bluuebunny/crossref_metadata_2025 huggingface dataset:
Gross structure and function of the quadriceps femoris in Lemur fulvus: An analysis based on telemetered Electromyography
Authors: Jungers William L. , Jouffroy FrançOise K. , Stern Jack T.
Published: February 2005

Analysis based on telemetered electromyography from the quadriceps femoris of Lemur fulvus, a Malagasy prosimian, during walking, galloping, leaping, and a variety of postural behaviors partially confirms and partially contradicts earlier hypothesized functions of this musculoskeletal complex. As predicted on the basis of morphological criteria (large physiological cross‐section and long parallel fibers), the vastus lateralis is of special functional significance in leaping. This relatively large muscle consistently initiates the leap and frequently undergoes a very long period of force enhancement via active stretch. By contrast, the vastus intermedius fails to exhibit increased electrical activity and undergoes little or no active stretch during jumps. The myological details of vastus intermedius (short fibers, no fusion with other components), therefore, cannot be accounted for as adaptations to leaping. Rather, a primary postural role is indicated for the vastus intermedius, because in normal resting postures, with the knee quite flexed, it alone is continuously active. The existence of a fibrocartilaginous superior patella in the tendon of vastus intermedius, however, is most plausibly related to the complex tensile and compressive stresses generated in the tendon during the completely hyperflexed phase of leaping.

The phasic patterning of the quadriceps femoris of Lemur fulvus does not point to any special role of the vastus lateralis or vastus intermedius during walking and galloping; it does indicate very different patterns of muscle recruitment in comparison to those in nonprimate mammals and some anthropoid primates. The forward cross walk (diagonal sequence, diagonal couplets) of primates versus the backward cross gait (lateral sequence) of most other mammals probably accounts for some of these differences. Lemur fulvus lacks the degree of elastic storage and release of kinetic energy in the quadriceps femoris that characterizes the gallop of dogs, cats, and Erythrocebus patas.
In vitro differentiation of tooth buds from embryos and adult lizards (L. gravenhorsti): An ultrastructural comparison
Authors: Lemus D. , Paz De La Vega Y. , Fuenzalida M. , Illanes J.
Published: February 2005

It is well established that the capacity for teeth to differentiate “in vitro” depends upon: (a) the age of the embryonic rudiments at the time of excision and (b) the number of cells within each tissue type which are capable of differentiating into organ culture. This paper studies ultrastructural aspects of tooth buds grown in vitro from lizard embryos and compares these characteristics with those observed in dental germs grown in situ in older lizard embryos. Moreover, we report the self‐differentiation in vitro dental tissues from adult lizard and compare this phenomenon with the main features of a morphogenetic field. Our results suggest that approximately in the first third of gestation in L. gravenhorsti the dental buds has already acquired the capacity for self‐differentiation in vitro. The ultrastuctural observations show that there are no significant differences between odontoblasts and ameloblasts in situ and in vitro. The tooth from “adult lizards,” isolated by combined microsurgical and enzymatic procedure and cultured in semisolid‐liquid medium were also able to differentiate teeth. This phenomenon implies that self‐differentiation is not rigidly determined, and that in these animals the tooth tissues represents a continuous morphogenetic field throughout the animal's life. This property is intrinsic, resides in the isolated tooth tissues, and is relatively independent of external factors. In addition, these studies indicate that the chick chorio–allantoic membrane and the semisolid‐liquid culture medium supply the majority of the factors required for development of these tissues.
The projection of neuroendocrine fibers (NCC I and II) in the brains of three orthopteroid insects
Authors: Koontz Margaret , Edwards John S.
Published: February 2005

Neuronal projections from neuroendocrine tracts (nervi corpori cordiaci I and II) in the brains of the locust (Schistocerca vaga), cricket (Acheta domesticus), and cockroach (Periplaneta americana) were studied using reconstructions of silver‐intensified cobalt chloride preparations. Collaterals from the NCC I in these species branch extensively in the dorsal protocerebral neuropile, anterior to the stalk of the corpora pedunculata and ventral to its calyces. Other fibers project from the NCC I bilaterally into the medial protocerebral neuropile, anterior to the central body, and posterior to the beta lobes. NCC II collaterals arborize in the medial, dorsal, and lateral protocerebral neuropile, their region of projection partially overlapping with that of the NCC I. Several NCC II fibers terminate in the superior arch of the central body in Acheta but not in the other two species. Tritocerebral cells filled through the NCC I branch in the medial tritocerebral neuropile in all three species, but most extensively in Schistocerca. No NCC fibers were seen to penetrate any part of the corpora pedunculata, protocerebral bridge, olfactory glomeruli, ocellar tracts, or optic lobes.

