Alexandre Clistenes de Alcântara Santos

Estrutura da comunidade de peixes demersais da baía de Sepetiba, RJ

Um programa de amostragens mensais de arrasto de fundo em sete estacoes de coleta na Baia de Sepetiba foi realizado entre julho de 1993 e junho de 1994 com o objetivo de descrever a estrutura da comunidade de peixes e suas variacoes espaciais e temporais. Noventa e sete especies de peixes foram levantadas, compreendendo 70 generos e 38 familias. As familias Ariidae, Gerreidae, Sciaenidae, Carangidae e Sparidae, nesta ordem, foram as mais abundantes em numero, contribuindo com 69,9% do total capturado, enquanto Ariidae, Sparidae, Gerreidae, Haemulidae e Sciaenidae somaram 67,9% do peso total. Genidens genidens, Gerres aprion, Cathorops spixii, Micropogonias furnieri e Chloroscombrus chrysurus, nesta ordem, foram as especies mais abundantes, contribuindo cada uma com mais de 5% do numero total de peixes capturados. O maior numero de peixes foi associado as menores profundidades e transparencias, enquanto a salinidade apresentou, na maior parte do tempo, valores estaveis em torno de 29%o. Maiores abundâncias de peixes ocorreram entre fins do verao e inicio do inverno. O numero e peso dos peixes foram maiores na zona interna da Baia enquanto o numero de especies foi maior na zona externa, proxima ao limite com o mar. O elevado numero de especies de peixes sugere o importante papel da Baia de Sepetiba como area de criacao e desenvolvimento para a comunidade de peixes.

A new Aspidoras (Siluriformes: Callichthyidae) from rio Paraguaçu basin, Chapada Diamantina, Bahia, Brazil

During a recent ichthyological survey in Chapada Diamantina, Estado da Bahia, Brazil, a new, very distinctive Aspidoras was discovered in tributaries of the upper rio Paraguacu. The new taxon differs from its congeners mainly in having: a poorlydeveloped pigmentation pattern, restricted to minute scattered blotches on dorsal region of head and body, but grouped in small, irregular blotches along the lateral body plate junction; four or five caudal vertebra, anterior to compound caudal centrum, with neural and haemal spines placed posteriorly, close to post-zygapophyses; and post-zygapophyses of the precaudal vertebrae without dorsal expansions connected with their respective neural spines. The new species shares with Aspidoras velites dorsolateral body plates not touching their counterparts dorsally, and infraorbital bones with reduced flanges that are restricted to the latero-sensory canal. Both of these are considered reductive character states, probably indicating a paedomorphic condition to both species. The new species is also compared to Aspidoras maculosus, a congener which bears the most similar color pattern and is geographically closest to the new species. Durante um estudo recente sobre a ictiofauna da Chapada Diamantina, foi descoberta uma nova especie de Aspidoras, bastante distinta morfologicamente de suas congeneres, em afluentes do alto rio Paraguacu, Estado da Bahia, Brasil. O novo taxon difere das demais especies de Aspidoras principalmente pela pigmentacao pouco desenvolvida, restrita a minusculas maculas espalhadas na regiao dorsal da cabeca e corpo, concentradas em pequenas manchas irregulares ao longo da juncao das placas laterais; por apresentar as quatro a cinco ultimas vertebras caudais anteriores ao centro caudal composto com os espinhos neurais e hemais situados posteriormente junto as pos-zigapofises; e pos-zigapofises das vertebras pre-caudais sem expansoes dorsais unidas ao respectivo espinho neural. Alem disso, a nova especie compartilha com Aspidoras velites a condicao em que as placas dorso-laterais nao contatam suas contrapartes dorsalmente, e os ossos infra-orbitais reduzidos a pouco mais que o canal latero-sensorial, caracteristicas redutivas, provavelmente indicando um estado de carater pedomorfico para estas especies. A nova especie e ainda comparada a Aspidoras maculosus, congenere mais semelhante no padrao de colorido e tambem aquela mais proxima geograficamente.

Population structure of two Astyanax Baird & Girard, 1854 (Teleostei, Characidae) species from upper Paraguaçu river

The fishes of the family Characidae are among the main species of fresh water fishes in South America. In this work, some aspects of the population structure of two Astyanax species were assessed. The fishes were caught in Santo Antonio and Sao Jose rivers, in the Paraguacu basin, by standardized monthly samplings adapted to the microhabitats. Astyanax sp. b (Sao Jose river) presented larger size than Astyanax sp. a (Santo Antonio river). The length-weight relationship showed positive allometric growth for Astyanax sp. a, and negative for Astyanax sp. b. Both the species showed a long reproductive period, with higher activities in dry period.

