Petaloconchus (Gastropoda: Vermetidae) reefs as habitat for meiofauna with a focus on free-living nematodes in tropical coasts

The reef-building gastropod Petaloconchus is a critical ecosystem engineer in intertidal zones. Despite the high ecological importance, the fauna of these bioconstructions is virtually unknown worldwide. The present study describes the structure of meiofauna communities in reefs of Petaloconchus in sandstone reefs on the Brazilian tropical coast, highlighting their role in promoting marine biodiversity. Samples were collected at Enseada dos Corais Beach in the dry and rainy seasons. The meiofauna was identified at a high taxonomic level (phylum, order, or class), and nematodes were identified at the genus level. Each Nematoda was assigned a category of cuticle, amphidial fovea morphology, shape of the tail, trophic group, and life strategy. The meiofauna comprised ten groups, with Nematoda being the dominant group (75% of total individuals). The nematofauna comprised 46 genera (dominance of Desmodoridae), in six orders and 19 families. Most nematodes had a punctate or annulated cuticle, a spiral amphidial fovea, and a conical tail, and were epistrate feeders (trophic group 2A) and colonizers (c-p 2). The morpho-functional traits of nematodes are adapted to high-energy environments. The structure of meiofauna and nematofauna communities, as well as the set of morpho-functional traits, varied significantly among seasons. Given the importance and limited knowledge about meiofauna in biogenic reefs worldwide, national, regional, and international legislation must draw attention to these increasingly threatened marine habitats.