These neuronal projections from the NCC I and II lie anterior to regions of branching of second‐order ocellar fibers and thus provide no anatomical basis for direct ocellar input to neurosecretory cells, contrary to previous reports for orthopteroid species (Brousse‐Gaury, '71a, b). However, interneurons filled from the optic lobes were found to terminate in the same region of dorsal protocerebral neuropile as NCC I and II fibers in Acheta, thus providing a possible pathway for optic input to the cerebral neuroendocrine system.
Cephalic anatomy of a gnathostomatid nematode Echinocephalus sinensis, parasite of oysters and rays
Authors: Ko Ronald C. , Ling J. , Adal M. N.
Published: February 2005

Light, transmission, and scanning electron microscopy of both adult and third‐stage Echinocephalus sinensis shows that the head is characterized by a circular muscle layer in the headbulb wall, a highly unusual arrangement in nematodes. The basal region of cephalic spines is enclosed by all three cuticular zones but the distal region of its shaft is lined only by the cortical layer. The so‐called “ballonet‐cervical sac” system is actually formed by four modified cervical muscle cells of the circomyarian type, each with a liquid cytoplasmic matrix serving as a hydrostatic chamber. The headbulb is deflated by contraction of the circular wall muscle and six pairs of specialized longitudinal and oblique muscles. Two pairs of oblique somato‐oesophageal muscles also serve to shorten the oesophagus. Relaxation of the muscles and an anterior flow of fluid into the cephalic region of the cervical muscle cells inflate the headbulb. In adult worms, the trilobed pseudolabia are lined internally mostly by the oesophageal cuticle. Four radially arranged muscles help to dilate the buccal cavity and the pseudolabia can be retracted into the headbulb by two pairs of oblique muscles inserted at their base. The radial musculature at the anteriormost oesophagus has more abundant and tightly packed myofilaments than other regions. Four pitlike structures of unknown function are located near the base of the pseudolabium. In the third‐stage worm the pyriform pseudolabium is internally lined mostly by the body cuticle. Two rows of bulbous structures each with a central process are located on the headbulb a short distance from the pseudolabium. Two pairs of oblique buccal dilatory muscles help to dilate the oral opening and draw the pseudolabia towards the headbulb. Two bands of oblique myofilaments are present within the anterior‐most region of the oesophagus. The functional adaptation of the cephalic system in relation to the biology of the parasite is discussed.
Nerve elements in the planula of the hydrozoan Pennaria tiarella
Authors: Martin Vicki Joan , Thomas Mary Beth
Published: February 2005

The nerve elements described by light microscopy for the hydrozoan planula have not previously been identified ultrastructurally. This electron microscopic study confirms the presence of two distinct nerve cell types in the planula of the hydroid Pennaria tiarella. Type I nerve cells occur at the base of the ectodermal epithelium just apical to the forming foot processes of the epitheliomuscle cells. The perikaryon contains mitochondria, microtubules, neurosecretory granules, and a prominent Golgi body. Neurites rich in microtubules project from these cells and form a nerve plexus of transversely and longitudinally oriented processes throughout the length of the planula. The Type II nerve cell extends from the free surface of the planula to the mesoglea and bears a single cilium surrounded by long microvilli. The Type I and II nerve cells closely resemble the sensory‐motor‐interneurons and neurosensory cells of Hydra.
Development of dentition and dermal skeleton in embryonicScyliorhinus canicula
Authors: Reif Wolf‐Ernst
Published: February 2005

Serial sections ranging from very young embryos to hatched juveniles and whole embryos ofScyliorhinusshow that dentition and dermal skeleton belong to two independent secondary developmental fields that differ both developmentally and structurally. The development of the dentition starts very early, with a thickening of the ectoderm in the region of the mouth (stage 04), the invagination of the dental lamina (stage 18), and the formation of the germs of the first generation (stage 20). Tooth replacement movements start only near the end of embryogenesis (stage 35). Scale germs, on the other hand, first begin to form at stage 24. Scales erupt shortly before the animal hatches (stage 43). Only one scale generation is formed during embryogenesis. The forces which erupt the scales may come from fluid pressures in vacuoles of the fibrous layer of the dermis. Those which erupt the teeth probably also result from similar fluid pressures. The crown and upper part of the base of scales and teeth are formed by cells of the inner dental epithelium which are differentiated from the ectoderm. They are also formed by odontoblasts which are derived from the vascular layer of the dermis. However, the basal plates of scales and teeth containing the anchoring fibers are formed by osteoblasts, which are derived from the fibrous layer of the dermis.
Cytodiffrentiation in the accessory glands of Tenebrio molitor. VI. A congruent map of cells and their secretions in the layered elastic product of the male bean‐shaped gland
Authors: Dailey Patrick J. , Gadzama Njidda M. , Happ George M.
Published: February 2005

The morphology of the bean‐shaped accessory glands (BAGs) of males of Tenebrio molitor is described. All cells in the secretory epithelium are long and narrow (300–400 mμ × 5 mμ). The seven types of secretory cells are distinguished from one another by the morphology of their secretory granules. Granule substructure varies from simple spheres with homogeneous electrondense contents to complex forms with thickened exterior walls or with crystalline and membranous contents. Individual cell types were mapped by staining whole glands with Oil Red O, and the cell distributions were confirmed by wax histology and ultramicroscopy. The secretions of all seven cell types form a secretory plug composed of seven layers. During mating, the secretory plug from each BAG is forced into the ejaculatory duct by contractions of a sheath of circular muscle. The mirror image plugs from symmetrical BAGs fuse and are transformed into the wall of the spermatophore.
The effects of cold‐stress, hibernation, and prolonged inactivity on bone dynamics in the golden hamster, Mesocricetus auratus
Authors: Steinberg Barry , Singh Inder Jit , Mitchell Ormond G.
Published: February 2005

