaxial sheath enclosing the axial fibre of the flagellum. Forward extension of the axial fibre into the centriolar fossa in myobatrachids is seen elsewhere only exceptionally (in the bufonid Nectophrynoides). Bufonids, and most other eubufonoids including leptodactylids, differ apomorphically from Limnodynastes, and Neobatrachus in location of the mitochondria at the axonemal end (and in a collar) rather than the axial fibre end of the undulating membrane. In Mixophyes, mitochondria surround the nuclear‐axonemal junction in a cytoplasmic droplet and are probably shed with this at maturity.
The Phylogenetic Position of the Rhizocephala: Are They Truly Barnacles?
Authors: Høeg Jens T.
Published: April 2010

Incorporation of the Rhizocephala in the Cirripedia, reflecting the traditional view that these parasites evolved from a setose feeding barnacle, has recently been challenged in favour of rhizocephalans being the sister group to all other Thecostraca or a scenario where they evolved from a free‐living, ‘precirripede’ ancestor. Adult morphology is useless in discussing the monophyly of the Cirripedia, since rhizocephalan adults are too reduced to furnish any phylogenetic evidence. But numerous, detailed similarities in nauplii and cyprids of the Thoracica, Acrothoracica and Rhizocephala as well as the ultrastructure of their sperm are synapomorphic relative to other Thecostraca and indicate that these three orders form a monophylum. There is evidence that the stylet in the rhizocephalan kentrogon is homologous to an element in the ancestral mouth field. If so, the Rhizocephala probably evolved before setose feeding was adopted, and constitute the sister group to the Acrothoracica and Thoracica. This conclusion is based on frail evidence so the term Cirripedia should be retained to comprise the Rhizocephala, Thoracica, and Acrothoracica. These three orders all possess remarkably similar cyprids, adapted to accomplish irreversible settlement by cement secretion and initiate metamorphosis, so their last common ancestor was most probably a permanently sessile organism.
Holistic Pattern Analysis as an Alternative to Pattern Cladistics in Hypothesizing Crustacean Phylogenetic Sequences
Authors: Watling Les
Published: April 2010

There has been a growing realization that ‘true’ phylogenetic relationships cannot be determined using pattern cladistical methods alone. The applications of such techniques to the problem of crustacean evolution is first examined using the results presented by Wilson (in this issue). It is found that the degree of correlation of characters in the head vs trunk regions explains very well the grouping of taxa in the cladograms, suggesting that the groups are nothing more than mathematical constructs. The argument is presented that functions of different parts of the crustacean body need to be determined, along with an understanding of how the body morphology is designed in accordance with the dominant functions. A method for producing hypothesized phylogenetic sequences from an analysis of body morphology is proposed and examined using the amphipod family Iphimediidae. It is suggested that cladograms are merely hypotheses and can be tested using functional morphological information of the type outlined.
On the Distribution of the Crustacean Dorsal Organ
Authors: Martin Joel W. , Laverack Michael S.
Published: April 2010

An oval, dorsal organ, variously bearing four minute pits around a central pore and/or encircled by a cuticular border, has been reported for the cephalic region of various groups of living and fossil crustaceans. Although varying somewhat in location and in size, the organ appears basically uniform in organization in at least two of the major crustacean taxa: Branchiopoda (especially Laevicaudata) and Malacostraca (Decapoda and Syncarida). Little is known about its ultrastructure and function in various groups, and it is likely that the term ‘dorsal organ’ also has been applied to several nonhomologous structures. In particular, the embryonic dorsal organ, reviewed recently by Fioroni (Fioroni, P. 1980.—Zoologische Jahrbücher (Anatomie) 104: 425–465) and apparently functioning in nutrition and ecdysis, is not the topic of this paper; that organ is similar in name and location only and appears in embryonic uniramians, chelicerates, and crustaceans. The function of the dorsal organ in branchiopods is in ion regulation, possibly a secondary modification of the original function in marine crustaceans, which is unknown. In larval decapods, the organ probably functions as a chemo‐ or mechano‐receptor. We review the known occurrence of the crustacean dorsal organ, describe the similarities and differences in structure in various taxa, and review the competing hypotheses concerning its function. Phylogenetic implications are discussed.
To the Question of Eyes in Primitive Crustaceans
Authors: Elofsson Rolf
Published: April 2010

Based on a review of studies of functional and comparative anatomy of crustacean eyes, a hypothesis is formed on eyes in primitive crustaceans. It is suggested that they were similar to present‐day frontal eyes of the malacostracan type. Neuronal architecture suggests that the development to apposition compound eye followed two main routes, one seen in malacostracans and the other in non‐malacostracans. Within the two subgroups different and separate lines have been followed to form specialized apposition types and, within the Malacostraca, superposition eyes as pointed out by Nilsson (Nilsson, D. E. 1989. Facets of vision, pp. 30–73).
Phylogeny of Selected Maxillopodan and Other Crustacean Taxa Based on 18S Ribosomal Nucleotide Sequences: A Preliminary Analysis
Authors: Abele L. G. , Spears T. , Kim W. , Applegate M.
Published: April 2010

