Abundance of the reef-building Petaloconchus varians (Gastropoda: Vermetidae) on intertidal rocky shores at Ilha Grande Bay, southeastern Brazil.

The reef-building vermetid Petaloconchus varians occurs in the western Atlantic Ocean, from the Caribbean Sea to the southern coast of Brazil. The present study evaluated the abundance of P. varians on intertidal rocky shores in Ilha Grande Bay (Rio de Janeiro State), and characterized their reefs, describing the species density, besides the weight and the belt width of the reefs. Petaloconchus varians reefs were recorded at 25 sites, with rocky shores exposed to different wave action (very sheltered, sheltered, semi-exposed and exposed) and slopes (10° to 46°). Clusters of individuals constructed large reefs along the middle intertidal zone, creating a wide belt (38 cm to 2 m). The density of P. varians and the weight of the reefs ranged from 620 to 2,559 ind.100 cm-2 and from 100 to 1,500 g.100 cm-2, respectively. Considering that the species was last reported from the area in the mid-20th century, the present study suggests that P. varians reefs are becoming dominant in the intertidal zone of rocky shores in Ilha Grande Bay. This is a contribution to knowledge of this ecosystem in Ilha Grande Bay, in view of local or global ecological changes.

Abundance of the reef-building Petaloconchus varians (Gastropoda: Vermetidae) on intertidal rocky shores at Ilha Grande Bay, southeastern Brazil

ABSTRACT The reef-building vermetid Petaloconchus varians occurs in the western Atlantic Ocean, from the Caribbean Sea to the southern coast of Brazil. The present study evaluated the abundance of P. varians on intertidal rocky shores in Ilha Grande Bay (Rio de Janeiro State), and characterized their reefs, describing the species density, besides the weight and the belt width of the reefs. Petaloconchus varians reefs were recorded at 25 sites, with rocky shores exposed to different wave action (very sheltered, sheltered, semi-exposed and exposed) and slopes (10° to 46°). Clusters of individuals constructed large reefs along the middle intertidal zone, creating a wide belt (38 cm to 2 m). The density of P. varians and the weight of the reefs ranged from 620 to 2,559 ind.100 cm-2 and from 100 to 1,500 g.100 cm-2, respectively. Considering that the species was last reported from the area in the mid-20th century, the present study suggests that P. varians reefs are becoming dominant in the intertidal zone of rocky shores in Ilha Grande Bay. This is a contribution to knowledge of this ecosystem in Ilha Grande Bay, in view of local or global ecological changes.

The first finding of Ostrea cf. puelchana (Bivalvia) living as epibiont on Callinectes exasperates (Decapoda) / Primeiro registro de Ostrea cf. puelchana (Bivalvia) vivendo como epibionte sobre Callinectes exasperates (Decapoda)

This paper describes the epibiosis of Ostrea cf. puelchana on Callinectes exasperatus (Gerstaecker, 1856), both collected from the estuary of the Paraíba River, in the state of Paraíba, northeastern Brazil. The basibiont crab was captured using a trap installed in mangrove area at a depth of about 2 meters. The oyster was closely attached to the left side of dorsal carapace covering most of the epibranchial, mesobranchial and metabranchial regions. Possible advantages and disadvantages for both the epibiont and the basibiont are discussed. We believe that young O. cf. puelchana may avoid a variety of potential predators due to the considerable movement capacity of C. exasperatus and may also serve as a small protective shield for the basibiont. However, the oyster, which is a bivalve with an epifaunal lifestyle, is likely to be negatively affected, mainly due to burrowing activity of the crab. This is the first record of epibiosis between bivalves of the genus Ostrea Linnaeus, 1758 and crabs of the genus Callinectes Stimpson, 1860.

O presente estudo descreve a epibiose de Ostrea cf. puelchana sobre Callinectes exasperatus (Gerstaecker, 1856), ambos coletados no estuário do Rio Paraíba, no estado da Paraíba, nordeste do Brasil. O caranguejo basibionte foi capturado usando uma armadilha instalada em área de mangue em cerca de 2 metros de profundidade. A ostra estava fixada sobre o lado esquerdo da carapaça dorsal cobrindo grande parte das regiões epibranquial, mesobranquial e metabranquial. Possíveis vantagens e desvantagens para ambos epibionte e basibionte são discutidas. O espécime jovem de O. cf. puelchana pode evitar uma variedade de predadores potenciais devido à considerável capacidade de deslocamento de C. exasperatus, ao mesmo tempo, essa espécie pode atuar como um escudo protetor para o basibionte. Entretanto, o ostreídeo possui um estilo de vida epifaunal, podendo ser afetado de forma negativa, principalmente devido à atividade de escavação do caranguejo. Este é o primeiro registro de epibiose entre bivalves do gênero Ostrea Linnaeus, 1758 e caranguejos do gênero Callinectes Stimpson, 1860.