Optivus agrammus, Gomon, 2004

Gomon, Martin F., 2004, Two New Species of Roughy (Trachichthyidae: Optivus) from Coastal Waters of Southern Australia, Records of the Australian Museum 56 (2), pp. 173-178 : 176-178

Optivus agrammus n.sp.

Figs. 1, 2; Tables 1, 2

Optivus elongatus (non Günther, 1859). McKay, 1970: 6; Kotlyar, 1980: 217.

Optivus n. sp. —May & Maxwell, 1986: 220; Paxton et al., 1989: 365.

Optivus sp. 2 .— Gomon, 1994: 407, fig. 365; Kotlyar, 1996: 182.

Type material. HOLOTYPE: CSIRO H.5316-08 (86.7), central Great Australian Bight, South Australia, 31°50'S 130°45'E, 54 m, trawl, 14 May 2000, SS01/00/380, FRV Southern Surveyor . PARATYPES: CSIRO CA3459 (70.9), south of Point Dover, Great Australian Bight , Western Australia, 32°50'S 125°31'E to 32°48'S 125°32'E, 50– 44 m, trawl, 7 March 1979 , F. V. Courageous ; CSIRO CA3460 (82.4), south of Point Dover, Great Australian Bight , Western Australia, 32°50'S 125°31'E to 32°48'S 125°32'E, 50– 44 m, trawl, 7 March 1979 , F. V. Courageous ; CSIRO H.5316- 09 (3, 76.9–91.0), same data as holotype ; NMV A24987- 001 (73.5), 6 mi (9.6 km) off Venus Bay , South Australia, 18–25 fms (33–46 m), June 1982 , T. Olsen ; SAMA A478 (72.7), presumably 34°25.0'S 133°25'E to 34°25.0'S 133°23'E, 128–130 m, 15August 1981 , SO3/81/65, FRV Soela ; SAMA A744 (2, 72.0–74.3), western Great Australian Bight , Western Australia, 33°15'S 125°24'E to 33°13'S 125°24'E, 60– 61 m, 29 July 1981 , SO3/81/13, FRV Soela ; SAMA A776 (51.7), western Great Australian Bight , Western Australia, 34°10'S 124°31'E to 34°11'S 124°32'E, 320–380 m, 29 July 1981 , SO3/81/9, FRV Soela ; SAMA A1664 (80.0), same data as NMV A24987-001 ; WAM P.15263 (62.3), Lookout Point, Cheyne Beach , Western Australia, 34°53'S 118°25'E, trawl, 19 April 1980 , B. Hutchins et al.; WAM P.26608-08 (54.7), west of Fremantle, Western Australia, 32°09'S 114°27'E, trawl, 1965, Suruga Maru .

Diagnosis. Gill rakers 20–24, modally 22; lateral profile of nape and dorsal surface of head gently curved, nearly horizontal in front of dorsal-fin origin, almost straight between eyes; tip of snout broadly rounded; depth of head at vertical through upper end of gill opening 2.7–2.9 times in SL; snout length 1.5–2.6 times in eye diameter; inner row of teeth on premaxilla noticeably longer than others;

caudal peduncle relatively short and deep, depth 0. 9–1.2 in length; dorsal and anal fins relatively low, third segmented dorsal-fin ray 3.8–4.6 times in SL, first anal-fin ray 5.6–8.2 times in SL; body greenish brown on back, silvery below; fins almost uniformly pink, though slightly dusky tips to caudal-fin lobes persisting in recently preserved large specimens.

Description. Dorsal-fin rays IV, 11 (III, 11 and IV, 10 in two of 13 paratypes); anal-fin rays III, 9 (III, 10 in 1); caudalfin rays 6 (7 in 12) + 19 + 6 (5 in 2); pectoral-fin rays 12 (11 in 2 and 13 in 1 of 26 fins counted); vertebrae 12 + 14; lateral-line scales 26; scales above lateral line approximately 9 (9–11); scales below lateral line approximately 12 (12– 15); predorsal scales approximately 27 (27–29); ventral scutes 11 (9 in 3 and 10 in 5); total gill rakers 22 (20–24, modally 22; Table 2). (See Table 1 for morphometric values).

