Research Journal of Fisheries and Hydrobiology, 3(2): 54-62, 2008 © 2008, INSInet Publication Corresponding Author: Mohd Hanafi Idris, Department of Animal Science and Fishery, Faculty of Agriculture and Food Sciences, Universiti Putra Malaysia Bintulu Campus, Nyabau Road, P. O. Box 396, 97008 Bintulu, Sarawak, Malaysia. E-Mail: mhanafi@putra.upm.edu.my 54 Biodiversity and Distribution of Pen Shells (Bivalvia: Pinnidae) from the Seagrass Beds of Sungai Pulai, Peninsular Malaysia Mohd Hanafi Idris, Aziz Arshad, Japar Sidik Bujang Mazlan Abd. Ghaffar and 1,3 2 1,3 4 Siti Khalijah Daud 3 Department of Animal Science and Fishery, Faculty of Agriculture and Food Sciences, 1 Universiti Putra Malaysia Bintulu Campus, Nyabau Road, P. O. Box 396, 97008 Bintulu, Sarawak, Malaysia. Department of Aquaculture, Faculty of Agriculture II, Universiti Putra Malaysia, 2 43400 UPM Serdang, Selangor, Malaysia Department of Biology, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang, 3 Selangor, Malaysia. School of Environmental and Natural Resources Science, Faculty of Science and Technology, 4 Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia. Abstract: Studies on biodiversity and distribution of pen shells were conducted at Merambong Shoal (N1 19’ 55.62” E103 35’ 57.75”), Tanjung Adang Shoal (N1 19’ 48.03” E103 33’ 59.44”) o o o o and Merambong Island (N1 18’ 54.83” E103 36’ 33.37”) off South Western Johor coast, Malaysia o o from August 2005 to June 2006. A total of 135 individuals were collected from three different stations. Pinna bicolor and Pinna atropurpurea were dominance. Higher density of pen shells were recorded in St 1 with 0.027 ind/m and St 2 was recorded lower density with 0.004 ind/m at 2 2 Merambong Shoal. Univariate analysis at Merambong Shoal population recorded higher values for diversity and richness indices compared to Tanjung Adang Shoal and Merambong Island but the value of Evenness index was quite similar between the three stations. Fifty eight individuals of pen shell were collected from study areas for taxonomy identification. Seven groups of pen shell were identified base on the internal and external surface of the valves of pen shell. Seven species were clearly identified which Pinna and Atrina were dominant from the seagrass bed of Sungai Pulai, Peninsular Malaysia. Key words: Bivalvia, Pinnidae, Pen Shells, Distribution, Diversity, Malaysia INTRODUCTION The Pinnidae or Pen shells are widely distributed in the Indo-Pacific from southeastern Africa to Melanesia and New Zealand, north to Japan and to New South Wales and New Zealand. Pen shells are also found in Mediterranean and American waters . Atrina and Pinna species exist as [19.16.3.25] metapopulations, composed of small groups or patches of individuals. Pen shells are generally large bivalves (30-48 cm long), triangular in shape, thin, shell tapering to a point and light yellow-brown to dark brown in color. Pen shells live with their pointed end embedded in sediment, attached by abundant fine byssal threads . Pen shells are relatively common [13,22,8,9] at the sandy substrate of the seagrass beds (Posidonia oceanica and Cymodocea nodosa ), lagoons and coral rubble areas . Most publications of pen shells come [1,14] from the researchers in Indo-Pacific, Mediterranean and American regions . Pen shells show a considerable [19,16,17] morphological variation creating taxonomic confusion for many taxonomists. The genetic heterogeneity analysis and RAPD marker detection have been used to identify pen shells up to species level . According [24]