Polysteganus cerasinus, Iwatsuki, Yukio & Heemstra, Phillip C., 2015

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 : 144-146

Polysteganus cerasinus new species

Proposed English name: Cherry Seabream Figure 4 ; Table 2

Holotype. SAIAB 84183, 134 mm SL (X), sex not determined, Saya de Malha Bank, Mascarene Plateau (19.10°54.75'S, 60°58.17'E), depth 127 m, Trawl No. Mascarene-19, coll. by D. Tweddle & O. Alvheim, 30 October 2008.

Diagnosis. Distinguished from all congeners of Polysteganus by the following combination of characters: scale rows above lateral line 6½; scales rows between 5th dorsal-fin spine base and lateral line 4½; lower counts of pored lateral-line scales 49; suborbital depth clearly less than orbit diameter (OD), 60% OD; no lines of blue spots on body; dorsal-fin rays reddish pink but yellowish membranes of both pinkish dorsal-fin and caudal-fin fin lobes, no whitish margin of lower margin of lower caudal fin lobe; no blue iridescence on body but bright whitish iridescence on each body scale of lateral side of bright pinkish body; body deep, 43% SL; no bony bulge before and above eye; pinkish upper and lower caudal-fin as well as rear pinkish margin of the caudal fin with yellowish hyaline membrane of most of caudal fin with no whitish upper and lower margins; rear margin of membrane of branchiostegal rays yellow, with yellow hue on some body scales just above upper pectoral-fin base ( Fig. 4 ); no bony bulge before and above eye; caudal fin moderately forked.

Description. Counts and proportional measurements as percent of standard length of the holotype of Polysteganus cerasinus n. sp. are given in Table 2 .

Body depth relatively deeper; head robust, rostro-occipital profile nearly straight; interorbital scaly, scales extend to nearly above anterior nostrils and just above posterior nostrils; anterior nostrils small and rounded, posterior nostrils oval; orbit diameter clearly greater than interorbital width; maxilla naked, its rear end nearly reaching vertical at front edge of eye when mouth closed, rear margin of maxilla not concealed by infraorbitals; jaws robust, especially upper jaw; canines short and small, 4 in upper and 6 in lower jaw (but not visible to naked eye; 2 outermost canines in upper jaw somewhat larger than 2 medial canines, and 2 outermost canines of lower jaw somewhat greater in size than 4 medial canines if seen through binocular microscope); an outer lateral row of conical teeth and a series of villiform teeth, on inner side of outer lateral teeth row; mandible straight; rear margin of preopercle rounded and minutely serrate; narrow naked area between preopercle flange scaly area and cheek scales; first to third dorsal-fin spines progressively longer, fourth dorsal-fin spine longest, and clearly greater than snout length; no sheath scales on dorsal and pelvic-fin rays; predorsal length clearly greater than body depth, and definitely less than dorsal-fin base length; lateral line gently curved, subequally parallel to curved dorsal profile between dorsal outline and curved lateral line; pectoral-fin base scaly and somewhat pointed posteriorly, 2 or 3 lowest rays slightly extended posteriorly, compared with rays above ( Fig. 2 B, visible in the holotype of this species if seen through binocular microscope), the fin tip reaching vertical at anal fin origin, its length subequal to head length; first pelvic-fin ray length definitely greater than fourth dorsal-fin spine length, fin tip not beyond vertical at pectoral-fin tip and not beyond rear margin of anus; soft dorsal- and anal-fins with no scales; anal fin with low scaly sheath, anal-fin spines slender, second subequal to third, clearly less than orbit diameter; caudal fin moderately forked; scales ctenoid; gill-rakers lanceolate; vertebrae 10+14.

Color when fresh, based on color photograph of the holotype (photographed by O. Alvheim; Fig. 4 ): head and body uniform pink with silvery reflection on each scale, color of upper part of head and dorsolateral part of body brighter pink than lower part of head and abdominal part of body; iris golden and pupil black; all fins uniform pinkish hyaline, especially in hyaline of membrane of pectoral fins; pinkish upper and lower caudal-fin as well as rear pinkish margin of the caudal fin with yellowish membrane of greater part of caudal fin with no whitish margin on lower margin of lower caudal fin lobe (central part of membrane and caudal-fin rays of caudal fin yellow and with pinkish margin); head and body uniform reddish orange with golden yellow reflection at center of each scale, color of dorsal head and dorsolateral part of body brighter than ventral part of head and abdominal part of body; iris golden and pupil black; all fins uniform reddish orange, but membrane of spinous dorsal-fin reddish orange.

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

Distribution. Polysteganus cerasinus n. sp. is currently known only from Saya de Malha Bank (19.10°54.75'S, 60°58.17'E), at a depth of 127 m. This species is presumably more likely to inhabit the somewhat shallower coastal waters around the Mascarene Islands than other Mascarene Polysteganus species: Polysteganus baissaci , P. flavodorsalis n. sp. and P. mascarenensis have all been trawled deeper than 200 m.

Etymology. This fish is named cerasinus , ‘of the cherry’, alluding to its cherry blossom colour. Remarks. Two other Mascarene species, P. flavodorsalis n. sp., and P. mascarenensis , were collected at depths of over 200 m (Iwatsuki & Heemstra 2011). Further biological information and additional collection data are urgently required for this species.

Figures

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.