Abstract
Brazilian marine molluscs, especially Gastropoda and Bivalvia, are relatively well studied. However, information on the class Polyplacophora is more scarce, particularly on reef-dwelling forms. This study aimed to qualitatively and quantitatively analyze aspects of polyplacophorans from reef ecosystems and their associations with macroalgae on the coast of Maceio (state of Alagoas, Brazilian Northeast). The study area included five coral reefs at Ipioca, Ponta do Prego, Ponta do Meirim, Riacho Doce and Ponta Verde, as well as two sandstone reefs, located in Guaxuma and Sereia. The samples were obtained by snorkelling along the intertidal and subtidal reef zones to a depth of up to five meters during low tides, between 2009 and 2011. In addition, the chitons associated with three macroalgae of the Ponta Verde coral reef were studied based on collections made over 12 years (from the summer of 1998 to the winter of 2009). Three replicates with an area of 25 cm2 were collected from each of the following species of macroalgal phytals: Amphiroa fragilissima (Rhodophyta), Caulerpa racemosa (Chlorophyta) and Dictyota cervicornis (Phaeophyta). A total of 715 individuals (110 juveniles and 605 adults) were identified, including Acanthochitona terezae Guerra, 1983, Ischnochiton striolatus (Gray, 1828) and Ischnoplax pectinata (Sowerby II, 1840). Acanthochitona terezae was found for the first time in the area. Ischnochiton striolatus was the most abundant species in the reef ecosystem and in association with macroalgae. The greatest number of individuals of all three polyplacophorans identified (adults and juveniles) was found on the phytal A. fragilissima.
Highlights
The Polyplacophora differ from the other taxa of the phylum Mollusca in that their dorsal shell is formed by eight plates or valves, and the mantle forms a belt around the plates
Three Polyplacophora species were recorded for seven reef ecosystems and for three phytals from one site, along the coast of Maceió
I. striolatus and I. pectinata, which occurred in greater numbers on these reefs, were reported by DENADAI & AMARAL (1999) and AMARAL et al (2006), who considered them to be typical inhabitants of consolidated substrates, and to occur in tropical climates in regions of high temperatures and salinities
Summary
The Polyplacophora differ from the other taxa of the phylum Mollusca in that their dorsal shell is formed by eight plates or valves, and the mantle forms a belt around the plates. 1845) and Ischnoplax pectinata (Sowerby II, 1840) (RIOS & CARDOSO 1967) They were characterized by occasional associations with different macroalgae on the coral reef of Maceió, state of Alagoas, Brazil, compared with other invertebrate groups (SANTOS & CORREIA 1994, 1995, 2001), and only one species was present in shallow reefs on the coast of Paraíba (GONDIM et al 2011). Reef ecosystems on the coast of northeastern Brazil, such as those in the state of Alagoas, have a rich biological diversity (CORREIA & SOVIERZOSKI 2009), including the fauna associated both with seagrasses and macroalgae, with numerous species of molluscs (RIOS 2009), many of which belong to the subclass Opisthobranchia (PADULA et al 2012), some species of Ophiuroidea (LIMA et al 2011, 2013), and many sponges with new species (BISPO et al 2014, CEDRO et al 2011, 2013). This particular class of molluscs is poorly known in the region
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