Pleurosicya mossambica Smith 1959

Pleurosicya mossambica Smith, 1959 Mozambique Ghostgoby

Figures 3–6, Table 3

Pleurosicya mossambica Smith, 1959: 218, Fig. 37 (type locality: Pinda, Mozambique; holotype: SAIAB 227)— Goren 1984: 72, Figs. 1a–c (Marsa Barecha, southern Sinai Peninsula); Larson 1990: 32 (types of P. sinaia); Golani & Bogorodsky 2010: 48 (listed); Debelius 2011: 185 (Dahlak, Eritrea); Fricke et al. 2015: 217, Figs. 1–3 (Israel); Akel & Karachle 2017: 19, Table 2 (Egypt); Golani & Fricke 2018: 159 (listed).

Pleurosicya micheli (non Fourmanoir)— Herler & Hilgers 2005: 125, Fig. 17A–C; Herler et al. 2009: 732, Figs. 3 & 4 (Eritrea); Golani & Bogorodsky 2010: 48 (listed); Debelius 2011: 185 (Safaga, Egypt); Golani & Fricke 2018: 159 (listed).

Pleurosicya sinaia Goren, 1984: 74, Figs. 2a–c (Marsa Barecha, southerm Sinai Peninsula and south of Eilat, Israel)— Akel & Karachle 2017: 19, Table 2 (Egypt).

Distinctive characters (based on the specimens listed below). Pectoral-fin rays 16–19 (usually 17); midline of nape naked, scales on side of nape extending forward nearly to eye; gill opening broad, extending forward to or beyond a vertical at posterior edge of eye; tip of tongue rounded; head and body with brownish red stripe ending on caudalfin base and series of alternating brown and white dashes along vertebral column; nape with U-shaped mark; often a diffuse black band on basal half of first dorsal fin.

Description (based on examined material). A small fish, standard length usually less than 25 mm. Body elongate and compressed. Mouth terminal. Maxilla extending posteriorly to below anterior margin of eye pupil. Lips thick. Upper and lower jaws with bands of pointed teeth. In upper jaw, outermost 4–6 pairs enlarged, curved backward and visible when mouth is closed. Inner teeth of lower jaw enlarged, two pairs canine-shaped. Tip of tongue rounded. Vomer with a considerable protuberance. Gill opening broad, extending forward to below posterior margin of eye or little beyond. Gill rakers short, 1+1+5.

Fins: Dorsal-fin rays VI + I,7–8; anal-fin rays I,7–8; pectoral-fin rays 16–17; pelvic-fin rays I,5. First dorsal fin height is equal to about three-fourths of body depth. Second dorsal fin inserts above anus, its height is equal to body depth (Fig. 3). Pelvic fins fully united, do not reach anus. The fin cup-shaped, with fleshy lobes at each side of the frenum. Pelvic frenum well developed, folded anteriorly to form pocket.

Vertebrae count: 25–26. Dorsal pterygiophore formula: 3-221100.

Scales: 23–26 ctenoid scales in longitudinal series along the body, 7 transverse rows. Mid predorsal area naked, side of nape scaled, scales nearly reaching to eye.

Selected meristic characteristics and proportions presented in Table 3.

Cephalic sensory pore system: Anterior nostrils a short tube, closer to upper lip than to eye. Posterior nostrils at midway between eye and upper lip. Anterior interorbital pore above mid eyes. Posterior interorbital pore above posterior margins of eyes, opens backward. Pairs of supraotic and anteriotic pores behind eyes.A pair of intertemporal pores above preopercle. Three preopercular pores (Fig. 4).

Colour (alive, Fig. 5, based on original observation). Body translucent gray, with red to brownish red stripe extending from upper lip and continuing behind eye along body, ending on midbase of caudal fin. A longitudinal series of internal short white dashes alternating with longer brown ones visible along vertebral column. Brown dashes much longer than white dashes on anterior half of body. Series of dashes and body stripe separated by a whitish interspace on anterior half of body, meeting below interdorsal space. Side of abdomen within the stripe usually covered with melanophores; nape with red U-shaped mark; iris brownish orange, dorsal half densely pigmented, inner ring white; fins translucent; some individuals with a series of melanophores forming a diffuse blackish band basally in first dorsal fin, more heavily pigmented centrally.

Colour (preserved): Body and head yellowish. Patches of small black dots of lower part of the membrane of first dorsal fin.

Distribution and Habitat. Ranges from the Red Sea south to Mozambique, South Africa, Madagascar, and Mauritius, east to Chagos Archipelago and Maldives. Found on coral reefs and adjacent habitats, at depths of 2– 28 m. Commensal on a wide variety of sessile animals, mainly on soft corals of the family Nephtheidae (usually Litophyton arboreum Forsskål, 1775), on massive-growing stony corals of the genera Platygyra, Porites and Echinopora, and sponges (Larson 1990; Herler & Hilgers 2005; present study).

