Sillago (Sillago) indica McKay, Dutt & Sujatha 1985

Sillago (Sillago) indica McKay, Dutt & Sujatha, 1985

Figs. 1, 2, 3, Tables 1, 2

[English name: Indian sillago]

Sillago parvisquamis (non Gill 1861): Dutt & Sujatha, 1980: 372.

Sillago (Parasillago) indica McKay, Dutt & Sujatha in McKay 1985: 38 (Holotype: ZSI: uncatalog, India). McKay, 1992: 45 (description).

Material examined. Paratypes: BMNH 1985.8.13.1 (159.4 mm SL), QM I20386 (141.0 mm SL), MNHN 1985–0799 (126.5 mm SL), Visakhapatnam, India, collected by K. Sujatha, June 8, 1979. Additional specimens: NMMB-P13995 (2 specimens, 173.4–174.2 mm SL), Phant Thiet, Vietnam, April 14, 2011.

Diagnosis. A species of subgenus Sillago (Sillago) with 34 total vertebrae, a dark black band on midline of body, and eight or nine lateral processes spanning entire lateral side of main body of swimbladder.

Description. Counts and measurements are given in Table 1. Description is based on three paratypes and two additional specimens.

Body fusiform, slightly compressed; depth at the first dorsal-fin origin usually deepest (except a specimen possessing depressed abdomen), deepest depth 5.3–5.5 in SL. Caudal peduncle deep, depth 2.5–3.0 in body depth. Head large, length 3.3–3.5 in SL. Snout very long, length 1.9–2.5 times eye diameter. Eye moderate, its margin covered with adipose eyelid, diameter 4.9–5.9 in HL. Interorbital region flat. Nostrils situated anterior to upper margin of eye; anterior nostril tubular with flap anteriorly, posterior nostril lacking flap. Mouth small, terminal, opening slightly oblique. Upper jaw with small canines forming tooth band, becoming narrower posteriorly. Lower jaw with small canines, forming tooth band anteriorly, width same as upper jaw tooth band, tooth band gradually becoming narrower posteriorly, terminating in one row. Palatine and tongue toothless. Vomer with two to three rows of canine teeth. Two large slit-like sensory pores open onto tip of snout, just above upper lip. Posterior margin of preopercle slightly serrated. Opercle with single weak spine posterodorsally. Body scales deciduous, size moderate, ctenoid except for those on prenasal area, which are cycloid. Cheek scales deciduous, cycloid, arranged in about two rows. Lower part of preoperculomandibular canal covered with cycloid scales, upper part covered with ctenoid scales. Gill rakers on first arch pointed, with small irregular spines; two tooth plates on hypobranchial portion of arch.

First and second dorsal fin short; longest spine 5.3–6.1 in SL. Dorsal fins narrowly separated. Anal-fin origin just below second dorsal-fin origin. Pectoral fin moderate in length 5.9–6.6 in SL; its tip reaching to below sixth to eighth dorsal spine. Pelvic fin shorter than pectoral fin, length 6.2–7.4 in SL; first soft ray elongated. Caudal fin emarginate.

Swimbladder large, with two posterior extensions extending into haemal funnel beyond posterior end of body cavity; two anterior extensions extending forward to basioccipital on both sides above auditory capsule. A single duct-like process originating from ventral surface of swimbladder and reaching urogenital opening. An anterolateral extension present on each side of swimbladder, branching into anterior and posterior subextensions: anterior one comprising a short, simple blind tubule; posterior one kinky, situated along abdominal wall and reaching just posterior to duct-like process of swimbladder. Eight or nine lateral processes extending from entire lateral surface of main body of swimbladder, anterior three stout and horn-like, posterior five or six rather small and triangular in shape.

Color when fresh (based on two non-type specimens, Fig. 2). Body and head silvery overall, dorsal and abdominal portions separated by dark black band. Upper part of snout blackish and lower part yellowish, parietal blackish, cheek and opercle with fine black dots. Dorsal-fin membranes dusted with black dots. Pectoral fin yellowish, no blotches on base. Anal fin yellowish, interradial membranes dusted with black dots. Caudal fin yellowish, posterior margin blackish and lower lobe densely black.

Color in alcohol. In non-types, body and head yellowish brown overall, greenish grey dorsally grading to white ventrally, dorsal and abdominal portions separated by a dark black band. Snout and parietal light brown, lower half of opercle silver with fine black dots, and cheek white with fine black dots. Dorsal-and anal-fin membranes dusted with black dots. Posterior margin of caudal fin blackish and lower lobe densely blackish.

In paratype (Fig. 1), body and head dark brown overall, no dark black band on midline of body. Abdomen with fine black dots. Snout dark gray, lower half of opercle blackish, and cheek with fine black dots. Dorsal-and analfin membranes dusted with black dots. Lower lobe of caudal fin dark gray. Over time in preservation coloration may become uniform dark brown, and black band on midline of body disappears.

Distribution. Known from the east and west coasts of India (McKay 1992), and now Vietnam.

TABLE 2. Comparison of Sillago (Sillago) indica and five species of the subgenus Sillago. S. (S.) S. (S.) S. (S.) S. (S.) S. (S.) S. (S.) sihama a, b, e

indica a caudicula b intermedius b, c, e megacephalus d, e parvisquamis a, b, e

Number of examined 5, 4, 5, 81.0–152.7 – 4, 219.1–258.4 9, 92.2–187.4 specimens and SL (mm) 126.5–17 101.1–148.

4.2 6

Vertebrae (in total) 34 35–36 34 no data 39–40 34 Dorsal fin rays XI–XII–I, XI–I, XI–I, 21–22 XI –I, 22 XII –XIII–I, 20–22 XI –I, 20–23

21–22 22–23

Soft anal fin rays 21–23 23–24 21–22 23 22–24 21–23 HL/SL (%) 28.2–30.1 29.0–30.1 29.1–31.3 33.0 25.9–27.7 27.7–29.9