The morphology and 12 shell morphometric features proportionate to shell length were analysed between local hard clam; Meretrix lyrata, M. meretrix and M. lusoria from Sarawak, Malaysia. Meretrix spp. was observed to comprise a unique feature of a pallial sinus scar for each species. Analysis of variance revealed significant differences among Meretrix spp. using proportion ratios of SL for SW; LL; AL; LCT; AW; PW and PS (p<0.05). Cluster analysis among morphometric features of M. lyrata, M. meretrix and M. lusoria were discriminated at 98.5% similarities and supported by the principal component analysis. The present study suggests that pallial sinus scar shape, together with interior and exterior morphometric features, were suitable as identification keys for Meretrix spp. Hence, the present study emphasizes on the application of interior, rather than exterior morphology and morphometric features in hard clam identification before further investigation can be performed through genetic identification means.
Investigation on copepod communities in Perai river estuary was conducted from November 2005 to May 2006. Five stations were established for monthly sampling and were located from the river mouth to the upper reaches of the river. Copepod samples were collected from vertical tows using a standard zooplankton net. The Perai river estuary was slightly stratified and salinity decreases significantly from the mouth of the river towards the upper reaches of the river. A total of 28 species of copepods were recorded and comprised of 14 families, Paracalanidae, Oithonidae, Corycaeidae, Acartiidae, Calanidae, Centropagidae, Eucalanidae, Pontellidae, Pseudodiaptomidae, Tortanidae, Ectinosomatidae, Euterpinidae, Clausidiidae and Cyclopidae. A total of 10 species showed high positive affiliation towards salinity (R > 0.60), Acartia spinicauda, Euterpina acutifrons, Microsetella norvegica, Oithona nana, Oithona simplex, Paracalanus crassirostris, Paracalanus elegans, Paracalanus parvus, Pseudodiaptomus sp. and Hemicyclops sp. The copepod species Pseudodiaptomus dauglishi were negatively affiliated towards salinity (R = -0.71). The copepod assemblages classified into two distinct groups according to salinity regimes, euryhaline-polyhaline group (25 marine affiliated species) and oligohaline-mesohaline group (3 freshwater affiliated species).
Macrobenthos in coastal environment that play a significant role in the food web. It could also use as a good indicator of aquatic ecosystem health. The abundance and composition of macrobenthos in Bakkhali channel system, Cox's Bazar were conducted in relation to the soil parameters. Samples were collected using Ekman Berge bottom grab from five different stations of Bakkhali channel. Macrobenthos were comprised of five major groups namely Polychaeta (9.96-30.31%), Oligochaeta (3.68-59.707%), Crustacea (0.02-58.40%), Bivalvia (1.40-82.09%) and Gastropoda (0.08-4.25%). Total number of macrobenthos was higher at station I (9000 individuals m(-2)) and station II (8517 individuals m(-2)) compared to other stations. Shannon diversity index among the stations ranged from 0.65-1.04. Soil pH and soil moisture ranged from 6.1-6.4 and 23.44-31.29%, respectively. The highest organic carbon concentration was observed at station I (2.11%) and lowest at station III (1.40%). Maximum fraction of sand by weight was found at stations II (81.88%) and III (87.88) while the highest fraction of clay (21.52%) and silt (8.0%) were recorded in station I. It was observed that benthic bivalves were positively correlated (r = 0.891, p > 0.05) with silt fraction of the sediments.