Chlopsis nanhaiensis Tighe, Ho, Pogonoski & Hibino

Tighe, Kenneth A., Pogonoski, John J., Hibino, Yusuke, Ho, Hsuan-Ching & Nguyen, Quan Van, 2015, Three new species of the genus Chlopsis (Anguilliformes: Chlopsidae) from the Indo-Pacific, Zootaxa 4060 (1), pp. 19-29 : 22-25

Chlopsis nanhaiensis Tighe, Ho, Pogonoski & Hibino , sp. nov.

Figs. 4 , 5 , 6 , 7

Holotype: USNM 408189 (228 mm total length); Dong-gang fish market, Pingtung, Taiwan, collected by D. G. Smith, Nov 2009.

Paratype: NMMB-P 22369 (270+ mm total length); Dong-gang fish market, Pingtung, Taiwan, collected by H. Ho, 26 Apr 2015.

Diagnosis. Distinguished from all other members of the genus Chlopsis by the combination of the following characters: pigmentation bicolored, dorsal origin approximately one eye-diameter behind gill opening, and low vertebral number (120 and 118+ in only known specimens).

Description. Total vertebrae 120 (118+, incomplete, tail regenerated), predorsal vertebrae 12 (11), preanal vertebrae 35 (33), precaudal vertebrae 54 (52), dorsal rays 353 (incomplete), anal rays 316 (incomplete), dorsal rays anterior to anal-fin origin 67 (78). Proportions as percent of total length: predorsal length 14.5 (incomplete), preanal length 33.8 (incomplete), head length 12.3 (incomplete), depth at anus 3.3 (incomplete). Proportions as percent of head length: eye diameter 10.7 (9.1), interorbital width 16.1 (15.2), snout length 16.8 (20.6), tip of snout to rictus 32.1 (30.6), tip of lower jaw to rictus 28.6 (27.9).

Body moderately elongate, slightly compressed, body depth nearly constant, gradually tapering over last 20% of total length to tip of tail ( Fig. 4 ). Dorsal-fin origin slightly more than one eye diameter posterior to gill opening ( Fig. 5 ). Head moderate in length, relatively deep. Snout relatively broad. Gape short, rictus at posterior margin of eye. Anterior nostril tubular, slightly behind tip of snout, directed anterolaterally. Posterior nostril a posteroventrally directed low tubular opening (covered by a flap) on lip in front of eye.

Lateral line on body absent except for one pore in branchial region, dorsal and anterior to gill opening ( Fig. 5 ). Supraorbital pores three: first (ethmoidal) at anteroventral tip of snout, second anteromedial to base of anterior nostril, and last above and slightly behind anterior nostril. Infraorbital pores four: first just behind anterior nostril, second midway between anterior and posterior nostrils, third just behind and slightly below posterior nostril, and last below middle of eye. Preoperculomandibular pores five, first near tip of lower jaw and last just behind middle of eye, anterior to rictus.

Maxillary teeth ( Fig. 6 ) conical, slightly recurved, in 2 irregular rows, increasing in size from outer to inner, a total of 22 teeth in inner row. Mandibular teeth like those of maxilla, in 2 rows with 21–22 teeth in the slightly enlarged, inner row; 8–9 of the anterior teeth enlarged compared to the rest of the mandibular teeth posteriorly. Intermaxillary teeth conical, slightly recurved, with approximately 18 teeth in patch; 9 small teeth around outside of patch and 9 enlarged teeth arranged in 3 rows of 3 teeth arranged longitudinally in center of intermaxillary tooth patch. Vomerine dentition shorter and stouter, slightly compressed, in two longitudinal series of 12–14 teeth anteriorly and reduced to a single median row of 5 teeth posteriorly. Description of teeth based on holotype, but dentition of paratype very similar.

Color of body dark grayish brown above and distinctly lighter ventrally; ventral light area starts on snout, in front of unpigmented anterior nostril and continuing back above posterior nostril to anterior margin of eye; tip of lower jaw also pigmented ( Fig. 5 ); posterior to eye, dorsal edge of ventral light area becomes more irregular, but extends dorsally to gill opening; ventral light area then tapers to base of anal fin slightly behind anus, but continues along base of anal fin for approximately 2/3 of body length; anal fin remains unpigmented to near tip of tail; ventral base of caudal fin and posterior portion of anal fin base much darker than rest of body.

Etymology. The name nanhaiensis is from Nan Hai, the Chinese name for the South China Sea where the holotype apparently was captured by commercial fishermen, and the Latin adjective ensis, meaning “originating in.”

Distribution. Known from the holotype and paratype ( Fig. 7 ) collected by fishermen off the southwest coast of Taiwan; presumably more widespread in the South China Sea.

Chlopsis nanhaiensis is similar in overall appearance to several other members of the genus Chlopsis . Chlopsis apterus , C. bicollaris and C. kazuko , all from the eastern Pacific Ocean, are all also bicolored, as is C. bicolor from the Atlantic Ocean, C. bidentatus from the southwestern Pacific Ocean, and C. orientalis (described herein). The posterior origin of the dorsal fin (at least one eye diameter behind the gill opening) separates C. nanhaiensis from C. bicollaris and C. kazuko . Chlopsis apterus , C. bicolor , C. bidentatus and C. orientalis , which also have the dorsal origin behind the gill opening, have more vertebrae (120 in C. nanhaiensis versus 134–140 in C. apterus , 127–134 in C. bicolor , 125–128 in C. bidentatus and 135 in C. orientalis ). All other species in the genus Chlopsis can be distinguished from C. nanhaiensis by coloration. Chlopsis sagmacollaris also has bicolor pigmentation, but is much lighter in overall coloration and has the distinctive, darker pigment patch on the nape of the neck. Chlopsis olokun , from the eastern Atlantic, is a fairly uniform tan or gray color, while C. dentatus (from the Atlantic and Indian Oceans) and C. slusserorum (from the southwestern Pacific) have banded, blotched or mottled coloration.

Figures

FIGURE 4. Holotype of Chlopsis nanhaiensis, USNM 408189, 228 mm TL; Dong-gang fish market, Pingtung, Taiwan.

FIGURE 5. Head of holotype of Chlopsis nanhaiensis, USNM 408189.

FIGURE 6. Upper (A) and lower (B) jaws of holotype of Chlopsis nanhaiensis, USNM 408189.

FIGURE 7. Paratype of Chlopsis nanhaiensis, NMMB-P 22369, 270 + mm TL; Dong-gang fish market, Pingtung, Taiwan.