The peracarid epifauna associated with the ascidian Pyura chilensis (Molina, 1782) (Ascidiacea: Pyuridae)

Epifaunal peracarids inhabit a variety of biogenic substrata, including ascidians. Herein we examined the peracarid fauna living on the tunica of the sublittoral ascidian Pyura chilensis growing in offshore and nearshore conditions in Bahía San Vicente, Chile. From a total of 38 samples we collected 17 species of Amphipoda, five Isopoda and two Tanaidacea. The similarity between the sites was high (73.8%, Sorensen's index). Species diversity (H') was 2.8 and 2.6, evenness (J) was 0.7 and 0.6 at the offshore and nearshore site, respectively. Both species and individual number increased significantly with the size (volume) of the ascidian samples, and these relationships did not differ between the sites. Many species, in particular the most abundant ones, occurred at both sites, but some species were restricted either to the offshore (three species) or to the nearshore site (seven species). Amphipods and tanaids were the most abundant taxa at both sites. The peracarid fauna at both sites was dominated by suspension-feeding peracarids (>80% of the individuals), which utilize the ascidians primarily as shelter, feeding on allochthonous material, i.e. not originating from the ascidians. It is suggested that the high percentage of suspension-feeding species among the epifaunal peracarids is due to the fact that ascidians settle and grow at sites that provide optimal feeding conditions for these organisms.     

Revision of the genus Peraeospinosus Sieg, 1986 (Crustacea: Peracarida: Tanaidacea)

Ten species, four new to science, five formerly belonging to genus Typhlotanais, and Peraeospinosus pushkini (Tzareva, 1982 Tzareva, L. A. 1982. “Dopolnenie k faune kleshnienosnykh oslikov (Crustacea: Tanaidacea) shelfovykh zon Antarktiki i Subantarktiki.”. In Fauna i raspredelenie rakoobraznych notal'nych i antarkticheskikh vod, Edited by: Kavanov, A. I. 119Vladivostok: Akademia Nauk SSSR.  [Google Scholar]) are congeneric species, based on the following set of characters: a row of setae is present on the dorsal margin of the cheliped carpus, the distal seta of pereopods 4–5 exceeds the bifurcated unguis, large prickly tubercles on pereopods 4–6 surrounded by well‐calcified spines, the pleopods semi‐elliptical, and the rami of the uropod subequal in length. The new definition of the genus is proposed together with a key for identification of the females. The present‐day distribution of the genus does not in itself indicate geographical origin, although the possibility of a deep‐water origin cannot be excluded. It is assumed that phylogenetically young, blind Peraeospinosus could have colonized Antarctic free niches and then radiated.     

A new species of Hyalella from the Patagonia,Chile, with redescription of H. simplex Schellenberg, 1943 (Crustacea: Amphipoda)

The species of Hyalella living in the southern extreme of South America have several common morphological features. The uniqueness of this morphology presents a good argument for inferring phylogenetic relationships among them. The species are concentrated, although not exclusively, in the Patagonia of Chile and Argentina. The group is called here ' patagonica complex'. These species are not the only Hyalella present in the area, however. Hyalella simplex Schellenberg, 1943, with no morphological affinities to the patagonica complex is also present, and is one of the few other species outside the complex living in the continental extreme south of South America. Hyalella simplex is redescribed in this paper. Two species of the patagonica complex have been recorded for the area: H. neonoma Stock and Platvoet, 1991 and H. araucana Grosso and Peralta, 1999. H. fossamancinii Cavalieri, 1959, another species in the complex, is found high in the Andes. The new species H. franciscae described in this work is added to the complex.