Ventral Velum Research Articles

Descriptions of Leptolaimus sinensis sp. nov. and Perspiria brevicaudata sp. nov. (Nematoda) from the Yellow Sea, China

Two new free-living marine nematodes which were collected at silt beach of Rizhao along the Yellow Sea are identified here as Leptolaimus sinensis sp. nov. and Perspiria brevicaudata sp. nov. Leptolaimus sinensis sp. nov. is characterized by annulated cuticle with lateral alae, 2 µm in width; buccal cavity cylindrical; cephalic setae 2 µm long; amphidial fovea unispiral, circular in outline; six to seven evenly spaced tubular precloacal supplements and 23-29 continuous alveolar supplements extending from cloaca to level of the base of buccal cavity; spicules slender, slightly arcuate; gubernaculum with dorso-caudal apophysis; tail conico-cylindrical, about 6 times cloacal body diameter in males and elongated in females, about 9 times anal body diameter in length. Perspiria brevicaudata sp. nov. is characterized by having four cephalic setae and four cervical setae; small buccal cavity with dorsal tooth and minute ventral tooth; amphidial fovea unispiral, looking like double circle in outline, surrounded partially by cuticle striations; spicules arcuate with ventral velum, handle-like proximally and tapered distally; gubernaculum plate-shaped, without apophysis; twelve winged precloacal supplements present. Updated identification keys for group of Leptolaimus species characterized by the presence of both alveolar and tubular precloacal supplements and for species of Perspiria are also given.

Two new species of genus Perspiria (Desmodoridae: Nematoda) from the Bohai Bay of China

ABSTRACT Two new species of genus Perspiria were discovered from the subtidal sediments of Bohai Bay of China and described as Perspiria macramphida sp. nov. and Perspiria major sp. nov. Perspiria macramphida sp. nov. is characterised by the large and longitudinal loop-shaped amphidial fovea, partially surrounded with cuticular striations; conical buccal cavity with a dorsal tooth; spicules arcuated with enlarged proximal end and ventral velum, 53–61 µm long; 15–16 papillary precloacal supplements; and tail conico-cylindrical with prominent transverse striations except its terminal end. Perspiria major sp. nov. is characterised by its small unispiral amphidial fovea looking like a double circle in outline, partially surrounded with cuticular striations; conical buccal cavity with a small dorsal tooth; pharynx with a pear-shaped terminal bulb; tail short, conico-cylindrical; spicules strongly curved with heart-shaped proximal end, without ventral velum; and lacking precloacal supplements. An updated key for valid species of Perspiria is provided. http://www.zoobank.org/urn:lsid:zoobank.org:pub:AB1A7D19-1030-4FF8-8882-3F79C9080597

Phalloidin fluorescence and confocal microscopy reveal the musculature development of clam Ruditapes philippinarum.

Knowledge of early development in bivalves is of great importance to understand the function of animal organ systems and the evolution of phenotypic diversity. Manila clam (Ruditapes philippinarum) is an economically important bivalve living in marine intertidal zones. To determine the pattern of muscle development in the clams, we investigate the characteristics of musculature development utilizing phalloidin staining and confocal microscopy. Myofilaments first appear at the early trochophore stage, and gradually become orderly arranged during the transition from trochophore to veliger. For veliger, larval muscle system is mainly composed of dorsal velum retractors, medio-dorsal velum retractors, ventral velum retractors, ventral larval retractors and anterior and posterior adductor muscles. After metamorphosis, the muscle system of late veliger has been reconstructed, showing the irreversible shrink of velum retractor muscles, the rapid growth of wedge-shaped foot and mantle margins. One of the most striking changes in settled spats is the development of sophisticated architecture of foot musculature, which consists of transverse pedal muscles, anterior foot retractor and posterior foot retractor. These findings will not only provide the basis to understand the dynamic pattern of myogenesis in the burrowing bivalves, but also provide valuable information for comparative analysis of muscle development among bivalves.

Perspiria boucheri sp. nov. (Nematoda, Desmodorida) from the East China Sea

A new free-living marine nematode species from marine sediments in the East China Sea, is described here as Perspiria boucheri sp. nov. The new species is characterized by amphideal fovea surrounded partially by body annulations; four cephalic setae stout; conical buccal cavity with a minute dorsal tooth and two ventrosublateral teeth; pharynx with a pyriform terminal bulb; tail elongated, conical with 3/4 posterior cylindrical portion which having distinct coarse annulations; spicules strongly curved with narrow ventral velum, handle-shaped proximally; gubernaculum canoe-shaped, without apophysis. The new species differs from the most similar species Perspiria striaticaudata (Timm, 1962) by strongly curved spicules with handle-shaped proximal end, gubernaculum without dorsal apophysis and relatively shorter tail. Updated key to all species of Perspiria is provided.