Relationships among the following taxa were examined based on 18S ribosomal RNA and DNA nucleotide sequences: Branchiopoda (Branchinecta packardi), Ostracoda (two podocopid species), Branchiura (Argulus nobilis), Pentastomida (Porocephalus crotali), Copepoda (Calanus pacificus, Macrocyclops albidus), Thoracica (Balanus eburneus, Calantica villosca), Acrothoracica (Trypetesa lampas), and Decapoda (Procambarus leonensis, Callinectes sapidus). Phylogenetic relationships were inferred by maximum parsimony and results evaluated by bootstrapping. With Branchinecta packardi as an outgroup, the following tree was inferred: the first branch leads to a node that joins a pentastome, a branchiuran and the two ostracodes; the second branch leads to a node that has the two copepods as a sister taxon to a clade that includes the acrothoracican and thoracicans; the last branch leads to a node joining the two decapods. The analyses suggest: (1) acrothoracicans diverged very early from the cirripede line and are not derived from a lepadomorph‐like ancestor; (2) branchiurans are not related to either copepods or thecostracans but are closely allied with pentastomes; and (3) the Maxillopoda, broadly defined, is not a monophyletic taxon. These results differ from previous studies of these groups.
Chemical Nature and Mode of Stabilization of Egg‐shell in Helicometra pulchella (Rudolphi, 1819) (Digenea: Opecoelidae)
Authors: Kalantan A. M. N. , Arfin M. , Alyousif Mohamed S.
Published: April 2010

The chemical nature and mode of stabilization of egg‐shell protein in digenetic trematode Helicometra pulchella (Rudolphi, 1819) have been investigated using histochemical techniques. It was found that the egg‐shell is stabilized by quinone‐tanning together with dityrosine. Other structural proteins (elastin, collagen and keratin‐like proteins), glycogen and acid mucopolysaccharides were absent in egg‐shell. Tyrosine was present in vitelline cells and immature egg‐shell indicating that the proteins involved in quinone‐tanning were tyrosine rich and tyrosyl residues are modified to form dityrosine in mature egg‐shell.
Glial Cell Composition and Ultrastructure of the Caudal Spinal Cord of Young and Adult Tuataras, Sphenodon punctatus
Authors: Alibardi Lorenzo
Published: April 2010

Research on the caudal spinal cord (SC) of three young and three adult tuataras (Sphenodon punctatus) has revealed that most of the glial cells were well differentiated as astrocytes and oligodendrocytes. The former type was not completely differentiated 3 months post‐hatching, but was the main glial cell type at the age of 1 yr and in adulthood. Smaller numbers of oligodendrocytes were found in the white matter of adult animals than fibrous astrocytes. It was concluded that during growth, there is a progressive decrease in the dark, basophilic and electron‐dense glioblasts, most of which develop as astrocytes.
Note on the Rod‐like Photoreceptors in the Retina of the Snake Telescopus fallax (Fleischmann, 1831)
Authors: Munk O. , Rasmussen J. B.
Published: April 2010

Abstract A previous light microscopic study of the retina of Telescopus fallax has showed the presence of three types of photoreceptors: large single cones (type A), large double cones (type B), and small single rods (type D). The present electron microscopic study has demonstrated that the small single rod is a morphological cone characterized by possessing a slightly tapering outer segment and a very extensive zone of continuity between the discs and the plasma membrane of the outer segment.
Ultrastructure of Axial Vascular and Coelomic Organs in Comasterid Featherstars (Echinodermata: Crinoidea)
Authors: Balser Elizabeth J. , Ruppert Edward E.
Published: April 2010

