Overview

Brief Summary

History of Classification

Dermophis mexicanus was originally classified as Siphonops mexicanus in 1841 (Dumeril, 1981). It was reclassified as Amphisbaena versatilis in 1850 (Gray, 1850). In 1880, it was first classified by its current name, Dermophis mexicanus (Peters, 1880). In 1968, it was mistakenly classified as Dermophis eburatus (Taylor, 1968).

Before 1968, all caecilians were classified in a single family, Caeciliaidae (Nussbaum, 1989). Three new families were added in 1968 and 1969: Ichthyophiidae, Typhlonectidae, and Scolecomorphidae; the latter was further divided into Caeciliinae and Dermophiinae, to which D. mexicanus now belongs. In 1980, Dermophiinae was further divided into old Old World and New World varieties; however, this was reversed in 1989 (Nussbaum, 1989). In 2011, a large large-scale phylogenetic analysis of amphibians found Caeciliidae paraphyletic. It also merged Caeciliinae and Typhlonectidae. Despite these results, Caeciliidae is still generally considered a valid family. The NCBI places Dermophis in the family Dermophiidae. However, most other classifications place assign Dermophis to Caeciliidae.

Duméril, A. M. C., and G. Bibron. 1841. Erpétologie Genérale ou Histoire Naturelle Complète des Reptiles. Volume 8. Paris: Librarie Enclyclopedique de Roret.

Gray, J. E. 1850. Catalogue of the Specimens of Amphibia in the Collection of the British Museum. Part II. Batrachia Gradientia, etc. Printed by Order of the Trustees. London: Spottiswoodes and Shaw.

Nussbaum, R. A., and M. Wilkinson. 1989. On the classification and phylogeny of caecilians (Amphibia: Gymnophiona), a critical review. Herpetological Monographs 3: 1.

Peters, W. C. H. 1880 "1879". Über die Eintheilung der Caecilien und insbesondere über die Gattungen Rhinatrema und Gymnopis. Monatsberichte der Königlichen Preussische Akademie des Wissenschaften zu Berlin 1879: 924–945.

Pyron, R. A., and J. J. Wiens. 2011. A large-scale phylogeny of Amphibia including over 2800 species, and a revised classification of extant frogs, salamanders, and caecilians. Molecular Phylogenetics and Evolution 61: 543-83.

Taylor, E. H. 1968. The Caecilians of the World: A Taxonomic Review. Lawrence: University of Kansas Press.

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Comprehensive Description

Description

Adults are large for caecilians (up to 600 mm total length for Guatemalan specimens from the Pacific versant) and relatively stout-bodied (Savage and Wake 2001). Dorsal coloration is dark gray, with a pale venter as well as pale jaw and tentacle markings (Wake 2003). Body annuli (94-112 primary folds and 35-88 secondary folds) are numerous. Annuli are also darkly pigmented ventrally, in sharp contrast to the pale venter (Savage and Wake 2001). The tentacle is located roughly halfway between the eye and nostril, with the tentacular foramen present in the anterior margin of the maxillary bone (Savage and Wake 2001). The orbit is not roofed over by squamosal bone (Savage and Wake 2001). Teeth are present in a single row on the lower jaw, since splenial teeth are lacking (Savage and Wake 2001).

  • Savage, J. M., and Wake, M. H. (2001). ''Reevaluation of the status of taxa of Central American caecilians (Amphibia: Gymnophiona) with comments on their origin and evolution.'' Copeia, 2001(1), 52-64.
  • Wake, M.H. (1980). "Reproduction, growth, and population structure of the Central American caecilian Dermophis mexicanus (Amphibia: Gymnophiona)." Herpetologica, 36, 244-256.
  • Bemis, W. E., Schwenk, K., and Wake, M. H. (1983). ''Morphology and function of the feeding apparatus in Dermophis mexicanus (Amphibia: Gymnophiona).'' Zoological Journal of the Linnean Society, 77, 75-96.
  • Summers, A. P., and O'Reilly, J. C. (1997). ''A comparative study of locomotion in the caecilians Dermophis mexicanus and Typhlonectes natans (Amphibia: Gymnophiona).'' Zoological Journal of the Linnaean Society, 121, 65-76.
  • Wake, M. H. (2003). ''Mexican caecilian, Dermophis mexicanus.'' Grzimek's Animal Life Encyclopedia, Volume 6, Amphibians. 2nd edition. M. Hutchins, W. E. Duellman, and N. Schlager, eds., Gale Group, Farmington Hills, Michigan.
  • Wake, M.H. (1995). ''The spermatogenic cycle of Dermophis mexicanus (Amphibia: Gymnophiona).'' Journal of Herpetology, 29, 119-122.
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Distribution

