bluuebunny/crossref_metadata_2025 huggingface dataset:
Coelomic Cells in the Connective Tissue Spaces of the Clitellar Epithelium of Lumbricus friendi Cognetti, 1904 (Oligochaeta): an Ultrastructural Study
Authors: de Quiros Isabel F. Bernaldo , Benito Jesus
Published: April 2010

The ultrastructure of the connective tissue spaces in the clitellar epithelium has been studied in the earthworm Lumbricus friendi. Four morphological types of coelomic cells are described: amoebocytes, mucocyte‐like cells, pigment cells and crystal‐containing cells. The amoebocytes are characterized by the presence of spherical to oval electron‐dense granules, phagocytic vacuoles and numerous microtubules located in the Golgi areas. The mucocyte‐like cells show the features of the mucocytes reported in enchytraeid worms (globular inclusions with filamentous and homogeneous, moderately electron‐dense material, as well as a filopodous process). The pigment cells contain typical spindle‐shaped osmiophilic granules, microtubules (not reported before) and glycogen particles. The crystal‐containing cells show inclusions which are polygonal in section with a striated substructure (periodicity of about 4.5 nm). Apart from the mucocyte‐like cells, the coelomocytes showed cytoplasmic processes attached to the basement membrane of the spaces. The possible functions of these cells are discussed and a common peritoneal origin is postulated on the base of their morphological and cytological features.
The Nervous System of the Male Dinophilus gyrociliatus (Annelida: Polychaeta). I. Number, Types and Distribution Pattern of Sensory Cells
Authors: Windoffer Reinhard , Westheide Wilfried
Published: April 2010

The entire nervous system of the smallest annelid hitherto known, the dwarf male of the highly dimorphic species Dinophilus gyrociliatus, has been reconstructed by means of TEM investigations of serial ultrathin sections. Altogether there are 68 neurons, 40 of which have a sensory function. The structure and distribution of them is described. The receptor endings of the 20 sensory cells of each side are located either in two groups — the anterior receptor group and the posterior receptor group — or are singly positioned in the integument. Structural differences of the apical portion of the dendrites enables four types of receptors to be distinguished: three types with emergent cilia and one type with non‐emergent cilia. Neurons with emergent cilia can be monociliated collar cells as well as mono‐ or multiciliated cells without collar. Special vesicle‐in‐vesicle structures, are located close to the basal portion of the cilia in some of these cells. The non‐emergent cilia border closely to a neighbouring epidermal cell and contain a prominent intraciliary vesicle. The function of receptors is discussed with regard to a comparison with receptors in other polychaete species, structural specializations and their distribution pattern on the animal's surface.
Settlement and Metamorphosis of Rhabdopleura normani (Hemichordata: Pterobranchia)
Authors: Lester Susan M.
Published: April 2010

Settling and metamorphosing larvae of the pterobranch hemichordate Rhabdopleura normani from Bermuda were examined with light microscopy, providing the first detailed description of the morphological changes during larval metamorphosis in pterobranchs. The swimming larvae settle within 24 h after being released from the parent tube. The settled larva immediately everts the ventral depression and surrounds itself with a translucent, sealed cocoon. During metamorphosis, which takes place over 7–10 days within the protective cocoon, structural changes occur in the following sequence: (1) differentiation of the oral shield from the anterior region; (2) budding of the two arms from the mid‐dorsal surface; (3) development of the posterior stalk from the adhesive organ; (4) budding of the tentacles on the arms; (5) formation of the pharynx from invaginated ectoderm; (6) formation of the gut and pericardium from the remaining mesenchyme. The gut is the last structure to become functional. The larva relies on stored nutrients throughout metamorphosis. The metamorphosed juvenile builds a tube at an opening in the cocoon and begins to feed. Similarities with lecithotrophic bryozoan and enteropneust larvae are discussed.
Localisation of Vanadium, Sulphur and Bromine Within the Vanadocytes of Ascidia mentula Müller: A Quantitative Electron Probe X‐Ray Microanalytical Study
Authors: Lane D. J. W. , Wilkes S. L.
Published: April 2010

Levels of vanadium, sulphur and bromine within the vanadopohores of Ascidia mentula vanadocytes have been determined by quantitative X‐ray microanalytical techniques. Values obtained for vanadophore vanadium in thin sections correspond to 2.5‐3.25% or 0.5‐0.65 molal aqueous solutions in vivo. Quantitation of sulphur in thin sections gives levels an order of magnitude lower than for vanadium, but it is likely that major losses of sulphur have occurred, since analysis of unfixed, air dried vanadocytes gives V/S atomic ratios close to unity. This 1: 1 ratio may have implications for the structure of the vanadium complex. Quantitation of bromine is less reliable, but levels of this halogen in vanadocytes are significant. The possibility that bromine, in the form of brominated metabolites, together with vanadium and acid, contribute to a multicomponent chemical defense role in ascidians is discussed.
Ultrastructural Study of Spermatogenesis and Mature Spermatozoa of Paravortex cardii (Platyhelminthes, Dalyellioida)
Authors: Cifrian Blanca , Garcia‐Corrales Pedro , Alós Susana Martinez
Published: April 2010

