Saccogaster hawaii Cohen & Nielsen, 1972

Nielsen, Jørgen G., Schwarzhans, Werner & Cohen, Daniel M., 2012, Revision of Hastatobythites and Saccogaster (Teleostei, Bythitidae) with three new species and a new genus, Zootaxa 3579, pp. 1-36 : 10-12

Saccogaster hawaii Cohen & Nielsen, 1972

Figs. 5 , 6 , 25 , Tables 1 , 2, 4

Saccogaster hawaii Cohen & Nielsen 1972: 455 , figs. 1, 3 (type locality: off Maui, Hawaian Islands); Nielsen et al. 1999: 109.

Material examined (1 specimen, 69 mm SL). Holotype: USNM 207355, female, 69 mm SL, off Maui, Hawaii , 21°00’N, 156°47’W, R/V Townsend Cromwell, st. 40–62, bottom trawl, bottom temp. 15.9°C, 234 m, 19 Nov. 1968.

Diagnosis. Saccogaster hawaii differs from all other Saccogaster species by the opercular spine ending in three prongs. Also the following combination of characters is diagnostic: A pair of sub-dermal spines on frontal behind and above eyes, median sub-dermal ethmoidal spine in front of eyes with forward pointed tip; three developed rakers on anterior gill arch hardly longer than the knobs, extremely small filaments on anterior gill arch; scales absent on predorsal and present on median part of body; thin, transparent skin; palatines with single row of teeth; elongate pectoral peduncle longer than high; precaudal vertebrae 18 and total vertebrae 54; fin rays in dorsal 92, anal 55 and pectoral 22.

Similarity. Saccogaster hawaii seems most similar to S. brayae (see comparison above).

Description. The principal meristic and morphometric characters are shown in Table 4 . Head and body elongate and compressed with tapering caudal part and blunt snout. Scales absent from predorsal part and from band along bases of dorsal and anal fins. Anteriormost scales widely scattered, those more posteriorly positioned closely spaced and on rear of body regularly imbricate. Lateral line indistinct. Dorsal fin origin above distal part of pectoral peduncle, anal fin origin well behind midpoint of fish and pelvic fins inserted below hind margin of opercle, ending below middle of pectoral fin. Anterior gill arch ( Fig. 6 D) with three barely developed rakers scarcely longer than the three spiny knobs on upper branch and the knobs on lower branch. Very short gill filaments on anterior arch. No pseudobranchial filaments observed. No intromittent organ developed so it is probably an immature female. A pair of elongate gonads visible through transparent skin.

Axial skeleton (from radiographs): Number of precaudal vertebrae 18. Anterior neural spine very short. Neural spines 2–4 long, depressed and with pointed tips. Neural spines 5–18 with short, blunt spines. Parapophyses developed on vertebrae 7–18. Pleural ribs distinct on vertebrae 3–6.

Dentition: Palatines with 10–15 sharp, pointed teeth in a single row. Vomer with 6 teeth similar to the longer premaxillary teeth plus a scattering of smaller teeth. Premaxillaries with band of small, granular teeth and near symphysis as series of 8 elongate, needlelike teeth in a widely spaced row. Dentaries with an irregular row of about 15 longer, pointed teeth and an outer narrow band of shorter teeth.

Otolith: Not extracted from unique holotype.

Head morphology ( Fig. 6 A–C): A pair of forward directed sub-dermal frontal spines behind and above eyes, a large, median, sub-dermal ethmoidal spine in front of eyes with forward pointed tip and a blunt sub-dermal spine above each eye. Five faint neuromasts below eye curving upwards and two on snout inward of posterior nostril. Upper jaw ends well posterior to eye with posterior margin vertically expanded and not sheathed dorsally. Opercle with a flattened, antler-like, 3–pronged spine ( Fig. 6 A).

Coloration: Body pale with fine, brown pigmentation along the bases of dorsal and anal fins. Similar pigmentation on head, particularly on snout and between eyes, and an intense dark band from behind eye becoming more diffuse posteriorad.

Biology and distribution ( Fig. 25 ). Saccogaster hawaii is only known from the holotype caught at the upper continental shelf at a depth of 234 m off Maui, Hawaiian Islands.

Figures

FIGURE 5. Saccogaster hawaii, holotype, USNM 207355, SL 69 mm (from Cohen & Nielsen 1972).

FIGURE 6. Saccogaster hawaii, holotype: A—Lateral view of head. B—Lateral radiograph of head (photo S. Raredon). C—Dorsal view of head. D—Anterior right gill arch.

FIGURE 25. Geographic distribution of Hastatobythites and Saccogaster in the Indo-West Pacific. Each marking may represent more than one locality.