Hydroid assemblages from the Southwestern Atlantic Ocean (34–42° S)

Abstract

This paper provides updated taxonomic knowledge about hydrozoan species and provides ecological information including geographical and bathymetric distributions and biological substrata for the various hydroid assemblages from the Sub‐Antarctic Biogeographical Region, mainly Buenos Aires and the Uruguayan coasts. Five of the 41 species found are new records for the study region. Thirty‐one species (75.6%), all found at depths of less than 80 m, have cosmopolitan distributions. Biodiversity decreased markedly below 80 m depth, where nine species (≈22%) distributed in the Southern hemisphere and one endemic species (2.4%) were found. Most species were non‐specific epizoites, occurring on diverse substrata. A non‐parametric multivariate similarity analysis revealed nine species groups that were correlated with large‐scale and local oceanographic patterns and with the availability of suitable substrata. The main hydroid substrata for eight of the groups were cnidarians, molluscs (mainly blue mussels), quartzite rocks and sponges. In a single group found in Patagonian scallop beds, the main biological substrata were polychaete tubes, other hydroids and scallops.

Hydroid epifaunal communities in Arctic coastal waters (Svalbard): effects of substrate characteristics

“…About one-third of all hydroid records and 40 % (23 species) of hydroid species are noted on this type of substrate. Bryozoans have often been noted as a substrate colonized by hydroids (e.g., Genzano and Rodriguez 1998;Genzano and Zamponi 2003;Henry et al 2008;Genzano et al 2009); however, no detailed descriptions (such as bryozoan host taxonomic composition) on the epizoic type of associations between hydrozoans and bryozoans are included in these studies. Piraino et al (1992) described the parasitic relationship between the hydroid Halocoryne epizoica Hadzi, 1917, and the bryozoan Schizobrachiella sanguinea (Norman 1868), in which the hydroid lived in obligate association and feeds on the lophophoral tentacles of its bryozoan host.…”

“…Hydroid-hydroid associations are most often noted only briefly in taxonomic and/or ecological studies (e.g., Schuchert 2001;Genzano and Rodriguez 1998;Zamponi et al 1998;Henry et al 2008;Genzano et al 2009). Large colonies of hydroids are known to offer refuge and food supply for deposit feeders and carnivores (Hughes 1975).…”

“…The advantage of colonizing asexually reproducing substrates such as Hydrozoa is the unlimited and permanent growth of new hydrocauli (i.e., the new substrate) and the better access to seston they provide to suspension-feeding animals. A continuously growing substrate can be colonized quickly by epizoic hydroids from neighboring hydrocauli through stoloniferous growth (Genzano et al 2009). Orlov (1997) examined the hydroidhydroid associations closely and identified the morphological plasticity of colonists as an adaptation of hydroids to an epizoic mode of life.…”

“…Both ecological papers and taxonomical revisions frequently report the type of substrate to which hydroids are attached (Naumov 1969;Zamponi et al 1998;Schuchert 2001;Genzano et al 2009). However, detailed analyses of the relationships between substrate characteristics and hydroid diversity or community structure in the Arctic are lacking.…”

First record of the invasive stinging medusa Gonionemus vertens in the southern hemisphere (Mar del Plata, Argentina)

“…In the southwestern Atlantic Ocean, the Hydrozoa fauna have been widely studied in recent decades and its species richness is well known (see Migotto et al, 2002;Genzano et al, 2008Genzano et al, , 2009Rodriguez et al, 2012, and references therein). New species have been recently described (Nogueira et al, 2013), and two invasive species were also discovered.…”