Polyplacophora (Mollusca) from reef ecosystems and associations with macroalgae on the Coast of Alagoas, Northeastern Brazil

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 Maceió (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.

摘要：巴西海洋软体动物，尤其是腹足纲（Gastropoda）与双壳纲（Bivalvia）的研究相对较为深入。但针对多板纲（Polyplacophora）的资料相对匮乏，尤以栖息于礁体的类群为甚。本研究旨在对巴西东北部阿拉戈斯州马塞约沿岸礁体生态系统中的多板类动物及其与大型藻类的关联进行定性与定量分析。研究区域涵盖伊皮奥卡（Ipioca）、蓬塔杜普雷戈（Ponta do Prego）、蓬塔杜梅里姆（Ponta do Meirim）、里亚舒杜斯（Riacho Doce）及蓬塔韦尔迪（Ponta Verde）的5处珊瑚礁，以及瓜苏马（Guaxuma）与塞雷亚（Sereia）的2处砂岩礁。样本采集于2009年至2011年的低潮时段，通过浮潜方式在潮间带及潮下带礁区开展，采样深度可达5米。此外，本研究基于1998年夏季至2009年冬季共12年的采样数据，对蓬塔韦尔迪珊瑚礁区域与3种大型藻类共生的石鳖进行了研究。针对以下3种大型藻类藻体生境，各采集3个面积为25平方厘米的重复样本：脆弱叉珊藻（Amphiroa fragilissima，红藻门（Rhodophyta））、总状蕨藻（Caulerpa racemosa，绿藻门（Chlorophyta））与鹿角网地藻（Dictyota cervicornis，褐藻门（Phaeophyta））。本次研究共鉴定出715个个体（其中幼体110个，成体605个），涵盖特蕾莎棘侧石鳖（Acanthochitona terezae Guerra, 1983）、条纹毛肤石鳖（Ischnochiton striolatus (Gray, 1828)）及梳形等齿石鳖（Ischnoplax pectinata (Sowerby II, 1840)）。其中特蕾莎棘侧石鳖为该区域首次记录的物种。条纹毛肤石鳖是礁体生态系统及与大型藻类共生类群中丰度最高的物种。本次鉴定的3种多板类动物（成体与幼体）的总个体数在脆弱叉珊藻的藻体生境中最多。