Implementing new northernmost records to modelling the distribution of Hypsiboas caingua (Anura: Hylidae) in South America.

New northwestern records of the striped treefrog Hypsiboas caingua (Carrizo, 1991 "1990") are presented for Brazil, extending its known geographic distribution approximately 115 km northward (linear distance) of the previous northernmost record of the species. In all new localities, individuals of H. caingua were only found in calling activity under temperatures below 18°C. The species appears to be associated with Atlantic Forest, although it had already been recorded in Cerrado. Although the scientific literature data suggests that H. caingua presents discontinuous geographical distribution, three methods of distribution modelling based on climatic data show that the species' distribution is continuous. The gap in the distribution may be related to the lack of field surveys in the regions that connect these populations, especially in colder periods. Nevertheless, factors other than climate might also be responsible for the current distribution of H. caingua, since the species was absent in well-surveyed sites situated between the areas of modeled distribution. Therefore, further studies on natural history, populations' genetic structure, and geographic distribution models implementing factors other than climate will be important to elucidate some ecological and evolutionary aspects of the distribution of H. caingua in South America.

Structure of aquatic vegetation of a large lake, western border of the Brazilian Pantanal.

Studies on Neotropical aquatic macrophytes have increased in recent decades, however species richness in wetlands of South America is far from being fully known. In addition, studies having an ecological approach are scarce in the Pantanal. Rapid assessments are essential for gaining knowledge of the biodiversity in the region. This study was performed in five sites of the Baía do Castelo, the western border of the Brazilian Pantanal, which included wild-rice patches, floating mats and floating meadows. At each site, plots of 0.5 × 0.5 m were set (n = 137), species of aquatic macrophytes were identified, their coverage was measured and the plot depth was estimated. We recorded 57 species in 26 families, of which Poaceae was the richest. The most frequent and abundant species was Commelina schomburgkiana; the second most frequent was Oryza latifolia,followed by Leersia hexandra, Enydra radicans and Pityrogramma calomelanos. The latter species was second in cover, followed by Pontederia rotundifolia, Eichhornia azurea, E. crassipes and Enydra radicans. These five species and C. schomburgkiana (the most abundant) together represent more than half of the coverage on the lake. Pontederia rotundifolia, Ludwigia helminthorrhiza, Pistia stratiotes, E. azurea, E. crassipes, Enydra radicans and Panicum elephantipes were strongly associated with deeper areas, while Oryza latifolia, Leersia hexandra and Salvinia auriculata were prevalent in shallow areas. Pityrogramma calomelanos, Ludwigia nervosa, Ipomoea alba, Cayaponia podantha, Polygonum acuminatum, Rhynchanthera novemnervia and Ludwigia leptocarpa were highly correlated with floating meadows. The structure of the habitat, natural dynamics and zonation of aquatic vegetation in the Baía do Castelo seems to be influenced by a variation in water levels, which promotes spatial segregation, most likely due to competition and/habitat preference.

Growth parameters estimates for a small fish of the Pantanal, Brazil: Moenkhausia dichroura (Characiformes; Characidae).

Growth parameters were estimated for Moenkhausia dichroura (Kner, 1858) (Characiformes, Characidae), a small-sized and very abundant fish of the Pantanal lentic habitats commonly known as "pequira ". A method based on the length frequencies distribution and the ELEFAN I routine from the FISAT program were used. The fish were collected in the Baia da Onça, an oxbowlake of the sub-region Pantanal of Aquidauana, Mato Grosso do Sul, Brazil, from June to December 1988. The standard length of the captured fishes ranged from 29 to 76 mm with an average of 53 mm. The estimated growth parameters were L(infinity) = 81 mm (standard length), k = 0.85 year(-1), C = 0.89, WP = 0.6 (Rn = 0.285). The WP indicated that growth reduction occurred in July, when the lowest temperature of the year was registered. The growth curve showed that captured individuals belonged to three cohorts. The obtained results seem robust and quite compatible with the biology of the fish and its adjustment to the environment. M. dichroura, in spite of not being a direct fishing interest, is an important species in terms of its ecological aspects, due to its abundance and high growth rate, and as a great food source for aquatic organisms and specially for larger fish of economic value. Considering the information gap about small fish, the parameters estimated for pequira constitute a comparison base for other growth studies of small-sized fish species of tropical environments.