The effects of cold‐stress and hibernation on bone dynamics in the femurs of hamsters were investigated using histometric analyses. Control animals were maintained at 27° C for 90 days; experimental animals were kept at 5° C and hibernated for 7, 15, 21, 50, or 90 days. Histometric analyses of cross sections indicated that bone diameter and cortical thickness at the femoral midshaft increased after 83 days of extreme cold and 7 days of hibernation but decreased significantly after 69 days of cold stress and 21 days of hibernation. Osteoporosis was evident although the number of osteons per unit area of bone increased during hibernation. An initial decrease in the number of non‐Haversian longitudinal vessels per unit area of bone was seen in experimental animals which was apparently related to a corresponding reduction in cortical thickness. Lacunar area increased in these animals, suggesting that osteocytic osteolysis may be a significant mechanism for calcium regulation during hibernation.
An investigation of the prolactin‐thyroxine synergism in newt limb regeneration
Authors: Hessler Arthur C. , Landesman Richard
Published: February 2005

The use of hormone replacement to support limb regeneration in hypophysectomized newts has been the subject of many investigations. Growth hormone, as well as prolactin (PL) in combination with exogenously supplied thyroxine, have all been shown to he effective. However, the bovine growth hormone used to support limb regeneration was contaminated by prolactin and thyroidstimulating hormone (TSH). The present investigation evaluates the significance of (1) prolactin contamination and (2) endogenous thyroxine synthesis resulting from TSH contamination on limb regeneration in hypophysectomized newts. The effect of supplying exogenous thyroxine was also evaluated. Our studies showed that when hypophysectomized newts were injected with contamination levels of PL and TSH, regeneration occurred, suggesting that the newt's thyroid synthesized sufficient thyroxine to support a prolactin‐thyroxine synergism. The endogenous thyroxine was synthesized by thyroid glands that were indistinguishable from those of saline‐injected, hypophysectomized controls.
Fine structure of the body wall, nervous system, and digestive tract in the Lobatocerebridae Rieger and the organization of the gliointerstitial system in Annelida
Authors: Rieger R. M.
Published: February 2005

The new family Lobatocerebridae, Rieger, contains a group of turbellariomorph worms in the annelid line of evolution. The fine structural organization of the body wall, the digestive tract, and parts of the central and peripheral nervous system are described and the findings are discussed in light of general invertebrate cytology. The epidermis and gastrodermis contain a basal granule cell system which is structurally very similar to the neuroglia cell system of the nervous system. The continuity of the neuroglia cell system, and the epidermal basal granule cell system and the basal granule cell system in the digestive epithelia suggests the existence of a single glial‐basal granule cell system, similar to the gliointerstitial cell system first recognized in the Mollusca (see Nicaise, '73). The Annelida may show a dual (ectodermal and mesodermal) origin of such a gliointerstitial cell system as suggested by similarities in the epidermal basal cell system in the Oligochaeta and of certain epidermal and gastrodermal cells in polychaete regeneration with neuroglia in the Annelida. The structural similarity of neuroglia and basal granule cells in Lobatocerebridae may be the result of similarity in the formation, maintenance, or regulation of the extracellular matrix.
The movements and fusion of the pronuclei at fertilization of the sea urchin Lytechinus variegatus: Time‐lapse video microscopy
Authors: Schatten Gerald
Published: February 2005

The penetration of the sperm into the egg, and the movements of the male and female pronuclei were followed from sperm attachment through pronuclear fusion, using time‐lapse video microscopy of gametes and zygotes of the sea urchin Lytechinus variegatus (23° C). The pronuclei move in four stages: I. Sperm Entry Phase, following sperm‐egg fusion and a rapid radiating surface contraction (5.9 ± 1.3 μm/second) when egg microvilli engulf the sperm head, midpiece, and tail to form the fertilization cone and the sperm tail beats in the egg cytoplasm; II. Formation of the Sperm Aster, which pushes the male pronucleus centripetally at a rate of 4.9 ± 1.7 μm/minute starting 4.4 ± 0.5 minutes after sperm‐egg fusion, as the male pronucleus undergoes chromatin decondensation; III. Movement of the Female Pronucleus, the greatest and fastest of the pronuclear motions at a rate of 14.6 ± 3.5 μm/minute at 6.8 ± 1.2 minute after sperm‐egg fusion, which establishes the contact between the pronuclei; and IV. Centration of the Pronuclei to the egg center at a rate of 2.6 ± 0.9 μm/minute by 14.1 ± 2.6 minutes after sperm‐egg fusion. Pronuclear fusion typically occurs after stage IV and proceeds rapidly starting 14.7 ± 3.6 minutes after sperm‐egg fusion with the male pronucleus coalescing into the female pronucleus at a rate of 14.2 ± 2.6 μm/minute.
Heterochronic mechanisms of morphological diversification and evolutionary change in the neotropical salamander, Bolitoglossa occidentalis (Amphibia: Plethodontidae)
Authors: Alberch Pere , Alberch Jordi
Published: February 2005