Abstract The spongy body of Davidaster rubiginosa, D. discoidea, and Comactinia meridionalis, is an axial haemal plexus consisting of two structurally similar, but positionally distinct, regions: an oral circumesophageal part and an aboral part which lies lateral to the axial organ. The axial organ is a large axial blood vessel which is infiltrated by hollow cellular tubes lined with monociliated epithelial cells. The spongy body plexus is a tangle of small blood vessels overlain by podocytes and myocytes. The spongy body and the axial organ are situated in the axial coelom, which is confluent with the perivisceral coelom, the water vascular system, and the parietal canals. The parietal canals open to the exterior via ciliated tegmenal ducts and surface pores. The crinoid spongy body is morphologically similar to the axial gland of asteroids, ophiuroids, and echinoids (AOE). Although the axial glands of these three classes of echinoderms are mutually homologous structures, the homology of the crinoid spongy body and the AOE axial gland is questionable because of differences in organization and developmental origin. Alternatively, the crinoid spongy body may be homologous to asteroid gastric haemal tufts, which are podocyte‐covered blood vessels suspended in the perivisceral coelom. The functional organization of the spongy body suggests a filtration nephridium and predicts an excretory function. An alternative hypothesis is that the spongy body is a site of nutrient transfer from the blood vascular system to the perivisceral coelom.
Egg Envelope Cytodifferentiation in the Colonial Ascidian Botryllus schlosseri (Tunicata)
Authors: Manni Lucia , Zaniolo Giovanna , Burighel Paolo
Published: April 2010

Abstract The formation and cytodifferentiation of egg envelopes were studied at the ultrastructural level in blastozooids of Botryllus schlosseri. The process was divided into five recognized stages of oogenesis. First, the small young oocytes (stage 1) are contacted by scattered cells (primary follicle cells—PFC) which adhere to the oolemma at several junctional spots. PFC extend all around the growing oocyte, acquire polarity, and form a layer covered externally by a thin basal membrane (stage 2). At stage 3 isolated cells are recognizable between the PFC layer and oocyte. They never form junctions with the oocyte and represent prospective inner follicle cells (IFC) and test cells (TC), the latter being progressively received in superficial depressions in the oocyte. The layer of PFC, which maintains junctions with the oolemma, represents prospective outer follicle cells (OFC). PFC are considered to be the source of the three cellular envelopes because a contribution from mesenchymatous elements was not observed. At the beginning of vitellogenesis (stage 4), the vitelline coat (VC) becomes recognizable as a loose net covering the oocyte and TC. It is crossed by the oocyte microvilli and OFC projections which meet and form numerous small junctional plaques, some of them resembling gap junctions. IFC, VC and TC show marked signs of differentiation with approaching ovulation. OFC differentiate completely before ovulation (stage 5) and are engaged in intense synthesis of proteins which may be transferred and taken by endocytosis into the oocyte for yolk formation. Experiments with injected horseradish peroxidase also revealed that proteins present in the blood may reach the oocyte via the intercellular pathway, overcoming OFC and IFC. The possible roles of all the egg envelopes are discussed.
Ultrastructure of Spermiogenesis in Acanthocotyle and Myxinidocotyle (Platyhelminthes, Monogenea, Acanthocotylidae)
Authors: Justine Jean‐Lou , Afzelius Björn A. , Malmberg Göran , Mattei Xavier
Published: April 2010

Abstract Spermiogenesis was studied by transmission electron microscopy in the acanthocotylid monogeneans Myxinidocotyle californica (from Eptatretus stoutii) and Acanthocotyle lobianchi (from Raja clavata). In Myxinidocotyle and Acanthocotyle, the zone of differentiation shows two 9+‘1’ axonemes, the elongating nucleus and mitochondrion, and a single cortical cytoplasmic microtubule. This single microtubule is found in the mature spermatozoon of both species and was also noted in capsalids. This requires a modified definition of ‘pattern 2’ of spermatozoa which becomes: ‘spermatozoa with two axonemes and no cortical microtubules, except one single element much shorter than the spermatozoon’. A very unusual structure was found in Myxinidocotyle, but not in Acanthocotyle: the centriolar derivative of one of the 9+‘1’ axonemes is made up of 18 diverging singlets of unequal length associated with electron‐dense cytoplasm. This seems to be the first case of a centriolar derivative without nine‐fold symmetry associated with an axoneme with nine‐fold symmetry.
Ciliary Bands in Echinoderm Larvae: Evidence for Structural Homologies and a Common Plan
Authors: Lacalli T. C.
Published: April 2010

Abstract A series of laterally projecting ridges develop along the ciliary band of late stage auricularia larvae. These are similar in position to the larval arms of bipinnaria larvae and the epaulettes and vibratile lobes of echinoid pluteus larvae, all of which structures are potentially homologous. When the auricularia is converted to a doliolaria with a series of circumferential ciliary bands, the ridges of the former are retained as basic elements from which the circumferential bands of the latter then develop. There is a simple repeating pattern in the arrangement of these elements in which bands composed of two elements alternate with bands composed of four. The available evidence does not resolve the question of which of the above four larval types, whether feeding or non‐feeding, is more primitive. The common plan apparent among them suggests, however, that this plan, whatever its origin, predates the diversification of larval types among eleutherozoan echinoderms.
Skeletal Ultrastructure in the Cyclostome Bryozoan Hornera
Authors: Taylor Paul D. , Jones Chris G.
Published: April 2010

