bluuebunny/crossref_metadata_2025 huggingface dataset:
Follicular dynamics and germinal bed activity during the annual ovarian cycle of the lizard, Calotes versicolor
Authors: Shanbhag Bhagyashri A. , Prasad B. S. Krishna
Published: February 2005

Changes in size frequency distribution of extrastromal follicles, atretric follicles (AF), and the number of oogonia, oocytes, and primordial follicles in the ovaries are studied in Calotes versicolor during its annual reproductive cycle. Extrastromal follicles were graded into stages I to VI based on their diemeter. Stage I (0.5–0.75 mm) follicles are found throughout the year. The recruitment of stage II (0.76–1 mm) and stage III (1.10–2 mm) follicles occurs during December and March, respectively. Follicles of stage I–III are found in greater number in May. Stage IV vitellogenic follicles (2.10–3 mm) are recruited in April. Advanced vitellogenic follicles (stage VI) are formed between May and August. From April to August, the ovaries of lizards contain vitellogenic follicles of stages IV or V or VI suggesting that once a set of follicles enters vitellogenic phase there is no recruitment of another set of vitellogenic follicles from previtellogenic follicles until the former ovulates. The presence of vitellogenic follicles and at least two sets of CL in July‐August suggest that C. versicolor may oviposit at least three clutches of eggs per season. The clutch size in this lizard varies from a maximum 24 eggs in May to a minimum of 13 eggs in September. The previtellogenic AF are found throughout the year. Atresia is more prevalent in stage III suggesting that these follicles are more prone to become atretic. Interestingly, atresia of vitellogenic follicles occurs rarely. Each ovary in C. versicolor has two germinal beds. The germinal beds contain a greater number of oogonia (536–696), primary oocytes (40–71), and primordial follicles (32–55) during prebreeding and early breeding phases of the ovarian cycle. © 1993 Wiley‐Liss, Inc.
Observations on the development of unusual melanization of leopard frog ventral skin
Authors: Fernandez Philip J. , Bagnara Joseph T.
Published: February 2005

The ontogeny of ventral pigmentation of two species of leopard frog, Rana pipiens and R. chiricahuensis, was examined by light microscopy and transmission electron microscopy to reveal how the unusual melanistic ventral pigmentation of R. chiricahuensis is achieved at the cellular level. Ventral skin of R. pipiens is always white. Ventral skin of adult R. chiricahuensis is white when frogs are background‐adapted to a white substrate, but ventral skin becomes nearly as dark colored as the dorsal skin when frogs darken in response to a black background. Skin samples from tadpoles of both species, newly metamorphosed frogs, and adult frogs were analyzed for chromatophore composition and distribution. Ventral skin of R. pipiens larvae, newly metamorphosed frogs, and adults and of R. chiricahuensis larvae was white due to abundant iridophores and no melanophores. Melanophore density in the ventral integument of R. chiricahuensis was 9.1 ± 2.8/mm2 in newly metamorphosed frogs and 87.0 ± 4.8/mm2 in adult frogs. Pigment within ventral melanophores migrated during physiological color change during background adaptation. © 1993 Wiley‐Liss, Inc.
Suboccipital muscles in the cat neck: Morphometry and histochemistry of the rectus capitis muscle complex
Authors: Selbie W. S. , Thomson D. B. , Richmond F. J. R.
Published: February 2005

The morphometry, histochemistry, and biomechanical relationships of rectus capitis muscles were examined in adult cats. This family of muscles contained six members on the dorsal, ventral, and lateral aspects of the upper cervical vertebral column. Three dorsal muscles (rectus capitis posterior major, medius, and minor) formed a layered complex spanning from C1 and C2 to the skull. Rectus capitis posterior major was composed predominantly of fast fibers, but the other two deeper muscles contained progressively higher proportions of slow fibers. One ventral muscle, rectus capitis anterior major, was architecturally complex. It originated from several cervical vertebrae and appeared to be divided into two different heads. In contrast, rectus capitis anterior minor and rectus capitis lateralis were short, parallel‐fibered muscles spanning between the skull and C1. The ventral muscles all had nonuniform distributions of muscle‐fiber types in which fast fibers predominated. Dorsal and ventral muscle groupings usually had cross‐sectional areas of 0.5 cm2 or more, reflecting a potential capacity to generate maximal tetanic force in excess of 9 N. Biomechanical analyses suggested that one muscle, rectus capitis lateralis, had its largest moment in lateral flexion, whereas the other muscles had large, posturally dependent moment arms appropriate for actions in flexion‐extension. The observation that most rectus muscles have relatively large cross‐sectional areas and high fast‐fiber proportions suggests that the muscles may have important phasic as well as postural roles during head movement. © 1993 Wiley‐Liss, Inc.
Organization of hematopoietic tissue in the intermolt lobster, Homarus americanus
Authors: Martin Gary G. , Hose Jo Ellen , Choi Maryanne , Provost Ron , Omori Gregg , McKrell Nancy , Lam Garrett
Published: February 2005