Internal oral morphology in larvae of the genus Rhinella Fitzinger, 1826 (Amphibia, Anura, Bufonidae).

From the 86 species allocated in the genus Rhinella, 25 have their tadpoles described and only R. arenarum, R. chrysophora, R. icterica, R. ornata, R. schneideri and R. spinulosa have aspects of the internal oral morphology evidenced. Herein, the internal oral morphology from 12 species of Rhinella distributed between the morphological groups of R. crucifer, R. granulosa, R. marina and R margaritifera is described and compared. The internal oral morphology of Rhinella is little variable in many aspects. Despite the many similarities found between the tadpoles of Rhinella, the study showed that there are characteristics that exhibit interspecific variation that can be used in the taxonomy of the genus. Important features to distinguish species were: number of infrarrostral projections; number and shape of the infralabial papillae; size, arrangement, shape and apex of the lingual papillae; shape of the buccal floor arena papillae; number of projections of the ventral velum; shape of the prenarial ridge; choanae arrangement; number and apex of the postnarial papillae; number and shape of the secondary branches on the lateral ridge papilla; buccal roof arena papillae arrangement.

Trichodorus arasbaranensis n. sp. (Nematoda: Trichodoridae) from a natural forest in Arasbaran, north-west Iran

AbstractTrichodorus arasbaranensis n. sp. is described from the rhizosphere of Carpinus betulus growing in forests in Arasbaran, north-west Iran. The new species is characterised by its large body length (1020-1520 μm in males; 1100-1500 μm in females), cuticle abnormally swollen upon fixation, onchiostyle medium-sized (41-66 μm in males; 49-65 μm in females) and secretory-excretory pore at level of pharyngeal bulb. Males have a single ventromedian cervical papilla varying in position from anterior to posterior to secretory-excretory pore, sperm cells with sausage-shaped nucleus, large (74-110 μm), smooth, ventrally curved spicules, manubrium wide, not offset from lamina, lamina narrowed in mid-region and with a distal ventral velum, and gubernaculum 25.5-34.5 μm long. Females have a short, but well developed, rounded vagina with large, rounded, triangular to oval-shaped, sclerotised vaginal pieces in lateral view. Because of its large body size, the new species most closely resembles T. magnus, T. elegans, T. obtusus, T. californicus and T. nanjingensis, from which the female can be differentiated by the short vagina length in relation to the corresponding body diam. and large size of the vaginal sclerotised pieces, and the male by the longer and differently shaped spicule which bears a velum. A key to the males and females of the Trichodorus spp. recorded from Iran is provided.

Morphology of premetamorphic larvae of Lysapsus limellus (Anura: Pseudinae)

AbstractThe chondrocranium, visceral skeleton, mandibular, hyoid and hyobranchial musculature, buccal apparatus and buccopharyngeal cavity of premetamorphic larvae of Lysapsus limellus from Santa Fe, Argentina are described. The cartilaginous skeleton corresponds in general terms to that of a typical pond type tadpole. Some characteristic features are the flat triangular projection of the arcus subocularis quadrati, the scarce development of the cartilagines orbitales, the presence of the processus pseudopterygoideus and quadratoethmoidalis, the open fenestra basicranialis, and the presence of a reticulating cartilaginous connection between the spicula III, IV and the plana hypobranchialia. Regarding muscles, the most salient characters are the configuration of the m. levator mandibulae lateralis, with nasal insertion, and the presence of a discontinuous m. subarcualis rectus II-IV. The oral disc and buccal cavity show features that indicate a generalist-mesophagous diet, for example the presence of jaw sheaths, rows of keratodonts, filter structures on the buccal floor and roof, and a glandular epithelium in the ventral velum.

Regression of blood vessels in the ventral velum of Xenopus laevis Daudin during metamorphosis: light microscopic and transmission electron microscopic study.

Structural changes of the ventral velum of Xenopus laevis tadpoles from late prometamorphosis (stage 58) to the height of metamorphic climax (stage 62) were examined by light and transmission electron microscopy. Special emphasis was given to the blood vessel regression. Early changes of velar capillaries were formation of luminal and abluminal endothelial cell processes, vacuolation, and cytoplasmic and nuclear chromatin condensation. At the height of metamorphic climax, transmission electron microscopy revealed apoptotic endothelial cells with nuclear condensation and fragmentation, intraluminal bulging of rounded endothelial cells which narrowed or even plugged the capillary, and different stages of endothelial cell detachment ('shedding') into the vessel lumen. These changes explain the 'miniaturisation' of the velar microvascular bed as well as the typical features found in resin-casts of regressing velar vessels which have been observed in a previous scanning electron microscopy study of the ventral velum.

