The distribution and abundance of tardigrades in the city of General Pico (Argentina) are analyzed from samples collected during autumn and spring 2001. Sample sites included paved urban locations with different traffic intensities, non-paved periurban places, and places with peculiar conditions such as the city industrial area and the bus station. Trees of the same species were selected in each area and from each of them nine subsamples of lichens and/or moss, 11 mm in diameter, were taken with steel corers. The diversity, density and relative abundance of tardigrades was recorded and analyzed. Sampling sites were ordinated and classified with PCA and clustering. The number total of species collected in the research was 5. The maximum number of species per site and per tree was 4. The species recorded were: Echiniscus rufoviridis, Milnesium cf. tardigradum, Ramazzottius oberhaeuseri, Macrobiotus areolatus and an undescribed species of the genus Macrobiotus. The average density was approximately 10 specimens per cm 2 and the maximum values reach over 50 specimens per cm 2 . R. oberhaeuseri and M. cf. tardigradum were the most frequent species. R. oberhaeuseri dominates in periurban areas with high suspension dust and very exposed to the sun. M. cf. tardigradum dominates on paved streets with intense vehicle traffic. Results supported the hypothesis of the relationship between air quality and tardigrade diversity.

The type-specimens of Parspina argentinensis (Szidat, 1954) from Pimelodus maculatus Lacépède, and new material from Iheringichthys labrosus (Lütken), Parapimelodus valenciennis (Lütken), Pimelodella gracilis (Valenciennes), Pimelodus albicans (Valenciennes), P. argenteus Perugia and P. maculatus caught in the basins of the La Plata and Paraná Rivers, Argentina, were studied to elucidate its taxonomic status. The type-specimens of Parspina bagre Pearse, 1920 from Pimelodella metae Eigenmann in Lake Valencia, Venezuela, were also studied and new observations on its morphology recorded. The amendation of the generic diagnosis of Parspina Pearse, 1920 is proposed based on the study of both species, which revealed, among other features, the absence of a thin walled-membrane enclosing the male terminal genitalia. Parspina argentinensis is characterised by the following features: absence of a gonotyl; presence of a bipartite seminal vesicle, pars prostatica and ejaculatory duct; caeca of nearly equal length; uterus extending from the level of the ventral sucker to end of body; testes symmetrical to slightly oblique; ovary transversely elongate, compact and variable in shape; and the utilisation of a wide range of freshwater fishes as hosts. The tegumental surface of this species is covered with pectinate spines arranged quincuncially. Spines decrease in size and density from forebody to hindbody. There are two types of sensory papillae, ciliated and dome-shaped. Ciliated papillae are distributed on the surface of the oral region and on the dorsal and ventral surfaces of the body, whereas dome-shaped papillae are found on the surface of the ventral rim of the oral sucker associated with a ciliated papilla. Gland-duct openings are interspersed with the spines of the oral crown. In addition, the infection indices of P. argentinensis vary widely, not only among different hosts but also between the Paraná and La Plata River basins. Higher prevalences of P. argentinensis are recorded in the La Plata River, and Pimelodus albicans, P. maculatus and Iheringichthys labrosus are the principal final hosts in this area.

Argentine tardigrades are relatively unknown and, in many cases, unstudied; in the province of Salta in northwestern Argentina the lone record of tardigrade dates to the 1980s. Here, we evaluate and compare tardigrade diversity in natural habitats (N), urban environments (U) and rural communities (R) of Yungas. This work seeks to verify the existence of a reduction in tardigrade diversity outside their native habitats and if there is a biotic homogenization in the urban communities. Tardigrade community assemblages were compared between habitats using non-metric multidimensional scaling and a multi-response permutation procedure. Beta diversity was analysed in its component parts, species turnover and nesting, using a modified Raup-Crick test. Gamma diversity was divided into alpha and several beta levels. In total, 2080 eutardigrade and heterotardigrade specimens were registered and showed differences in tardigrade assemblages between habitats; the most diverse habitat was R. The beta diversity partition showed a nesting pattern in the U communities, highlighting faunal homogenization, while species turnover was key in the R and N communities. There was species loss from N to U communities, most markedly between R and U; various forces (both stochastic and deterministic) influence the structure of these communities.

