bluuebunny/crossref_metadata_2025 huggingface dataset:
Larval Attachment by Eversion of the Internal Sac in the Marine Bryozoan Bowerbankia gracilis (Ctenostomata: Vesicularioidea): A Muscle‐Mediated Morphogenetic Movement
Authors: Reed Christopher G.
Published: April 2010

The larval morphology and settlement of the vesicularioid ctenostome bryozoan Bowerbankia gracilis has been investigated by light and electron microscopy in an attempt to elucidate the mechanism of attachment to the substratum at the onset of metamorphosis. The oral epithelium in the free‐swimming larva is infolded to form a glandular internal sac at the oral pole. The internal sac is not specialized into distinct regions, but consists of a uniform, simple columnar epithelium filled with secretory granules. The hemispherical internal sac is underlain by a cup‐shaped layer of undifferentiated cells that constitutes the polypide rudiment. The cupiform layer of undifferentiated cells is in turn embraced by a network of muscle fibers called the rete muscularis. At the onset of metamorphosis, the larva constricts oro‐laterally and the internal sac is everted against the substratum. As the sac everts, the glandular cells secrete an adhesive that is wafted up over the metamorphosing larva by the reversed beating of the coronal cilia. At the same time, the cupiform layer of undifferentiated cells flattens in the plane of the oro‐lateral constriction and doubles in thickness. The cells of the cupiform layer undergo a corresponding transformation from short columnar cells to flask‐shaped cells that bulge into the glandular cells of the internal sac. The narrow ends of the flask‐shaped cells abut the strongly contracted muscle fibers of the rete muscularis. It is hypothesized that the contraction of the muscle fibers of the rete muscularis is responsible for the change in shape of the undifferentiated cells and, consequently, for the eversion of the internal sac. On the basis of this study and a review of the literature, it is concluded that attachment to the substratum at the onset of metamorphosis typically is effected by the eversion of an internal sac in larvae of the ctenostome superfamily Vesicularioidea.
Cypris Settlement, Kentrogon Formation and Host Invasion in the Parasitic Barnacle Lernaeodiscus porcellanae (Müller) (Crustacea: Cirripedia: Rhizocephala)
Authors: Høeg Jens T.
Published: April 2010

The anatomy of the female cypris is very similar to that of cyprids of the Thoracica. There is no development of a preformed kentrogon within the unsettled cypris. Kentrogon formation is completed within 10–20 min after settlement. Elimination of the spent cypris is necessary for successful development. The kentrogon includes a variety of tissues, such as muscles and part of the cement glands. The injection stylet develops in connection with a moult, and it penetrates into the crab gill through the ventral body wall of the kentrogon c. 50 h after settlement. Only a single cell, also recognizable in the unsettled cypris, is injected into the host, while the rest of the kentrogon degenerates after invasion. The speed of kentrogen development and much of the kentrogon anatomy can be interpreted as a defense against host crab grooming. The single invasion cell may either be considered as a stem cell or an egg.
An Ultrastructural Account of Otoplanid Turbellaria Neuroanatomy II. The statocyst design: evolutionary and functional implications
Authors: Ferrero Enrico Antonio , Bedini Celina , Lanfranchi Alberto
Published: April 2010

The statocyst architecture in the three otoplanid species Notocaryoturbella bigermaria Lanfranchi, 1969, Otoplana truncaspina Lanfranchi, 1969 and Parotoplanella heterorhabditica Lanfranchi, 1969 is compared. Common features are: (a) a fibrillar collagen‐like, 0.2 μm thick, investing capsule continuous with the brain capsule; (b) an inner wall made up of six or more flattened and overlapping parietal cells; (c) a statolith forming cell hanging from the dorsal side down in the lumen, with a large statolith containing vacuole; (d) a bilateral pair of spindle shaped accessory cell groups, adjoining the statolith cell and sending projections to the wall—nerve projections run through the capsule; (e) one accessory cell enveloping the other cells of the group has a filament containing cytoplasm, the filaments coverging into a hemidesmosome making contact with a projection coming from a parietal cell; (f) muscles from the longitudinal body musculature inserting onto the capsule externally. The lack of ciliary structures differentiates the turbellarian statocyst from the majority of invertebrate statocysts. The developmental origin, the phylogenetical meaning and the functional and adaptive value of the statocyst in Turbellaria are here commented on.
Balancer Fine Structure of the Pleurodeles Larva
Authors: Fox Harold
Published: April 2010

The paired balancers of larval Pleurodeles waltl, a urodelan species of the Amphibia, were investigated throughout their life span until final degeneration, using electron microscopy. The evidence from cellular ultrastructure illustrates the mucus‐secreting function of these organs, and the outer epithelial cells actively synthesize muco‐proteinaceous substance. An extensive granular endoplasmic reticulum and well developed Golgi complexes participate in the mucus manufacture. The balancer epidermis is also extensively innervated throughout by non‐myelinated neurites, most of them without Schwann cells, a feature which argues strongly in favour of the organ also having a sensory function, whose nature has yet to be determined.
The Alimentary Canal of a Freshwater Copepoda, Macrocyclops albidus, and some Other Cyclopoida
Authors: Defaye Danielle , Such Janine , Dussart Bernard
Published: April 2010

