Transforming growth factor‐β signal regulates gut bending in the sea urchin embryo

During gastrulation, one of the most important morphogenetic events in sea urchin embryogenesis, the gut bends toward the ventral side to form an open mouth. Although the involvement of transforming growth factor‐β (TGF‐β) signals in the cell‐fate specification of the ectoderm and endoderm along the dorsal–ventral axis has been well reported, it remains unclear what controls the morphogenetic behavior of gut bending. Here, using two sea urchin species, Hemicentrotus pulcherrimus and Temnopleurus reevesii, we show that TGF‐β signals are required for gut bending toward the ventral side. To search for the common morphogenetic cue in these two species, we initially confirmed the expression patterns of the dorsal–ventral regulatory TGF‐β members, nodal, lefty, bmp2/4, and chordin, in T. reevesii because these factors are appropriate candidates to investigate the cue that starts gut bending, although genetic information about the body axes is entirely lacking in this species. Based on their expression patterns and a functional analysis of Nodal, the dorsal–ventral axis formation of T. reevesii is likely regulated by these TGF‐β members, as in other sea urchins. When the Alk4/5/7 signal was inhibited by its specific inhibitor, SB431542, before the late gastrula stage of T. reevesii, the gut was extended straight toward the anterior tip region, although the ectodermal dorsal–ventral polarity was normal. By contrast, H. pulcherrimus gut bending was sensitive to SB431542 until the prism stage. These data clearly indicate that gut bending is commonly dependent on a TGF‐β signal in sea urchins, but the timing of the response varies in different species.     

Larvae of <Emphasis Type="Italic">Lamprogrammus shcherbachevi</Emphasis> (Ophidiiformes: Ophidiidae) from the western North Pacific Ocean

Three exterilium larvae (18.2 mm notochord length to 113.3 mm standard length) of an ophidiid, Lamprogrammus shcherbachevi, from the western North Pacific are described. The specimens had a highly specialized morph with a remarkably elongate trailing gut and ventral coracoid process, and many elongate anterior dorsal fin rays, as occur in other exterilium larvae, but were characterized by unique melanophore patterns (a cluster of melanophores on the back of the stalked pectoral fin base, a row of clusters midlaterally on the trunk and caudal region, and further clusters on the trailing gut). Although the largest specimen (113.3 mm standard length, much larger than the previously recorded maximum size of exterilium larvae) retained typical features of the exterilium stage, the ventral coracoid process was significantly reduced in size compared with that of a smaller specimen (37.8 mm standard length). Comparison of the largest specimen with an adult suggests that the anterior dorsal fin rays would disappear during the transformation stage.     

Larval development of Asemichthys taylori (Cottidae)

Larvae of Asemichthys taylori were reared in the laboratory to identifiable juveniles. A preserved series of larvae was characterized in part by fin meristics (X–XI, 14–15 dorsal fin rays; 15 anal fin rays), as well as a combination of the alignment of the jaw tip with the ventral margin of the gut, heavy lateral melanistic pigment except on the caudal peduncle, and a series of postanal ventral melanophores. An internal, horizontal band of melanin extends through the head from the snout to the gut. Hypural plates do not align vertically even after settlement, giving the appearance that the larvae do not complete notochord flexion during their planktonic stage. Larval A. taylori resemble known larvae of Radulinus spp., a genus under which some authors have synonymized the monotypic genus Asemichthys.     

PISCIVORY IN THE FEATHERED DINOSAUR MICRORAPTOR

The largest specimen of the four‐winged dromaeosaurid dinosaur Microraptor gui includes preserved gut contents. Previous reports of gut contents and considerations of functional morphology have indicated that Microraptor hunted in an arboreal environment. The new specimen demonstrates that this was not strictly the case, and offers unique insights into the ecology of nonavian dinosaurs early in the evolution of flight. The preserved gut contents are composed of teleost fish remains. Several morphological adaptations of Microraptor are identified as consistent with a partially piscivorous diet, including dentition with reduced serrations and forward projecting teeth on the anterior of the dentary. The feeding habits of Microraptor can now be understood better than that of any other carnivorous nonavian dinosaur, and Microraptor appears to have been an opportunistic and generalist feeder, able to exploit the most common prey in both the arboreal and aquatic microhabitats of the Early Cretaceous Jehol ecosystem.     