Range Description

This species is found on the Atlantic slope of southeastern Mexico and disjunctive in eastern Guatemala and northwestern Honduras. It also occurs patchily on the Pacific slope from Oaxaca, Mexico, through Guatemala, El Salvador and Honduras to central Nicaragua. It ranges from near sea level to 1200m asl.
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Distribution and Habitat

This species occurs in Mexico, from the lowlands and mountains of Guerrero on the Pacific versant and Veracruz on the Atlantic versant, southward to northern Panama. It is generally fossorial but is also found on the surface in leaf litter. It prefers to make burrows in moist, friable soil but is able to make use of a diversity of soil types (Wake 1980).

  • Savage, J. M., and Wake, M. H. (2001). ''Reevaluation of the status of taxa of Central American caecilians (Amphibia: Gymnophiona) with comments on their origin and evolution.'' Copeia, 2001(1), 52-64.
  • Wake, M.H. (1980). "Reproduction, growth, and population structure of the Central American caecilian Dermophis mexicanus (Amphibia: Gymnophiona)." Herpetologica, 36, 244-256.
  • Bemis, W. E., Schwenk, K., and Wake, M. H. (1983). ''Morphology and function of the feeding apparatus in Dermophis mexicanus (Amphibia: Gymnophiona).'' Zoological Journal of the Linnean Society, 77, 75-96.
  • Summers, A. P., and O'Reilly, J. C. (1997). ''A comparative study of locomotion in the caecilians Dermophis mexicanus and Typhlonectes natans (Amphibia: Gymnophiona).'' Zoological Journal of the Linnaean Society, 121, 65-76.
  • Wake, M. H. (2003). ''Mexican caecilian, Dermophis mexicanus.'' Grzimek's Animal Life Encyclopedia, Volume 6, Amphibians. 2nd edition. M. Hutchins, W. E. Duellman, and N. Schlager, eds., Gale Group, Farmington Hills, Michigan.
  • Wake, M.H. (1995). ''The spermatogenic cycle of Dermophis mexicanus (Amphibia: Gymnophiona).'' Journal of Herpetology, 29, 119-122.
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Physical Description

Morphology

Dermophis mexicanus has been the subject of a variety of morphological studies. Certain morphological features observed in D. mexicanus are found in distantly related caecilians, and therefore are assumed to apply to all caecilians. Other traits, however, are found exclusively in D. mexicanus. While an overview of basic morphology can be found in the Comprehensive Description section, this section focuses on several specific systems.

Skull

Like most caecilians, D. mexicanus displays many skull modifications adapted for a fossorial lifestyle. Several skull bones are fused to provide structural support for burrowing. The nasal and premaxillary bones fuse to form the naso-premaxilla (Wake, 1982). The maxillary and palatine bones fuse to form the maxillo-palatine. In addition, the pterygoid fuses with the quadrate and the sphenethmoid fuses with the os basale. Dorsally investing bones also overlap anteroposteriorly, but do not completely fuse. While these bones have been heavily ossified, several other bones in the skull remain cartilaginous through adulthood. These include the anterior rims of each nasal capsule, the hyoid apparatus, and the mesethmoid part of the sphenethmoid. Nearly all other skull elements become heavily ossified by adulthood.

Dermophis mexicanus also possesses a retroarticular process extending behind its jaw joint (Bemis, 1983). This bone serves as an attachment to the interhyoideus posterior muscle. If the jaw is open, this huge muscle helps close it, but if the jaw is already closed, the muscle pulls the head up dorsally, which can be used to burrow through hard substrates. Most caecilians have a retroarticular process, but it is particularly pronounced in D. mexicanus and extends all the way to the posterior end of the skull.

The skull in D mexicanus closely resembles the skulls of other genera in both development and adult morphology. Specifically, it has been compared to the genera Ichthyophis, Grandisonia, Hypogeophis, and Gegeneophis. However, there are several features unique to D. mexicanus. For instance, the nasal capsules are fenestrated on their dorsal, ventral, and anterior sides, while in most other caecilians the nasal capsules are roofed. Additionally, the ascending processes on the palatoquadrate is missing in D. mexicanus, while the pterygoid process is highly reduced and only appears late in development. These processes are present and well developed in nearly all other species, including the genera listed above.

Wake, M. H., and J. Hanken. 1982. The development of the skull of Dermophis mexicanus (Amphibia: Gymnophiona), with comments on skull kinesis and amphibian relationships. Journal of Morphology 173: 203–233.

