bluuebunny/crossref_metadata_2025_split huggingface dataset:
Muscular mechanisms of snake locomotion: An electromyographic study of lateral undulation of the florida banded water snake (Nerodia fasciata) and the yellow rat snake (Elaphe obsoleta)
Authors: Jayne Bruce C. 
Published: February 2005

AbstractElectromyography and cinematography were used to determine the activity of epaxial muscles of colubrid snakes during terrestrial and aquatic lateral undulatory locomotion. In both types of lateral undulation, at a given longitudinal position, segments of three muscles (Mm. semispinalis‐spinalis, longissimus dorsi, and iliocostalis) usually show synchronous activity. Muscle activity propagates posteriorly and generally is unilateral. With each muscle, large numbers of adjacent segments (30 to 100) show simultaneous activity. Terrestrial and aquatic undulation differ in two major respects. (1) During terrestrial undulation, muscle activity in a particular region begins when that portion of the body has reached maximal convex flexion and ends when it is maximally concave; this phase relation is uniform along the entire snake. During swimming, however, muscle activity passes posteriorly faster than the wave of vertebral flexion, causing the relation of muscle activity to flexion to change along the length of the snake. (2) In the terrestrial mode, the block of active muscle segments remains approximately constant in size as it passes down the snake, whereas during swimming the number of adjacent active muscle segments increases posteriorly. Despite the fact that Elaphe obsoleta has nearly twice as many body vertebrate as Nerodia fasciata (240 vs. 125), the only difference observed in the swimming of these two species is that a larger number of adjacent muscle segments is simultaneously active in comparable regions of Elaphe obsoleta than in Nerodia fasciata.
Transmission electron microscopic study of the saccule in the embryonic, larval, and adult toadfish Opsanus tau
Authors: Sokolowski Bernd H. A. , Popper Arthur N. 
Published: February 2005

AbstractThe development of the sensory epithelium of the saccular macula of Opsanus tau was studied with transmission electron microscopy. In the 10–12 somite embryo all cells of the newly formed otocyst are morphologically undefined, having an apically placed cilium with an underlying basal body and parabasal body. Junctional complexes are characterized primarily by tight junctions and a few desmosomes. In the 17‐somite embryo the sensory cells begin to differentiate and are definable by the development of microvilli, which lack a cuticular plate. When the embryo has approximately 25–30 somites, ganglion cells differentiate and send their nerve processes toward the thin, disrupted basal lamina and the developing rhombencephalon. Desmosomes are more definable in the sensory regions at this age.As the myotomes begin forming (approximately 5–8 days before hatching), the nerves invade the sensory epithelium, and the developing sensory cells contain dense bodies surrounded by clear, membrane‐bound vesicles. Clear synapticlike vesicles are also found throughout the infranuclear region of the sensory cells. However, afferent fibers lack a postsynaptic density. Three to 6 days prior to hatching a cuticular plate begins forming under the ciliary bundles and support and peripheral cells begin to morphologically differentiate. Two to 4 days before hatching the cuticular plate is well formed, desmosomes are numerous, afferent synapses and complete, and the sensory cells are in the upper two‐thirds of the epithelium. Seven to 10 days after hatching, sensory cells have efferent synapses and ganglion cells and nerves show a myelin coat. These results suggest that sensory cells begin their development prior to VIIth nerve innervation, although the orientation and pattern development of these cells may be related to the formation of the cuticular plate, desmosomes, afferent innervation, and basal lamina formation.
Morphology and locomotor adaptations of the bovid femur in relation to habitat
Authors: Kappelman John 
Published: February 2005

