Saccogaster nikoliviae, Nielsen, Jørgen G., Schwarzhans, Werner & Cohen, Daniel M., 2012

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 : 16-18

Saccogaster nikoliviae n. sp.

Figs.11 , 12 , 25 , Tables 1 , 2, 5

Material examined (3 specimens, 50–69 mm SL). Holotype: NMV A 29674-010, female, 69 mm SL, off northwestern Australia, Imperieuse L23 transect, 17°31’44’’S, 118°50’37’’E to 17°32’30’’S, 118°50’31’’E, R/V Southern Surveyor, beam trawl, 407– 403 m, 15 June 2007. Paratypes: CSIRO H 6602-01, female, 57 mm SL (same data as for holotype). NMV A 29670-021, male, 50 mm SL, off northwestern Australia, Hedland L22 transect, 18°34’12’’S, 117°27’52’’E to 18°34’04’’S, 117°28’38’’E, R/V Southern Surveyor, beam trawl, 405– 401 m, 14 June 2007.

Diagnosis. Saccogaster nikoliviae differs from all other Saccogaster species by presence of predorsal scales and by the following combination of characters: A more or less distinct pair of frontal spines above and behind eyes and a median, sub-dermal, cartilaginous, ethmoidal spine in front of eyes; numerous neuromasts below translucent head-skin arranged in four distinct clusters; scales on body; three long gill rakers on anterior arch 3–5 times length of filaments; pectoral peduncle prolonged; palatines with 2–3 tooth rows; an antero-ventrally directed spine on lower angle of preoperculum; precaudal vertebrae 12–13 and total vertebrae 52–53; fin rays in pectoral 17–18, dorsal 80–84 and anal 48–52; otolith length to height = 1.9, otolith length to colliculum length = 2.8–3.1.

Similarity. Saccogaster nikoliviae and S. parva are the only species with numerous developed neuromasts on the head. They differ in number of developed gill rakers (3 vs. 6 in S. parva ), presence of scales vs. none in S. parva , and a pair of spines behind eyes vs. none in S. parva .

Description. The principal meristic and morphometric characters are shown in Table 5 . The description is based on the holotype; differences from the two paratypes are mentioned in brackets. Body moderately compressed and elongate with tapering caudal part and blunt snout. Body covered with thin, overlapping scales on sides and on predorsal; length of scale from above pectoral fin 0.8 mm. No scales on head and abdomen. Lateral line indistinct (observed close to dorsal margin of body ending above tip of pectorals). Dorsal fin origin above proximal part of pectoral fin and anal fin origin well behind midpoint of fish. Pectoral fins ending half way to anus with peduncle not attached to body. Pelvic fins ending below anterior part of pectoral fins. Anterior gill arch ( Fig. 12 F) with three (4) knobs on upper branch, a long raker in angle and lower branch with two long rakers with a knob in between followed by seven (10) knobs; all knobs and long rakers with small densely placed spines. Long rakers on anterior gill arch 3 (5) times length of filaments. Ca. 35 very small gill filaments. Two thin pseudobranchial filaments.

Axial skeleton (from radiographs): Number of precaudal vertebrae 12–13. Anterior neural spine one fourth the length of second spine. Neural spines 4 to 8–9 gradually decreasing in length. Pointed tips on vertebrae 2 to 4–5, blunt tips on vertebrae 6 to 10–11 and the remaining vertebrae with neural and haemal spines pointed. Vertebrae 3–7 with depressed tips and vertebrae 3 to 7–8 with enlarged basal parts. Parapophyses developed on vertebrae 7–13, pleural ribs on vertebrae 3 to 7–8 and epipleural ribs on vertebrae 3–10.

Dentition: Vomer boomerang-shaped with 5–10 fangs in inner row and 20–25 small, close-set teeth in 2–3 outer rows. Palatines with about 10 fangs in inner row and many small teeth in 1–2 outer rows. Dentaries with 10–20 fangs in inner row and many, small teeth in 2–3 outer rows. Premaxillaries with 2–3 long fangs near symphysis and with granular teeth in several, irregular rows further back.

Head morphology ( Fig. 12 A–D): Head profile concave above eyes. Head with pair of small free, closely set spines on frontal above and behind eyes, sub-dermal surface of frontal plate very uneven, a median, subdermal, cartilaginous, ethmoidal spine in front of eyes and a blunt sub-dermal spine above eyes. Anterior nostril with a low rim placed close to upper lip; posterior nostril a mere hole placed close to eye. Head pores: 1 supraorbital pore at tip of snout, 2 anterior infraorbital pores below and in front of eye, 1 anterior mandibular pore at tip of jaw. Head skin thin, tight. Total of 17–18 diamond-shaped, light-colored neuromasts visible below transparent skin arranged in four cluster: 5–6 infraorbital along upper lip and curving around eye, 2 pairs between eyes, 6 supraorbital along line above opercle and behind eyes, 4 mandibular along jaw. Upper jaw ends well behind eye; posterior end of maxilla vertically expanded. Opercular spine pointed but flat, free, not reaching hind margin of opercle. Small, subdermal anterior-ventrally pointed spine at lower angle of preoperculum.

Otolith ( Fig. 12 E, G–H): Otolith oval, moderately thick; otolith length to height = 1.9, otolith height to thickness = 2.2. Dorsal and ventral rims gently and regularly curved, smooth. Anterior and posterior tips regularly rounded resulting in a symmetrical outline of the otolith. Inner face slightly convex with centrally positioned, undivided oval, shallow sulcus without anterior projection; otolith length to colliculum length = 2.8–3.1. Outer face convex.

Coloration: Head and body light brown. Head with dusky background coloration. Eyes black with lighter lens.

Biology and distribution ( Fig. 25 ). A viviparous species occurring on the upper continental slope. The holotype and a 57 mm SL paratype are females with extended ovaries and eggs up to 0.5 mm in diameter; no embryos were observed. The 50 mm SL paratype is a male with ripe testes and well developed intromittent organ. Known from three specimens caught off northwestern Australia in bottom fishing gear at depths between 401 and 407 m.

Etymology. The new species is named after two of the senior author’s grandchildren: Nikolaj and Olivia.

Figures

FIGURE 11. Saccogaster nikoliviae, holotype, NMV A 29674 - 010, SL 69 mm (photo N. Ioannou).

FIGURE 12. Saccogaster nikoliviae, holotype: A—Lateral view of head. B—Lateral radiograph of head. C—Dorsal view of head. D—Ventral view of head. E—Median view of otolith. F—Anterior right gill arch. G—Dorsal view of right otolith. H—Median view of right otolith (paratype, NMV A 29670 - 021).

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