Morfometria geométrica de Anomalocardia flexuosa (Linnaeus, 1767) (Bivalvia: Veneridae): efeitos das características do habitat e da densidade populacional

Abstract

Anomalocardia flexuosa(Linnaeus, 1767)is a bivalve mollusc widely distributed along the Brazilian coast, showing a large adaptability in different enviroments, such as sandy beaches, mangroves and coral reefs. Knowing that in a hypersaline estuarine environment the size and shape of the shell can be influenced by environmental factors and intraspecific disputes, the present work was developed with the objective of analyzing, using the geometric morphometric techniques, changes in the shape of the shell of Anomalocardia flexuosa, considering the high population density and the influence on the space dispute with a prairie of Halodule wrightii (Ascherson, 1868) in an estuary on the semiarid coast of Brazil. The study used specimens colleted by the research project “Population ecology and fisheries dynamics of Anomalocardia flexuosa in a hypersaline estuary in the Brazilian semiarid region", from the Zoobentos Laboratory of the Instituto de Ciências do Mar, Universidade Federal do Ceará (Labomar/UFC). The morphometric analysis was based on the use of landmarks that represent the morphological characteristics of the hinge, the adductor muscular system and the areas of the shield and lunula of the specie. Two descriptive and morphometric analyzes were performed, due to the disparity between the number of individuals in each area. In the two descriptive analyses, there were differences in length between the areas, with Area 2 showing individuals larger in length than Area 1. For the analysis of geometric morphometry, the method of superposition of Procrustes with the coordinates of the landmarks was used and later Principal Component Analysis (PCA), Canonical Variable Analysis (CVA) and Discriminant Function. The results revealed a tendency of not having a very explicit separation in relation to the form, although an anteroposterior elongation is more pronounced in the individuals. Geometric morphometric techniques were effective in punctuating how much and where changes in Anomalocardia flexuosa shell shape occurred when analyzed in two different biotopes.