Ascidiacea (Chordata: Tunicata) do Golfo do México

Abstract

Ascidians are benthic invertebrates that inhabit virtually all marine ecosystems. These organisms are interesting bioindicators for the monitoring of environmental disturbances, especially due to the sessile life habit during adulthood. One of the regions under strong anthropic influence is the Gulf of Mexico, home to the largest number of oil and gas extraction platforms in the world, with eight major oil spills occurring in the last decades. The ascidians from the Gulf of Mexico has been registered through several studies and specimens in natural history museums, and assessing those records may real important changes occurred in the faunal composition of this region. The most recent accident in the Gulf of Mexico occurred on April 20, 2010, where a ruptured duct connected to the Deepwater Horizon semi-submersible rig caused the largest accidental oil spill in US marine regions. As part of the Deepwater Horizon leakage monitoring project, ascidians were collected off the west coast of Florida (U.S.A.) in May 2012. Through the analysis of the ascidians collected during this monitoring and also through the verification of part of the specimens acquired in the 1960s during the Hourglass cruises, 242 samples belonging to the three orders of the Ascidiacea class were examined. A total of 56 species that make up the fauna of ascidians of the Gulf of Mexico was identified, distributed in eleven families. Considering this result, we can observe that the organisms registered in the present study represented 38% of the ascidians already registered for this area. In addition, 16 species unknown to occur in the Gulf of Mexico were identified, representing about 29% of the ascidians listed here, being: Ascidia aff. corallicola, Ascidia cf. munda, Ascidia xamaycana, Ascidia sp., Clavelina sp., Exostoma sp., Aplidium sp., Lissoclinum perforatum, Didemnum galacteum, Didemnum sp. 1, Didemnum sp. 2, Didemnum sp. 3, Trididemnum sp. 1, Trididemnum sp. 2, Molgula sp. and Metandrocarpa sterreri. Hence, despite the many works already done in the region it is still possible to observe new records and possible new species in the study area. Based on the various bibliographical references and online database, the temporal assessment of ascidians records in the Gulf of Mexico was also carried out. This work presents the description of all species recently collected, along with an identification key suitable for use in the study area.