Abstract Scanning electron microscopy of calcified walls in two species of the cyclostome bryozoan Hornera has revealed previously undescribed details of skeletal morphology and growth. The calcitic interior walls of both H. robusta MacGillivray and H. squamosa Hutton have a laminated structure. Walls are extended at distal growing edges where the formation of new crystallites is concentrated and wall fabric is nacreous or semi‐nacreous. New crystallites are seeded on the surface of existing crystallites as six‐sided rhombs. At the centres of the rhombs in H. robusta there are often three ‘spikes' which point towards alternate sides of the rhomb. Screw dislocations resulting in spiral overgrowths are also common at these distal wall edges. Wall thickening occurs further proximally where walls develop a regularly foliated structure of imbricated laths growing towards the colony base. Although often thought to be ubiquitous in cyclostomes, the division of walls into three layers (an inner, primary layer flanked on both sides by secondary layers) is absent in Hornera. Wall ultrastructure contrasts strongly with the lamellar–fibrous–lamellar structure recently described from cinctiporid cyclostomes. The c‐axes of the crystallites are orientated perpendicular to the wall surface in Hornera, unlike cinctiporids in which they are orientated within the plane of the wall. Apparent similarities in ultrastructure suggest that Hornera may provide a good model for wall growth in extinct trepostome bryozoans.
Structural Organization of the Blood‐sinus Systems in Lampreys and Hagfish: Functional and Evolutionary Interpretations
Authors: Tsuneki Kazuhiko , Koshida Yutaka
Published: April 2010

Abstract The head and branchial regions of larval and adult lampreys and hagfish were studied histologically in serial sections. The most remarkable feature in these extant agnathans was the occurrence of large blood‐sinuses. In larval lampreys, blood‐sinuses are well developed in the velum, an organ that functions to introduce water and accompanying food particles from the mouth into the gill and alimentary regions. The sinuses in the velum may act to transduce the force of contraction of velar muscles to the stroke‐like movement of the velum; without these sinuses muscular contractions might simply cause the velum to collapse. In adult lampreys, blood‐sinuses are well developed in the peribranchial space that surrounds the branchial (gill) sac and is surrounded by the branchial pouch. It is possible that the force of contractions of the branchial‐pouch muscles is transduced effectively to the branchial sac via the peribranchial blood‐sinus and facilitates the expiration of water through the external gill pores. If the peribranchial sinus were absent, the muscular contraction might deform the branchial sac in an inappropriate manner. In the hagfish, the blood‐sinus system is also well developed in the velum and peribranchial space, although the peribranchial sinus lies outside the muscular branchial pouch. In agnathans, the blood‐sinus system may function, at least in part, as a kind of hydrostatic skeleton that transduces the force generated by muscular contraction.
Light and Electron (SEM, TEM) Microscopy of Taste Buds in the Tench Tinca tinca (Pisces: Cyprinidae)
Authors: Żuwata Krystyna , Jakubowski Michał
Published: April 2010

Abstract The ultrastructure and quantitative distribution of the taste buds (TBs) were studied in the oropharyngeal cavity and in skin from the head of the tench. All TBs are of similar structure, following an orthodox plan: the basal cells (1–2) are the basis of the bud, and vertically elongated gustatory cells and supporting cells span from the basal membrane to the apex where they form a sensory zone (known as the gustatory pore).

The basal cells have finger‐like processes pointing towards the nerve plexus. They do not show any hemidesmosomal connections with the basal membrane. Typical afferent synaptic contacts were found only at the basal cells and gustatory cells while no such contacts were found at the supporting cells.

The highest concentration of TBs (up to 170 TBs mm 2) occurs in the epithelial lining of the distal part of the pharynx, the least (12 TBs mm 2) in the epidermis of the distal part of the head. The tops of most TBs protrude above the epithelium but their gustatory pores are slightly sunken, thereby protecting the apical processes of the gustatory cells from mechanical stimulation.
Yet Another Interpretation of the Coelacanthiform Basicranial Muscle and its Innervation
Authors: Bjerring Hans C.
Published: April 2010

AbstractA compilation of newly published information on the innervation of the basicranial muscle in the living tufttailLatimeria chalumnaeand data obtained from other craniates, extant as well as extinct, suggest that the coelacanthiform basicranial musculature and the nerve supply which pertains to it are trimetameric in character rather than monometameric, as usually reported. This result supports the available data on the basic composition of the head of craniate animals and gives no support to a recently suggested homology between the tufttail basicranial muscles and the tetrapod retractor bulbi musculature.
Scanning and Transmission Electron Microscopical Observations on the Larvae of Priapulus caudatus (Priapulida)
Authors: Higgins R. P. , Storch V. , Shirley T. C.
Published: April 2010