Body of moderate depth; caudal peduncle rather short and deep, tapering only slightly posteriorly; anus positioned well behind pelvic-fin bases, just in advance of anal-fin origin; no apparent luminescent tissue. Head and snout rounded; dorsal outline of nape and head gently curved in lateral profile, nearly horizontal in front of dorsal fin, almost straight between eyes; snout short, not projecting in advance of mouth; posttemporal spine short and sharp. Posterior edge of preopercle finely serrate, posteroventral corner produced as broad spine reaching nearly to hind edge of operculum. Dorsoposterior corner at rear end of maxilla positioned vertically below posterior margin of orbit. Gill rakers on upper limb of first arch long and slender.

Oral edge of premaxilla and dentary broadly covered with fine teeth of similar size, dentigerous surface extending laterally around expanded anterior end of dentary to underside. Vomer naked; palatine covered with fine teeth.

Scales adherent, each with numerous rows of strong ctenii obscuring scale margins and making determination of squamation patterns difficult; single row of scales overlapping onto bases of dorsal and anal fins. Predorsal scales on dorsal midline of head reaching just in advance of vertical through centre of orbit on dorsal midline of head. Cheek scales reaching forward just in advance of vertical through posterior extent of orbit. Lateral-line pores mostly obscured by ctenii. Scales on ventral midline between pelvic-fin bases and anus modified as moderately large bony scutes.

Dorsal fin short based, continuous, spines and rays increasing in length progressively to third soft ray, subsequent rays gradually decreasing in length; first soft ray unbranched, remaining rays branched; origin of fin above centre of pectoral fin. Anal fin short based, first spine tiny, spines and rays increasing in length progressively to second soft ray, subsequent rays subequal or decreasing slightly in length. Caudal fin distinctly forked. Posterior edge of pectoral fin curved, middle rays longest, first and last rays simple and short, second longer and also simple, others branched. Posterior tip of pelvic fin reaching about two thirds of way to anal-fin origin.

Preserved coloration (in alcohol). Body and fins pale; large, recently preserved individuals with slightly dusky caudal-fin tips.

Live coloration. See colour photo in Gomon, 1994 (fig. 365). Greenish brown on back, silver below; fins pink.

Etymology. agrammus , from the Greek a, meaning “without”, and gramme, for “line”, in reference to the absence of stripes on the caudal fin of this species.

Distribution. Known only from western and central southern Australia, between Fremantle, Western Australia and Venus Bay, South Australia, at the eastern end of the Great Australian Bight, in depths of 40– 320 m.

Discussion. Freshly preserved individuals of Optivus agrammus are readily separable from the other two species of Optivus by colour pattern, the former lacking the distinctive lengthwise dark stripe on each of the caudal-fin lobes found in its congeners (see colour photos in Gomon, 1994, of O. agastos —fig. 364 and O. agrammus —fig. 365, and Doak, 1972, of O. elongatus —pl. 8, as Hoplostethus elongatus ). Other features that differ between it and its congeners relate to the overall shape of the head, body and fins and are evident as morphometric shifts, with overlapping values ( Table 1). The distribution of characters in the species do not support any clear relationships (e.g., Fig. 2). Although O. agrammus has modally fewer gillrakers than O. agastos , both have less than O. elongatus ( Table 2). The use of the distribution of cheek scales by Gomon (1994) to separate O. agastos and O. agrammus (as O. sp. 1 and O. sp. 2, respectively) is invalid as the character is more variable than described.

The precise collection site of the paratype SAMA A478 is unclear, due to incomplete registration information. The specimen was recorded as coming from a Soela station “65” without further details. It is surmized that the specimen was taken on the same Soela cruise as the other two specimens sent to the South Australian Museum by CSIRO, both of which were registered later than this specimen, rather than from one of the three subsequent cruises to the Bight region by the vessel .

ACKNOWLEDGMENTS. I am grateful to M. McGrouther ( AMS), A. Graham ( CSIRO), J. Johnson ( QM), A. Stewart ( NMNZ), the late C.J.M. Glover ( SAMA), B. Hutchins and G. Moore ( WAM) for facilitating loans of specimens. Thanks to A. Gill ( BMNH) for reporting on types of O. elongatus . CSIRO Marine Labs and B. Hutchins also kindly provided photographs of freshly caught specimens .