Genomic signatures of paleodrainages in a freshwater fish along the southeastern coast of Brazil: genetic structure reflects past riverine properties.

Past shifts in connectivity in riverine environments (for example, sea-level changes) and the properties of current drainages can act as drivers of genetic structure and demographic processes in riverine population of fishes. However, it is unclear whether the same river properties that structure variation on recent timescales will also leave similar genomic signatures that reflect paleodrainage properties. By characterizing genetic structure in a freshwater fish species (Hollandichthys multifasciatus) from a system of basins along the Atlantic coast of Brazil we test for the effects of paleodrainages caused by sea-level changes during the Pleistocene. Given that the paleodrainage properties differ along the Brazilian coast, we also evaluate whether estimated genetic diversity within paleodrainages can be explained by past riverine properties (i.e., area and number of rivers in a paleodrainage). Our results demonstrate that genetic structure between populations is not just highly concordant with paleodrainages, but that differences in the genetic diversity among paleodrainages correspond to the joint effect of differences in the area encompassed by, and the number of rivers, within a paleodrainage. Our findings extend the influence of current riverine properties on genetic diversity to those associated with past paleodrainage properties. We discuss how these findings may explain the inconsistent support for paleodrainages in structuring divergence from different global regions and the importance of taking into account past conditions for understanding the high species diversity of freshwater fish that we currently observe in the world, and especially in the Neotropics.

Analysis of an astounding aggregation of Ranzania laevis (Molidae: Actinopterygii) in the tropical south-western Atlantic.

Unusual catches of more than 4200 kg of the slender sunfish Ranzania laevis are described from the south-western Atlantic, corresponding to the largest aggregation records for the species. These unexpected records were associated with unusually warm currents in the area. Males and females were physiologically able to spawn at the moment of capture, suggesting the occurrence of reproductive aggregation in this species.

Aspects of fish conservation in the upper Patos Lagoon basin.

The Patos Lagoon basin is a large (201 626 km(2) ) and complex drainage system in southern Brazil. The lagoon is 250 km long and 60 km wide, covering an area of 10 360 km(2) . The exchange of water with the Atlantic Ocean occurs through a 0·8 km wide and 15 m deep inlet, fixed by 4 km long jetties, at the southernmost part of the Patos Lagoon. The estuarine area is restricted to its southern portion (10%), although the upper limit of saline waters migrates seasonally and year to year, influenced by the wind regime and river discharge. The known number of recorded limnetic fish species is 200, but this number is expected to increase. A higher endemism is observed in fish species occurring in upper tributaries. The basin suffers from the direct impact of almost 7 million inhabitants, concentrated in small to large cities, most with untreated domestic effluents. There are at least 16 non-native species recorded in natural habitats of the Patos Lagoon basin, about half of these being from other South American river basins. Concerning the fishery, although sport and commercial fisheries are widespread throughout the Patos Lagoon basin, the lagoon itself and the estuarine area are the main fishing areas. Landing statistics are not available on a regular basis or for the whole basin. The fishery in the northern Patos Lagoon captures 31 different species, nine of which are responsible for most of the commercial catches, but only three species are actually sustaining the artisanal fishery: the viola Loricariichthys anus: 455 kg per 10 000 m(2) gillnet per day, the mullet Mugil liza: 123 kg per 10 000 m(2) gillnet per day and the marine catfish Genidens barbus: 50 kg per 10 000 m(2) gillnet per day. A decline of the fish stocks can be attributed to inadequate fishery surveillance, which leads to overfishing and mortality of juveniles, or to decreasing water quality because of urban and industrial activities and power production. Global climatic changes also represent a major threat to the Patos system by changing the frequency of El Niño-La Niña-Southern Oscillation (ENSO).

Reproductive strategies in two inseminating species of Glandulocaudini, Mimagoniates microlepis and Mimagoniates rheocharis (Characiformes: Characidae: Stevardiinae).

The reproductive biology of two inseminating Glandulocaudini species, Mimagoniates microlepis and Mimagoniates rheocharis, was investigated and compared with reproductive patterns described for other inseminating and non-inseminating characids, hypothesizing the evolutionary history of these reproductive traits. The long reproductive period, with higher activity in colder months, distinguishes the reproductive strategy of these species when compared with most characiforms. The M. rheocharis population was structured in two groups of males throughout the year, mature males with high gonado-somatic index (IG = 2·0 and 4·4) and immature and maturing males with low IG values (0·0 and 1·2). Mimagoniates rheocharis and M. microlepis showed the lowest absolute mean fecundities known for characids, indicating that inseminating species allocate less energy to oocyte production and reinforcing the hypothesis that insemination has an adaptive advantage, which provides a higher chance of fertilization.

