Phylogenetic relationships of Indian caecilians (Amphibia: Gymnophiona) inferred from mitochondrial rRNA gene sequences

India has a diverse caecilian fauna, including representatives of three of the six currently recognized families, the Caeciliidae, Ichthyophiidae, the endemic Uraeotyphlidae, but previous molecular phylogenetic studies of caecilians have not included sequences for any Indian caecilians. Partial 12S and 16S mitochondrial gene sequences were obtained for a single representative of each of the caecilian families found in India and aligned against previously reported sequences for 13 caecilian species. The resulting alignment (16 taxa, 1200 sites, of which 288 cannot be aligned unambiguously) was analyzed using parsimony, maximum-likelihood, and distance methods. As judged by bootstrap proportions, decay indices, and leaf stabilities, well-supported relationships of the Indian caecilians are recovered from the alignment. The data (1) corroborate the hypothesis, based on morphology, that the Uraeotyphlidae and Ichthyophiidae are sister taxa, (2) recover a monophyletic Ichthyophiidae, including Indian and South East Asian representatives, and (3) place the Indian caeciliid Gegeneophis ramaswamii as the sister group of the caeciliid caecilians of the Seychelles. Rough estimates of divergence times suggest an origin of the Uraeotyphlidae and Ichthyophiidae while India was isolated from Laurasia and Africa and are most consistent with an Indian origin of these families and subsequent dispersal of ichthyophiids into South East Asia.     

Molecular systematics of caeciliid caecilians (Amphibia: Gymnophiona) of the Western Ghats, India

Together, Indian plus Seychelles caeciliid caecilian amphibians (Gymnophiona) constitute approximately 10% of the extant species of this order. A molecular phylogenetic analysis of all but one (or two) nominal species (16, in five genera) is presented based on mitochondrial (12S, 16S, cytb, cox1) and nuclear (RAG1) sequence data. Results strongly support monophyly of both Seychelles and peninsular Indian caeciliids, and their sister-group status. Within the Indian caeciliids, Indotyphlus and Gegeneophis are monophyletic sister genera. The phylogenetic position of Gegeneophis ramaswamii, Gegeneophis seshachari, and Gegeneophis carnosus are not well resolved, but all lie outside a well-supported clade of most northern Western Ghats Gegeneophis (madhavai, mhadeiensis, goaensis, danieli/nadkarnii). Most nominal species of Indian caeciliid are diagnosed by robust haplotype clades, though the systematics of G. carnosus-like forms in northern Kerala and southern Karnataka requires substantial further investigation. For the most part, Indian caeciliid species comprise narrowly distributed, allopatric taxa with low genetic diversity. Much greater geographic genetic diversity exists among populations referred to G. seshachari, such that some populations likely represent undescribed species. This, the first phylogenetic analysis of Indian caeciliids, generally provides additional support for recent increases in described species (eight since 1999), and a framework for ongoing taxonomic revision.     

Development of the tectum in Gymnophiones,with comparison to other amphibians

Tectal development in a number of caecilian (Gymnophiona: Amphibia) species was examined and compared with that in frogs and salamanders. The caecilian optic tectum develops along the same rostrocaudal and lateromedial gradients as those of frogs and salamanders. However, differences exist in the time course of development. Our data suggest that, as in salamanders, simplification of morphological complexity in caecilians is due to a retardation or loss of late developmental stages. Differences in the time course of development (heterochrony) among different caecilian species are correlated with phylogenetic history as well as with variation in life histories. The most pronounced differences in development occur between the directly developing Hypogeophis rostratus and all other species examined. In this species, the increase in the degree of morphological complexity is greatly accelerated. J. Morphol. 236:233–246, 1998. © 1998 Wiley-Liss, Inc.     

A mitogenomic perspective on the phylogeny and biogeography of living caecilians (Amphibia: Gymnophiona)

