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-20 th 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.

Host Range of the Coral-Associated Worm Snail Petaloconchus sp. (Gastropoda: Vermetidae), a Newly Discovered Cryptogenic Pest Species in the Southern Caribbean

“…A small, concave operculum is characteristic for the genus Petaloconchus H.C. Lea, 1843 [24]. Owing to its symbiotic nature, the coral-dwelling worm snail of the present study cannot be confused with previously reported Caribbean species, such as the reef-building Petaloconchus varians (d'Orbigny, 1839) in Venezuela [5] and Brazil [25]. The invasive vermetid Eualetes tulipa (Chenu, 1843) has also been recorded in the West Atlantic and the Caribbean, but its operculum is much darker than that of our specimens and it has not been reported as a coral symbiont but as colonies on rock and artificial substrate [26,27].…”

Relative sea-level curve during the Holocene in Rio de Janeiro, Southeastern Brazil: A review of the indicators - RSL, altimetric and geochronological data

“…According to Laborel (1986), vermetid populations disappear or decrease on the rocky coasts south of Cabo Frio, Rio de Janeiro. However, the occurrence of P. varians elsewhere in southeastern Brazil, at the Anjos cove in Arraial do Cabo and at the Ilha Grande Bay, further south, both in Rio de Janeiro State is well documented (Spotorno-Oliveira et al, 2016;Breves-Ramos et al, 2017). P. varians fossil assemblages were identified from the lower middle to the upper middle coastal zone (Spotorno-Oliveira et al, 2016).…”