Cystacanths of Acanthocephala in notothenioid fish from the Beagle Channel (sub-Antarctica)

The morphology of relaxed cystacanths of polymorphid acanthocephalans collected from notothenioid fishes in the Beagle Channel (Magellanic subregion of sub-Antarctica) is described. A parasite of birds, Andracantha baylisi (Zdzitowiecki, 1986), was found in Patagonotothen longipes and Champsocephalus esox. It has: a proboscis 0.82–0.89 mm long; a proboscis hook formula of 16 rows of 9/10–10/11, including 4–5 basal hooks; distal hooks with the longest blades; a fore-trunk not separated from the hind-trunk by a constriction; large somatic spines arranged in two zones separated by a zone of small, loosely dispersed spines; and only the anterior 36–40% of ventral side of the trunk is covered with spines. One male specimen of Corynosoma sp. was found in Patagonotothen tessellata. It differs from A. baylisi in that the distal proboscis hooks are similar in length to the prebasal hooks, it has a smaller proboscis (0.77 mm) and in the distribution of the somatic spines, which are contiguous with the genital spines on the ventral side of the trunk and lack a zone of small spines between zones of larger spines. A parasite of seals and fur seals, Corynosoma evae Zdzitowiecki, 1984, was found in P. longipes and Champsocephalus esox. It has: a proboscis 0.61–0.78 mm long; a proboscis hook formula of 20–22 rows of 12–13, including 3/4–4 basal hooks; prebasal hooks with the longest blades; a trunk divided into fore-trunk and hind-trunk; somatic spines covering the anterior 64–74% of the ventral side of the trunk; genital spines present only in males; and a terminal genital opening in both sexes. Corynosoma beaglense n. sp. was found in Champsocephalus esox. It has: an almost cylindrical proboscis (length 0.52–0.56 mm); a proboscis hook formula of 16 rows of 9/10–10/11, including 4–4/5 basal hooks; distal hooks shorter than the prebasal hooks; a fore-trunk not separated from the hind-trunk by a constriction; somatic spines contiguous with the genital spines on the ventral side of the trunk of the male and covering the entire length of the ventral side of the female trunk, and the presence of genital spines surrounding the terminal genital pore of the male. The definitive host of this species is unknown.     

The scaphopod foot is ventral: more evidence from the anatomy of Rhabdus rectius (Carpenter, 1864) (Dentaliida: Rhabdidae)

Scaphopods comprise about 900 described species of elongate infaunal molluscs, separated into two orders. The phylogenetic position of this class is contentious, having been proposed as a sister-group to bivalves or alternatively cephalopods, all groups that notably represent dramatic modifications of the molluscan body plan and historical confusion over the fundamental body axes. The digging scaphopod foot was previously considered to be anterior. Here we use a three-dimensional tomographic reconstruction of digestive anatomy and partial dorso-ventral musculature, to test the hypothesis that the scaphopod foot is ventral. Similar to cephalopods, the body orientation is confounded by ano-pedal flexion, but rationalising scaphopods is perhaps further undermined by their infaunal lifestyle, which confounds comparison of ecological life position. Some scaphopods are locally abundant, providing good quality material for anatomical study. In our focal species, Rhabdus rectius (Carpenter, 1864), sexes can reliably be differentiated in vivo by differential colour of the gonad (yellow in females; white in males). The gut is composed of three complete loops. Based on the orientation of the digestive tract and the dorso-ventral muscles, we find further evidence to support the interpretation that the concave side of the scaphopod shell is anterior (the site of the mouth) and the foot is ventral.     