Hematopoiesis in the American lobster Homarus americanus, as in most decapod crustaceans, occurs in a thin tissue covering the dorsal surface of the foregut. This tissue is composed of loosely attached, ovoid lobules containing the hematopoietic precursors and maturing hemocytes. Release of hemocytes into the dorsal hemocoel is accomplished by rupture of a portion of the connective tissue capsule covering the lobule. Cross sections of the lobules contain between 6 and 40 hematopoietic cells, of which approximately 90% constitute stages in granulocyte maturation and 10% are intermediates in hyaline cell maturation. Hematopoietic precursors in these two lines are similar to those recently described in a penaeid shrimp Sicyonia ingentis. The mitotic rate averaged 5.1% (range = 0.7% to 15.8%) in intermolt lobsters, 90% comprised granulocyte precursors. © 1993 Wiley‐Liss, Inc.
Microstructure, ontogeny, and evolution of scale surfaces in xenosaurid lizards
Authors: Harvey Michael B.
Published: February 2005

Both scanning electron and light microscopy were used to examine the epidermal structure of scales taken from several ontogenetic stages of Xenosaurus grandis and Shinisaurus crocodilurus. In addition, scales from all xenosaurid species were examined by scanning electron microscopy to determine scale surface variation among genera, species, and subspecies. A varied and phylogenetically informative morphology characterizes the scale surfaces of xenosaurid lizards. Scale surface morphology is conservative among the species and subspecies of Xenosaurus, but is more variable between the two xenosaurid genera. Their scale surfaces are characterized by folds in the oberhautchen, beta, mesos, and alpha epidermal layers, forming polygonal ridges of a type previously described for the Iguania. The three species of Xenosaurus possess lenticular scale organs, whereas Shinisaurus has scale organs with spikes (bristles). The spikes of Shinisaurus are formed by the beta and oberhautchen layers, with the alpha layer forming a dome‐shaped cap over a dermal papilla. Shinisaurus crocodilurus exhibits a dramatic ontogenetic change in scale surface morphology, that is here reported for the first time in any lizard. © 1993 Wiley‐Liss, Inc.
Chiropteran tendon locking mechanism
Authors: Quinn Thomas H. , Baumel Julian J.
Published: February 2005

Rather than the usual mammalian scheme in which tendon and sheath surfaces provide as little friction as possible, the tendons and sheaths of many bats have a locking segment on the manual and pedal flexor tendon complex. This tendon locking mechanism (TLM) exists opposite the proximal phalanges of each toe and pollex of many bats. Its structure, similar to a ratchet mechanism, assists bats in hanging with little muscular effort. The third digit of the pelvic limb and the pollex of species representing 15 chiropteran families were studied to determine the presence or absence, morphology, and function of the TLM. Most of the species studied have a TLM consisting of a patch of tubercles on the ventral surface of the flexor tendon associated with the proximal phalanx of each pollex or toe. The sheath adjacent to this portion of the flexor tendon has a series of transverse folds or ridges, which, when engaged with the tubercles on the tendon, lock the tendon in place. The TLM is similar in megachiropterans and microchiropterans possessing it. The TLM is absent, however, in some of the microchiropterans studied, most notably in the phyllostomids. Since many birds have a TLM similar to that of bats, it is an excellent example of the convergent evolution of a feature brought about by similar functional pressures on birds and bats. © 1993 Wiley‐Liss, Inc.
Microtopography of Nippostrongylus brasiliensis (Nematoda: Heligmosomatidae): Parasitic larval stages and adults
Authors: Nembo B. , Goudey‐Perriere F. , Gayral P. , Perriere C. , Brousse‐Gaury P.
Published: February 2005

Specimens of the rat hookworm, Nippostrongylus brasiliensis (Nematoda) were recovered from lungs (third‐ and fourth‐stage larvae) and intestine (fourth‐stage larvae and adults). The following features were studied in the different stages by scanning electron microscopy: cephalic structures, especially sense organs, synlophe, cervical region, and caudal part. The main differences between the third and fourth stages concerned the lip‐like structures around the oral aperture, the appearance of the cephalic space with the presence of a cephalic cap in fourth‐stage larvae, the pattern of longitudinal ridges, and sexual differentiation. Pore‐like papillae, not seen in third‐stage larvae, developed in later stages. Deirids were observed only in adults, and phasmids were poorly discerned.

Some of these morphological features, such as the cephalic sense organ apertures and cuticle pores and micropores, can be observed only by scanning electron microscop y. The possible functions of these different structures and their relationship with the behavior of the worms during their life cycle are discussed. © 1993 Wiley‐Liss, Inc.
Renal vasculature and excretory system of the agamid lizard, Ctenophorus ornatus
Authors: O'shea James E. , Bradshaw S. Donald , Stewart Tom
Published: February 2005

The structure and ultrastructure of the vasculature and nephric tubules of the kidney of the Ornate Dragon Lizard, Ctenophorus (=Amphibolurus) ornatus, was investigated by light microscopy and scanning electron microscopy of resin casts. Compared with other agamid lizards, the arterial supply of only two arteries per kidney is small. The number of glomeruli per kidney in C. ornatus, at between 400 and 600, is low by reptilian standards and very low for lizards. The glomeruli are not only comparatively few in number but are also simple in the nature of their capillary configuration. These features are suggestive of a greatly reduced surface area for arterial filtration. In contrast to the small arterial supply, the afferent venous supply, the renal portal system (RPS), is substantial and forms an extensive capillary network throughout the kidneys. No venous shunts were found in the kidneys, suggesting that the venous network is functioning as a true portal system. Valves were not identified within the RPS, implying that neural control of general vascular tone could alter velocity and perhaps the direction of blood flow by changing pressure profiles. The nephroi are comparatively short and display features consistent with the production of urate precipitates as the primary nitrogenous waste product. A close association between the distal tubule (DT) and the glomerular hilus may demonstrate a simple form of a juxtaglomerular apparatus. The finding of aglomerular tubules indicates an important role for tubular secretion. The results of this study indicate that these lizards may have a reduced reliance on filtration for homoiostasis and a greater reliance on tubular secretion. © 1993 Wiley‐Liss, Inc.
Larval and adult eyes in Capitella spec. I (Annelida, Polychaeta)
Authors: Rhode Birgit
Published: February 2005