The spermatogenesis and mature spermatozoon of Paravortex cardii were studied by transmission electron microscopy. Meiotic divisions occur without cytokinesis and the spermatid nuclei appear embedded in a common cytoplasmic mass. The mature spermatozoon is filiform, very regular in contour and circular in cross‐section. A tubular lining of microtubules lying close to the plasma membrane is found along the spermatozoon. Rows of spherical glycogen particles with helical arrangement lay internal to the cortical microtubules. The spermatozoon of P. cardii may be divided into two regions, nuclear and cytoplasmic regions. The nuclear region contains an elongated nucleus with a densely packed nuclear material. The mitochondria are distributed throughout the cytoplasmic region; they pack tightly together and often fuse to form one large one. This spermatozoon lacks both acrosome and the so‐called dense bodies. A ciliary or centriolar apparatus was not observed. Accordingly, the spermatozoon of P. cardii is considered to be aflagellate in type. Spermatozoa are compared among flatworms, and some considerations on the significance of their ultrastructure for phylogeny in the Platyhelminthes are tentatively given.
A Scanning Electron Microscopic Study on the Thyroid Follicle of the Hagfish Eptatretus burgeri
Authors: Suzuki Shintaro , Kawabata Isuzu
Published: April 2010

The external form of the follicles was mostly spherical or oval and the large oval follicles reached more than 300 times 180 μm in size. Cytoplasmic inclusions of various sizes were observed in the follicular epithelium. Follicles were composed of hexagonal epithelial cells, and on the apical surface of the cells many microvilli were found (380–500 microvilli per cell) with globular or amorphic cytoplasmic protrusions. In a few cells a central cilium was also observed. From these results a relationship between thyroid structure and function in the hagfish is discussed.
The Fine Structure of the Testis of a Lancelet (=Amphioxus), Branchiostoma floridae (Phylum Chordata: Subphylum Cephalochordata= Acrania)
Authors: Holland Nicholas D. , Holland Linda Z.
Published: April 2010

The germinal and non‐germinal cells of the ripe lancelet testis are described by transmission electron microscopy. The visceral peritoneum of the testis is composed of myoepithelial cells, and the haemal layer consists of regions of narrow sinuses and conspicuously thicker blood vessels filled with blood plasma and bounded by basal laminae. Within the germinal epithelium and the testicular lumen, the non‐germinal cells, which are not abundant, contain conspicuous lysosomes and mitochondria with tubular cristae, indicating that they may be involved in steroid synthesis. In the ripe testis, the non‐germinal cells do not appear to be organized into a blood‐testis barrier. Ail types of spermatogenic cells may be flagellated and are joined in small groups by intercellular bridges. During differentiation of the spermatids, the Golgi complex is associated with formation of the acrosomal vesicle near the posterior pole of the cell. A remarkable feature is the dual origin of the subacrosomal material: one component originates at the posterior end of the spermatid, and the other at the anterior end. Subsequently, the two components merge into one after the acrosomal vesicle has migrated to its definitive anterior position in the mature spermatozoon.
Macrophages and Reticulum Cells in the Spleen of the Dogfish, Scyliorhinus canicula
Authors: Pulsford A. , Zapata A.
Published: April 2010

The presence and ultrastructural features of reticulum cells and macrophages were studied in the spleen of the dogfish Scyliorhinus canicula. Three morphologically distinguishable regions of the spleen were identified: the white pulp, the red pulp and the ellipsoids. In all three, the splenic parenchyma was a meshwork supported by reticulum cells and fibres. Reticulum cells in both the white and the red pulp are irregular elements, the processes of which are joined by cell junctions and embrace developing reticular fibres. The ellipsoids of the dogfish spleen are terminal branches of the splenic arteries of the white pulp, with a sheath consisting of reticulum cells, reticular fibres, ground substance, macrophages and occasional lymphocytes. Isolated melanomacrophages also occur in the ellipsoid walls as well as in the red pulp. In both the white and the red pulp phagocytic reticulum cells, and macrophages appear frequently forming cell associations with surrounding blood cells, mainly lymphocytes. The functional significance of the ellipsoids and the cell‐cell clusters of the white and the red pulp is discussed in relation to the immune capacities demonstrated in elasmobranchs.
Morphological Studies on the Testis of Adults of Moniliformis (Acanthocephala)
Authors: Asaolu S. O.
Published: April 2010

The morphology of the testis in young adult males of Moniliformis dubius developing in the rat has been studied with the aid of light and electron microscopes. In one‐day‐old male worms, the testis is organised as two zones. One zone consists of individual germ‐line cells, while the other consists of a supporting syncytium which embeds the cells and forms the boundary of the testis. The surface of the testis is covered by a fibrous non‐cytoplasmic coat. In seven‐day‐old male worms, the syncytium has lost its compact form, breaking down into multinucleate units connected by cytoplasmic processes and apparently forming a loose syncytial network throughout the testis. The germ cells are now randomly distributed and are surrounded by wide spaces among the segments of the supporting syncytium. The fibrous coat, lined internally by an irregular layer of the syncytium, forms the testis envelope. This basic structure is maintained in the testis of 14‐day‐old and sexually mature male worms.
Fine Structure of the Cellular Parenchyma and Extracellular Matrix of Ophiotaenia loennbergii (Cestoda: Proteocephalidea)
Authors: Conn David Bruce , Rocco Laura J.
Published: April 2010