Dinosaur Highways

A specimen of Calceola sandalina (Linne 1771) from the Givetian of the Czech Republic shows severe injury on its right side when observed from its cardinal side. Approximately one-half of the counter side is missing between the counter septum and the alar corallite angle. The injury is healed within the calice, as visible also on deformed septa close to injury, while the outer flat ventral side shows no signs of healing. The operculum is not preserved but the damage clearly must have affected it. It is difficult to envision how such damage might have occurred by abiotic means in a rather low-energy environment without the influx of grains larger than silt. We consider the injury a result of attack by a predator. When speculating on the animal capable of producing such injury, one must consider preferably a vertebrate with strong jaws: fish-like animals capable of durophagy (placoderms and chondrichthyans) appeared in the Devonian.     

The chordoid larva of Symbion pandora (Cycliophora) is a modified trochophore

Developmental and free-living stages of the chordoid larva of the cycliophoran species, Symbion pandora Funch and Kristensen 1995, were studied using light and electron microscopy. In the free-living stage of the larva, about 200 μm long, four ciliated areas are found: two anterior bands, a ventral ciliated field, and a posterior unit on the ventral side of the foot. The nervous system consists of a dorsal brain and a pair of ventral longitudinal nerves. A gut is absent. A pair of protonephridia, each with a single multiciliated terminal cell and at least one duct cell, is present. Nephridiopores are not localized. A pair of corsal ciliated organs is posterior to the brain. The homology between these and the apical organ of a trochophore larva is discussed. A distinctive longitudinal rod, the chordoid organ, consists of vacuolized cells with circular myofilaments. The organ is comparable to a similar structure in gastrotrichs. In the discussion of the phylogenetic position of Cycliophora among protostomians, important morphological observations that are described in the present study indicate that, despite some dissimilarities, the chordoid larva is a modified trochophore. © 1996 Wiley-Liss, Inc.     

Description and ecology of larvae and juveniles of three native cypriniforms of coastal southern California

Larval series of the Santa Ana sucker, Catostomus santaanae (Federally Threatened), arroyo chub, Gila orcutti (California Species of Special Concern), and Santa Ana speckled dace, Rhinichthys osculus (California Species of Special Concern) are described from wild-caught specimens from the Los Angeles and Santa Ana river drainages. Santa Ana sucker larvae are elongate, having 41–46 myomeres and a distinctive paired-triangle patch of melanophores over the midbrain. Melanophores present on the snout, dorsal body, lateral midline, dorsal gut, postanal ventral body, and caudal fin. Preanal length 74–79% in body length (BL), typical of catostomids. Arroyo chub larvae relatively deep-bodied, 36–39 myomeres, and a heart-shaped patch of melanophores over the midbrain with a line of melanophores trailing posteriorly. Heavy pigment present on the snout, lower jaw, dorsal body, lateral midline, gill arches, dorsal gut, postanal ventral body, and caudal fin; short preanal length of 65–72% BL, typical of native North American cyprinids. Santa Ana speckled dace are similar to arroyo chub except for having less pigment on the ventral gut, large distinct melanophores on the ventrolateral caudal peduncle, a wedge-shaped patch of midbrain melanophores with no distinct line trailing posteriorly, and lateral midline melanophores that do not extend anteriorly. These three species often occur together and with nonnative cyprinids. Characters distinguishing them from other local larvae, including southern fathead minnow, Pimephales promelas confertus and red shiner, Cyprinella lutrensis, are discussed with their habitat preferences.     

Coulonia parva n. sp., a new species of Astropectinidae (Asteroidea; Echinodermata) from the Santonian (Upper Cretaceous) of Sierra de Montsech (southern Pyrenees, Spain)

A new astropectinid sea star,Coulonia parva n. sp., is described from the Santonian of the Sierra de Montsech, northern Spain. The single specimen shows part of a rather weathered ventral side. It is characterized by comparatively long arms (R/r approx. 3/1), with one row of actinals reaching far into the arms; inferomarginals on the interbrachial arc have deep fasciolar grooves that are less developed on the arms; there are no larger spines on adambulacrals and probably also on inferomarginals. Based on presence of deep marginal fascioles,C. parva n. sp. is inferred to have shared the capability for self-burial with the relatedC. platyspina Hess &Blake.      