Larval and adult eyes of the capitellid Capitella spec. I have been investigated by electron microscopy. Developing larvae possess one pair of eyespots. Each eyespot is composed of one sensory cell, one pigment cell, and one supporting cell. The sensory cell bears a photosensory apparatus, an array of parallel microvilli containing a striking form of submicrovillar cisternae (SMC). A single basal body was observed near the basal end of the SMC only in 3–4‐day‐old larvae. This basal body was not observed in older larvae. A special, thus far unreported feature of the pigment cell is a ring of microvilli‐like structures that project from the edge of the pigment cup and form a kind of diaphragm around the head of the sensory cell. Each of these microvilli‐like structures is covered with closely packed rows of tiny plates, giving them a fimbriated appearance. After metamorphosis, the larval eyespots are reduced.

Adult specimens possess one pair of eyes. In juvenile worms the eye is built of 2–3 pigment cells and one sensory cell. The volume of adult eyes increases by the addition of 2–3 sensory cells. The pigment cells are deposited one upon the other, wrapping the sensory complex in the center. Each sensory cell forms a deep depression at its apical end where up to three cilia and numerous microvilli arise. The sensory processes project into a common ocular cavity. Long microvilli of the uppermost pigment cells project into an extracellular channel that reaches from the ocular cavity up to the cuticle. A single fourth sensory cell of identical structure may occur next to the eye directly beneath the cuticle and close to the opening of the ocular channel.

Signs of progressive disintegration of the pigment cells can be observed in adult specimens. Sensory cells are not affected by this reduction process. Eyes resembling those of Capitella spec. I have never been reported before. Their functional qualities are discussed. © 1993 Wiley‐Liss, Inc.
Neuromuscular organization and regional EMG activity of the pectoralis in the pigeon
Authors: Boggs Dona F. , Dial Kenneth P.
Published: February 2005

In order to improve our understanding of the neuromuscular control of the most massive avian flight muscle, we studied the innervation pattern of the pigeon pectoralis. Nine primary branches from the rostral trunk and nine to ten branches from the caudal trunk of the pectoral nerve were identified by microdissection in ten pigeons. The region of muscle that each branch innervates was delineated by nerve stimulation studies (ten pigeons) and six regions were confirmed by glycogen depletion (ten pigeons). In pigeons, branches from the rostral nerve innervate the anterior 3/5 of the sternobrachialis (SB) head of the pectoralis and branches from the caudal trunk innervate the posterior 1/2 of the SB and all of the throacobrachials (TB). In the SB, individual branches of the rostral pectoral nerve innervate wedge‐shaped muscle regions (each approximately 1.3 cm wide), collectively forming a fan shaped arrangement along the sternal carina. Adjacent muscle regions partially overlap at their boundaries. Within the thoracobrachialis (TB) head of the pectrolis, muscle regions are wider. There is a region in mid‐SB‐where the innervation territories of the rostral and caudal nerves oferlap. Electromyographic (EMG) activity patterns were recorded within ten of the identified muscle regions during take‐off, level flapping flight, and landing. Onset of EMG activity and EMG intensity within various muscle regions exhibits significant differences both within a wingbeat cycle and among different modes of flight. The innervation pattern of the pectoralis presents the anatomical substrate for neuromuscular compartmentalization and differential EMG activity within the pectoralis may reflect sensory‐motor partitioning. The extent to which the neuromuscular compartmentalization of the pectoralis corresponds to its ability to produce an array of force vectors to the wing awaits further more detailed biomechanical studies. © 1993 Wiley‐Liss, Inc.
Changes in geometry of activily shortening unipennate rat gastrocnemius muscle
Authors: Zuurbier C. J. , Huijing P. A.
Published: February 2005

Muscle geometry of the unipennate medial gastrocnemius (GM) muscle of the rat was examined with photographic techniques during isometric contractions at different muscle lengths. It was found that the length of fibers in different regions of GM differs significantly, and proximal aponeurosis length varies significantly from distal aponeurosis length; the angle of the aponeurosis with the muscular action differs significantly among regions at short muscle lengths (full contraction). These data support the idea that the unipennate GM cannot be represented by a parallelogram in a two‐dimensional analysis. As the muscle shortens, the area of the mid‐longitudinal plane of the GM decreases by 24%, a decrease that may be explained by assuming fiber diameter to increase in all directions. The angle between fiber and aponeurosis is determined by more than fiber length. Hence, such important assumptions as a parallelogram with constant area and fiber angle γ changes determined by fiber length changes, freqently used in the theoretical analysis of the morphological mechanism of unipennate muscle contraction, do not hold for the unipennate GM of the rat.

