Variação ontogenética do caranguejo Goyazana castelnaui h. milneedwards, 1853 (brachyura, trichodactylidae) no semiárido do Brasil.

Abstract

Geometric morphometry is a low-cost analysis method, in which it is possible to transform data obtained from anatomical landmarks, providing detailed knowledge about the shape of the animal, including aspects about ontogeny and sexual dimorphism. Brachyurous grow through seedlings that continue to occur successively throughout growth, leading individuals to present body patterns, developing characteristics of sexual and age dimorphism. The species Goyazana castelnaui is of great ecosystem importance for the Pajeú River basin, especially because it is the only brachyurous species found. With this, the objective of this work was to know the ontogenetic trajectory and to identify morphometric variations of the crab G. castelnaui. To carry out this work, 36 females, 43 males and 162 juveniles (unidentified sex, still in the female's abdominal cavity) were collected in the Pajeú River, in the brazilian semiarid region. Crabs were analyzed on the carapace, pleon and right cheliped, which were photographed with individuals parallel to the plane, and 04 anatomical landmarks and 07 semi-landmarks were selected on the carapace; 03 landmarks and 10 semi-landmarks in the pleon and in the cheliped 03 landmarks and 07 semi-landmarks. In the analysis of principal components (PCA), the main variations occurred in the frontal and posterior region in the carapace, in the posterior and anterolateral region of the pleon and in the base of the fixed finger in the cheliped. In the analysis of canonical variation there was significant variation between genders as well as between juveniles and adults (p<0.05, Hotelling test with Bonferroni correction), and through the analysis of the discriminant (p<0.05) the carapace, pléon and chelipod obtained correct allocations that varied between 89.3% and 100.0%. The ontogenetic trajectory in G. castelnaui can be observed through the regression scores of the canonical correlations as a function of the centroid size, in which the carapace showed constant dimorphism reaching similar centroid sizes for both males and females (p>0.05); the pleon and the cheliped when juveniles, there was no separation of groups (dimorphism), with variation and change as they grew (ontogenetic trajectory) reaching different centroid sizes (p <0.05), in females reaching a larger size in the pléon and in the males a larger size in the chelipods, consistent with the monophyletic theory of the Brachyura.