Atractoscion atelodus ( Günther, 1867 )

Song, Young Sun, Kim, Jin-Koo, Kang, Jung-Ha & Kim, Seong Yong, 2017, Two new species of the genus Atractoscion, and resurrection of the species Atractoscion atelodus (Günther 1867) (Perciformes: Sciaenidae), Zootaxa 4306 (2), pp. 223-237 : 225-227

Atractoscion atelodus ( Günther, 1867)

English name: Small lunate caudal fin croaker; Korean name: Kko-ma-cho-seung-kko-ri-min-eo ( Figs 1–2 , Tables 2–3)

Otolithus atelodus Günther, 1867: 60 , holotype, BMNH 1866.6 .19.9, from Australia ; Macleay, 1881: 521 (Sydney, Australia).

Zeluco atelodus: Whitley, 1931: 317 .

Otolithus teraglin Macleay, 1881: 48 (Sydney, New South Wales).

Atractoscion aequidens (not of Cuvier, 1830): Trewavas, 1977: 283; Chao & Trewavas, 1990: 815; Sasaki, 1996: 84; Bray et al., 2006: 1258.

Holotype. BMNH 1866.6 .19.9, 263.0 mm SL, Sydney market, Australia; no collection data.

Paratypes. Holotype of Otolithus teraglin , AMS I.9773, 515.0 mm SL, Sydney market, New South Wales, Australia, no collection date; AMS I.26027-009 (207.0 mm SL), New South Wales, Australia (29° 39' S, 153° 23' E), caught by demersal prawn trawl, 24 Mar 1985, collected by FRV Kapala ; AMS I.27322-008 (210.0 mm SL), New South Wales, Australia (32° 08' S, 152° 31' E), caught by demersal prawn trawl, 1 Oct 1985, collected by FRV Kapala ; AMS I.43816-002 (170.0 mm SL), New South Wales, Australia (32° 51' S, 151° 53' E), caught by demersal trawl, 2000, collected by NSW Fisheries; AMS I.46169-001 (107.0 mm SL), New South Wales, Australia (29° 05' 53" S, 153° 26' 30" E), caught by demersal trawl, 26 Mar 2013, collected by NSW Fisheries.

Diagnosis. Dorsal fin soft rays, 31–34 (31); gill rakers 7 + 1 + 7–9 in first gill arch; lateral line 70–73 pored scales; no canines in adults; caudal fin emarginate; distribution south-eastern Australia.

Description. D XI, 31–34 (31); A II, 9; P 1 18–19; P 2 I, 5; C 9 + 5; GR 7 + 1 + 7–9; vertebrae 25. The counts and measurements for two specimens are given in Tables 2 and 3. Largest examined specimen was 515.0 mm SL. Overall view of the body is shown in Figure 2 .

Body compressed. Head small; eye large, its diameter shorter than snout length, preorbital length longer than postorbital region. Two pair of nostrils, anterior nostrils circular, posterior nostrils an elongated ellipse; posterior nostrils larger than anterior nostrils. Mouth large; lower jaw located in front of upper jaw; posterior margin of upper jaw slightly extending to posterior margin of eye diameter; posterior margin of maxillary slightly angular. Both jaws with teeth; tips of teeth hook-like, curving toward inner oral cavity; anterior of upper jaw with 2–3 rows of teeth, and posterior of jaw with one row; anterior of lower jaw with 2 rows of teeth, and posterior with one row; inner teeth larger than outer teeth; teeth on vomer or palatines absent. Dorsal margin of snout forming slightly convex ridge. Interorbital region slightly concave. No sensory pores around eyes or jaws. Gill opening large; margin of the preopercle with a spine covered by thin membrane; upper margin of opercle with two spines covered by thin membrane. Gill rakers of first gill arch short, dentate, sparse; 7 on upper limb, 8–10 on lower limb. Isthmus located vertically below posterior margin of eye. Dorsal fin composed of 11 spines and 31–34 rays. Origin of dorsal fin located above and behind gill opening, with its posterior base extending in front of caudal peduncle. Origin of anal fin located below 21st to 23rd dorsal-fin soft rays, its posterior tip not extending beyond the posterior margin of dorsal fin. Anal-fin base short; soft rays longer than spines. Pectoral fin slightly short, its origin located vertically below origin of dorsal fin; tip of pectoral fin not extending to tip of pelvic fin. Origin of pelvic fin located directly below or slightly behind origin of pectoral fin; tip of pelvic fin extending to directly below or slightly behind tip of pectoral fin. Caudal peduncle length longer than its depth. Caudal fin emarginate, fin shorter than the head length. Body covered with scales, except for jaws; scales on base of caudal fin. Lateral line from upper region of gill opening to margin of caudal fin, lateral line pored scales from upper region of gill opening to base of caudal fin.