The cellular parenchyma and extracellular matrix (ECM) of Ophiotaenia loennbergii were studied by light and transmission electron microscopy. The parenchyma consists primarily of muscle cells divided into three compartments that maintain some cytoplasmic continuity: (1) myofibrils; (2) broadly lobate nucleated myocytons (muscle cell perikarya) with the perinuclear cytoplasm dominated by greatly dilated cisternae of granular endoplasmic reticulum: (3) thin anucleated sarcoplasmic extensions formed in sheets with abundant glycogen and extremely large lipid droplets, which cause the cytoplasmic sheets to bulge. These cellular compartments are separated from each other by abundant ECM, which consists primarily of an electron‐lucent amorphous ground substance. Filaments are scarce in all ECM except the tegumental basement lamella. This is the first report of parenchyma and ECM fine structure in the Proteocephalidea. The results provide additional evidence that cestode parenchyma is formed from similar cells, but is subject to substantial variability between different species.
The Ultrastructure of the Proboscis in Psammorhynchus tubulipenis Karling, 1964 and Cytocystis clitellatus Karling, 1953 (Platyhelminthes, Rhabdocoela)
Authors: De Vocht Alain
Published: April 2010

The ultrastructural organization of the proboscis in two species of free‐living Platyhelminthes, Psammorhynchus tubulipenis and Cytocystis clitellatus is very alike but differs from previously described species. Both sheath and cone epithelium are composed of two circumferential belts. Only the basal cone epithelium is syncytial, while no nuclei were found in the distal belt of the sheath epithelium. The sheath epithelium is characterized by numerous infoldings of the basal plasma membrane. The nuclei present in the bulb belong to the proximal belt of the sheath epithelium and the apical cone epithelium. Nuclei of the basal cone epithelium are located insunk behind the proboscis bulb. The insunk cell parts pierce the septum of the bulb laterally near the proximal end. Different types of gland necks and sensory cells pierce the epithelia. Associated with the distal belt of the sheath epithelium, two sensory organs are found, containing multiciliary receptors with modified axonemata. Differences in organization of the proboscis musculature are described and compared with the organization in other species. The systematic position of both species is discussed in the light of the new findings.
Fine Structure of the Midgut and Hindgut in Lepidocampa weberi (Insecta, Diplura)
Authors: Xue L. , Dallai R. , Yin W.‐Y.
Published: April 2010

The fine structure of the alimentary canal, especially the midgut and hindgut of Lepidocampa weberi (Diplura: Campodeidae) is described. The general organization of the canal is similar to that of Campodea. The midgut epithelium is composed of columnar apical microvillated cells. Each nucleus contains a single intranuclear crystal. Close to the pyloric region, the posterior midgut cells are devoid of microvilli and intranuclear crystals. There is no special pyloric chamber as in Protura or pyloric cuticular ring as in Collembola but a morphological transformation from midgut to hindgut cells. Eight globular Malpighian papillae, consisting of distal microvillated cells and flat proximal cells, open into the gut lumen via ducts formed by hindgut cells. The structure of the hindgut is complicated and can be divided into three segments. The anterior hindgut cells have an irregular shape and compact cytoplasm. A striking interdigitation between the large bottle‐shaped epithelial cells and longitudinal muscle cells occurs in the middle segment of the hindgut. The thick cuticle gives rise to long spikes projecting into the gut lumen. The posterior hindgut cells possess the morphological features for water reabsorption. Some hypotheses are advanced about the function of the different regions of the gut.
Lectin Histochemistry on Glycoconjugates of the Epidermis and Dermal Glands of Xenopus laevis (Daudin, 1802)
Authors: Danguy André , Genten Franck
Published: April 2010

We performed an investigation at the light microscopical level of the differential distribution of lectin‐binding sites among cells of the epidermis and glandular domains of the African clawed frog Xenopus laevis. Using a panel of biotinylated lectins (Con‐A. PSA, LCA, UEA‐I, DBA, SBA, SJA, RCA‐I, BSL‐I, WGA, s‐WGA, PHA‐E and PHA‐L) and an avidin–biotin–peroxidase complex (ABC), we have identified specific binding patterns.

The results show that expression of saccharide moieties in Xenopus epidermal keratinocytes is related to the stage of cellular differentiation, different cell layers expressing different sugar residues. Moreover, oliogosaccharides with “identical” biochemically defined sugar compositions can be distinguished. The method allowed further characterization of complex glycoconjugates of dermal glands. In view of these results, the ABC technique and the biotinylated lectins employed in the present study are believed to be a reliable method for the precise localization of saccharide residues of glycoconjugates present in ectothermic vertebrates.
Internal Organization of Limbate Polychaete Setae (Sabella penicillus), with Notes on Bending Stiffness
Authors: Kryvi Harald , Sørvig Tryggve
Published: April 2010

The internal architecture of the limbate setae of Sabella penicillus (Sabellidae) is described, based on transmission and scanning electron microscopy. The setae are composed of a number of cylindrical channels (mean= 877). The number of channels is less than one third of the number of spines on the distal swollen part of the setae. In the proximal shaft, channels are hollow and cylindrical. Towards the expanded distal part of the setae, the lumen gradually disappears, and the shape of the wall of the channels changes from circular to hexagonal. With no lumen, the term microrod is suggested as more descriptive than ‘channel’ for the units in this part of the seta. The solid microrods change from a strictly hexagonal shape to a more irregular indented shape, and gradually taper off towards the tip region. The cortical layer of the expanded part contains numerous irregular cavities. Morphometric data on the organization of the internal components are presented. When tested for flexibility, the setae broke when bent to a mean of 93.6° (±9°). Calculations based on morphometry show that the bending stiffness is up to 19 times greater in the swollen part than in the shaft, and it is reduced to about 1/50 in the distal whip.
Ultrastructure of the Geogarypus nigrimanus Spermatozoon (Arachnida, Pseudoscorpionida)
Authors: Dallai Romano , Callaini Giuliano
Published: April 2010