Bolitoglossa occidentalis, a lowland salamander of Mexico and Guatemala, has a highly derived morphology. The features that are derived with respect to the condition in generalized members of the genus include the following: (1) small body size; (2) short tail; (3) fully webbed hands and feet; (4) reduction and loss of certain phalangeal elements; (5) fusion of carpals and tarsals; (6) absence of prefrontal bones; and (7) reduced skull ossification. The ontogeny of this species was analyzed quantitatively and compared with the patterns of growth and differentiation encountered in two morphologically generalized members of the genus, B. rostrata and B. subpalmata. Most of the derived features can be explained by invoking a single heterochronic process: truncation of development at a small size (most likely the product of early maturation). Therefore, B. occidentalis is a paedomorphic species whose morphology has been attained through the process of progenesis. This result supports Alberch's ('80a) prediction, based on functional analysis, that the principle adaptation to arboreality in B. occidentalis is small size; other derived morphological features are associated with the organism's truncated development and may have no adaptive significance. However, patterns of dissociation are found within this overall progenetic process. Some of these include the following: (1) accelerated growth rates of the metatarsals and first phalanges, and retarded growth rates of the second and third phalangeal elements; (2) dissociation between rates of ossification of the skull and the autopodial elements; and (3) dissociation between the timing of termination of the process of shape change during the ontogeny of the foot (the product of differential growth between digital and interdigital areas) and termination of growth in overall foot size (foot surface area). This later result illustrates the independence of morphogenetic phenomena (shape change) from processes of growth (size increase).
Structure, histochemistry, ontogenetic development, and regeneration of the ocellus of Cladonema radiatum dujardin (cnidaria, hydrozoa, anthomedusae)
Authors: Weber Christian
Published: February 2005

The ectodermal eyes, 45–55 μm in diameter, of the cnidarian hydrozoan Cladonema radiatum Dujardin possess a lens approximately 15 μm in diameter enveloped by an eyecup (retina). An overlying layer of intensely vacuolated distal process of the adjoining epithelial cells forms a transparent cornea. The eyecup is composed of three cell types: basal cells, melanin‐containing pigment cells, and photoreceptor cells. The last two cell types occur in the ratio of approximately 2:1. Histogenesis of the eye both during ontogeny and regeneration is described from light and electron microscopic investigations. During ontogeny the cell types forming the retina are derived from a compact group of morphologically undifferentiated cells, but during regeneration a primordium is formed by regeneration cells. In both cases the lens is built from distal nonnucleated cytoplasmic portions pinched off from the pigment cells. The cornea is formed by distal lamellar processes of the ocellus adjoining the epithelial cells. Through EM‐histochemical methods (silver impregnation and DOPA‐oxidase reaction) the pigment of the chromatophores of the retina was identified as melanin.
The myth of intercalary segment in insect head
Authors: Singh Sawai
Published: February 2005

Embryonic development of the head of Oxyrhachis tarandus (Membracidae) has been investigated in detail to settle the controversy of head segmentation and to refute the occurrence of an intercalary segment. The head is formed from six distinct elements: the prostominal lobe, the paired cephalic lobes, the antennal segment and the three noncontroversial gnathal segments. The prostomial lobe, which possesses a neuromere and a pair of coelomic cavities, represents the first body segment, called the prostomial segment. The tritocerebral lobes of the brain and the stomatogastric nervous system, consisting of a frontal ganglion, clypeolabral nerves, and the recurrent nerve etc., develop from the neuromere of the prostomial lobe. The tritocerebrum thus belongs to the prostomial segment rather than to an imaginary intercalary segment and mainly represents the ganglionic center of the stomatogastric nervous system in the brain. Frons, clypeus, and labrum develop from the outer wall of the prostomial lobulate plate, whereas the epipharyngeal wall, including the cibarial pump, develops from its inner wall. The presence of three coelomic cavities and of three distinct neural masses in the cephalic lobes during the initial stages of development shows that they have developed by the fusion of three distinct segments during the long phylogenetic history of insects. The portion of the germ band presently considered as the intercalary segment is actually the sternal part of the antennal segment. The neural cells located in this region give rise to the deutocerebrum by shifting forward, around the stomodaeum, and always leaving a commissure behind. The intercalary segment is thus a complete illusion. The antennal segment is postoral in the beginning and bears a pair of coelomic cavities, but later on it shifts forward and its sternal part invaginates into the stomodaeum.
Structure and functional aspects of the scotopic compound eye of the sugarcane borer moth
Authors: Miskimen George W. , Rodriguez Nilda L.
Published: February 2005

Morphology and functional aspects of the scotopic compound eye of the moth Diatraea saccharalis, studied using light and electron microscopy, is presented. An ommatidium is composed of a laminate corneal lens, four Semper cells, a refractive cone, two primary pigment cells, six screening pigment cells, a crystalline tract that functions as an optical waveguide, and six to eight sensory retinular cells. Accessory light regulators consist of screening pigment cells that, in the dark‐adapted position, increase receptor sensitivity by permitting light rays to cross over to adjacent ommatidia and specialized tracheal regions that enhance sensitivity by reflecting light back toward sensory receptors.
Reptilian bone marrow. An ultrastructural study in the spanish lizard, Lacerta hispanica
Authors: Zapata A. , Leceta J. , Villena A.
Published: February 2005

