First record of the Mountain Caecilian Gymnopis syntrema (Amphibia: Gymnophiona: Dermophiidae) in Mexico

Abstract

We document the first record of Gymnopis syntrema (Dermophiidae) for Mexico. A single individual was found in the Montes Azules Biosphere Reserve, Lacandona region, in the southeast of Mexico. The specimen was collected in an old-growth forest site at the beginning of the rainy season on May, 2012 and extends former known distribution 88 km west from the nearest locality in Guatemala. We also present an updated distribution map of the species based on all known records of the species to date. With this new record, the number of amphibian species in Mexico increases to 377.

Resumen

Presentamos el primer registro de Gymnopis syntrema (Dermophiidae) para México. Se encontró un único individuo en la Reserva de la Biosfera Montes Azules, en la región de la lacandona, al sureste de México. El ejemplar fue recolectado en mayo de 2012 en bosque maduro al inicio de la temporada de lluvias, extendiendo la distribución conocida de la especie 88 km al oeste de su localidad más cercana en Guatemala. Presentamos un mapa actualizado de la especie basado en todos los registros conocidos a la fecha. Con este nuevo registro, el número de especies de anfibios en México se incrementa a 377.

Caecilians (Order Gymnophiona) are the most poorly known amphibians because of their low abundance and secretive habits. They are a highly specialized, limbless group with a long annulated body and sensitive tentacles on either side of the snout. Most species are tropical, fossorial predators with a great diversity in shape, ecology, and reproductive habits (Zug et al., 2001; Vitt and Caldwell, 2009).

Of the 4 known genera of the family Dermophiidae only Dermophis and Gymnopis are Mesoamerican endemics, of which only Dermophis glandulosus extends to northern Colombia (Wilkinson et al., 2011). Prior to this report, only 2 species of the genus Dermophis, D. mexicanus and D. oaxacae were known from Mexico; and the 2 species of the genus Gymnopis, G. multiplicata and G. syntrema were restricted to Central America (Wilkinson et al., 2011). Both genera inhabit low and intermediated elevations of tropical premontane regions from sea level to 900 m elevation in southern Mexico and Guatemala, and up to 1400 m elevation in Costa Rica and western Panama (Savage and Wake, 1972).

The mountain caecilian Gymnopis syntrema is called in Guatemala talpacua (Campbell, 1998). As described by Wake and Campbell (1983), Lee (2000) and Campbell (1998), it is moderately small and thin, from 250 to 307 mm in total length. The head and body are similar in width, the snout is rounded in dorsal view and the upper jaw is protracted beyond the lower jaw. The eyes are reduced, visible as spots or with the orbit sometimes covered with skin or even the squamosal bone, and the sensorial tentacle is in front of the eye. The primary rings vary from 128 to 132 and the secondary rings from 63 to 93 (193 to 132 in total). It has small scales between the primary and secondary rings, which increase in size posteriorly. The tail has a rounded end.

Because of its shape and coloration, this small, thin amphibian species can be easily confused with earthworms. The head and anterior portion of the body are normally pink, but the coloration of some specimens varies from dark grey, to brown or black, limiting the pink coloration to the ventral surface of the head. The ventral surface of the head can also be light gray or brownish yellow (Campbell, 1998). As with other caecilians, Gymnopis syntrema burrows in loose soil in primary and secondary vegetation in humid tropical or subtropical forest, between 400 and 1 000 m in elevation. Most of the life history data remain unknown. It is thought to feed on worms and perhaps other soil invertebrates and reproduction is thought to be similar to that of G. multiplicata, which produces from 2 to 12 offspring (Lee, 2000; Campbell, 1998). Gymnopis syntrema is rarely seen in the wild, although Acevedo et al. (2004) reported that many specimens, deposited at the University of Texas at Arlington (UTA), were dug out by a bulldozer in Chichipate, Izabal, eastern Guatemala. Apparently, eleven of these specimens are the ones used by Ducey et al. (1993) in burrowing behavior experiments.

Gymnopis syntrema appears to be thoroughly reported patchily in central Guatemala and southern Belize (Campbell, 1988). So far we have found only 6 specimens reported with accurate locality data at the Global Biodiversity Information Facility (GBIF, 2012), BERDS (2012), and the reference collection of the Biology Department in the Universidad del Valle, Guatemala (UVG). Reported localities for Guatemala are: ca. 8 Km south east Chisec, Alta Verapaz, GBIF: 15°45' N, 90°15' W (Staatliches Museum für Naturkunde Stuttgart, SMNS: Herpetologie: 2245); Finca El Volcán, Alta Verapaz, ca. 15°30'10” N, 89°51'42” W (Savage and Wake, 2001); Aldea Vista Hermosa, Los Amates, Izabal, GBIF: ca. 15°15'20” N, 89°05'48” W 650 m elev. (Kansas University, Herpetology, KUH: 189566, possibly same as in Savage and Wake, 2001); Finca Semuc, Sierra de Santa Cruz, El Estor, Izabal, 15°40'0.12” N, 89°28'59.88” W and 15°41'32.28” N, 89°21'7.92” W, 500 m elev. (Universidad del Valle, Guatemala, UVG 507 and UVG 929); and, Chichipate, southern Sierra de Santa Cruz, Izabal, ca. 15°28'34” N, 89°27'54” W (Acevedo et al., 2004 specimens at the University of Texas at Arlington, UTA). Campbell (1998) reported this species from the Sierra de las Minas, Izabal, ca. 15°17'34” N; 89°28'17” W (see also Frost, 2011); Sierra de Chinajá in Petén, Alta Verapaz, ca. 15°58'21” N, 90°12'05” W; and, from the Sierra de Merendón (uncertain locality, possibly in Chiquimula province) (Fig. 1). In Belize it was reported from the Mayan Mountains: Upper Raspaculo River, Chiquibul, Cayo, ca. 16°47' N, 88°55'24”W, elev. 600 m (BERDS: Specimen ID: 90758; Rogers and Sutton, 1991; Stafford, 1994; Lee 1996) Fig. 1). The map provided by the IUCN (Acevedo et al., 2004) is far from complete, restricting the distribution of G. syntrema around Lake Izabal and Belize, ignoring all other Guatemalan records. Cope (1866) described the type locality of the species from “the neighbouring region of Honduras” and Taylor (1968) later referred it to “the northern coast of Honduras”. That the distribution of this species might extend to Honduras has been mentioned in the literature, but no documented record exists and it is not listed in the most recent Honduran herpetofaunal lists (e.g., Townsend and Wilson, 2010).

