Spermiogenesis in caecilians Ichthyophis tricolor and Uraeotyphlus cf. narayani (Amphibia: Gymnophiona): analysis by light and transmission electron microscopy

Spermiogenesis, known as spermateleosis in lower vertebrates, is the transformation of the round spermatid into a highly specialized spermatozoon with a species-specific structure. Spermateleosis and sperm morphology of two species of caecilians, Ichthyophis tricolor and Uraeotyphlus cf. narayani, from the Western Ghats of Kerala, India, were studied using light and transmission electron microscopy. Spermateleosis is described in early, mid-, and late phases. During the early phase, the spermatid nucleus does not elongate, but the acrosome vesicle is Golgi-derived and its material is produced as a homogeneous substance rather than as discrete granules. In development of the acrosome, the centrioles shift in position to the lower half of the cell. The acrosomal vesicles take the full shape of the acrosome with the establishment of the perforatorium in midphase. An endonuclear canal develops and accommodates the perforatorium. The incipient flagellum is laid down when the proximal centriole attaches to the posterior side of the nucleus and the distal centriole connects to the proximal centriole, which forms the basal granule of the acrosome. The axial fiber also appears during midphase. The mitochondria shift in position to the posterior pole of the cell to commence establishment of the midphase. Late phase is characterized by nuclear condensation and elongation. Consequently, the final organization of the sperm is established with the head containing the nucleus and the acrosome. The undulating membrane separates the axoneme and axial fiber. Most of the cytoplasm is lost as residual bodies.     

Accumulation of yolk in a caecilian (Gegeneophis ramaswamii) oocyte: A light and transmission electron microscopic study

There is a paucity of information on the female reproductive biology of the caecilian amphibians when compared with the other vertebrate groups. Hence, the accumulation of nutrient reserves in the form of yolk and formation of yolk platelets were studied in Gegeneophis ramaswamii, adopting light microscopic histological and transmission electron microscopy analysis. Previtellogenic as well as vitellogenic follicles were observed in appropriate preparations. On the basis of the source and the routes of entry, we identified four types of yolk precursor materials, precursors 1 to 4. The earliest material appearing in the oocyte consists of abundant lipid vesicles during the previtellogenic phase, i.e., much before the follicular epithelium is fully established. This is a contribution from the oocyte mitochondria, which we identified as yolk precursor material 1, and it is autosynthetic. Once the follicle cell‐oocyte interface is fully established, there is an accumulation of the principal component of the heterosynthetic yolk by sequestration from the blood through the intercellular spaces between follicle cells in a pinocytic process. This we identified as yolk precursor material 2. There was also an indication of a lipidic yolk material synthesis in the follicle cells sequestered from maternal blood through the follicle cells in an endocytic process in which the macrovilli of follicle cells and the microvilli of the oocyte play a role. This we identified as yolk precursor material 3. Contribution to the yolk of peptidic, glycosidic, and/or lipidic material synthesized in the vitellogenic oocyte was also indicated. This we identified as yolk precursor material 4. The sequential development of intercellular associations and indications of synthesis/sequestration of the yolk have been traced. Thus, we report the mechanistic details of synthesis/sequestration of the yolk materials in a caecilian. J. Morphol., 2008. © 2008 Wiley‐Liss, Inc.     

Review of Erigonine spider genera in the Neotropics (Araneae: Linyphiidae,Erigoninae)

