Uranoscopus crassiceps Alcock, 1890

Fricke, Ronald, Jawad, Laith A., Al-Kharusi, Lubna H. & Al-Mamry, Juma M., 2013, New record and redescription of Uranoscopus crassiceps Alcock, 1890 (Uranoscopidae) from Oman, Arabian Sea, northwestern Indian Ocean, based on adult specimens, Cybium 37 (3), pp. 143-147 : 144-147

Uranoscopus crassiceps Alcock, 1890

( Fig. 1 A-E)

Uranoscopus crassiceps Alcock, 1890: 205-206

(off Madras coast, India, northeastern Indian Ocean, 18°30’N- 84°46’E, Investigator station 96, depth 98-102 fathoms). Alcock, 1894: Pl. 10, fig. 4. Norman, 1939: 71 (Gulf of Aden, St. 16, depth 186 m; St. 194, depth 220 m). Menon and Yazdani, 1968: 146 (type catalogue). Menon and Rama-Rao, 1970: 37 (type catalogue). Menon and Rama-Rao, 1975: 39 (type catalogue). Heemstra, 1984: 2 (Western Indian Ocean). Brüss, 1987a: 41, 44, 45. Brüss, 1987b: 53. Pietsch, 1989: 295 (Gulf of Aden to Bay of Bengal).

Material

Oman, northwestern Indian Ocean : OMMSFC 1086, one specimen, 270 mm SL, south of Masirah Island, 20°03’55.44’’N- 59°08’19.53’’E, 180 m depth. SMF 34725 , 3 specimens, 189-218 mm SL, vicinity of Salalah City , 16°18’17.98’’N- 54°34’59.61’’ E, 185 m depth .

India, northeastern Indian Ocean : MNHN 1890-0324 to 1890-0326 , 3 syntypes of Uranoscopus crassiceps Alcock, 1890 , 53–75 mm SL, Chennai [Madras] coast, 18°30’- 84°46’E, 98-102 fms depth [179-187 m], hard sand bottom, R / V Investigator St. 96, 4 Mar. 1890 .

Diagnosis

A medium-sized species of Uranoscopus with a large head (head length 2.7-2.9 in SL); lower edge of preopercle with 4-7 spines; labial fimbriae well-developed; both nostrils with short tubiform valve; dorsoposterior margin of pectoral-fin truncate; lower half of pectoral-fin and membranes of caudal-fin yellow in fresh specimens; 52-54 oblique scale-rows along the sides of the body in adults, 41-54 in juveniles and subadults.

Description of adults from Oman

Morphometric and meristic data are summarised in table I.

Dorsal-fin V + iii,11; anal-fin i,13; pectoral-fin i,17; pelvic-fin I,5; caudal-fin (iii),i,10,i,(iii).

Head large and anterior part of body broad, depressed, body tapering and becoming slightly compressed posteriorly. Body scales arranged in 52-54 oblique rows. Head, nape between lateral lines, breast and belly naked. Tubiform scales embedded along lateral line. Lateral line positioned dorsally, bending down on caudal peduncle to continue in an extension of the central two caudal-fin rays, extending along the basal one-third of those rays. Spines 1-4 in first dorsal fin well developed, connected by membranes; rudimentary 5 th element covered by skin. First element of second dorsal fin segmented and unbranched. Membranes of anal and paired fins fleshy and thickened. Pectoral fin broad, dorsoposterior margin truncate, remainder of distal margin convex, 7 th- 8 th rays longest. Soft dorsal and anal-fin bases long, height of soft dorsal-fin 2.5-2.7 in second dorsal-fin base length, height of anal fin 4.4-4.7 in anal-fin base length. Caudal fin distally convex. Pelvic fins situated on isthmus; distance between pelvic fins about one pelvic-fin base length ( Fig. 1D ). Pelvic spine feeble, closely connected to 1 st soft-ray by tendon. Maximum observed SL 270 mm.

