bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparative studies on the eye morphology of lungless salamanders, family Plethodontidae, and the effect of miniaturization
Authors: Linke Rüdiger , Roth Gerhard , Rottluff Bernd
Published: February 2005

In seven species of lungless salamanders, family Plethodontidae, ranging from medium to very small in body size and from small to very large in cell size, the morphology of the eye and the retina were investigated. Haller's rule was only partially corroborated. While the smallest species had the relatively largest eyes, the largest two species, having the largest cells, showed the third and fourth largest eyes of the series. An effect of cell size was also found with regard to eye morphology. Small species with small cells as well as large species with large cells had relatively small retinae and relatively large lenses. In contrast, small eyes with relatively large cells had absolutely and relatively large retinae and relatively small lenses.

The retinae of all investigated plethodontids showed a morphology typical for land vertebrates with two fiber and three nuclear layers. Rods, cones and double cones could clearly be distinguished. A fovea or area centralis was not found. Retina ganglion cell and photoreceptor counts show that the number of these elements was lower than in salamandrids. However, determination of the resolution power of miniaturized eyes based on morphological and behavioral data shows that this does not seem to constitute a functional disadvantage. The morphological and functional properties and constraints of eyes of miniaturized salamanders are discussed.
Comparative morphology and evolution of cheek pouches in rodents
Authors: Ryan James M.
Published: February 2005

There are two types of cheek pouches in extant rodents. Internal cheek pouches are evaginations of the oral cavity deep to M. platysma and M. sphincter colli profundus, and have evolved independently in some species of the superfamilies Sciuroidea and Muroidea. External, furlined cheek pouches open lateral to and separate from the oral cavity, (also deep to M. platysma and M. sphincter colli profundus), and occur in all species of the families Geomyidae and Heteromyidae. The presence of external, furlined cheek pouches is a synapomorphy for the superfamily Geomyoidea.

The posterior retractor muscle of the pouch is derived from facial musculature in sciurids, from trapezius musculature in cricetids, and from both facial and trapezius muscle groups in the Geomyoidea. Differences also exist in the musculature associated with the pouch opening. In the Sciuridae and Cricetidae, the M. buccinatorius muscle group acts as a sphincter to control the size of the pouch opening. In the Geomyoidea, the size of the opening is controlled by the M. orbicularis sacculi in concert with a slip of the M. Platysma myoides.

Thin sections and scanning electron micrographs of the pouch tissue reveal the presence of dermal papillae in Phodopus sungorus but not in a close relative, Mesocricetus auratus. All members of the subfamily Cricetinae have a peninsula of highly folded tissue projecting anteriorly from the posteromedial pouch wall. This folding allows for expansion of the pouch walls when food is stored in the pouch.
Ultrastructural evidence of extruding exocytosis of residual bodies in the freshwater sponge Ephydatia fluviatilis
Authors: Willenz Philippe , van de Vyver Gysèle
Published: February 2005

Exocytosis of residual bodies by choanocytes, archeocytes and endopinacocytes lining the aquiferous system of Ephydatia fluviatilis has been demonstrated using calibrated latex beads and Escherichia coli as tracers. In passing into the mesohyl or the lumen of the exhalant aquiferous canals, beads, and altered bacteria were enveloped by the plasma membrane of the cell containing them. The membrane constricted at a neck region to form extruding vacuoles. This process appeared first in choanocytes and later in other cell types. The occurrence of these buds increased with the length of incubation time, as did the number of particles they contained. Acid phosphatase activity was frequently associated with the particles budding from the cell membrane, confirming that this process followed digestive activity.

Membranous vacuoles were recovered from the external medium and observed by TEM and those adhering to the substratum were seen by SEM. These observations proved that vacuoles were released from the sponges. This membrane‐consuming mechanism of exoctyosis implies intense membrane replacement in the digestive cells of the sponge.
Comparative aspects of cerebellar cytoarchitecture in the European eel life cycle
Authors: Bernocchi G. , Biggiogera M. , Barni S.
Published: February 2005

The major anatomical divisions of the cerebellum of the European eel, i.e., corpus cerebelli, lobus vestibulolateralis, and valvula, were studied morphologically and morphometrically. There were differences in cerebellar cytoarchitecture and gross morphology in two stages of the eel life cycle, the trophic stage (yellow eel), and the reproductive stage (silver eel), which are characterized by different degrees of swimming activity. The principal differences between silver and yellow eels in the cytoarchitecture of the corpus cerebelli and the lobus vestibulolateralis were in distribution of Purkinje or Purkinje‐like cells in the molecular layer, which is wider in silver eels, in part because of a decreased thickness of the granular cell layer. In the silver eel, the scattering of Purkinje cells was more evident in the lobus vestibulolateralis where the molecular layer is also thicker. The data indicate the transition from the yellow eel to the silver eel is characterized by a migration of granule cells from the ganglionic cell layer to the internal granular layer and by a further development of molecular layer components, e.g., parallel fibers, Purkinje‐cell dendrites, etc. In contrast, the thickness of the granular layer and of the Purkinje cell layer, limited to the lower part of the valvula, decreased. There is also a slight increase of cerebellar volume in the silver eel. The volume of the lobus vestibulolateralis was constant. Hypertrophy of the valvula and eminentiae granulares is observed and is due to the migration of cells from the granular layer of the corpus cerebelli whose volume slightly decreases. Perhaps the lobus vestibulolateralis also contributes to the increased volume of eminentiae granulares. Our findings suggest that the cerebellum continues to develop during the passage from the trophic to the reproductive stage of the eel. The appearance of new afferents from the lateral line which becomes more visible in the silver eel probably completes cerebellar ontogeny.
Lymph heart musculature in birds
Authors: Budras K.‐ D. , Hullinger R. L. , Rautenfeld D. Berens V.
Published: February 2005

