Abstract
In fishes, gonad morphology is an important parameter to understand the reproductive biology, phylogenetic relationships and systematic studies. The main objective of this study was to make a comparative analysis of the morphology of mature ovary and testis in six fish species of the family Anostomidae. A total of 212 specimens, presenting maturing gonads, were captured from the São Francisco River, Três Marias Reservoir area, in Southeastern Brazil, between August 2008 and December 2010. The six analyzed species had mature ovaries and showed a grayish color. In vitellogenic oocytes (VO), cortical alveoli (CA) were composed by small vesicles in all Leporinus species, but in Leporellus vittatus and Schizodon knerii the CA were large vesicles. However, the CA of all species showed similar histochemical content. The pellucid zone consists of two layers to all species, but it was thicker in S. knerii (11.5 ± 1.8 µm) than in L. vittatus (9.0 ± 0.8 µm) and Leporinus species (3.5 ± 0.6 - 8.7 ± 0.9 µm). Follicular cells of the VO were respectively cubic and prismatic in animal and vegetative poles of S. knerii (22.3 ± 3.2 and 61.1 ± 9.6 µm), and squamous in the other species (1.3 ± 0.3 - 1.6 ± 0.3 µm). Females of S. knerii and males of L. vittatus showed lower values of gonadosomatic index (GSI) than the other assessed species. All evaluated species presented testicular morphology similar to most neotropical Characiformes, with unrestricted spermatogonial testis and anastomosing tubular organization of seminiferous tubules. Phenotypical differences in the vitellogenic oocyte of Anostomidae fishes, confirmed the taxonomic position of S. knerii as different genus in relation to Leporinus and L. vittatus. Despite being placed in different genera, the characteristics of the vitellogenic oocytes of L. vittatus were similar to those found in the studied Leporinus.
Highlights
The Characiformes are one of the orders with the largest number of families and subfamilies amongst fish (Nelson, 2006), and the Anostomidae family comprises approximately 163 species in 12 genera distributed throughout the neotropical region (Garavello & Britski, 2003; Reis, Kullander, & Ferraris, 2003)
Since gonad morphology is an important parameter for the understanding of the reproductive biology, phylogenetic relationships and systematic studies, the main objective of this study is to make a comparatively analysis of the morphology of mature ovary and testis in six fish species of the family Anostomidae of the São Francisco River basin, in Minas Gerais, Brazil: Leporellus vittatus (Valenciennes 1850); Leporinus obtusidens; Leporinus piau Fowler, 1941; Leporinus reinhardti Lütken, 1875; Leporinus taeniatus Lütken, 1875 and Schizodon knerii (Steindachner 1875)
L. obtusidens was largest in total length and body weight, while the smallest were L. taeniatus and L. vittatus (Table 1)
Summary
The Characiformes are one of the orders with the largest number of families and subfamilies amongst fish (Nelson, 2006), and the Anostomidae family comprises approximately 163 species in 12 genera distributed throughout the neotropical region (Garavello & Britski, 2003; Reis, Kullander, & Ferraris, 2003). In the São Francisco River basin, one of the main rivers in Brazil for fishing resources, there are three genera of Anostomidae, Leporellus Lütken 1875, Leporinus Agassiz 1829 and Schizodon Agassiz 1829, including the commercially important species for sport and small-scale fishing of Leporinus obtusidens (Valenciennes 1837), which may reach a length of 40 cm (Garavello & Britski, 2003). Since gonad morphology is an important parameter for the understanding of the reproductive biology, phylogenetic relationships and systematic studies, the main objective of this study is to make a comparatively analysis of the morphology of mature ovary and testis in six fish species of the family Anostomidae of the São Francisco River basin, in Minas Gerais, Brazil: Leporellus vittatus (Valenciennes 1850); Leporinus obtusidens; Leporinus piau Fowler, 1941; Leporinus reinhardti Lütken, 1875; Leporinus taeniatus Lütken, 1875 and Schizodon knerii (Steindachner 1875)
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