The genus Cymatocylis in the Southern Ocean: Monospecific or the most diversified one?

ALDER V.A.

Curitiba, Brasil

Simposio; IX SCAR Biology Symposium: Evolution and biodiversity in Antarctica; 2005

SCIENTIFIC COMMITTEE ON ANTARCTIC RESEARCH

Cymatocylis is one of the most relevant tintinnid genera within Antarctic waters due to both its contribution to the microzooplanktonic fraction in numbers and biomass, and its ample spatial and temporal distribution. From the taxonomic point of view, however, it is still not possible to precise whether the genus is monospecific (as suggested by previous studies) or, contrarily, the most diversified one. A taxonomic revision (based on the counting and measurement of  >10 morphometric parameters in >5000 individuals) made on materials collected in the Weddell Sea, Bellingshausen Sea, Drake Passage and Bransfield Strait during Summer and Winter, allowed differentiating two groups of “species” within this genus: 1) C. nobilis, C. drygalskii, C. convallaria and C. antarctica; 2) C. vanhoffeni and C. kerguelensis. The morphological continuity among the species of Group I prevents defining whether they are independent entities. Species belonging to Group II are characterized by their striated lorica (both the shortest and largest ones within the genus) and their prevalence in Winter. Should Cymatocylis be indeed a monospecific genus, then tintinnid specific richness in the Southern Ocean would be 50% less than previously suggested. This taxonomic uncertainty might be extensive as well to other planktonic protists, such as dinoflagellates.