Length of the sarcomere within the mid‐longitudinal plane of GM varies from 1.92 to 2.14 μm among the different muscle regions at muscle optimum length (length at which force production is highest), whereas shortening to 6 mm less than optimum length produces a range of sarcomere lengths from 0.89 to 1.52 μm. These data suggest that fibers located in different regions of the GM reach their optimum and slack lengths at various muscle lengths. © 1993 Wiley‐Liss, Inc.
Two different patterns of interrupted spermatogenesis in winter diapause and summer quiescence in the desert beetle, Omorgus freyi
Authors: Friedländer Michael , Scholtz Clarke H.
Published: February 2005

Spermatogenesis discontinues during both adult reproductive diapause and quiescence in the flightless males of Omorgus freyi. During both types of dormancy, spermatogenesis discontinuity is a dynamic process involving an uninterrupted supply of primary spermatocytes that undergoes partial development and lyses before spermatozoa can be formed. Notwithstanding this common feature, the pattern of discontinuity differs between the two kinds of dormancy. During reproductive diapause, spermatozoa and late spermatids are the first cells that lyse; after diapause break, spermatozoa are produced anew. During quiescence, in contrast, the first indication of discontinuity is the degeneration of late primary spermatocytes; spermatozoa apparently remain intact for a while but eventually degenerate as well. Therefore, males returning to sexual activity after a short period of quiescence may still have spermatozoa capable of fertilization. However, following a long period of quiescence, spermatozoa will be absent and must be produced anew, as in postdiapausing males. The existence of two different patterns of spermatogenesis discontinuity may indicate that each is controlled differently by the endocrine system, in response to the different environmental conditions inducing quiescence or diapause. Dual control of discontinuity may contribute to the high reproductive potential of these flightless beetles, under unpredictable and extreme desert conditions. © 1993 Wiley‐Liss, Inc.
Morphological and functional body reconstruction in a teleost of the genus Oreochromis (Cichlidae)
Authors: Fishelson Lev
Published: February 2005

The process of morphological and functional regeneration was followed on a tilapid fish, a cross of Oreochromis aureus × Oreochromis niloticus, by observations on movements and the use of X‐rays. A four‐year‐old adult fish that lost its tail as post larva, including ten vertebrae, was able to reconstruct a novel and shorter central skeleton, including a specially modified urostyle. The enlarged and strengthened pterygiophores and their junctions with the dorsal and anal spine formed a fast‐holding base for the fins, the posterior part of which largely performed the functions of the missing caudal fin. Although the fish was much shorter than usual, this male behaved and functioned normally. © 1994 Wiley‐Liss, Inc.
Characteristics of the flagellar axoneme in Neuroptera, Coleoptera, and Strepsiptera
Authors: Afzelius Björn A. , Dallai Romano
Published: February 2005

Spermatozoa from representatives of the five insect orders in superorder Neuropteroidea were examined by electron microscopy following a new fixation method that includes tannic acid in the primary fixative but has uranyl acetate rather than osmium tetroxide as the secondary fixative. The sperm axoneme was found to be similar in the four orders Megaloptera, Raphidioptera, Neuroptera, and Coleoptera, and is characterized above all by its so‐called intertubular material being divided into two portions, one located outside, but in contact with the doublet, and the other projecting from the accessory tubule and having a beak‐like shape. These features have not been seen in insects from other orders and may be a synapomorphy for these neuropteroid orders. The accessory tubules in these four orders have 16 protofilaments. The shape of the accessory bodies adjacent to the mitochondrial derivatives is nearly the same in insects from the more primitive neuropteroid orders and in Coleoptera. The sperm tail of the examined strepsipteran deviates in several respects from that of other neuropteroids: the particle row in the wall of accessory tubules is incomplete, an intertubular material is missing, and the mitochondria contain no crystal. © 1994 Wiley‐Liss, Inc.
Anatomy of the propatagium: The great horned owl (Bubo virginianus)
Authors: Brown Richard E. , Baumel Julian J. , Klemm Robert D.
Published: February 2005

Skinfolds and feathers form the profile of the avian airfoil. The wing of birds has a nearly flat profile from shoulder to carpus, without the presence of the propatagium. The propatagium is the largest skinfold of the wing; it fills the angle formed by the partially flexed elbow, and with its feathers forms a rounded leading edge and dorsally cambered profile added to the cranial aspect of the wing. The propatagium is variably deployed, relative to elbow extension, in flight; support for its cambered shape is maintained by multilayered collagenous and elastic tissue networks suspended between leading edge and dorsal antebrachium. The leading edge ligament (Lig. propatagiale) courses from deltopectoral crest to carpus and, with its highly distensible center section, supports the leading edge of the propatagium across a range of wing extensions. The elbow extension limiting ligament (Lig. limitans cubiti) courses from deltopectoral crest to proximal antebrachium and limits maximum elbow extension. M. deltoideus, pars propatagialis inserts on the proximal end of the common origin of the propatagial ligaments and, by way of the insertions of the two ligaments, coordinates (1) automatic flexion / extension actions of the elbow and wrist, (2) propatagial deployment, and (3) tension along the length of Lig. propatagiale supporting the leading edge. © 1994 Wiley‐Liss, Inc.
Praesomal nerves in Corynosoma hamanni (Acanthocephala: Polymorphidae)
Authors: Gee Randall J. , Holloway Harry L.
Published: February 2005

Investigated by light microscopic observations, nerve pathways and the Stützzellle are described in the praesoma of a species of Corynosoma. The pathways are described for 13 nerves, 6 paired and one single nerve, which originate from the cerebral ganglion and terminate in the body wall musculature and the proboscis. © 1994 Wiley‐Liss, Inc.
Salivary glands of the cockroach, Periplaneta americana: New data from light and electron microscopy
Authors: Just F. , Walz B.
Published: February 2005