The ultrastructure of the spermatozoon of Geogarypus nigrimanus (Arachnida, Pseudoscorpionida) is described. The spermatozoon is composed of a small elliptic nucleus, a short flagellum and a very long and complex acrosome. In the male genital ducts, as in other studied species of pseudoscorpions, the sperm components are rolled up to form a globular structure enclosed in a cyst wall. The Geogarypus spermatozoon with a reduced flagellum and a giant acrosome seems to be evolutionary more advanced than spermatozoa from other pseudoscorpions.
Larval Tunic and the Function of the Test Cells in Ascidians
Authors: Cloney Richard A.
Published: April 2010

Abstract In normal ascidian development, cuticular fins begin to form at the late tailbud stage and are fully formed at hatching. When one or several neurulae were manually demembranated (follicle cells, vitelline coat and test cells removed) and cultured in seawater they failed to form caudal fins. Fins were normal when the follicle cells alone were removed. The shape of the fins was normal when demembranation was delayed to the late tailbud stage. Does demembranation cause the loss of an essential factor produced by the embryos themselves or do the test cells provide a factor for fin morphogenesis? Demembranated neurulae of Ascidia callosa were cultured in groups ranging in size from 2 to 80 in 1 ml volumes of seawater. The mean lengths of the caudal fins increased with group size. In larger groups, some embryos developed fins that were normal in shape and as long as undemembranated controls. Results were similar with Corella inflata. These experiments suggest that a diffusible substance from the embryos facilitates fin morphogenesis and that test cells are not required. Test cells deposit ‘ornaments’ on the tunic in some species. In other species no ornaments are produced. Ten families are compared. It is proposed that the test cells make the tunic hydrophilic.
FMRFamide‐like Peptides in the Nervous and Endocrine Systems of the Digenean Helminth Echinostoma liei
Authors: Riddell Jennifer H. , Whitfield Philip J. , Balogun M. A. , Thorndyke Michael C.
Published: April 2010

FMRFamide‐like immunoreactivity has been demonstrated in the digenean trematode Echinostoma liei. The functions of FMRFamide‐like substances appear to be many and varied within the invertebrates, where they are involved in neurotransmission, cardiovascular regulation, muscular contraction and/or relaxation, and in co‐ordination of growth and maturation. It is clearly indicated that FMRFamide‐like substances function as neurotransmitter/neuromodulator in E. liei by the abundance of positively stained nerve fibres and perikarya seen throughout the CNS and PNS. A single endocrine‐like cell also showing FMRFamide‐like immunoreactivity is situated within the muscular cirrus pouch.
Trans‐epidermal Transport and Storage of Calcium in Holthuisana transversa (Brachyura; Sundathelphusidae) During Premoult
Authors: Greenaway Peter , Farrelly Caroline
Published: April 2010

Holthuisana transversa reabsorbs much of its exoskeletal calcium in the last 3 days before ecdysis and stores it in circulating granules in the haemocoel and in non‐circulating granules in the subepidermal connective tissue. Calcium enters the epidermal cells from the moulting fluid, probably through their apical microvilli and is either incorporated into intracellular calcium granules or exits the cell via the basolateral membranes to be used in formation of two other granule types. Intracellular granules (0.4–2 μm long) form in large masses in the apical cytoplasm of the epidermal cells. They are formed as membrane‐bound vesicles by the Golgi, and calcium and organic matrix material are added from the surrounding cytoplasm. As development proceeds, lamellae appear and calcium carbonate is deposited in the matrix. Granule masses move basally and are stored in the connective tissue. Calcium is also incorporated into extracellular large granules (0.8–3.8 μm long) which are formed in narrow intercellular channels between epidermal cells. A third granule type (small granules, 0.26 μm diameter) is formed in subepidermal connective tissue cells and released into the haemolymph in very large numbers. Calcium was identified in the two larger granule types using X‐ray microanalysis and significant amounts of phosphorus and potassium were also present in the large granules. A model for ion cycling between the exoskeleton and granules is presented.
Egg Turning During Incubation has no Effect Upon the Growth of Embryos of Alligator mississippiensis
Authors: Deeming D. C. , Ferguson M. W. J.
Published: April 2010

Alligator eggs are not turned during incubation, instead the embryo adheres to the top inside of the shell. Turning is alleged to shear off the embryo and kill it. Avian egg turning allegedly facilitates embryonic development by stimulating growth of the area vasculosa and minimizing the effects of unstirred yolk and albumen layers.