Remarks. The present comparison between the Red Sea and western Indian Ocean populations of P. mossambica (including P. sinaia) does not support dividing them into different species despite small differences in mouth width (Fricke et al. 2015), a small but clear genetic divergence (see more details in the molecular results), and minor differences in coloration. Red Sea specimens are either without pigment in the first dorsal fin or have a diffuse black band present on basal part of the fin whereas specimens from the south-western Indian Ocean always have1–4irregular black spots on basal part of the fin (Smith 1959; Fig. 6A–C). Larson (1990) examined specimens from a broad range, from South Africa to Fiji, but did not provide data separately for specimens from the western Indian and western Pacific Oceans. She noted that the species has variable scale patterns on the nape, from unscaled to partly or fully scaled. Specimens of P. mossambica from the Western Indian Ocean (including holotype) and Red Sea are characterised by an absence of scales on the midline of the nape. More specimens from both areas are needed for further comparative analysis including genetic data. Specimens identified as P. mossambica from the western Pacific (Great Barrier Reef) are divergent genetically (Fig. 1), hence the population from the western Pacific is assigned preliminary to an undescribed species. A specimen from Palau (ROM 74851, Fig. 6D) is similar in coloration but additional study is needed to conclude whether specimens from Australia and Palau are conspecific.

Herler & Hilgers (2005), who reported the presence of P. micheli in the Red Sea, distinguished P. micheli from P. mossambica by the intensity of pigmentation on first dorsal fin and lower part of trunk, and by their different habitats. They claimed that P. micheli inhabits “massive growing stony corals” while P. mossambica mostly inhabits soft corals. As evident from a series of images (Fig. 5), the type of host is not relevant in the case of P. mossambica. This species has been found in association with various species of both hard and soft corals as well as with sponges. Pleurosicya micheli is very similar to P. mossambica morphologically but differs in details of colouration (based on photos, Fig. 7). The body stripe is directly below a series of alternating long white and short brown-red dashes or an interrupted white line along the vertebral column on the anterior half of the body in P. micheli whereas a series of alternating long brown and short white dashes is separated by a whitish interspace from the body stripe on the anterior half of the body in P. mossambica. In addition, a body stripe extending into basal half of the lower caudalfin lobe is present in P. micheli but the stripe ends on the caudal-fin base in P. mossambica. The iris is red-orange and its dorsal surface black in P. micheli versus iris brownish orange and dorsal half densely pigmented with black dots in P. mossambica. Pleurosicya micheli is known from Indonesia to French Polynesia (Larson 1990) and records from the Indian Ocean are based on misidentification. Randall (1995) reported P. micheli from Oman but illustrated an individual photographed from Papua New Guinea. Coloration of two specimens reproduced in Herler & Hilgers (2005) match color description of P. mossambica, therefore P. micheli is excluded from the fauna of the Red Sea.

Material examined: Israel: SMNH-P 6414 (paratype of P. sinaia), 16.8 mm SL, Eilat (Gulf of Aqaba), 29.503313°N, 34.911932°E, 01 October 1976; SMNH-P 9972, 11.7 mm SL, Eilat (Gulf of Aqaba), 29.503313°N, 34.911932°E, 16 July 1988; SMNH-P 10377, 19.8 mm SL, Eilat (Gulf of Aqaba), 29.503313°N, 34.911932°E, 01 November 1992; SMNH-P 15251 (first identified and reported in BOLD as P. micheli), 16.4 mm SL, Eilat (Gulf of Aqaba), 29.503313°N, 34.911932°E, 18 March 2012. Egypt: SMNH-P 6415 (holotype of P. sinaia), Marsa Bareika (southern Sinai Peninsula), 17.7 mm SL, 17.789137°N, 34.218273°E, 16 October 1979; SMNH-P 9017, 2 spec., 17.7 mm SL & 16.0 mm SL, Marsa Bareika (southern Sinai Peninsula), 17.789137°N, 34.218273°E, 01 March 1979. Mauritius: SAIAB 57883, 3 spec., 15.1–17.9 mm SL, Flic en Flac 30m N of Pass, 20.2666664124°S, 57.3666648865°E, 05 May 1995. Seychelles: SAIAB 76388, 3 spec., 14.1–18.7 mm SL, Baie Ternay-center, 04.3831°S, 55.2241°E, 08 May 2005; SAIAB 79084, 16.6 mm SL, Tie Therese, SE side, 04.4048°S, 55.2441°E, 29 April 2005; SAIAB 79325, 19.8 mm SL, south of Pointe L’Escalier (S of Port Launay, at L’Embarcadere), 4.6611°S, 55.397°E, 22April 2005. Mozambique: SAIAB 5438, 16.7 mm SL, Pinda Island, 14.21666622°S, 40.7666664124°E, 23 September 1950; SAIAB 50419, 25.1 mm SL, Penta Malongane, 26.76666641°S, 32.9000015259°E, 04 April 1995; SAIAB 5439, 3 spec., 17.2–19.8 mm SL, Pinda Island, 14.21666622°S, 40.7666664124°E, 07 September 1956; SAIAB 5440, 17.4 mm SL, Pinda Island Reef, 14.21666622°S, 40.7666664124°E, 21 September 1956. South Africa: SAIAB 61190, 14.9 mm SL, Aliwal Shoal, 30.25°S, 30.8166675568°E, 25 November 1999.