Laubuka tenella Kullander, Rahman, Noren & Mollah 2018

Laubuka tenella Kullander, Rahman, Norén & Mollah, 2018 Laubuka tenella Kullander, Rahman, Norén & Mollah 2018: Zookeys (742): 105–126 (Bangladesh: Chittagong Division, Cox’s Bazar District, Naf River drainage, Domdomia Stream; Chittagong Division: Bakkhali River drainage, Majerchora Stream; Myanmar: Rakhine State; Thandwe River drainage: Nan Chaung, a stream at 3 km on road from Thandwe (market) to Ngapali). Specimens examined (n=10): SEABRI 20241852, 37.5 mm SL, 1 ex., Tae Stream (16°25'11.56"N, 94°27'48.39"E), Pathein River drainage, Nga Yoke Kaung Town, collected by Xiao-Yong Chen, Nay Htet Naing, and Phyo Htet Zaw, 31 July 2024. SEABRI 20241853 –57, 35.0– 37.5 mm SL, 5 ex., Tae Stream (16°25'7.26"N, 94°27'51.60"E), Pathein River drainage, North of Nga Yoke Kaung Town, collected by Xiao-Yong Chen, Nay Htet Naing, and Phyo Htet Zaw, 3 August 2024; SEABRI 20241858 –9, 33.5–37.1 mm SL, 2 ex., Minn Stream (16°19'50.19"N, 94°24'39.81"E), South of Nga Yoke Kaung Town, collected by Xiao-Yong Chen, Nay Htet Naing, and Phyo Htet Zaw, 3 August 2024. SEABRI 20241860 –61, 38.9–42.3 mm SL, 2 ex., a stream (16°42'26.33"N, 94°32'37.42"E) on the mid way from Nga Yoke Kaung to Pathein Township, Pathein River drainage, collected by Xiao-Yong Chen, Nay Htet Naing, and Phyo Htet Zaw, 8 August 2024. Diagnosis Laubuka tenella is distinguished by the combination of the following characters: Presence of a dark stripe along middle of posterior third of side, anteriorly replaced by short vertical bars, abdomen white, body elongate, strongly compressed laterally, mouth terminal, pectoral fin long and falcate, almost reaching end of pelvic-fin rays, pelvic fin short, dorsal-fin rays ii, 8½, predorsal scales 16–18, lateral-line scales 29–32, fins hyaline. Description Measurements and counts are shown in Table 5 and Figure 8 for general appearance. Body elongate, strongly compressed laterally. Predorsal contour gradually rising, the highest point at base of dorsal-fin origin. Abdomen rounded. Eyes large, lateral, place in middle of head length. Snout short. Mouth terminal. Lower jaw with minute papillae. Tubercles absent. Barbels absent. Scales cycloid, thin, and transparent. Dorsal fin origin at anterior two-thirds of standard length, length of rays gradually decreased. Dorsal-fin rays ii.8 ½ (10). Anal-fin base longer than dorsal-fin base, posterior rays gradually shorter. Anal-fin rays iii, 16½ (2), 17½ (2), 18½ (6). Pectoral fin long, falcate, unbranched ray longest or unbranched ray and first branched ray equally long, almost reaching end of pelvic fin. Pectoral-fin rays i.10 (7) or 11 (3). Pelvic fin short, not reaching anus. Pelvic-fin rays i.6 (10). Caudal peduncle slender. Caudal fin forked. Caudal fin lobes almost subequal. Lateral line complete, with 29–32+1 scales. Predorsal scales 16 (3), 17(2), 18(5), prepelvic and preanal region scaled. Circumpeduncular scales 12(10). Distribution Based on our field collections and the historic specimens, Laubuka tenella is distributed in the Thandwe and Pathein rivers (Ayeyarwady drainage), in Rakhine State and the Ayeyarwady Region (Fig. 2). Habitat and biology The stream in which Laubuka tenella was found had an average water depth 0.9 m, with steady flow. The ground is sandy and the water is clean. Coexisting species include Mystus gulio, Pethia conchonius, Pethia stoliczkana, and Glossogobius giuris. Comparisons The interspecific variation in L. tenella is 0.00 and sequence similarity is 99.7 between Myanmar and Bangladesh samples. Based on the original description of Kullander et al. (2018), the preserved color pattern of L. tenella reported here is different from Rakhine samples, but share the same proportional measurements and counts. The published photograph (Kullander et al. 2018; fig. 1) of the type, shows 6 distinct anterior vertical bars (vs. 2 indistinct vertical bars or absent). Laubuka tenella is distinguished from Sri Lanka Laubuka species by having 16–18 predorsal scales (vs. 18–21 in L. lankensis, L. insularis, L. ruhuna, and L. hema); 29–32 lateral-line scales (vs. 33–35 in L. hema, 34–37 in L. lankensis, and 34– 36 L. insularis); a shorter pelvic-fin length, of 14.9–20.8% SL (vs. 25.4–32.0% SL in L. lankensis, L. insularis, and L. hema) and the presence of an entire, narrow lateral band on the posterior third of the body (vs. a series of blotches along the side in L. ruhuna and L. varuna). It is further distinguished from Indian Laubuka species by the presence of a dark stripe along the posterior third of the side, anteriorly replaced by short vertical bars (vs. a dark-brown midlateral stripe along the side in L. parafacsciata, L. fasciata, and L. trevori; the absence of any markings on the side of body other than the humeral and caudal-peduncle spots in L. latens), and 8½ branched dorsal-fin rays (vs. 7½ in L. trevori, L. latens, and L. fasciata). It is distinguished from L. caeruleostigmata by having a lesser body depth (23.8–29.4% SL, vs. 36.4–40.7% SL); 8½ branched dorsal-fin rays (vs. 11½–12½), and the presence of lateral band on the posterior side of the body (vs. absence). It is further distinguished from L. siamensis by having 16–18 predorsal scales (vs. 20) and the presence of a dark stripe along middle of posterior third of side, anteriorly replaced by short vertical bars in alive specimens (vs. indistinct vertical bars on the anterior side, followed by black lateral stripe ending in a triangular spot on the caudal-fin base).