Isolation and characterization of 21 microsatellite loci for the sea cucumber Holothuria (Halodeima) atra (Echinodermata, Holothuroidea) reveal low asexual propagation through time in Reunion Island (southwestern Indian Ocean).

ABSTRACT

BACKGROUND: Holothuria (Halodeima) atra Jaeger, 1833 is a tropical sea cucumber usually harvested for the "bêche-de-mer" trade market. It has been reported to reproduce both sexually, through gamete spawning, or asexually, through fission. To date, no study has ever investigated clonality, nor genetic connectivity, among its populations, using microsatellite markers. METHODS AND RESULTS: We isolated the first 21 microsatellite loci specific for H. atra, which were then used to investigate clonal diversity, genetic structure and diversity among 44 H. atra individuals sampled in Reunion Island (southwestern Indian Ocean), over two seasons. All 21 loci were polymorphic, with number of alleles per locus ranging from 2 to 10. No repetitive multi-locus genotype (MLG) and few clonal lineages (MLL) were found. Observed heterozygosities per locus and season ranged from 0.000 to 0.909, while expected heterozygosities ranged from 0.290 to 0.882. Four loci were at Hardy-Weinberg equilibrium for both seasons, all others presenting a deficit of heterozygotes in one or both seasons. Meanwhile, no genetic differentiation was detected between seasons, according to assignment tests and global FST. CONCLUSIONS: These results suggest low asexual propagation in this population. These loci represent useful tools to better understand reproductive strategies and population connectivity of H. atra, and thus provide relevant knowledge for efficient management.