We have reinvestigated the morphology of the salivary glands in the cockroach, Periplaneta americana, by light, electron, and confocal laser scanning microscopy. All secretory acini have a uniform structural layout. They consist of three cell types: peripheral cells, central cells, and duct cells. One pair of peripheral cells forms the base of each acinus. The central cells, arranged concentrically in a fourfold symmetry around the most proximal part of the acinar ducts, lie next downstream. In every acinus, duct cells accompany the central cells and form a thin sheet on the apical surface of the latter. This apical lining of the duct cells is regularly fenestrated, and the central cells secrete the contents of their secretory vesicles only through these openings into the lumen of the ducts. Peripheral cells and central cells are never in direct physical contact, because, apically, extensions of the inner acinar duct cells intervene between the cells. Basally, thin extensions of the basement membrane separate the cell types. We have found no morphological evidence for the existence of electrical coupling (gap junctions) between the saliva‐producing cells. Our ultrastructural data support the view that the peripheral cells are responsible for water and electrolyte transport, whereas only central cells secrete the proteinaceous components of the saliva.

We have found that the duct cells distal to the acini are also specialized for ion and water transport. They have a prominent basal labyrinth containing numerous mitochondria and a highly folded apical surface. The folded apical membrane surface is coated with electron‐dense particles on its cytoplasmic side; these particles are probably portasomes. Our investigation provides morphological evidence that the duct cells distal to the secreting acini are able to modify primary saliva. © 1994 Wiley‐Liss, Inc.
Follicular placenta of the viviparous fish, Heterandria formosa: II. Ultrastructure and development of the follicular epithelium
Authors: Grove Bryon D. , Wourms John P.
Published: February 2005

Embryos of the viviparous poeciliid fish, Heterandria formosa, develop to term in the ovarian follicle where they undergo a 3,900% increase in embryonic dry weight. Maternal‐embryonic nutrient transfer occurs across a follicular placenta that is formed by close apposition of the embryonic surface (i.e., the entire body surface during early gestation and the pericardial amnionserosa during mid‐late gestation) to the follicular epithelium. To complement our recent study of the embryonic component of the follicular placenta, we now describe the development and fine structure of the maternal component of the follicular placenta. Transmission electron microscopy reveals that the ultrastructure of the egg envelope and the follicular epithelium that invests vitellogenic oocytes is typical of that described for teleosts. The egg envelope is a dense matrix, penetrated by microvilli of the oocyte. The follicular epithelium consists of a single layer of cuboidal cells that lack apical microvilli, basal surface specializations, and junctional complexes. Follicle cells investing the youngest embryonic stage examined (Tavolga's and Rugh's stage 5–7 for Xiphophorus maculatus) also lack apical microvilli and basal specializations, but possess junctional complexes. In contrast, follicle cells that invest embryos at stage 10 and later display ultrastructural features characteristic of transporting epithelial cells. Apical microvilli and surface invaginations are present. The basal surface is extensively folded. Apical and basal coated pits are present. The cytoplasm contains a rough endoplasmic reticulum, Golgi complexes, and dense staining vesicles that appear to be lysosomes. The presence of numerous apically located electron‐lucent vesicles that appear to be derived from the apical surface further suggests that these follicle cells may absorb and process follicular fluid. The egg envelope, which remains intact throughout gestation and lacks perforations, becomes progressively thinner and less dense as gestation proceeds. We postulate that these ultrastructural features, which are not present in the follicles of the lecithotrophic poeciliid, Poecilia reticulata, are specializations for maternal‐embryonic nutrient transfer and that the egg envelope, follicular epithelium, and underlying capillary network form the maternal component of the follicular placenta. © 1994 Wiley‐Liss, Inc.
Pufferfish inflation: Functional morphology of postcranial structures in Diodon holocanthus (Tetraodontiformes)
Authors: Brainerd Elizabeth L.
Published: February 2005

For the purpose of defending itself against predators, the balloonfish (Diodon holocanthus) can triple its body volume by pumping water into its stomach. Diodon holocanthus exhibits striking structural and functional specializations for inflation. The stomach of the balloonfish is highly extensible and has lost its digestive function, it is repeatedly folded upon itself and is lined with transitional epithelium. The peritoneal cavity of the balloonfish is also large and extensible. During inflation, the stomach expands into an existing peritoneal space surrounding the axial musculature and presses the folded peritoneum out into potential peritoneal spaces ventral to the head and surrounding the dorsal fin, anal fin, and caudal peduncle; only the dorsal and lateral surfaces of the head are unaffected. Balloonfish skin is also specialized for inflation. Because the collagen fibers in the dermis of unstretched skin are wavy, little force is required to extend the skin up to 40% of its rest length. At high strains, the collagen fibers are stressed directly and the skin suddenly becomes stiff. Stiff skin surrounding a ball of incompressible water provides a rigid framework for the support of the erectile spines, and the balloonfish becomes a formidable, spiny sphere. However, not all of the structural and functional features that contribute to the ability of balloonfish to inflate are evolutionary adaptations specifically for inflation. Absence of pleural ribs, absence of a pelvis, and the orthogonal arrangement of dermal collagen sheets in the skin were all present in the ancestor of pufferfishes, and thus, must be considered exaptations. Sagittal plane flexibility of the vertebral column may be an epiphenomenon of the lengthening of the body cavity for more spherical inflation. Together these structural and functional features—whether adaptations, exaptations, or epiphenomena—combine to produce a highly effective mechanical defense. © 1994 Wiley‐Liss, Inc.
Ontogeny of the sea bass spleen (Dicentrarchus labrax): A light and electron microscopic study
Authors: Quesada J. , Villena M. I. , Navarro V.
Published: February 2005

