Description
Ichthyophis nguyenorum is a fossorial, moderately sized caecilian described by a female holotype and two female paratypes, ranging from 256.5 - 306.5 mm in total length. The body itself is sub-cylindrical, slightly depressed dorsoventrally and tapers posteriorly. The ratio of total length to body width at middle is 21.7 - 24. 9. The head is slightly widened around the angle of the jaw and narrows anteriorly. Dorsally and laterally, the nostrils are close to the anterior margin of the mouth. Furthermore, there is a rounded snout anterior to the tentacles, slightly longer than the lower jaw. The slightly protruding eyes that are nearly midway between the top of the head and edge of the mouth laterally and slightly inset from the edge of the head dorsally. The interorbital distance is smaller than intertentacle distance and much larger than internarial distance. The tentacle-nostril distance is roughly 1.8 times the eye-nostril distance and a little larger than eye-jaw angle distance; the eye-jaw angle distance is larger than eye-tentacle distance. The tentacles themselves are very close to the edge of the mouth; in life, the tentacles are long and thin, while in preservation, their tips slightly protrude from the tentacular sheath. Regarding dentition, the number of premaxillary-maxillopalatine teeth for I. nguyenorum is 27 - 37, the vomeropalatine teeth is 23 - 28, the dentary teeth is 24 -28, and the splenial teeth is 21 - 25 (Nishikawa et al. 2012a).

Past the occiput, there is a collar region consisting of three nuchal collars, with the second being longer than the first. From a dorsal and ventral view, the collar region is wider than the head and the anterior body dorsally, while from a lateral view, the collar is not higher than the head and anterior body laterally. The first collar groove is a visible constriction that curves slightly anteriorly to the dorsal midline, separating head and trunk and becoming incomplete with separated tips at the dorsal midline. The second collar groove is visible ventrally but not dorsally, parallel to the first groove laterally and fading near the lateral stripe’s upper margin; there are two dorsal transverse grooves on the second collar as well. The third collar groove is dorsally complete and curves slightly anteriorly to the dorsal midline, with separated tips midventrally; this groove is hard to differentiate from the anterior annular grooves of the trunk and the second collar’s dorsal transverse grooves, but can be recognized as the first groove that crosses laterally to the ventral body. Following the first collar, there are 312 - 318 annuli, four of which are in the caudal region. These rings are dorsally complete but narrowly separate ventrally, except for one-tenth of the body posteriorly. On one-fourth of the body anteriorly, the annuli curve slightly anteriorly towards the midline, while on three-fourths of the posterior body, the annuli are nearly straight; ventrally, the rings distinctly angle posteriorly at the midline, their degree of curvature decreasing posteriorly until they are straight at around one-tenth of the body. On the posterior nine-tenths of the body (roughly the anterior most 10th to 15th annuli to the end of the body), the number of scale rows tend to increase up to three rows in posterior annuli. A longitudinal vent, surrounded by a subcircular and small disc, with no papillae, can be seen on I. nguyenorum, with six denticulations on each side of the vent and one small denticulation on the vent’s posterior end. There are four annuli in each vent slit, including denticulations, and in the tail. The tail itself is shorter than wide and blunt (Nishikawa et al. 2012a).

A variety of morphological characteristics differentiate I. nguyenorum from other striped Ichthyophis species. Regarding Indochinese Ichthyophis species, I. nguyenorum is differentiated from I. bannanicus by its smaller number of total annuli and complete lateral stripe (where I. bannanicus has more than 340 total annuli and a lateral stripe broken posteriorly) and from both I. kohtaoensis and I. supachaii by its robust body and wider lateral stripe (where I. kohtaoensis and I. supachaii have slender bodies and narrow lateral stripes). Regarding non-Indochinese Ichthyophis species, a smaller number of post-vent annuli and a thick, blunt tail differentiate I. nguyenorum from I. alfredi and I. daribokensis, which respectively have 5 - 7 post-vent annuli and 4 - 7 post-vent annuli, in addition to a narrow pointed tail in both species. A larger number of annuli further differentiate I. nguyenorum from I. alfredi, which has less than 300 annuli. A smaller number of post-vent annuli, in addition to a normal head, also separate I. nguyenorum from I. nokrekensis, which and 5 -7 post-vent annuli and a dorsally concave head. Furthermore, a larger number of total annuli differentiate I. nguyenorum from I. atricollaris, I. garoensis, and I. kodaguensis, which each respectively have 263 - 310 total annuli, less than 290 annuli, and less than 310 annuli. Ichthyophis atricollaris also has interrupted lateral stripes in their collars and fewer splenial teeth, I. garoensis has a body length less than 220 mm and a narrow, pointed tail, and I. kodaguensis has up to six scale rows, all unlike I. nguyenorum, which has complete lateral stripes in the collar, more splenial teeth, a body length of at least 256 mm, and up to three scale rows. Conversely, I. glutinosus and I. longicephalus have a larger number total of annuli (more than 340 annuli and nearly 350 annuli respectively) than I. nguyenorum. Ichthyophis longicephalus also has a smaller body (less than 200 mm in length) than I. nguyenorum. Complete lateral stripes in the collar and larger number of splenial teeth also differentiate I. nguyenorum from I. biangularis, which has complete lateral stripes and four splenial teeth. Having a tentacle close to the eye and smaller number of splenial teeth separate I. nguyenorum from I. beddomei, where I. beddomei has a tentacle farther from the eye and 35 - 44 splenial teeth. Additionally, a tentacle less than twice as close to the eye than nare separates I. nguyenorum from I. bernisi, I. elongatus, I. hypocyaneus, I. paucisulcus, and I. pseudangularis, which have a tentacle nearly or more than twice as close to the eye than nare. Lacking mustache-like stripes between the tentacles and nostrils also differentiates I. nguyenorum from I. khumhzi, I. moustakius, and I. sendenyu, which distinctly feature such stripes. Lastly, lacking a midventral stripe distinguishes I. nguyenorum from I. tricolor, which has a whitish midventral stripe (Nishikawa et al. 2012a).