Development and innervation of the lymph heart musculature of chicken, emu, rhea, and duck was studied by electron microscopy at posthatch ages from 3 days to adulthood. Development of innervation was monitored by acetylcholinesterase staining. Horseradish peroxidase was used to determine the extent of the transverse tubule network. Chickens were unusual among these birds in that lymph heart myocytes had already undergone a definitive differentiation and degeneration by 3 days. In ducks and ratite birds, lymph heart myocytes more slowly but progressively differentiate a cytomorphology that does not conform in all characteristics to cardiac or skeletal muscle and even resembles in some aspects, smooth muscle. Myofibrils become the dominant cytoplasmic structure, transverse tubules form ‘internal couplings’ with agranular reticulum cisternae, and ‘external couplings’ are formed between myocytes at myomyal junctions. The myomyal junctions also contain AChE‐positive reaction product and some subplasmalemmal vesicles that lack a dense core. The lymph heart myocardium of ducks of 2 weeks demonstrated mitotic figures. In adult ducks the myosatellite cell numbers diminish and a characteristic pattern of myocyte degeneration appears. In juvenile ducks and ratites some myocytes differentiate to conductile cells, much as the conductile myocytes and myofibers of the blood heart. The lymph heart innervation is described, and the role of nerve in differentiation and maintenance of myocyte morphology in the lymph heart is discussed.
Neuromast topography in anuran amphibians
Authors: Lannoo Michael J.
Published: February 2005

Generalized anuran tadpoles across families exhibit a similar neuromast morphology on their heads, as follows: (1) all neuromast lines known for anurans are present; (2) within these lines total neuromast number ranges from about 250 to 320; (3) neuromasts form linear stitches composed of two to three, but sometimes up to five, neuromasts; (4) neuromast linear dimensions are ⩽ 10 μm; and (5) neuromasts contain ⩽ 15 hair cells. Compared with generalized forms, stream, arboreal, carnivorous, and desert‐pond forms have fewer neuromasts but they contain more hair cells. They do not, however, form stitches. Obligate midwater suspension‐feeding forms, including Xenopus (Pipidae), Rhinophrynus (Rhinophyrnidae), and Phrynomerus (Microhylidae), form stitches that contain > six, but potentially up to 18 or more, loosely aggregated neuromasts. Xenopus and Rhinophrynus have large neuromasts (up to 40 μm across). Chiasmocleis (Microhylidae) tadpoles form stiches that are linearly arranged with up to ten neuromasts. Whereas urodeles can have more than one neuromast row per line and may form both linear and transverse stitches, anurans have only one row of neuromasts per line and form only transverse stitches. Neuromasts in anurans tend to be smaller and more circular than in urodeles and positioned flush with the epidermal surface. A greater percentage of anurans form stitches, and anurans have greater intrafamilial variation in stitch formation than do urodeles.
Regenerative response of amputated forelimbs of Xenopus laevis froglets to partial denervation
Authors: Liversage Richard A. , Anderson Meri‐Jo , Korneluk Robert G.
Published: February 2005

Xenopus laevis froglet forelimbs normally respond to amputational injury by forming a heteromorphic cartilaginous rod‐shaped outgrowth. However, partial denervation of a forelimb by ablation of the N. radialis or the N. ulnaris, followed in 2 days by amputation through the mid radius‐ulna, results in a size deficiency of the regenerative outgrowth 14 and 21 days postamputation. The decreasing quantity of forelimb innervation, as a result of partial denervation by 55 or 45%, apparently has a graded effect on the cell population and on the extent of cartilage development in the outgrowth. As a consequence of amputational injury, a nerve independent response of the periosteum was also found. This response produced considerable thickening in the periosteum and was due to cell proliferation in both the control and denervated cases.
A morphological study of the nervous system of the praesoma of Paulisentis fractus (Acanthocephala: Neoechinorhynchidae)
Authors: Gee Randall J.
Published: February 2005

The nerve pathways in the praesoma are described for a member of the class Eoacanthocephala for the first time. Eleven nerves, five paired and one single, are traced from the cerebral ganglion to their associations with the musculature of the body wall, neck sense organs, and the musculature of the proboscis wall and the invertor muscles of the proboscis. The structure and location of the stutzzelle and series of nerve endings in the hypodermis of the body wall and at the apex of the proboscis are described.
Structure and function of the spermatheca in a snail host of schistosomiasis, Biomphalaria glabrata
Authors: Rogers Steffen H. , Reeder Richard L.
Published: February 2005