The splenic rudiment in sea bass (Dicentrarchus labrax) appears 18 days after hatching in the right side of the body, close to the dorsal wall of the anterior part of the intestine. It acquires its final localization after about 2 months in a middle‐ventral position between the cecal part of the stomach and the first intestinal loop. The haemopoietic activity of this spleen during organogenesis varies with age. During the first 40 days only erythropoietic activity is shown, after which thrombopoiesis begins and the first lymphocytes appear. At the time that the amorphous extracellular matrix increases, some reticular, cells of the stroma undergo an active lipid synthesis, which ceases when the larvae are about 2 months old. All the above coincides with a decrease in erythropoiesis and total vascular development, although the ellipsoids and sinusoids do not present their final structure until later stages. These structural variations create microenvironmental conditions which favor modifications in the activity of the spleen. This relation between microenvironment and changes in haematopoietic organ function has also been described in mammals and birds (Metcalf and Moore [1971] Frontiers of Biology. Amsterdam: North Holland; Quesada et al. [1985] J. Submicrosc. Cytol. 17:537–540; Yassine et al. [1989] Cell Diff. Dev. 27:29–45). © 1994 Wiley‐Liss, Inc.
Microscopy of vascular architecture and arteriovenous communications in the spleen of two odontocetes
Authors: Tanaka Yasukazu
Published: February 2005

The red pulp of the spleens of the short‐finned pilot whale (Globicephala macrorhynchus) and the Pacific bottle‐nosed dolphin (Tursiops truncatus gilli) (Odontoceti) were examined by light and electron microscopy and found to comprise two venous layers, an inner and an outer. The inner layer is homologous to the intermediate zone (IZ) of primitive‐type mammalian spleens and contains sinusoids consisting of endothelial cells and a thin layer of extracellular deposits. Its vascular structure is unclear. The venous vessels of this layer eventually communicate with veins of the perivenous outer layer. The perivenous layer contains veins of various sizes, interstitial elements, and trabeculae. It is filled with blood cells, particularly plasma cells, but no myeloid cells. The perivenous layer (PVL) is homologous to the red pulp of common mammalian spleens but shows signs of involution.

The white pulp gives origin to arterial terminals that end in the red pulp, where they communicate directly with the sinusoidal veins producing a closed circulation. The arterial terminals do not show ellipsoids. The presence of an IZ with a closed circulation and the involution of the red pulp makes the spleen of Odeontoceti another example of a mammalian spleen of the primitive type that has been altered by the evolutionary process. Vascular remodelling of the spleen of Odontoceti seems to follow the pattern noted in the spleens of nonmammalian vertebrates. © 1994 Wiley‐Liss, Inc.
Morphology and density distribution of cone photoreceptor in the retina of the atlantic stingray, Dasyatis sabina
Authors: Logiudice F. T. , Laird R. J.
Published: February 2005

Light miscroscopy of the retina in the Atlantic stingray, Dasyatis sabina, reveal two distinct photoreceptor types. Histological criteria establish the two cell types as morphological rods and cones. The retina was studied through a sequential series of vertical sections in a protocol designed to evaluate the entire retina. By performing differential counts in multiple regions and expressing cones as a percent of the total photoreceptors in a domain, it was possible to determine relative cone density and distribution. Cone distribution varies throughout the retina in two patterns. First, relative cone density gradually decreases peripherally. Second, a cone‐rich band occurs along the horizontal axis of the eye, extending from ora serrata to ora serrata. This structure appears to be a visual streak. Both distribution patterns are statistically significant and are consistent among animals regardless of age. © 1994 Wiley‐Liss, Inc.
Immunohistochemical distribution of calbindin D‐28k and parvalbumin in the head of the caudate nucleus and substantia nigra of the cat
Authors: De Las Heras Silvano , Hontanilla Bernardo , Mengual Elisa , Giménez‐Amaya José Manuel
Published: February 2005

The heterogeneous anatomy of both the dorsal striatum at the level of the head of the caudate nucleus and of the substantia nigra of cats was analyzed immunohistochemically using two calcium‐binding proteins, namely, calbindin D‐28k and parvalbumin. The striatal histochemical markers nicotinamide‐adenine dinucleotide phosphate diaphorase and acetylcholinesterase were revealed in sections adjacent to those used for the immunohistochemical procedure. The distribution of both the calbindin D‐28k and the parvalbumin immunoreactivities is heterogeneous in dorsal, ventral, lateral, and medial areas of the head of the caudate nucleus and is in register with the striosome/matrix pattern displayed by the histochemical markers. These calcium‐binding proteins preferentially are located in the matrix compartment of the rostral caudate nucleus. Moreover, in some areas of the rostral two‐thirds of the substantia nigra, calbindin D‐28k and parvalbumin immunoreactivities appear to follow a complementary pattern that is quite different from the mesencephalic distribution of these two calcium‐binding proteins. © 1994 Wiley‐Liss, Inc.
Histoenzymological studies on embryonic and posthatching development of the ovary in the tropical oviparous lizard, Calotes versicolor
Authors: Doddamani Laxmi S.
Published: February 2005

