Carnivorous sponges (Porifera, Cladorhizidae) from the Southwest Indian Ocean Ridge seamounts

Abstract

The family Cladorhizidae (Porifera) comprises a particularly interesting group of sponges that has developed a carnivorous feeding strategy unique within the phylum. Cladorhizids are typically considered deep-sea sponges, are frequently found at oceanic ridges and seamount systems, and new species are continuously discovered as new areas are explored.In this study we describe nine new cladorhizid sponges collected on three seamounts of the Southwest Indian Ocean Ridge (SWIOR) during the RRS “James Cook” cruise JC066: Abyssocladia boletiphora, Ab. corniculiphora, Ab. hemiradiata, Asbestopluma (Asbestopluma) unguiferata, As. (A.) jamescooki, As. (A.) laminachela, As. (A.) pseudoisochela, As. (A.) ramuscula and Chondrocladia (Meliiderma) rogersi; and re-describe four species, viz. Ab. symmetrica, Ch. (M.) stipitata, Cladorhiza moruliformis and Cl. tridentata collected during the “Challenger” expedition in the Southwest Indian Ocean. Barcodes and a phylogenetic analysis showing the systematic position of the new species are included as additional information.Our results show that the cladorhizid fauna of the Southwestern Indian Ocean is diverse and seems to be bathymetrically structured with no observed overlap between the newly reported upper bathyal species (~1000m) and previously described lower bathyal and abyssal species from the area. While the upper bathyal SWIOR species are unique and represent a regionally endemic cladorhizid fauna, similarities in morphology and spicule characters as well as molecular evidence suggests biogeographical affinities to species from the SW Pacific and SW Atlantic, but no similarities to previously reported Antarctic fauna were found. A table of cladorhizid species from the Southwest Indian Ocean and neighboring areas is provided.