The Neotropical genera of the linyphiid spider subfamily Erigoninae are revised at the genus level. Emphasis was placed on genera endemic to the Neotropics and species with dubious relationships to their nominal genera, especially species from the older literature. This work recognizes 50 genera in the Neotropics, of which 39 genera are strictly endemic to the Neotropics, three are represented outside the Neotropics by one species, and eight genera have significant representation both in and beyond the Neotropics. Three additional genera, Ceraticelus Simon, 1884, Idionella Banks, 1893, and Eulaira Chamberlin & Ivie, 1933, are represented in northern Mexico and/or the West Indies, but are best classified as having a Nearctic or Holarctic distribution. Species previously placed in the typically northern hemisphere genera Gongylidiellum Simon, 1884, Leptorhoptrum Kulczynski, 1894, Macrargus Dahl, 1886, Minyriolus Simon, 1884, Oedothorax Bertkau, 1883, Phanetta Keyserling, 1886, and Tmeticus Menge, 1868 are found to be misplaced or nomina dubia; two genera endemic to the Neotropics, Clitistes Simon, 1902 and Zilephus Simon, 1902 are nomina dubia. The genus Beauchenia Usher, 1983 is an erigonine, not a mynoglenine; there are no known representatives of the Mynogleninae in the Neotropics. One hundred and forty new combinations are established; 19 genera are synonymized including Micromaso Tambs‐Lyche, 1954, revalidation rejected; 34 species are synonymized. The following new genera are established: Gigapassus gen. nov. , Intecymbium gen. nov. , Moyosi gen. nov. , Orfeo gen. nov. and Toltecaria gen. nov. Malkinella Millidge, 1991 and Valdiviella Millidge, 1985 are preoccupied; Malkinola nom. nov. and Valdiviola nom. nov. are established as replacement names. The following new species are described: Asemostera daedalus sp. nov. , Asemostera enkidu sp. nov. , Asemostera janetae sp. nov. , Fissiscapus attercop sp. nov. , Gonatoraphis lysistrata sp. nov. , Gravipalpus standifer sp. nov. , Microplanus odin sp. nov. , Moyosi chumota sp. nov. , Myrmecomelix leucippus sp. nov. , Neomaso damocles sp. nov. , Notiomaso exonychus sp. nov. , Paraletes pogo sp. nov. , Psilocymbium acanthodes sp. nov. , Smermisia holdridgi sp. nov. and Smermisia parvoris sp. nov. The following species remain misplaced in inappropriate genera: Erigone fellita Keyserling, 1886, Erigone zabluta Keyserling, 1886, and Oedothorax fuegianus (Simon, 1902). For 23 species, type specimens could not be located and the species could not be unambiguously identified; the type of Macrargus pacificus Berland, 1924 could not be located, but it is transferred to Laminacauda Millidge, 1985. The female of Onychembolus subalpinus Millidge, 1985 described by Millidge in 1991 is mismatched; this female is Notiomaso exonychus sp. nov. ; the true female of Onychembolus subalpinus was described as both Neomaso bidentatus Millidge, 1991 syn. nov. and Neomaso tridentatus Millidge, 1991 syn. nov. The male and female of Asemonetes[now Asemostera]arcana (Millidge, 1991) are not conspecific; a male thought to be conspecific with the female of A. arcana is newly described; the true female of A. arcana is unknown. The transfer of Emenista dentichelis Berland, 1913 to Laminacauda comb. nov. renders Laminacauda dentichelis Millidge, 1991 a junior homonym; the replacement name Laminacauda baerti nom. nov. is provided for Laminacauda dentichelis Millidge. The following species were erroneously placed in erigonine genera: Oedothorax bisignatus Mello‐Leitão, 1945 is synonymized with Theridion calcynatum Holmberg, 1876 syn. nov. (Theridiidae); Liger incomta O. Pickard‐Cambridge, 1896 is transferred to Theridion Walckenaer, 1805 (Theridiidae) [Theridion incomtum comb. nov. ]; Erigone ectrapela Keyserling, 1886 is transferred to Dictyna Sundevall, 1833 (Dictynidae) [Dictyna ectrapela comb. nov. ]; Erigone peruana Keyserling, 1886 is transferred to Thymoites Keyserling, 1884 (Theridiidae) [Thymoites peruanus comb. nov. ]; Adelonetria dubiosa Millidge, 1991 is not a linyphiid and will be dealt with elsewhere. Lomaita darlingtoni Bryant, 1948 is confirmed as a linyphiid, not a mysmenid. © 2007 The Linnean Society of London, Zoological Journal of the Linnean Society, 2007, 149 (Suppl. 1), 1–263.     

A field guide to the caecilians of the Western Ghats, India

Caecilians are legless amphibians quite characteristic of the Western Ghats. Fourteen out of 16 Indian species occur in the Western Ghats and all are endemic. The present paper deals with the biology of caecilians with reference to external morphology and general breeding behaviour. It consolidates information on 26 morphological parameters which are used in caecilian identification. Metric multidimensional scaling of 16 species of caecilians using pair-wise euclidian distances calculated on the basis of 11 important morphometric parameters clearly depicts morphological distances between different species and more so the genera, thereby validating the classification. A field guide has been developed for the identification of caecilians based on a survey made all over the Western Ghats, observation of holotypes at the Natural History Museum, London and review of the literature. The study also reveals the microhabitat requirements of the caecilians. Further, the localities of caecilian distribution in the Western Ghats are mapped. The taxonomy of Indian caecilians is discussed.     