Structural and ultrastructural studies on the gut of a freshwater Cyclopoida, Macrocyclops albidus (Crustacea, Copepoda) during its post‐naupliar development show constant morphological and cytological characteristics. The alimentary canal is composed of three parts: oesophagus, gut and rectum. Three zones are described from the gut, which forms the major part of the alimentary canal. The median part, or midgut, is the more interesting, characterized by its vacuolar cells. All cells of the gut have constant features. An hypothesis on the digestive function is given in relation to behavioral observations and histological and biochemical data.
Estimation of Steroids and Steroid Metabolism in a Lower Vertebrate (Lampetra planeri Bloch)
Authors: Seiler Karl , Seiler Ruth , Ackermann Wilfried , Claus Rainer
Published: April 2010

Pregnenolone, androstenedione and testosterone were identified by RIA in tissue homogenates of the pronephric region, the opisthonephros, the gonads and in plasma samples from male and female immature and mature adult brook lampreys. Additionally, hydroxysteroid dehydrogenase activity was determined spectrophotometrically in homogenates from the same tissues of mature and spent adult brook lampreys employing pregnenolone, testosterone or 3β,17β‐dihydroxy‐5β‐androstane as substrates. The steroid levels show differences corresponding to developmental stages, tissues and sex. Remarkable quantities of testosterone were measured in the testicular tissue homogenates, in homogenates obtained from the pronephric region and in the serum.
Sex Difference in the Cloacal Gland in the Hagfish, Eptatretus burgeri, and its Possible Significance in Reproduction
Authors: Tsuneki Kazuhiko , Suzuki A. , Ouji M.
Published: April 2010

The cloacal gland of the hagfish, Eptatretus burgeri, was studied histologically in four seasons. Before the breeding season (spring and summer) the male cloacal gland was larger than the female cloacal gland. The gland was largest in the males with a more mature testis. After the breeding season (autumn and winter) there was no sex difference in the size of the cloacal gland. The cloacal gland consists of mucus and thread cells, as do the lateral slime glands. The sperm may be entangled within slime in the cloacal gland and be shed outside as a slimy sperm mass. Such a slimy sperm mass may play an important role in reproduction of the hagfish.
The Question of a Presupracleithrum in Brachiopterygian Fishes
Authors: Bjerring Hans C.
Published: April 2010

The presupracleithrum is an exoskeletal pectoral bone that occurs in Paleozoic and Mesozoic actinopterygian fishes. It has been equated more than once with an opercular element in brachiopterygian fishes. In recent cladistic analyses, this alleged homology is used to assign brachiopterygians to actinopterygians. However, a comparison of brachiopterygian and actinopterygian crania shows clearly that the former lack a presupracleithrum.
Histochemical Characterization and Distribution of Fiber Types in the Pectoralis Muscle of the Ostrich (Struthio camelus) and Emu (Dromaius novaehollandiae)
Authors: Rosser Benjamin W. C. , George John C.
Published: April 2010

The muscle fibers of the pectoralis (M. pectoralis pars thoracicus) of a male and a female ostrich (Struthio camelus) and a male and a female emu (Dromaius novaehollandiae) were studied histochemically for succinate dehydrogenase and myofibrillar adenosine triphosphatase. Slow‐tonic (ST), fast‐twitch oxidative‐glycolytic (FOG) and fast‐twitch glycolytic (FG) fibers were approximately equal in number and distribution in the emu pectoralis examined. In the ostriches, both predominantly FG and approximately equal areas, were present. ST fibers were significantly (P ≤ 0.05) larger than the similarly (P ≥ 0.05) sized FG and FOG fibers in the female ostrich and emus. In the male ostrich ST fibers were smaller (P ≤ 0.05) than FG fibers, neither of which were significantly (P ≥ 0.05) different from FOG fibers. The ratites have the greatest percentage and widest distribution of ST fibers found in any avian pectoralis studied to date. This could represent the ancestoral avian pectoralis, neoteny or an effect of flightlessness. ST fibers are used in the maintenance of posture, which is probably the main role of the pectoralis in the emu. The predominantly FG areas of the ostrich are indicative of an additional function, namely, behavioural display. Sexual dimorphism in the ostrich pectoralis is strongly suggested.
On the Fine Structure of the Alimentary Tract of Cephalodiscus gracilis (Pterobranchia, Hemichordata)
Authors: Dilly Peter Noel , Welsch Ulrich , Rehkämper Gerd
Published: April 2010

The U‐shaped alimentary tract of Cephalodiscus is of exclusively epithelial structure; on the basis of fine structural criteria the entire tract can be divided into two large subdivisions: an anterior one with mouth, mouth cavity, pharynx and oesophagus, and a posterior one with stomach and intestine. The anterior subdivision is built up of a relatively uniform, innervated, pseudostratified, ciliated epithelium with mucus cells which are concentrated in the initial parts of the mouth cavity. Cilia and mucus presumably constitute a mechanism transporting food particles into the stomach. In the area of the gill slits specific vacuolated cells occur which may lend rigidity to the walls of the slits. The gastric epithelium consists of prismatic cells characterized by, among others, large inclusion bodies, which may represent digestive vacuoles, small dense rod‐shaped granules and an elaborate system of microridges, at the base of which abundant endocytotic vesicles occur. The dorsal gastric pouch contains cells rich in rough ER and secretory granules, probably containing digestive enzymes. Thus morphological evidence points both to intra‐ and extracellular digestion. The intestinal epithelium resembles that of the stomach, however, it is lower, its organelles are fewer and it bears, beside cilia, mainly microridges, which towards its distal end become sparse. Both in the gastric and intestinal epithelium small granulated cells have been found, which presumably represent endocrine cells.
Insulin‐Like Immunoreactivity in the Neural Ganglion of the Ascidian Ciona intestinalis
Authors: O'Neil G. S. , Falkmer S. , Thorndyke M. C.
Published: April 2010