The ultrastructure of hemopoietic bone marrow of the Spanish lizard, Lacerta hispanica, has been studied for the first time. The organ consists of a stroma formed by venous sinuses and reticular cells. Erythropoiesis takes place in the lumen of blood vessels, while granulopoiesis is extravascular. Pluripotent stem cells are structurally differentiated into erythrocytes and granulocytes. Two types of granulocytes, heterophils and acidophils, have been found, and a third granular cell type is tentatively identified as granular leukocyte. Remarkably, plasmacytopoiesis occurs in the bone marrow of Lacerta hispanica. The possible functional significance of these results is discussed with emphasis on their importance for the reptilian immune system.
Ultrastructure of the wax‐gland system in subterranean scale insects (homoptera, coccoidea, margarodidae)
Authors: Foldi Imré
Published: February 2005

The ultrastructure of wax glands (integumentary, stigmatic, and peristigmatic glands) was investigated in larvae, cysts, and adult females and males of species belonging to the genera Porphyrophora, Sphaeraspis, and Eurhizococcus. The general organization and cytological characteristics are similar for all glands studied. Each gland is composed of a single layer of 8 to 40 cells. The glandular cells are characterized by a very large quantity of smooth endoplasmic reticulum which forms dense zones throughout the cytoplasm, but is always placed near the collecting canals in the presence of mitochondria. Each cell has a central canal reservoir which penetrates it deeply and gives rise to a large number of lateral collecting canals, formed by the invagination of the apical plasma membrane. The canals open into a subcuticular cavity forming a common reservoir in which the secretion is accumulated. This reservoir is covered by a modified cuticle formed from the endocuticle and the epicuticle. The endocuticle is composed of a network of fine tubular structures and has many filaments on its surface. The epicuticle is perforated by numerous pores. There is no cuticular duct. The secretion crosses the cuticle in three successive steps. First, it passes through the filaments, then through fine tubular structures of the endocuticle, and finally through the epicuticular pores.
A three dimensional serial reconstruction of neuronal distributions in the hypostome of a Hydra
Authors: Kinnamon John C. , Westfall Jane A.
Published: February 2005

The numbers, types, and distributions of neurons in a hypostome of Hydra littoralis were determined from electron micrographs of serial (0.25 μm thick) sections. In 1,080 serial sections examined we found 75 sensory cells and 949 centrally located ganglion cells. More than 96% of the 1,024 neurons identified had a single cilium.

Sensory cells were most numerous near the apex of the hypostome. Proceeding away from the apex, they steadily decreased in numbers; at 120 μm they were no longer observed. Ganglion cells were bimodally distributed; some were associated with sensory cells at the apex, but most were found at the sites of tentacle origin.

We observed, throughout the hypostome, a total of 64 neuronal clusters (three or more contiguous neurons), with an average of five and a maximum of 11 neurons in a cluster. Clusters were distributed similarly to ganglion cells: an initial concentration of clusters near the apex; the majority at the hypostometentacle junctions.

Each neuron identified was traced through succeeding sections in which it was observed. We used a three coordinate system to create a three‐dimensional reconstruction of the neuronal locations in the hypostome. Although the functional significance of the neuronal distributions we observed is unknown, we suggest that neurons at the apex of the hypostome transduce sensory information involved in feeding behavior. The neuronal concentrations at sites of tentacle origin may be responsible for initiating Contraction Burst Pulses associated with rhythmic behavioral patterns of Hydra or coordinating tentacle movements involved in prey capture, ingestion or locomotion.
The hand of two ‐toed sloths (Choloepus): Its anatomy and potential uses relative to size of support
Authors: Mendel Frank C.
Published: February 2005

Hands of two‐toed sloths (Choloepus) are long, narrow, hook‐like apparatuses with only two functional digits (II and III); rays I and IV are represented only by metacarpals. The proximal phalanges of digits II and III are shortened to essentially proximal and distal articulating surfaces, and all but distal interphalangeal joints of these digits are restricted by interlocking surfaces to minimal ranges of flexion and extension. Several intercarpal joints and the wrist joint, however, allow wide ranges of movement in several axes. Wide excursion at the wrist is permitted by an extremely lax joint capsule, the manner of insertion of several prime movers of the carpus, and the reduced participation of the ulna in the wrist joint. Several extrinsic digital muscles, particularly extensors, are absent and others have unusual actions. Intrinsic musculature consists primarily of mm. interossei and m. extensor digitorum brevis, although other, inconstant muscles do occur. Hands of Choloepus are used as flexible hooks on supports less than 52 mm in diameter and as fixed grapnels on larger supports. In both cases, distal phalanges (and covering claws) form the “hook” element. Whereas bare volar pads seem to be adjunctive on supports smaller than 52 mm in diameter, they are essential on those larger than 65 mm. Two‐toed sloths may prefer supports 50 mm in diameter or smaller. The potential importance of vines as supports is discussed.
A crustacean statocyst with only three hairs: Light and scanning electron microscopy
Authors: Rose R. D. , Stokes D. R.
Published: February 2005