The caecilians, members of the amphibian Order Gymnophiona, are the least known Order of tetrapods, and their intra-relationships, especially within its largest group, the Family Caeciliidae (57% of all caecilian species), remain controversial. We sequenced thirteen complete caecilian mitochondrial genomes, including twelve species of caeciliids, using a universal primer set strategy. These new sequences, together with eight published caecilian mitochondrial genomes, were analyzed by maximum parsimony, partitioned maximum-likelihood and partitioned Bayesian approaches at both nucleotide and amino acid levels, to study the intra-relationships of caecilians. An additional multiple gene dataset including most of the caecilian nucleotide sequences currently available in GenBank produced phylogenetic results that are fully compatible with those based on the mitogenomic data. Our phylogenetic results are summarized as follow. The caecilian family Rhinatrematidae is the sister taxon to all other caecilians. Beyond Rhinatrematidae, a clade comprising the Ichthyophlidae and Uraeotyphlidae is separated from a clade containing all remaining caecilians (Scolecomorphidae, Typhlonectidae and Caeciliidae). Within this large clade, Scolecomorphidae is the sister taxon of Typhlonectidae and Caeciliidae but this placement did not receive strong support in all analyses. Caeciliidae is paraphyletic with regard to Typhlonectidae, and can be divided into three well-supported groups: Caeciliidae group 1 contains the African caeciliids Boulengerula and Herpele; Caeciliidae group 2 contains Caecilia and Oscaecilia and it is the sister taxon of Typhlonectidae; Caeciliidae group 3 comprises the remaining species of caeciliids. The mitochondrial genome data were also used to calculate divergence times for caecilian evolution using the penalized likelihood method implemented in the program R8S. The newly obtained dating results are compatible with (but a little older than) previous time estimates mainly based on nuclear gene data. The mitogenomic time tree of caecilians suggests that the initial diversification of extant caecilians most probably took place in Late Triassic about 228 (195–260) Ma. Caeciliids currently distributed in India and the Seychelles diverged from their African and American relatives most probably in Late Jurassic about 138 (112–165) Ma, fairly close to the time (130 Ma) when Madagascar–India–Seychelles separated from Africa and South America. The split between the Indian caeciliid Gegeneophis and Seychellean caeciliids occurred about 103 (78–125) Ma, predated the rifting of India and the Seychelles (65 Ma).     

Remarkable genetic homogeneity in unstriped, long-tailed Ichthyophis along 1500 km of the Western Ghats, India

The mountainous Western Ghats are part of a biodiversity hotspot and extend for about 1600 km, lying close and subparallel to the west coast of peninsular India. The region is a centre of diversity for amphibians, and recent preliminary work on some components of both caecilian (Gymnophiona) and frog (Anura) fauna is indicative of a high degree of local endemism. We investigated diversity in mitochondrial rRNA 12S and 16S sequences for long-tailed, unstriped Ichthyophis (Amphibia: Gymnophiona: Ichthyophiidae) that potentially represent four taxonomically confused and poorly known endemic caecilian species. Data were analysed for18 individuals from along c . 1500 km of the Western Ghats region. Genetic diversity is remarkably low, with a maximum uncorrected p -distance of 0.5%. These DNA sequences and new morphological data do not allow us to reject the null hypothesis that the sample comprises only a single, widely distributed, highly interconnected species. The phylogenetic signal among the data is extremely low. However, population genetic analyses reveal that the Palghat Gap, a c . 30 km discontinuity in the Western Ghats considered to be significant in the biogeography of other organisms occurring in this region, corresponds to a significant subdivision of long-tailed, unstriped Ichthyophis into two groups.     

Assembly of ovarian follicles in the caecilians Ichthyophis tricolor and Gegeneophis ramaswamii: light and transmission electron microscopic study

Though much is known about various aspects of reproductive biology of amphibia, there is little information on the cellular and mechanistic basis of assembly of ovarian follicles in this group. This is especially true of the caecilians. Therefore, taking advantage of the abundant distribution of caecilians in the Western Ghats of India, two species of caecilians, Ichthyophis tricolor and Gegeneophis ramaswamii, were subjected to light and transmission electron microscopic analysis to trace the sequential changes during the assembly of ovarian follicles. The paired ovaries of these caecilians are elongated sac-like structures each including numerous vitellogenic follicles. The follicles are connected by a connective tissue stroma. This stroma contains nests of oogonia, primary oocytes and pregranulosa cells as spatially separated nests. During assembly of follicles the oocytes increase in size and enter the meiotic prophase when the number of nucleoli in the nucleus increases. The mitochondrial cloud or Balbiani vitelline body, initially localized at one pole of the nucleus, disperses through out the cytoplasm subsequently. Synaptonemal complexes are prominent in the pachytene stage oocytes. The pregranulosa cells migrate through the connective tissue fibrils of the stroma and arrive at the vicinity of the meiotic prophase oocytes. On contacting the oocyte, the pregranulosa cells become cuboidal in shape, wrap the diplotene stage oocyte as a discontinuous layer and increase the content of cytoplasmic organelles and inclusions. The oocytes increase in size and are arrested in diplotene when the granulosa cells become flat and form a continuous layer. Soon a perivitelline space appears between the oolemma and granulosa cells, completing the process of assembly of follicles. Thus, the events in the establishment of follicles in the caecilian ovary are described.     