A new Moenkhausia Eigenmann, 1903 (Ostariophysi: Characiformes) from Chapada Diamantina, rio Paraguaçu Basin, Bahia, Northeastern Brazil

Moenkhausia diamantina, new species, is described from tributaries of the rio Paraguacu, BA, northeastern Brazil. This species is distinguished from all congeners by features of body color pattern, the presence of scales on the predorsal median line and the number of anal-fin rays.

Composition and seasonal variation of the ichthyofauna from upper Rio Paraguaçu (Chapada Diamantina, Bahia, Brazil)

The aim of this work was to characterize the composition of the ichthyofauna of the upper course of the Rio Paraguacu. Two excursions were carried out, one in the dry season, and the other in the rainy season, with 36 localities sampled. A total of 63 species were collected. Multivariate analyses indicated that abiotic variables such as the channel order and altitude were the main influences on the number of species present. The number of species in each excursion was equivalent in the two seasons, suggesting that seasonal changes have little influence on the ichthyofauna of this area.

Temporal variation in fish composition and abundance in a perennial tributary of the rio Paraguaçu, a little-known drainage in the Brazilian semi-arid region

The rio Santo Antonio is a perennial lowland stream in the Brazilian semi-arid region, and is the main tributary of the upper rio Paraguacu, an important drainage of the Chapada Diamantina. The temporal variation of the fish composition and abundance in a stretch of the middle course of the river was evaluated. Sampling was carried out monthly between August 1998 and July 1999, using standardized gear and techniques. Data on water and air temperature, water transparency, maximum and mean depth, width and area of the channel, and flow were recorded on each fish sampling occasion. Univariate and multivariate statistical analyses were employed in order to detect significant temporal differences in environmental parameters and fish abundance. Temperature, transparency and channel depth drove opposite tendencies between the dry and rainy months. The fish community richness (32) and composition did not change between these periods, but large fish caught with gillnets were more abundant in the rainy months. We conclude that the undramatic disturbance in the hydrological stream conditions between the dry and rainy periods led to weak responses of the fish assemblage. Long-term monitoring would be necessary, however, to assess the real persistence of the fish community structure in this perennial stream.

Ampliação do limite norte de distribuição geográfica de Catathyridium garmani (Jordan & Goss 1889) (Actinopterygii: Achiridae)

Catathyridium garmani (Jordan & Goss, 1889) is being recorded for the first time in Northeastern Brazil on the basis of twenty-six specimens collected in the Paraguacu river estuary, Sao Felix municipality, Bahia state. This note relates the septentrional geographic distributions ampliation of this species, which was restricted to Rio de Janeiro state. Meristic and morphometric data from the collected species are presented.

Phylogeny of the subfamily Stelliferinae suggests speciation in Ophioscion Gill, 1863 (Sciaenidae: Perciformes) in the western South Atlantic

Phylogenies based on morphological and molecular data confirm the monophyly of the subfamily Stelliferinae; however, there is no consensus on the intergeneric and interspecific relationships in the group. Previous studies suggested the non-monophyly of Ophioscion and Stellifer, and possible cryptic species in Ophioscion punctatissimus. Therefore, we used mitochondrial (16S rDNA and COI) and nuclear (Rhodopsin, EGR1, and RAG1) regions to examine phylogenetic relationships among species of this subfamily. Our results confirmed the monophyly of Stelliferinae and supports the close relationship among Bardiella, Corvula and Odontoscion, which form a sister group to Stellifer and Ophioscion. Notwithstanding, all the results support the non-monophyly of Stellifer and Ophioscion and we suggest that a taxonomic revision should consider Ophioscion as a junior synonym of Stellifer. Moreover, O. punctatissimus was grouped into two clades, with the O. punctatissimus lineage I (LI) being closer to O. scierus from the eastern Pacific than to the O. punctatissimus lineage II (LII). The most recent common ancestor (TMRCA) for the O. scierus and O. punctatissimus LI and O. punctatissimus LII clade dates from 7.2 (HPD: 4.3-10.5) Ma, whereas TMRCA for the O. scierus and O. punctatissimus LI clade dates from 5.3 (HPD: 2.4-8.6) Ma, indicating that speciation processes may be related to the rise of the Isthmus of Panama. Phylogeographic analyses corroborate the hypothesis of speciation in O. punctatissimus. These results suggest that lineages of O. punctatissimus originated from distinct ancestors and, by morphological similarity, were considered the same taxon. A taxonomic revision should be performed to validate the species status of such lineages.

Record of the genus Sicydium Valenciennes , 1837 (Gobiidae, Sicydiinae) from Brazil and extent of distribution of S. punctatum Perugia, 1896

Sicydium punctatum, previously known from Panama, Caribbean islands, and coastal drainages of Venezuela, has a distribution that extends up to coastal drainages of Bahia state, Brazil. The genus Sicydium is formally recorded for Brazilian freshwaters. Comparisons are made between S. punctatum and other species of the genus based on data from the literature and presented here.