AbstractExtant bovids inhabit a wide diversity of environments that range from forest to savanna and display locomotor patterns that are habitat specific. I report here on an investigation of the linkage between these locomotor patterns and habitat based on a study of the morphology of the bovid femur. Femoral head shape, shaft dimensions, and knee structure are examined and support a statistically significant separation of the different morphological complexes present in bovids from forest, broken cover, and savanna habitats. Morphological differences are primarily related to locomotor patterns as reflected in the degree of cursoriality displayed by bovids in different habitats. Cursorial bovids from savanna environments have laterally expanded femoral heads that act to limit the degree of abduction and axial rotation at the hip, and elliptically shaped distal femora that increase the moment arm of the extensor muscles that cross the knee. Forest bovids have spherically shaped femoral heads. This morphology permits a much higher degree of abduction and axial rotation at the hip and appears to provide greater maneuverability in a vegetationally complex habitat. Bovids living in broken cover environments that fall between the extremes of closed canopy forest and savanna display an intermediate set of femoral characters. This approach to the relationship between habitat and locomotion offers a potentially powerful means with which to examine the interplay between structural form and function in bovid evolution.
Anatomy and function of the mouthparts of the biting midge, Culicoides sanguisuga (Diptera: Ceratopogonidae)
Authors: Sutcliffe James F. , Deepan Paul D. 
Published: February 2005

AbstractThe mouthparts and upper food canal of the biting midge, Culicoides sanguisuga, are described with light, scanning electron, and transmission electron microscopy. The stylets (labrum, hypopharynx, mandibles, laciniae) are individually described so that their union into the piercingsucking syntrophium can be understoo. Labial anatomy and relationships to the syntrophium are also described. Syntrophial integrity is based on a complex system in which (1) the mandibles articulate with each other and with the hypopharynx; (2) the edges of the labrum are hooked over the sides of the mandibles; (3) the laciniae “clasp” the hypopharyngeal‐mandibular complex to the labrum; and (4) the labellum holds the stylets together terminally.We propose that all muscles attached to the mandibles of the biting midge serve as retractors. This, combined with the fact that the mandibles have only one toothed edge (rearward‐directed teeth on the lateral edge), suggests that retraction is the only active cutting stroke during biting. The mechanism contrasts with that of black flies (simuliids), which have mandibular protractors and retractors and teeth on both lateral and medial mandibular margins.
Ear morphology of the frog‐eating bat (Trachops cirrhosus, family: Phyllostomidae): Apparent specializations for low‐freqency hearing
Authors: Bruns Volkmar , Burda Hynek , Ryan Michael J. 
Published: February 2005

AbstractThe frog‐eating bat (Trachops cirrhosus) is unusual among bats studied because of its reliance on low‐frequency (<5 kHz) sounds emitted by frogs for prey localization. We investigated the ear of this bat in order to identify anatomical features that might serve as adaptations for low‐frequency hearing. Trachops cirrhosus has a variety of anatomical features that might enhance low‐frequency hearing, either by increasing sensitivity to low‐frequency sounds or expanding the total frequency range to include lower frequencies. These bats have long pinnae, and a long and wide basilar membrane. The basal portion of the basilar membrane is much stiffer than the apical portion, and the basal portion of the tectorial membrane is more massive than the apical portion. There is also a concentration of mass in the apical portion of the cochlea. T. cirrhosus possesses the largest number of cochlear neurons reported for any mammal, the second highest density of cochlear neurons innervation known among mammals, and three peaks of cochlear neuron density. Other bats have two peaks of cochlear neuron density, lacking the apical concentration, while other mammals usually have only one. T. cirrhosus differs from most other small mammals and bats in characteristics of the apical portion of the cochlea, i.e., that area where the place theory of hearing predicts that low frequencies are detected.
Architecture and consequent physiological properties of the semitendinosus muscle in domestic goats
Authors: Gans Carl , Loeb Gerald E. , de Vree Frits 
Published: February 2005

AbstractMorphological and physiological analyses confirm that the semitendinosus muscle of goats contains two separate compartments in series, each with distinct innervation. These compartments of the muscle are in turn composed of short fibers (approximately four fibers in series in the proximal compartment and seven to eight fibers in the distal compartment) which overlap each other for more than 30% of their length, with much of the overlapping portions consisting of slender tails that terminate at one‐tenth of the midfiber diameter. Groups of fibers are associated into relatively narrow bands that run end‐to‐end in each compartment. The data suggest that the maximum length of muscle fibers may be limited; even the fibers of parallelfibered muscles may not scale with the dimension of the animal.
Sex differentiation and early gonadal development in Bombina orientalis (anura: Discoglossidae)
Authors: Lopez Kristin 
Published: February 2005