Bemis, W. E., K. Schwenk, and M. H. Wake. 1983. Morphology and function of the feeding apparatus in Dermophis mexicanus (Amphibia: Gymnophiona). Zoological Journal of the Linnean Society 77: 75-96.

Feeding Apparatus

Dermophis mexicanus has similar feeding morphology to most other vertebrates. Therefore, analysis of its feeding morphology and behavior is often generalized to all caecilians; nevertheless, the research was conducted on this specific species.

The lower jaw is comprised of two bones: the anterior pseudodentary and the posterior pseudoangular. These two bones have a 57% overlap and act as a single rigid unit. The joint is formed by an articular process on the quadrate, which fits into a cartilage-lined groove in the pseudoangular. The joint itself is enclosed by sturdy connective tissue. The articular facet lies at a 45-degree angle to the lower jaw, which restricts lateral and anteroposterior movement.

The retroarticular process is a posterior extension of the lower jaw unique to caecilians. In D. mexicanus, it extends for about a third of the total length of the lower jaw. When the jaw is open, this process points dorsally, but when closed, it points posteriorly. It serves as an attachment for three muscles involved in mandibular articulation: the interhyoideus posterior, the levator mandibulae posterior, and the depressor mandibulae.

The depressor mandibulae acts to open the jaw, while the other two are involved in closing the jaw. Additionally, the longus capitis muscles depress the cranium at the cranio-vertebral joint, which also helps close the jaw. The combination of these three muscles for jaw closing results in a huge biting force. It is thought that these additional muscles, as well as the retroarticular process, evolved to increase bite force without increasing cross-sectional area, which is a common trend in fossorial species.

Dermophis mexicanus possess two rows of arrow-shaped teeth on their upper jaw, and one row on the lower jaw. The row on the lower jaw fits between the two rows of the upper jaw. Each row contains 23-33 teeth. Each tooth crown has a flexible connection to the pedicel, which allows the teeth to fold slightly inward but not outward. As a result, struggling prey are likely to pull themselves further into the mouth without being able to escape.

The craniovertebral joint of D. mexicanus is similar to that of other caecilians but differs from all other amphibians. Caecilians lack the tuberculum interglenoideum. Additionally, the skull is firmly connected to the atlas vertebra by ligaments. This joint allows dorsoventral movement but not lateral movement. Dermophis mexicanus can make limited lateral head movements; however, this motion does not arise at the atlas and instead uses the joints of the first 6-10 vertebrae.

Bemis, W. E., K. Schwenk, and M. H. Wake. 1983. Morphology and function of the feeding apparatus in Dermophis mexicanus (Amphibia: Gymnophiona). Zoological Journal of the Linnean Society 77: 75-96.

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Diagnostic Description

Species in the genus Dermophis are relatively robust, with an average length to width ratio of 15-34. They have visible eyes, and their chemosensory tentacles are located halfway between their eye and their nostril. They also lack a terminal vertical keel and an unsegmented terminal shield. Their eyes fit in a socket but are not fully covered by bone. The anterior margin of their maxillopalatine contains a tenticular foramen. They also lack temporal fossae, narial plugs, splenial teeth, and the diastema between vomerine and palatine teeth. Dermophis mexicanus is often confused with Gymnopis multiplicata. However, it can be differentiated by its tentacle: in D. mexicanus, the tentacle is located halfway between the eye and the nostril, while in G. multiplicata, the tentacle is located directly anterior to the eye.

Savage, J. M.. 2002. The Amphibians and Reptiles of Costa Rica: A Herpetofauna between Two Continents, between Two Seas. Chicago: University of Chicago Press.

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Development

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Ecology

Habitat

Southern Pacific Dry Forests Habitat

This taxon is found in the Southern Pacific dry forests ecoregion, which is situated along the southeastern versant of the Sierra Madre del Sur Mountains including the Pacific Ocean coastal plain. These forests are a key locus of endemism for butterflies, and has the greatest diversity of scorpions and spiders in the entirety of Mexico. This ecoregion is classified in the Tropical and Subtropical Dry Broadleaf Forests biome. The Southern Pacific dry forests exhibit a moderate to high faunal species richness; for example, there are a total of 744 vertebrate taxa recorded in the ecoregion, with a particularly large number of endemic reptiles.

The ecoregion elevation ranges from sea level to 1400 metres. The climate is tropical and dry, with precipitation levels of 800 millimetres (mm) per annum. There is an extended arid season, which factor drives the prevalence of deciduous vegetation. The forests grow chiefly on shallow, well-drained soils derived from limestone. Closer to the base of the Sierra Madre del Sur Mountains, the soils are more rocky, and are derived from igneous rocks.

