The genus Milnesium Doyère, 1840 (Tardigrada) in South America with descriptions of two new species from Argentina and discussion of the feeding behaviour in the family Milnesiidae.

Milena Roszkowska,Łukasz Kaczmarek,Marta Ostrowska

doi:10.1186/s40555-014-0082-7

Milena Roszkowska, Łukasz Kaczmarek + Show 1 more

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https://doi.org/10.1186/s40555-014-0082-7

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Abstract

The diversity and distribution of the tardigrades in South America are rather poor and selective, as is information about their feeding behaviour and diet. To date, only ca. 210 tardigrade taxa have been reported from the region of South America. In the present paper, we provide an update of the distribution of the genus Milnesium inSouth America and discuss some aspects of the feeding behaviour in the family Milnesiidae. In seven moss samples collected in the Argentinean province of Río Negro, 31 specimens, 4 exuviae and 32 eggs belonging to the genus Milnesium were found. Among them, four species were identified: Milnesium argentinum sp. nov., Milnesium beatae sp. nov., Milnesium brachyungue and Milnesium granulatum. By its dorsal sculpture,M.argentinum sp.nov. is most similar to M.beatae sp.nov., Milnesiumbeasleyi andMilnesiumberladnicorum, butit differs from M.beasleyi andM.berladnicorum mainlyby having a different claw configuration and from M. beatae and M. beasleyi by having stylet supports inserted in a more caudal position and by some other morphometriccharacters. In the width of its buccal tube and the claw configuration [3-3]-[3-3], M.beatae sp.nov. is most similar to Milnesiumbohleberi,M.brachyungue andMilnesiumeurystomum,but it differs from them mainly by having a sculptured dorsal cuticle and by some other morphometric characters. The study discusses distribution and taxonomic problems of the Milnesium species known from South America. As of now, nine Milnesium taxa are known from this region (including two new species reported in this paper). Additionally, the study broadens our knowledge of tardigrades' feeding behaviour, provides some details about their diet and suggests that the type of prey chosen by some species belonging to the family Milnesiidae may be associated with the width of their buccal tube.

Highlights

The diversity and distribution of the tardigrades in South America are rather poor and selective, as is information about their feeding behaviour and diet
We strongly suggest that all specimens reported as M. tardigradum s. s. from this region should be re-examined and determined based on the modern taxonomic characters
The majority of the newly described species are known only from their type localities and Michalczyk et al (2012a,b) hypothesised that M. tardigradum s. s. is not a cosmopolitan species, but previous reports from various localities should be re-examined in light of new taxonomic characters because they probably belong to different species

Summary

Introduction

The diversity and distribution of the tardigrades in South America are rather poor and selective, as is information about their feeding behaviour and diet. South America, with an area of almost 18 million km, is located mostly in the Southern Hemisphere, with a relatively small portion Roszkowska et al Zoological Studies (2015) 54:12 largest in Latin America. It is subdivided into 23 provinces and one autonomous city - Buenos Aires. The exceptionally diverse climate depends on the geographic regional division and ranges from tropical in the north to subpolar in the far continental south (Edwards 2008)

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