Diversity of estuarine and marine hydroids (Cnidaria, Hydrozoa) from subtropical ecosystems of Brazil

Abstract

The subtropical coastal waters of Brazil have been surveyed regarding their hydroid fauna since 1941. However, a comprehensive compilation of all hydroid records with detailed information has not yet been published for these waters. Besides filling this knowledge gap, we provide an updated species list, along with the biogeographic status (native, introduced, or cryptogenic) of each hydroid species for the area between Ilha Comprida municipality and the state of Rio Grande do Sul. We also present the distribution patterns of hydroid morphotypes, a sampling sufficiency analysis, and spatial-temporal progress of their research. The dataset was compiled by conducting a thorough bibliographical survey, accessing data of zoological collections, and performing field surveys with experimental settlement panels. This work provides an update for new hydroid records for a large number of localities within the study area. We listed 27 families, 59 genera, 129 morphotypes, and 95 unique species. Regarding the unique species, ~ 3% were classified as introduced, ~ 2% as native, and ~ 95% as cryptogenic. The 3% of introduced species include the first record of the non-indigenous Podocoryna loyola on natural substrata and new records of this species for Sao Paulo. The 95 unique species also represent ~ 19% and ~ 52% of the hydroid fauna recorded in South America and Brazil, respectively. Sampling effort is still not sufficient and therefore continuing research on the hydroid fauna is required, especially for the detection of new introduced species.