On a Possible Hair Cell Turn-Over in the Inner Ear of the Caecilian Ichthyophis glutinosus (Amphibia: Gymnophiona)

The inner ear of the caecilian Ichthyophis glutinosus is briefly described. An analysis of the fine structure of the utricular macula show the presence of several varieties of hair cells. At least one type seems to be degenerating, another developing. A slow hair cell turnover is proposed. The number of afferent nerve endings in contact with a few hair cells were found to be 6–13 as reconstructed from electron microscopical serial sectioning.     

Marginal plates in hepatic peroxisomes of Ichthyophis glutinosus (Amphibia: Gymnophiona)

Summary The ultrastructure of hepatic peroxisomes was investigated in Ichthyophis glutinosus (Amphibia: Gymnophiona), employing perfusion fixation and the diaminobenzidine (DAB) technique for the visualization of catalase. The majority of peroxisomes is circular or rod-shaped, although elongated particles occasionally occur. They contain a finely granular matrix, lightly stained after the DAB procedure. Their mean diameter is approximately 0.25 m. Serial sections reveal that the circular and rod-shaped peroxisomal profiles are cross and oblique sections of highly tortuous, tubular organelles exceeding 2 m in length.In addition to tubular profiles, elongated, rectangular particles, as well as straight dumbbell-shaped organelles with distinct marginal plates are observed. They range from 900 to 1650 nm in length (mean = 1200 nm). In the flattened, thin central portion of the dumbbell-shaped particle, the peroxisomal membranes form a cisterna enclosing one or two uniformly thick marginal plates, which display a definite substructure with a periodicity of 10 nm.These findings indicate that peroxisomes in the liver of Ichthyophis exhibit a complex organization. It is suggested that the organelles undergo a specific differentiation process, morphologically characterized by the formation of enlarged segments of unusual shape.This study was supported by grants from the Deutsche Forschungsgemeinschaft, Fa 146/1-2 and Sto 75/9     

Fine structural and enzymehistochemical observations on the notochord of Ichthyophis glutinosus and Ichthyophis kohtaoensis (Gymnophiona,Amphibia)

Summary The notochord of Ichthyophis glutinosus and I. kohtaoensis consists of peripheral flattened cells characterized by a well-developed system of rough endoplasmic reticulum, bundles of tonofilaments, and abundant glycogen particles. These cells contain furthermore fairly high activities of -naphtyl-acetate esterase and 4-chloro-5-bromoindoxyl acetate esterase as well as acid phosphatase which was found in lysosomal localization. The huge intracellular vacuoles of the centrally situated cells possibly originate from electron translucent spaces within the glycogen fields of the peripheral cells.The notochord sheath consists of variously differentiated layers of collagen fibers and of an elastica externa. The diameters of the collagen fibers increase from the inner towards the outer region of the sheath. A peculiar feature of the Ichthyophis notochord sheath is a ring of mineralized collagen. The notochord of the caecilians investigated is compared with that of anurans, urodeles, and several groups of fish.Supported by the Deutsche Forschungsgemeinschaft.     

Hair Cell Polarization in the Flatfish Inner Ear

The hair cell polarization of the various sensory epithelia in the inner ear was examined in two species of flatfish, the Plaice (Pleuronectes platessa) and the Dab (Limanda limanda). The hair cells in the macula utriculi are polarized in the pattern usually seen for this macula in vertebrates. In the macula sacculi and macula lagenae the hair cell polarization is different from that hitherto described from bony fishes and other vertebrates. The polarization seen in these maculae in the flatfish explains their ability to sense movements in all directions, which is necessary if these sensory areas are the most important inner ear organs in the regulation of postural orientation.     

Retinal projections in the caecilian Ichthyophis kohtaoensis (Amphibia,Gymnophiona)

Summary The retinal projections of the caecilian Ichthyophis kohtaoensis were investigated by anterograde transport of HRP. The optic tract forms two bundles in the diencephalon, a narrow medial bundle in the optic tectum, and a basal optic tract consisting of few fibres. Terminal fields are in the thalamus, pretectum, tectum, and as a circum-scribed basal optic neuropile in the tegmentum. Thalamic, pretectal and tectal projections are contralateral as well as ipsilateral. The reduced but existing visual projection corresponds to a reduced but existing visually guided behaviour.     

