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.
Highlights
The family Vermetidae comprises sessile marine gastropods with irregularly spiral shells that are attached on hard substrata
Among other important environmental features, wave action is commonly invoked to explain the development of vermetid reefs (Hughes 1979), their vertical distribution along the intertidal zone (Lipkin and Safriel 1971) and their densities (Schiaparelli and Cattaneo-Vietti 1999, Kelly III 2007)
Based on the external and internal morphological characteristics of the shells, we determined that all the vermetid reefs from Ilha Grande Bay were monospecific, constructed by Petaloconchus varians
Summary
The family Vermetidae comprises sessile marine gastropods with irregularly spiral shells that are attached on hard substrata. They are usually abundant in the intertidal zone, especially in the tropics (Keen 1961). Among other important environmental features, wave action is commonly invoked to explain the development of vermetid reefs (Hughes 1979), their vertical distribution along the intertidal zone (Lipkin and Safriel 1971) and their densities (Schiaparelli and Cattaneo-Vietti 1999, Kelly III 2007). Antonioli et al (1999) and Chemello and Silenzi (2011) stated that vermetid platforms are rare along sheltered coasts of the Mediterranean Sea, and concluded that wave action influences the distribution and size of the reef structures on a small spatial scale. Some species of the genus Petaloconchus prefer calm waters, according to Laborel (1977)
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