Unveiling the diversity of thaliaceans (Chordata, thaliacea) from the South Brazilian Bight and Southern Subtropical Shelf (22°-33°S)

The taxonomic composition of the thaliaceans was analyzed using 86 plankton samples collected in autumn (expeditions: IV = 04/13 to 05/10 2012; VI = 05/09 to 06/12 2013) and spring (expeditions: V = 10/26 to 11/19 2012; VIII = 11/14 to 12/10 2014) on the outer shelf and slope of the South Brazilian Bight and Southern Subtropical Shelf (22 degrees 52 ' 46 '' S-33 degrees 41 ' 28 '' S). More than 61,000 organisms were examined, classified in 3 orders, 4 families, 13 genera and 18 species. Thalia democratica (Forskal, 1775), Doliolum nationalis Boegert, 1893 and Salpa fusiformis Cuvier, 1804 were the most common and abundant species. Doliolina krohni Herdman, 1888 was recorded for the first time in Brazil, Thalia orientalis Tokioka, 1937 was recorded for the first time in the South Brazilian Bight and Brooksia rostrata (Traustedt, 1893) and Soestia zonaria (Pallas, 1774) were recorded for the first time in the Southern Subtropical Shelf. The wide area of the outer shelf and slope sampled in this study revealed the greatest diversity of thaliaceans (similar to 22% of known thaliacean diversity) ever recorded in a faunistic survey in this region of the South Atlantic. The richness estimators, however, did not reach an asymptote and extrapolation showed that the number of species tends to increase as the sampling effort increases.