Copulation and egg retention in an oviparous Caecilian (Amphibia: Gymnophiona)

Viviparity (i.e., the bearing of live young) has evolved from oviparity (egg laying) independently in various major vertebrate lineages, and several transitional stages have been described. The transition from oviparity to viviparity requires the retention of fertilised eggs in the female reproductive tract. Caecilian amphibians (Gymnophiona) display a considerable diversity of reproductive modes, including oviparity and viviparity. Among amphibians, caecilians have also modified the process of internal fertilisation through a special intromittent organ, or phallus, in males. Here we report the oviposition of “embryonated” eggs ranging from various gastrula-to-neurula stages by female Ichthyophis cf. kohtaoensis (Ichthyophiidae) from North-eastern Thailand. In addition, we describe a copulation resulting in an oviposition of embryonated eggs. Our findings will have implications for the further understanding of the evolutionary reproductive biology of amphibians.     

Investigations on the thyroid gland of embryonic larval and adult Ichthyophis glutinosus and Ichthyophis kohtaoensis (Gymnophiona,amphibia)

Summary Different developmental stages of two species of the genus Ichthyophis have been investigated. In the late embryo the follicular cells of the thyroid gland exhibit various degrees of cytodifferentiation. Well differentiated cells show a polar organization and contain numerous granular inclusions, but a colloid-containing lumen is rare. Most cells at this stage contain large lipid inclusions. In young and older larvae the cells contain well-developed rough ER and Golgi systems, numerous mitochondria, and abundant granular and vesicular inclusions. Tentative identifications were made of primary lysosomes, secondary lysosomes, residual bodies, and two types of small apical vesicles—containing resorbed colloid or transporting material into the follicular lumen. In the larvae the number of apical microvilli is relatively high. The thyroid cells of the older larvae seem to contain more granular and vesicular inclusions than those of the younger larvae. In the adult the size of the follicles greatly increases, the height of the epithelium decreases, microvilli become rare, residual bodies are more frequent, and the small primary lysosomes are replaced by larger ones. Colloid droplets have been found only rarely in the cytoplasm of the thyroid cells of adult animals. In the immediate neighbourhood of the follicular epithelium, profiles of nerve fibres were found in all animals. Radioiodide investigations—measurements of conversion ratio and thyroid uptake factor—show, if compared with the results of corresponding studies in other amphibians, only relatively small differences between the larvae on the one hand and larvae and adults on the other. The absolute counts of the thyroid region are lowest in the adult and highest in the older larvae, shortly before metamorphosis. Furthermore our results indicate, on the basis of four animals tested, that in Ichthyophis the activity of the thyroid gland is temperature dependent. The results in Ichthyophis show that the classical stages of metamorphosis, in other amphibians characterized among other things by different levels of thyroid activity, are very indistinct in this animal.We gratefully acknowledge the financial support of the Deutsche Forschungsgemeinschaft (We 380/5; Sto 76/4).     

The fine structure of the lateral-line organs of larval Ichthyophis (Amphibia: Gymnophiona)

Light and electron microscopic observations of the lateral-line organs of larval Ichthyophis kohtaoensis confirmed earlier reports of the occurrence of two different types of lateral-line organs. One type, the ampullary organ, possesses 15–26 egg-shaped sensory cells. Each sensory cell extends a single kinocilium surrounded by a few microvilli into the ampullary lumen. This is in contrast to the ampullary organs of urodele amphibians that contain only microvilli. The second type of organ, the ordinary neuromast, has 15–24 pear-shaped sensory cells arranged in two to three rows. Each sensory cell shows a kinocilium that is asymmetrically placed with respect to both a basal plate and approximately 60 stereovilli. The sensory cells of ampullary organs are always separated by supporting cells; those of neuromasts are occasionally in contact with one another. Numerous (neuromasts) or few (ampullary organs) mantle cells separate the organs from the epidermal cells. Only afferent synapses are found in the ampullary organs whereas vesicle-filled fibers together with afferent nerve terminals are found in neuromasts. Both organs contain similarly sized presynaptic spheres adjacent to the afferent fibers. It is suggested that the neuromasts have a mechanoreceptive function, whereas the ampullary organs have an electroreceptive one.     