Stages in follicle cell/oocyte interface during vitellogenesis in caecilians <Emphasis Type="Italic">Ichthyophis tricolor</Emphasis> and <Emphasis Type="Italic">Gegeneophis ramaswamii</Emphasis>: a transmission electron-microscopic study

We describe the ultrastructural organization of the vitellogenic follicle stages in two caecilian species. Monthly samples of slices of ovary of Ichthyophis tricolor and Gegeneophis ramaswamii from the Western Ghats of India were subjected to transmission electron-microscopic analysis, with special attention to the follicle cell/oocyte interface. In order to maintain uniformity of the stages among the amphibians, all the stages in the caecilian follicles were assigned to stages I–VI, the vitellogenic and post-vitellogenic follicles being assigned to stages III–VI. Stage III commences with the appearance of precursors of vitelline envelope material in the perivitelline space. Stages IV and V have been assigned appropriate substages. During the transition of stage III to stage VI oocytes, a sequential change occurs in the manifestations of follicle cells, perivitelline space, vitelline envelope and oocyte cortex. The vitelline envelope becomes a tough coat through the tunnels of which the macrovilli pass to interdigitate between the microvilli. The oocyte surface forms pinocytic vesicles that develop into coated pits and, later, coated vesicles. Contributions of the oocyte cortex to the vitelline envelope and of the follicle cells to yolk material via synthesis within them are indicated. The follicle cell/oocyte interface of vitellogenic follicles of these two caecilians resembles that in anurans and urodeles, with certain features being unique to caecilians. Thus, this paper throws light on the possible relationships of caecilians to anurans and urodeles with special reference to ovarian follicles. This research was supported by funds from the Kerala State Council for Science, Technology and Environment (KSCSTE), through the SARD facility, and by the FIST scheme of Department of Science and Technology, Government of India, New Delhi, to the Department of Zoology, University of Kerala, Thiruvananthapuram, and to the Department of Animal Science, Bharathidasan University, Thiruchirapalli (SR/FST/LSI-233/2002).     

A new frog species from the central western Ghats of India, and its phylogenetic position

Tropical evergreen forests of Indian subcontinent, especially of the Western Ghats, are known hot spots of amphibian diversity, where many new anuran species await to be identified. Here we describe from the Sharavathi River basin of central Western Ghats a new shrub-frog taxon related to the anuran family Rhacophoridae. The new frog possesses the characteristic features of rhacophorids (dilated digit tips with differentiated pads circumscribed by a complete groove, intercalary cartilages on digits, T-shaped terminal phalanges and granular belly, the adaptive characters for arboreal life forms), but also a suite of unique features that distinguish it from all known congeners in the region. Morphogenetic analysis based on morphological characteristics and diversity in the mitochondrial 12S and 16S rRNA genes revealed it to be a new Philautus species that we named Philautus neelanethrus sp. nov. The phylogenetic analysis suggests the new frog to represent a relatively early Philautus species lineage recorded from the region. The distribution pattern of the species suggests its importance as a bioindicator of habitat health. In general, this relatively widespread species was found distributed only in non-overlapping small stretches, which indirectly indicates the fragmentation of the evergreen to moist deciduous forests that characterize the Western Ghats. Thus the discovery of the new rhacophorid species described here not only further reinforces the significance of the Western Ghats as a major hotspot of amphibian biodiversity, but also brings into focus the deterioration of forest habitats in the region and the need for prioritization of their conservation.     

Phylogeny of the freshwater crabs of the Western Ghats (Brachyura,Gecarcinucidae)

The Western Ghats mountain range in India is a biodiversity hotspot for a variety of organisms including a large number of endemic freshwater crab species and genera of the family Gecarcinucidae. The phylogenetic relationships of these taxa, however, have remained poorly understood. Here, we present a phylogeny that includes 90% of peninsular Indian genera based on mitochondrial 16S rRNA and nuclear histone H3 gene sequences. The subfamily Gecarcinucinae was found to be paraphyletic with members of two other subfamilies, Liotelphusinae and Parathelphusinae, nesting within. We identify a well‐supported clade consisting of north Indian species and one clade comprising mostly south Indian species that inhabit the southern ‘sky islands’ of the Western Ghats. Relationships of early diverging genera, however, were resolved with low support. This study also includes newly sampled material from an isolated mountain plateau in the northern part of the Western Ghats, representing a new species of Gubernatoriana, which we describe here as Gubernatoriana basalticola sp. n. The new species is immediately distinguished from its congeners and the related genera Ghatiana and Inglethelphusa by its carapace and cheliped morphology, which are unique among Indian freshwater crabs. This study highlights the urgent need for continued faunistic studies to assess the true diversity of gecarcinucid crabs on the Indian subcontinent, to fully understand the basal phylogenetic relationships within the freshwater crab family Gecarcinucidae, and to evaluate the conservation threat status and biogeography of the montane freshwater crabs of the Western Ghats.     

