Genetic diversity of the sea cucumber, Holothuria scabra in New Caledonia, Australia (Northern Territory) and Bali

Within-region genetic heterogeneity of Holothuria scabra populations in New Caledonia was examined through allozyme electrophoresis. Five locations, each separated by 60-130 km, were selected along the coast of New Caledonia and 2 replicate sites (8-23 km apart) were chosen within 4 of these locations on the west coast of the island. Only one site was selected on the northeast coast. Between 14 and 34 adult Holothuria scabra were collected from each site. A short section of the upper intestine (5-10 cm), without sediments, was dissected from each animal and stored in liquid nitrogen until analysed. Holothuria scabra samples from Bali (n=90) and Knocker Bay, Australia (n=47), and existing data from the western Pacific: Solomon Islands; Torres Strait; and the Queensland Coast (Upstart Bay and Hervey Bay) were compared with the data from New Caledonia to investigate larval connectivity over a wider geographic scale. Seven polymorphic enzyme loci were surveyed using allozyme electrophoresis: GPI, HK, MDH, PEP-1, PEP-2, PEP-3 and PGM. Basic analyses of genetic variability (allele frequencies, number of polymorphic loci, heterozygosity) were carried out. The allelic richness for each population was calculated. F statistics were calculated and genetic distance analyses, cluster analyses and Mantel tests were performed.
This research was undertaken to improve understanding of the genetic differentiation between stocks of Holothuria scabra at different spatial scales so that the release of cultured juveniles in restocking programs can be planned in a responsible way to preserve the genetic diversity of existing stocks.
Sampling sites in New Caledonia: A=Baie de Sainte-Marie; B= Ilot Maître; C=Ouano; D=Ilots Kundogi; E=Plateau de Béco; F=Pointe Pindaï; G=Pouangué; H=Ouaco; I=Récif Thaavaam (Ilot Cocotier).