Colouration of holotype when fixed: body overall silver; dorsal region bluish-brown; dorsal-fin base darkish; ventral surface, head, cheek, operculum, below lower jaw, preorbital and suborbital region silver; snout tip dark drown; inside of the mouth and gill cover yellow to pinkish-yellow; around anterior nostrils blackish; dark-brown pattern behind the base of pectoral fin; membrane of dorsal fin light brown; anal, pectoral and pelvic fins pale yellow; margin of caudal fin yellow, centrally dark brown.

Geographic distribution. Endemic to south-eastern coast of Australia.

Remarks. Günther (1867) described Otolithus atelodus based on a single specimen from Australia, preserved in the National History Museum, London, UK (BMNH 1866.6.19.9). Original description included some meristic characteristics (dorsal fin rays X + I, 31; anal fin rays II, 9), but little additional information. Macleay (1881) reported O. teraglin (common name “Teraglin”) from Australia, and noted the presence of 70 lateral line pored scales, based on the holotype in the Australian Museum (AMS I.9773). Trewavas (1977) considered that these two species were synonymous with Atractoscion aequidens . However, our results show that A. aequidens can be distinguished from the other Atractoscion species based on meristic and morphometric data. A. atelodus is clearly distinguished from A. aequidens and A. nobilis in having more dorsal-fin soft rays (31–34) than A. aequidens (26– 29) and A. nobilis (21–22). O. teraglin was reported to have 70 lateral line pored scales (Macleay 1881). A. atelodus has 70–73 pored lateral line scales. In addition, our molecular data demonstrates that specimens identified as A. atelodus from Australia belong to a distinct taxon. A. atelodus is further distinguished from A. aequidens in its distribution ( Australia for the former, and South Africa for the latter; Henriques et al. 2014). The 506 bp sequences of mtDNA COI from A. atelodus specimens from Australia differed considerably (5.1–5.3%) in Kimura’s genetic distances from those from A. aequidens specimens from South Africa ( Fig. 3 , Table 4). Therefore, we conclude that A. atelodus ( Günther 1867) should be resurrected.

Figures

FIGURE 1. Map showing the distribution area of Otolithus aequidens, MNHN A – 5586 (*), Atractosion atelodus, BMNH 1886.6. 19.9 (□), Otolithus californiensis, NMW _ 31129 and Otolithus californiensis, MCZ 10898 (Ǫ), Otolithus teraglin, AMS I. 9773 (□), Atractoscion macrolepis sp. nov., SAIAB 187117 – 1, 2, 6 and 7 (Δ), Atractoscion microlepis sp. nov., PKU 9312 – 9316, 10774 – 10783 (●).

FIGURE 2. Photographs of the type specimens. (A) Atractoscion atelodus, holotype, BMNH 1886.6. 19.9, 263.0 mm SL, Australia (previously reported as Otolithus atelodus); (B) Atractoscion macrolepis sp. nov., holotype, SAIAB 187117 – 2, 284.0 mm SL, Tombua beach of Angola; (C) Atractoscion microlepis sp. nov., holotype, PKU 9315, 280.0 mm SL, Gulf of Oman, illustration of dorsal view of swimbladder (left below) and sagitta in otolith (right below).

FIGURE 3. NJ-tree showing relationships among Atractoscion species including Atractoscion microlepis sp. nov. and Atractoscion macrolepis sp. nov. Numbers at branches indicate bootstrap probabilities in 5000 bootstrap replications. Bar indicates genetic distance of 0.02. * Atractosion atelodus was resurrected from synonym of A. aequidens.