Antisera raised against salmon insulin and bovine insulin were used to assess the distribution of insulin‐like immunoreactive neurons in the neural ganglion of Ciona intestinalis. Cell bodies of two sizes were found in cortical and medullary positions, together with an extensive network of immunoreactive fibres. These observations indicate that an insulin‐like material is an important component of the central nervous system in Ciona and gives weight to the hypothesis that protochordates utilize insulin‐like factors as neurotransmitters or modulators, as do their invertebrate ancestors.
The Nervous System of Early Larval Stages of the Cestode Diphyllobothrium dendriticum
Authors: Wikgren Marianne C.
Published: April 2010

The nervous system (NS) of the coracidium and procercoid larval stages of the pseudophyllidean cestode Diphyllobothrium dendriticum was examined by whole mount immunocytochemistry and electron microscopy. Antisera against the bioamine serotonin and the molluscan cardioexcitatory peptide FMRF‐amide gave a positive immunoreaction in the NS of the procercoid. Ultrastructurally, three types of nervous elements were discerned. Ultrastructural evidence of both aminergic and peptidergic neurons in the coracidium is provided. The NS of these early larval stages is simply organized. The serotonergic part of the NS shows a beginning centralization in the procercoid, while the peptidergic neurons are more peripherally distributed.
In vivo Observations on a Specialized Microvasculature, the Primary and Secondary Vessels in Fishes
Authors: Steffensen J. F. , Lomholt J. P. , Vogel W. O. P.
Published: April 2010

Microscopical observations have been made on the blood circulation of intact, unanaesthetized specimens of the transparent glass catfish. Along the segmental arteries of the trunk, groups of short, curled vessels of capillary dimensions (termed inter‐arterial anastomoses) branch off and reunite to form large so‐called secondary arteries running parallel to the main (primary) arteries. Secondary arteries give rise to capillaries in the median ventral fin membrane. Secondary capilaries are drained via separate secondary veins. When blood passes from primary to secondary arteries via the inter‐arterial anastomoses a pronounced plasma skimming is observed. Hence, blood perfusing the secondary capillaries of the fin membrane contains very few red blood cells.
A Rostral Sensory Mechanism in Oikopleura dioica (Appendicularia)
Authors: Bollner Tomas , Holmberg Kaj , Olsson Ragnar
Published: April 2010

The ventral sense organ, below the mouth, is composed of 30 primary sensory cells situated in a row perpendicular to the long axis of the animal. Each cell carries one long and slender, modified cilium which arises from an apical pocket in the cell. The sensory cells project 15 axons at each side of the pharynx to the brain, which is rostrally paired and terminates in bulb‐like swellings. Each of these bulbs contains four cell bodies, which, according to their fine structure, as well as the synaptic connections with receptor and brain fibers, belong to three different types. It is suggested that the sense organ is a chemosensor and that its remarkable similarity to the vertebrate mechanisms for olfaction makes it probable that the appendicularian Oikopleura dioica possesses a ‘protochordate’ counterpart to the craniate olfactory apparatus.
Ultrastructural Observations on the Spermatozoa of Two Temnocephalids (Platyhelminthes)
Authors: Justine Jean‐Lou , de León Rodrigo Ponce , Mattei Xavier
Published: April 2010

The spermatozoa of two Temnocephalidae collected in Uruguay,Temnocephala iheringiHaswell, 1893 (Host:Pomacea canaliculata) andTemnocephala axenosMonticelli, 1899 (Host:Parastacus varicosus), were studied with a transmission electron microscope. In both species the spermatozoon is made up of a long sperm body which bears at one extremity two free flagella of the 9+‘1’ flatworm pattern. The sperm body contains the nucleus, mitochondria, dense bodies and parallel, cortical, longitudinal singlet microtubules. Along a part of the sperm body the palissade of the microtubules displays a spiral pattern in transverse sections. A part of the perimeter of the cell is thus lined by two overlapping rows of microtubules. This spiral pattern of the singlets is considered as a synapomorphy of the family Temnocephalidae. The singlet microtubules are interconnected by two kinds of links: tangential links between neighbouring singlets in the same row and radial links between singlets belonging to two rows. The presence of these links suggests that this structure could be a motile system of singlets.
Allocation of Matter in the Body of Growing Toads, Bufo bufo: Components of ‘Condition’
Authors: Jørgensen C. Barker , Wind‐Larsen H.
Published: April 2010

The condition, CI = [body mass (g)/length (cm)3]‐1000, tends to increase in toads growing in the laboratory on a diet of meal‐worms. The allocation was therefore studied of ingested food to growth corresponding to maintenance of standard condition (ΔWS) and to increases in condition, expressing bulky growth. A condition index of 100, typical of toad populations, is chosen to characterize standard growth, higher values expressing bulky growth. The relationship between mass specific standard growth (ΔWs/W0) and actual growth in mass (ΔW/W0) was the same in controls and growth hormone‐treated toads and was independent of sex and season. It could be described by the allometric equation ΔWs/W0 = 0.28 (ΔW/W0)1.36, r = 0.93. The composition of mass representing increases in bulk in excess of a CI = 100 was assessed from allometric relationships established between the indices of the chemical constituents and the overall condition index. The increases in condition were partitioned among the organs and parts of the body from allometric relationships established between indices of organs and body parts and the overall condition index. Treatment with growth hormone enhanced growth in mass and significantly increased the relative proportion of mass allocated to standard growth. However, the effect was not specific to growth hormone, but was an indirect effect of the increased growth rate. Water was the predominant constituent of the growth in bulk, amounting to about 70% of increases in CI. Fat and protein contributed about equally initially, 5–10%, with fat strongly increasing and protein slightly decreasing with increasing condition, fat to approach 20–30% when CI approached 200. Increases in water content largely reflected increases in volume of blood and lymph.
The Role of Ligaments in Arm Extension in Feather Stars (Echinodermata: Crinoidea)
Authors: Grimmer John C. , Holland Nicholas D.
Published: April 2010