Microanatomy of the digestive system of Supachai's caecilian,Ichthyophis supachaii Taylor, 1960 (Amphibia: Gymnophiona)

The gross anatomy and microanatomy of the digestive system of Ichthyophis supachaii were investigated. The microscopic structures of the digestive system are similar to those in other caecilians. Functional and developing teeth are present in adults. The tongue contains the genioglossus muscle. The digestive tract is elongated and consists of the mucosa, submucosa, muscularis and adventitia/serosa. The oesophagus contains longitudinal folds and lacks oesophageal glands. We report for the first time the caecilian gastric rugae and specific localization of oxynticopeptic cells in the anterior gastric region. The intestinal folds are exclusively present in the anterior intestinal region. The liver comprises 30–40 incomplete hepatic lobes, lying in an imbricate manner. Each lobe is enveloped by haematopoietic tissue that produces and delivers blood cells into sinusoids. Hepatic parenchyma is organized into anastomosing, two‐cell‐thick plates, having sinusoids at the basal domain and bile canaliculi at the apical domain of hepatocytes. Pigment cells are scattered inside sinusoids. The pancreas contains pancreatic acini interspersed with islets of Langerhans. The gallbladder proper is thin and continuous with the cystic duct wall. Neutral and carboxylated acid mucosubstances are secreted along the digestive tract, while sulphated mucosubstances are not produced by the stomach and anterior intestinal regions.     

版纳鱼螈泌尿系统解剖学及组织学观察

采用常规解剖学和组织学方法对版纳鱼螈Ichthyophis bannanica的泌尿系统进行研究.结果表明,版纳鱼螈泌尿系统包括中肾、输尿管、膀胱.版纳鱼螈的中肾由肾小体和肾小管组成,无皮质、髓质之分,肾小体主要分布在肾脏背外侧缘,肾小管由颈段、第1近曲小管、第2近曲小管、间段、第1远曲小管、第2远曲小管和集合管组成;输尿管位于两肾外侧缘,其上皮由前端的单层立方上皮过渡到后端的假复层上皮;膀胱为泄殖腔膀胱,内壁具有发达的绒毛,绒毛上皮为变移上皮.     

A New Species of Skin-Feeding Caecilian and the First Report of Reproductive Mode in Microcaecilia (Amphibia: Gymnophiona: Siphonopidae)

A new species of siphonopid caecilian, Microcaecilia dermatophaga sp. nov., is described based on nine specimens from French Guiana. The new species is the first new caecilian to be described from French Guiana for more than 150 years. It differs from all other Microcaecilia in having fewer secondary annular grooves and/or in lacking a transverse groove on the dorsum of the first collar. Observations of oviparity and of extended parental care in M. dermatophaga are the first reproductive mode data for any species of the genus. Microcaecilia dermatophaga is the third species, and represents the third genus, for which there has been direct observation of young animals feeding on the skin of their attending mother. The species is named for this maternal dermatophagy, which is hypothesised to be characteristic of the Siphonopidae.     

Germ-cell origin in the adult caecilian Ichthyophis glutinosus (Linn)

Summary In Ichthyophis glutinosus, no residual spermatogonia traceable to primordial germ cells of the embryo are seen, the primary spermatogonia of each season being formed afresh. Their only source so far as the adult is concerned, is the lining of the collecting duct and its numerous branches which ramify in the testis. No evidences of their origin from the surface epithelial cells of the testis, stromal cells or nurse cells are seen.     

Histomorphological studies of the testis and male genital ducts of Supachai's caecilian,Ichthyophis supachaii Taylor, 1960 (Amphibia: Gymnophiona)

We investigated the structure of the male reproductive system in Ichthyophis supachaii. The testis comprises a series of mulberry‐like lobes, each of which contains testis lobules occupied by germ cysts. A single cyst consists of synchronously developing germ cells. Six spermatogenic cell types, viz. primary spermatogonia, secondary spermatogonia, primary spermatocytes, secondary spermatocytes, spermatids and spermatozoa, have been identified and described. Notably, the testis of I. supachaii encompasses specific organization patterns of spermatids and spermatozoa during spermiogenesis. Spermiating cysts rupture and release spermatozoa to the collecting ducts, which are subsequently transported to the sperm duct, Wolffian duct and cloaca. We report for the first time ciliated cells in the epithelium of the caecilian Wolffian duct. The cloaca is divided into the urodeum and phallodeum. The urodeum has ciliated and glandular epithelia at its dorsolateral and ventral regions, respectively, as the lining of its internal surface. The muscular phallodeum is lined by ciliated epithelium. Paired Mullerian ducts lie parallel to the intestine and join the cloaca. The posterior portion of the duct is modified as the Mullerian gland. The most posterior region is non‐glandular and lined by ciliated epithelium. Our findings contribute further to information on the reproductive biology of caecilians in Thailand.     

版纳鱼螈的饲养观察

2006年对30条版纳鱼螈Ichthyophis bannanica进行饲养观察,发现版纳鱼螈生长速度缓慢,在非冬眠期体长月增长5.84 mm± 3.0 mm,体重月增长1.31 g± 0.92 g;活动规律受温度影响大,食性单一,具有冬眠和蜕皮的现象.     