Standard histological and SEM techniques have been used to examine the pair of statocyst organs located in the telson of the isopod, Cyathara polita. Each organ is formed as an invagination of the dorsal cuticle of the telson. The invagination narrows to form a stalk between the statocyst and dorsal surface. A canal courses longitudinally through this stalk and forms a continuous channel between the lumen of the cyst and the external environment. On the luminal floor of each statocyst, there are three pits; each correlates with a nodule protruding from the ventro‐medial wall. From each pit, a single, bifurcating hair projects dorsally to contact the single concretion within the statocyst lumen. No other static organs have been found in this animal. Thus, maintenance of equilibrium in this species appears to be under the control of but six hairs, three in each statocyst. Innervation of each statocyst is provided by a branch of a nerve which connects anteriorly with the last abdominal ganglion.
The larval chondrocranium of Pelodytes punctatus, with a review of tadpole chondrocrania
Authors: Sokol Otto M.
Published: February 2005

The larval chondrocranium of the pelobatoid anuran Pelodytes punctatus was studied, using Alcian blue‐alizarin stained and cleared whole preparations, serial sections, and gross dissections. This beaked tadpole is an unspecialized pond dweller and its chondrocranium closely resembles those of other ecologically similar tadpoles of diverse systematic relationships. Detailed analysis, however, shows many differences among the chondrocrania of anuran larvae. Among other features, these include the configurations of suprarostrals, fronto‐parietal fenestrae, palatoquadrate suspensoria, the ligamentum or cartilago tectum of the muscular process of the quadrate and the circumoral ligaments. The lateral circumoral ligament permits differentiation of beaked discoglossoidean and ranoidean larvae. Microhyloids conform to the ranoidean pattern in this feature. Pipoids either lack it or seem to conform to the discoglossoidean pattern. Use of these larval features as key characters enables assignment of Pelodytes to an uncertain position among pelobatoid frogs. This is totally congruent with previous assignments based on adult features and is used to support the hypothesis that anuran phylogenies based on larval characters will closely resemble, in major features at least, those based solely on adult characters.
Primary palatal development in the chick
Authors: Will Leslie A. , Meller Samuel M.
Published: February 2005

Seventy‐nine chick embryos were examined by light microscopy and scanning electron microscopy to determine the mechanism of primary palatal development. Fusion between two discrete processes, the medial nasal and maxillary prominences, was found to be necessary for formation of a complete primary palate. This was one component of a three‐stage process that included: (1) invagination of the nasal pit prior to the appearance of the facial prominences; (2) fusion between the medial nasal and inaxillary processes caudal to the nasal groove; (3) rupture of the bucconasal membrane. The lateral nasal and maxillary prominences were found to be part of the same tissue mass. Mergence was proposed as a mechanism for the obliteration of the groove between these two localized prominences. These results were compared with those obtained by other authors for primary palate formation in rodents and man.
Morphology of the pineal organ in the salamander Ensatina eschscholtzi
Authors: Hetherington Thomas E.
Published: February 2005

The pineal organ of Ensatina eschscholtzi, a terrestrial and secretive species of salamander of the family Plethodontidae, is a photoreceptive structure lying on the dorsal surface of the diencephalon. The pineal is flattened with a broad lumen and consists of three cell types: photoreceptors, supportive cells, and neurons. Pineal photoreceptors are typical vertebrate photoreceptors and possess outer segment formations which, however, are frequently contorted and disorganized. Sloughing of apical portions of outer segments and vesiculation along the lateral edges of outer segment membrane disks are consistently observed and presumed to represent mechanisms of outer segment membrane recycling. Photoreceptors have basal processes which synapse with neural dendrites. Synapses between photoreceptor basal processes are occasionally observed. All synapses are characterized by synaptic ribbon structures of variable number, size, and configuration. Dense‐core vesicles are occasionally observed mingled with clear synaptic vesicles within photoreceptor basal processes. Supportive cells within the pineal function in phagocytosis and recycling of shed outer segment membrane material, and neurons are localized at the lateral margins of the organ. The latter send axons into the ipsilateral side of the dorsal diencephalon. The pineal organ of Ensatina shows marked variation in overall size (cell total), cell type proportions, absolute neuron number, and ratio of photoreceptor number to neuron number for individual pineals. None of these morphological parameters is correlated with body size, sex, or season, and it is assumed that such variability represents significant variation in photosensory capabilities. It is suggested that the pineal organ of Ensatina is a partially degenerate photoreceptive structure.
Comparative analysis of the development of the lizard, Liolaemus tenuis tenuis. II. A series of normal postlaying stages in embryonic development
Authors: Lemus D. , Illanes J. , Fuenzalida M. , De La Vega Y. Paz , Garcia M.
Published: February 2005