Abstract Scanning electron microscopical studies revealed four distinct morphological larva‐types (not instars) of Priapulus caudatus whose lorica‐length measured 82–860 μm. The smallest of the larvae are round to oval, have 20 longitudinal ridges, a series of transverse ridges, and have two pairs of laterally situated tubuli near the posterior limits. The second larva‐type is dorsoventrally compressed, has a single dorsal and single unsculptured ventral plate each with a prominent midridge near the anterior limits, three infolded lateral plates with a pair of tubuli near the posterior limits. The third and fourth larva‐types remain dorsoventrally flattened; the third larva‐type has less pronounced sculpturing than the fourth larva‐type and is smaller; two pairs of tubuli are situated as in the previous stage. The number and arrangement of scalids on the introvert and pharyngeal teeth differ according to each of the four larva‐types and are described. The ultrastructure of all organ systems is described. All scalids are sensilla equipped with ciliated receptor cells. The cuticle is similar to the cuticle in the adult and differs fundamentally from the cuticle of larval Halicryptus. The trunk is richly supplied with sensory structures. Trunk tubuli contain secretory cells. Posteriorly, a gland complex was found which presumably is the precursor of the equivalent gland in postlarvae and adults. The implications of the first larva‐type's structural similarity to the larva of Tubiluchus are discussed.
The Digestive Tract of the Spatangoid Echinoid Echinocardium cordatum (Echinodermata): Morphofunctional Study
Authors: DeRidder C. , Jangoux M.
Published: April 2010

Abstract Echinocardium cordatum is a detritus‐feeder. Its digestive tract has three functional parts: the mucus‐secreting oesophagus where lubrication and sediment compaction occur, the protein‐secreting stomach and gastric caecum where extracellular digestion occurs, and the absorptive non‐secretory siphon, intestine, intestinal caecum and rectum. Each region harbours typical enterocytes. Acinar mucous glands occur in the posterior oesophagus prior to the incurrent aperture of the siphon; their secretions prevent sediment grains from entering the siphon and may be stimulated by epineural nerves running in the connective tissue layer. The siphon is a sucking organ, and its cytological features indicate that it is a site for absorption of dissolved organic matter. Enterocytes of the intestinal caecum show basal specializations, suggesting that it is a site of active exchange between coelom and gut. This caecum contains symbiotic sulphide‐oxidizing bacteria. Collagen fibres are well developed in organs subjected to severe deformations (e.g., oesophagus and siphon); elastic‐like fibres are conspicuous around haemal lacunae and at the attachment areas of gut‐suspending mesenteries. Circular muscles are seen along the whole gut, whereas longitudinal muscles may be absent in areas such as the siphon. The bulky alimentary bolus that occurs in the ascending segments of the gut is transported by peristalsis; the scattered sediment grains that occur in horizontal segments are presumably moved by the contractions of the gut‐suspending mesenteries.
The Morphology of the Naupliar Stages of Sacculina carcini(Crustacea: Cirripedia: Rhizocephala)
Authors: Collis Sarah A. , Walker Graham
Published: April 2010

A morphological study was carried out on the fournaupliar stages of Sacculina carciniusing mainly scanning electron microscopy. Frontal horns were present and throughout development the typical nauplius limbs remained simple and gnathobases were lacking. Such features are characteristic of other lecithotrophic barnacle nauplii. The presence of a vestigial ventral thoracic process was evident on the stage III nauplius and was even more prominent on the stage IV nauplius. These observations confirm that the rhizocephalan nauplius is close to the thoracican nauplius form and lend strong support for the retention of the Rhizocephala within the Cirripedia.
Fine Structure of the Female Intoshia variabili(Alexandrov & Sljusarev) (Mesozoa: Orthonectida)
Authors: Slyusarev George S.
Published: April 2010

The morphology and fine structure of female Intoshia variabili, new combination for Rhopalura variabiliAlexandrov & Sljusarev, 1992, were studied with transmission electron microscopy. The body surface is covered with a 3‐layered cuticula, under which is a layer of ciliated + non‐ciliated cells arranged in alternating rings around the body. Ciliated cells have lateral extensions that intercalate with the non‐ciliated cells. The kinetosome of each cilium has two longitudinally oriented cross‐striated rootlets. The outer surface of the ciliated cells is covered with small tubercles, and the cytoplasm of these cells contains granules, vacuoles, mitochondria, fibrillar structures and lamellary bodies. A band of dense fibrils passes through the upper part of each ring of cells, going from one cell junction to another, encircling the entire body. Between the layer of ciliated + non–ciliated cells and the oocytes, elongated contractile cells from 4–5 longitudinal columns and 1 ring, the latter at the level of ciliated rings 7–9. The contractile cells contain thick and thin longitudinally oriented fibrils. The oocytes contain a large nucleus, numerous mitochondria, electron–dense granules and 1–2 spherical structures. An anteriorly situated, ciliated goblet–like receptor, not described for any other orthonectids, consists of three closely apposed cells, the upper part of which contains densely packed cilia. The genital pore opens through a non–ciliated cell and is surrounded by several cells with granules.
Variability in the Presence of Elastic Fibre‐like Structures in the Ventral Aorta of Agnathans (Hagfishes and Lampreys)
Authors: Welsch U. , Potter I. C.
Published: April 2010