A comparative study of locomotion in the caecilians Dermophis mexicanus and Typhlonectes natans (Amphibia: Gymnophiona)

We compared locomotion of two species of caecilian using x-ray videography of the animals traversing smooth-sided channels and a pegboard. Two channel widths were used, a body width channel and a body width + 20% channel. The terrestrial caecilian, Dermophis mexicanus , used internal concertina locomotion in both channels and lateral undulation on the pegboard. The aquatic caecilian, Typhlonectes natans , was not able to move at all in the body width channel. In the wider channel Typhlonectes proceeded at the same speed as Dermophis while using normal, rather than internal, concertina locomotion. On the pegboard, Typhlonectes used lateral undulation and achieved 2.5 times the speed managed by Dermophis. A phylogenetic analysis of this, and other, evidence shows that (1) internal concertina evolved in the ancestor to extant caecilians and (2) internal concertina locomotion was secondarily lost in the aquatic caecilians.     

Comparative morphology and evolution of the lungless caecilian Atretochoana eiselti (Taylor) (Amphibia: Gymnophiona: Typhlonectidae)

Atretochoana eiselti is a radically divergent aquatic caecilian until recendy known from only a single specimen from South America. In addition to its status as the largest lungless tetrapod known, and the only known lungless caecilian, this species has a suite of highly unusual morphological features that sets it apart from all other tetrapods, including sealed choanae (internal nostrils), complete loss of pulmonary arteries and veins, novel cranial architecture, and a novel stapedial muscle. The external, buccal, skeletal, muscular and cardiovascular anatomies of Atretochoana eiselti are described and compared to these features in other caecilians, particularly representatives of all typhlonectid genera which are its closest relatives. The comparative morphological data are used as a basis for interpretations of the ecology and evolution of Atretochoana eiselti. It is argued that lunglessness and the transition to cutaneous gas exchange is correlated with life in cold, montane, fast-flowing streams. Here, high oxygen concentrations and reduced metabolic rate serve to relax the physiological limitations on body size imposed by a reliance upon cutaneous gas-exchange, and lungs can produce disadvantageous buoyancy. Cranial evolution has increased the gape of Atretochoana eiselti relative to other caecilians, and seems likely to be associated with a shift in prey size and possibly type. Several modifications of the cranium appear to be associated with enhanced cranial kinesis in which a distinct cheek unit is highly mobile. The novel stapedial musculature is interpreted as contributing to this cranial kinesis. Respiratory and cranial evolution are argued to be correlated, with the ventilatory function of the buccopharyngeal pump constraining the evolution of the skull. The evolution of lunglessness removed this constraint facilitating repatterning of the skull.     

Sexual size dimorphism in caecilian amphibians: analysis, review and directions for future research

Sexual dimorphism, widespread in the animal kingdom, describes differences between the sexes in size, shape and many other traits. Sexual size dimorphism (SSD) plays a significant role in understanding life history evolution and mating systems. The snakelike morphology of limbless caecilian amphibians lacking obvious secondary sexual characters (in contrast to frogs and salamanders) impedes accurate intrasexual comparisons. In this study, sexual size dimorphism in the oviparous caecilian Ichthyophis cf. kohtaoensis, a phylogenetically basal caecilian, was analysed. Females were larger in all body and head characters tested. However, when adjusted to body size (total length), females differed only in their cloacal shape. Clutch volume was positively correlated to female body size, thus female fecundity increased with body size supporting the hypothesis of a fecundity-selected SSD in the oviparous Ichthyophis cf. kohtaoensis. A review of the present SSD data for caecilians shows that many species are monomorphic for body size but show dimorphism in head size, while other species demonstrate female-biased SSD. Male-biased SSD has not been reported for caecilians. To understand life history evolution in caecilians, further studies on the reproductive biology of other taxa are urgently needed, in particular for rhinatrematids and uraeotyphlids. New data will allow phylogenetically controlled comparative analyses to fully explore the pattern of SSD among caecilian lineages.     

