HOST-ASSOCIATED BACTERIAL ASSEMBLAGES OF LITTORINIDAE GASTROPODS FROM MANGROVE AND BEACH ECOSYSTEMS ON THE BRAZILIAN SEMI-ARID COAST

Abstract

Gastropods of Littorinidae family are ecologically important in coastal ecosystems, but little is known about the microbial communities associated with these molluscs, particularly in semi-arid tropical regions. This study aimed to characterize and compare the bacterial microbiota associated with three Littorinidae species: Echinolittorina lineolata, Littoraria angulifera, and Littoraria flava collected from two contrasting habitats (beach and mangrove) on the semi-arid coast of northeastern Brazil. A total of 40 specimens were collected and analyzed using culture-based methods followed by automated identification via the VITEK® 2 Compact system. Statistical analyses (PERMANOVA and SIMPER) revealed that host species identity was the main factor shaping microbiota composition (p = 0.001). Significant differences were found between L. angulifera and both E. lineolata and L. flava from beach environment. However, no significant differences were detected between L. angulifera and L. flava from the mangrove. Dominant taxa contributing to microbial dissimilarities included Vibrio alginolyticus, Vibrio fluvialis, Sphingomonas paucimobilis, and Streptococcus iniae, with notable habitat-specific patterns. These findings emphasise the influence of both host identity and environmental conditions on microbiota structure. Species from the same genus but different environments presented distinct microbial profiles, while those sharing the same habitat displayed similarities regardless of taxonomic proximity. These results advance our understanding of host-microbe interactions in marine invertebrates and highlight the potential of Littorinidae species as bioindicators of coastal environmental health.