Larval Development of Lampanyctus Species (Pisces: Myctophidae) from the Southwestern Indian Ocean, and Species Groups Based on Larval Characters

Ten species belonging to the genus Lampanyctus were found among the fish larvae collected in the Agulhas Current region during a pilot study and three cruises carried out during 1989–1991. Six were identified to species level: L. achirus, L. alatus, L. ater, L. lepidolychnus, L. nobilis and L. pusillus. Individuals of four other species were differentiated, but they were too small to show the meristic or photophore characters that allow species identification with complete confidence. The most probable identifications of these four species as L. festivus, L. turneri, L. lineatus, and a species of the L. regalis-ater group, is discussed in the paper. Detailed descriptions of larval development are given for those species with previously unknown early life history stages, together with a discussion of the characters on which the identifications were based. Information on the characters that allow differentiation of all the Lampanyctus larvae that may occur in the Southwestern Indian Ocean is also given. A brief description of L. australis larvae from the northern Benguela region is therefore also included. Larval characters of other Lampanyctus species, obtained from the literature or determined after examination of samples obtained in other geographical areas, were used, together with the present information, to study affinities between species. Three very dissimilar groups of species were differentiated. The most similar species were L. crocodilus, L. australis and L. alatus.