Growth parameters estimates for a small fish of the Pantanal, Brazil: Moenkhausia dichroura (Characiformes; Characidae)

Growth parameters were estimated for Moenkhausia dichroura (Kner, 1858) (Characiformes, Characidae), a small-sized and very abundant fish of the Pantanal lentic habitats commonly known as "pequira ". A method based on the length frequencies distribution and the ELEFAN I routine from the FISAT program were used. The fish were collected in the Baia da Onça, an oxbowlake of the sub-region Pantanal of Aquidauana, Mato Grosso do Sul, Brazil, from June to December 1988. The standard length of the captured fishes ranged from 29 to 76 mm with an average of 53 mm. The estimated growth parameters were L¥ = 81 mm (standard length), k = 0.85 year-1, C = 0.89, WP = 0.6 (Rn = 0.285). The WP indicated that growth reduction occurred in July, when the lowest temperature of the year was registered. The growth curve showed that captured individuals belonged to three cohorts. The obtained results seem robust and quite compatible with the biology of the fish and its adjustment to the environment. M. dichroura, in spite of not being a direct fishing interest, is an important species in terms of its ecological aspects, due to its abundance and high growth rate, and as a great food source for aquatic organisms and specially for larger fish of economic value. Considering the information gap about small fish, the parameters estimated for pequira constitute a comparison base for other growth studies of small-sized fish species of tropical environments.

Neste estudo foram estimados os parâmetros de crescimento para Moenkhausia dichroura (Kner, 1858) (Characiformes, Characidae), um peixe de pequeno porte e muito abundante nos ambientes lênticos do Pantanal, onde é conhecido, vulgarmente, como "pequira". Para a estimativa dos parâmetros, foi utilizada uma metodologia baseada na distribuição mensal das freqüências de comprimento por meio da rotina ELEFAN I do programa FISAT. Os peixes foram coletados na Baía da Onça, uma lagoa do Pantanal do rio Aquidauana, Mato Grosso do Sul - Brasil, entre junho e dezembro de 1988. O comprimento dos exemplares capturados variou de 29 a 76 mm com média igual a 53 mm. Os melhores ajustes obtidos para os parâmetros de crescimento foram L¥ = 81 mm (comprimento padrão), k = 0.85 ano-1, C = 0.89 e WP = 0.6 (Rn = 0.285). O valor de WP indicou que a redução do crescimento ocorreu em julho, quando foram registradas as menores temperaturas do ano. A curva de crescimento obtida indicou que foram capturados indivíduos pertencentes a três cortes. Os resultados obtidos parecem robustos e bastante compatíveis com a biologia do peixe e seu ajuste ao ambiente. M. dichroura, apesar de não ser de interesse direto para a pesca, é uma espécie importante sob o ponto de vista ecológico, em função de sua abundância e elevada taxa de crescimento corporal, constituindo uma grande fonte de alimento para os demais organismos aquáticos e, sobretudo, para os peixes maiores de valor econômico. Em função da carência de informações, os parâmetros aqui estimados para a pequira constituem uma base de comparação para outros estudos sobre o crescimento de espécies de peixes de pequeno porte nos ambientes tropicais.

Isolation of the flagellum and characterization of the paraxial structure of Herpetomonas megaseliae.

It was observed in thin sections that the flagellum from Herpetomonas megaseliae, a protozoan of the Trypanosomatidae family, has, besides the axoneme, a filamentous lattice-like structure, the paraxial rod. Crithidia deanei, a protozoan of the same family, does not possess a paraxial rod in its flagellum. The flagella of these two trypanosomatids were isolated. Cultures were sonified and fractionated thus resulting the following fractions: total homogenates, deflagellated cell bodies, crude flagellar fraction and purified flagellar fraction from both H. megaseliae and C. deanei. The flagellar fractions are very pure and the flagella have their structures well preserved: axonemes and paraxial structures, where they exist, are intact, associated with one another and surrounded by the flagellar membrane. A comparative analysis of the purified flagellar fractions from both trypanosomatids was made using polyacrylamide gel electrophoresis. Two protein bands, with molecular weights of 78,000 and 73,000 daltons, which were enriched along the process of purification of the flagella from H. megaseliae, were found to correspond to the main components of the paraxial structure. These two bands were not observed in the purified flagellar fraction from C. deanei.