Figure 1.

Distribution map of Gymnopis syntrema based upon reported specimens. Belize: (a) Chiquibul, Cayo. Guatemala: (b) Sierra de Chinajá, Alta Verapaz; (c) Chisec, Alta Verapaz; (d) Finca El Volcán, Alta Verapaz; (e, f) Finca Semuc, Sierra de Santa Cruz, El Estor, Izabal; (g) Chichipate, Izabal; (h) Sierra de las Minas, Izabal; (i) Los Amates, Izabal (j); Sierra de Merendón (possibly Chiquimula). México: (k) Ocosingo, Chiapas.

Here, we report the first record of the caecilian Gymnopis syntrema in Mexico. The specimen was found on May 25th, 2012 in Ruinas location at the Montes Azules Biosphere Reserve, Municipality of Ocosingo, Chiapas, Mexico, (16°06'35.21” N, 91°00'59.10” W; Datum= WGS84; 300 m elev.; Fig. 1). The specimen was found on the ground, near the edge of a small stream within pristine tropical rainforest in the early rainy season during an afternoon storm. Associated microenvironmental conditions at the site were: average temperature at 1.5 m of the ground= 24.48 ± 2.21 °C (max = 31.52 °C; min = 20.19 °C); and, average humidity at 1.5 m from the ground= 96.99 ± 5.6% (Max. 100%; Min. 69.6%). In addition we characterized the vegetation structure: litter percentage average, 49.5% (SD 13.8%); average of number of trees with a diameter at breast height larger than 30 cm, 1.16 per 4 m² (SD 0.7); average of palms, 4.6 per 4 m² (SD 2.8) and average of ferns 3.5 per 4 m² (SD 3.7). Temperature and humidity values were measured with data-loggers placed in the site during dry season (March) and wet season (August), 2011, and from May to July, 2012.

This is the first definite report for both the genus and the species for Mexico and the westernmost report for the species. It extends the known distribution 88 km west from the nearest locality in the Sierra de Chinajá in Petén, Guatemala (ca. 15°58'21” N, 90°12'05” W; Campbell, 1998) and is the lowest known elevation record at 300 m. The specimen (Fig. 2) was deposited in the Colección Nacional de Anfibios y Reptiles in the Instituto de Biología of the Universidad Nacional Autónoma de México under the accession number CNAR-IBH 26015.

Figure 2.

Specimen CNAR-IBH 26015, first finding of the caecilian Gymnopis syntrema in Mexico from Ruinas at the Montes Azules Biosphere Reserve, Municipality of Ocosingo, Chiapas, southern Mexico (16°06'35.21” N, 91°00'59.10” W; 300 m elev.).

According to Taylor (1968)Siphonops oligozonus described by Cope (1877) and synonymized by Nussbaum (1988) with Gymnopis syntrema was described from a specimen of “uncertain” locality, possibly Chiapas or Tehuantepec in Mexico. According to Cochran (1961) the specimen USNM 25187 is the holotype designated by Cope (1877) for S. oligozonus. This specimen, however, does not have any associated locality information to verify where it was collected (Smithsonian, 2012).

The new specimen has a long and slender body distinctively different from the stouter Gymnopis multiplicata. The eye is covered by skin and the tactile tentacle is placed just below the eye, far posterior to the nostril. It has 126 primary rings and 69 secondary rings, and the tail is rounded and restricted to the posterior end of the body. The rings are pink contrasting with the reddish-brownish folds. The head and the tail are pink and the venter is slightly paler than the dorsum.

Gymnopis syntrema is listed as Data Deficient in the IUCN red list, and it is not listed in CITES. This species should be immediately placed on the Mexican protected species list NOM-059-SEMARNAT (Semarnat, 2010) as it is a rare and restricted species endemic to western Central America with a very limited distribution within Mexico. In addition, deforestation rates in some regions of the Lacandona Forest are high (Mendoza and Dirzo, 1999; Couturier et al., 2012), and it is still unknown if the species is distributed widely within the Montes Azules Biosphere Reserve.

Prior to our report 376 amphibian species were known within the Mexican territory (Parra-Olea et al., 2014); now the number of known species has increased to 377.

Acknowledgements

We thank J. A. Campbell for providing some information regarding locality data and M. G. Palomo for providing locality data from the reference collections at the Universidad del Valle de Guatemala. We especially thank Fermín Jamangape for support in the field, and comments of two anonymous reviewers to the manuscript. The specimen was verified by Luis Canseco Márquez (Museum of Zoology “Alfonso L. Herrera”, UNAM). We thank funding by the UNAM's “Dirección General de Personal Académico” (PAPIIT IN229507) and Idea Wild for providing field equipment. OHO thanks Miguel Martínez Ramos for logistical support, Conacyt for a graduate fellowship (216024) and Posgrado en Ciencias Biológicas (UNAM). The specimen was collected under special permit to VHR: Oficio Núm/SGPA/DGVS/02132, Semarnat.