It has long been thought that feather star arms flex due to muscular contraction and extend due to an opposing elastic force supplied by the ligaments, however, in 1985, Candia Carnivali and Saita (J. Morph. 185, 59–74) proposed that extension was due not to elastic ligaments, but to hydraulic pressure within the coelomic canals of the arm. We tested this new proposal experimentally by destroying the coelomic canals along the proximal halves of all ten arms of a feather star and then inducing it to swim. The wave form of the swimming arms was recorded on cine film for frame analysis. While the animal was swimming even the arm regions without coelomic canals were able to extend vigorously. Therefore, hydraulic pressure in the coeloms is not required for arm extension in feather stars. Our results are consistent with the classical idea that elastic ligaments extend the arms of crinoids.
Ultrastructure of the Protonephridium in Acteonemertes bathamae Pantin (Rhynchocoela: Enopla: Hoplonemertini)
Authors: Jespersen Åse
Published: April 2010

The protonephridial system consists of terminal cell, protonephridial capillary, protonephridial tubule and efferent duct. The terminal cell is an elongated, thin‐walled, fenestrated basket containing a ciliary flame circumscribed by a palisade of straight microvilli. The filtration area is confined to the terminal cell and consists of slits bridged by a filtration membrane. The cilia, as well as the microvilli, projects into the proximal bell‐shaped part of the thin‐walled protonephridial capillary. The terminal cells are often found in pairs connected to the same capillary, which has a very narrow lumen. The proximal part of the thick‐walled, convoluted protonephridial tubule is ciliated and shows characteristic foldings of the luminal plasma membrane and numerous small vesicles in the cytoplasm. The cells of the following, non‐ciliated part of the tubule have interdigitating lateral surfaces and the bases deeply invaginated to form compartments with numerous mitochondria; in the cytoplasm are many large vesicles, possibly containing lipid droplets, and small amounts of glycogen. The distal protonephridial tubule resembles various epithelia with an osmoregulatory function, including the vertebrate nephron.
Ultrastructural Observations on the Larva of Loxosoma pectinaricola Franzén (Entoprocta, Loxosomatidae)
Authors: Sensenbaugh Terry
Published: April 2010

The larva of Loxosoma pectinaricola Franzén has been studied using scanning and transmission electron microscopy. The embryo develops surrounded by an egg envelope attached to the brood chamber. The newly released larva measures about 100 μm in length and is characterized by a prominent apical organ, stalked vesicles, paired lateral sense organs and a prototroch. The apical organ consists of at least four cell types: (1, 2) two types of ciliated cells, (3) vacuolated cells and (4) myoepithelial cells. The apical organ and frontal ganglion are tightly juxtaposed in the upper tier of the episphere. The stalked vesicles each consisting of two cells are unique evaginations of the epidermis. There are about twenty stalked vesicles with a maximum diameter of about 20.0 μm. The ciliated, knob‐shaped, paired lateral sense organs are situated fronto‐laterally on the episphere. The prototroch is comprised of a row of contiguous prototroch cells each containing about eighteen long cilia. The apical organ, frontal ganglion and paired lateral sense organs are suggested to be sensory structures that play an important role in active locomotion, settlement site selection and metamorphosis.
Extracellular Matrix in Platyhelminths, with Special Reference to the Presence of Fibronectin
Authors: Lindroos Paula , Wikgren Marianne
Published: April 2010

The extracellular matrix (ECM) was studied in the turbellarians Polycelis nigra and Microstomum lineare, the cestode Diphyllobothrium dendriticum and the trematode Dicrocoelium dendriticum. Routine LM staining methods for connective tissue gave positive results only in P. nigra. Positive staining reactions were observed in the subepithelial basal lamina, around the pharynx and as strings in the tissues. Peroxidase‐anti‐peroxidase and immunofluorescence methods were used to identify fibronectin. Positive results were obtained in all species. Positive reactivity to anti‐fibronectin was observed in the subepithelial basal lamina and as a thin network between the cells of the tissues. Some intracellular reactivity occurred, but the cell type was not identified. In M. lineare a strong positive reactivity was observed in the regenerating area.
An Ultrastructural and Immunocytochemical Study of Gastrodermal Cell Types in Microstomum lineare (Turbellaria, Macrostomida)
Authors: Reuter Maria , Palmberg Irmeli
Published: April 2010