In life, I. nguyenorum has a uniform slate ground color dorsally and pale lilac ventrally. A bright yellow, broad, and uninterrupted lateral stripe, which is mostly uniform in width between specimens, runs from just behind the upper jaw’s tentacle and lower jaw’s anterior one-fourth to the vent disc’s posterior end. A narrow whitish ring surrounds the eyes. The tentacle, its surrounding tentacle aperture, and the small, subcircular disk around the vent are whitish as well. In preservation, the colors in life diminish (Nishikawa et al. 2012a).

Aside from total length and total annuli, there may be variation in coloration in I. nguyenorum. One paratype of I. nguyenorum is described with a cream yellowish spot at the tail’s end (Nishikawa et al. 2012a).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Viet Nam

View distribution map in BerkeleyMapper.

Ichthyophis nguyenorum is endemic to certain localities of southern and central Vietnam, the latter of which has an elevational range of 135 - 1200 m (Nishikawa et al. 2012a; IUCN 2017; Poyarkov et al. 2021). In southern Vietnam, Chứng and Nghiệp (2014) report I. nguyenorum in the province of Đồng Tháp. In central Vietnam, within the Annamite (Trường Sơn) Range, I. nguyenorum can be found in Măng Cành and Tê Xăng of the Kon Tum province (Gower et al. 2002; Geissler et al. 2015; Poyarkov et al. 2021). In Măng Cành, I. nguyenorum can be found on the floors of tropical evergreen forests, with heavy rain lasting between 19:00 and 24:00 (Nishikawa et al. 2012a; IUCN 2017)

Life History, Abundance, Activity, and Special Behaviors
Ichthyophis nguyenorum can be found under rotten logs, within leaf litters, and along stream beds (during the day and night) (Geissler et al. 2015). The species was also caught by Geissler et al. (2015) in drift fence traps.

Nishikawa et al. (2012a) found the ovary of one paratype to contain ova with a maximum diameter of 3.5 mm.

Similar to other Ichthyophis, I. nguyenorum is presumably oviparous, depositing their eggs in burrows or chambers under loam or sandy soil nearby water. The mothers stay with their eggs until they hatch (Vitt and Caldwell 2013).

Larva
Ichthyophis nguyenorum larvae are gilled, exiting their burrows and crawling to a nearby body of water overland (Vitt and Caldwell 2013).

Trends and Threats
The Central Highlands of Vietnam face deforestation due to conversion to farmland for perennial crops such as coffee, tea, and rubber (Meyfroidt et al. 2013; IUCN 2017). Nishikawa et al. (2012a) found the Kon Tum Caecilian in a secondary forest nearby farmland. However, Gower and Wilkinson (2005) describe how certain caecilian species may not be negatively impacted by anthropogenic habitat changes, such as in cases of farmlands reducing soil erosion and maintaining favorable levels of shade and moisture. Therefore, research is necessary to determine if forest loss affects I. nguyenorum (IUCN 2017)

The species can be found in the Cat Tien National Park and in the Tram Chim National Park (Chứng and Nghiệp 2014; IUCN 2017).

