Abstract:
The dusky kob (Argyrosomus japonicus) is a large, estuarine-dependent sciaenid fish that has been
severely depleted in South African waters and that, in recent years, has received considerable
attention from the local fish farming industry. Discovery and application of appropriate molecular
markers is necessary to improve the understanding of wild population structure, assist the
effectiveness of broodstock and breeding programmes, and ensure monitoring of potential
interactions between wild and farmed fish. The present study uses a recently tested approach that
combines the FIASCO enrichment protocol with 454 GS-FLX Next Generation Sequencing, to identify
large numbers of microsatellite-containing sequences at a low cost and high discovery rate from the
dusky kob genome. Following the FIASCO enrichment (targeting specifically tetranucleotide repeats),
2355 potential tetranucleotide microsatellites (perfect repeat motifs including eight or more repeat
units flanked by regions for primer design) were identified from 1/5th of a single 454 lane. From
these sequences, a test panel of 60 potential markers was selected for validation. A total of nine
(15%) markers were successfully amplified from a test sample of wild dusky kob individuals and
showed high levels of polymorphism (observed heterozygosity per locus ranging between 0.375 and
0.905). Cross-species amplification of eight of these markers was also successfully carried out in
another closely related and commercially important South African sciaenid species, the silver kob (A.
inodorus). The microsatellite markers developed in the present study are readily available tools
suitable to address genetic variability of Argyrosomus species of Southern Africa.