The histochemistry and ultrastructure (SEM and TEM) of the spermatheca of Biomphalaria glabrata was investigated to elucidate the function of this organ and to compare its structure and function to similar organs found in other species. The spermatheca has a debris‐filled lumen surrounded by a thin wall of tissue. The cells adjacent to the lumen are of three columnar epithelial cell types. Two cell types have abundant microvilli and mammalian cell‐like organelle distribution and morphology. The above cell types differ in the electron density of their cytoplasms, nuclear morphologies, and organelle content. The third cell type differs from the other two in its cytoplasmic makeup. However, the most distinctive difference is the presence of large numbers of cilia at the apical surface with no evidence of microvilli. These columnar cells rest on a basal lamina adjacent to a two to three cell thick muscle layer. The entire organ is surrounded by an adventitia of unusual morphology. Histochemical investigation demonstrated that DNAase, RNAase, and protease are present in the lumen, alkaline phosphatase is associated primarily with the microvilli, small amounts of acid phosphatase are concentrated in the midcell area of the columnar epithelium, and ATPase activity is localized in the muscle cells and just below the absorptive surface of the microvillous cells. The luminal contents and adventitial areas are Sudan Black B positive, all areas of the lumen and organ wall are PAS positive, the cell nuclei and amorphous masses in the lumen showed Feulgen staining, and large vesicles in the columnar cells were Oil Red O positive. Apparently, the spermatheca of B. glabrata is both a digestive and absorptive structure. Although this organ shares functional similarities with those found in opisthobranchs and terrestrial pulmonates, the epithelia of the spermatheca differ dramatically in these groups.
Characterization of the form and growth pattern of colonies in several freshwater bryozoans
Authors: Mukai Hideo , Fukushima Mariko , Jinbo Yoshie
Published: February 2005

In all species of phylactolaemates, an individual successively produces daughter buds. Individual daughters are designated, according to the order of appearance, as first bud, second bud, and so on. The first bud appears precociously, while the mother is a pear‐shaped vesicle. The idea of regarding a main bud, a duplicate bud, and an adventitious bud as a set is not tenable. In the budding region, the cystidal wall shows a constant wavy movement. In Plumatella colonies, branching occurs only when and where a bud of the second or higher order grows up to a zooid. A branch is composed of longitudinally arranged first zooids with the only exception being the most proximal one. The proportion of first zooids in a colony increases in the order of P. casmiana, P. emarginata, and P. repens. The frequency of branching, therefore, decreases in this order. The ancestrula germinated from the statoblast shows the highest activity of budding. The tendency that successively produced daughters of the ancestrula grow in alternate directions is most conspicuous in P. emarginata and least conspicuous in P. casmiana. Replacement budding occurs in these three species of Plumatella, but only under unfavorable culture conditions. The colony of Gelatinella toanensis is characterized by composite branches, each consisting of an axial branch composed of a series of first zooids and of stunted lateral branchlets. In Hyalinella punctata, multiple budding does not necessarily result in branching; zooids of different budding orders coexist in a branch. The genus Pectinatella comprises two species, P. gelatinosa and P. magnifica. Both produce massive colonies. In P. gelatinosa, the colony proper is sac‐like with the convex basal wall, and the polypides can retract with the digestive tracts straight. Each individual (except the ancestrula) of this species produces a pair of daughter buds which are located bilaterally relative to the median sagittal plane of the mother. A left bud produces its first bud to the right, and vice versa. In P. magnifica, the colony proper is very thin and flat. When polypides are retracted, the digestive tracts are folded characteristically. Based on these and other results, phylogenetic relationships among the phylactolaemates are discussed.
Fine structure and histochemistry of the freshly extruded and hardened spermatophore of the spiny lobster, Panulirus interruptus
Authors: Martin Gary G. , Herzig Chris , Narimatsu Glen
Published: February 2005

Freshly extruded and hardened spermatophores of the spiny lobster, Panulirus interruptus, were compared using light and electron microscopy (EM). The spermatophore is composed of a sperm tube embedded in an acellular matrix. The sperm tube consists of tightly packed spherical cavities in an acellular material within which the sperm lie. The extruded spermatophore is white, soft, and sticky on all surfaces. The highly coiled sperm tube can be seen near the surface of the foot of the spermatophore, which is the side that will attach to the exoskeleton of the female. The opposite surface, the cap, will harden and darken after exposure to seawater. In the soft spermatophore, the matrix surrounding the sperm tube and extending from foot to cap is composed of small (2‐μm) granules embedded in a loose weave of filaments. In the hardened spermatophore, the matrix is composed of small (4‐μm) empty spheres. At the cap region the matrix darkens, and at the foot the granules dissolve to form a thick layer characterized by vertical striations. The structure of this spermatophore is compared to those spermatophores of other decapods that have been described at the EM level. The chemical composition and possible function(s) of the various components are discussed.
The spermatophore and its structural changes with time in the bursa copulatrix of the silkworm, Bombyx mori
Authors: Osanai Minoru , Kasuga Hiroko , Aigaki Toshiro
Published: February 2005