The dominant plant species include Mauto (Lysiloma divaricatum), Bursera excelsa and Fragrant Bursera (B. fagaroides), which are typically found in association with Pochote (Ceiba aesculifolia), Comocladia engleriana, and Trichilia americana. In the Mexican state of Michoacán, the macro plant species more generally in evidence are Ficus insipida, F. pertusa, Breadnut (Brosimum alicastrum), Licania arborea, Sideroxylon capiri and Elephant Ear (Enterolobium cyclocarpum).

There are a number of anuran species present in the ecoregion, including: Blunt-toed Chirping Frog (Eleutherodactylus modestus VU); Cloud Forest Stream Frog (Ptychohyla euthysanota NT), found from southeast Oaxaca to Guatemala and eastern El Salvador; Matuda's Spikethumb Frog  (Plectrohyla matudai VU). A special status caecilian found in the ecoregion is the Mexican Caecilian (Dermophis mexicanus VU), a fossorial species that can attain lengths up to sixty centimetres. A special status salamander found in the ecoregion is the Sierra Juarez Salamander (Pseudoeurycea juarezi CR), a near-endemic known only between Cerro Pelón and Vista Hermosa in the Sierra de Juarez, north-central Oaxaca. The White-lipped Peeping Frog (Eleutherodactylus albolabris CR), a near-endemic known chiefly from Agua del Obispo, central Guerrero.

The Southern Pacific dry forests contain numerous reptilian taxa, including the following endemics: Bocourt's Anole (Norops baccatus); Taylor's Anole (Norops taylori), known only to  Puerto Marquez area, in northern Acapulco, Guerrero; Simmons' Anole (Anolis simmonsi), restricted to the vicinity of Pinotepa Nacional, Oaxaca; Stegneger's Blackcollar Spiny Lizard (Sceloporus stejnegeri), restricted to the Pacific versant in the state of Guerrero, Mexico; Red Earth Snake (Geophis russatus), found in a very narrow range outside of Putla, Oaxaca; Sierra Mije Earth Snake (Geophis anocularis), known only from around Totontepec on the Atlantic versant of the Sierra Mixe, Oaxaca; Ramirez`s Hooknose Snake (Ficimia ramirezi), restricted to the Pacific versant of the Isthmus of Tehuantepec, Niltepec, Oaxaca; Halberg's Cloud Forest Snake (Cryophis hallbergi), found only in northern Oaxaca, at Sierra de Juarez and Sierra Mazateca; Isthmian Earth Snake (Geophis isthmicus), known only from the vicinity of Tehuantepec, Mexico; the endemic Macdougall's Spiny Lizard (Sceloporus macdougalli).

Characteristic mammalian fauna include the endemic Oaxacan Pocket Gopher (Orthogeomys cuniculus), restricted to several sites on the Isthmus of Tehuantepec, Oaxaca. Other mammals seen in the ecoregion include the: Lesser Long-nosed Bat (Leptonycteris yerbabuenae VU), Tropical Hare (Lepus flavigularis EN), restricted to Salina Cruz, Oaxaca to the extreme west of  Chiapas; Greater Bulldog Bat (Noctilio leporinus), Coati (Nasua narica), Buller’s Pocket Gopher (Pappogeomys bulleri), Javelina (Tayassu tajacu), and Mexican Long-tongued Bat (Choeronycteris mexicana NT).

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Habitat and Ecology

Habitat and Ecology
This species lives in humid to dry soils beneath leaf-litter, logs, banana or coffee leaves and hulls or similar ground cover. In El Salvador it is present in dry forest and savanna between sea level and 900m asl (Köhler et al., 2006). It is adaptable to secondary habitats. It is a viviparous species.

Systems
  • Terrestrial
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Life History and Behavior

Behavior

Feeding

Dermophis mexicanus, and indeed most fossorial caecilians, are “sit and wait” predators. When they approach prey, they do so very slowly, and they do not pursue fleeing prey. They capture prey with their powerful jaws. Most caecilian prey is elongate, and is thinner than the caecilian itself. Earthworms are a very common prey item, and there is a population in Guatemala found to feed exclusively on earthworms.

Normally, D. mexicanus and most other caecilians feed via a static pressure system. The animal captures and crushes prey with its powerful jaw, and then swallows the prey whole. Ingestion is a fairly continuous process alternating between biting and swallowing motions. However, when capturing prey while partially emerged from its burrow, D. mexicanus has been observed spinning back into the burrow in a corkscrew, and shearing the prey against the sides of the burrow.