Global patterns of body size evolution are driven by precipitation in legless amphibians

Body size shapes ecological interactions across and within species, ultimately influencing the evolution of large‐scale biodiversity patterns. Therefore, macroecological studies of body size provide a link between spatial variation in selection regimes and the evolution of animal assemblages through space. Multiple hypotheses have been formulated to explain the evolution of spatial gradients of animal body size, predominantly driven by thermal (Bergmann's rule), humidity (‘water conservation hypothesis’) and resource constraints (‘resource rule’, ‘seasonality rule’) on physiological homeostasis. However, while integrative tests of all four hypotheses combined are needed, the focus of such empirical efforts needs to move beyond the traditional endotherm–ectotherm dichotomy, to instead interrogate the role that variation in lifestyles within major lineages (e.g. classes) play in creating neglected scenarios of selection via analyses of largely overlooked environment–body size interactions. Here, we test all four rules above using a global database spanning 99% of modern species of an entire Order of legless, predominantly underground‐dwelling amphibians (Gymnophiona, or caecilians). We found a consistent effect of increasing precipitation (and resource abundance) on body size reductions (supporting the water conservation hypothesis), while Bergmann's, the seasonality and resource rules are rejected. We argue that subterranean lifestyles minimize the effects of aboveground selection agents, making humidity a dominant selection pressure – aridity promotes larger body sizes that reduce risk of evaporative dehydration, while smaller sizes occur in wetter environments where dehydration constraints are relaxed. We discuss the links between these principles with the physiological constraints that may have influenced the tropically‐restricted global radiation of caecilians.     

Ameboid cells in spermatogenic cysts of caecilian testis

Sertoli cells constitute a permanent feature of the testis lobules in caecilians irrespective of the functional state of the testis. The developing germ cells are intimately associated with the Sertoli cells, which are adherent to the basal lamina, until spermiation. There are irregularly shaped cells in the cores of the testis lobules that interact with germ cells at the face opposite to their attachment with Sertoli cells. These irregularly shaped (ameboid) cells first appear in the lumen of the cysts containing primary spermatocytes and are continually present until spermiation. We did not observe any cytoplasmic continuity between a Sertoli cell and an ameboid cell. Both light microscopic and TEM observations reveal a phagocytic role for the ameboid cells: they scavenge the residual bodies shed by spermatozoa. Organization of the ameboid cells is grossly different from that of the spermatogenic and Sertoli cells. They appear to develop from the epithelium at the juncture of the collecting ductule with the testis lobule.     

Assessing the conservation status of soil‐dwelling vertebrates: Insights from the rediscovery of Typhlops uluguruensis (Reptilia: Serpentes: Typhlopidae)

Soil‐dwelling amphibians and reptiles are relatively poorly studied and understood. Difficulties in sampling these taxa in their subterranean habitats might impede assessments of their conservation status. We explore this issue with a case study of the burrowing scolecophidian snake Typhlops uluguruensis, endemic to the Uluguru Mountains in the Eastern Arc of Tanzania. Despite recent standard faunistic surveys, there have been no reported sightings or collections of T. uluguruensis since the type series of four specimens was collected in 1926. Intensive replacement of forest by agriculture in the vicinity of the type locality had led to concern about the conservation status of this and other species. We report the rediscovery of T. uluguruensis in low intensity agriculture adjacent to human habitation, and close to the type locality. We compare the new material with the type series, and discuss the implications of this rediscovery for conservation assessments of small, soil‐dwelling lower vertebrates. We advise caution in determining conservation status when, as is usually the case, no special sampling of the soil has been carried out. Additionally, relatively neglected disturbed habitats should also be given more attention. Standard sampling methods for soil‐dwelling vertebrates need to be further developed and established.     

Life history and reproduction of the neotropical caecilian Siphonops annulatus (Amphibia,Gymnophiona, Siphonopidae), with special emphasis on parental care

Due to their mainly fossorial way of life, caecilian amphibians are the least known order of terrestrial vertebrates. Here, we present new observations on the natural history and reproductive biology of the neotropical oviparous, siphonopid caecilian Siphonops annulatus from a long-term study of this species in the field and in captivity. In the studied population, mating occurs between the end of August and beginning of October, and oviposition between November and December, when rainfall peaks. Egg hatching occurs between the end of December and beginning of January. The complete cycle of maternal care, from oviposition to independent, self-sufficient offspring lasts about 3 months. After eclosion, the altricial young feed on the mother's specially modified skin (maternal dermatophagy) and are also supplied by a fluid released from coming from the maternal cloaca. Also presented are observations on the burrows, feeding and social behaviour of S. annulatus.