The bursa copulatrix of the silkmoth is filled with various secretions and seminal fluid transferred from the male reproductive system during mating. The contents of the bursa include a pearly body, spermatophragma, and spermatophore. The latter consists of a four‐layered wall, an inner and outer matrix, and a soft plug. The components of the spermatophore are all heterogeneous, since they are formed by the partially mixed, viscous streams of the male secretions. Apyrene spermatozoa and eupyrene bundles are present only in the inner matrix, but both the matrices are important sites of sperm maturation. After spermatophore formation, the basophilic regions and periodic acid‐Schiff (PAS)‐granules in both matrices gradually decrease with time. The PAS‐granules were identified as glycogen by α‐amylase treatment. The inner matrix containing sperm and the outer matrix decrease in volume and become concentrated near the neck of the spermatophore. Apyrene and eupyrene spermatozoa can move toward the ductus seminalis after their maturation. A large, beltlike space which does not stain remains at the periphery of the spermatophore. These structural changes of spermatophore contents seem to reflect metabolic reactions in the spermatophore as the reactor for sperm maturation.
Comparative study of the adrenergic innervation of the teleost gill
Authors: Donald John A.
Published: February 2005

The adrenergic innervation of structures in the gills of six teleost species was studied with catecholamine fluorescence histochemistry. The species studied were the following: sand flathead, Platycephalus bassensis and blue‐spot flathead Platycephalus caeuruleopunctatus (Platycephalidae); smooth toadfish, Tetractenos glaber (Tetraodontidae); Australian short‐finned eel, Anguilla australis (Anguillidae); river blackfish, Gadopsis marmoratus (Gadopsidae); and common carp Cyprinus carpio (Cyprinidae).

In all species except C. carpio fluorescent components were observed in the branchial nerves in the gill arch.

In the arterio‐arterial vascular pathway, the afferent and efferent branchial arteries were innervated only in Cyprinus. Fluorescent nerve fibres were found on afferent filamental arteries of all species except A. australis and on many afferent lamellar arterioles of all species except T. glaber. The secondary lamellae were devoid of fluorescent nerve fibres in all species. In Cyprinus and Anguilla, fluorescent nerve fibres were observed on occasional efferent lamellar arterioles. In Cyprinus, there was an additional innervation on the basal one‐third of the efferent filamental artery. The innervation of the arteriovenous vascular pathway was similar in all species. Fluorescent nerve fibres were found on nutritive arterioles, and in the core of each filament between the surface epithelium and the wall of the filament venous sinus.

Since most of the adrenergic innervation was found on afferent vessels of the arterio‐arterial pathway, it is suggested that adrenergic nerves and circulating catecholamines may have distinct functions in the regulation of blood flow through the gills.
Antennal sensory organs in the millipede Eurypauropus ornatus: Fine structure of the flagella and globulus
Authors: Tichy Harald
Published: February 2005

On the antennal tip of Eurypauropus ornatus are 3 threadlike sensilla—the flagella, and a single spheroid sensillum—the globulus. Each of the 3 flagella is innervated by 2 groups of sensory cells. One group contains 4 cells, the other, 5. All cells of the “four group” and 3 of the “five group” are comprised of single cilia and unbranched dendrites which extend along the lumen of the flagellum. Two cells of the “five group” have double cilia and pairs of unbranched dendrites. One pair also enters the flagellum and the other pair terminates beneath the flagellar base to form a concentric array of lamellae. No pores are present in the cuticular wall.

Eight sensory cells innervate the globulus. They are arranged in 3 groups, one triplet and 2 pairs, in addition to a single cell. The single cell contains a pair of cilia whose unbranched dendrites differentiate into tubular bodies that are inserted into the base of the globulus. Each of the other 7 sensory cells has a single cilium. Their unbranched dendrites penetrate into the globulus in 3 groups as described for the sensory cells. The dendrites in each group terminate in an individual pore channel at the globulus tip and completely fuse with the electron‐dense material that plugs the pore channel.

Based on structural similarities to sensilla having known functions, it is probable that the flagella and the globulus are chemoreceptors, the former responding to odors, the latter sensitive to substances in aqueous solution.
The development of acellularity of the vertebral bone of the Japanese medaka, Oryzias latipes (Teleostei; Cyprinidontidae)
Authors: Ekanayake Sunetra , Hall Brian K.
Published: February 2005

Among vertebrates, some teleosts are unique in having bone which lacks osteocytes embedded in the matrix. The fate of cells that secrete the matrix of these acellular bones has not been investigated thoroughly. Histological and fluorescent microscopic analysis of the vertebral bone of Oryzias latipes demonstrated that acellularity is not a secondary appearance of an early cellular bone during ontogeny. Vertebral bone is devoid of cells embedded in the matrix throughout development. Cells that secrete bone matrix do not become trapped in their own secretion. Instead, they always remain as a surface layer over the outer surface of the bone. Fluorescent microscopic visualization of tetracycline injected into growing fish demonstrated that bone was only deposited by osteoblasts lining the outer surface of the bone; no deposition of bone took place on the inner surface.
The morphology and vasculature of the lungs and gills of the soldier crab, Mictyris longicarpus
Authors: Farrelly Caroline , Greenaway Peter
Published: February 2005