Microscopic structures of the ovary and female genital ducts of Supachai's caecilian,Ichthyophis supachaii Taylor, 1960 (Amphibia: Gymnophiona)

The structures of the female reproductive system (ovary, oviduct and cloaca) of Ichthyophis supachaii were investigated by dissection, histology and light microscopy. Paired, elongated, sac‐like ovaries are parallel to the gut and fat bodies. Follicle stages include germinal nests of oogonia and primary oocytes, early and late previtellogenic follicles, early and late vitellogenic follicles and atretic follicles. Germinal nests of oogonia comprise oogonia and prefollicular cells. Nests of primary oocytes contain clusters of synchronously developing primary oocytes enclosed by connective tissue. Primary oocytes are associated with follicular cells. Previtellogenic follicles initially form the vitelline envelope, theca cell layers and patches of ooplasmic glycoproteins. Vitellogenic follicles contain heterogeneously sized spherical yolk granules. Atresia is present in several stages of developing follicles. The oviduct is divided into the anterior, middle and posterior parts. All oviductal parts are lined by non‐ciliated epithelium. A small number of mucous cells are present in the middle part. The cloaca of female I. supachaii is divided into the anterior and posterior chambers. The anterior chamber is lined by glandular stratified columnar epithelium, while the posterior chamber has stratified cuboidal epithelium with less mucus production. Our results contribute to useful information on the reproductive biology of caecilians.     

Histological and histochemical observations on the neurosecretory cells in the diencephalon of Chthonerpeton indistinctum and Ichthyophis paucisulcus (Gymnophiona,Amphibia)

Summary In the diencephalon of two species of Gymnophiona (Amphibia) two neurosecretory nuclei were examined with histological (Alcian Blue, Aldehyde Fuchsin, Brookes Trichrome stain) and enzyme histochemical techniques (acid phosphatase, -naphthyl acetate esterase, acetylcholinesterase (AChE)). In the preoptic nucleus two categories of secretory neurons were distinguished: large and medium sized neurons. The perikarya of both cell types contain very little neurosecretory material. The Alcian Blue method stained the medium sized neurons faintly but selectively. The tractus praeopticohypophyseus is marked by the presence of Herring bodies, which, however, are relatively scarce. The neurohypophysis, in contrast, contains large amounts of neurosecretory material. Both cell types of the preoptic nucleus are characterized by their very strong AChE and -naphthylacetate esterase activity. The AChE also marks the tractus praeoptico-hypophyseus. In the large neurons acid phosphatase is present around the nucleus; in the medium sized neurons this enzyme is concentrated close to the origin of the axon. In the dorso-caudal hypothalamus a small group of neurons is stained with Alcian-Blue. These neurons, which also contain AChE, are located immediately under the ependyma which seems to be specialized in this region.The financial support of the Deutsche Forschungsgemeinschaft is gratefully acknowledged (We 380/5)     

Sertoli cells in the testis of caecilians, Ichthyophis tricolor and Uraeotyphlus cf. narayani (Amphibia: Gymnophiona): light and electron microscopic perspective

The caecilians have evolved a unique pattern of cystic spermatogenesis in which cysts representing different stages in spermatogenesis coexist in a testis lobule. We examined unsettled issues relating to the organization of the caecilian testis lobules, including the occurrence of a fatty matrix, the possibility of both peripheral and central Sertoli cells, the origin of Sertoli cells from follicular cells, and the disengagement of older Sertoli cells to become loose central Sertoli cells. We subjected the testis of Ichthyophis tricolor (Ichthyophiidae) and Uraeotyphlus cf. narayani (Uraeotyphliidae) from the Western Ghats of Kerala, India, to light and transmission electron microscopic studies. Irrespective of the functional state of the testis, whether active or regressed, Sertoli cells constitute a permanent feature of the lobules. The tall Sertoli cells adherent to the basal lamina with basally located pleomorphic nuclei extend deeper into the lobule to meet at the core. There they provide for association of germ cells at different stages of differentiation, an aspect that has earlier been misconceived as the fatty matrix. Germ cells up to the 4-cell stage remain in the intercalating region of the Sertoli cells and they are located at the apices of the Sertoli cells from the 8-cell stage onwards. The developing germ cells are intimately associated with the Sertoli cell adherent to the basal lamina until spermiation. There are ameboid cells in the core of the lobules that appear to interact with the germ cells at the face opposite to their attachment with the Sertoli cells. Adherence of the Sertoli cells to the basal lamina is a permanent feature of the caecilian testicular lobules. The ameboid cells in the core are neither Sertoli cells nor their degeneration products.