From day 10 to day 45 of incubation, alligator eggs were experimentally turned, gently, through ± 60° in an hourly cycle. This turning regime killed only 6 out of 25 embryos. Compared with unturned controls, no significant effects were observed on the growth, production of extraembryonic fluids or utilization of albumen and yolk for those embryos that survived turning. The protein concentration of amniotic fluid at various stages of alligator development was examined in eggs incubated at 30 and 33°C. The fluid contained very little protein (max <8 mg) at any time: the protein concentration did not change consistently as development progressed. Differences in response to egg turning in birds and reptiles may be associated with the length of the incubation period, the protein content of the albumen and the mechanism of albumen utilization.
Comparison of Alimentary Systems in Shelled and Non‐shelled Sacoglossa (Mollusca, Opisthobranchia)
Authors: Jensen Kathe R.
Published: April 2010

The Sacoglossa (= Ascoglossa) comprise a ‘complete’ evolutionary series from species with a large shell into which the animal can withdraw completely, through species with a reduced shell covering only the visceral mass, to shell‐less (‘nudibranchiate’) forms some of which have lateral wing‐like extensions, parapodia, others bearing leaf‐like or cylindrical dorsal appendages, cerata. The Sacoglossa are all specialized suctorial feeders, and almost all are stenophagous herbivores. Hence many anatomical adaptations to a particular food occur in the alimentary system. However, a number of characters seem to reflect phylogenetic relationships as well. Among these are presence/absence, shape, and position of pharyngeal pouches, basic shape of radular teeth, branching pattern of digestive gland, and position of anus. The classificatory significance of these characters is discussed.
On the Innervation and Homologues of the Cephalic Appendages of the Aphroditacea (Polychaeta)
Authors: Orrhage Lars
Published: April 2010

Abstract Earlier papers dealing with the innervation and homologues of the anterior end appendages of some aphroditacean families were re‐studied. However valuable these earlier works may be, in some respects they proved to be insufficient for detailed comparisons with other polychaete families and some of their statements are quite contradictory. This prompted a re‐investigation of the central‐most parts of the nervous system of representatives of the families Polynoidae, Sigalionidae, Aphroditidae and Acoetidae. In the present paper, the brain commissures and the innervation of, inter alia, the antennae, the palps and the ommatophores (when present) in Lepidonotus squamatus, Harmothoe longisetis, Leanira (Sthenolepis) tetragona, Laetmonice producta benthaliana, and Panthalis oerstedi are described. Special attention is paid to the much‐debated question about the presence or absence of a palp ganglion. The results, summarized in schematic diagrams, are compared with corresponding observations of the brains of, above all, the ‘spiomorphic’ polychaetes. Using the first Remanian criterion for identifying homologies, equivalents in the aphroditacean brain and the central nervous system of ‘sedentary’ families are proposed. By this a broader base is established for the discussion regarding the fundamental constitution of the anterior end of the polychaetes and the structure and homologues of their cephalic appendages.
A Study of the Morphology and Biology of Thompsonia littoralis (Crustacea: Cirripedia: Rhizocephala)
Authors: Lützen Jørgen , Jespersen Åse
Published: April 2010

Interna development within the intertidal tropical crab, Leptodius exaratus, requires up to 4.5 months; the roots become distributed from the CNS along the major nerves and, when the crab moults, results in emergence of numerous externae located symmetrically on the abdomen and bases of the thoracic appendages. As many externae drop off, their number is continuously reduced; the survivors reach sexual maturity and ovulate after 2.5 months and complete embryonic development after 2 more months. At the next moult a new and more numerous generation of externae appears, and this is repeated until the crab dies. Presence of externae significantly prolongs the host's normal intermoult period and minimizes its growth. The parasite has little effect on the host's sexual characters although females are normally sterilized. The cuticle of the externa is moulted once, leaving a distinct annulus around the stalk. Spermatogonia are presumably injected by male cyprids into the female externa and develop into sperm within one or more vesicular spermatogenic bodies in its mantle. The eggs are laid through a single oviduct into the mantle cavity where they become fertilized and develop into cyprids that are liberated at the disintegration of the externa.
A Study of the Alimentary Canal of the Brachyopterygian Fish Polypterus senegalus with Electron Microscopy and Immunohistochemistry
Authors: Burkhardt‐Holm Patricia , Holmgren Susanne
Published: April 2010

The gastro‐intestinal tract of Polypterus senegalus was investigated by means of electron microscopy and immunohistochemistry. Cilia‐bearing cells can be observed over the whole length of the intestine. All enterocytes along the intestinal tract are characterized by apical pinocytotic vesicles. However, a typical intestinal region, which in other fish is characterized by large supranuclear vacuoles, is lacking. By means of electron microscopy, four types of endocrine cells and three types of nerve cell processes can be identified. By means of immunohistochemistry, endocrine cells with immunoreactivity for bombesin‐, enkephalin‐, G/CCK‐, 5‐HT‐, somatostatin‐ and substance P‐antisera can be found. Nerve cell processes show immunoreactivity for bombesin‐, enkephalin‐, 5‐HT‐, substance P‐ and VIP‐antisera. The number of immunoreactive endocrine cells, nerve cells and nerve cell processes is different for each part of the gut.
Scanning Electron Microscopy and X‐ray Diffraction Studies of the Macular Crystals in the Chondrostean Fish Erpetoichthys calabaricus (Smith)
Authors: Marmo Francesco , Ariani Antonio P. , Balsamo Giuseppe , Avallone Bice
Published: April 2010

Morphologic and crystallographic studies of the otoliths of the reed‐fish Erpetoichthys calabaricus showed (1) aragonite statoliths with a serrated surface, and (2) two populations of statoconia: one of numerous discoid biconvex crystals of vaterite, the other of pseudohexagonal crystals of aragonite. We suggest that the presence of two calcium carbonate polymorphs in the statoacoustic organs of this archaic fish may have an evolutionary, as well as a systematic and functional significance.
Blood Supply to the Interventricular Septum of the Heart in Rodents with Intramyocardial Coronary Arteries
Authors: Durán Ana C. , Sans‐Coma Valentín , Arqué Josep Maria , Cardo Manuel , Fernández Borja , Franco Diego
Published: April 2010