The development of the ovary in the lizard Calotes versicolor has been studied histologically and histochemically from the day of oviposition (stage 27) to 2 months after hatching. The gonadal component appears as a genital ridge at stage 27. Sex differentiation of gonads occurs at stage 34, which indicates that the period of sexual bipotentiality is very brief. Oogenesis starts at stage 35, where preleptotene and leptotene oocytes appear for the first time in the ovary. The zygotene and pachytene oocytes appear during stage 36 and 38. Diplotene oocytes occur at stage 40. Folliculogenesis occurs 10 days after hatching. Follicles having a polymorphic membrana granulosa consisting of small, intermediate, and large round cells are found in 1‐month‐old hatchlings, and pyriform cells are observed in the granulosa of the ovary of 2‐month‐old hatchlings. The number of germ cells increases as development of the ovary proceeds. At oviposition, ∼236 and 244 germ cells were counted in right and left ovaries, respectively, and there was a manyfold increase in their number (to 4,234 and 4,294) at hatching. Mitotic germ cells are more abundant at stage 34, and no mitotic germ cells are seen after hatching.

Histochemical localization of of ‐3β‐HSDH and G‐6‐PDH activity is seen in the medulla of the ovary after sexual differentiation (stage 36), which indicates that the medulla of the ovary is the site of steroidogenesis. intensity of the enzyme activity remains more or less the same in the ovary up to 1 month after hatching and begins to increase thereafter. © 1994 Wiley‐Liss, Inc.
Unique locomotory mechanism of Mermis nigrescens, a large nematode that crawls over soil and climbs through vegetation
Authors: Gans Carl , Burr A. H. Jay
Published: February 2005

Females of Mermis nigrescens, a nematode parasitic on grasshoppers, climb through terrestrial vegetation where they lay their eggs. The 100‐mm‐long body of these nematodes bridges gaps in this three‐dimensional substratum, and crawls efficiently over planar surfaces. The nematodes do not use the classical undulant pattern of nematode locomotion as one coordinated unit; instead they propel themselves in several independent, locally controlled zones that propagate posteriorly. A repeated motion of their anterior end laces the body around fixed objects at which force may be applied. Propulsive force is applied to objects as the body glides past the contact site. Intermediate loops are elevated above the surface where they cannot contribute to propulsion. These loops rise and fall with time due to varying differences in propulsive forces between the contact sites.

Forces are applied to the objects by internally generated bending couples that are propagated along the trunk, propelling the body in a cam‐follower mechanism. Bending couples are generated by the contraction of ventral or dorsal longitudinal muscle bands that apply compressive force to the cuticle. The muscle bands, consisting of a single layer of obliquely striated muscle cells, are closely applied to the cuticle and are separated from it only by a fibrous basal lamina and a thin extension of a hypodermal cell. The myofilaments of each sarcomere are parallel to the body axis and attached perpendicularly via dense bodies (z‐line equivalents) to the basal lamina, which in turn is fixed to the cuticle via filaments passing through the hypodermal cytoplasm, Consequently, forces are transmitted laterally to the cuticle over the entire length of the muscle, compressing it parallel to the surface without need for attachment to the terminal ends of the muscle cells. Thus the muscles are engineered for local control of bending and avoidance of buckling. There is evidence that the motor nervous system of Mermis may not be as simple as in classical nematode examples, which may explain why Mermis is capable of a much more localized control of locomotory motion. © 1994 Wiley‐Liss, Inc.
Development of craniofacial musculature inMonodelphis domestica(marsupialia, didelphidae)
Authors: Smith Kathleen K.
Published: February 2005

Development of craniofacial muscles ofMonodelphis domestica(Marsupialia, Didelphidae) is described. In a period of 4–6 days all craniofacial muscles inM. domesticaprogress from myoblast condensation, to striated myofibers that are aligned in the direction of adult muscles and possess multiple, lateral nuclei. This process begins 1 to 2 days before birth and continues during the first few days after birth. Compared to other aspects of cranial development, muscle development inM. domesticais rapid. This rapid and more or less simultaneous emergence of craniofacial muscles differs from the previously described pattern of development of the cranial skeleton in marsupials, which displays a mosaic of acceleration and deceleration of regions and individual elements. Unlike the skeletal system, craniofacial muscles show no evidence of regional specialization during development.M. domesticaresembles eutherian mammals in the relatively rapid and more or less simultaneous differentiation of all craniofacial muscles. It differs from eutherian taxa in that most stages of myogenesis occur postnatally, following the onset of function. The timing of the development of muscular and skeletal structures is compared and it is concluded that the relatively early development of muscle is not reflected by any particular acceleration of the differentiation or growth of skeletal structures. Finally, the difficulties in accounting for complex internal arrangements of muscles such as the tongue, given current models of myogenesis are summarized. © 1994 Wiley‐Liss, Inc.
Kinematic analysis of jaw protrusion in orectolobiform sharks: A new mechanism for jaw protrusion in elasmobranchs
Authors: Wu Ernest H.
Published: February 2005

