Comparative oocyte morphology and early development in three species of trahiras from the São Francisco River basin, Brazil
Oocyte morphology, embryogenesis and early larval development were compared in Hoplerythrinus unitaeniatus, Hoplias lacerdae and Hoplias malabaricus (Characiformes: Erythrinidae) by macroscopical, histological, histochemical and ultrastructural analyses. The eggs of the three species were yellowish and adhesive, containing carboxyl and sulphate radicals in the glycoconjugates of the zona radiata. A complex surface arrangement was identified in oocytes of H. unitaeniatus and H. lacerdae, while H. malabaricus had a simple oocyte surface pattern. Lectin histochemistry revealed different carbohydrate terminal residues in cortical alveoli, outer zona radiata and follicular cells of the three species. At the animal pole, the oocyte surface topography surrounding the micropyle was species-specific. The micropylar cell was ConA-positive, suggesting the presence of carbohydrates with mannose/glucose terminal residues that could have a role during fertilization. The erythrinids exhibited a prolonged embryonic and larval development compared to other Characiformes, a reproductive strategy used for increasing offspring protection. Early development proceeded most rapidly in H. unitaeniatus, followed by H. malabaricus and then H. lacerdae, which could have more developed parental care behaviour. An adhesive organ composed of secretory prismatic cells protruding from the cephalic region of the three erythrinid larva allowed them to attach to one another during development. Reproductive behaviour and early developmental strategies were similar in the three species, but the oocyte surface morphology suggests a close relationship between H. unitaeniatus and H. lacerdae.
egg surface ultrastructure;
Document Type: Regular Paper
Graduate Program Zoology of Vertebrates, Pontifical Catholic University of Minas Gerais, 30535-610, Belo Horizonte, Minas Gerais, Brazil
Institute of Biological Sciences, Federal University of Minas Gerais, P. O. Box 486, 30161-970 Belo Horizonte, Minas Gerais, Brazil
Hydrobiology and Hatchery Station of Três Marias-CODEVASF, 39205-00, Três Marias, Minas Gerais, Brazil
Publication date: May 1, 2007