The gastrodermal cell types of Microstomum lineare (Turbellaria, Macrostomida) were studied by electron microscopy. Their immunoreactivity (IR) to bovine pancreatic peptide (BPP), FMRF‐amide and vasotocin, somatostatin, neurotensin, ACTH, CCK, bombesin, secretin, gastrin/CCK and insulin antisera was tested by light microscopic immunocytochemical methods. In addition to granular club cells and phagocytic cells, neurons and neoblasts occur in the gastroderm of this turbellarian species. This is the first observation of neurons in the gastroderm of a flatworm. Dense‐core vesicles (70–100 nm diameter), electron lucent cytoplasm and numerous Golgi complexes characterize the neurons. Unpolarized two‐way synapses, neuromuscular junctions and polarized chemical synapses can be observed in the gastroderm. Neoblasts with large nuclei and scanty cytoplasm and differentiating cells containing clusters of basal bodies occur next to the basal lamina of the gastroderm. BPP‐like, FMRF‐amide‐like and vasotocin‐like immunoreactivity is demonstrated in the gastroderm. Both BPP and FMRF‐amide IR is restricted to the basal cytoplasm of the granular club cells, while a different location for IR to vasotocin antiserum is observed. The status of the neuronal cell in the gastroderm of M. lineare is discussed in relation to endocrine (paracrine) cells and neurons in the gastroderm of invertebrates.
Protonephridial organs in Myzostoma cirriferum (Myzostomida)
Authors: Pietsch Arnold , Westheide Wilfried
Published: April 2010

Myzostoma cirriferum Leuckart, 1836 possesses five paired, serially arranged, blindending nephridial organs which are described for the first time. Ultrastructural investigations reveal that each nephridium is composed of three terminal cells and one tubular cell that forms the emission tubule. The central lumen of the individual terminal cells contains six to nine flagella, each of which is surrounded regularly by cytoplasmic rods arranged in parallel. Weir‐like fenestrations in the peripheral wall of the terminal cells make up the connection between the central lumina and the extracellular space around the nephridial organ. The canal of the emission tubule possesses cilia, microvilli and cytoplasmic structures, suggesting involvement of this cell with active transport and storage. It opens into the cuticle at the ventral surface of the animal.
Structure and Function of Metazoan Ciliary Bands and Their Phylogenetic Significance
Authors: Nielsen Claus
Published: April 2010

Ciliated epithelia, especially the ciliary bands used in swimming and filter feeding, of representatives of the following phyla have been investigated: Porifera, Cnidaria, Annelida, Mollusca, Sipuncula, Nemertini, Platyhelminthes, Entoprocta, Ectoprocta, Rotifera, Pterobranchia, Phoronida, Brachiopoda, Echinodermata and Enteropneusta. The trochaea theory predicts that Porifera and Cnidaria have only monociliate cells and lack ciliary bands used in filter‐feeding, that the gastroneuralian larvae have downstream‐collecting ciliary bands with prototroch and metatroch of compound cilia on multiciliate cells, and that notoneuralian larvae have an upstream‐collecting neotroch on monociliate cells. The observations generally fit these predictions and the exceptions are discussed. In all the ciliated epithelia, except that of the sponge larva, each ciliated cell has an accessory centriole perpendicular to the basal body of the cilium and situated on its downstream side.
Fine Structure and Function of Pharynx Cilia in Glossobalanus minutus Kowalewsky (Enteropneusta)
Authors: Pardos Fernando
Published: April 2010

Two kinds of cilia have been observed in the pharynx of Glossobalanus minutus Kowalewsky. From the present study, a ciliary specialization can be found in order to move a determinate substance, i.e. mucus or water. Mucus‐moving cilia (type I cilia) have a single basal centriole and poorly developed ciliary rootlets. Their tips are rounded, bearing an inner, asymmetrical cap attached to some tubules. Water‐moving cilia (type II cilia) are exclusively located at lateral epithelia of branchial bars, giving rise to the water current through the gills. They have two basal centrioles, proximal and distal, and a complex system of ciliary rootlets made up of a principal rootlet, a secondary or accessory rootlet and a ‘fan’ rootlet. The tips of type II cilia have a long process with some tubules inside. All basal structures are precisely orientated in order to assure a good coordination of ciliary beat. The possible functional significance of ciliary substructure is also discussed. From these observations a model for mucus and water currents through gill slits is postulated.
Immunocytochemical Evidence of Neuroactive Substances in Flatworms of Different Taxa—a Comparison
Authors: Reuter Maria , Lehtonen Marjut , Wikgren Marianne
Published: April 2010

Immunoreactions (IR) in the nervous systems (NS) of species representing the platyhelminthic taxa Acoela, Proseriata, Tricladida and Rhabdocoela (Dalyellioida, Typhloplanoida, Kalyptorynchia) have been studied by means of the peroxidase‐antiperoxidase (PAP) immunocytochemical method and the whole mount immunofluorescence (FITC) method. Antisera to the molluscan cardioactive neuropeptide FMRF‐amide, to the bioamine 5‐HT and to the vertebrate neuropeptides bovine pancreatic peptide (BPP), leu‐enkephalin, substance P and human growth hormone releasing factor (GRF) were used. Perikarya and fibres positive to FMRF‐amide antiserum (anti‐FMRF‐amide) appear in the NS of all investigated species. Since IR to anti‐FMRF‐amide has been obtained in worms representing taxa of all flatworm classes it is suggested that substances with similar sequences have been inherited from the stem form of Platyhelminthes. IR to 5‐HT antiserum (anti‐5‐HT) observed in the NS of all the investigated flatworms confirm the importance of this bioamine, which may have appeared early in platyhelminth evolution. IR to GRF antiserum was found in the acoel, the triclad and the rhabdocoel species, IR to leu‐enkephalin antiserum in the triclad and rhabdocoel species and IR to substance P antiserum in the rhabdocoels.
The Morphology of the Organum Olfactus of a 32 mm Embryo of the Brachiopterygian Fish Polypterus senegalus
Authors: Bjerring Hans C.
Published: April 2010

