A B S T R A C TCumaceans are benthic crustaceans distributed worldwide, from intertidal to abyssal plains. They live in sandy and muddy bottoms and can sometimes be found in the water column. Despite their ecological importance as food items for fishes and other organisms and their usefulness as environmental indicators, very few studies have investigated their biodiversity and distribution in Brazil. The present paper reports an ecological study of the cumacean species found on the continental shelf off Santos, southeastern Brazil. It investigates the composition and spatio-temporal structure of the communities, the main environmental factors responsible for the maintenance of that structure and analyzes the effects of the seasonal oceanographic changes on the community descriptors. A grid of 21 stations located between 10 and 100 m depth was created in winter 2005 and summer 2006 and the sediment samples collected with a 0.1 m 2 box corer. Twenty four species were obtained, five of them being the most numerous: Diastylis sexpectinata, D. sympterygiae, Eudorella sp., Oxyurostylis salinoi and Anchistylis notus, the latter highly dominant in summer. Diastylis sympterygiae was characteristic of the shallowest and least saline stations (< 16 m depth; S = 33.07 -34.2) in both seasons. Of the total of 919 individuals, nearly 70% occurred in summer. The area was divided into four depth bands and no significant temporal difference was found as regards the density distribution of cumaceans in those bands as between the samples of the two campaigns. There were, however, spatial differences within bands in the summer campaign: the higher values of density, diversity and richness were close to the 50 m isobath in both campaigns, a fact that could well be attributed to the ongoing effect of the South Atlantic Central Water in this area. The results showed also that depth and the sediment particle size were the main structural factors determining the composition and distribution of the cumacean species. R E S U M OCumáceos são crustáceos peracáridos cosmopolitas que se distribuem desde a zona entre marés até os fundos abissais. Habitam fundos arenosos e lamosos e eventualmente são encontrados no ambiente pelagial. Apesar de sua importância na dieta de diversos organismos, e de serem considerados bons indicadores ambientais, poucos estudos ecológicos foram realizados com o grupo no Brasil, não havendo uma avaliação do papel que desempenham na estruturação e funcionamento do ecossistema bêntico. O presente trabalho teve como objetivo descrever a composição e a distribuição espaço-temporal das espécies de Cumacea, investigar a existência de comunidades e de sua estrutura, identificar os principais fatores responsáveis pelos agrupamentos encontrados e avaliar o efeito das mudanças sazonais da estrutura oceanográfica sobre os descritores utilizados. Para tanto duas campanhas foram realizadas, no inverno de 2005 e no verão de 2006, em uma grade de 21 estações situadas na plataforma continental sudeste ao largo de Santos, dispostas...
Cumaceans are Peracarid crustaceans distributed worldwide, occurring from intertidal zone to abyssal plains. They inhabit sandy and muddy bottoms, and are eventually found in the pelagic environment. Despite their importance as food for many organisms and their role as environmental indicators, few ecological studies have been conducted in Brazil up to now, and there are no efforts for understanding their role in structuring benthic communities. The aim of the present study is to describe the composition and spatio-temporal distribution of the cumaceans species in the continental shelf offshore of Santos, to investigate the existence and strucuture of ecological communities and the main factors responsible for their functioning, trying to assess the effects of the oceanographic changes upon the community descriptors. The samples were obtained on 21 stations placed in the southeastern continental shelf, between São Sebastião and Peruíbe, in winter 2005 and summer 2006, by means of a 0,09m 2 box corer and a rectangular dredge. The results showed the presence of 31 species of cumaceans in the whole area, being 24 in winter and 28 in summer. Higher values of density, diversity and richness obtained in stations near the 50m isobath in both campaigns can may be attributed to the South Atlantic Central Water presence on these areas, since it promotes intense eutrophication of the water column and environmental stability by means of the stablishment of a sub-superficial thermocline. The present study also showed that depth and sediment grain size were the main factors determining the composition and distribution of the cumacean communities. Three zones parallel to the coast with distinct depth ranges and oceanographic features were observed: shallow zone, intermediate zone and deeper zone, each one presenting characteristic species and ecologically structurated in different ways. The use of different sampling gears, as Box corer and dredge, allowed the complementation of data and enlarged the data set adding robustness to the study.
Diastylis sympterygiae Băcescu & Queiroz (1985) has been reported in many ecological studies conducted in the Patos Lagoon, southern Brazil. However, the original description of this species is based on damaged specimens from stomach contents of rays, and therefore insufficient for a confident identification. In the present contribution, based on a large number of well-preserved specimens now available from the type locality area, the description of this common euryhaline species is completed and its range of distribution as far north as São Paulo is extended.
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