Saccogaster tuberculata ( Chan, 1966 )

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 : 22-26

Saccogaster tuberculata ( Chan, 1966)

Figs. 17 , 18 , 25 , Table 1 , 2, 6

Barbuliceps tuberculatus Chan 1966: 4 , figs. 1–2 (type locality: South China Sea). Saccogaster tuberculata: Cohen 1987: 3 ; Nielsen et al. 1999: 110.

Material examined (18 specimens, 84–160 mm SL). Holotype: BMNH 1965.11.6.1, male, 106 mm SL, South China Sea, 6°01’48’’N, 109°57’24’’E, R/V Cape St. Mary, cr. 7/64, st. 32, Agassiz trawl, 823–834 m, 5 Nov. 1964. Nontypes: USNM 207354, 2 females (1 cleared and stained) and ZMUC P77550, female, 95 mm SL, off Hawaiian Islands, 21°06’N, 156°13’W, R/V Townsend Cromwell, 52–88, shrimp trawl, 585–640 m, 3 Mar. 1971. BSKU 29526, female, 138 mm SL, Kyusu-Palau ridge, 28°04’N, 134°41’E, R/V Shinkai-Maru, No. 53, beam trawl, 523 m, 18 Dec. 1979. AMS I.22814-029, female, 160 mm SL, off Northwest Australia, 18°29’S, 116°36’E, R/V Soela, st. SO 2/82/ 26 ,27, Engel trawl, 696–704 m, 6 Apr. 1982. AMS I.26002-005, female, 84 mm SL, off New South Wales, 33°34’S, 152°2’E, R/V Kapala, st. K 86-01-06, bottom trawl, 658 m, 11 Feb. 1986. IOM 0 0 498, male, 94 mm SL, Mozambique Channel, 12°28’30’’S, 48°09’54’’E to 12°26’S, 48°08 E, R/V Vityaz, cr. 17, st. 2601, bottom trawl, 700–710 m, 12 Nov. 1988. AMS I.29749-002, female, 90 mm SL, off New South Wales, 32°40’S, 152°51’E to 32°38’S, 152°54’E, R/V Kapala, K 89-17-02, bottom trawl, 814–850 m, 15 Aug. 1989. MNHN 2002-3143, female, 119 mm SL, Chesterfield Islands, 19.7°S, 158.83°E, Musorstom 5, st. cc384, bottom trawl, 756–772 m, 21 Oct. 1986. MNHN 2000-0677, female, 147 mm SL, Vanua Balavu, Fiji Islands, 17.33°S, 178.7°W, R/V Buge, cr. 40, st. cp 1431, bottom trawl, 495–500 m, 2 Mar. 1999. MNHN 2006-0588, female, 100 mm SL, Solomon Islands, 8.38°S, 159.47°E, Camp. Salomon 2, st. cp2194, bottom trawl, 440–521 m, 24 Oct. 2004. MNHN 2006-0702, male, 112 mm SL, Solomon Islands, 7.62°S, 157.75°E, Camp. Solomon 2, cr. cp2214, 550– 682 m, 26 Oct. 2004. MNHN 2006-0090, male, 113 mm SL, Solomon Islands, 7.71° S, 156.47°E, Camp. Salomon 2, st. cp2246, bottom trawl, 664–682 m, 1 Nov. 2004. MNHN 2006-0464, male, 84 mm SL, Solomon Islands, 7.7°S, 156.43°E, Camp. Salomon 2, st. cp2247, bottom trawl, 686–690 m, 1 Nov. 2004. MNHN 2006-0061, 2 females, 91–98 mm SL, Solomon Islands, 7.9°S, 156.95°E, Camp. Salomon 2, st. cp2267, bottom trawl, 590–600 m, 4 Nov. 2004. IOM (no cat. no.), 137 mm SL, off Vietnam, R/V Odissey tr. 52; no further data available.

Diagnosis. Saccogaster tuberculata differs from the other Saccogaster species by the following combination of characters: No body scales; a pair of small, sub-dermal spines on frontal plate just behind eyes, median subdermal ethmoidal spine in front of eyes; skin rather thick; large posterior mandibular pore behind end of maxilla; cartilaginous ethmoidal spine on snout; opercular spine hidden, no preopercular spine; three developed rakers on anterior gill arch almost equal in length to developed rakers; pectoral peduncle prolonged; no fangs on dentigerous bones, palatines with 3 to several tooth rows; precaudal vertebrae 14–15 and total vertebrae 55–58; fin rays in dorsal 82–93, anal 54–60 and pectoral 19–22; otolith length to height 2–2.1, otolith length to colliculum length variable, 2.5–3.3.

Similarity. Saccogaster tuberculata seems most close to S. horrida , both having developed gill rakers on anterior arch equal to or longer than long filaments, three developed gill rakers and no scales. They differ from each other by S. tuberculata having an indistinct frontal plate and small subdermal spines (vs. a distinct frontal plate with a pair of well developed, visible spines), no transverse, bony ridge on frontal plate (vs. bony ridge present), presence of a posterior mandibular pore (vs. absent), dentigerous bones without fangs (vs. vomer and premaxillaries with fangs), distance from base of pelvic fins to origin of anal fin 32.0–39.0 % SL (vs. 46.0 % SL) and ratio otolith length to height 2.1–2.2 (vs. 1.75).