Anatomical and physiological observations on the organization of mechanoreceptors and local interneurons in the central nervous system of the wandering spider Cupiennius salei

Summary In the wandering spider Cupiennius salei, the functional neuroanatomy of leg mechanosensory receptor neurons and interneurons associated with a single leg neumere was investigated by combined intracellular recording and Lucifer yellow ionophoresis. Trichobothria axons that selectively respond to air currents and to low-frequency airborne vibrations have arborizations restricted to ventral regions of the appropriate leg neuromere. Receptor afferents that respond selectively to substrateborne vibrations are distributed ventrally in the corresponding leg neuromere and extend into certain interganglionic tract neuropiles. Golgi impregnation and intracellular dye filling show that local interneurons originate in ventral sensory neuropiles of leg neuromeres and ascend dorsally to terminate amongst dendrites of motor neurons. Local interneurons generally show higher thresholds for vibration stimuli than do receptors. Local interneurons typically receive inputs from one or several types of receptors. Some respond to stimulation of a single leg, others respond to stimulation of several legs on the same side of the body. The functional morphology of the receptor afferents is correlated with known physiological characteristics of slit sensilla and trichobothria. Structure and activity of the local interneurons are compared with analogous interneurons in other arthropods.     

The ventral nerve cord in Cephalocarida (Crustacea): New insights into the ground pattern of Tetraconata

Cephalocarida are Crustacea with many anatomical features that have been interpreted as plesiomorphic with respect to crustaceans or Tetraconata. While the ventral nerve cord (VNC) has been investigated in many other arthropods to address phylogenetic and evolutionary questions, the few studies that exist on the cephalocarid VNC date back 20 years, and data pertaining to neuroactive substances in particular are too sparse for comparison. We reinvestigated the VNC of adult Hutchinsoniella macracantha in detail, combining immunolabeling (tubulin, serotonin, RFamide, histamine) and nuclear stains with confocal laser microscopy, complemented by 3D‐reconstructions based on serial semithin sections. The subesophageal ganglion in Cephalocarida comprises three segmental neuromeres (Md, Mx1, Mx2), while a separate ganglion occurs in all thoracic segments and abdominal segments 1–8. Abdominal segments 9 and 10 and the telson are free of ganglia. The maxillar neuromere and the thoracic ganglia correspond closely in their limb innervation pattern, their pattern of mostly four segmental commissures and in displaying up to six individually identified serotonin‐like immunoreactive neurons per body side, which exceeds the number found in most other tetraconates. Only two commissures and two serotonin‐like immunoreactive neurons per side are present in abdominal ganglia. The stomatogastric nervous system in H. macracantha corresponds to that in other crustaceans and includes, among other structures, a pair of lateral neurite bundles. These innervate the gut as well as various trunk muscles and are, uniquely, linked to the unpaired median neurite bundle. We propose that most features of the cephalocarid ventral nerve cord (VNC) are plesiomorphic with respect to the tetraconate ground pattern. Further, we suggest that this ground pattern includes more serotonin‐like neurons than hitherto assumed, and argue that a sister‐group relationship between Cephalocarida and Remipedia, as favored by recent molecular analyses, finds no neuroanatomical support. J. Morphol. 275:269–294, 2014. © 2013 Wiley Periodicals, Inc.     