In this work, we have completed a study of the development of the ovoviviparous lizard Liolaemus tenuis tenuis. Ovoviviparity in this lizard is a condition in which eggs are retained within the reproductive duct for about 60 days. During this period the phases of segmentation, gastrulation, neurulation, presomitic, and somitic embryos transpire. During the months of December and January the eggs are laid, and at this time the embryos are comparable to stage 27 Liolaemus gravenhorsti lizard embryos, or to stage 29 Calotes versicolor lizard embryos. Differentiation of the facial region occurs between Days 12 and 42 after egg laying. Limbs develop rapidly between the 8th and 23rd days. By 53 days the appendicular skeleton is completely formed. After 36 days the mesonephros begins to degenerate, and its function is gradually taken over by the developing metanephros. Newborn lizards do not possess an egg caruncle. During the period up to hatching, there is a great increase of liquid within the egg, presumably amniotic fluid. Cracks develop in the leathery shell shortly before hatching and are, perhaps, the first sign of the onset of hatching. Increase of liquid in the egg during postlaying development accounts for its increase in weight and change in shape. Weight of the embryo at hatching does not exceed 32% of the total weight of the egg.
Histochemistry of lower vertebrate calcified structures. I. Enamel of the dogfish Squalus acanthius compared with mammalian enamel and homologous dentine
Authors: Everett Mona M. , Miller William A.
Published: February 2005

The enameloid and dentine of Squalus acanthius have been compared histochemically with those of Bos taurus. Squalus enameloid is much less reactive to a variety of stains or reagents than dentine or bovine immature enamel but it does have positive reactions with picromethyl blue, Mallory's and Van Gieson's stains, and Alcian blue. It stains faintly with Biebrich scarlet, indicating some anionic groups. Specific reactions for tyrosine, tryptophane, lysine, histidine, arginine, and cysteine are negative. Bos immature enamel is positive for cationic, anionic, and aromatic reactive groups by all test procedures, and dentine was positive for the anionic components. Bovine maturing enamel, however, is more similar in terms of lack of reactivity to Squalus enameloid but differed because the bovine enamel was moderately positive for tyrosine; tryptophane, and anionic groups and negative with Mallory's picromethyl blue and Van Gieson's stains. A fibrous transitional area between Squalus dentine and enameloid has staining reactions characteristic of both collagen and keratins.
Observations on the morphology and histochemistry of the foregut muscles of spiders (Arachnida: Araneida)
Authors: Meyer Wilfried
Published: February 2005

The morphology of the foregut muscles of five spider families (Theraphosidae, Agelenidae, Araneidae, Lycosidae, Salticidae) was described, and the individual fibre numbers and fibre cross diameters of the muscles were determined. The nomenclature of these muscles was reviewed and modified if necessary.

Oxidative enzyme and myosin‐ATPase histochemistry revealed eight dilatatory muscles of the foregut to consist of slow (type I) fibres, while fast fibres (type IIB), and intermediate fibres, were only to be found in the two other muscles of the foregut, and in the remaining prosomal muscles (type IIA fibres around the poison gland).

The eight sucking muscles proper of the foregut also showed stronger activities of transmitter metabolizing enzymes [monoamine oxidase, glutamate dehydrogenase(NAD)], and comparatively distinct amounts of glycogen and lipids.
Arterial circulation of the spinal cord and brain in the monodontidae (Order cetacea)
Authors: Vogl A. W. , Fisher H. D.
Published: February 2005

In this paper we document retial supply of the spinal cord and describe the arterial vascular pattern of the brain in the whale family Monodontidae. Observations are based on gross dissections of four brains, two each of Monodon monoceros and Delphinapterus leucas, and one spinal cord from M. monoceros.

Vessels of the spinal cord arise from extradural retia in the neural canal. Arteries originating from the retia penetrate the dura between successive spinal roots (mainly ventral) and not in association with them, unlike radicular arteries of other mammals. Also, these vessels are uniformly distributed and contribute equally to a plexus surrounding the cord. An A. radicularis magna is not present, and neither are dìstinct anterior or posterior spinal arteries.

Circulation to the brain is effected by two pairs of arteries originating from intracranial retia. The rostral pair supplies most of the forebrain (prosencephalon), whereas the more caudal pair supplies mainly the midbrain (mesencephalon) and hindbrain (rhombencephalon). The circulatory pattern is characterized by (1) complete independece of anterior cerebral arteries (no anastomoses); (2) extensive cortical supply by the anterior choroidal arteries; (3) absence of subdural communicating vessels between rostral and caudal trunks; (4) union of caudal trunks to form a small basilar artery; and (5) absence of vertebral arteries and hence of a vertebral basilar system. There are some obvious differences between subdural arteries in the Monodontidae and those in other mammals; however, their general patterns of distribution are similar, and we suggest that most of the vessels, at least in the cranium, are homologous.
Fiber type composition and postmetamorphic growth of anuran hindlimb muscles
Authors: Sperry David G.
Published: February 2005

Fiber type composition distinguished by the level of succinic dehydrogenase, mean fiber diameter, and fiber number were determined for the gracilis major and sartorius in ontogenetic series of the anurans Rana pipiens, Bufo americanus, and Xenopus laevis to characterize muscle composition and mode of muscle growth.