AbstractGonadal differentiation in premetamorphic Bombina orientalis is described and staged. The pattern of events during differentiation in Bombina differs in several respects from that previously described in other anurans. The Bombina gonad initially develops on the ventral surface of the vena cava, where there is no pre‐existent somatic genital ridge prior to the arrival of the germ cells. The sexually undifferentiated gonad does not have a distinct cortex and medulla; instead, medullary cells ingress from the mesonephric blastema during sexual differentiation. Formation of a testis or an ovary appears to depend on the ability (or lack of ability) of the medulla to invade the germ cell‐containing cortex. In the germ line, sexual differetiation can be recognized by a premeiotic increase in oogonial cell volume.
Mechanics of drinking in the mallard (Anas platyrhynchos, anatidae)
Authors: Kooloos J. G. M. , Zweers G. A. 
Published: February 2005

AbstractWater drinking in the mallard is accomplished by a fine‐tuned set of movements of upper and lower jaw and of the tongue. During immersion of the tips of the bill, the oral cavity is formed into smaller volumes containing water and into connecting tubes. Two mechanisms serve the water transport: (1) lingual and jaw movements press water from the water‐containing spaces into the tubes; (2) a quantitative simulation of the shape of the oral cavity during immersion shows that the two tubes are so narrow that capillary action also contributes to water transport.Thereafter, the tips of the bill are raised until they point upward. In this “tip‐up” position, water flows into the esophagus because of gravity. We conclude that, in addition to normal tip‐up drinking observed in almost all Passeriformes and Galliformes, a second type of tip‐up drinking may be distinguished in Anseriformes. The integration of the drinking mechanism, keeping the water inside the mouth, and the straining mechanism, expelling the water along the beak rims, is effected by specific actions of the elaborate lingual apparatus.
Pituitary gland of the garter snake (Thamnophis): Morphology and immunocytochemistry
Authors: Wurst Gloria Z. , Pearson Anita K. , Licht Paul 
Published: February 2005

AbstractThe three‐dimensional gross morphology of the pituitary gland of the garter snake (Thamnophis sirtalis) is presented. Hormone‐producing cells of the pars distalis were localized immunocytochemically. Corticotropes and lactotropes occur in the anterior two‐thirds of the gland; corticotropes are especially numerous in the area of the pars distalis nearest the median eminence, and lactotropes are most abundant medially. Somatotropes are restricted to the posterior one‐third of the pars distalis. Gonadotropes and thyrotropes are scattered throughout the pars distalis and in favorable sections form a network of cells enclosing clusters of peptide‐secreting cells.
Effect of photoperiod on testicular function in blinded and non‐blinded marbled newts, Triturus marmoratus (caudata, salamandridae)
Authors: Fraile Benito , Paniagua Ricardo , Rodriguez Marina C. , Saez Francisco José 
Published: February 2005

AbstractAdult male marbled newts (Triturus marmoratus) were collected at the beginning of the spermatogenetic period and exposed to different photoperiods (natural photoperiod with progressively increasing daylengths, total darkness, 8L:16D, 12L:12D, 16L:8D, and continuous light) for 3 months at 20°C. To evaluate the effect of photoperiodic input via pineal gland photoreceptors, two additional groups of newts were blinded by a non‐aggressive method (an elastic rubber cap was adjusted to the head to cover the eyes but not the pineal photoreceptors). These animals were exposed either to the natural photoperiod or to 12 hr of light per day. Quantitative histologic studies on testicular development and germ‐cell volume revealed no significant differences between non‐blinded and blinded animals. Testicular size and germ‐cell development increased in the following order: total darkness, constant light, 8L:12D, natural photoperiod, 12L:12D, and 16L:8D. These results suggest that (1) long photoperiods enhance testicular development, whereas short photoperiods or an environment of continuous light have the opposite effects and (2) the effect of photoperiods on testicular function in newts is independent of the ocular photoreceptors.
Functional morphology of the pharyngeal jaw apparatus in perciform fishes: An experimental analysis of the haemulidae
Authors: Wainwright Peter C. 
Published: February 2005