Bemis, W. E., K. Schwenk, and M. H. Wake. 1983. Morphology and function of the feeding apparatus in Dermophis mexicanus (Amphibia: Gymnophiona). Zoological Journal of the Linnean Society 77: 75-96.

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Life Cycle

Development

Like all amphibians, D. mexicanus develops a cartilaginous skeleton and skull, which then become ossified during development. By the time fetuses are about 30 mm long, they already have a well developed chondrocranium and Meckel’s cartilage, including a pronounced articular facet and a retroarticular process. The articular facet and the quadrate begin ossifying around this time.

By the time fetuses are about 40 mm long, the opposing articular surfaces of their Meckel’s cartilage and palatoquadrate have started ossifying. These processes will form the jaw joint. This is important because the fetuses have access to a limited amount of egg yolk. When the yolk runs out, the fetus begins to feed on the interior lining of the uterus, and need well-developed jaws and teeth by this point. By the time the fetuses reach about 50 mm, their jaw joints have nearly finished ossifying.

When the fetuses reach about 60 mm in length, most of their chondrocranium has eroded, and Meckel’s cartilage is eroding medially. However, the nasal capsules continue to chondrify. The anterior rims of the nasal capsules will remain permanently cartilaginous. By the time they reach 70 mm, most of the cartilage has ossified and only isolated patches of cartilage remain.

When fetuses are 70 mm long, their nasal bones are beginning to fuse with the premaxillae, the pterygoids begin fusing with the quadrates, and the prefrontal and maxilla begin to fuse. Additionally, the fetuses have already developed several rows of teeth with well-mineralized pedicels. This allows them to feed on the internal uterine linings.

When the fetuses reach 105 mm in length, their skulls begin to elongate and flatten. In addition, most bones are becoming thicker and more ossified.

The development of the chondrocranium in D. mexicanus is remarkably similar to its development in the genera Ichthyophis, Grandisonia, Hypogeophis, and Gegeneophis. However, the ossification process differs in D. mexicanus. While several of these genera display early ossification of jaw suspension elements. However, the specific bones that ossify first, in particular the Meckel’s cartilage, differ between D. mexicanus and the other genera. In addition, D. mexicanus has lost several primary ossification sites that are present in all other caecilians, including the quadratojugal, postparietal, lacrimal, periorbital, ectopterygoid, and interparietal elements. Instead, the fusion of multiple ossification centers forms the single median os basale.

The skulls of developing D. mexicanus are also highly kinetic. In particular, the quadrate is highly moveable because it ossifies before any of the bones around it. This allows fetal jaw movement, which assists in feeding on the uterine lining. Skull kinesis is highly reduced by adulthood, although the adult skulls are still streptostylic and slightly kinetic.

Wake, M. H., and J. Hanken. 1982. The development of the skull of Dermophis mexicanus (Amphibia: Gymnophiona), with comments on skull kinesis and amphibian relationships. Journal of Morphology 173: 203–233.

Metamorphosis

Metamorphosis from the larval to adult stage in D. mexicanus occurs in the last 4-5 months of gestation. By the time they are born, they have completed metamorphosis and emerge in their adult morphs.

Larval fetuses have long gill filaments that branch into groups of three. They keep these gills for slightly more than half of the 11-month gestation period. After 5-6 months of gestation, the gills are reabsorbed, although the spiracle stays open until about the eighth month of gestation.

Fetal teeth are present at hatching, 2.5-3 months into gestation. The fetus continues to add teeth and rows until birth, at which point they lose their larval teeth and start developing adult teeth. The loss of fetal teeth marks the end of metamorphosis.

Wake, M. H. 2014. Fetal adaptations for viviparity in amphibians. Journal of Morphology. In press.

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Life Expectancy

Lifespan, longevity, and ageing

Maximum longevity: 13.8 years (captivity)
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Evolution and Systematics

Functional Adaptations

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Molecular Biology and Genetics

Molecular Biology

Barcode data: Dermophis mexicanus

The following is a representative barcode sequence, the centroid of all available sequences for this species.


There is 1 barcode sequence available from BOLD and GenBank.   Below is the sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.  See the BOLD taxonomy browser for more complete information about this specimen.  Other sequences that do not yet meet barcode criteria may also be available.