Jaw protrusion is an important component of prey capture in fishes, although the mechanics of protrusion have thus far been studied largely in teleosts. Elasmobranchs are also able to protrude their jaws (Tricas and McCosker [1984] Proc. Cal. Acad. Sci. 43: 221–238; Tricas [1985] Mem. S. Calif. Acad. Sci. 8:81–91.; Frazzetta and Prange [1987] Copeia 4:979–993). Several related features of the feeding apparatus contribute to jaw protrusion in sharks. Labial cartilages form an extendible series attached dorsally to the anterolateral face of the palatoquadrate and ventrally to the anteroventral surface of Meckel's cartilage. The labial cartilage chain swings anterolaterally as the lower jaw is depressed, thrusting the labial margins forward to form a circular oral opening and displacing the jaw apparatus towards the food; this pattern is analogous to halecomorph and primitive actinopterygian fishes in which the maxilla swings forward (Lauder [1979] J. Zool. Lond. 187:543–578). The palatoquadrate and Meckel's cartilage also project anteriorly and represent the major contribution to protrusion. These movements occur simultaneously with enlargement of the oral cavity to generate suction. The wobbegong sharks (Orectolobidae) are specialized for jaw protrusion. The spotted wobbegong protrudes its jaw by 33% of its chondrocranial length using two different mechanical systems. In the first mechanism of jaw protrusion, the intermandibularis and interhyoideus muscles medially compress the lower jaw and hyomandibulae. Compression of the lower jaw results in a more acute symphyseal angle so that the anteroposterior alignment of the lower jaw increases due to the rotation of each lower jaw towards a saggital orientation. Distal compression of the hyomandibulae at their attachments to the jaws swings the jaws forward. The second mechanism involves rotation of the ceratohyal around a posterior process of the lower jaw, pushing the hyomandibulae anteroventrally, thereby pushing the jaw articulation ventrally and anteriorly to protrude the jaws. © 1994 Wiley‐Liss, Inc.
Olfactory organ of acipenseriformes and comparison with other actinopterygians: Patterns of diversity
Authors: Chen Xin‐Yu , Arratia Gloria
Published: February 2005

The position and structure of the olfactory organ and its openings vary among actinopterygians. The anterior nasal opening is a simple perforation in the skin in many extant actinopterygians (e.g., acipenseriforms, lepisosteids, and primitive Recent teleosts) and represents the primitive condition. Polypterids and Amia each exhibit a derived condition, in which the anterior nasal opening extends into a tube. The olfactory organ is relatively far away from the anterior end of the elongate rostrum in acipenseriforms, whereas the olfactory organs are closer to the anterior end of the snout in extant actinopterygians (e.g., polypterids, lepisosteids, and amiids). In adults, olfactory organs are cuplike structures in most actinopterygians, but these organs are tubelike in polypterids. Among extant actinopterygians, a nasal diverticulum is present only in polypterids. Teleosts have accessory nasal sacs, but chondrosteans, polypterids, lepisosteids, and amiids lack them.

The olfactory rosette is formed by primary folds or lamellae that may be placed anterior, lateral, posterior, and/or medial to the axis of the organ. Large acipenserids have 20–32 lamellae, polyodontids have 13–18 lamellae, lepisosteids have 8–10 lamellae, and Amia may have over 100. In teleosts, the number of lamellae varies from none or a few to over 200. Secondary lamellae are present in acipenseriforms, lepisosteids, and some advanced teleosts; secondary lamellae are interpreted as independently acquired in these lineages. Secondary lamellae are absent in Amia and primitive teleosts such as Elops and Hiodon. Tertiary lamellae are present in Acipenser oxyrhynchus. The arrangement of the primary lamellae in relation to the axis of the organ results in at least 11 patterns of the olfactory rosette in actinopterygians. Lamellae that are enclosed in a tubelike sac and that have an anteromedial diverticulum are specializations of polypterids. Primary lamellae anterior, lateral, and posterior to an elongate axis are characteristic of lepisosteids. The presence of primary lamellae lateral, medial, and posterior to an elongate olfactory axis is a synapomorphy of Halecomorpha (Amia plus teleosts). The absence of secondary lamellae is a synapomorphy of Halecomorpha. © 1994 Wiley‐Liss, Inc.
Spermathecae of Salamandrina terdigitata (Amphibia: Salamandridae): Patterns of sperm storage and degradation
Authors: Brizzi Rossana , Delfino Giovanni , Selmi Maria Gloria , Sever David M.
Published: February 2005

The spermathecae of female Salamandrina terdigitata were observed using light and transmission electron microscopy during the fallspring period of sperm storage and secretory activity and during the summer stasis. When sperm are stored inside the spermathecae, the product synthesized by spermathecal epithelial cells is exported into the lumen, where it bathes the sperm. During sperm storage some spermatozoa undergo degradation by the spermathecal epithelium. This process, which includes sperm capture by the apical microvilli, formation of endocytic vacuoles and production of lysosomes, becomes prominent shortly after oviposition. In many instances, cells filled with vacuolized spermatozoa and/or residual bodies undergo desquamation from the spermathecal epithelium and enter the lumen together with residual sperm. Desquamated cells, together with residual sperm, are a common feature in the spermathecal lumina at the end of the egg‐laying season.

Concomitant to the activity of the spermathecal epithelium, macrophages move into the spermathecae from the stroma and contribute to the degradation of both the residual sperm and desquamated epithelial cells. As a result of this degradation activity, spermathecae observed during the short summer stasis appear devoid of secretory product and sperm. By late summer, however, the spermathecae already show early signs of an imminent resumption of biosynthetic activity. © 1995 Wiley‐Liss, Inc.