Second generation genetic linkage map for the gilthead sea bream Sparus aurata L.

An updated second linkage map was constructed for the gilthead sea bream, Sparus aurata L., a fish species of great economic importance for the Mediterranean aquaculture industry. In contrast to the first linkage map which mainly consisted of genomic microsatellites (SSRs), the new linkage map is highly enriched with SSRs found in Expressed Sequence Tags (EST-SSRs), which greatly facilitates comparative mapping with other teleosts. The new map consists of 321 genetic markers in 27 linkage groups (LGs): 232 genomic microsatellites, 85 EST-SSRs and 4 SNPs; of those, 13 markers were linked to LGs but were not ordered. Eleven markers (5 SSRs, 5 EST-SSRs and 1 SNP) are not assigned to any LG. The total length of the sex-averaged map is 1769.7 cM, 42% longer than the previously published one, and the number of markers in each LG ranges from 2 to 30. The inter-marker distance varies from 0 to 75.6 cM, with an average of 5.75 cM. The male and female maps have a length of 1349.2 and 2172.1 cM, respectively, and the average distance between markers is 4.38 and 7.05 cM, respectively. Comparative mapping with the three-spined stickleback (Gasterosteus acuulatus) chromosomes and scaffolds showed conserved synteny with 132 S. aurata markers (42.9% of those mapped) having a hit on the stickleback genome.