Dependence of juvenile reef fishes on semi-arid hypersaline estuary microhabitats as nurseries.

The differences between fish assemblages in three microhabitat types, in relation to vegetation and sediment characteristics of a hypersaline estuary located in an semi-arid zone in north-eastern Brazil, were investigated. Fishes were collected using a beach seine during the rainy and dry seasons in 2012. A total of 78 species were recorded, with the most common families being Gerreidae, Lutjanidae and Tetraodontidae. The majority of species were represented by juveniles, with Eucinostomus argenteus, Ulaema lefroyi and Sphoeroides greeleyi being the dominant species. The fish assemblage structures differed significantly among microhabitat types, with the narrow intertidal flat adjacent to the mangrove fringe supporting the most diverse fish fauna. In addition, only 27 species were common to all of the microhabitats. The results support the hypothesis that hypersaline estuaries serve as important nursery areas for various reef fish species, due to the structural complexity provided by their macroalgae beds and mangroves.

Molluscs associated with the macroalgae of the genus Gracilaria (Rhodophyta): importance of algal fronds as microhabitat in a hypersaline mangrove in Northeastern Brazil.

The fronds of marine macroalgae play an important role in coastal ecosystems because the algae banks are utilized as a microhabitat by different taxa, including molluscs, one of the most abundant and diverse animals of marine ecosystems. In this study, we characterized the malacofauna associated with the macroalgae Gracilaria domingensis (Kützing) Sonder ex Dickie 1874 and Gracilaria cuneata Areschoug 1854 of a hypersaline mangrove on the northern coast of the state of Rio Grande do Norte, Northeastern Brazil. The first alga dominates in the rainy season and it is substituted by second one in the dry period. A total of 1,490 molluscs were surveyed, representing 56 species in 29 families: 1,081 were associated with G. domingensis and 409 with G. cuneata, the latter showing the greater diversity (H'=1.25). Columbellidae, Neritidae, Pyramidellidae and Cerithiidae were among the most representative families in the number of species and individuals. The micromolluscs were dominant in the algal microhabitat, constituting 74.63% of the malacofauna recorded. The columbellid Parvanachis obesa (C. B. Adams, 1845) was the dominant species followed by the neritid Neritina virginea (Linnaeus, 1758) in both algae. In spite of the annual alternated succession of the algae species, at least 15 mollusc species are common for these algae. Furthermore, juveniles of P. obesa were recorded in both seasons, indicating a continuous reproduction. Possible reasons for difference in abundance, diversity and dominance of molluscs living on these algae are discussed. Both species of substrate-algae represent an important microhabitat for refuge, feeding and the reproduction of small-sized mollusc species during rainy and dry seasons.

Diadema ascensionis (Echinodermata: Echinoidea) is not restricted to Oceanic Islands: evidence from morphological data.

The genus Diadema presently consists of seven species, two of which are known from the Brazilian coast: D. antillarum and D. ascensionis. The first is usually known for shallow coastal areas, while the second was apparently restricted to oceanic islands. In February 2011, a dense population of D. ascensionis was observed on the coastal reefs of Praia do Francês (Alagoas State, northeastern Brazil). Five specimens were collected and transported to the laboratory where morphological studies of the test and pedicellariae were conducted. Subsequently, visits were made to scientific collections in order to compare and confirm species identifications. Our observations confirm the presence of tridentate pedicellariae with narrow and strongly curved valves. The axial cavity in the tips of the spines is filled with dense nonreticular tissue. This taxonomic data confirms the occurrence of D. ascensionis in coastal areas. On the coastal reefs of Praia do Francês, animals were observed from the beach to the reef formations about 200 m offshore in areas with a sandy substrate and in reef cavities, usually in clear and well illuminated waters. Solitary individuals or groups of up to 15 individuals formed dense populations in the area. We stress the importance of pedicellariae for the specific identification of the Diadematidae, considering that they are quite constant and reliable at this taxonomic level. Our results demonstrate that D. ascensionis is not restricted to insular environments and that this species may be common in shallow coastal habitats.

Diadema ascensionisMortensen, 1909 (Echinodermata: Echinoidea) is not restricted to Oceanic Islands: evidence from morphological data / Diadema ascensionisMortensen, 1909 (Echinodermata: Echinoidea) não está restrito a Ilhas Oceânicas: evidências de dados morfológicos

The genus Diadema presently consists of seven species, two of which are known from the Brazilian coast: D. antillarum and D. ascensionis. The first is usually known for shallow coastal areas, while the second was apparently restricted to oceanic islands. In February 2011, a dense population of D. ascensionis was observed on the coastal reefs of Praia do Francês (Alagoas State, northeastern Brazil). Five specimens were collected and transported to the laboratory where morphological studies of the test and pedicellariae were conducted. Subsequently, visits were made to scientific collections in order to compare and confirm species identifications. Our observations confirm the presence of tridentate pedicellariae with narrow and strongly curved valves. The axial cavity in the tips of the spines is filled with dense nonreticular tissue. This taxonomic data confirms the occurrence of D. ascensionis in coastal areas. On the coastal reefs of Praia do Francês, animals were observed from the beach to the reef formations about 200 m offshore in areas with a sandy substrate and in reef cavities, usually in clear and well illuminated waters. Solitary individuals or groups of up to 15 individuals formed dense populations in the area. We stress the importance of pedicellariae for the specific identification of the Diadematidae, considering that they are quite constant and reliable at this taxonomic level. Our results demonstrate that D. ascensionis is not restricted to insular environments and that this species may be common in shallow coastal habitats.

O gênero Diadema é composto por sete espécies, das quais duas são conhecidas para o litoral brasileiro: D. antillarum e D. ascensionis. A primeira é principalmente conhecida em áreas costeiras, enquanto que a segunda está aparentemente restrita a ilhas oceânicas. Em fevereiro de 2011, uma densa população de D. ascensionis foi observada nos recifes costeiros da Praia do Francês, no Estado de Alagoas, Região Nordeste do Brasil. Cinco espécimes foram coletados e transportados ao laboratório, onde estudos morfológicos da carapaça e das pedicelárias foram desenvolvidos. Subsequentemente, foram realizadas visitas a coleções científicas para a comparação e a confirmação da espécie. As observações, neste trabalho, evidenciaram a presença de uma pedicelária tridentada com valvas estreitas e fortemente curvadas. A cavidade axial nas pontas dos espinhos é preenchida por um denso tecido não reticular. Estes dados taxonômicos confirmam a ocorrência de D. ascensionis em áreas costeiras. Nos recifes costeiros da Praia do Francês, os animais foram observados a partir da praia em direção às formações recifais localizadas a 200 m da praia, em áreas de substrato arenoso, e nas cavidades do recife, geralmente em águas claras e bem iluminadas. Os indivíduos estavam solitários ou formando grupos de até 15 indivíduos. Destaca-se a importância das pedicelárias na sistemática dos Diadematidae, tendo em vista que as mesmas são bastante constantes e confiáveis para a identificação em nível específico. Os resultados do presente trabalho demonstram que D. ascensionis não está restrita a ambientes insulares e que esta espécie pode ser comum em habitats costeiros rasos.