A comparative study of populations of Ectopleura crocea and Ectopleura ralphi (Hydrozoa, Tubulariidae) from the Southwestern Atlantic Ocean.

Ectopleura crocea (L. Agassiz, 1862) and Ectopleura ralphi (Bale, 1884) are two of the nominal tubulariid species recorded for the Southwestern Atlantic Ocean (SWAO), presumably with wide but disjunct geographical ranges and similar morphologies. Our goal is to bring together data from morphology, histology, morphometry, cnidome, and molecules (COI and ITS1+5.8S) to assess the taxonomic identity of two populations of these nominal species in the SWAO. We have observed no significant difference or distributional patterns between the so-called Brazilian E. ralphi and Argentine E. crocea for both morphological and molecular data. Therefore, SWAO populations of Ectopleura belong to the same species. In a broader view, it is difficult to find decisive character distinguishing E. crocea from E. ralphi, and both species have indeed recently been synonymized, with the binomen E. crocea having nomenclatural priority. Geographically broader genetic analysis should be carried out in order to test the validity of this synonymy because taxonomical procedures such as studying type specimens and documenting broad phenotypic variability have not yet been conducted.

Correction: Macroscale abundance patterns of hydromedusae in the temperate Southwestern Atlantic (27°-56° S).

[This corrects the article DOI: 10.1371/journal.pone.0217628.].

Macroscale abundance patterns of hydromedusae in the temperate Southwestern Atlantic (27°-56° S).

Gelatinous organisms are crucial components of marine ecosystems and some species imply social and economic consequences. However, certain geographic areas, such as the temperate Southwestern Atlantic (SWA, 27° - 56° S), remain understudied in terms of jellyfish ecological data. We analyzed 3,727 plankton samples collected along ~6.7 million km2 over a 31-year period (1983-2014) to determine the occurrence, abundance, and diversity patterns of hydromedusae in the SWA. Analyses were made at both community and species levels. Two abundance hot spots of hydromedusae were identified, where values up to 2,480 ind. m-3 were recorded between 2003 and 2014. Liriope tetraphylla and Obelia spp. were the main responsible for recurrent peaks. Diversity indexes were in the range of those published for temperate areas worldwide, and some coastal zones showed values that can be considered moderate to high for a temperate neritic region. The community analysis yielded 10 groups following previously determined biogeographic schemes throughout the study area. This work enhances the knowledge of hydromedusae in the SWA and provides essential information about the current global warming context and the gelatinous zooplankton data necessity.

Areas of endemism in the Southwestern Atlantic Ocean based on the distribution of benthic hydroids (Cnidaria: Hydrozoa).

Geographic distributions of 130 species of benthic hydroids were used to infer areas of endemism in the Southwestern Atlantic Ocean (SWAO, between 22°S and 55°S). Endemicity Analysis (EA) was carried out with the software NDM VNDM, using a 2° x 2° grid with different values of F (F = 0.5 and F = 1.0) for inferred presence. Hypothesized areas of endemism (16 with F = 0.5 and 13 with F = 1.0) formed three generalized patterns: (1) Tropical, (2) Subtropical, and (3) disjunctions along Tropical and Subtropical areas. Areas of endemism estimated here were compared with provinces, ecoregions and areas of endemism previously defined (but not based on algorithmic analysis) in the literature. Ecological and historical aspects that are potentially relevant for the SWAO realm were contrasted, related and discussed to areas of endemism. This is the first study to apply NDM VNDM to the marine realm and one of the few that focuses on the SWAO.