Vascular regression during amphibian metamorphosis--a scanning electron microscope study of vascular corrosion casts of the ventral velum in tadpoles of Xenopus laevis Daudin.

We used scanning electron microscopy and vascular casting to study gross arterial supply, venous drainage, and microvascular patterns of the fully developed ventral velum of tadpoles of Xenopus laevis Daudin and analyzed changes of the velar vascular bed from prometamorphosis to metamorphic climax in a qualitative and quantitative manner. The multilayered, highly secretory ventral velum is supplied bilaterally by an anterior and a posterior velar artery, branches of the external carotid artery. Velar arterioles branch mainly dichotomously and form a flat two-dimensional capillary meshwork overlying the tops of filterplates I-IV. Thymopharyngeal veins, dorsal branches of the filter plates veins, and the internal jugular veins drain the velum toward the venous sinus of the heart. Location, architecture, and the drainage of the velar microvascular bed into the venous sinus make a significant contribution of the velar capillaries to gas exchange unlikely. Instead, velar capillaries rather serve the nutrition of the secretory epithelium. The overall morphology of velar vessels from prometamorphosis to metamorphic climax--deduced from vascular corrosion casts--points to atonic vessels with increased leakage indicated by adhering globular extravasations, and to obstructed or blind ending vessels evidenced by the tapered and/or rounded blind ending cast vessels. The significant decrease in the size of the ventral velum during the metamorphic cycle was paralleled by a miniaturization of the velar vascular bed. We hypothetize that this miniaturization occurs by a shortening and fusion of capillary mesh elements. Our findings in corrosion casts, particularly the miniaturization of the velar microvascular bed and the morphology of the regressing capillaries, point to profound morphologic and ultrastructural changes in velar vessels; a study on the fine structure of the microvascular bed of the ventral velum in metamorphic tadpoles is in progress.

The biology of the Pe-ret’ Toad, Otophryne robusta (Microhylidae), with special consideration of its fossorial larva and systematic relationships

Adult and larval Otophryne robusta- were collected in Colombia, South America. Although this genus has been assigned to the family Microhylidae, a variety of both adult and larval features distinguish it from all other microhylids. The adult is a diurnally active leaf mimic with complex agonistic behaviours and vocalizations. It tends to walk rather than hop, and does not burrow in captivity. The larva is unique in having minute, dagger-like, keratinized teeth and a sinistral spiracle at the tip of a long tube. The mature larva lives shallowly buried in sand at the bottom of clear, shallow streams. The anatomy of the tadpole was examined for clues to how it burrows into and survives in sand, as well as to the correct phylogenetic association of the genus. Internally, the tadpole is most similar to microhylid tadpoles and has a wealth of oral features (e.g. unperforated internal nares, branchial food traps arranged in crescentic organs, ventral velum divided on the midline, glottis located rostral to the free edge of the ventral velum, large gill filters etc.) that characterize that family. Most, if not all, of the unique features of the Otophryne larva can be associated with its fossorial existence. The arrangement of the muscles suggest that it can actively raise and lower its snout during burrowing and possibly dorsiflex its head on its vertebral column. Although the larval teeth first suggest carnivory, many features indicate that maerophagy is not possible. Stomach contents include a variety of bacteria and micro-organisms, but no fragments of macroscopic animals. We conclude that the Otophryne tadpole is a microphagous suspension feeder and its teeth are more important for keeping sand grains out of its mouth than for grasping prey. Since the O. robusta larva does not burrow deeply, the tip of its spiracular tube probably extends upward above the sandy bottom and into the current. In this position pressure would be lower at the spiracle than at the mouth and a current could be passively drawn (by the Bernoulli effect) through the oral cavity for feeding and respiration. If this is correct then the Otophryne larva is the first fossorial vertebrate known to passively filter-feed. All features of the tadpole, except the keratinized teeth and sinistral spiracle, indicate an affinity of Otophryne-/i with South American microhylids. The tadpole and adult are, however, so unusual as to warrant subfamilial status+ADs- we propose the subfamily Otophryninac for this monotypic genus.

The filter apparatus of Rana temporaria and Bufo bufo larvae (Amphibia, Anura)

In larvae of Rana temporaria and Bufo bufo the location of filter apparatus within the larval organization, the arrangement of the morphological parts as branchial food trap, ventral velum, and filter rows, as well as their surface anatomy, are similar to that of other species of Orton's larval type IV. The means by which mucous with its entrapped food particles is transported from the filter rows to the esophagus is finally resolved. The dorsally positioned ciliary cushion extends far ventrally between the filter plates. From their contact with the filter rows, the cilia transport the mucous to Kratochwill's caudally positioned “Flimmerrinne” and from there to the esophagus. The original chordate principle of mucous entrapment and ciliary transport is thus retained by these anuran larvae. The only modification specific to the latter is the division into a ventral filter apparatus, whose epithelia serve for mucus entrapment, and a dorsal ciliary area.

