Lepidocephalus nanensis, Deein & Tangjitjaroen & Page, 2014

Deein, Gridsada, Tangjitjaroen, Weerapongse & Page, Lawrence M., 2014, A revision of the spirit loaches, genus Lepidocephalus (Cypriniformes, Cobitidae), Zootaxa 3779 (3), pp. 341-352 : 344-347

Lepidocephalus nanensis , n. sp.

Thai Spirit Loach

( Fig. 1A )

Holotype. NIFI 4388 , 72.0 mm SL; Thailand, Phitsanulok Prov., Khlong Chompu, Mae Nam Nan, Chao Phraya basin, Nov. 2008, G. Deein.

Paratypes. NIFI 3787 , 79.3 mm SL; Thailand, Phitsanulok Prov., Nern Ma Prang District, Mae Nam Nan drainage, Chao Phraya basin, Nov. 2008 ; NIFI 4856 (6, 69.9–76.1), Phitsanulok Province, Bang Rakam District, Mae Nam Nan, 16.76N, 100.11E, 9 Feb. 2011 ; NIFI 4857 (6, 68.4–80.1), boundary of Sukhothai Province, Kongkrairat District with Phitsanulok Province, Prompiram and Bang Rakam districts, Mae Nam Nan, 16.76N, 100.11E, 18 Aug. 2010 ; NIFI 4858 (4, 56.4–67.6) Nakon Sawan Province, Chum Sang District, Borraped Lake , 15.71N, 100.27E, 11 Oct. 2010 ; UF 186928 (5, 68.2–75.0), Phitsanulok Province, Prompiram District, Mae Nam Nan near Naraesuan Dam , 17.04N, 100.20E, 23 Apr. 2009 ; UF 186929 (2, 65.5–72.7), Phichit Province, Sam Ngam District, Mae Nam Nan, 16.50N, 100.20E, 4 Oct. 2011 ; UF 186930 (2, 65.2–70.0), Nakon Sawan Province, Krok Pra District, Chao Phraya River , below confluence of Nan and Yom rivers, 15.55N, 100.08E, 15 Jun. 2009 .

Diagnosis. A species of Lepidocephalus that is readily distinguishable ( Fig. 1 , Table 1 ) from L. spectrum by the presence of eyes and dark pigment on the body, and absence of tubules along the lateral line and large papillae on the lips; from L. pahangensis by the presence of scales on top of the head and absence of large papillae on the lips ( Figs. 3A , 4A ); from L. pallens by having the dorsal-fin origin well behind (vs. over) the pelvic–fin origin (predorsal length 68.1–71.3 vs. 59.9% SL); and from L. macrochir by having a longer snout (5.6–7.4 vs. 3.9–5.1% SL; 28.6–38.1 vs. 23.3–27.1% HL).

Description. Body deep, slab-sided; greatest depth 14.7–21.2% SL. Head narrow, length 16.9–22.2% SL. Eye small, in dorsal half of head in shallow depression above bifid suborbital spine. Origin of dorsal fin behind origin of pelvic fin. No or small axillary lobe on pelvic fin; absent on holotype. Fleshy lobe at origin of pectoral fin.

Scales on top of head, cheek and opercle; body completely covered with minute, often deeply embedded scales. Lateral line complete, 185–205 scales; 0–2 pores on caudal fin; no tubules on lateral line.

Mouth horseshoe-shaped; upper lip smooth on ventral surface, with small papilla on anterior and posterior margins, without median indentation; lower lip plicated, with median indentation on lower edge ( Figs. 3A , 4A ). Two pairs of rostral barbels; inner pair reaching to corner of mouth, outer pair slightly longer and reaching slightly past corner of mouth; one pair of maxillary barbels, reaching approximately to vertical at posterior end of groove containing suborbital spine. Large flap on anterior nostril. Dorsal rays iii,8; pectoral rays 9–11; pelvic rays 6–8; anal rays ii,5–6; upper branched caudal rays 7; lower branched caudal rays 7.

Cephalic lateralis system: lateral canal with 1 pore, extends anteriorly from lateral line; suborbital canal extends along lower margin of groove holding suborbital spine with 4 pores, abruptly turns anteroventrally with 4 more pores, ends on side of snout well in front of nostrils; no supraorbital canal at surface. Supratemporal canal branches off lateral canal, then ends or continues under skin without pores at surface. Preoperculomandibular pores not visible.

Pectoral fin falcate in both sexes; second ray longer in both sexes than other pectoral-fin rays. Pectoral fin much longer in some individuals than others (12.2–18.9% SL); extent and significance of inter- and intra-variation, including sexual and ontogenetic variation, is unknown. Second ray of pectoral fin much thicker (forming lamina circularis) in adult male than in female, but not longer. Pectoral fins of male L. nanensis (N = 4) averaged 15.1% SL; those of females (N = 7) averaged 15.5% SL. The thicked ray presumably has a function related to spawning behavior. Pelvic fins are short, 6–8% SL.

Coloration in life. Body dusky pink-brown; darker gray-brown along mid-dorsum and along mid-side posteriorly ( Fig. 5 ). Distinctive yellow snout followed by blue-black bar before eye; head dusky yellow behind eye. Cheek and opercle with silver-blue iridescence. Dorsal fin with concentration of melanophores at base, creating dark basal band - deepest anteriorly; melanophores outlining lower halves of fin rays. Other fins clear except for melanophores along rays.

Etymology. The name nanensis , an adjective, refers to the river system where most specimens have been collected.

Distribution. Lepidocephalus nanensis is found in Thailand in the Nan River and in the Chao-Phraya River below the confluence of the Nan and Yom rivers ( Fig. 2 ). To our knowledge, Šlechtová et al. (2008) first recorded this species from Thailand (as L. macrochir ) and included molecular data from specimens collected at a fishpond at Nakom Savan (Nakon Sawan, Nakon Sawan Province), Thailand. Recent collections suggest that this species is common in the Nan and lower Chao Phraya rivers. These large rivers seem to be the preferred habitat of the species.

Figures

FIGURE 1. Species of Lepidocephalus. (A) L. nanensis, holotype, NIFI 4388, 72.0 mm SL, Nan River, Thailand; (B) L. macrochir, syntype, BMNH 1866.5.2.55, 77.7 mm SL, Sumatra or Java; (C) L. pallens, holotype, RMNH 7783, 41.9 mm SL; (D) L. pahangensis, holotype, ZRC 490, 35.8 mm SL; (E) L. spectrum, paratype, USNM 230267, 49.2 mm SL, Kalimantan. Photos A, C, D and E by Z. Randall; B by M. Sabaj Perez.

FIGURE 2. Distribution of specimens of Lepidocephalus examined.

FIGURE 3. Mouths of Lepidocephalus. (A) L. nanensis, holotype, NIFI 4388, 72.0 mm SL, Nan River, Thailand; (B) L. pahangensis, holotype, ZRC 490, 35.8 mm SL; (C) L. spectrum, paratype, USNM 230267, 49.2 mm SL, Kalimantan. Photos by Z. Randall.

FIGURE 4. Mouths of specimens of Lepidocephalus shown in Figure 3. (A) L. nanensis, (B) L. spectrum. Although the lower lip of L. nanensis is folded more posteriorly than that of L. spectrum, it and the upper lip lack the large papillae shown on the lips of L. spectrum. Drawings by D. Lumbantobing.

FIGURE 5. Lepidocephalus nanensis in an aquarium. Collected at Naraesuan Dam on Mae Nam Nan, Prompiram District, Phitsanulok Province, Thailand, June 2005 (not vouchered). Photo by N. Panitvong.