Relation to Humans
Ichthyophis nguyenorum may be eaten by the locals of the Đồng Tháp province (Chứng and Nghiệp 2014).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Intensified agriculture or grazing

Comments
Gower et al. (2002) found I. nguyenorum to be a sister species to I. bannanicus via analyses of mitochondrial sequences cytochrome b and 12S - 16S rRNA genes using maximum-likelihood and maximum parsimony. Analyses by Nishikawa et al. (2012b) strongly supported this position through Bayesian, maximum likelihood, and maximum parsimony methods on mitochondrial sequences of the complete cytochrome b (1137 - 1140 base pairs) and 12S - 16S rRNA (2553 - 2577 base pairs) genes. Nishikawa et al. (2012a) analyzed the same genes (cytochrome b and 12S - 16S rRNA) to strongly support the hetero-specificity of I. nguyenorum and I. bannanicus. However, in 2015, Geissler et al. analyzed two mitochondrial fragments (a 660 base pairs COI fragment and a 1296 base pairs fragment with the complete cytochrome b gene) via Bayesian analysis, maximum likelihood, and maximum parsimony, to conclude that I. nguyenorum is likely sister to a new species they described, I. cardamomensis, with a high support for the monophyly of this group. The next most closely related clade includes northern and southern I. bannanicus and an undescribed species, but, there is low support for the relationship between I. bannanicus, and the clade composed of I. cardamomensis and I. nguyenorum.

The translation of the Vietnamese common name, “ếch giun”, is worm frog (Chứng and Nghiệp 2014).

The presence of a lateral stripe is an ancestral state in Ichthyophis (Nishikawa et al. 2012b).

Ichthyophis nguyenorum has limited dispersal due to their subterranean lifestyle and inability to cross major salt-water barriers (Gower et al. 2002).

References
Chứng, N. Đ., and Nghiệp, H. T. (2014). Hiện trạng nguồn tài nguyên lưỡng cư, bò sát ở vườn Quốc gia Tràm Chim Huyện Tam Nông, Tỉnh Đồng Tháp. Hue University Journal of Science (HU JOS), 91(3). [link]

Geissler, P., Poyarkov, N. A., Grismer, L., Nguyen, T. Q., An, H. T., Neang, T., Kupfer, A., Ziegler, T., Böhme, W., and Müller, H. (2015). New Ichthyophis species from Indochina (Gymnophiona, Ichthyophiidae): 1. The unstriped forms with descriptions of three new species and the redescriptions of I. acuminatus Taylor, 1960, I. youngorum Taylor, 1960 and I. laosensis Taylor, 1969. Organisms Diversity & Evolution, 15, 143-174. [link]

Gower, D. J., Kupfer, A., Oommen, O. V., Himstedt, W., Nussbaum, R. A., Loader, S. P., Presswell, B., Müller, H., Krishna, S.B., Boistel, R., and Wilkinson, M. (2002). A molecular phylogeny of ichthyophiid caecilians (Amphibia: Gymnophiona: Ichthyophiidae): out of India or out of South East Asia? Proceedings of the Royal Society of London. Series B: Biological Sciences, 269(1500), 1563-1569. [link]

Gower, D. J., and Wilkinson, M. (2005). Conservation biology of caecilian amphibians. Conservation biology, 19(1), 45-55. [link]

IUCN SSC Amphibian Specialist Group. (2017). Ichthyophis nguyenorum. The IUCN Red List of Threatened Species 2017: e.T43340087A113955436. https://dx.doi.org/10.2305/IUCN.UK.2017-2.RLTS.T43340087A113955436.en. Accessed on 18 May 2023.

Meyfroidt, P., Vu, T. P., and Hoang, V. A. (2013). Trajectories of deforestation, coffee expansion and displacement of shifting cultivation in the Central Highlands of Vietnam. Global Environmental Change, 23(5), 1187-1198. [link]

Nishikawa, K., Matsui, M., and Orlov, N. L. (2012a). A new striped Ichthyophis (Amphibia: Gymnophiona: Ichthyophiidae) from Kon Tum Plateau, Vietnam. Current Herpetology, 31(1), 28-37. [link]

Nishikawa, K., Matsui, M., Yong, H. S., Ahmad, N., Yambun, P., Belabut, D. M., Sudin, A., Hamidy, A., Orlov, N.L., Ota, H., Yoshikawa, N., Tominaga, A., and Shimada, T. (2012b). Molecular phylogeny and biogeography of caecilians from Southeast Asia (Amphibia, Gymnophiona, Ichthyophiidae), with special reference to high cryptic species diversity in Sundaland. Molecular Phylogenetics and Evolution, 63(3), 714-723. [link]

Poyarkov, N. A., Van Nguyen, T., Popov, E. S., Geissler, P., Pawangkhanant, P., Neang, T., Suwannapoom, C., and Orlov, N. L. (2021). Recent progress in taxonomic studies, biogeographic analysis, and revised checklist of amphibians in Indochina. Russian Journal of Herpetology, 28(3A), 1-110. [link]

Vitt, L. J., and Caldwell, J. P. (2013). Herpetology: an introductory biology of amphibians and reptiles. Academic press. [link]

Species Account Citation: AmphibiaWeb 2024 Ichthyophis nguyenorum: Kon Tum Caecilian (English); Ếch giun nguyễn (Vietnamese); Nguyens’ Caecilia (English) <https://amphibiaweb.org/species/7871> University of California, Berkeley, CA, USA. Accessed Dec 26, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 26 Dec 2024.

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