Polysteganus lineopunctatus ( Boulenger 1903 )

Iwatsuki, Yukio & Heemstra, Phillip C., 2015, Redescriptions of Polysteganus coeruleopunctatus (Klunzinger 1870) and P. lineopunctatus (Boulenger 1903), with two new species from Western Indian Ocean, Zootaxa 4059 (1), pp. 133-150 : 140-141

Polysteganus lineopunctatus ( Boulenger 1903)

Proposed English name: Bluespotted Seabream Figures 1 B, 2B; Table 1

Dentex lineopunctatus Boulenger 1903:66 , pl. 6 (type locality: KwaZulu-Natal coast, South Africa). Dentex natalensis Gilchrist & Thompson 1908:156 (type locality: KwaZulu-Natal, South Africa).

Polysteganus coeruleopunctatus (non Klunzinger); Smith & Smith 1986:590 (in part, southwestern Africa); Heemstra & Heemstra 2004:232 (in part, Red Sea to the Eastern Cape, South Africa, Western Indian Ocean); van der Elst 1985:359, unnumbered color figure (in part, South Africa).

Holotype. BMNH 1903.2.6.5, 320 mm SL, KwaZulu-Natal coast, South Africa ( Fig. 2 B).

Other material examined. SAIAB 17470, 318 mm SL, 20 miles off Port Durnford, KwaZulu-Natal, South Africa (29°09'36''S, 32°03'49''E); SAIAB 29416, 189 mm SL, Coffee Bay, Eastern Cape Province, South Africa; SAIAB 37126, 288 mm SL, 20 miles off Port Durnford, KwaZulu-Natal, South Africa; SAIAB 48180, 148 mm SL, Mozambique; SAIAB 82139, 3 specimens, 92–196 mm SL (X), Mozambique (21°35.0'S, 35°32.3'E – 21°33.6'S, 35°32.2'E), bottom trawl, 17 October, 2007, collected by P.C. & E. Heemstra; SAM 9908 (1 of 2 syntypes of Dentex natalensis ; 1 missing, M. Bougaardt pers. comm.), 283 mm SL, KwaZulu-Natal, South Africa, southwestern Indian Ocean, collected by R. Robinson.

Diagnosis. Distinguished from all congeners of Polysteganus by the following combination of characters: scale rows above lateral line 7½; scales rows between 5th dorsal-fin spine base and lateral-line 5½; higher counts of pored lateral-line scales (53–55); suborbital depth clearly less than or subequal to orbit diameter; dorsal-fin rays reddish pink or orangish red but with deep yellow upper margin of dorsal-fin rays; 7 or 8 distinct irregular lines of blue spots on body (often present even in preserved specimens); pale reddish yellow membranes on caudal-fin lobes and caudal fin with hyaline white margin on lower fin lobe; no blue iridescence on dorsal and lateral side of whitish pink body; canines somewhat smaller, only upper canines visible when mouth closed; body slender, 40– 43% (mean 42%) of SL; no bony bulge before and above eye even in larger specimens of over 25 cm TL; caudal fin moderately forked.

Description. Counts and proportional measurements as percent of SL of the holotype and other specimens (included as synonymized type) of Polysteganus lineopunctatus are given in Table 1 .

Body depth relatively deeper; head robust, rostro-occipital profile strongly convex; interorbital scaly, scales extending to nearly above anterior nostrils and just above posterior nostrils, anterior nostrils small and rounded, posterior nostrils oval; orbit diameter greater than interorbital width; maxilla naked, its posterior end not reaching vertical at front edge of eye, rear margin of maxilla not concealed by infraorbitals; jaws robust, especially upper jaw; canines slender and very short, 4 in upper and 6 in lower jaw (two outermost canines in upper jaw larger than 2 medial canines, and two outermost canines of lower jaw larger than 4 medial canines; an outer lateral row of conical teeth and a series of villiform teeth on inner side of outer lateral teeth row; mandibular profile slightly convex; rear margin of preopercle rounded and feebly serrated, a narrow naked area (preopercle with keel-like ridge), between preopercle flange scaly area and cheek scales; first to third dorsal-fin spines progressively longer, fourth dorsal-fin spine longest, slightly greater than snout length; no sheath scales on dorsal and pelvic-fin rays; predorsal length subequal to or slightly less than body depth, and clearly less than dorsal-fin base length; lateral line gently curved, almost parallel to curved profile between dorsal outline and lateral line, giving an impression of a more slender body than that of the similar species, P. coeruleopunctus ( Figs. 1–2 ); pectoral-fin base scaly and fin rounded posteriorly, two or three lowest rays slightly extended posteriorly, compared with rays above ( Fig. 2 B, of the holotype shows this feature), fin tip reaches vertical at anus, its length clearly less than head length; first pelvic fin ray definitely greater than fourth dorsal-fin spine, fin tip not reaching beyond vertical at pectoral-fin tip and rear margin of anus; soft dorsal and anal fins with no scales; anal fin with moderate scaly sheath, anal-fin spines slender, second and third subequal, and slightly greater than orbit diameter; caudal fin lobes broad and wide, caudal fin moderately forked ( Figs. 1 A, 2A); scales ctenoid; gill-rakers lanceolate; vertebrae 10+14.

