The morphology and morphometric characteristics of the male swimming crab (Portunus pelagicus) from the East Sahul Shelf, Indonesia

The swimming crab (Portunus sp.) has distinct morphological characteristics. They come in a variety of colors and most have white patterns on their carapaces. The aim of this study is to determine the morphology and morphometric variation of male swimming crabs collected from the East Sahul Shelf in Indonesia. The sample was collected in West Papua, representative of the East Sahul Shelf area. The sampling locations were Sorong (30 crabs), Raja Ampat (45 crabs) and Kaimana (76 crabs). The morphological analysis determined the color, white patterns on carapace and shape of the gonopodium. While the morphometric characteristics were determined by measuring the length and width of the crabs' carapaces and meri. Data regarding the morphometric characteristics were analyzed using Stepwise Discriminant Analyses. The distance of genetic variation based on morphology and morphometric characteristics between populations was analyzed using Predicted Group Membership and Pairwise Group Comparison and the Test Equality of Group Means was used to analyze the more specific characteristic of the crab. Results indicated that the morphological characteristics based on color and the white patterns on the carapace of the swimming crab from West Papua were similar to Portunus pelagicus. However, based on the shape of the gonopodium, crabs from Sorong, Raja Ampat and Kaimana had characteristics similar to those of the Portunus armatus with the percentage of similarity being 30%, 40% and 25%, respectively. Morphometric analysis showed a significant difference between the crabs' morphometric characteristic and their populations from the three locations of sampling (p < 0.05). In conclusion, the swimming crabs from West Papua exhibit large variations in morphologic and morphometric characteristics. Thus, it can be concluded that the swimming crab from West Papua shows intraspecific variation.