Morphology and molecular analyses of razor clams Solen spp. from Malaysia

Hung, Tze Mau (2009) Morphology and molecular analyses of razor clams Solen spp. from Malaysia. Masters thesis, Universiti Malaysia Sarawak (UNIMAS).

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Abstract

Taxonomy status of razor clam, Solen spp. is unclear due to the presence of morphological variations in the arrangement of pallial muscle scars and adductor scars. Three species of razor clams have been reported in various locations in Malaysia. Previous classifications were done by observing differences in the pallial muscle scars and adductor scar on the specimen shell. This study incorporated morphological and molecular approaches to evaluate the systematic relationships of Solen spp. in Malaysia more effectively. Multivariate morphometric tools were applied in verifying the reliability of using shell variables in classifying Solen spp. Eight morphological shell characters were scored: total shell length (TSL), shell width (SW), shell weight (SWHT), distance innermost point of pallial sinus to posterior margin (DPSPM), length of abductor scar (LAS), ligament length (LL), length of anterior abductor scar (LAAS), length of ventral limb of pallial sinus. Discriminant function analysis (DFA) and Principal Component Analysis (PCA) were applied to examine these eight morphometric variables of the Solen sp. The results showed the existence of four distinct morphospecies in the samples collected, indicating DFA morphometric analysis as useful tools for discriminating Solen spp. PCA managed to extract SW and LAAS as suitable variables to discriminate the three forms of Solen as Solen regularis (Anibal Biasa), Solen lamarckii (Ambal Jernang) and Solen sarawakensis Type I and Type II (Ambal Riong). As for the molecular aspects, phylogenetic relationship study was conducted among the Malaysian razor clam of family, Solenidae using partial 16S ribosomal RNA gene, ITS region of ribosomal DNA and COI mitochondrial gene sequences. This paper attempted to V combine both ecological aspect and molecular approaches to further clarify the issue on Solen spp. taxonomic relationship in species level. The obtained results manage to shed some light in the taxonomy of bivalve especially Solenids. Twenty-three samples from three species of the Peninsular and Sarawak razor clams (Family: Solenidae) was used in this study to examine on the phylogenogenetic relationship between species of razor clams based on three targeted genes. Phylogenetic analysis using neighbour joining, maximum parsimony and maximum likelihood methods support the monophyly of the four different taxa found in Sarawak namely Solen regularis, Solen lamarckii, Solen sarawakensis Type I and Type II. The results obtained from the phylogenetic trees generated from the three studied genes revealed that Solen sarawakensis Type II that was collected from Peninsular Malaysia could belong to a distinct species and failed to show any similarity in its morphological characters. Overall, this study has provided a significant contribution in clarifying the phylogenetic and relationships of Solenidae in Malaysia.

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