Head flattened dorsolaterally, dorsal and lateral surfaces almost entirely encased in minutely sculptured bones ( Fig. 1C ). External apparent bones of head slightly concave along mid-dorsal line. Single pair of basipterygial processes widely separated ( Fig. 1D ). Joints of head bone elements marked by deep channels. Post-interorbital knobs absent. Two occipital lobes developed. Preopercular limb not joined 46). This author reported 41–54 oblique lateral scale rows with opercle. Eye large, positioned dorsally, slightly tel- in subadults, compared to 52-54 in adults from Oman; the escopic, without membranous tentacle or grainy row. Inter- number of lateral scale rows obviously tends to increase with orbital fossa semicircular, longer than broad, including pos- age. The head is slightly smaller (2.7-2.9 in SL) compared to terior half of interorbital space, reaching to level of posterior the proportion observed by Brüss (36.5-39.5% of SL, equal- margin of orbit ( Fig. 1C ). Nasal bone weakly ossified, not ling 2.6-2.7 in SL), and the pelvic fin slightly longer (4.2- exposed, covered by skin of snout. Frontal bones not form- 4.6 in SL, compared to 4.5-5.2 observed by Brüss). The head ing a supraorbital tubercule. Both nostrils with short tubi- bones and spines agree with those of the specimens illusform valve. No chin barbel or cirri on branchiostegal mem- trated by Brüss (1987a: figs. 5-6). Previous authors includ- brane. Prelingual filament reduced to a triangular velum. ing Alcock (1890) and Brüss (1987a), have missed the 5 th Opercle distinctly shorter than deep; subopercle without spine of the first dorsal fin, which is embedded in the skin ventral thickening, not overlapping opercle. Preopercle and barely visible.

without a horizontal, ventrolateral thickening. Preopercular Uranoscopus crassiceps is distinguished from U. gutlimb not joined with opercle. Lower edge of preopercle with tatus which has a similar body colouration of dorsal white 4-7 spines ( Fig. 1B ). Respiratory valve rudimentary. Dentary spots and purple-brown sides (southern Red Sea and eastwithout a ventromedial flange. Teeth in jaws small, conical, ern India), by the wider head (head width 1.07-1.10 in head in two series; one series of widely separated caniniform teeth length, compared with approximately 1.4 in U. guttatus ), on premaxillary and dentary; labial fimbriae well-developed the absence of post-interorbital knobs (present in U. gut- (14-16 on upper lip, 22-26 on lower lip) ( Fig. 1E ). tatus), and 41-54 lateral scale rows (55 in U. guttatus ). It Colour in life (see Fig. 1A ). - Dorsal parts of head and differs from U. archionema (East Africa) in its smaller eye body dark brown, back with irregular large whitish blotches. (orbit diameter 5.4-6.8 in head length, compared to 4.0-5.0 Sides of head and body brownish violet. Belly, thorax and in U. archionema ), a smaller interorbital width (interorbital pectoral-fin base white. Eye dorsally dark brown, laterally width in orbit diameter 0.59-0.75, compared to 0.9-1.0 in yellowish green. First dorsal fin black, base of first and sec- U. archionema ), the pectoral-fin colouration (dorsal half ond spines reddish brown, fourth membrane white. Rays gray, and ventral half greenish-yellow, compared to plain of second dorsal and anal fins greenish brown, membranes gray with a distal pale margin in U. archionema ), and the translucent. Caudal fin rays dark brown, membranes in lower caudal-fin colouration (dorsally gray, ventrally pale or yel- half greenish yellow, membranes in dorsal half dusky. Upper half of pectoral fin Table I. - Morphometric and meristic data of Uranoscopus crassiceps from Oman (4 greyish brown, lower half greenish yel- specimens measured).

low. Pelvic fin whitish rose, first to third Proportion Range rays distally mottled with dark brown, Head length in SL 2.7-2.9 fifth ray greenish yellow. Head width in SL 2.9-3.2 Colour in preservative (see Fig. 1C ). Head width in HL 1.1

- Head and body dorsally dark brown, lat- Length between snout and gill opening in SL 3.4-3.8 erally brown, ventrally light brown. White Length of longest anal-fin soft-ray in SL 7.2-10.7 blotches on the back still discernible. Yel- Pelvic-fin length in SL 4.2-4.6 lowish, green and violet shades no longer Length of postorbital part of head in HL 1.2-1.4 visible. Orbit diameter in HL 5.4-6.8

Upper jaw length in HL 2.2-2.4 Distribution

Caudal peduncle depth in HL 3.3-4.6 Northwestern and northeastern Indian

Caudal-fin length in HL 1.4-1.7 Ocean: Somalia (Gulf of Aden), Yemen

Cleithral-spine length in HL 4.3-7.2 (Gulf of Aden); Oman (Arabian Sea);

Distance between basipterygial processes in HL 4.5-6.3 India (Coromandel coast, Ganjam coast,

Opercular width in HL 2.6-3.7 Chennai coast). Found on soft bottoms of

Interorbital width in orbit diameter 0.6-0.8 lower continental shelf; depth range rela-

Length of interorbital fossa in orbit diameter 1.0-1.2 tively narrow, 179-220 m.