The five gill pairs of Mictyris longicarpus have the lowest weight specific area reported for any crab. The cuticle of the gill lamellae is lined with epithelial cells which have structural features characteristic of iontransporting cells. Pillar cells are regularly distributed in the epithelium and serve to maintain separation of the two faces of the lamellae. The central hemolymph space is divided into two sheets by a fenestrated septum of connective tissue cells. The dorsal portion of the marginal canal of each lamella receives hemolymph from the afferent branchial vessel and distributes it to the lamella while the ventral portion of the canal collects hemolymph and returns it to the efferent branchial vessel.

The lung is formed from the inner lining of the branchiostegite and an outgrowth of this, the epibranchial membrane. Surface area is increased by invagination of the lining which forms branching, blind‐ending pores, giving the lung a spongy appearance. The cuticle lining the lung is thin and the underlyng epithelial cells are extremely attenuated, giving a total hemolymph/gas distance of 90–475 nm. Venous hemolymph is directed close to the gas exchange surface by specialised connective tissue cells and by thin strands of connective tissue which run parallel to the cuticle. Air sacs are anchored in position by paired pillar cells filled with microtubules. Afferent hemolymph is supplied from the eye sinus, dorsal sinus, and ventral sinus. Afferent vessels interdigitate closely with efferent vessels just beneath the respiratory membrane. The two systems are connected by a “perpendicular system” which ramifies between the airways and emerges to form a sinus beneath the carapace and then flows back between the air sacs to the efferent vessels. The afferent side of the perpendicular system is the major site of gas exchange. Efferent vessels return via large pulmonary veins to the pericardial cavity. PaO2 levels were high (95.5 Torr), indicating highly efficient gas exchange.
Changes in femoral robusticity and porosity during the reproductive cycle of the female alligator (Alligator mississippiensis)
Authors: Wink Carole S. , Elsey Ruth M. , Hill Elizabeth M.
Published: February 2005

To help understand the nature of skeletal changes during the reproductive cycle of the female alligator, we compared femoral robusticity (density) and porosity of cross‐sections from the midshafts of femora from the following groups of female alligators: (1) immature; (2) pre‐ovulatory; (3) postovulatory with soft‐shelled oviducal eggs; (4) post‐ovulatory with hard‐shelled oviducal eggs; (5) post‐ovulatory with eggs in the nest; (6) post‐ovulatory with hatched eggs; and (7) mature, quiescent. Femora from alligators with eggs in the nest were significantly less robust (dense) than those of the other groups except those with hard‐shelled oviducal eggs. Cross sections from the midshaft of femora from alligators with eggs in the nest were significantly more porous than those from all the other groups. The results indicated that calcium was mobilized from the femoral shaft shortly before eggs were laid and that femoral density returned to normal levels for mature alligators 1–2 months after egg‐laying.
Transformation of mucocartilage to a definitive cartilage during metamorphosis in the sea lamprey, Petromyzon marinus
Authors: Armstrong L. A. , Wright G. M. , Youson J. H.
Published: February 2005

An ultrastructural analysis of the development of adult piston (tongue) cartilage in the ventromedial longitudinal bar (VMLB), an area of larval mucocartilage, was undertaken in the lamprey, Petromyzon marinus, in order to clarify the relationship between these two unique larval and adult connective tissues. At the onset of metamorphosis, the mucocartilage fibroblasts dedifferentiate into a “mesenchymal” cell type. Migration of unspecialized cells from surrounding tissues plays an important role in the development of a cellular “embryonic” tissue in the VMLB. Degradation of the mucocartilage extracellular matrix (ECM) by the unspecialized cells seems to occur prior to cartilage differentiation. This event is followed by the appearance of a blastema of undifferentiated cells, which expands by proliferation of cells in the core of the VMLB. The cells of the blastema subsequently differentiate into chondroblasts, which secrete adult ECM components consisting of 20‐nm nonbanded fibrils, electron‐dense branched lamprin fibrils, and proteoglycan. The present study suggests that mucocartilage, as a primitive or embryonic connective tissue, temporarily specializes to act as a skeletal support during larval life. Once metamorphosis is initiated, this tissue resumes an embryonic character (mesenchymal) and cartilage histogenesis takes place. The mechanism of cartilage development within the lamprey VMLB is similar to that observed in the chondrogenic system of higher vertebrates.
Development and evolution of avian racket plumes: Fine structure and serial homology of the wire
Authors: Bleiweiss Robert
Published: February 2005