Anatomically the brachiopterygian organum olfactus is unique among craniates. As revealed by the present study of Polypterus senegalus, it consists of an incurrent and an excurrent tube, a body and six lobes. Luminally these divisions are extensively covered with cilia, the actions of which cause water to flow through the organ. The proximal extremities of the two tubes communicate directly with one another, allowing water to bypass the body and the lobes. The body is subdivided by means of seven infolds into a central part and two peripheral parts. Of these, the central part directs water to the lobes; the peripheral parts drain the lobes and lead water to the excurrent tube. Each lobe has an axial portion and two rows of alternating lobuli. Interlobularly infolds of the axial portion subdivide the lobar lumen in such a way that movement of water is possible. Olfactory neurosensory cells occur in the rear of the incurrent tube, as well as in the lobes. Probably the degree of stimulation of the tubal receptors determines whether the water taken in is to bypass the lobes.
Distribution and Structure of the Adrenocortical Homolog in the Reed‐Fish (Calamoichthys calabaricus Smith)
Authors: Youson J. H. , Butler D. G. , Bawks B. A.
Published: April 2010

The adrenocortical homolog (AH) was identified in the reed‐fish (Calamoichthys calabaricus Smith) using histochemistry for the enzyme δ5‐3β‐hydroxysteroid dehydrogenase (3β‐HSD) and its distribution and structure were examined with both light and electron microscopy. AH appears as yellow corpuscles which extend as isolated bodies throughout the length of both kidneys in close apposition to the posterior cardinal veins. The yellow corpuscles are composed of convoluted cords of epithelial cells and tortuous sinusoids which empty directly into the cardinal veins. Wide lateral intercellular spaces and accompanying microvilli give the impression of pseudotubules or pseudofollicles to the cords of epithelial cells. The extensive network of tubules of smooth endoplasmic reticulum, the many mitchondria with tubulo‐vesicular cristae, the conspicuous Golgi apparatus, lipid droplets, many pleomorphic granules and the presence of 3β‐HSD are indicative of the steroidogenic nature of the cells. Large, pleomorphic mitochondria and gap junctions are also typical of most cells. The fine structure of the cells in the AH of the reed‐fish most closely resembles that of other Polypteriformes, but the tissue is more widely distributed in the kidneys than in any osteichthylian so far reported.
The Number and Distribution of Calyceal Hair Cells in the Inner Ear Utricular Macula of Some Reptiles
Authors: Jørgensen J. Mørup
Published: April 2010

The utricular macula in the inner ear was examined in two turtle, two lacertilian, two snake and one crocodilian species. The orientation of hair cells was found to be similar to the general pattern for this macula described previously from fish to mammals. The calyceal hair cells, characterized by their embracing afferent nerve endings, are distributed in a single belt running parallel with the anterior and lateral borders of the macula in the examined reptiles.

The number of hair cells in a large number of calyces was counted for some of the examined reptile species, and the total number of hair cells calculated in two specimens of a turtle, crocodile and snake utricular macula. In the turtle and snake maculae, the calyceal hair cells form about 10% of the total hair cell number, while the crocodiles, which were very young, only had 2% calyceal hair cells. The total number of hair cells was found to be much higher in the crocodiles than in the other reptiles examined. The presented data, as well as data from the literature of the avian and mammalian inner ear, indicate that the number of this very sensitive hair cell type in the utricular macula is independent of locomotion type.
Organization of the Nervous System and Sensory Organs in the Larva of the Marine Bryozoan Bowerbankia gracilis (Ctenostomata: Vesiculariidae): Functional Significance of the Apical Disc and Pyriform Organ
Authors: Reed Christopher G.
Published: April 2010

The organization of the nervous system and the histology and ultrastructure of the apical disc and the pyriform organ have been investigated by serial sections with light and electron microscopy for the larva of the vesiculariid ctenostome bryozoan Bowerbankia gracilis Leidy 1855. The nervous system consists of four major internal components: (1) a median‐anterior nerve nodule; (2) an equatorial, subcoronal nerve ring; (3) paired aboral nerve cords; (4) paired antero‐lateral nerve tracts. The nervous system is associated with the ciliated larval surface at the apical disc, the pyriform organ, the corona and the intercoronal cells. The paired aboral nerve cords extend from the apical disc to the nerve nodule, which gives rise to the paired antero‐lateral nerve tracts to the pyriform organ and to paired lateral tracts that form the equatorial nerve ring. Ultrastructural evidence is provided for the designation of primary sensory cells in the neural plate of the apical disc and in the juxtapapillary regions of the pyriform organ. Efferent synapses are described between the equatorial nerve ring and the overlying coronal cells, which constitute the primary locomotory organ of the larva. The repertoire of potential functions of the apical disc and pyriform organ are discussed. It is concluded that the apical disc and pyriform organ constitute larval sensory organs involved in orientation and substrate selection, respectively. Their association with the major effector organs of the larva (the corona and the musculature) via the nervous system supports this interpretation.
An Ultrastructural Study of the Spermatozoa from Prionospio cf. queenslandica and Tripolydora sp.: Two Spionid Polychaetes with Different Reproductive Methods
Authors: Rouse G. W.
Published: April 2010

