Navigobius dewa, Hoese, Douglass F. & Motomura, Hiroyuki, 2009

Hoese, Douglass F. & Motomura, Hiroyuki, 2009, Descriptions of two new genera and species of ptereleotrine fishes from Australia and Japan (Teleostei: Gobioidei) with discussion of possible relationships, Zootaxa 2312, pp. 49-59 : 52-55

Navigobius dewa sp. nov.

Figures 1 and 2

Ptereleotridae , indet. gen. and sp. 2: Senou et al., 2004: 512 (Kagoshima Bay, Japan).

Holotype. AMS I.44800–001, 37.5 mm SL female from off Sakurajima, Kagoshima Bay, Kagoshima Prefecture, Japan (31°35’35”N, 130°35’25”E), 25 July 2007, Shin’ichi Dewa , 70 m (formerly KAUM I.5518).

Paratypes. KAUM-I.5516, 40.7 mm SL female, taken with holotype; KAUM-I.5517, 45.2 mm SL female taken with holotype.

Diagnosis. As for the genus.

Description. Based on 3 females. General. First dorsal fin with 6 spines (in 3); second dorsal-fin rays I,19(3). Anal-fin rays I,19(2), I,20(1, holotype). Pectoral-fin rays 20(3). Pelvic-fin rays I,4(3). Segmented caudal-fin rays 9/8(3). Branched caudal-fin rays 6/5(3); longitudinal scale count 92–97; scales imbricate, 40– 42 in transverse series; gill opening moderate, extending ventrally to just below posterior preopercular margin; gill-rakers on first arch 5+1+ 10 in one paratype, spatulate, elongate; rakers on second, third and fourth arches tuberculate with dorsal spiny projections.

Head. Snout strongly curved in lateral view, broadly rounded in dorsal view; anterior nostril at end of very short tube, 2–3 nostril diameters above upper lip, posterior nostril a larger pore just anterior to—almost touching—anterodorsal margin of eye; eyes lateral on head, eye length almost twice snout length; mouth at an angle of 27–37° to longitudinal axis of body; gill opening moderate, extending from upper part of pectoral base ventrally to just below posterior preopercular margin; tongue tip pointed; nuchal crest a low fold, extending forward to above rear end of eye.

Teeth. No teeth on vomer, tongue or palatine; jaw teeth conical; upper jaw with two rows of conical curved teeth, outer row enlarged, very widely spaced, one inner row of smaller close-set teeth; lower jaw with outer row of small close-set teeth, two enlarged curved conical teeth on each side of jaw in inner row anteriorly; other teeth in row very small, close-set.

Scales. Nape, operculum and cheek naked. Body scales largely cycloid, imbricate, naked before line from just behind pectoral-fin insertion to about fifth dorsal spine, no scales in pectoral axil, ventrally scales continuous onto sides of isthmus; a small patch of ctenoid scales on midside under pectoral fin with 3–5 ctenii, scales near posterior end of caudal peduncle ctenoid, each scale with 1–3 small ctenii; posteriorly body scales extending onto base of caudal fin, but not other fins, belly and pectoral-fin base scaled; prepelvic area with scattered scales on midline, scaled at side of isthmus.

Fins. First dorsal fin low with rounded margin, dorsal spines all short, no filamentous dorsal spines, membrane from dorsal spine 6 connecting to body just before origin of second fin; fourth and fifth spines subequal, longest (only slightly longer than third spine; when depressed sixth spine reaching to between first and second segmented dorsal ray). Second dorsal fin subequal in height to first dorsal fin, its posterior rays not prolonged, all segmented rays branched. Anal fin subequal in height to second dorsal fin, its posterior rays not prolonged, all segmented rays branched. Pectoral fin with broadly rounded posterior margin, rays all branched, except uppermost 2 and lowermost 2, fin slightly shorter than head length. Pelvic fins separate, with 1 spine and 4 segmented rays, first 3 rays with a single branch, fourth ray unbranched; third ray longest, fourth ray about 70% length of third ray; third ray reaching to a point just below posterior end of pectoral fin, below sixth dorsal spine, well short of anus. Caudal fin forked, upper lobe longer than lower, sixth segmented ray from top prolonged into a filament; fifth and seventh rays with much shorter filaments.

Head pores: 4 pores along upper and rear margin of each orbit, posterior nasal pore just above and behind posterior nostril, paired interorbital pores above middle of orbit, postorbital pore dorsoposterior to orbit, infraorbital pore posterior to upper margin of pupil, behind orbit; a terminal lateral canal pore above posterior preopercular margin; no preopercular pores.

Head papillae: head papillae a transverse pattern, with few papillae in each row. Papillae shown in Figure 2 (n.b., the drawing may be incomplete with papillae hard to discern).

Coloration of freshly collected holotype: Head and body largely a translucent orange. A dull yellowish stripe (depth slightly less than pupil diameter) extending forward from eye; a similarly colored stripe extending from dorsal margin of eye posteriorly to below first dorsal fin origin; upper lip light brown posteriorly; operculum and pectoral-fin base an iridescent blue; belly silvery; dorsal fins with two broad yellow stripes (more intense on membranes between spines and rays); below lowermost yellow stripe a thin purple stripe; a similar purple stripe between yellow stripes; distal margin of fins with purple stripe, followed ventrally by a very thin white stripe; anal fin with very thin proximal light purple stripe, followed ventrally by a broad yellow stripe (not narrowing between rays), followed ventrally by a broad purple stripe, followed ventrally by a broad yellow stripe, with thin brown margins; thin purple stripe at distal margin of fin; pectoral and pelvic fins translucent; pelvic fin with tinge of purple on outer quarter; upper lobe of caudal fin with a yellowish-orange stripe along upper margin, followed by a broad purple stripe, then a yellowish-orange stripe; central portion of caudal fin translucent, becoming pale purple ventrally, lower lobe with a yellow stripe, with purple stripe along lower margin of fin.

Coloration in alcohol: Head and body uniformly light brown; fins clear; scattered melanophores posteriorly on body; a short curved pale black bar on base of caudal fin.

Etymology. The species is named for the collector of the type material, Mr. Shin’ichi Dewa ; it is treated as a noun in apposition.

Distribution. Currently known only from southern Japan: Kagoshima Bay (type locality) and off Amamioshima Island, the Ryukyu Islands (underwater observation by Mr. S. Dewa ).

Remarks. Mr. Dewa observed the species in Kagoshima Bay at depths of 45–65 m from June to October (summer and autumn) and at 75–85 m from November to May (winter and spring). The species is epibenthic on sandy and muddy bottoms on the steep slope.

The adult fish forms epibenthic schools, comprising 10–300 individuals in Kagoshima Bay, where Mr. Dewa has recognized at least 15 adult schools. From late October to late November, approximately 20 mm TL juveniles were found in schools of about 10 individuals.

In May 2007, Mr Dewa found about 30 individuals of the species at a depth of 60 m at the outer edge of a reef off Amami-oshima Island.

Figures

FIGURE 1. Holotype of Navigobius dewa, AMS I. 44800 – 001, from Kagoshima, Japan.

FIGURE 2. Head of Navigobius dewa, showing sensory papillae on side of head; arrow indicates lower attachment of gill membrane.