Discovery of ventrally directed spiralia in a Permian spiriferellid brachiopod and implications for its feeding system

Spiralia are lophophore‐supporting, coiled internal structures developed in some extinct brachiopods. In spite of considerable variations in their orientation, the spiralia of most spiriferide and spiriferinide taxa are known to be laterally directed. Recent studies have shown that these brachiopods consistently have a median inhalant and lateral exhalant feeding system. Here, we report a Permian spiriferellid brachiopod fossil (Spiriferella protodraschei) bearing ventrally directed spiralia in its interior. Using the serial sections of the specimen, we have reconstructed the detailed morphology and orientation of the spiralia. Each spiralium in the specimen does not show the apically tapering pattern supposedly universal in all the known types of spiralia: instead it maintains a similar diameter even at its last whorl. The spiralia appear to have directly developed from strong and anteriorly extended crura, consisting of ten whorls in one side and 13 whorls in the other side. As the morphology and orientation of spiralia are immediately associated with the arrangement of spirolophous lophophore within the mantle cavity, the extraordinary orientation and form of the spiralia indicate that this brachiopod likely had developed a considerably modified feeding pattern with respect to most other spirolophous brachiopods. It is postulated that the inhalant/exhalant current circulation of the species (and its descendants) would be considerably different from that of other spiriferide taxa. In particular, the combination of the vertically oriented life posture (free‐lying with thickened ventral apex bottom) and ventrally directed spiralia resembles both fossil atrypide and modern rhynchonellide brachiopods in the orientation of spirolophe, suggesting that some spiriferellid brachiopods may have developed a lateral inhalant/median exhalant feeding current system. A few spiriferide and spiriferinide brachiopod taxa with a weakly transverse but strongly convex ventral valve are noted to exhibit similar modifications in their spiralia, possibly due to the spatial limitation of their mantle cavities.     

The caecilian amphibian Scolecomorphus kirkii Boulenger as prey of the burrowing asp Atractaspis aterrima Günther: trophic relationships of fossorial vertebrates

A report is given of an adult caecilian, Scolecomorphus kirkii, found in the gut of a specimen of the snake Atractaspis aterrima from the Udzungwa Mountains, Tanzania. Both predator and prey are largely fossorial in soil, and their ecology is poorly known, such that this is the first reported predator of any scolecomorphid caecilian. The caecilian was ingested head first and much of the flesh from the anterior of the specimen had been digested. The prey/predator mass ratio is 0.48. This value is substantially higher than reported for A. aterrima from West Africa, and refutes the notion that this species feeds only on small prey. Most reported predators of caecilians are snakes, and a brief review is presented.     

An Angiocardiographic Analysis of the Central Circulation in the Air Breathing Teleost Channa argus

The unique anatomy of the double ventral aorta outflow system in the air breathing teleost Channa argus (Ophiocephalus) showing an anterior and posterior ventral aorta is described. The marked trabeculation of the ventricle and bulbus arteriosus and the arrangement of central veins are used as a basis for the hypothesis that Channa may selectively channel the well oxygenated blood draining the air breathing organs via the anterior cardinal vein to the posterior ventral aorta, which forms the systemic arterial circulation. An angiocardiographic technique was used to test this hypothesis, as well as to delineate the functional role of the heart chambers in the cardiac cycle. No reflux of contrast to the sinus venosus during atrial filling and no ventricular filling before atrial contraction were apparent, which makes the atrium the main determinant of the ventricular end-diastolic volume. Ventricular contraction left a small or no residual volume. The ventricular ejectate was initially nearly completely absorbed by the very elastic bulbus arteriosus, acting as a pressure chamber (Windkessel) stabilizing and prolonging ventral aortic blood flow. Contrast medium was not selectively passed from the anterior cardinal vein to the posterior ventral aorta. However, the diameter of this vessel and its density of contrast were greater than in the anterior aorta, suggesting a preference for a greater blood flow from the air breathing organ through the heart to the posterior aorta.     

A case of colonic lymphoid tissue invasion by Gymnophalloides seoi in a Korean man

A 65-year old Korean man, living in Mokpo-city, Jeollanam-do, Republic of Korea, visited a local clinic complaining of right upper quadrant pain and indigestion. At colonoscopy, he was diagnosed as having a carcinoma of the ascending colon, and thus, a palliative right hemicolectomy was performed. Subsequently, an adult fluke of Gymnophalloides seoi was incidentally found in a surgical pathology specimen of the lymph node around the colon. The worm was found to have invaded gut lymphoid tissue, with characteristic morphologies of a large oral sucker, a small ventral sucker, and a ventral pit surrounded by strong muscle fibers. This is the first reported case of mucosal tissue invasion by G. seoi in the human intestinal tract.     