Cellular migration and morphological complexity in the caecilian brain

The morphology of the tectum mesencephali and the medial pallium is studied in species representing the six families of caecilians (Amphibia: Gymnophiona) in order to determine whether differences in brain morphology are related to function, phylogenetic history, or life history strategies. In general, the caecilian tectum is characterized by simplification in having little to no lamination and few migrated cells. The degree of morphological complexity differs between species and between brain regions. Our data suggest that changes in brain morphology are due to a mosaic of different influences. We did not find a strict correlation between visual system reduction and tectal morphologies. However, phylogenetic effects exist. The greatest degree of morphological complexity is found in members of the Rhinatrematidae, a family that is considered basal to the lineage. Thus, simplification of brain morphology in caecilians must be considered a secondary or derived rather than a primitive feature. Direct development and miniaturization are correlated with the greatest simplification in the tectum mesencephali and medial pallium. There is a relationship between differences in brain morphology and heterochrony in caecilians, as in other amphibians. J. Morphol. 231:11–27, 1997. © 1997 Wiley-Liss, Inc.     

Evolutionary relationships of the lungless caecilian Atretochoana eiselti (Amphibia: Gymnophiona: Typhlonectidae)

Appreciation of the diversity of caecilian amphibians has recently been enhanced by the discovery of a radically divergent aquatic caecilian of the Neotropical Typhlonectidae. Atretochoana eiselti is the largest lungless tetrapod and the only lungless caecilian, and it possesses a suite of remarkable cranial modifications that set it apart from all other caecilians. Numerical phylogenetic analyses, using 141 morphological characters, were performed in order to resolve the evolutionary relationships of Atretochoana and representatives of all other typhlonectid genera. These analyses yield a single most parsimonious tree, (Chthonerpeton (Nectocaecilia (Typhlonectes natans, Typhlonectes compressicauda) (Potomotyphlus, Atretochoana)))) , that is both well resolved and, as judged by Bremer support and by bootstrapping, is well supported. This tree is used as a basis for interpreting ecological shifts and associated morphological evolution within the Typhlonectidae. The available data suggest that the rate of morphological evolution in the Atretochoana lineage is significandy greater than that in other typhlonectid lineages.     

One hundred million years of skin feeding? Extended parental care in a Neotropical caecilian (Amphibia: Gymnophiona)

Maternal dermatophagy, the eating of maternal skin by offspring, is an unusual form of parental investment involving co-evolved specializations of both maternal skin and offspring dentition, which has been recently discovered in an African caecilian amphibian. Here we report the discovery of this form of parental care in a second, distantly related Neotropical species Siphonops annulatus, where it is characterized by the same syndrome of maternal and offspring specializations. The detailed similarities of skin feeding in different caecilian species provide strong evidence of its homology, implying its presence in the last common ancestor of these species. Biogeographic considerations, the separation of Africa and South American land masses and inferred timescales of amphibian diversification all suggest that skin feeding is an ancient form of parental care in caecilians, which has probably persisted in multiple lineages for more than 100 Myr. These inferences support the hypotheses that (i) maternal dermatophagy is widespread in oviparous direct-developing caecilians, and (ii) that viviparous caecilians that feed on the hypertrophied maternal oviduct evolved from skin-feeding ancestors. In addition to skin-feeding, young S. annulatus were observed to congregate around, and imbibe liquid exuded from, the maternal cloacal opening.     

Evolution of Cranial Shape in Caecilians (Amphibia: Gymnophiona)

Insights into morphological diversification can be obtained from the ways the species of a clade occupy morphospace. Projecting a phylogeny into morphospace provides estimates of evolutionary trajectories as lineages diversified information that can be used to infer the dynamics of evolutionary processes that produced patterns of morphospace occupation. We present here a large-scale investigation into evolution of morphological variation in the skull of caecilian amphibians, a major clade of vertebrates. Because caecilians are limbless, predominantly fossorial animals, diversification of their skull has occurred within a framework imposed by the functional demands of head-first burrowing. We examined cranial shape in 141 species, over half of known species, using X-ray computed tomography and geometric morphometrics. Mapping an existing phylogeny into the cranial morphospace to estimate the history of morphological change (phylomorphospace), we find a striking pattern: most species occupy distinct clusters in cranial morphospace that closely correspond to the main caecilian clades, and each cluster is separated by unoccupied morphospace. The empty spaces in shape space are unlikely to be caused entirely by extinction or incomplete sampling. The main caecilian clades have different amounts of morphological disparity, but neither clade age nor number of species account for this variation. Cranial shape variation is clearly linked to phyletic divergence, but there is also homoplasy, which is attributed to extrinsic factors associated with head-first digging: features of caecilian crania that have been previously argued to correlate with differential microhabitat use and burrowing ability, such as subterminal and terminal mouths, degree of temporal fenestration (stegokrotaphy/zygokrotaphy), and eyes covered by bone, have evolved and many combinations occur in modern species. We find evidence of morphological convergence in cranial shape, among species that have eyes covered by bone, resulting in a narrow bullet-shaped head. These results reveal a complex history, including early expansion of morphospace and both divergent and convergent evolution resulting in the diversity we observe today.     