This paper investigates whether elastic fibre‐like structures are present in the ventral aorta of hagfishes and lampreys. Fibres, which are morphologically similar to the elastic fibres of gnathostomatous (jawed) vertebrates, are shown to be present in the ventral aorta of the hagfish Paramyxine atami, and also, but to a lesser extent, the dorsal aorta of this species and the ventral aorta of another hagfish, Eptatretus stouti.The ‘elastic’ tissue formed irregular sheet‐like aggregates, comprising well‐defined amorphous material surrounded by tubular microfibrils, whose diameters ranged from 10 to 15 nm. While this tissue was most abundant in the same region of the aortae as that occupied by the elastica interna in the blood vessels of gnathostomes, it was also found deeper in the wall of these blood vessels. Although tubular microfibrils were found in the ventral aorta of the hagfish Myxine glutinosaand the lamprey Geotria australis, these were never associated with well–defined, amorphous material. This parallels the results of previous studies on Myxine glutinosaand another species of lamprey, Petromyzon marinus.Thus, the elastic fibre–like tissues found in the ventral aortae of P. atamiand E. stoutiprovide the first examples of such structures in this region in agnathan vertebrates.
Ultrastructural Study of Oogenesis in the Compound Ascidian Botryllus schlosseri(Tunicata)
Authors: Manni Lucia , Zaniolo Giovanna , Burighel Paolo
Published: April 2010

On the basis of ultrastructural observations, Botryllus schlosserioogenesis is divided into five stages, of which stages 1–3 and 4–5 refer to previtellogenic and vitellogenic phases, respectively. Special attention was paid to the mechanisms of acquisition of nutrient, organelle differentiation, yolk formation and relationships between oocyte and its complex investment.

In the gonadal blastema of young buds, small oocytes are recognized early, partially covered by a few primary follicle cells, the presumptive source of all the cellular envelopes of the fully grown oocyte. Some oocytes are seen in the zygotene–pachytene phase, characterized by synaptonemal complexes, but most are found at the end of the diplotene, when oocytes commonly stop meiosis, grow and migrate through blood vessels into blastozooids of successive generations. In laboratory animals, only 1–3 oocytes per blastozooid can reach complete maturity.

Detailed observations on the time of appearance and development of organelles, microvilli and endocytotic activity in growing oocytes are also reported. Ultrastructural differentiation and the relationships between oocytes and their envelopes all indicate that both auto– and hetero–synthetic mechanisms for yolk formation occur in B. schlosseri.These mechanisms and the possible role of egg envelopes in the process are discussed, comparing the large yolky eggs of B. schlosseriwith those of solitary species.
Comparative SEM Studies of Lattice Organs: Putative Sensory Structures on the Carapace of Larvae from Ascothoracida and Cirripedia (Crustacea Maxillopoda Thecostraca)
Authors: Jensen Peter Gram , Moyse John , Høeg Jens , Al‐Yahya Hamad
Published: April 2010

Putative sensory structures, called lattice organs, were studied with scanning electron microscopy from ascothoracid or cypris larvae representing a wide range of families of the Ascothoracida and Cirripedia. These organs, situated dorsally on the carapace were, with few exceptions, always found in two anterior and three posterior pairs. The lattice organ morphology displayed by the Ascothoracida, a seta–like structure with a terminal pore, is believed to be the most plesiomorphic condition. Within the Cirripedia lattice organ morphology varied from types resembling the Ascothoracida in the Acrothoracica and the lepadomorph Capitulum mitella, to an elongate pore field with a larger terminal pore in most Thoracica and Rhizocephala. Akentrogonid Rhizocephala seem to display the most apomorphic condition. While lattice organ morphology was generally constant at the family level, cases were seen where closely related species such as Chthamalus stellatusand Chthamalus montaguishowed minor, but clear cut differences.