Effects of bacterial infestation caused by human wastes on the skin structures of Mugil platanus Günther, 1880 (Mugilidae).

Manifestation of infectious pathologies in fishes usually increases in environments where organic wastes are disposed. Specimens of Mugil platanus Günther, 1880 and water samples collected at three points of the Tramandaí river were analyzed during a one year period. The macroscopic observation revealed ulcerations in the caudal peduncle area covered with a mass of amorphous and whitened tissues. Histopathologic analysis showed the presence of negative gram bacteria, probably responsible for alterations of the normal structure of the epidermic tissues. Non-parametric statistical analysis for ammonia concentration showed a significant variation among the three collected spots as well as in the multiple comparison between two spots. In this study, we describe cutaneous lesions observed in Mugil platanus specimens and tested their correlation with environmental ammonia concentration.

Effects of bacterial infestation caused by human wastes on the skin structures of Mugil platanus Günther, 1880 (Mugilidae) / Efeitos da infestação de bactérias provocada por resíduos humanos na pele de Mugil platanus Günther, 1880 (Mugilidae)

Manifestation of infectious pathologies in fishes usually increases in environments where organic wastes are disposed. Specimens of Mugil platanus Günther, 1880 and water samples collected at three points of the Tramandaí river were analyzed during a one year period. The macroscopic observation revealed ulcerations in the caudal peduncle area covered with a mass of amorphous and whitened tissues. Histopathologic analysis showed the presence of negative gram bacteria, probably responsible for alterations of the normal structure of the epidermic tissues. Non-parametric statistical analysis for ammonia concentration showed a significant variation among the three collected spots as well as in the multiple comparison between two spots. In this study, we describe cutaneous lesions observed in Mugil platanus specimens and tested their correlation with environmental ammonia concentration.

A manifestação de patologias infecciosas em populações de peixes costuma ser incrementada em ambientes onde são lançados despejos orgânicos. Exemplares da espécie Mugil platanus Günther, 1880 coletados em três pontos do rio Tramandaí foram utilizados para análise das alterações, e amostras de água foram tomadas durante o período de um ano para verificação da presença de bactérias. A observação macroscópica revelou ulcerações na região do pedúnculo caudal revestidas por uma massa de tecido amorfo e esbranquiçado. A análise histopatológica mostrou a presença de bactérias gram negativas, que provavelmente foram as responsáveis pela alteração da estrutura normal dos tecidos de revestimento do corpo. O resultado da análise estatística não paramétrica para a concentração de amônia mostrou variação significativa entre os três pontos amostrados bem como nas comparações múltiplas entre os pontos dois a dois. Este trabalho descreve as lesões cutâneas observadas em Mugil platanus e testa sua correlação com a concentração de amônia.

Morphology and histology of the male reproductive system in two species of internally inseminating South American catfishes, Trachelyopterus lucenai and T. galeatus (Teleostei: Auchenipteridae).

As part of an effort to characterize reproductive modifications in internally inseminating catfishes, ovaries and male reproductive systems were examined histologically in two species of auchenipterid catfishes, Trachelyopterus lucenai and T. galeatus, from southeastern Brazil. Internal insemination was documented in both species by the presence of sperm within ovaries. Although there is some variation in gross morphology of the male reproductive systems between the two species, both have four main regions: spermatogenic lobes, sperm storage regions, and secretory and storage regions of the seminal vesicle. In both species, the anterior portion of the reproductive system is spermatogenic and divided into numerous finger-like lobes. Posterior to the spermatogenic area is the storage region of the seminal vesicle, a large median structure with a honeycomb-like appearance. This region is consistently larger in T. lucenai. Attached to the storage region of the seminal vesicle in both species are secretory lobes comprised of tubules lined by secretory cells. These lobes in T. lucenai are small and located on the anterior aspect of the storage region of the seminal vesicle, whereas in T. galeatus the lobes are much larger and located laterally. The sperm storage regions of T. lucenai consist of two large lobes located ventral to the storage region of the seminal vesicle. Highly compact sperm packets (spermatozeugmata) fill the lumina of the ramifying tubules of these regions. Each spermatozeugma consists of elongate nuclei tightly arranged parallel to one another. In T. galeatus two distinct sperm storage regions are present. Just posterior to the spermatogenic lobes a series of small lobes serve as anterior sperm storage regions. Posterior to the secretory lobes of the seminal vesicle is a series of lobes, at the most posterior aspect of the reproductive tract, that serve as posterior sperm storage regions. Both are identical, histologically, to the sperm storage regions of T. lucenai. An absence of compact spermatozeugmata in the T. galeatus specimens may be related to variations in their sexual activity. The descriptions presented here allow for consistent terminology for comparison of regions of the male reproductive system based on presumed function.