Desarrollo de la sagitta en juveniles y adultos de Odontesthes argentinensis (Valenciennes, 1835) y O. bonariensis (Valenciennes, 1835) de la provincia de Buenos Aires, Argentina (Teleostei: Atheriniformes)

Abstract

The development of the otolith sagitta was described in young and adults of two silverside species. Odontesthes argentinensis was collected from Punta Rasa (36 degrees 22' S) and Miramar (38 degrees 16' S) and, Odontesthes bonariensis collected from Laguna de Chascomus (35 degrees 36' S). Sagitta morphology was studied in both species, analyzing four morphological groups of O. argentinensis (I: 75-120 mm, II: 130-220 mm, III: 230-270 mm and IV: 280-320 mm) and three morphological groups of O. bonariensis (I: 80-120 mm, II: 130-220 mm and III: 230-320 mm). The morphological features of the sagitta shared by both species are: sulcus present, dorsal areal depression on the medial face, lateral face with striations and the presence of the culminant point on the dorsal margin. The dorsal areal depression of O. argentinensis begins in contact with the cauda. This feature easily identifies the sagittae of young in both species. The dorsal areal depression is separated from the cauda in adults of both species, and the statistical analysis showed a discontinuous growth. Morphological differences were found between pairs of sagittae of the same specimen relating to the shape of the ostium, presence of an anterior excisure. rostrum and the culminant point, but no significant morphometric difference was found