Description. The principal meristic and morphometric characters are shown in Table 6 . Body compressed and elongate with tapering caudal part and blunt snout. Scales absent. Skin relatively thick, loose and semitransparent. Lateral line indistinct, originating above gill opening, descends gradually above anus and continues in midline becoming obscure posteriorly. In some specimens the 25–30 lateral line papillae are black clearly showing the course of the line. Dorsal fin origin above vertebrae 6–8 and anal fin origin below vertebrae 21–23. Pectoral fin reaching more than halfway to anus. Anterior gill arch ( Fig. 18 F) with 3–4 spiny knobs on upper branch, a developed raker in angle and lower branch with two developed rakers with a knob between followed by 7–11 knobs. Number of knobs varies between 14 and 19. Two pseudobranchial filaments. Intromittent organ of holotype on a thick, fleshy, posteriorly directed stalk with the vent immediately anterior to its base; distal rim of stalk swollen and divided into two lobes, with a small penis in the middle; sections of the testes show spermatozoans arranged in spermatophores. In USNM 207354 (SL 130 mm) ovaries contain several hundred dark-eyed, uniformly brownish embryos with yolk sacs.

S. staigeri S. tuberculata Axial skeleton (based on radiographs): Number of precaudal vertebrae 14–15. Anterior neural spine one fourth length of second spine. Neural spines 2 to 4–5 long and compressed and with pointed tips, spines 6–11 with blunt tips and vertebrae 4–8 with enlarged basal part. Parapophyses on vertebrae 7 to 14–15, pleural ribs on vertebrae 2–10 and epipleural ribs on vertebrae 4–10. Pleural and epipleural ribs often indistinct.

Dentition: Fangs absent. Dentition granular. Palatines with 3 to several, irregular tooth rows. Vomer boomerang-shaped and with 3–4 tooth rows. Premaxillaries and dentaries with several, irregular tooth rows. Number of tooth rows seems to increase with standard length.

Head morphology ( Fig. 18 A–E): Head profile straight above eyes. Head with pair of small, sub-dermal spines on frontal plate above and behind eyes, small, median, sub-dermal, ethmoidal spine in front of eyes and blunt subdermal spine above eyes. Sub-dermal surface of frontal plate behind frontal spines slightly textured. Anterior nostril 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, loose, tighter in small specimens and then translucent and sometimes with faint indications of 1–3 subdermal neuromasts below and behind eyes. No head pigmentation visible. Upper jaw ends well behind eye; posterior end of maxilla vertically expanded. Opercular spine pointed, subdermal, not reaching hind margin of opercle. No spine at lower angle of preoperculum.

Otolith ( Fig. 18 G–J): Otolith elongate, moderately thick; otolith length to height = 2.0–2.2, otolith height to thickness = 1.9–2.2. Ventral rim regularly curved, smooth; dorsal rim regularly curved or broadly undulating. Anterior tip moderately pointed; posterior tip slightly pointed or rounded. Inner face flat with centrally positioned, undivided oval, shallow sulcus with distinct anterior projection and somewhat elevated colliculum; otolith length to colliculum length variable, 2.5–3.3. Outer face markedly convex.

Coloration: Recently caught specimens often with brownish snout, dark dorsum and black papillae on head and in lateral line.

Biology and distribution ( Fig. 25 ). The 18 examined specimens were caught in bottom fishing gear at depths of 440–850 m from off East Africa to Hawaii .

Remarks on variability. Saccogaster tuberculata is the most widely distributed species of the genus. It also shows a remarkably high variation of certain characters, which however is not consistent enough to warrant distinction of separate species. Particularly it appears that it is always single characters that make the distinction of any given variation, which is not supported by any independent second character. Two specimens from Hawaii , the northeastern-most occurrence of the species, show otoliths with a regularly curved dorsal rim ( Fig. 18 G), whereas all others exhibit an undulating dorsal rim. The southwestern-most specimen, from off Madagascar, has a tight head skin (vs. mostly loose) and a distinctly narrower interorbital width (3.4 % SL vs. 3.9–5.6 % SL). A specimen from off New South Wales, Australia, has a single, feeble neuromast ( Fig. 18 E) and two specimens from off the Solomon Islands show 2 and 3 neuromasts, respectively, all on the upper lip behind the eye. A few specimens from off the Solomon Islands show dusky pigmentation on the posterior part of the body.

Figures

FIGURE 17. Saccogaster tuberculata, holotype, BMNH 1965.11. 6.1, SL 106 mm, (photo M. Krag).

FIGURE 18. Saccogaster tuberculata: A—Lateral view of head (USNM 207354). B—Lateral radiograph of head (ZMUC P 77550). C—Dorsal view of head (USNM 207354). D—Ventral view of head (USNM 207354). E—Lateral view of head (AMS I. 26002 - 005). F-Anterior right gill arch (USNM 207354, from Cohen & Nielsen 1972). G—Median view of right otolith (ZMUC P 77550). H—Dorsal view of right otolith (ZMUC P 77550). I—Median view of right otolith (MNHN 2000 - 0667). J—Median view of right otolith (IOM 00498).

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

Tables

TABLE 6. Meristic and morphometric characters of Saccogaster staigeri and S. tuberculata.

	HT	PT + 3 spms	HT	17 non-types
Standard length	93	49–65	106	84–160
Meristic characters
Dorsal fin rays	87	86(87.2)88	85	82(87.7)93
Caudal fin rays	12	12	12	11(11.9)12
Anal fin rays	54	53(54.2)57	59	54(57.6)60
Pectoral fin rays	18	18(18.4)19	22	19(19.8)21
Pseudobranch. fil.		2	2	2
Precaudal vertebrae	14	13(13.8)14	14	14(14.5)15
Total vertebrae	51	53(53.2)54	56	55(56.5)58
Long rakers on anterior gill arch	3	3	3	3
Ant. dorsal ray above vertebra no.	7	6(7.0)8	7	6(7.2)8