Morphological and molecular identification of leptocephali of Taiwanese duckbill conger, Gavialiceps taiwanensis (Chen & Weng, 1967) (Family Congridae) Author Lin, Chien-Ting Author Ho, Hsuan-Ching text Zootaxa 2018 2018-07-31 4454 1 215 227 journal article 29280 10.11646/zootaxa.4454.1.17 500d3e41-9c20-4797-a207-a58fb08b9a4b 1175-5326 1446655 DEFC3DCA-20A5-4DDB-854E-EF1F0C858B6F 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. FIGURE 1. General appearance of G. taiwanensis . A, B. Stage 1, NMMB-P27898, 150 mm TL. C. Stage 2, NMMB-P27901, 137+ mm TL. D. Stage 3, NMMB-P27900, 144 mm TL E. Juvenile, NMMB-P27907, 72.4 mm PAL. TABLE 1. Meristics and morphometrics of three leptocephalic stages of G. taiwanensis .
Stage 1 Stage 2 Stage 3
TL (mm) 132+‒150+ (n=4) 125+‒144 (n=7) 114+‒156+ (n=25)
PAL (mm) 86.4‒108.3 (n=3) 57.2‒109.1 (n=6) 42.2‒98.2 (n=22)
TM 173+‒203+ (n=2) 164+‒227 (n=5) 152+‒212+ (n=15)
PDM 66 (n=1) 13‒99 (n=3) 8‒77 (n=11)
PAM 108‒111 (n=2) 58‒134 (n=4) 50‒123 (n=14)
% TL
HL 5.1‒5.9 5.5‒6.0 6.4‒8.9
PDL 42.0‒51.6 52.1‒61.5 10.4‒41.4
PAL 57.6‒72.7 44.5‒80.8 30.2‒64.3
TR 51.7‒67.5 39.3‒75.3 22.5‒56.3
% PAL
PDL 68.7‒72.9 35.3‒76.1 24.2‒71.8
HL 7.1‒10.3 6.8‒13.9 10.0‒27.0
UJ 3.6‒5.4 3.9‒9.3 5.0‒16.0
ED 1.2‒1.7 1.2‒2.3 1.3‒3.3
S 3.2‒4.2 3.4‒6.5 4.0‒12.8
BD 6.0‒6.7 5.1‒9.9 4.9‒14.4
TR 89.7‒92.9 86.1‒93.2 73.0‒90.0
% HL
ED 15.0‒18.3 13.3‒19.7 12.4‒17.2
S 40.9‒45.4 45.4‒49.9 40.0‒55.9
UJ 49.3‒57.3 49.5‒66.9 49.8‒70.1
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 . FIGURE 2. General appearance of G. taiwanensis . A. Adult, ASIZP 61770, 161.3 mm PAL. B. Adult, 208.1 mm PAL 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 . FIGURE 3. Lateral view of head showing jaw development of G. taiwanensis . A. Stage 1, NMMB-P27898, 150 mm TL. B. Stage 2, NMMB-P27901, 137+ mm TL. C. Stage 3, NMMB-P27900, 144 mm TL. D. Juvenile, NMMB-P27907, 72.4 mm PAL. E. Adult, ASIZP61770, 161.3 mm PAL. 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 .