Lattice organs in 2 + 3 pairs are argued to represent a synapomorphy for the Ascothoracida and the Cirripedia. The results confirm that the cyprid morphology at the ultrastructural level will prove to be of high value in estimating phylogeny within the Cirripedia.
Ultrastructure of the Spermatozoon of Avitellina centripunctata(Cestoda, Cyclophyllidea), a Parasite of the Small Intestine of Cattle in Senegal
Authors: Bǎ Cheikh T. , Marchand Bernard
Published: April 2010

The Avitellina centripunctataspermatozoon is filiform, tapered at both ends and lacks mitochondria. The anterior extremity exhibits an apical cone and a crested–like body 150–200 nm thick. The axoneme is surrounded by a fine layer of lucent cytoplasm and a sheath of electron–dense material. The cytoplasm is slightly electron–dense at the anterior tip of the apical cone and in region IV of the spermatozoon. Over the rest of the gamete it is subdivided into numerous electron–lucent compartments by irregularly spaced walls. The nucleus is electron–dense. It interposes itself between the cortical microtubules which are all electron–dense centred and spiralized along their whole length. An apical zone containing spiralized microtubules, cortical microtubules which are all electron–dense centred and stop before reaching the posterior extremity of the nucleus, as well as the subdivision into cavities by intracytoplasmic proteinaceous material, have never been described before in a cestod. Moreover, the crested–like body of Avitellina centripunctatais the thickest of those which have been described to date in the cestods.
Ultrastructure of Spermiogenesis and the Spermatozoon of Mathevotaenia herpestis(Cestoda), Intestinal Parasite of Atelerix albiventrisin Senegal
Authors: Bǎ Cheikh T. , Marchand Bernard
Published: April 2010

Spermiogenesis in M. herpestisbegins with the formation of a differentiation zone which contains two centrioles associated with an electron–dense, finely granular material. This granular material very quickly becomes striated, a median cytoplasmic extension forms, one of the centrioles becomes laterally oriented in a cytoplasmic bud and the other gives rise to a flagellum. After the migration of the nucleus, a helicoidal crested–like body forms, then the old spermatid separates from the residual cytoplasm. The mature M. herpestisspermatozoon exhibits an apical cone of electron–dense material, a crested–like body and cortical microtubules which are electron–dense centred and spiralized except at their posterior extremity where they are parallel to the spermatozoon axis. The axoneme is of the 9 + ‘1’ pattern. It reaches the posterior extremity of the gamete where the cytoplasm is very electron–dense. The presence of centrioles flanked by ‘striated roots’ has never, to our knowledge, been reported in a platyhelminth. Likewise, a nucleus with an annular cross–section and unevenly distributed electron–dense peri–axonemal material has never been described in a cestod.
Retinal Pigment Epithelium–Calycal Processes Association in the Catfish Clarias batrachus(Linnaeus, 1758)
Authors: Nag Tapas Chandra
Published: April 2010

Abstract In the duplex retina of the catfish Clarias batrachus(Linnaeus, 1758), the apical processes of the pigment epithelial cells have been found by transmission electron microscopy to be in intimate contact with the calycal processes around the basal portion of the photoreceptor outer segments. It is hypothesized that the retinal pigment epithelium effectively transports synthesized products and metabolites to the photoreceptor inner segments via the anatomical zone of the apical–calycal processes interface in this species.
Morphology and Growth of Lateral Line Organs of the Rainbow Trout (Oncorhynchus mykiss)
Authors: Siregar Yusni Ikhwan
Published: April 2010

Abstract The morphology and growth of selected lateral line organs of the rainbow trout (Oncorhynchus mykiss) are described. Canal neuromasts of the infraorbital and operculo–mandibular canal of three different–sized trout have been examined by light microscopy. The number of neuromasts and pores, as well as their distribution, is constant in all sizes of fish. However, the area and estimated number of hair cells (HC) of the examined neuromasts increase with size and with a correlation coefficient (r2) of 0.90 and 0.87, respectively. It was found that area and estimated hair cell number of neuromasts increase 6‐fold in fish from 10 to 30 cm total length (TL). Based on calculation of the hair cell number in small and large fish, a net addition of 1 and 6 HC per day is suggested for IO and OM neuromasts, respectively.
Developmental Patterns and Hypotheses of Homology in the Antennules of Thecostracan Nauplius Larvae (Crustacea)
Authors: Grygier Mark J.
Published: April 2010

