Taxonomy and distribution of Antarctotetilla spp. (Porifera: Tetillidae) from the South Orkney Islands, Antarctica

Antarctic benthic communities are characterized by a high abundance and diversity of sponges, which play a key role in structuring hard-bottom habitats. Within the order Tetractinellida, the family Tetillidae comprises several Antarctic and sub-Antarctic species whose taxonomy has been clarified through recent morphological and molecular studies. There are only five species of Antarctotetilla known worldwide. Here, we report the occurrence of two Antarctotetilla species collected at the South Orkney Islands (Antarctica) during the Argentine Summer Antarctic Expedition. Sampling of the benthic communities was performed in March 2014 aboard the research vessel ARA Puerto Deseado, using a bottom trawl between 290 and 591 m depth. Among sponges, four specimens belonging to the Family Tetillidae were identified at three sampling sites. Identification was based on external morphology, skeletal architecture, and spicules, and corresponded to A. leptoderma (three specimens) and A. sagitta (one specimen). Antarctotetilla leptoderma is a widespread Antarctic and sub-Antarctic species, and the present material represents its second record from the South Orkney Islands. The specimen assigned to A. sagitta represents the first record of this species from the South Orkney Islands, extending its distribution northward (up to 61°25′S). Furthermore, it agrees with the current morphological concept of A. sagitta despite some discrepancies among published descriptions that suggest its taxonomy warrants further revision. The results of the present study are essential for subsequent syntheses and large-scale distributional analyses of Antarctic Tetillid sponges, which rely on the accumulation of occurrence data from multiple local studies that refine our understanding of species distributions, biodiversity patterns, and ecological connectivity among regions.