TCTCGTTGATTTTTTTCAACTAATCATAAAGACATTGGCACCCTATATTTAATCTTTGGTGCTTGAGCTGGAATAGTGGGGACTGCGCTA---AGTCTTCTAATTCGTGCTGAATTAAGCCAACCAGGCACATTATTAGGAGAT---GATCAAATTTACAATGTAGTAGTAACCGCCCATGCTTTCATTATAATTTTCTTTATAGTAATACCAATTATAATTGGCGGATTTGGTAATTGGTTAGTACCGTTAATA---ATTGGTGCTCCTGATATAGCCTTCCCACGAATGAACAATATAAGTTTTTGACTTCTCCCCCCATCATTATTACTATTAGTAGCATCATCAAGTGTAGAAGCCGGTGCAGGTACAGGTTGAACCGTATACCCACCACTAGCCAGTAACCTAGCCCATGCTGGAGCATCAGTTGATTTA---ACAATCTTCTCACTCCACTTAGCTGGTGTATCATCAATTTTAGGTGCTATCAACTTTATTACAACAATTATTAATATAAAACCACCATCAATATCTCAATATCAAACCCCTTTATTTGTTTGATCAGTTCTAGTAACTGCAGTATTATTATTATTATCCTTACCAGTTCTAGCTGCA---GGTATCACAATATTACTTACAGATCGTAATATTAATACCACATTCTTTGATCCAGCAGGCGGTGGTGACCCTATTTTGTACCAACATTTATTTTGATTTTTTGGACACCCAGAAGTATATATCTTAATTCTTCCAGGATTCGGAATAATTTCTCACATCGTTACATATTATTCCGGAAAAAAA---GAACCATTTGGATATATAGGTATAGTATGGGCCATAATATCAATTGGTTTTTTAGGATTTATCGTTTGAGCTCACCATATATTTACTGTAGGTATAAATGTAGATACCCGAGCATATTTTACCTCTGCAACAATAATTATTGCTATCCCAACAGGTGTAAAAGTATTTAGCTGATTA---GCAACTTTACATGGAG
-- end --

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Statistics of barcoding coverage: Dermophis mexicanus

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 1
Specimens with Barcodes: 2
Species With Barcodes: 1
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
VU
Vulnerable

Red List Criteria
A2ac

Version
3.1

Year Assessed
2004

Assessor/s
Georgina Santos-Barrera, Marvalee Wake, John Measey, Mark Wilkinson

Reviewer/s
Global Amphibian Assessment Coordinating Team (Simon Stuart, Janice Chanson, Neil Cox and Bruce Young)

Contributor/s

Justification
Listed as Vulnerable because of a population decline, estimated to be possibly more than 30% over the last ten years, inferred from observed decline at known sites, shrinkage in distribution, and habitat destruction and degradation.
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Population

Population
This species was once common in parts of its range, it is now much diminished in areas of previous abundance (such as near San Marcos, Guatemala) (Marvalee Wake pers. comm., 2007). It is possible that this species may have declined considereably more than 30% over the past ten years or three generation, this is likley to be a conservative estimate (Marvalee Wake pers. comm., 2007). There have been no new records for in Veracruz and Tabasco since around the 1950s, although there has been limited collecting in these areas (Marvalee Wake pers. comm., 2007).

Population Trend
Decreasing
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Life History, Abundance, Activity, and Special Behaviors

Dermophis mexicanus spends much of its time in burrows in moist, loose soil (Wake 2003). However, it also forages on the surface, often emerging at dusk if there is a light rain (Wake 2003). D. mexicanus is a sit-and-wait predator with a diet composed of soil or leaf-litter invertebrates (e.g., earthworms, termites, orthopteran instars) and perhaps occasional vertebrates (smaller lizards and baby mice, depending on the size of the individual caecilian) (Wake 2003). Feeding mechanics have been studied (e.g., Bemis et al. 1983).

D. mexicanus constructs its own burrow (Wake 2003). Modes of locomotion include internal concertina motion and lateral undulation (Summers and O'Reilly 1997).

Sexual maturity occurs at two to three years of age. How mates are attracted and whether they undergo courtship is not known. As is the case for all caecilians, Dermophis mexicanus has internal fertilization, with the male extruding the rear part of the cloaca into the female's cloaca to transfer sperm. Although males can produce sperm nearly year-round (11 months; Wake 1995), females in a given population show synchronous development of embryos in the oviduct, implying that there is a short and synchronized breeding period but no sperm storage. Embryos are small (2 mm in diameter) and feed on the egg yolk supply for only about three months of gestation before the yolk supply is exhausted. At that point the mother makes a nutritious secretion from internal oviduct glands. Fetal caecilians move around within the oviduct and have specialized dentition with which they scrape the oviduct skin in order to stimulate and ingest the mother's nutritive secretion. The dentition is shed at birth and a quite different adult dentition is rapidly acquired within a few days. Fetuses also have elaborate tri-branchiate gills (Wake 2003).