Orbit diameter in width of interorbital fossa 0.6-0.9 Remarks Greatest infraorbital depth in orbit diameter 0.8-1.0 The counts and measurements agree Length of basipterygial process in distance between basipterygial processes 1.0-1.3 with those of a range of larger subadult Longest dorsal soft-ray length in longest anal soft-ray length 0.7-0.8 specimens described by Brüss (1987a: Pectoral-fin length in cleithral-spine length 0.2-0.4 lowish, compared to plain gray in U. archionema ). It is distinguished from U. marisrubri (Red Sea) (see Brüss, 1987a: 46) by its smaller head (head length 2.6-2.9 in SL, compared to 2.4-2.6 in U. marisrubri ), preorbital lower (preorbital depth 18-22 in SL, compared to 10-20 in U. marisrubri ), humeral spine usually longer (humeral-spine length 9-14 in SL, compared to 9-10 in U. marisrubri ), a longer pelvic fin (pelvic-fin length 4.3-4.6 in SL, compared to 4.6-5.3 in U. marisrubri ), more lateral scale rows (41-43 in juveniles, 52-54 in adults, compared to 38 in juveniles and 50 in adults in U. marisrubri ), and usually more preopercular spines (5-7, rarely 4 in U. crassiceps , 4 in U. marisrubri ).

Uranoscopus crassiceps is apparently widely distributed along the lower edge of the continental shelf of the northern Indian Ocean, from the Gulf of Aden ( Somalia, Yemen) to off Chennai, India. The Bab-el-Mandeb with a maximum depth of 310 m apparently forms an effective barrier preventing the dispersal of this species, though depth is not the ecological factor producing that barrier. Salinity and/or a competitive Uranoscopus species like U. dahlakensis or U. marisrubri are probably more relevant factors. Further along the African coast ( Kenya southward), Uranoscopus crassiceps is replaced by the similar species U. archionema , which occupies a wider depth range of 60- 300 m. The Persian/Arabian Gulf (maximum depth 90 m) is too shallow to be inhabited by Uranoscopus crassiceps .

The geographic distribution of Uranoscopus crassiceps , as revealed by the specimens from southern Oman, covers the area of cold upwelling in southern Arabia, as well as the regions towards the west and the east. While the upwelling zone provides an effective barrier for the dispersal of many shallow water fish species, the lower edge of the continental shelf is apparently less affected, and water temperatures at a depth around 180-200 m differ little from the surrounding continental shelf regions. Consequently, the upwelling barrier is not effective at that depth.

Considering the known distribution range of Uranoscopus crassiceps , it is expected to occur also along the lower continental shelf of southern Iran, Pakistan, and along the western (Arabian Sea) coast of India, and possibly also around Sri Lanka. As a continental species, probably requiring nutrient-rich soft bottom habitats, it is unlikely to occur around offshore islands like the Laccadives or Maldives.

Acknowledgements. – We would like to thank the Ministry of Fisheries Wealth, Marine Science and Fisheries Centre, and the Directorate of Agriculture and Fisheries Developmental Fund for giving us the opportunity to work on the fish samples to examine the qualitative and quantitative distribution of marine organisms in Sultanate of Oman and providing the appropriate financial support. We also thank Tilman Alpermann (SMF, Frankfurt am Main) for curating uranoscopid material, and Oliver Crimmen (BMNH, London), Martine Desoutter and Jean-Claude Hureau (MNHN, Paris) for the permission to examine material in their care. We are grateful to Clea Fricke (Université Aix-Marseille III, Aix-en-Provence) for the French translation of the abstract.

Figures

Figure 1. - Uranoscopus crassiceps, OMMSFC 1086, 270 mm SL, Oman. A: Lateral view; B: Lateral view of head; C: Dorsal view of head; D: Ventral view of head; E: Anterior view of head.