Avian racket plumes, characterized by a vaned paddle‐shaped tip borne on a wirelike segment, are among the most spectacular pennaceous contour feathers. This is the first detailed description of the fine structure of the wirelike segment in several racket plumes that acquire their shape exclusively during development, for the parrot Prioniturus discurus, the hummingbirds Ocreatus underwoodii and Loddigesia mirabilis, the kingfisher Tanysiptera carolinae, and the bird of paradise Parotia carolae. Scanning electron microscopy reveals that the wirelike segments are comprised of small, structurally simplified barbs located along a central rachis, indicating that racket plumes retain the basic structural organization of pennaceous contour feathers. The diverse structures provide evidence of several alterations to normal developmental processes, including arrested and disrupted development of the barbs. Many of the major differences among the five species in the fine structure of the wire apparently result from differences in the morphogenesis of barb ridges on the epidermal collar of the developing plume. The structure and morphogenesis of the racket plumes described herein are distinct from those described in motmots (Momotidae), indicating that racket plumes can evolve through convergence.
The ultrastructure and innervation of the ear of the gar, Lepisosteus osseus
Authors: Mathiesen Carsten , Popper Arthur N.
Published: February 2005

The endorgans of the inner ear of the gar were examined using transmission and scanning electron microscopy as well as nerve staining. The ultrastructure of the sensory hair cells and supporting cells of the gar ear are similar to cells in other bony fishes, whereas there are significant differences between the gar and other bony fishes in the orientations patterns of the sensory hair cells on the saccular and lagenar sensory epithelia.

The saccular sensory epithelium has two regions, a main region and a secondary region ventral to the main region. The ciliary bundles on the main region are divided into two groups, one oriented dorsally and the other ventrally. Furthermore, as a result of curvature of the saccular sensory epithelium, the dorsal and ventral ciliary bundles on the rostral portion of the epithelium are rotated ninety degrees and are thus oriented on the animal's rostro‐caudal axis. Hair cells on the secondary region are generally oriented ventrally.

The lagenar epithelium has three groups of sensory hair cells. The groups on the rostral and caudal ends of the macula are oriented dorsally, whereas the middle group is oriented ventrally. Hair cell orientations on the utricular epithelium and macula neglecta are similar to those in other bony fishes.

Nerve fiber diameters can be divided into three size classes, 1–8 μm, 9–13 μm, and 14 μm or more, with the smallest size class containing the majority of fibers. The distribution of the various classes of fiber diameters is not the same in nerve branches to each of the end organs. Similarly, the ratio of hair cells to axons differs in each end organ. The highest hair cell to axon ratio is in the utricle (23:1) and the smallest is in the macula neglecta (7:1). The number of sensory hair cells far exceed the number of eighth nerve axons in all sensory epithelia.
Intrinsic organization of the medial cerebral cortex of the lizard Lacerta pityusensis: A golgi study
Authors: Berbel P. J. , Martínez‐Guijarro F. J. , López‐García C.
Published: February 2005

The morphology of cells and the organization of axons were studied in Golgi‐Colonnier and toluidine blue stained preparations from the medial cerebral cortex of the lizard Lacerta pityusensis. In the medial cortex, six strata were distinguished between the superficial glial membrane and the ependyma. Strata I and II formed the outer plexiform layer, stratum III formed the cellular layer, and strata IV go VI the inner plexiform layer. The outer plexiform layer contained smooth bipolar neurons; their dendrites were oriented anteroposteriorly and their axons were directed towards the posterior zone of the brain. Five neuronal types were observed in the cellular layer. The spinous pyramidal neurons had well‐developed apical dendrites and poorly developed basal ones. Their axons entered the inner plexiform layer and gave off collaterals oriented anteroposteriorly. The small, sparsely spinous pyramidal neurons had poorly developed dendrites and their axons entered the inner plexiform layer. The spinous bitufted neurons had well‐developed apical and basal dendritic tufts. Their axons gave off collaterals that reached the outer and inner plexiform layers of both the dorsomedial and dorsal cortices. The sparsely spinous horizontal neurons had dendrites restricted to the outer plexiform layer. Their axons entered the inner plexiform layer. The sparsely spinous, multipolar neurons had their soma close to stratum IV and their axons entered the outer plexiform layer. In stratum V of the inner plexiform layer were large, spiny polymorphic neurons; they had dendrites with long spines, and their axons reached the cellular layer. On the basis of these results, we have subdivided the medial cortex into two subregions: the superficial region, which contains the neurons of the cellular layer and their dendritic domains, and the deep region, strata V and VI, which contains the large, spiny polymorphic neurons. The neurons in the medial cortex of these lizards resembles those in the area dentata of mammals. On this basis, the superficial region may be compared to the dentate gyrus and the deep region to the hilar region of the hippocampus of mammals.
Development of an avascular region (the stigma) in ovarian follicles of lizards (Anolis)
Authors: Jones Richard E. , Lopez Kristin H. , Summers Cliff H. , Austin Harriet B. , Rand Matt S.
Published: February 2005