Eptatretus strickrotti n. sp. (Myxinidae): first hagfish captured from a hydrothermal vent

A single hagfish (Myxinidae, Eptatretus) specimen was recently captured at a hydrothermal vent site on the East Pacific Rise (38 degrees S). This is the first capture of a member of the jawless fishes (agnathans) from a hydrothermal vent site. The specimen differs from all congeners by the very slender body (depth 2.9% of total length), the paired and median ventral nasal sinus papillae, and the presence of 10 afferent branchial arteries on the medial ventral aorta. It is further unique because of a combination of the following features: slime pore counts; paired dorsal nasal sinus papillae; 12 gill pouches and gill apertures; posterior left side of body widely separated from pharyngocutaneous duct; 3/2 multicusp configuration; ventral aorta bifurcated anteriorly between 2nd and 3rd gill pouches (counted from the snout toward the heart); and pink coloration. The specimen is here described as a new species named Eptatretus strickrotti. Molecular 16S rRNA data places this new species as the basal-most species of Eptatretus, providing important new insight to the evolution of hagfishes as a whole.     

Paralineopsis taki gen. et sp. nov., a littoral heteronemertean from Japan,provided with special proboscideal,circulatory and sensory organs of significance to nemertean systematics

Some morphological features with major systematic significance are recorded in the heteronemertean Paralineopsis taki gen. et sp. nov. from Onomichi, Japan as follows: horizontal band of specialized epithelium extends from near apex to the opening of the cerebral organ canal on either side of the head; precerebral region filled with gelatinous (hyaline) connective tissue in which longitudinal muscles are absent; body wall muscles do not accompany rhynchodaeal invagination; rhynchodaeum initially only epidermal; inner longitudinal muscles of ventral wall of cephalic blood lacuna become intimately associated with rhynchodaeum forming a dorsal saddle over it; cerebral organs do not penetrate inner longitudinal muscles, and do not contact blood vascular system; proboscideal diaphragm post-cerebral; outer longitudinal muscles absent throughout body; longitudinal muscles of proboscis derived from inner longitudinal musculature. The systematic relationship of P. taki and Paralineus elisabethae (Schütz, 1911) from Villefranche, France is discussed.     

Spinitheca gen. nov.—A new orthothecimorph hyolith genus from the Lower Cambrian of the Siberian platform

The study of the morphology of orthothecimorph hyoliths from the Atdabanian (Lower Cambrian) of the Siberian Platform allowed the recognition of the new genus and species Spinitheca sysoievi gen. and sp. nov.     

The Vascularization of the Kidneys in Bufo bufo (L.), Bombina variegata (L.), Rana ridibunda (L.) and Xenopus laevis (D.) (Amphibia,Anura) as Revealed by Scanning Electron Microscopy of Vascular Corrosion Casts

Abstract The vascular patterns of the ventral side of the kidneys in Bufo bufo and Rana ridibunda is similar. Strong venulae renales revehentes dominate. In Bombina variegata and Xenopus laevis, however, also many superficially located glomeruli are found at the ventral side. In Xenopus further branching of the renal arteries into afferent arterioles attracts attention. Bundles of delicate afferent arterioles originate within circumscribed areas of the renal artery. The glomerular layer of the kidney is tightest in Bombina, and has its maximal extension in Rana. It covers up to 2/3 of the thickness of the kidney while in the other species studied the glomeruli are restricted to the ventral third of the kidney. Glomeruli with double afferent or efferent arterioles were rarely found in Xenopus. The vascularization of the dorsal side of the kidneys is characterized by the presence of large (Bufo, Rana, Xenopus) or small (Bombina) venulae renales advehentes.