The blood supply to the interventricular septum of the heart was studied in a sample of 1634 specimens belonging to four rodent families, Cricetidae, Arvicolidae, Gliridae, and Muridae. Most specimens (n = 1604) were examined using a corrosion‐cast technique, while the remaining 30 were studied by histological techniques. In 1417 cases the coronary artery pattern was normal, and the interventricular septum was fundamentally supplied by one or rarely two septal arteries arising from the right and/or left coronary arteries. In 72 specimens the right and left coronary arteries were normal, while the septal artery arose from a separate ostium in the aorta, behaving as a third coronary artery. The remaining 145 animals possessed anomalies in the origin of the coronary arteries, and the septum was also principally irrigated by a septal artery. In 5 of these 145 anomalous cases the septal artery originated from a separate ostium in the aorta. In all specimens examined a less important vascularization of the septum was established through thinner penetrating vessels originating from the right and/or left coronary arteries. Existence of one or rarely two septal arteries is the most constant feature of the coronary artery arrangement in rodents with intramyocardial coronary arteries.
Ultrastructure of the Flame Bulbs and Protonephridial Capillaries of Artioposthia sp. (Platyhelminthes, Tricladida, Geoplanidae)
Authors: Rohde Klaus , Watson N. A.
Published: April 2010

The protonephridial terminal complex of Artioposthia is formed by one or two terminal cells, each with a nucleus located in the lateral wall of the flame bulb, and probably two proximal canal cells forming the wall of the protonephridial capillary. The weir is restricted to the proximal parts of the flame bulbs and consists of convoluted slits separated by thick cytoplasmic columns. Cross‐striated ciliary rootlets running parallel with and obliquely or transversely to the longitudinal axis of the flame bulbs strengthen the walls of the flame bulbs and, to a lesser degree, that of the capillary. Numerous cristate mitochondria are present in the terminal and proximal canal cells. Cytoplasmic processes extend from the terminal cells into the adjacent tissue, and narrow internal leptotriches extend from the cytoplasm of the terminal cells into the lumen of the flame bulbs. The wall of the capillary contains many interconnected, liquid filled spaces that communicate with the lumen of the capillary, and two septate junctions. Phylogenetic implications of the findings are discussed.
Comparative Ultrastructural Studies on the Pineal Organ of the Mexican Catfish Rhamdia laticauda Heckel, 1858 and One of its Cave‐dwelling Derivates (Pimelodidae, Teleostei)
Authors: Langecker Thomas G. , Wilkens Horst
Published: April 2010

The pineal organ of the epigean catfish Rhamdia laticauda and of its cave‐dwelling derivate from Cueva del Tunel in Zongolica, Mexico, was examined ultrastructurally. The pineal of the epigean form is relatively small but ultrastructurally well differentiated and characterized as a metabolically active, photoneuroendocrine organ. The outer segments of the sensory cells are composed of 32–55 very regularly arranged sacculi which are obviously functioning in photoreception. Furthermore, the presence of electron‐dense vesicles, free ribosomes, conspicuously well‐developed Golgi bodies, and large amounts of rough and smooth endoplasmic reticulum in the cytoplasm provide evidence for a secretory activity of the sensory cells. The only regressive traits in the pineal of the cave form regard the outer segments: there are few disintegrated, whorl‐like outer segments and the number of sacculi exhibits an increased variability. Compared with other morphological structures dependent on light, for example the eyes, the degree of regression is very low. It is suggested that this is due to a remaining secretory role of the sensory cells, which prevents the functionless, photoreceptive outer segments from rapid degeneration by developmental constraints.
Distribution and Ultrastructure of Ciliated Sensory Receptors in the Posterior Mantle Epithelium of Dentalium rectius (Mollusca, Scaphopoda)
Authors: Reynolds Patrick D.
Published: April 2010

The scaphopod mantle cavity opens posteriorly via the pavilion, a siphon‐like extension of the posterior mantle through which the respiratory currents pass. The pavilion was examined for ciliated sensory cells in Dentalium rectius Carpenter, 1865, using scanning and transmission electron micropscopy. Three types of sensory receptor were distinguished on the basis of number, length and ultrastructure of the associated cilia. Receptors with 2–5 cilia of ˜ 1.7 μm length lined the pavilion edge. A second type, possessing 1–2 cilia, ˜ 8.2 μm in length, was found throughout the internal and on part of the external surface of the pavilion. The third receptor type consisted of a rigid bundle of 16–40 cilia with a length of ˜ 14.4 μm, and was present close to the periphery and at the base of the pavilion near the entrance to the mantle cavity. The structure and distribution of these cells are similar to peripheral chemo‐ and mechanoreceptors which sample respiratory currents and the surrounding environment in other molluscs, but they may assume a greater functional significance in scaphopods due to the absence of an osphradium in this class.
Phylogenetic Significance of the Burgess Shale Crustacean Canadaspis
Authors: Briggs Derek E. G.
Published: April 2010