AbstractA new mechanical model for function of the pharyngeal jaw apparatus in generalized perciform fishes is developed from work with the family Haemulidae. The model is based on anatomical observations, patterns of muscle activity during feeding (electromyography), and the actions of directly stimulated muscles. The primary working stroke of the pharyngeal apparatus involves simultaneous upper jaw depression and retraction against a stabilized and elevating lower jaw. The working stroke is characterized by overlapping activity in most branchial muscles and is resolved into three phases. Four muscles (obliquus dorsalis 3, levator posterior, levator externus 3/4, and obliquus posterior) that act to depress the upper jaws become active in the first phase. Next, the retractor dorsalis, the only upper jaw retracting muscle, becomes active. Finally, there is activity in several muscles (transversus ventrales, pharyngocleithralis externus, pharyngohyoideus, and protractor pectoralis) that attach to the lower jaws. The combined effect of these muscles is to elevate and stabilize the lower jaws against the depressing and retracting upper jaws.The model identifies a novel mechanism of upper jaw depression, here proposed to be the primary component of the perciform pharyngeal jaw bite. The key to this mechanism is the joint between the epibranchial and toothed pharyngobranchial of arches 3 and 4. Dorsal rotation of epibranchials 3 and 4 about the insertion of the obliquus posterior depresses the lateral border of pharyngobranchials 3 and 4 (upper jaw). The obliquus dorsalis 3 muscle crosses the epibranchial‐pharyngo‐branchial joint in arches 3 and 4, and several additional muscles effect epibranchial rotation. Five upper jaw muscles cause upper jaw depression upon electrical stimulation: the obliquus dorsalis 3, levator posterior, levator externus 3/4, obliquus posterior, and transversus dorsalis. This result directly contradicts previous interpretations of function for the first three muscles. The presence of strong depression of the upper pharyngeal jaws explains the ability of many generalized perciform fishes to crush hard prey in their pharyngeal apparatus.
Motor innervation and proprioceptors of the mouthparts in the worker honey bee apis mellifera. II. Maxillary and labial nerves
Authors: Masuko Keiichi 
Published: February 2005

AbstractSensory and motor innervation of the proboscis by branches of the maxillary and labial nerves of the worker honey bee has been investigated in specimens stained vitally by methylene blue or viewed by scanning electron microscopy. A chordotonal organ consisting of a single scolopidium is present in the maxillary palp. Flexion of the maxillary palp occurs only passively, induced by the flexion of the galea. This chordotonal organ may function as a proprioceptor for the movement of the galea. Another chordotonal organ exists in the prementum of the labium. It contains, on the average, 12 sensory cells and presumably responds to the bending of the labial palp. A nerve‐net of bipolar cells arises from the sensory branches of the maxillary nerve. Free nerve endings derived from the periphery of this nerve‐net expand broadly on the intersegmental membranes connected to the stipes. The right and left nerves to the dilator muscles of the salivarium exchange branches, resulting in the reciprocal innervation of each muscle.
Oviductal morphology and egg shelling in the oviparous lizards Crotaphytus collaris and Eumeces obsoletus
Authors: Guillette Louis J. , Fox Sandra L. , Palmer Brent D. 
Published: February 2005

AbstractMorphological changes occurring in the oviduct and epithelial cells of the lizards Crotaphytus collaris and Eumeces obsoletus during the natural reproductive cycle were examined and quantified. Additionally, development of the eggshell at different stages of gravidity was described. The anterior uterus of each species has a distinct glandular type which differs between species: in E. obsoletus, the glands are tubular and in C. collaris, branched saccular. The branched saccular glands in the anterior uterus of C. collaris produce collagen‐like material that forms the fibers of the shell membranes. However, fibers from the eggshell of E. obsoletus did not stain for collagen. The shell of both species is composed of a multilayered inner boundary covered externally by fibers of varying thickness. Initial layers are composed of thick fibers all lying along the same general axis. Outer layers of fibers are progressively thinner and an external surface layer composed of glycosaminoglycans (GAGs) is also present. In C. collaris, calcium, which is deposited in relatively small amounts on the shell surface, appears to be secreted by the epithelium of the anterior uterus. The nonciliated secretory epithelial cells covering the villi‐like folds of the posterior infundibulum secrete GAGs. Epithelial cell height of the infundibular villi is greatest during early gravidity. A functional relationship may exist between luteal activity and oviductal secretory activity because the activity of the glandular epithelium varied as gravidity progressed.
Failure to turn eggs during incubation: Development of the area vasculosa and embryonic growth
Authors: Deeming D. C. 
Published: February 2005