The architecture of follicular blood vessels in the ovary of lizards (Anolis equestris and Anolis carolinensis) was studied by standard histology and also after vascular perfusion with an orange silicone‐rubber compound or with India ink. The theca of the follicular wall contains a netlike arrangement of anastomosing sinusoids, which increase in size as a follicle grows. An avascular stigma forms in very small, growing follicles when a portion of the follicular wall contacts the ovarian surface epithelium. Blood vessels then invade the theca except in the zone of contact. The diameter of the stigma is about 50% of follicular diameter, regardless of follicular size. Although the stigma of smaller follicles is avascular, that of vitellogenic follicles is hypovascular, i.e., a few vessels radiate into the stigma region. The antiangiogenic process involved in stigma formation may continue as the stigma enlarges. The development pattern of stigma formation found in Anolis is displayed by many other vertebrates.
Fine structure of the fungiform papilla in a ranid frog (Rana esculenta)
Authors: Gioglio Luciana , Rapuzzi G. , Dell'orbo C.
Published: February 2005

The freetop of the fungiform papilla shows a sensorial area about 100 μm in diameter, surrounded by a ring of ciliated cells. Externally to the ciliated cells, i.e., in the lateral wall, numerous large goblet cells can be seen devoid of their mucous content. The sensorial area is composed by three types of cells: mucous, supporting, and neuroepithelial cells. Mucous cells form the most superficial layer, while the cell bodies of the other two are deep, and from them basal and apical processes arise. The above mentioned cells are connected by desmosomes preferentially located between the mucous and the supporting cells, rather than between the supporting and the neuroepithelial cells. The lateral wall of the papilla is made up of a multilayered epithelium that comprises two types of cells: the first type contains electron‐dense granules and an abundant rough endoplasmic reticulum, the others are ciliated cells. In the connective axis of the papilla, numerous fenestrated capillaries with endothelial vesiculated cells and nerve fibers are found.
Arrangement of accessory cells and nematocytes bearing mastigophores in the tentacles of the cubozoan Chironex fleckeri
Authors: Rifkin J. F. , Endean R.
Published: February 2005

Nematocytes containing microbasic mastigophores are intimately associated with accessory cells in the epidermis of Chironex fleckeri. Large microbasic mastigophores may be surrounded by seven to nine such cells. Each accessory cell possesses an apical portion containing secretory droplets and a basal portion which carries a radially oriented fibre linking the cell to the underlying mesogloea. The fibre is capable of projecting and retracting the accessory cell. Junctional complexes occur between accessory cells and the apical regions of neighbouring mastigophores. Each nematocyte bearing a mastigophore contains a triggering apparatus consisting of a cnidocil surrounded by microvilli. This apparatus protrudes from an invagination in the apical region of the nematocyte and is exposed when the mastigophore is in the fire‐ready position. A basket of filaments which make contact with microvilli surrounds the apical end of the nematocyst like a collar. The basket is linked via fibrous bundles which envelop the mastigophore to radially oriented fibres basally. These fibres are capable of projecting and retracting the mastigophore and its associated triggering apparatus. Up to nine such fibres were observed to be associated with a single large microbasic mastigophore. Microtubules averaging 25 nm in diameter and linked via cross bridges to electrondense material were detected in the radial fibres of both nematocytes and accessory cells. Retraction of the accessory cells and projection of nematocytes result in mastigophores being brought to the firing line and in the exposure of the cnidocil apparatus.
Some aspects of segment formation and post‐placental development in Peripatus acacioi marcus and marcus (Onychophora)
Authors: Walker Muriel , Campiglia Sylvia
Published: February 2005

The surface morphology of the anterior‐to‐posterior sequence of segment formation in embryos of a viviparous neotropical onychophoran and aspects of post‐placental development seen using scanning electron microscopy are described. When all the segments have formed and the walking legs have completed their elongation, the body surface becomes covered with an embryonic cuticle that does not exhibit the hydrofuge properties seen in the adult cuticle. As soon as the walking legs have reached their full length, barbed projections are formed at their distal extremities. These projections are extensions of single cells and are covered by the embryonic cuticle. Transmission electron microscopy reveals that the cells at the distal ends of the legs and their projections have many pinocytotic vesicles at their surfaces. The cytoplasm of these cells and their projections is rich in mitochondria, rough endoplasmic reticulum, glycogen, and granules of storage material. There are minor differences in the surface morphology of the projections found at the ends of the walking legs in embryos of Peripatus acacioi and those of Peripatus biolleyi. The projections and the embryonic cuticle persist thoughout postplacental development. The role of the projections in the uptake of material by the embryo from the uterus is discussed and the possible phylogenetic significance of these projections is suggested.
Ultrastructure and silver‐staining analysis of spermatogenesis in the sea urchin Paracentrotus lividus (Echinodermata, Echinoidea)
Authors: Sousa Mario , Azevedo Carlos
Published: February 2005