The fine structure of the spermatozoa of two spionids is described. The spermatozoon of Prionospio cf. queenslandica is typical of an animal utilizing external fertilization, in having a subspheroidal nucleus, a midpiece composed of unmodified rounded mitochondria surrounding two centrioles and a free flagellum. The acrosome is unusual in showing bilateral symmetry. The spermatozoon of Tripolydora sp. resembles that of spionids utilizing spermatophores, in possessing an extremely elongate nucleus and midpiece. The nucleus is penetrated by the 9+2 axoneme for its entire length, linking with a single centriole at the anterior end. Platelets surround the nucleus and intermingle with the mitochondria of the midpiece, which terminates with an annulus. The acrosome shows some internal vesiculation and substructuring. Sperm structure in relation to reproductive methods is discussed and the view of external fertilization as primitive is questioned.
Ultrastructural Study of the Evolution of Globules in Coronet Cells of the Saccus Vasculosus of an Elasmobranch (Scyliorhinus canicula L.), with some Observations on Cerebrospinal Fluid‐Contacting Neurons
Authors: Rodriguez‐Moldes M. Isabel , Anadón Ramón
Published: April 2010

The luminal surface of the coronet cells of the dogfish saccus vasculosus has been studied by scanning and transmission electron microscopy. Most of these cells have a mulberrylike structure composed of 25–35 closely arranged globules originated from ciliary stalks. In adult dogfish some coronet cells have globules either shedding or in different phases of formation from cilia. We report here the description of dogfish coronet cells and the discussion on a putative globule formation cycle. Cerebrospinal fluid (CSF) contacting neurons of the dogfish saccus vasculosus were also described.
Putatively luminous tissue in the abdominal pouch of a male dalatiine shark, Euprotomicroides zantedeschia Hulley & Penrith, 1966
Authors: Munk Ole , Jørgensen Jørgen Mørup
Published: April 2010

The putatively luminous villous tissue in an abdominal pouch of a male specimen of the oceanic midwater shark Euprotomicroides zantedeschia is described. The epithelium within the pouch is probably stratified. The most conspicuous cell type is tall columnar cells, typically containing small cytoplasmic granules and a large inclusion. Cells with similar cytoplasmic characteristics, thought to be photogenic cells, are present in the epidermal skin photophores in other selachians which are known to be luminous.
Primary Culture of the Mouse Subcommissural Organ In Vitro*
Authors: Lehmann Werner , Sterba Günther , Wobus Anna M.
Published: April 2010

Explants of adult mouse subcommissural organs were subjected to primary tissue culture on a feeder layer prepared from mouse embryonic fibroblasts. The explants quickly anchored and developed into three tissue types: (i) cystic explants. (ii) solid explants, and (iii) subcolonies. Secretory material was localized immunocytochemically in all of these three types of specimens. Electron microscopical investigations support the idea that a discharge of secretory material takes place into the culture medium.
The Protonephridia of the Arctic Kinorhynch Echinoderes aquilonius (Cyclorhagida, Echinoderidae)
Authors: Kristensen Reinhardt Møbjerg , Hay‐Schmidt Anders
Published: April 2010

The cyclorhagid kinorhynch Echinoderes aquilonius Higgins & Kristensen, 1988 possesses a single pair of protonephridia located in segments 10 and 11. The protonephridia consist of: (1) three terminal cells T‐1, T‐2. T‐3, each with two cilia; (2) a single non‐ciliated canal cell; (3) a nephridiopore cell with many microvilli and a cuticular sieve plate.

The protonephridia of Echinoderes are presumed to develop from the ectoderm near the area of the sieve plate on the eleventh segment, and are suspended in the dorso‐lateral pseudocoelomic cavity where they are surrounded by a basal lamina. One of the terminal cells (T‐1) secondarily penetrates the basal lamina of the tenth segment and a part of the cell attaches to the cuticle. The kinorhynch protonephridia are compared with the excretory organs of other Bilateria. expecially the ‘aschelminths’, and apomorphic characters of the kinorhynch protonephridia are defined.
Fine Structure of the Labial Gland in Macrotermes bellicosus (Isoptera, Termitidae)
Authors: Billen J. , Joye L. , Leuthold R. H.
Published: April 2010

The labial gland in M. bellicosus corresponds with the acinar type, and occupies the greater part of meso‐ and metathorax. The acini comprise three secretory cell types, in addition to the central ductule cells and the epithelial cells that make up the efferent ducts. Cell types are mainly distinguished by the size and appearance of their secretory vesicles and the extent of the microvillar contact area with the ductule cells. They probably produce a proteinaceous secretion that may contain digestive enzymes. The labial gland acini in soldiers, on the other hand, contain only one type of secretory cell, which is not comparable with any of the cell types in the worker caste. This difference is in agreement with the multifunctional role of the labial gland according to the termites' polyethism.
The Oral Papilla of the Lancelet Larva (Branchiostoma lanceolatum) (Cephalochordata)
Authors: Andersson Eva , Olsson Ragnar
Published: April 2010

The oral papilla is a prominent larval organ in the lancelet, which develops early during ontogenesis and disappears completely at metamorphosis. Electron microscopic studies indicated that the prevailing theories of its function are unlikely. Its cells lack the cytological characteristics of sensory or mucus producing cells, and the organ is not equipped with a tuft of flagella. It was not possible to reveal the function of the papilla, but its cells seem to be involved in a pronounced substance transport through the basal cell membrane as well as in the cytoplasm. Apical specializations indicate exo‐ or endocytotic activity and vesicles imply some exchange also between papilla cells and the sea water.
Sperm Structure in the Psocoptera
Authors: King P. E. , Ahmed K. S.
Published: April 2010