Pregnancies are 11 months long and this species is viviparous. Females give birth to three to sixteen young when the rainy season begins in May/June. Newborns measure 10-15 cm in length, while the mother herself is only 30-45 cm long (Wake 2003).

  • Savage, J. M., and Wake, M. H. (2001). ''Reevaluation of the status of taxa of Central American caecilians (Amphibia: Gymnophiona) with comments on their origin and evolution.'' Copeia, 2001(1), 52-64.
  • Wake, M.H. (1980). "Reproduction, growth, and population structure of the Central American caecilian Dermophis mexicanus (Amphibia: Gymnophiona)." Herpetologica, 36, 244-256.
  • Bemis, W. E., Schwenk, K., and Wake, M. H. (1983). ''Morphology and function of the feeding apparatus in Dermophis mexicanus (Amphibia: Gymnophiona).'' Zoological Journal of the Linnean Society, 77, 75-96.
  • Summers, A. P., and O'Reilly, J. C. (1997). ''A comparative study of locomotion in the caecilians Dermophis mexicanus and Typhlonectes natans (Amphibia: Gymnophiona).'' Zoological Journal of the Linnaean Society, 121, 65-76.
  • Wake, M. H. (2003). ''Mexican caecilian, Dermophis mexicanus.'' Grzimek's Animal Life Encyclopedia, Volume 6, Amphibians. 2nd edition. M. Hutchins, W. E. Duellman, and N. Schlager, eds., Gale Group, Farmington Hills, Michigan.
  • Wake, M.H. (1995). ''The spermatogenic cycle of Dermophis mexicanus (Amphibia: Gymnophiona).'' Journal of Herpetology, 29, 119-122.
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Threats

Major Threats
It is an adaptable species but threatened by habitat loss, and changes in agricultural methods (such as the transformation of shaded coffee plantations to open plantations). It is confused with snakes in some areas, and so it persecuted locally. It sometimes appears in the international pet trade, but not at a level to constitute a threat to the species.
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Life History, Abundance, Activity, and Special Behaviors

Although this species remains locally abundant in some localities, its habitat is being altered or destroyed as deforestation occurs. It does seems to adapt well to some kinds of farm use. For instance, this species is abundant on some coffee fincas where the coffee hulls are piled up to decay, resulting in the kind of moist organic soil in which Dermophis (along with its primary food, earthworms) thrives (Wake 2003).

  • Savage, J. M., and Wake, M. H. (2001). ''Reevaluation of the status of taxa of Central American caecilians (Amphibia: Gymnophiona) with comments on their origin and evolution.'' Copeia, 2001(1), 52-64.
  • Wake, M.H. (1980). "Reproduction, growth, and population structure of the Central American caecilian Dermophis mexicanus (Amphibia: Gymnophiona)." Herpetologica, 36, 244-256.
  • Bemis, W. E., Schwenk, K., and Wake, M. H. (1983). ''Morphology and function of the feeding apparatus in Dermophis mexicanus (Amphibia: Gymnophiona).'' Zoological Journal of the Linnean Society, 77, 75-96.
  • Summers, A. P., and O'Reilly, J. C. (1997). ''A comparative study of locomotion in the caecilians Dermophis mexicanus and Typhlonectes natans (Amphibia: Gymnophiona).'' Zoological Journal of the Linnaean Society, 121, 65-76.
  • Wake, M. H. (2003). ''Mexican caecilian, Dermophis mexicanus.'' Grzimek's Animal Life Encyclopedia, Volume 6, Amphibians. 2nd edition. M. Hutchins, W. E. Duellman, and N. Schlager, eds., Gale Group, Farmington Hills, Michigan.
  • Wake, M.H. (1995). ''The spermatogenic cycle of Dermophis mexicanus (Amphibia: Gymnophiona).'' Journal of Herpetology, 29, 119-122.
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Management

Conservation Actions

Conservation Actions
It occurs in many protected areas. This species is protected by Mexican law under the "Special Protection" category (Pr).
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Relevance to Humans and Ecosystems

Risks

Relation to Humans

It is of value to humans because of its ability to turn soil as it burrows, and because it consumes insects among other prey (Wake 2003).