The Filter Apparatus of Larval Pelodytes punctatus (Amphibia: Anura)

AbstractParts of the larval filter apparatus (ventral velum, branchial food traps, filter plates) were studied, using scanning electron microscopy. The primary species studied was Pelodytes punctatus, but Alytes obstetricans, Pelobates cultripes, Scaphiopus holbrooki, Telmatobius culeus, Hyla cinerea and Rana sphenocephala were also examined. Other data were taken from literature. Previous authors, in similar studies, maintained that variations in larval filter apparatus morphology supported the anuran suborders Archeo- and Neobatrachia. The present study concludes that the larval filter apparatus cannot be used to support any subordinal arrangement, but affirms its potential value at lower systematic levels. Pelobatoids tend to have modified filter apparatuses. Four types are recognizeable: 1) Pelodytes; 2) Scaphiopus; 3) Megophrys; 4)Pelobates, Leptobrachium, Oreolalax. Although other beaked Asian genera remain unstudied, these groups are enough to indicate that current pelobatoid systematics is erroneous. Pelodytes has the most primitive pelobatoid filter apparatus. This, the moderately derived larval chondrocranium and the peculiar mixture of certain primitive and derived character states in the adult frog (none shared with other pelobatoids), indicate a long independent phylogeny for Pelodytes. This in turn, supports recognition of a separate monogeneric family Pelodytidae.

The Bearing of Filter Feeding on the Water Pumping Mechanism ofXenopusTadpoles (Anura: Pipidae)

Abstract New findings on the functional anatomy of filter feeding have permitted some clarification of water flow through tadopoles. The dorsal velar apparatus projects downward from the roof of the buccopharynx and consists of three mucosal pads and three vanes on both sides of the midline. At least four functions may be ascribed to the dorsal velar apparatus. 1. Each pad and its complementary vane fit so flush into each of the three bilateral filter cavities that exhalent water must flow in thin sheets over the filter plates before its exit via the pharyngeal clefts. 2. Like hydrofoils, the vanes deflect water and prevent strong currents from disorganizing the mucous food cords. 3. When tadpoles cease water pumping, the plugging effect of the dorsal velar apparatus in the filter cavities helps to occlude the pharyngeal clefts. 4. Secretions of dorsal velar glands, especially on the surface of the velar pads, may assist the mucus of the ventral velum to entrap suspended food. Other findings concern the M3b muscle, which helps to elevate the buccopharyngeal floor during expiration; the lack of cilia, but presence of low glandular elevations on the ventral velum; the reduction of the exits from the pharyngeal clefts 2 and 3 into a single valvular exit controlled by the B2b and B2c muscles; and the probable absence of a mechanical feeding function for the oral tentacles.

The function of the ventral velum during gill irrigation in Rana catesbeiana.

The direct observation of the ventral velum in normally breathing tadpoles confirms earlier evidence for a valvular function of this structure during inspiration. The ventral velum also acts as a hydrofoil during expiration and as a mucus-secreting surface for the entrapment of suspended food particles.As the volume of water pumped per irrigation cycle is normally less than the maximum volume of the buccal cavity, it is unnecessary for the pharynx also to become filled with inspired water during the sinking of the buccal floor. Therefore the ventral velum's cyclic occlusion of the buccal cavity from the pharynx is no handicap to normal irrigation; on the contrary, it is a prerequisite for the efficiency of the pharyngeal pump.The dorsal velum does not participate in valvular activity, but deflects the respiratory current downward and inward to the gill cavity via gill clefts 2, 3, and 4. Therefore the strong flow pumped into the pharynx by buccal compression is prevented from impinging directly on the ciliated groove behind the dorsal velum and thereby interfering with the transport of food into the esophagus.

Hydrostatic pressures during normal ventilation in the bullfrog tadpole

A detailed description of the water flow through the ventilation system of the bullfrog tadpole has been facilitated by recording the time dependence of normal hydrostatic pressures in the system. The mouth and nasal intakes are discontinuous but a pharyngeal pressure pump to support the buccal pressure pump has been found to assist in maintaining a flow through the gill cavity. The alternate action of these pumps drives water into the gill cavity during almost the entire ventilation cycle and owes its efficiency to the occlusion between the buccal cavity and pharynx during the compression stroke of the pharyngeal pump. The need for a valvular function of the ventral velum has thus been demonstrated as it is the only structure between the buccal cavity and pharynx which can effect such cyclic occlusion.