The crustaceans, like the other major living groups of arthropods, have a long evolutionary history. The earliest examples occur in the Cambrian, and fossils of this age are a critical source of evidence of relationships both within the Crustacea, and between the Crustacea and other major arthropod groups. Canadaspis perfecta, from the Middle Cambrian Burgess Shale, is important as one of the oldest well‐documented crustaceans. The evidence for reconstructing its remarkable combination of primitive and derived characters is reviewed, and its possible phylogenetic significance re‐assessed.
Not Yet Proven Crustacea: the Thylacocephala
Authors: Rolfe W. D. Ian
Published: April 2010

The Thylacocephala is a recently recognized extinct group of uncertain, but probably crustacean, affinity, comprising fossils formerly assigned to many different crustacean groups. Key characters are three anterior pairs of subchelate limbs; at least 8 pairs of radiating gills, situated between the trunk and carapace, the most posterior gill lying subhorizontally; and the large posteriorly tapering battery of 8(–?20) elongated limb protopods with tenuous distal filaments. Thylacocephala bear huge anterior structures, variously identified as compound eyes or as a ‘cephalic sac’. Microsclerites borne on this structure may be external, perhaps setae, but need not imply affinity with cirripedes as has been argued. Internal microsclerites have been compared with crystalline cones of a compound eye. More detailed study of well‐preserved material is required to resolve the nature of these microsclerites, to elucidate details of appendages, to locate antennae, and to ascertain limb homologies. Until that work is done, affinities of the Thylacocephala must remain uncertain as must the group's relevance to evolution of Crustacea. Such recent recognition of a distinctive functional model system (Dahl, E. 1976. Zoologica Scripta 5: 163–166) which persisted for at least 340 million years, shows the fossil record still has much to contribute to understanding the pattern of arthropod evolution.
Reflections on the Phylogenetic Position of the Cephalocarida
Authors: Hessler Robert R.
Published: April 2010

This essay re‐evaluates the phylogenetic position of the Cephalocarida in the light of the recently discovered Orsten (Upper Cambrian) crustaceans, the living Remipedia, and new interpretation of the Paleozoic ‘trilobitomorphs’. The Orsten crustaceans reinforce the belief that cephalocarid external morphology is primitive, except to show that the early crustacean trunk limb was almost surely biramous. The epipod appears to be a synapomorphy of the Cephalocarida, Branchiopoda and Malacostraca, thus justifying the existence of the Thoracopoda, which is coequal to the Maxillopoda and Remipedia. External morphology of the Remipedia is too specialized to support the hypothesis that it approximates that of the urcrustacean. Crustaceans and chelicerates are still best regarded as subgroups of the Schizoramia.
Calcification of Cartilage from the Lamprey Petromyzon marinus (L.) in vitro
Authors: Langille Robert M. , Hall Brian K.
Published: April 2010

Abstract Adult and larval lamprey cartilage, normally unmineralized, was cultured in a medium meta‐stable for hydroxyapatite for periods of up to 12 days at 20, 30 or 37°C. Histochemical analysis revealed a temperature‐dependent increase over time in calcium phosphate incorporation into the extracellular matrix (ECM) of adult cartilage concomitant with the incorporation of calcium as detected by gravimetric and radioisotopic methods. Ultrastructural analysis revealed the presence of ECM dense bodies (40 nm average) containing crystalline material which increased in number with increased mineral incorporation but were absent from control cartilage. Additionally, electron‐dense particles (15–20 nm) found in close association with the ECM fibrils in some regions of mineralized cartilage may represent sites of amorphous calcium phosphate. Larval cartilage incorporated much less calcium, less uniformly over time than did adult cartilage. Histochemical and ultrastructural analysis revealed that calcium had accumulated in the chondrocytes instead of the ECM and this proved detrimental, leading to the death of the cells.

The discovery that adult lamprey cartilage calcifies in vitro under appropriate conditions, suggests that petromyzonids, or their direct agnathan ancestors, may have possessed mineralized skeletons and that this ability is ‘repressed’ in extant lampreys owing primarily to the environment they inhabit.
Fine Structure and Behaviour of the So‐called Cuvierian Organs in the Holothuroid Genus Actinopyga (Echinodermata)
Authors: VandenSpiegel Didier , Jangoux Michel
Published: April 2010

Abstract Actinopygid Cuvierian tubules are few in number. They are made of a basal trunk from which arises 2–3 branches. The trunk is smooth and hollow (proximally) or slightly swollen and solid (distally) and the branches consist of a central rachis to which attach many peripheral spherules. The fine structure of the tubules is similar in the three investigated species of Actinopyga but differs considerably from that of non‐actinopygid tubules. Basic behavioural differences occur also as actinopygid Cuvierian tubules cannot elongate nor become sticky, and are not expelled by the individuals. It is concluded that actinopygid Cuvierian tubules do not fulfil a defensive function.
Fine Structure of the Hepatic Sacculations of Glossobalanus minutus (Enteropneusta, Hemichordata)
Authors: Benito Jesús , Fernández Isabel , Pardos Fernando
Published: April 2010

