Redescription of the ocellus-bearing cuskeel Neobythites kenyaensis (Ophidiidae), with new Southeast African records and remarks on intraspecifíc morphological and colour variation

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Neobythites kenyaensis, a cuskeel (Ophidiidae) with two ocelli on the dorsal fin, is redescribed based on 33 meristic, body shape, colour, and otolith characters obtained from 15 specimens, 12 of which were studied for the first time. Nine of the 12 new specimens were collected during a research cruise off Mozambique together with vouchered colour photographs made on board when the fish were still fresh. Two specimens were collected off Natal, South Africa, one of them only available as a fresh colour photograph and one specimen off Dar es Salaam, Tanzania. Accordingly, while M kenyaensis was only known from Kenya and northernmost Tanzania (Zanzibar) since its description in 1995, we proved now its continuous distribution along the entire SE African coast from off Ras Ngomeni, Kenya, to off Durban, South Africa, at depths of 238-457 m. Neobythites kenyaensis is rather unique among the 54 species of its genus in possessing an ocellus positioned near the dorsal-fin origin (anterior ocellus) which it shares only with the West-Pacific N. longiventralis and West-Atlantic N. ocel-latus. It differs from the latter in the following characteristics: second, central ocellus more posteriorly placed on dorsal fin, more precaudal vertebrae (13 vs. 12), less developed gill rakers (8-10 vs. 14-16), shorter head (19.5-20.5 vs. 21.5-23.5% SL), and shorter pelvic fins (9.9-12.0 vs. 16.0-21.5% SL). Both species differ clearly from N. longiventralis in having a much shorter pelvin fin (9.9-215 vs. 32.0-34.% SL). The central ocellus-spot size, determined by the number of rays covered by the ocellus spot, varies considerably in N. kenyaensis and reaches the largest size reported for any ocellus-bearing Neobythites species. This character is strongly and positively correlated with both latitude and depth, suggesting gradual differentiation processes among adjacent populations or subpopulations. Another finding reported for the first time in Ophidiidae is the significant correlation of three otolith measurements with fish size (SL) in N. kenyaensis.

Udgave nummer1
Sider (fra-til)109-116
Antal sider8
StatusUdgivet - 28 feb. 2019

ID: 231199234