Sunday, May 19, 2019

[Herpetology • 2019] Limnonectes savan • A New Caruncle-bearing Fanged Frog (Limnonectes, Dicroglossidae) from Laos and Thailand

 Limnonectes savan 

 Phimmachak, Richards, Sivongxay, Seateun, Chuaynkern, Makchai, Som & Stuart, 2019
กบพนมดงรัก || DOI: 10.3897/zookeys.846.33200 

A new species of the dicroglossid frog genus Limnonectes is described from recent and historical museum specimens collected in central and southern Laos and northeastern Thailand. Limnonectes savan sp. nov. has males that bear a caruncle on top of the head, and most closely resembles L. dabanus from adjacent southern Vietnam and eastern Cambodia. However, the new species is readily distinguished from L. dabanus, and all other caruncle-bearing species of Limnonectes in mainland Southeast Asia, by its adult and larval morphology, mitochondrial DNA, and advertisement call. Its description brings the total number of caruncle-bearing species of Limnonectes to six.

Keywords: Amphibia, bioacoustics, larval morphology, Limnonectes dabanus, mitochondrial DNA, Southeast Asia

Figure 3.  Limnonectes savan sp. nov. in life A lateral view of holotype male (NCSM 76288) B lateral view of paratype female (NUOL 00061) C ventral view immediately prior to preservation of paratype male (NCSM 76303) D ventral view immediately prior to preservation of paratype female (NCSM 76301).

Figure 5.  Limnonectes savan sp. nov. A oviposition site with dead palm frond in situ in Savannakhet Province, Laos B eggs (NCSM 76494) prior to preservation adhered to underside of dead palm frond that is visible in previous image C eggs (NCSM 76494) in preservative with jelly layer D eggs (NCSM 76494) in preservative after removal from jelly layer.  

Figure 6.  Limnonectes savan sp. nov. larvae A in situ in puddle in wet gully in semi-evergreen forest in Savannakhet Province, Laos; one exemplar larva in preservative (NCSM 76492) at Gosner Stage 31, TL 18.4 mm in B oral view C dorsal view D lateral view and E ventral view.

Limnonectes (Elachyglossa) savan sp. nov.
Limnonectes sp. Chan-ard, 2003: 120.

Diagnosis: Assigned to the genus Limnonectes on the basis of its inferred phylogenetic position (Fig. 1), the presence of fang-like odontoid processes on the lower jaw (Emerson et al. 2000; Lambertz et al. 2014), and having males with hypertrophied heads (Lambertz et al. 2014). Assigned to the subgenus Elachyglossa (following Ohler and Dubois 1999; Lambertz et al. 2014) on the basis of its close phylogenetic position to the subgenerotype L. gyldenstolpei (Fig. 1). A medium-sized Limnonectes having the combination of adult males with SVL 39.0–56.2, adult females with SVL 38.9–55.2; males with hypertrophied head; males with interorbital caruncle consisting of low-profile swelling without a free posterior margin, extending from level of anterior margin of eye to level midway between posterior margin of eye and tympanum; odontoid processes on anterior margin of lower jaw larger in males than in females; horizontal diameter of tympanum equal to eye in adult males, ¾ of eye diameter in subadult males, immature males, and females; enlarged, rounded, tubercles on dorsum, becoming more elongated dorsolaterally; dark brown or gray spotting on throat, belly, and ventral surfaces of forelimbs and hindlimbs; and ova with pigmented poles.

Etymology: The specific epithet savan means paradise in the Lao language, and is a commonly used, truncated form of the name for Savannakhet Province, Laos, that contains the holotype and most paratype localities of the new species. The specific epithet savan is a noun in apposition.

Suggested common names: Savan Fanged Frog (English), Kop Hone Savan (Lao), Kop Panomdongrak (Thai).

Figure 8. Habitat of Limnonectes savan sp. nov. in Savannakhet Province, Vilabouli District, Laos in December 2008 at A Houay Khalai Stream, Ban Khalai Village, and B Houay Hong Stream, Ban Houay Hong Village.

Distribution, natural history: 
Limnonectes savan is known to occur in central and southern Laos (Khammouan, Savannakhet, and Champasak Provinces), and northeastern Thailand (Ubon Ratchatani; Fig. 7). Chan-ard (2003) also reported it (as Limnonectes sp.) from Amnat Charoen Provinces in northeastern Thailand. The species occurs in hill and semi-evergreen forest from 254–790 m elevation, and is usually associated with small (1–3 m wide) streams (Fig. 8); based on 51 specimens sampled at night (1900h–2251h), 38 (74.5%) were found in streams (permanent streams with rocky or sandy substrates, or intermittent streams), nine (17.7%) were found in puddles, two (3.9%) were found in ponds, and two (3.9%) were found on the forest floor, away from an obvious body of water. Nineteen (37.3%) of the 51 specimens were sampled in water, with the remaining 32 individuals (62.7%) found on substrates of soil, leaf litter, rocks or logs.

Limnonectes savan breeds in puddles on the forest floor during the rainy season. A chorus of calling males, including paratype male NCSM 76299, was observed in a wet gully under roots and dead leaves in semi-evergreen forest at 1935 h on 28 June 2009. Egg clutch NCSM 76494 was found adhering to the underside of a submerged dead palm frond in a puddle in the same wet gully on 1 July 2009 (Fig. 5). Larvae NCSM 76491 (n=13), NCSM 76492 (n=28), and NCSM 76493 (n=43) were sampled from small puddles (0.2–1 m diameter) in the same wet gully during 28 June–1 July 2009 (Fig. 6).

Limnonectes savan occurs in sympatry with L. lauhachindai in Ubon Ratchathani Province in northeastern Thailand (Appendix 1), but its geographic distribution appears to be parapatric to that of L. dabanus in southern Laos, and to that of L. gyldenstolpei in central and southern Laos and northeastern Thailand (Appendix 1).

 Somphouthone Phimmachak, Stephen J. Richards, Niane Sivongxay, Sengvilay Seateun, Yodchaiy Chuaynkern, Sunchai Makchai, Hannah E. Som and Bryan L. Stuart. 2019. A New Caruncle-bearing Fanged Frog (Limnonectes, Dicroglossidae) from Laos and Thailand. ZooKeys. 846: 133-156.  DOI: 10.3897/zookeys.846.33200


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