Hastatobythites arafurensis Machida, 1997

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 : 4-7

Hastatobythites arafurensis Machida, 1997

Figs. 1 , 2 , 25 , Tables 1–3

Hastatobythites arafurensis Machida 1997: 386 , figs. 1–2 (type locality: Arafura Sea, 9°18’S, 133° 25’E).

Material examined (1 specimen and photo and radiograph of holotype NTM S. 12904-011): Paratype: NTM S.12904-018, female, 57 mm SL, NNE of Money Shoal, Arafura Sea. 9°18’S, 133°25’E, otter trawl, 146 m, 7 Nov. 1990.

Remarks on material: Two specimens known from the same locality. A specimen (AMS I.29749-002) caught off New South Wales was originally identified as H. arafurensis and cited by Nielsen et al. (1999: 105). It is now correctly referred to Saccogaster tuberculata ( Chan, 1966) .

Diagnosis. See diagnosis for Hastatobythites

Description. The major meristic and morphometric characters are shown in Table 3 . Head and body elongate and strongly compressed with tapering caudal part and blunt snout. Posterior part of body fully scaled, anterior part with a few scales in midline and head naked. No visible lateral line. Dorsal fin origin above proximal part of pectoral fin and anal fin origin well behind midpoint of fish. Pectoral fin ending less than halfway to anus with peduncle a little longer than broad. Anterior gill arch ( Fig. 2 D) with 4–5 knobs on upper branch, a developed raker in angle and lower branch with two developed rakers with a knob between followed by 11 knobs; all rakers and knobs with small, densely placed spines. Long rakers about twice the length of gill filaments. Two small pseudobranchial filaments. Head pores on paratype difficult to observe.

Axial skeleton (based on radiographs): Number of precaudal vertebrae 15. Anterior neural spine one fifth the length of second spine. Neural spines 4–5 to 6–7 gradually decreasing in length. Pointed tips on neural spines 1–2 to 4–5, blunt tips on spines 6 to 9–11 and remaining vertebrae with neural and haemal spines pointed. Vertebrae 3–4 to 6 with depressed tips and vertebrae 3–7 with enlarged basal parts. Parapophyses developed on vertebrae 6–15. Pleural and epipleural ribs show up so poorly on radiographs that counts are questionable.

Dentition (based on paratype): Vomer and palatines with granular dentition in irregular rows and no fangs. Dentaries with 15–20 fangs in inner row and many small, pointed teeth in irregular outer rows. Premaxillaries with many small, pointed teeth in irregular rows and a few fangs near symphysis.

Head morphology ( Fig. 2 A–C): Head profile with minor concavity above eyes. Two spines in midline of head; a larger, free, forward-directed frontal spine placed above eyes and a smaller, ethmoidal spine partly covered by skin in front of eyes. Three median bony ridges on dorsum behind frontal spine (length 6.5 % SL). Anterior nostril placed close to upper lip and larger posterior nostril 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. No neuromasts visible. No head pigmentation visible. Upper jaw ends well behind eye with posterior margin vertically expanded. Opercular spine flat but pointed not reaching hind margin of opercle. No spine at lower angle of preoperculum.

Otolith ( Fig. 2 E–F): Otolith elongate, thin; otolith length to height = 2.5, otolith height to thickness = 2.1. Dorsal and ventral rims regularly and shallow curved, dorsal rim with slight predorsal lobe. Anterior and posterior tips regularly rounded resulting in an oval appearance of the otolith. Inner face flat with centrally positioned, undivided small, oval, shallow sulcus; otolith length to colliculum length = 2.7. Outer face flat.

Coloration. Paratype uniformly lightbrown, dorsal part of head darker and eyes bluish with light lens.

Biology and distribution ( Fig. 25 ). A viviparous species occurring on the lower continental shelf. Holotype a male with simple intromittant organ. Paratype a female with 4 embryos (4–5 mm long) with red-brown eyes, up to 20 scattered, red-brown spots on body and a short, brown stripe above abdomen ( Fig. 1 C). Known from two specimens caught in the same trawl haul in the Arafura Sea from a depth of 146 m.

Figures

FIGURE 1. Hastatobythites arafurensis: A—Paratype, NTM S. 12904 - 018, SL 57 mm (photo M. Krag). B-Paratype, dorsal view of head (photo N. Ioannou). C—Embryo from paratype, 4.5 mm (photo M. Krag).

FIGURE 2. Hastatobythites arafurensis, paratype: A-Lateral view of head. B-Dorsal view of head. C-Lateral radiograph of head. D-Anterior right gill arch. E-Median view of right sagitta. F-Dorsal view of right otolith.

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

Tables

TABLE 3. Meristic and morphometric characters of Hastatobythites arafurensis.

	HT NTM 12904-011*	PT NTM 12904-018
Standard length	52	57
Meristic characters
Dorsal fin rays	100	99
Caudal fin rays	12	12
Anal fin rays	64	65
Pectoral fin rays	16	17
Pseudobranch. fil.	2	2
Precaudal vertebrae	15	15
Total vertebrae	57	58
Long rakers on anterior gill arch	3	3
Ant. dorsal ray above vertebra no.	6	6
Ant. anal ray below dorsal fin ray no.	38	39
Ant. anal ray below vertebra no.	26	26
Morphometric characters in % SL
Head length	25.0	23.0
Head width	6.0	5.6
Depth origin anal fin	14.5	13.0
Body width	3.9	3.5
Upper jaw	14.0	13.5
Posterior maxil. height	6.0	5.6
Diameter of orbit	2.5	2.5
Interorbital width	2.5	1.9
Postorbital length	-	18.0
Preanal length	61	57
Predorsal length	31.5	29.5
Base of pelvic fin to anal fin origin	39.0	40.5
Pectoral fin length	16.0	16.0
Pelvic length	1.3	1.4
*Data from Machida (1997) and radiographs