Xylotrophic bivalves associated with sunken wood in the deep Southwestern Atlantic

• Ano de defesa: 2024
• Autor(a) principal: Carvalho, Guilherme Siqueira Toledo de
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: filogenia; MicroCT; micromollusks; micromoluscos; phylogeny; Xilophagaidae; Xylophagaidae
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/21/21134/tde-01042025-143957/

The deep sea represents the largest ecosystem on Earth and contains high biodiversity, despite the scarcity of energy resources. However, large amounts of organic matter, such as wood, sporadically sink to great depths and are rapidly colonized by a group of xylophagous bivalves in the family Xylophagaidae. Acting as ecosystem engineers, they transform it into a more labile source of nutrients and help create a distinct, diverse and rarely studied habitat. The aim of this thesis was to analyze the composition of these bivalves at the Southwestern Atlantic, an understudied basin, analyze possible discrepancies with their morphology and colonization patterns, and assess the efficiency and potential hurdles of traditional morphoanatomical methodology and x-ray microcomputed tomography, a novel and non-destructive technique. To obtain the specimens, an autonomous structure called lander was used, containing wooden blocks of different sizes and species, being deployed 240 km off Santa Catarina, Brazil, at a depth of 550 m for ten months. After their recovery, the wooden blocks were then sorted and, according to their relevant morphological characteristics, were identified using light and scanning electron microscopy (SEM). We found three different species from three different genera never previously reported for the Southwest Atlantic, each represented by hundreds of individuals: Xylonora and Xylopholas, and another third species, belonging to a probable new genus, currently under description. High diversity of xylophagaid genera in the region could be possibly related to the existence of extensive forests and river tributaries along the Brazilian coast. Through MicroCT scans, we also could infer growth rates and wood colonization stages. Adapting current protocols and methodology, alongside developing novel ones could be paramount for a first step towards integrative solutions in deep-sea taxonomy and ecology.