AbstractEffect of turning of the egg during incubation on development of the area vasculosa of the chick embryo was investigated. The size of the area vasculosa was determined by two methods: direct measurement with calipers and measurement of a template cut from the eggshell by use of an automatic surface area recorder. The effects of turning and additionally the effects of lowered temperature (36°C) on both growth of the area vasculosa by day 7 and embryo growth by day 14 of incubation were investigated. The effects of turning during a critical period for turning, from 3 to 7 days of incubation, were also recorded. Generally, failure to turn eggs retarded growth of the area vasculosa. Turning during the critical period stimulated the extent of growth of the area vasculosa by day 7 of incubation and of subsequent embryonic growth by day 14. Incubation at low temperature resulted both in reduced expansion of the area vasculosa and retarded embryonic growth in a pattern similar to that observed for unturned eggs. It is suggested that turning stimulates development of blood vessels in the area vasculosa via localized increases in blood pressure. The effect of a reduced area vasculosa is considered to retard embryonic development through restricted nutrient uptake from the yolk. The prevailing hypothesis that turning prevents deleterious membrane adhesions is questioned in light of these observations. It is suggested that the physiological basis for the need for turning lies in maximizing the growth rate of the area vasculosa to maximize yolk use and embryonic growth rate.
Structural and ultrastructural features of the inlet and outlet regions of the urinary bladders of the leech, Hirudo medicinalis L.
Authors: Wenning Angela , Cahill Mary Anne 
Published: February 2005

AbstractEach of the 34 nephridia in the leech, Hirudo medicinalis, has its own separate bladder. Urine flows from the last portion of the nephridium, the final canal, into the bladder through a special inlet which prevents backflow of urine. This inlet consists of a vestibule formed by two serially arranged septa, each with a small pore. As no muscles or cilia are associated with either the nephridia or the bladder inlet, urine flow into the bladder is passive. Urine leaves the bladder through an outlet that consists of a urethra with sphincters at both ends and an opening, the nephridiopore, in the ventral skin. The sphincter muscles are distinct from the body wall muscles and receive double innervation: urine retention and release is therefore active.
Scanning microscopy of the developing vagina in postnatal gerbils
Authors: Kress Annetrudi , Spornitz Udo M. , Zobrist Roger 
Published: February 2005

AbstractScanning electron microscopy of postnatally developing gerbil vagina (birth to maturity) shows that longitudinal folds form prior to transverse folds; the process of fold formation is initiated on the dorsal wall and proceeds ventrally. From days 1 to 7 postnatally, the vaginal epithelium is composed of either flat or bulging cells, depending on the vaginal region. The luminal cell surface is covered with uniform stubby microvilli and solitary cilia. Between days 9 and 20, the flat cells with distinct cell boundaries spread toward more proximal areas, leading to the formation of mixed patches of cells with flat or rounded apices. Individual elongated microvilli or tufts of forked microvilli may sprout from their surfaces. Solitary cilia gradually disappear.The transition from immature to mature vaginal epithelium starts around day 20, when individual cells recess below the level of neighboring cells. This process spreads throughout the vagina during the following days, reflecting local changes in the subsurface layers of the epithelium preparatory to exfoliation. Around day 40 the actual exfoliation of the luminal cell layer starts. By this time the surface characteristics of many of the desquamating cells have changed. In addition to microvilli, microridges are being formed. The process of exfoliation is finished by about day 60. The newly appearing cell layers now transform into typical cornified cells of the cycling vaginal epithelium.