The Braincase of Eocaecilia micropodia (Lissamphibia,Gymnophiona) and the Origin of Caecilians

The scant fossil record of caecilians has obscured the origin and evolution of this lissamphibian group. Eocaecilia micropodia from the Lower Jurassic of North America remains the only stem-group caecilian with an almost complete skull preserved. However, this taxon has been controversial, engendering re-evaluation of traits considered to be plesiomorphic for extant caecilians. Both the validity of the placement of E. micropodia as a stem caecilian and estimates of the plesiomorphic condition of extant caecilians have been questioned. In order to address these issues, the braincase of E. micropodia was examined via micro-computed tomography. The braincase is considered to be a more reliable phylogenetic indicator than peripheral regions of the skull. These data reveal significant new information, including the possession of an ossified nasal septum, ossified anterior wall of the sphenethmoid, long anterolateral processes on the sphenethmoid, and paired olfactory nerve foramina, which are known only to occur in extant caecilians; the latter are possibly related to the evolution of the tentacle, a caecilian autapomorphy. A phylogenetic analysis that included 64 non-amniote taxa and 308 characters represents the first extensive test of the phylogenetic affinities of E. micropodia. The results place E. micropodia securely on the stem of extant caecilians, representing a clade within Temnospondyli that is the sister taxon to batrachians plus Gerobatrachus. Ancestral character state reconstruction confirms the braincase of E. micropodia to be largely representative of the plesiomorphic condition of extant caecilians. Additionally, the results refine the context within which the evolution of the caecilian form can be evaluated. The robust construction and pattern of the dermal skull of E. micropodia is interpreted as symplesiomorphic with advanced dissorophoid temnospondyls, rather than being autapomorphic in its robust construction. Together these data increase confidence in incorporating E. micropodia into discussions of caecilian evolution.     

Echinops sahyadricus sp. nov. (Asteraceae: Cardueae), from the northern Western Ghats,Maharashtra, India

The new species Echinops sahyadricus is discovered and described from northern Western Ghats, India. It is endemic to the Maharashtra state and probably restricted to few high mountain peaks in Western Maharashtra. The new species is distinguished from the related E. echinatus by adaxially glabrous to sparsely elgandular hairy leaf surfaces, larger non-cornigerous synflorescences up to 9 cm in diameter and numerous (19–24) glabrous phyllaries up to 27 mm long. An identification key to all Indian taxa of Echinops, illustration and colour plates are provided.     

An insight into the skin glands,dermal scales and secretions of the caecilian amphibian Ichthyophis beddomei

The caecilian amphibians are richly endowed with cutaneous glands, which produce secretory materials that facilitate survival in the hostile subterranean environment. Although India has a fairly abundant distribution of caecilians, there are only very few studies on their skin and secretion. In this background, the skin of Ichthyophis beddomei from the Western Ghats of Kerala, India, was subjected to light and electron microscopic analyses. There are two types of dermal glands, mucous and granular. The mucous gland has a lumen, which is packed with a mucous. The mucous-producing cells are located around the lumen. In the granular gland, a lumen is absent; the bloated secretory cells, filling the gland, are densely packed with granules of different sizes which are elegantly revealed in TEM. There is a lining of myo-epithelial cells in the peripheral regions of the glands. Small flat disk-like dermal scales, dense with squamulae, are embedded in pockets in the dermis, distributed among the cutaneous glands. 1–4 scales of various sizes are present in each scale pocket. Scanning electron microscopic observation of the skin surface revealed numerous glandular openings. The skin gland secretions, exuded through the pores, contain fatty acids, alcohols, steroid, hydrocarbons, terpene, aldehyde and a few unknown compounds.