Antarctic hexactinellids: A taxonomically difficult, but ecologically important benthic component

• Main Author: Barthel, Dagmar
• Format: Article in Journal/Newspaper
• Language: English
• Published: Deutsche Zoologische Gesellschaft 1992
• Subjects: Antarctic; Rossel; The Antarctic; Antarc*
• Online Access: https://oceanrep.geomar.de/id/eprint/42061/; https://oceanrep.geomar.de/id/eprint/42061/1/Barthel-2.pdf

An introduction to the structure of the Antarctic sponge fauna is given with special reference to the position of the hexactinellida. The history of the taxon Hexactinellida is shortly summarized and the circumstances leading to the insatisfactory phylogenetic and taxonomic knowledge on the group in general are explained. Among the most important problems are discrepancies between the taxonomic criteria used by palaeontologists and neontologists respectively and the scanty availability of specimens. While predominantly confined to the deep sea in most parts of the world, hexactinellids in the Antarctic occur in shallow water as well. Most Antarctic hexactinellids have a circumpolar distribution and they dominate many benthic ecosystems in terms of abundance and biomass. At least three different mechanisms by which hexactinellids influence their environment are recognized today: 1. The large hexactinellids add a three-dimensional structure to a predominantly flat environment. 2. They serve as substrate and living space for a variety of associated fauna. 3. After their death their skeletons persist in the habitat; this can lead to profound changes in the structure of the benthic community. The biology of the species Rossel/a racovitzae, occurring in two different morphological variants with different biology is presented as an example for the need for further taxonomic work on Antarctic hexactinellids.