Thesis (M.Sc.)--Chulalongkorn University, 2011

Shovel-nosed lobsters (Thenus species) or Kang-kradan (in Thai) are an increasingly important fishery in Thailand. Genetic diversity of Thenus is needed in order to understand how it has been distributed and currently habits most of Thailand’s sea coasts. This thesis was conducted to investigate the genetic diversity of Thenus in Thailand using mitochondrial cytochrome c oxidase subunit I (CO1) gene. Two hundred and six adult Thenus specimens were sampled from ten provinces. Genomic DNA was extracted from pereiopods and the CO1 gene was amplified and sequenced. Phylogenetic trees were reconstructed using neighbour-joining, maximum parsimony, maximum likelihood, and Bayesian methods. The molecular phylogeny clearly separated the Thai Thenus specimens into three clades: 163 individuals of T. indicus, 12 of T. orientalis, and 31 of T. unimaculatus. The recently proposed propodus characteristics can be used to separate Thai Thenus species. For the genetic diversity study of T. indicus, 87 haplotypes were found. The AMOVA statistical analysis showed the significantly different genetic variation among three geographical groups (upper Gulf of Thailand, lower Gulf of Thailand, and Andaman Sea). The time of divergence between Gulf of Thailand and from Andaman Sea populations was estimated to be about 20,000 years ago. These findings are an important knowledge for establishing a sustainable fisheries and conservation management in the future.