Molecular affinity of Southwest Atlantic Alvinocaris muricola with Atlantic Equatorial Belt populations

Specialist fauna populations from chemosynthetic ecosystems are connected through larval stages travelling in current highways in the vast deep sea. One shrimp family of such specialists, Alvinocarididae, is hitherto known to be endemic to vents and seeps with no reported occurrence in ephemeral organic-rich chemosynthetic habitats. Here we report the first occurrence of Alvinocaris muricola on experimentally deployed whale bones and wood parcels in the Brazil margin (21 degrees to 26 degrees S) at 1500 and 3300 m depth. We sequenced the COI, 165 and 285 markers for molecular identification of Southwest Atlantic (SWAtl) specimens and used COI sequences to inspect the molecular diversity and genetic distance between the SWAtl and the Atlantic Equatorial Belt (AEB) populations. SWAtl A. muricola exhibited lower nucleotide and haplotype diversities in comparison with populations along the AEB. The low genetic divergence detected here between the SWAtl and AEB populations is likely a result of larval connectivity through equatorial currents from the East Atlantic margin populations, whereas the SWAtl may be supplied through western boundary currents at bathypelagic depths. The occurrence of A. muricola in organic falls suggests the existence of other deep-sea chemosynthesis-based ecosystems in the SWAtl that could function as larval sources to organic islands and vice versa. Our study additionally supports the ecological stepping-stone role of organic falls between vent and seep ecosystems.