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 巴西海洋软体动物类群中，腹足纲（Gastropoda）与双壳纲（Bivalvia）已有较为充分的研究积累，但针对多板纲（Polyplacophora）的相关资料仍较为匮乏，其中栖息于礁体环境的类群尤为不足。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纲类群及其与大型藻类的关联开展定性与定量分析。研究区域涵盖伊皮奥卡（Ipioca）、普雷戈角（Ponta do Prego）、梅里姆角（Ponta do Meirim）、多斯河（Riacho Doce）与绿角（Ponta Verde）共5处珊瑚礁，以及位于瓜苏马（Guaxuma）和塞雷亚（Sereia）的2处砂岩礁。样本采集工作于2009年至2011年的低潮时段开展，通过浮潜沿潮间带与潮下带礁区进行，最大采样水深达5米。此外，本研究还依托1998年夏季至2009年冬季共计12年的采集样本，对绿角珊瑚礁上与3种大型藻类相关联的石鳖进行了针对性研究。研究人员从脆枝叉珊藻（Amphiroa fragilissima，红藻门（Rhodophyta））、长茎葡萄蕨藻（Caulerpa racemosa，绿藻门（Chlorophyta））与鹿角网地藻（Dictyota cervicornis，褐藻门（Phaeophyta））这3种大型藻类藻体上，各采集3组重复样本，每组样本面积为25平方厘米。本次研究共鉴定出715个个体，其中幼体110个、成体605个，涵盖特蕾莎棘石鳖（Acanthochitona terezae Guerra, 1983）、条纹毛肤石鳖（Ischnochiton striolatus (Gray, 1828)）及栉形异毛石鳖（Ischnoplax pectinata (Sowerby II, 1840)）。其中特蕾莎棘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关联类群中丰度最高的物种；三种多板纲类群（成体与幼体）的总个体数在脆枝叉珊藻藻体上最多。