Pseudochromis leucorhynchus Lubbock

White-nosed Dottyback

Figure 6; Table 3

Pseudochromis leucorhynchus Lubbock, 1977: 6, pls 2b and 3b (type locality: Shela, Lamu Island, Kenya); Gill, 2004: 128, tab. 8, fig. 33, pl. 8F (description, synonymy, distribution, colour photo).

Pseudochromis leucorhynchus was originally described from 11 specimens from Kenya by Lubbock (1977). Gill and Mee (1993) recorded two specimens of the species from southern Oman, but noted that the Omani specimens tended to have more segmented anal-fin rays, more anterior lateral-line scales, more scales in lateral series, and fewer scales between lateral lines than those from Kenya. These differences were confirmed by Gill (2004: table 8) based on six additional specimens from southern Oman. He noted “the possibility that this variation is worthy of separate species status must await the analysis of specimens from intermediate areas” (Gill 2004: 130). We record the species from the Socotra Archipelago on the basis of 20 specimens from the west and south coasts of Socotra Island. With the exception of one character (scales between lateral lines), counts for the specimens are intermediate between the Omani specimens to the north and the Kenyan specimens to the south (Table 3), and we therefore argue for the continued recognition of a single species.

Pseudochromis leucorhynchus was also visually recorded from around the entire Socotra Island coast and also once each from the north coast of Abd al-Kuri Island and the north-east coast of Semha Island. It was recently recorded again from the west coast (Ras Bidou) and south coast (off Steroh village) of Socotra Island (H. Pulch and T. Alpermann, pers. comm.). The species thus occurs thoughout the entire island group, with a relatively wide ecological niche ranging from filter feeder communities on highly dynamic bedrock and relict spur and groove habitat, over mixed macroalgae-dominated communities on rock platform with sparse hard corals of the south coast (for which it appears to have a preference on Socotra), to occasionally massive coral communities (Porites, Galaxea) and diverse coral biotopes dominated by branching species (staghorn Acropora). It was found at a depth range of 2– 16 m.

Gill and Mee (1993) noted that P. leucorhynchus closely resembles the omobranchin blenniid Oman ypsilon Springer in live coloration, and suggested that the two may be involved in a mimetic relationship. The latter species is unknown from Kenya, but we newly record it from the Socotra Archipelago on the basis of an individual observed (but not collected) inside a Diadema urchin in 6–7 m at Di Hamri, Socotra, by the second author on 15 April 2007.

Material examined. SMF 29212, 2: 44.5–51.9 mm SL, Socotra Archipelago, W coast of Socotra Island, Shuab Bay, Ras Asfar, 12°39’24”N 53°24’07” E, bedrock with encrusting corals and filter feeders in front of cliff (biotope code S4.2.3), 8–10 m, U. Zajonz & M. Apel, 9 March 1999 (ST-017); SMF 29213, 10: 27.0– 61.6 mm SL, Socotra Archipelago, S coast of Socotra island, E of Ras Qatanin, 150 m off the coast at position of the stranded ship wreck, 12°20’03”N 53°34”26”E, 2–4 m, U. Zajonz & M. Khalaf, 13 March 1999 (ST-024); SMF 29233, 8: 15.3–58.6 mm SL, Socotra Archipelago, SW coast of Socotra Island, Ras Qatanin Bay, 12o21'17"N 53o32'39"E, collected at large boulder (biotope code S5.1.5), 8–11 m, U. Zajonz & F.N. Saeed, 9 April 2000 (ST-726).