An account is given of the ultrastructure of the sperm in Psocoptera. Three main types of sperm occur. Type one, in Suborder Trogiomorpha, is an uncoiled long sperm with a filamentous head and a flagellum containing two or three lateral ridges and two central tubules. Twenty three per cent of this type has two axonemes and four mitochondrial derivatives. The second type, in the Suborder Psocomorpha, lacks both central tubules and lateral ridges. Four per cent of this type contain biaxonemes and four mitochondrial derivatives. In the third type, in the Suborder Troctomorpha. 100% of the sperm have two axonemes and two mitochondrial derivatives. The possible function and the method of locomotion of these types are described. The similarity between sperm structure in the Psocoptera and in Anoplura and Mallophaga suggests a close phylogenetic relationship between the three orders.
Apertures of Craniate offactory Organs
Authors: Bjerring Hans C.
Published: April 2010

The olfactory organs of craniates appear to derive from an anterior pair of erstwhile branchiothyria and their adjacent epidermal, neurogenic placodes. The organ is termed saccus nasalis if its source is the ectobranchial invagination of the branchiothyrium, and the saccus rhinalis if its source is the entobranchial evagination of the branchiothyrium. Nasal sacs occur in gnathostomes and lampreys, and rhinal sacs in hagfish. It is difficult, therefore, to avoid the conclusion that the olfactory organ has evolved more than once. The rhinal sac has only one aperture, the postica, which represents an internal branchiothyric orifice. Partial fusion of the right and the left rhinal sac led to the development of a postica communis. The nasal sac has either one, two or three apertures. Altogether there are nine different aperturae sacci nasalis, viz. the naris, the foris, the tremiscus, the two nariculae, the rimilla, the portula, the opiscus and the janua. The janua represents an external branchiothyric orifice and occurs in lampreys. The naris and the foris arose by subdivision of the orifice from which the janua emanated; they are found in osteolepipods. The naris is also found in urodeles, porolepiforms and some teleosts. The incurrent and excurrent naricules resulted from bipartition of a naris and are present in actinopterygians, coelacanthiforms, brachiopterygians, dipnoans and elasmobranchiomorphs. Of the four remaining openings of the nasal sacs the rimilla results from an inpushing of the epidermis, the portula from an outpocketing of the nasal sac, and the tremiscus from a combination of two such movements, the one inward and the other outward. Rimillae occur in cyprinodonts, anurans, urodeles, caecilians and porolepiforms, portulae in uranoscopids and bathydraconids, and tremisci in urodeles and porolepiforms. The opiscus, finally, is the opening through which the vomeronasal organ communicates with the oral cavity. It occurs in most lizards and snakes and probably also in some mammals.
Further Evidence that Synaptic and Synaptoid Vesicles Constitute a Single Category of Inclusions: Dense‐cored Synaptic and Synaptoid Vesicles in Helix Discharge their Contents by Exocytosis
Authors: Bayraktaroglu Emine , Golding D. W. , Whittle A. C.
Published: April 2010

In the pulmonate mollusc Helix, neurosecretory cells have perikarya that form neurohaemal complexes peripherally beneath the inner surface of the neural lamella and give rise to axons with varicosities in the neuropile. Two categories of secretory inclusions are present throughout the cytoplasm and these accumulate adjacent to sites of release. Secretory granules invariably have electron‐dense contents, whereas smaller vesicles have fairly lucent contents following fixation in OsO4, but are dense‐cored in material fixed initially with aldehyde. Vesicles (‘synaptic vesicles’) at central sites appear identical to those (‘synaptoid vesicles’) at peripheral, neurohaemal locations. At both neurohaemal and central sites, both granules and vesicles discharge their contents by exocytosis, this process being most clearly visualized in tissues treated with tannic acid.
On the Fine Structure of the Nervous System of Tubiluchus philippinensis (Tubiluchidae, Priapulida)
Authors: Rehkämper Gerd , Storch Volker , Alberti Gerd , Welsch Ulrich
Published: April 2010

At the mouth tube/introvert border a circumenteric intraepithelial nerve ring occupies a circular ridge protruding into the body cavity. The ring has a centrally located neuropile nearly free of perikarya and two zones of different perikarya above and below the neuropile.

Presumably non‐neuronal perikarya have an oval nucleus, large heterochromatin clumps and marked filament bundles. Such elements resemble tanycytic glial cells.

Two types of presumably neuronal perikarya contain small cytoplasmic granules, similar to those in nerve fibre profiles. One of these neurons has a pale nucleus with a prominent nucleolus, the other a rather inconspicuous nucleus similar to that of the tanycytic cells.

The neuronal processes of the fibre ring differ in diameter and contain clear and dense core vesicles, small granules (high or medium electron density) or granules with a dense periphery and a light centre. Sometimes neighbouring processes seem interconnected by electrical synapses. Images suggesting chemical synapses are rare.

A large intraepithelial nerve lies in the wall of the introvert and ventral body wall close to the musculature, possibly innervated by this nerve.

Frontal of the anus lies an intraepithelial ganglion demonstrating again a central neuropile. two neuronal types and tanycytic elements with filament bundles.

Comparative aspects of the characters of the Tubiluchus nervous system are also discussed.