Gigantactis cheni, Ho & Shao, 2019

Ho, Hsuan-Ching & Shao, Kwang-Tsao, 2019, Two new deep-sea anglerfishes (Oneirodidae and Gigantactidae) from Taiwan with synopsis of Taiwanese ceratioids, Zootaxa 4702 (1), pp. 10-18 : 10-18

Gigantactis cheni sp. nov.

Hairy whipnose

Figs. 3 A–C

Holotype. ASIZP 62947 , female, 385 mm SL, off Daxi , Yilan, northeast Taiwan, ca. 24°50 N, 122°00 E, ca. 400– 500 m, bottom trawl, Oct. 2001, bycatch, coll. D.-M. Chen.

Paratype. ASIZP 61823 , female, 340 mm SL, May 2002 ; NMMB-P006230 , female, 325 mm SL, Nov. 8, 2007 ; both collected from near the type locality by D.-M. Chen.

Diagnosis. A member of the Gigantactis vanhoeffeni species group differing from congeners in having a single row of 8–15 unpigmented filaments present on posterior margin of basal one-third of illicium; illicial length 145.5– 172.1% SL; esca elongated, tapering into a conical shape, with numerous spinules, and darkly pigmented; distal prolongation length 10.6–12.6% SL; dentary teeth 66–70 on each side, arranged in 5 longitudinal series; dentary teeth relative long, 2.5–3.4% SL; caudal fin rays short, 25.5–30.6% SL; and caudal fin deeply forked.

Description. Dorsal-fin rays 6, anal-fin rays 6, pectoral-fin rays 17, caudal-fin rays 9. Dentary teeth 66–70 on each side, 136 (136–140) in total; premaxillary teeth 26–32 on each side; lower jaw with five series of teeth, two inner rows, one middle row, and 2 outer rows ( Fig. 3C ). Head length 19.7–21.5% SL; head depth 10.6–12.4% SL.

Body laterally compressed; caudal peduncle elongate; head short; dermal spinules present on entire body surface except lips; illicium emerging from stout tip, 15 (8–12 in paratypes) unpigmented filaments along posterior margin of basal one-third of illicial stem, 10 (5–8) on dorsal surface of head just behind the base of illicium; illicium relative long, 145.5–172.1% SL. Papilliform gland present inside of upper oral cavity.

Escal bulb tapering, with a long black-pigmented prolongation, 10.6–12.6% SL; surface spinulose except the escal pore; short filaments present on prolongation and the terminal tip.

Distribution. Gigantactis cheni is represented by the type series collected from northeastern Taiwan off Daxi at depth ca. 400– 500 m.

Etymology. Gigantactis cheni is named for Mr. Din-Moo Chen, an excellent fisherman who collected most samples for our studies, including the type series of both new species in present work.

Remarks. Gigantactis cheni sp. nov. belongs to the G. vanhoeffeni species group (Bertelson et al., 1981) and differs from all other members of this group in having a considerably longer illicium and a longer distal prolongation of the escal bulb. It is most similar to G. paxtoni Bertelsen, Pietsch & Lavenberg, 1981 which also has unpigmented filaments on illicium. However, the new species differs in having relatively more total jaws teeth (136–140, vs. 10–55), relatively short outtermost teeth (2.5–3.4%, vs. 3.4–7.1% SL); slightly shorter illicium (145.5–172.1%, vs. 168.0–198.0% SL); a relatively short escal prolongation (10.6–12.4%, vs. 12.0–28.0% SL); a relatively short caudal fin (25.5–30.6%, vs. 27.5–35.0% SL); and caudal fin deeply forked (vs. nearly truncate). Also, the filaments on the head are distributed on the posterior illicium for about one-third its length, whereas those on G. paxtoni are restricted to the basal region of illicium.

Gigantactis cheni sp. nov. is also similar to G. meadi Bertelsen, Pietsch & Lavenberg, 1981 , but differs in having a relatively long illicium (145.5–172.1%, vs. 72–96% SL), a relatively elongated esca (vs. short), caudal fin deeply forked ( Fig. 3A , vs. slightly concaved).

Figures

FIGURE 3. Gigantactis cheni sp. nov. A. Drawing of holotype, ASIZP 62947, 385 mm SL, not all cirri were shown. B. Fresh caught paratype, ASIZP 61823, 340 mm SL. C. Teeth on left side of lower jaw, from the holotype.