Ultrastructure of the Sagitta Otolith in Different Body Size Groups of Climbing Perch Anabas testudineus (Anabantidae)

The ultrastructural characteristics of the sagitta of the climbing perch, Anabas testudineus (Bloch, 1792) in different body size groups are described for the first time for the family Anabantidae using scanning electron microscopy. The sagitta is an ovate-shaped structure with a well-developed rostrum and anti-rostrum. The sulcus is S-shaped and has ostio-pseudocaudal type structure. The sulcus lacks collum. The ostium is a spoon-headed structure and is comprised of a triangular ostial colliculum. The excisura major is a prominent V-shaped structure and its width declines along with the growth of the total fish length. The cristae are prominent on both sides of the sulcus. The caudal colliculum is relatively well-developed in the smaller size groups than that of larger groups. The posterior end of otolith is blunt. The Kruskal–Wallis H test revealed that some sagitta features show significant differences in different body size groups of A. testudineus . The otolith weight is more closely related to the body length than the otolith length and width. Therefore, otolith weight can be used as an important predictor to evaluate the fish size.