Color when fresh, based on color photographs of specimens (SAIAB 82139, 198 mm SL, Mozambique, and uncatalogued SAIAB photograph, 275 mm TL, Mozambique, photographed by O. Alvheim; Fig. 1 B): head and body uniform reddish orange with silvery reflection at center of each scale, color of upper head and dorsolateral part of body brighter than lower head and abdominal part of body; iris golden and pupil black; all fins uniform reddish orange, but membrane of spinous dorsal-fin hyaline reddish, and more whitish in pelvic and anal fins.

Color of preserved specimens: upper sides of head and trunk uniform yellowish-tan.

Distribution. Polysteganus lineopunctatus ( Boulenger 1903) is currently known only from South Africa and Mozambique, and is endemic to the southwestern Indian Ocean. No confirmed reports of this species from Madagascar.

Remarks. Polysteganus lineopunctatus has long been considered a junior synonym of P. coeruleopunctatus (Klunzinger 1873) but is justified as a valid species in this study. The counts and proportional measurements of type material show it to be different ( Table 1 ). Genetic data ( Fig. 4 ) also supports the validity of P. lineopunctatus .

Polysteganus lineopunctatus differs from P. coeruleopunctatus in having 5½ scales rows between 5th dorsalfin spine base and lateral line (vs. 5½ or 6½ scale rows in the latter); 53–55 pored lateral-line scales (vs. 50 or 51 pored lateral-line scales); very weak bony bulge before and above eye, forming a low median ridge (vs. weak bony bulge, becoming prominent in specimens over 25 cm SL); anal-fin rays whitish pink (vs. anal-fin rays pinkish basally); with 7 or 8 distinct irregular blue spotted lines on small to large adults (vs. 7 or 8 faint irregular blue spotted lines).

Dentex natalensis Gilchrist & Thompson 1908 also has long been synonymized under Polysteganus coeruleopunctatus ( Klunzinger 1870) , but one of two syntypes (SAM 9908) clearly has the same counts and morphometric characters as P. lineopunctatus , shown in Table 1 . Another syntype was lost in 2009 (M. Bougaardt of SAM, pers. comm.). We accordingly conclude that Polysteganus natalensis ( Gilchrist & Thompson 1908) is a junior synonym of P. lineopunctatus ( Boulenger 1903) .

Figures

FIGURE 1. Polysteganus coeruleopunctatus A and P. lineopunctatus (B). A), HUJF 20120, 226 mm SL, Eilat, Israel, Red Sea, photographed by D. Golani; B), SAIAB 82139, Mozambique, southwestern Indian Ocean (21 ° 35 ' S, 35 ° 32.3 ' E), photographed by O. Alvheim.

FIGURE 2. Polysteganus coeruleopunctatus (A) and P. lineopunctatus (B). A), ZMB 7958, lectotype, 258 mm SL, [Kosseir] Al-Qusair, Red Sea B) BMNH 1903.2. 6.5, holotype, 320 mm SL, KwaZulu-Natal, South Africa, southwestern Indian Ocean, photographed by J. Maclaine.

FIGURE 4. P. c e r a s i nu s n. sp. SAIAB 84183, 134 mm SL, Saya de Malha Bank (10 ° 54.75 ' S, 60 ° 58.17 ' E), Mascarene Plateau, Indian Ocean, depth 127 m, photographed by O. Alvheim.