  • Savage, J. M., and Wake, M. H. (2001). ''Reevaluation of the status of taxa of Central American caecilians (Amphibia: Gymnophiona) with comments on their origin and evolution.'' Copeia, 2001(1), 52-64.
  • Wake, M.H. (1980). "Reproduction, growth, and population structure of the Central American caecilian Dermophis mexicanus (Amphibia: Gymnophiona)." Herpetologica, 36, 244-256.
  • Bemis, W. E., Schwenk, K., and Wake, M. H. (1983). ''Morphology and function of the feeding apparatus in Dermophis mexicanus (Amphibia: Gymnophiona).'' Zoological Journal of the Linnean Society, 77, 75-96.
  • Summers, A. P., and O'Reilly, J. C. (1997). ''A comparative study of locomotion in the caecilians Dermophis mexicanus and Typhlonectes natans (Amphibia: Gymnophiona).'' Zoological Journal of the Linnaean Society, 121, 65-76.
  • Wake, M. H. (2003). ''Mexican caecilian, Dermophis mexicanus.'' Grzimek's Animal Life Encyclopedia, Volume 6, Amphibians. 2nd edition. M. Hutchins, W. E. Duellman, and N. Schlager, eds., Gale Group, Farmington Hills, Michigan.
  • Wake, M.H. (1995). ''The spermatogenic cycle of Dermophis mexicanus (Amphibia: Gymnophiona).'' Journal of Herpetology, 29, 119-122.
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Wikipedia

Mexican burrowing caecilian

The Mexican burrowing caecilian (Dermophis mexicanus) is a species of limbless amphibian in the family Dermophiidae. It is found in Mexico and Central America, where it burrows under leaf litter and plant debris.

Description[edit]

The adult Mexican burrowing caecilian grows to a length of 30 to 50 cm (12 to 20 in).[2] In general appearance, it resembles a large earthworm. Around a hundred transverse annular folds in the skin give the appearance of segments. The head has a pointed snout, a single row of teeth in the lower jaw, and two vestigial eyes covered with skin, with a pair of protrusible tentacles between the eyes and the nostrils. The body is elongated and there are no limbs. The upper surface is dark grey and the under surface pale grey with darker markings on the annuli.[3]

Distribution and habitat[edit]

The Mexican burrowing caecilian is found in Mexico, Guatemala, El Salvador, Honduras, Nicaragua, and possibly Belize, mostly on the Atlantic side, but also in some isolated parts of the Pacific slope. Its natural habitats are subtropical or tropical dry forests, moist lowland forests, moist montane forests, plantations, rural gardens, and heavily degraded former forests. It is fossorial, living in damp, loose soil and under leaf litter, logs, and plant debris, often in banana and coffee plantations. It is found at altitudes of up to 1,200 m (3,900 ft) above sea level.[1]

Biology[edit]

The Mexican burrowing caecilian feeds on invertebrates, including earthworms, termites, crickets, slugs, and snails.[2] It emerges onto the ground surface on nights with light rainfall and catches small prey that come within its reach. Larger individuals may eat mice and small lizards. It moves by internal concertina-like movements and by undulating its body from side to side.[3]

This caecilian is viviparous. Fertilisation is internal and up to 16 developing larvae subsist on the yolks of their eggs for three months. Then, they develop rasping teeth and feed on maternal glandular secretions, scraping the inside of the oviduct to stimulate their production.[3] When they emerge, after 11 months of gestation, they are 10 to 15 cm (3.9 to 5.9 in) long. They then shed their larval teeth and rapidly grow a set of adult ones.[3]

Status[edit]

The Mexican burrowing caecilian is listed as Vulnerable in the IUCN Red List of Threatened Species, because it is thought that numbers have declined by more than 30% over the last ten years. It has several disjunct populations, and in areas where it used to be abundant it now seems to be less common, and the locations in which it is found seem to be fewer in number. It may be persecuted in some locations because it superficially looks like a snake.[1]

References[edit]

  1. ^ a b c Santos-Barrera, Georgina; Wake, Marvalee; Measey, John; Wilkinson, Mark (2004). "Dermophis mexicanus". IUCN Red List of Threatened Species. Version 2012.1. International Union for Conservation of Nature. Retrieved 2012-08-26. 
  2. ^ a b Gosselin-Ildari , Ashley. "Dermophis mexicanus, Mexican Burrowing Caecilian". Digimorph. Stony Brook University. Retrieved 2012-08-26. 
  3. ^ a b c d Chantasirivisal, Peera (2005-09-27). "Dermophis mexicanus". AmphibiaWeb. Retrieved 2012-08-26. 
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Names and Taxonomy

Taxonomy

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