Abstract The hepatic region of Glossobalanus minutus is characterized by deep foldings of the dorsal side of the gut epithelium which affect the neighbouring tissues and structures: coelomic spaces, musculature and epidermis. The following cell types of the gut epithelium are described: vacuolated cells, undifferentiated cells, two types of mucous cells and two types of granular secretory cells. The nature and function of the different cell types are discussed. Data on the general ciliation and subepithelial nerve plexus of the gut epithelium are also given, with special mention of a possible neuroendocrine secretion towards the subjacent blood spaces. A well‐developed blood sinus (gut sinus) lies between the gut and the visceral peritoneum. The ultrastructural features of the gut epithelium and its close association with the blood sinus point to an absorptive function. The coelomic cavity is reduced to a narrow space limited by two peritoneal sheets (visceral and parietal) of myoepithelial nature. Amoebocyte‐like cells (coelomocytes) occur free in the coelomic fluid, and muscular, unicellular bridges are attached to both peritoneal walls across the coelomic space. The dorsal epidermis follows the gut foldings and is formed by flat, overlapping cells. The present observations are compared with previous histological, histochemical and ultrastructural data.
Trichoplax adhaerens (Phylum Placozoa) has Cells that React with Antibodies Against the Neuropeptide RFamide
Authors: Schuchert Peter
Published: April 2010

Abstract The phylum Placozoa contains the most simply organized multicellular animals: they have a thick lower epithelium and a thin upper epithelium with some single cells sandwiched between these layers. Placozoans are generally considered to have no nerve cells or specialized sensory cells. However, the results of this investigation demonstrate the existence of a specific set of cells which react with antibodies against the neuropeptide family RFamide. The RFamide‐positive cells of Trichoplax adhaerens are positioned at some distance along the margin of the animal.
Euspermatozoa, Paraspermatozoa and Spermatozeugmata of Littoraria (Palustorina) articulata (Prosobranchia: Caenogastropoda) with Special Reference to the Pseudotrich
Authors: Healy John M. , Jamieson Barrie G. M.
Published: April 2010

Abstract Paraspermatozoa and euspermatozoa of the littorinid gastropod Littoraria (Palustorina) articulata are examined using transmission electron microscopy and light microscopy. In the seminal vesicle, both sperm types occur, either as free cells or organized into spermatozeugmata. It is shown that the elongate (120–140 μm), flagellum‐like component of the paraspermatozoon is in fact a tubular extension of the plasma membrane which encloses granular material but no axonemes or microtubules. This structure, here termed the pseudotrich, shows no evidence of motility and its function remains obscure. The main body region of the paraspermatozoon (length 32–36 μm) contains numerous spherical vesicles, scattered mitochondria, one or two large, rod‐shaped bodies (length 20–24 μm) and a fusiform, granular body (containing DNA; probably a modified nucleus). The rod‐shaped bodies, granular body and surrounding matrix are contained by a common membrane, and are therefore separated from other contents of the paraspermatozoon. In each spermatozeugma, euspermatozoa are attached via the tips of their acrosomes to the paraspermatozoan body at the opposite end to the pseudotrich. Euspermatozoa exhibit a conical acrosomal complex (with axial rod and basal plate), a tubular nucleus sheathing the axoneme, a midpiece (5–6 helical mitochondrial elements sheathing the axoneme), an annulus (with two rings), a glycogen piece and an end piece (total sperm length 268–272 μm). The euspermatozoa of L. articulata are similar to those of most littorinids and many other caenogastropods. The presence of a pseudotrich in the paraspermatozoon appears to be restricted to the subgenus Palustorina.
The Structure and Origin of the Plasmodium of Rhopalura ophiocomae(Phylum Orthonectida)
Authors: Kozloff Eugene N.
Published: April 2010

Abstract Adult orthonectids develop from germinal cells within a cytoplasmic matrix called a plasmodium. This is generally assumed to be formed by the parasite. In the case of Rhopalura ophiocomae, which lives in the brittle star Amphipholis squamata, the plasmodia occupying the perivisceral coelom are closely associated with the walls of the genital bursae or the gut, and they are covered by peritoneum. They have been reported to contain scattered small nuclei distinct from those within germinal cells, embryos, and adults, but the results of the present study indicate that such nuclei probably do not exist. Furthermore, electron micrographs show that some plasmodia are in continuity with the cytoplasm of contractile cells that lie beneath the peritoneum of a genital bursa or the gut of the host. The matrix of a plasmodium of R. ophiocomaeappears, therefore, to consist of cytoplasm of a contractile cell. It is proposed that after a contractile cell has been entered by an infective cell of the parasite, it hypertrophies, bulging progressively farther into the perivisceral coelom and lifting up the peritoneum, which remains in intimate contact with it.
The Larval Eye of Nannochoristid Scorpionflies (Insecta, Mecoptera)
Authors: Melzer Roland R. , Paulus Hannes F. , Kristensen Niels P.
Published: April 2010

Abstract The stemmata of last–instar Nannochoristalarvae are compound eyes composed of 10 or more ommatidia. Each ommatidium has four Semper cells, four distal and four proximal retinula cells which form a cruciform and layered rhabdom. The ommatidia are separated by epidermal cells (possibly rudimentary pigment cells). Corneal lenses are lacking. At the posterior edge, aberrant stemma units may be present which lack a dioptric apparatus and have a star–shaped rhabdom composed of at least six retinula cells. The stemmata of Nannochoristaappear to be derived from stemmata of the Panorpa‐type (Mecoptera‐Panorpidae). Differences between the stemmata of Nannochoristaand Panorpacan be explained as adaptations to aquatic life (flat cornea) or as regression. A compound larval eye is ascribed to the ground plan of the Mecoptera sensu latoand is considered a genuine plesiomorphy. The identical basic number (seven) of stemmata in the Neuropteroid/Coleoptera assemblage, Amphiesmenoptera and some Mecoptera (Bittacidae, Boreidae) is attributed to parallel evolution.