Spermatogenesis of the sea urchin Paracentrotus lividus has been studied at the ultrastructural level after conventional staining of thin sections and after en bloc silver staining. Cytoplasmic dense bodies are present in all steps of spermatogenesis except in late spermatids and spermatozoa. These bodies are closely associated with the development of centrioles and of the acrosomal vesicle during spermiogenesis. After it first appears, acrosomal vesicle is linked to the nuclear envelope by electron‐dense material and subsequently acquires a dense core. Later the acrosomal vesicle moves to the apical pole of the cell while maintaining its connection to the nucleus. Although chromatin was highly condensed in the head of spermatozoa, one or more nuclear vacuoles within the nucleus were found to contain uncondensed chromatin fibers. Silver nitrate stains several nuclear and cytoplasmic structures. In the nucleus it stains the nucleolus, specific regions at the periphery of the chromatin, the synaptonemal complexes, the nuclear basal fossa, and the nuclear vacuoles of spermatozoa. In the cytoplasm, silver stains the cytoplasmic dense bodies, the material that connects the acrosomal vesicle to the spermatid nucleus, the spermatozoan subacrosomal and periacrosomal materials, the intercellular bridges of spermatids, and the centrioles. Silver staining is abolished by pretreatment with pronase E, suggesting that silver staining is due to protein.
Atavisms and the homology of hyobranchial elements in lower vertebrates
Authors: Reilly Stephen M. , Lauder George V.
Published: February 2005

The homology of branchial arch segments in salamanders has been a matter of controversy since the last century. Many investigators term the most medial paired elements of salamander branchial arches “ceratobranchials” and the next distal paired elements “epibranchials.” This suggests that the first two segmental elements of the salamander branchial arch are not homologous with elements occupying the same position in ray‐finned fishes, Latimeria, “rhipidistians,” and lungfishes, in which these bones are called hypobranchials and ceratobranchials, respectively. Three lines of evidence suggest that it is more parsimonious to interpret urodele branchial arch segments as being homologous with those of other vertebrate clades−(1) comparative osteology, (2) comparative myology, and (3) the discovery of cartilaginous structures forming a third segmental unit that we interpret as atavistic epibranchials of the branchial arch in one population of the salamander Notophthalmus viridescens. These structures possess all the defining attributes of atavisms, and illustrate the special role that atavistic features play in resolving questions of homology recognition.
Ultrastructure of early cleavage and yolk extrusion in the marsupial Antechinus stuartii
Authors: Selwood Lynne , Sathananthan A. H.
Published: February 2005

The fertilized egg and the two‐cell stage and four‐cell stage of the marsupial Antechinus stuartii were studied by transmission electron microscopy. The features that make the fertilized egg of Antechinus stuartii different from those of any eutherian mammal are (1) the presence of a shell and (2) the relatively large quantity and polarized distribution of cytoplasmic inclusions, including lipid, protein yolk bodies, and protein fibers. Mitochondria and vesicles of smooth endoplasmic reticulum are also polarized in distribution. Early cleavage differs from that of eutherians in several ways: (1) it occurs in the uterus; (2) there is extrusion of a large, single, membrane‐bound yolk mass at first cleavage; and (3) blastomeres become separated after the second cleavage division and thus do not adhere by cell‐to‐cell contacts. Prior to the second division, blastomeres are connected to each other by remnants of the midbody and to the yolk mass by remnants of a cytoplasmic bridge. The yolk mass after extrusion is surrounded by plasma membrane and contains inclusions of lipid, protein yolk bodies, and fibers, as well as mitochondria and smooth endoplasmic reticulum. The blastomeres of the two‐cell and four‐cell stages also show intracellular polarization in the distribution of retained inclusions and organelles. Vesicles developing at the periphery of blastomeres and discharging their contents extracellularly increase in size and number from the fertilized egg to the four‐cell stage. The discharged contents may be implicated in early development of the blastula cavity.
Chondrocranium and ossification sequence of Hyla lanciformis
Authors: De Sa Rafael O.
Published: February 2005

Tadpoles of Hyla lanciformis live in midwater and have a normal, beaked, anteroventral, subterminal mouth. Overall, they are generalized pond‐type anuran larvae that show no specific modification for a particular habitat. The chondrocranium and ossification sequences of this hylid frog were studied, utilizing cleared and Alcian blue‐alizarin red‐stained tadpoles. The chondrocranium is similar to that of other unspecialized tadpoles. No larval otic process was found and a large process projecting from the otic capsule is considered homologous with the larval crista parotica described for other anurans. The pattern of cranial and postcranial ossification is reported. The sequence of cranial ossification is explained in the framework of functional changes of the skull through metamorphosis. Comparison with the available information for other hylid frogs shows clear differences in the ossification sequences. The sequence of postcranial ossification is described for the first time for any species of hylid frog.
A morphological study of the nervous system of the praesoma of Octospinifer macilentus (Acanthocephala: Noechinorhynchidae)
Authors: Gee Randall J.
Published: February 2005

The nerve pathways in the praesoma are described for the first time for a member of the genus Octospinifer. Eleven nerves, five paired, and one single, are traced from the cerebral ganglion to their associations with the musculature of the body wall, neck sense organs, and the musculature of the proboscis wall and the invertor muscles of the proboscis. The structure and location of the Stützzelle (support cell) and its association with the neck sense organs are described. A comparison with the nervous system in the praesoma of Noechinorhynchus and Paulisentis is discussed.