Siphamia mossambica Smith

Gon, Ofer & Allen, Gerald R., 2012, 3294, Zootaxa 3294, pp. 1-84 : 54-55

Siphamia mossambica Smith

Figures 26, 28a

Siphamia mossambica Smith, 1955: 63 , pl. 1 (type locality, Bazaruto Island , Mozambique; holotype, SAIAB 345 ).

Siphamia nigra Fourmanoir and Crosnier, 1964: 7 , fig. 4 (type locality, Ambatoloaka , Nosy-Bé, Madagascar; syntypes, MNHN 1973-0043 ).

Diagnosis: Dorsal rays VII+I,9; anal rays II,8; pectoral rays 14–16; tubed lateral-line scales 7–12; median predorsal scales 3–5; total gill rakers 3–4 + 9–10; developed gill rakers 1 + 8; gill rakers on ceratobranchial 6–7. Body depth 2.4–2.65 in SL and body width 1.7–2.2 in the depth; eye diameter 2.7–3.1 in head length; first dorsal spine 2.4–4.5 in second spine; second dorsal spine 3.9–4.95, spine of second dorsal fin 4.3–5.2, and second anal spine 5.7–7.0, all in head length; pectoral-fin length 4.3–5.0 and pelvic-fin length 4.0– 4.8 in SL; caudal-peduncle length 1.4–2.0 in distance between pelvic spine insertion and anal-fin origin. Preopercular edge with 0–19 (usually 5–12) serrations around angle; preopercular ridge smooth. Scales weakly spinoid to cycloid. Vomer and palatines with 1–2 series of small conical teeth. Tip of light organ on each side of tongue bound by membrane.

Colour in life (from underwater photo by Dennis King): body brown with purplish tinge, similar to the colour of the spines of the sea urchin in which the fish live; fins transparent with reddish tinge.

Colour when fresh (from colour slide by J.E. Randall): translucent with purplish tinge and mostly large dark dots on body and head; orange-brown dots present on iris; fin spines and rays with dark pigment basally, and orange-brown dots along their margin; light organ silvery with dark vertical or slanted striations.

Colour in alcohol: variable; body usually brown with dark brown to blackish dots that may form 1–3 dark stripes; all fins usually with dark dots or diffuse dark pigment proximally; first dorsal fin spines sometimes with dark dots along most of their length; anus sometimes dark; peritoneum with dark dots of various sizes; intestine and stomach with smaller dark dots.

Smallest specimen examined, USNM 349778, 11.5 mm, from Mauritius and largest specimen, WAM P.26460- 006, 33.6 mm, from Oman.

Remarks: See Tables 1–3 for frequency distributions of pectoral rays, lateral-line scales and gill rakers. Small fish (17.0 mm or smaller) usually have a subcutaneous dark dot at the base of each second dorsal- and anal-fin ray. These dots are responsible for the dark colour at the base of these fins when expanded in larger specimens. In a 12.2 mm specimen the light organ ended at about the middle of the caudal peduncle and in a 17.0 mm fish it had reached its final position over the base of the anterior procurrent caudal rays. The holotype of this species (SAIAB 345) is in poor condition, and seems to have been at least partially desiccated in the past. Fins, jaws and the top of the head are damaged, scales are glued to the skin and the opercular bones are falling apart. The left side of the fish has seven tubed lateral-line scales present and clear impressions of five additional ones indicating a total of 12.

This species is a member of the S. tubifer species group. It resembles S. fraseri from the south Pacific and S. arabica from the Gulf of Oman with which it shares a similar range of tubed lateral-line scales ( Table 2) and colour pattern. However, S. fraseri differs from S. mossambica in having 10–11 developed gill rakers ( Table 3). Siphamia arabica shows a very small overlap with S. mossambica in the total number of developed gill rakers and these two species are modally different in the number of gill rakers on the ceratobranchial ( Table 3). In addition, S. arabica has a shorter caudal fin (3.95–4.3 in SL), higher spiny dorsal fin (third and longest dorsal-fin spine 2.0– 2.5 in head length) and a longer pelvic-fin spine (1.4–1.7 in pelvic fin length). Siphamia tubifer , which may co-occur with this species in the northern part of the western Indian Ocean, also has a similar colour pattern and a similar number of developed gill rakers ( Table 3). However, S. tubifer has more lateral-line scales ( Table 2) and generally a longer pelvic-fin spine (1.3–1.7 in pelvic-fin length versus 1.7–1.9 in S. mossambica ). S. mossambica also has a similar colour pattern to S. majimai and S. goreni . Siphamia majimai has six spines in the first dorsal fin. See Remarks for S. goreni above for a comparison with this species.

Smith (1955, 1961) described the live colour of the holotype of this species as translucent with dark specks forming rows along the body, and pale fins. His paratype (SAIAB 785), a smaller specimen, had “only faint indications” of these dark spots making Smith uncertain that the two were conspecific. Smith, who was not a diver, did not see this species in its natural environment and he did not realize that it can change colours rapidly when threatened or following death. See also Remarks for the genus Siphamia above.

Siphamia mossambica is endemic to the western Indian Ocean. It has been collected along the east coast of Africa from Kenya to South Africa, Seychelles, Comoro Islands, Madagascar and Mauritius ( Fig. 7), at depths of 5– 26 m. Collection data indicate it is generally associated with the sea urchins Echinotrix diadema and Diadema setosum .

Material examined: KENYA: Mombasa, USNM 374487 , 2 : 19.8–23.3 mm. Shimoni , SAIAB 785 , 18.3 mm (paratype) . MOZAMBIQUE: Bazaruto , SAIAB 345 , 20.6 mm (holotype). Ponta Mamoli , SAIAB 46527 , 6 : 18.0– 32.5 mm. Ponta Malongane , SAIAB 50560 , 26.1 mm . SOUTH AFRICA: KwaZulu-Natal, Sodwana Bay , ROM 72903, 20.3 mm ; ROM 72805, 12.2 mm ; ROM 72913, 15.4 mm ; SAIAB 64586 , 29.2 mm . OMAN: ROM 44189, 6 : 17.1–27.9 mm. Near Mirbat , BPBM 34422 , 6 : 19.1–28.7 mm. Sawda Island , BPBM 36026 , 2 : 9.2–15.7 mm . SEYCHELLES: Aride Islands , BPBM 35465 , 18.5 mm. Curieuse Island , ANSP 152471 , 4 : 15.1–25.1 mm. Faon Island , ANSP 152442 , 2 : 19.6–19.8 mm . COMORO ISLANDS: Mayotte , ROM 59346, 17.0 mm ; ROM 59348, 33 :0 14.0–26.0 mm . MADAGASCAR: Nosy Bé , AMS I.28107-038, 16.1 mm; AMS I.28113-021, 2: 15.1–22.6 mm; MNHN 1973-0043 , 2 : 16.1–19.2 mm (syntypes of Siphamia nigra ) ; USNM 307709 , 15.9 mm . MAURITIUS: Flic en Flac , USNM 349780 , 14 : 12.5–21.5 mm. Baie de la Petite Riviere , USNM 349777 , 8 : 14.4–21.3 mm. Pointe Aux Cave Light House , USNM 349778 , 18 : 11.5–21.7 mm. West of Baie du Cap , USNM 308002 , 5 : 14.6–22.4 mm. Passe De L'Ambulante , USNM 349781 , 2 : 13.1–13.7 mm. Rodrigues Island , SAIAB 65535 , 2 : 17.0– 25.4 mm .