Abstract Antennular development is summarized for non–brooded nauplius larvae of the Ascothoracida (families Lauridae and Petrarcidae) and for selected nauplii of the Facetotecta. In the Cirripedia Thoracica, nauplii of the Lepadomorpha and Scalpellomorpha/Sessilia are shown to differ in their patterns of antennular setal addition and division into articles, and one or two possible apomorphies for each group are identified. Several variations of the scalpellomorphan/sessilian pattern are outlined. These data on the Ascothoracida, Facetotecta, and Cirripedia provide the basis for modifying an earlier proposal of structural homologies among the naupliar antennules of thecostracan maxillopodans. ‘Virtual’ articles (ones that are never completely free) are invoked to account for setae that ‘jump’ across article boundaries at molts and for supposedly homologous setae found on adjacent articles in different taxa. The identities of the preaxial setae in the Cirripedia are ambiguous and force consideration of two models for that group and for the thecostracan antennular Bauplan; the latter may have included up to 11 or 12 articles, more than the previously supposed 8 or 9. The scoring of characters used in an earlier cladistic study of thecostracan and other maxillopodan taxa is not seriously affected. A comparison with the Cambrian maxillopodan Bredocarissuggests that division of the antennule into discrete articles in extant thecostracans is an apomorphic state and that yet one more apical article once existed in the maxillopodan antennule.
The Canaliculi of Williamson in Holostean Bone (Osteichthyes, Actinopterygii): a Structural and Ultrastructural Study
Authors: Sire Jean‐Yves , Meunier François J.
Published: April 2010

Abstract The organization and structure of the canaliculi of Williamson and their associated cells are studied in the bone of various elements of the dermal skeleton and of the endoskeleton in extinct and living Holostei, and in regenerated scales of Lepisosteus oculatus.Light microscopical observations of ground and semi–thin sections of various skeletal elements confirm and complete previous data on the organization of the canaliculi. Transmission electron microscopy enables original descriptions of the cells of Williamson, of their cytoplasmic processes occupying the canaliculi of Williamson and of their environment. The cytoplasmic content of the cells of Williamson and their processes is composed mainly of microfilaments, microtubules, small vesicles and mitochondria; this does not resemble what is known for osteoblasts and odontoblasts. Moreover, as an alternative for the lack of ontogenetic series, regenerated scales are used to describe recently formed cells of Williamson at the upper scale surface and within vascular canals. Our cytological observations support a nutritive role for the cells of Williamson and their processes. The phylogenetical origins of the cells of Williamson are discussed.
Ultrastructural Studies of the Visceral Muscles of Chaetognaths
Authors: Duvert Michel , Salat Christiane
Published: April 2010

The visceral musculature of Chaetognaths was studied with special attention given to the digestive apparatus muscle. In the head the digestive apparatus muscle is relatively thick; individual muscles are difficult to distinguish at the anatomical level; in the anterior part of the oesophagus discontinuous bundles and layers of cross‐striated fibers are found. As a group however, the oesophageal musculature completely covers the oesophageal epithelium. The prominent muscle layers around the oesophagus probably help to force food into the intestine against the turgor pressure of the trunk cavity which tends to collapse the intestine. Around the intestine the musculature is largely circular and smooth. The intestinal epithelium is ciliated despite its muscular covering. Muscle fibers are not individually innervated. They form myoepithelial structures with various intercellular junction types. In the intestinal muscle the fibers show myoendothelial‐like junctions. Sphincters composed of myoepidermal cells surround the anus and the female gonopores. The somatic side of the general cavity is lined with a polymorphic squamous epithelium. Sometimes myoepithelial cells are found, with the occasional presence of extracellular matrix basal to the layer of the squamous epithelium. The ontogenetic relations between the polymorphic epithelium and the composite ‘mesenteries’ remain to be established. We have now some idea about the architecture of the body of Chaetognaths in relation to contractile structures.
Skeletal Ultrastructure in some Cyclostome Bryozoans of the Family Lichenoporidae
Authors: Taylor Paul D. , Weedon Michael J. , Jones Chris G.
Published: April 2010

The ultrastructure of the skeleton is described in six species of lichenoporid cyclostome bryozoans using field emission SEM. Both interior walls (vertical, interzooidal walls, and brood chamber roofs and floors) and exterior walls (basal walls) are initially secreted as tiny wedge‐shaped crystallites without a strong preferred orientation. These are seeded directly onto pre‐existing crystallites in the case of interior walls, but onto the organic cuticle in exterior walls, the bases of the crystallites forming a tightly packed mosaic against the cuticle. With growth the wedges become longer, broader and relatively flatter, developing into platey crystallites. These crystallites grow predominantly distally (i.e. parallel to wall growth direction) and are closely imbricated in a foliated fabric. Local disruptions to this pattern occur, especially in association with crystallite division along “divergent zones”. The pattern also breaks down in old walls where crystallite growing edges become less evident and imbrication is poorly developed. Although conforming to this general model, some differences exist between species of lichenoporids, and in the patterns found in different parts of the skeleton (e.g. apertural spines). Lichenoporid ultrastructure differs from that of both cinctiporid and hornerid cyclostomes: notably, lichenoporids lack the layer of transverse fibres found in cinctiporids, and their predominant distal growth direction of crystallites contrasts with the proximal direction found in hornerids.