A correlation can be made between the respective locomotor mode of these anurans, their activity physiology, and the fiber type composition of the propulsive muscles. R. pipiens and X. laevis have hindlimb muscles composed primarily of fast‐twitch, fast‐fatiguing type 1 fibers. B. americanus's muscles are composed of slow‐twitch, slow‐fatiguing type 2 and type 3 fibers. Fiber typing is apparently useful in explaining interspecific anuran locomotor capability previously difficult to correlate with body shape. Fiber typing also affords an explantion for reported variations in metabolism during strenuous activity.

Postmetamorphically, anuran muscles grow by a combination of hyperplasia and hypertrophy, but the percent fiber type composition remains unchanged. In R. pipiens and X. laevis, the muscles grow primarily by hypertrophy with the addition of relatively fewer fibers. The converse is true for B. americanus. In all three species the combinations result in strong positive allometric increases in muscle cross section. Anuran muscle growth is similar to that reported for fish and different from that associated with mammals.
The organization and structure of nerve and muscle in the jellyfish Cyanea capillata (coelenterata; scyphozoa)
Authors: Anderson Peter A. V. , Schwab Walter E.
Published: February 2005

The perirhopalial tissue and swimming muscle of Cyanea were examined with light microscopical and electron microscopical techniques. The perirhopalial tissue is a thin, triangular septum found on the subumbrellar surface of the animal. It separates part of the gastric canal system from the surrounding seawater, and is bound on two sides by radial muscle bands and on the third, the shorter side, by a rhopalium and the margin of the bell.

The ectoderm of the perirhopalial tissue is composed of large, somewhat cuboidal, vacuolated, myoepithelial cells. The muscle tails of these cells form a single layer of radial, smooth muscle. Neurons of the “giant fiber nerve net” (GFNN), which form an extensive net over the perirhopalial tissue, lie at the base of the vacuolated portion of the myoepithelial cells. These neurons are visible in living tissue. The morphology of individual GFNN neurons was examined following intracellular injection of the fluorescent dye Lucifer Yellow. The neurons are usually bipolar and free of branches. At the electron microscope level, one usually finds that the GFNN neurons contain large vacuoles. The other characteristic feature of these cells is that they form symmetrical, or nonpolarized, synapses; that is, synaptic vesicles are found on both sides of the synapse.

The swimming muscle is striated and composed of myoepithelial cells. Each myoepithelial cell has several muscle tails, and those of adjacent cells are linked to gether by desmosomes. The endoderm of the perirhopalial tissue also was examined.

This investigation of the organization and ultrastructure of the perirhopalial tissue and surrounding muscle was undertaken to provide essential background information for an ongoing physiological study of the GFNN neurons and their synapses.
Rosette glands in the gills of the grass shrimp Palaemonetes pugio. II. Premolt ductule reformation: Replacement of ciliary processes by cytoplasmic processes in relation to gland maturation
Authors: Doughtie Daniel G. , Rao K. Ranga
Published: February 2005

The events associated with premolt reformation of the cuticularized ductule in the underdeveloped (immature) branchial rosette glands, which are common in the gills of small (14–18 mm, total length) grass shrimp, are described and contrasted with the events of ductule reformation in the fully developed (mature) resette glands most common in larger shrimp. In immature rosette glands, two ciliary processes emerge from each of the component secretory cells and ascend into the basal luminal region of the old ductule. Subsequently a new ductule is formed around the old ductule, and the ciliary processes disappear, either because of degeneration or retraction. The transitory ciliary processes appear to prevent the old ductule from collapsing during the formation of a new ductule. Such transitory ciliary processes, however, are not found in association with premolt ductule reformation in the mature rosette glands; in their place are seen a number of microvilli‐like cytoplasmic processes, which emanate from the apices of the secretory cells and from the channels of the central cell. These cytoplasmic processes in mature glands, like the ciliary processes in immature glands, are transitory and appear to prevent the collapse of the old ductule.

Cytoplasmic processes comparable to those in mature glands, but relatively few in number and originating only from the secretory cells, are seen together with ciliary processes in some immature glands. The relative abundance of cytoplasmic processes in the mature glands, coupled with the observation that transitory ciliary processes occur in immature glands but not in mature glands, suggests that, during glandular maturation, transitory ciliary processes are replaced by transitory cytoplasmic processes.
Morphology and distribution of chromaffin cells in the adrenal gland of cordylidae (Reptilia, Sauria): A comparative study
Authors: Laforgia Vincenza , Varano Lorenzo
Published: February 2005

The distribution of the adrenaline and noradrenaline chromaffin cells in the adrenal glands of 10 members of the family Cordylidae have been examined. In the genus Gerrhosaurus, all the catecholamine cells lie on the surface of the adrenal gland, forming a continuous envelope of one or two layers of cells that mainly contain noradrenaline (NA). In the genus Platysaurus, the chromaffin envelope is intermittent. There are relatively large tracts of interspersed interrenal tissue containing some adrenaline cells (A). Islets of chromaffin cells are scattered between these interrenal tracts. In the genus Pseudocordylus and the genus Cordylus, the superficial chromaffin cells tend to gather into a multilayered dorsal mass, containing mainly NA cells. Inside the interrenal parenchyma, there are always numerous chromaffin islets, containing mainly A cells.