Gavialiceps taiwanensis
Creators: name: Lin, Chien-Ting
name: Ho, Hsuan-Ching
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Actinopterygii
Anguilliformes
Congridae
Gavialiceps
Gavialiceps taiwanensis

description: Gavialiceps taiwanensis (Chen & Weng, 1967)
Chlopsis taiwanensis Chen & Weng, 1967:81, fig. 61 (type locality: Tungkang (=Dong-gang), southwestern Taiwan). Gavialiceps taiwanensis (Chen & Weng, 1967): Karmovskaya, 1993:73. Smith in Randall & Lim, 2000:586. Ho et al., 2010:25. Ho & Shao, 2011:24. Ho et al., 2015a:8. Ho et al., 2015b:150.
Diagnosis. Juveniles and adults with light grayish body color, skin transparent and body white, pale grayish dorsally, white ventrally; gill chamber and gill opening black. Predorsal vertebrae 6‒9; preanal vertebrae 46‒52; preanal lateral-line pores 46‒52; total vertebrae 225+; dorsal-fin rays before origin of anal fin 65‒72.
Leptocephali with body markedly attenuate, narrow, tape-like, with long and almost filamentous tail; body depth 3.2‒4.4% TL; pectoral fin absent; body devoid of pigment, except for row of 5 to 8 large melanophores along ventral margin. Total myomeres up to 227; predorsal myomeres 8‒99; and preanal myomeres 50‒134.
Description of Stage 1 (Figs. 1A, 1B, 3A, 4A, 5A). Largest specimen examined is 150+ mm TL (n=4). Total myomeres 173+‒203+ (n=2); predorsal myomeres 66 (n=1); and preanal myomeres 108‒111 (n=2). Head small, head length 5.1‒5.9% TL. Tip of snout bluntly pointed, no trace of expansion; extending slightly beyond tip of lower jaw anteriorly. Dorsal fin origin at about middle of body, predorsal length 42.0‒51.6% TL. Position of anus variable, slightly behind midpoint of body (57.6% TL) in a 150 mm specimen and at two-thirds of body (72.7% TL) in 149 mm specimen. Eye relatively large, 15.0‒18.3% HL; snout relatively short, 40.9‒45.4% HL; end of mouth gape below middle of eye, upper-jaw length 49.3‒57.3% HL. Complete data provided in Table 1.
Description of Stage 2 (Figs. 1C, 3B, 5B). Largest specimen examined is 144 mm TL (n=7). Total myomeres 164+‒227 (n=5); predorsal myomeres 13‒99 (n=3); and preanal myomeres 58‒134 (n=4). Head small, head length 5.5‒6.0% TL. Tip of snout more pointed than those of Stage 1 but no trace of expansion, extending well beyond tip of lower jaw anteriorly. Dorsal fin originating from near nape to behind middle of body, predorsal length 52.1‒61.5% TL. Position of anus variable, well behind middle of body, preanal length 44.5‒80.8% TL. Eye moderately large, 13.3‒19.7% HL; snout slightly longer than that of Stage 1, its length 45.4‒49.9% HL; end of mouth gape below middle to posterior margin of eye, upper-jaw length 49.5‒66.9% HL. Complete data provided in Table 1.
Description of Stage 3 (Figs. 1D, 3C, 5C). Largest specimen examined is 156+ mm TL (n=25). Total myomeres 152+‒212+ (n=15); predorsal myomeres 8‒77 (n=11); and preanal myomeres 50‒123 (n=14). Head small to moderately large, head length 6.4‒8.9% TL. Tip of snout pointed with clear expansion, extending well beyond tip of lower jaw anteriorly, just behind the expansion; a concavity on each side of snout forming a neck-like structure. Tip of lower jaw less expanded than that of upper jaw and not forming neck-like structure. Dorsal fin originating from near nape to about middle of body, predorsal length 10.4‒41.4% TL. Position of anus variable, at anterior third to three-fourths of body, preanal length 30.2‒64.3% TL. Eye relatively small, 12.4‒17.2% HL; snout slightly slender, 40.0‒55.9% HL; end of mouth gape below to slightly behind posterior margin of eye, upper-jaw length 49.8‒70.1% HL. Complete data provided in Table 1.
Description of juveniles (Figs. 1E, 3D, 4B, 5D). Body very slender, trunk somewhat cylindrical, with a filamentous tail; body depth 1.2‒2.7% TL. Head slightly shorter, head length 10.0% TL. Dorsal origin above or slightly behind gill opening. No pectoral fin. Anus at anterior two-fifths of the fish, preanal length 41.1% TL. Both jaws markedly slender with a rounded expansion at anterior tip; end of mouth gape well behind posterior margin of eye. Those large melanophores along ventral margin faded or absent; melanophores present along upper margin of vertebrae and dorsal surface of head; dorsal surface of body covered with tiny chromatophores; body less transparent. Complete data provided in Table 2.
Description of adults (Figs. 2A, 2B, 3E, 4C, 5E). Total vertebrae 201+‒225+ (n=9); predorsal vertebrae 6‒9; and preanal vertebrae 47‒52; predorsal lateral-line pores 5‒7; preanal lateral-line pores 46‒52; dorsal-fin rays before vertical through origin of anal fin 6 5‒72. Head small and slender, head length 8.2‒11.3% TL. Snout more slender than juveniles. Dorsal-fin origin above gill opening, predorsal length 8.3‒11.4% TL. No pectoral fin. Anus at anterior third to before middle of the fish, preanal length 30.3‒43.0% TL. Dorsal surface of head and body deep grayish; both upper and lower margins of vertebrae covered by dense melanophores; black color in gill chamber and surfaces of gut become obvious and can be observed in the semi-transparent body. Largest specimen with complete tail examined is 696 mm TL. Complete data provided in Table 2.
description: Published as part of Lin, Chien-Ting & Ho, Hsuan-Ching, 2018, Morphological and molecular identification of leptocephali of Taiwanese duckbill conger, Gavialiceps taiwanensis (Chen & Weng, 1967) (Family Congridae), pp. 215-227 in Zootaxa 4454 (1) on pages 217-220, DOI: 10.11646/zootaxa.4454.1.17, http://zenodo.org/record/1446655