RESÚMEN Este trabajo se realizó bajo la hipótesis de que existe una pérdida creciente de diversidad en las comunidades de tardígrados, desde las áreas rurales hacia las urbanas, incrementando la homogenización de sus comunidades producto de la urbanización. Para la ciudad de Salta, se tomaron muestras en áreas con tránsito vehicular alto y muestras en áreas rurales circundantes. Se identificaron en total ocho especies/morfoespecies. El inventario tuvo una completitud mayor al 94%. La comunidad rural fue más diversa y estructuralmente más uniforme que la comunidad urbana. Macrobiotus hufelandi Schultze, 1834 resultó especie indicadora y Milnesium sp. como detectora para el hábitat urbano, mientras que Paramacrobiotus areolatus Murray, 1907 resultó indicadora para el hábitat rural.

Limno-terrestrial tardigrades of Argentina had been studied starting in 1908 and for a long time by European researchers, most frequently in the Patagonian region (incl. the Land of Fire). Starting during the 1980s, Claps, Rossi and collaborators published many surveys, studying other regions also, but with taxonomic criteria at that time. Since the 2000s, methodical and continuous studies using more modern criteria, have been carried out at the National University of La Pampa, contributing to the faunistic, taxonomic and ecological knowledge (including new species descriptions). This paper provides a comprehensive list of the limno-terrestrial tardigrade fauna reported from Argentina, with pertinent evaluations, owing to a careful study of every pertinent piece of literature since 1908, also solving some problems of discordance between the main past checklists. Summarizing, 39 genera and 119 species are present; of these, 72 represent records accepted by the literature, while 47 are records questioned in the literature but which represent distinct taxa surely present in Argentina; 14 additional taxa, instead, are clearly dubious. The authors also report the correct genus assignment to Viridiscus rufoviridis (du Bois-Reymond Marcus, 1944), which now becomes Barbaria rufoviridis comb. nov.

Tardigrades from Argentina are poorly known. Two new species from the Salta province are described in the present contribution: Pseudechiniscus saltensis sp. nov., and Doryphoribius cephalogibbosus sp. nov. The former species belongs to the novaezeelandiae group and, apart from the nominal species of the group, it is similar to nine congeneric species by the following characters: the absence of spines on legs I and lateral papillae, the scapular plate with a transversal fold, the presence of projections at the posterior margin of the pseudosegmental plate, caudal plate not faceted, and cuticular ornamentation in the form of heads (capituli) of endocuticular pillars, protruding through epicuticle and joined by striae. However, the new species differs from all of them in important qualitative (e.g. colour, different division of plates, details of cuticular ornamentation, claws etc.) and morphometric characters. The new species exhibits a unique morphology of gonopore and anus. Doryphoribius cephalogibbosus sp. nov., by the presence of two macroplacoids, dorsal gibbosities, and inhabiting terrestrial environment, belongs to the flavus group and differs from all members of the group in having ten, instead of nine, rows of gibbosities (X:2-4-6- 6-6-6-6-4-2-2+2[LI–III]), with as a peculiar exclusive character, the presence of the two cephalic gibbosities, never reported in other Doryphoribius species. Moreover, the new species differs from the other species of the group by morphometric and more detailed morphological characters. The new species description also gave an occasion to discuss the issue of gibbosity arrangement in other species and address the morphology of claw accessory points.

Urban tardigrades are studied little worldwide. In Salta (Argentina), two studies have evaluated their diversity in an urban–native gradient. Vehicular traffic in Salta city has increased over the last decade, increasing environmental pollution. Our aim is to determine whether biotic homogenization occurs in this city. Sampling sites were selected considering different vehicular traffic intensities (high, medium and low). Tardigrades were sampled from bryophytes growing on tree trunks. Specimens were treated according to the usual study methodology. Different biotic and environmental abiotic variables of the microhabitat were considered. A total of 3049 specimens of 16 species of heterotardigrades and eutardigrades were reported. The low vehicular transit habitat was more diverse than the others. Ordination analyses evidenced a nested pattern in the studied urban habitats. Milnesium sp. nov. 3 and Minibiotus sp. nov. 1 were reported as detector species for habitats with medium vehicular traffic. The partition of the β diversity showed that the species turnover was higher among low and high vehicular traffic communities than medium, whereas a loss of species was evidenced between high and medium habitats. The high diversity of tardigrades in Salta city and their assemblages are partly dependent on several factors, including vehicular traffic.

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