Growth -The asymptotic lengths of individuals of the southern form of P. blainvillei (distributed south of 32ºS) vary between 129.8cm and 136.4cm for males, and between 146.4cm and 161.9cm for females (Kasuya and Brownell, 1979;Walter, 1997;Barreto et al., 2000). The northern form of the species (distributed north of 27ºS), has asymptotic lengths that vary between 113.3cm and 117.1cm for males, and between 128.9cm and 144.7cm for females (Rosas, 2000;Ramos et al., 2000a;Ramos et al., 2000b). These results corroborate the populational differences in body size between the northern (smaller individuals) and southern forms (larger individuals) based on osteological data (Pinedo, 1991) and those from genetic studies (Secchi et al., 1998). These data also suggest populational differences within each of the geographic forms. The asymptotic lengths obtained by Rosas (2000) for franciscanas in an intermediate area (São Paulo and Paraná) of the species distribution were smaller than those close to the northern limit of its distribution (Ramos et al., 2000a). Additionally, the asymptotic lengths presented by Ramos et al. (2000b) from São Paulo were also smaller than those for the more northern Rio de Janeiro coast. The different body sizes observed among the individuals within the northern form might also be due to populational differences, as result of an isolation of the individuals in the northern region of Rio de Janeiro and Espírito Santo (Siciliano et al., 2000).
Worldwide knowledge of tardigrade fauna is still limited, and many areas such as South America are not well studied. The collection of new substrates in Argentinean urban areas provided an opportunity to describe the new tardigrade\ud species Macrobiotus kristenseni sp. nov. This species has been studied with an integrative taxonomic approach, analysing its morphology by light and scanning electron microscopy, and considering two genes (cox1 and 18S rRNA) for DNA\ud barcoding and phylogenetic purposes. The species belongs to the Macrobiotus hufelandi group of species, and it is characterized by egg processes in the shape of elongated cones with truncated and enlarged apexes, and by a high genetic distance with respect to closely related species (cox1: 18.2–33.4%).Morphological and molecular data show that the Macrobiotus hufelandi group of species has to be considered\ud a true biological entity; one of the more widespread tardigrade lineages in continental environments
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.
Du Bois-Raymond Marcus in 1944 on Brazilian specimens, it had not been recorded again. The validity of the species is confirmed, its geographic distribution is extended to Argentine localities and new data are provided on its morphology (optical and SEM) and its bioecology. Echiniscus rufoviridis can be clearly separated from the E. viridis, the closest species within the "viridis group", by the possession of depressions with pores on the surface of the cuticle, instead of papillae. On the other hand, an ecological similarity with E. testudo is proposed. This latter species occupies, albeit with low tolerance, urban environments in Europe]]>
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.
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