Stanley H. Weitzman

Estado atual da sistemática dos peixes de água doce da América do Sul

A fauna sul-americana de peixes de água doce, comparada com a do resto do mundo, é pouco conhecida. Há necessidade de coletas imediatas em muitas regiões, antes que os peixes se tornem raros ou se extingam . A fase descritiva da fauna de peixes de água doce da América do Sul desenvolveu-se em três periodos históricos. De 1750 até aproxima. damente 1866, boa parte dos grandes exemplares de interesse comercial foi descrita por zoólogos europeus. De 1866 a 1930, caracterizou-se por descrições de espécies de grande e pequeno porte, por ictiólogos tanto europeus como norte-americanos . De 1930 ao presente, foi, em parte, um período em que surgiram descrições adicionais na América do Norte, Europa e América do Sul. De 30 a 40% da fauna de peixes de água doce da América do Sul estão por ser descritos. Em termos de descrição e inventariação, o conhecimento desta fauna é comparável ao da fauna de peixes de água doce dos Estados Unidos e Canadá há cerca de 100 anos. Existem atualmente 2. 500 a 3. 000 espécies conhecidas de peixes de água doce na América do Sul e o número final pode chegar a 5. 000. A não disponibilidade de bibliografia antiga sobre peixes, de exemplares de museu para compar:1ções adequadas, e a falta de trabalhos faunisticos para a maior parte das áreas, são fatores que dificultam e até mesmo impossibilitam ictiólogos e biólogos de pesca no desempenno satisfatório de suas profissões na América do Sul. Muitas espécies descritas antes de 1870, precisam ser estuda.ctas e redescritas. A maior parte dos grupos de peixes de água doce sul-americanos necessita revisões taxonOmicas modernas.

Systematics of the neotropical fish subfamily Glandulocaudinae (Teleostei: Characiformes: Characidae)

The systematics of the Glandulocaudinae is reviewed in detail and justification for the recognition of the group as a subfamily is discussed. The subfamily Glandulocaudinae consists of three genera: Lophiobrycon with one species plesiomorphic in some anatomical features but some others exclusively derived relative to the species in the other genera; Glandulocauda with two species intermediate in phylogenetic derivation; and Mimagoniates with seven species (one new), all more phylogenetically derived concerning their pheromone producing caudal-fin organs and with other anatomical characters presumably more derived than in the species of the other genera. Glandulocauda melanogenys Eigenmann, 1911, is considered a junior synonym of Hyphessobrycon melanopleurus Ellis, 1911. A replacement name, Glandulocauda caerulea Menezes & Weitzman, is proposed for G. melanopleura Eigenmann, 1911. Gland cells found in the caudal-fin organs of all species are histologically indistinguishable from club cells and probably secrete a pheromone during courtship. The club cells are associated with somewhat modified to highly derived caudal scales forming a pheromone pumping organ in the more derived genera and species. This subfamily is distributed in freshwaters of eastern and southern Brazil, Paraguay, and northeastern Uruguay.

Comparison of spermiogenesis in the externally fertilizing Hemigrammus erythrozonus and the inseminating Corynopoma riisei (Teleostei: Characiformes: Characidae)

Spermiogenesis and sperm ultrastructure were analyzed in two species of characids with different modes of fertilization: externally fertilizing Hemigrammus erythrozonus and inseminating Corynopoma riisei. Spermiogenesis in H. erythrozonus is characterized by lateral development of the flagellum, nuclear rotation, formation of a shallow nuclear fossa, condensation of the chromatin by elimination of the electron-lucent area from the peripheral region of the nucleus, and renewal of the nuclear membrane. Multilammelated membrane and multivesicular bodies were also observed during elimination of the excess cytoplasm. The spermatozoon exhibits characters typical of aquasperm, i.e. a spherical head containing a spherical nucleus with highly condensed chromatin, several small mitochondria located at the base of the nucleus within a cytoplasmic collar that extends into a long cytoplasmic sleeve surrounding the anterior part of the single flagellum, which is contained within a cytoplasmic canal. The flagellum lacks fins. The proximal and distal centrioles are nearly parallel to one another, with the anterior tips of both located within shallow nuclear fossae. Spermiogenesis in C. riisei is characterized by nuclear elongation alongside the forming flagellum, formation of an elongate cytoplasmic canal, displacement and elongation of the mitochondria, and uniform condensation of chromatin throughout the nucleus through enlargement of the diameter of the chromatin granules. The spermatozoon has an elongate nucleus with two elongate mitochondria localized to one side. Mitochondria are also located posterior to the nucleus forming a mitochondrial region. The single flagellum, which lacks fins, is lateral to the nucleus and initially contained within the greatly elongate cytoplasmic canal before exiting the canal at its posterior terminus. The spermatozoon of C. riisei exhibits several characters typical of introsperm, such as an elongate nucleus and midpiece (mitochondrial region). The nuclear chromatin in the spermatozoon remains flocculent and is never as condensed as that seen in many characid sperm. Differences in spermiogenesis between externally fertilizing and inseminating characids are discussed.

Hyphessobrycon melanopleurus uruguayensis Messner, 1962, an available name and a senior synonym of Cyanocharax macropinna Malabarba & Weitzman, 2003 (Ostariophysi: Characidae)

Hyphessobrycon melanopleurus uruguayensis, Astyanacinus platensis, and Astyanax stenohalinus, published in a mimeographed paper by Messner in 1962 are considered available names. The subspecific name H. melanopleurus uruguayensis is recognized as a senior synonym of Cyanocharax macropinna Malabarba & Weitzman, 2003, and therefore referred to as Cyanocharax uruguayensis (Messner, 1962), new combination.