Research

Rotifers from selected inland saline waters in the Chihuahuan Desert of México

Elizabeth J Walsh¹ , Thomas Schröder¹ , Robert L Wallace² , Judith V Ríos-Arana³ and Roberto Rico-Martínez⁴

¹Department of Biological Sciences, University of Texas – El Paso, El Paso, TX 79968, USA

²Department of Biology, Ripon College, Ripon, WI 54971, USA

³Instituto de Ingeniería y Tecnología, Universidad Autónoma de Cd. Juárez, Chihuahua, México

⁴Departamento de Química, Universidad Autónoma de Aguascalientes, Aguascalientes, México

author email corresponding author email

Saline Systems 2008, 4:7doi:10.1186/1746-1448-4-7

Published:	4 June 2008

Abstract

Background

In spite of considerable efforts over past decades we still know relatively little regarding the biogeography of rotifers of inland waters in México. To help rectify this we undertook an extensive survey of the rotifer fauna of 48 water bodies in the Chihuahuan Desert of México.

Results

Of the sites surveyed, 21 had salinities ≥ 2000 μS cm^-1 and in these we found 57 species of monogonont rotifers and several bdelloids. Species richness in the saline sites varied widely, with a range in species richness of 1 to 27 and a mean (± 1SD) = 8.8 (± 6.2). Collectively all sites possess relatively high percent single- and doubletons, 33.3 and 21.7%, respectively. Simpson's Asymmetric Index indicated that similarity in rotifer species composition varied widely among a set of 10 sites. These were selected because they were sampled more frequently or represent unusual habitats. These SAI values ranged from 0.00 (complete dissimilarity) to 1.00 (complete similarity). The Jaccard Index varied between 0.00 and 0.35. This observation probably reflects similarities and differences in water chemistry among these sites. Inland saline systems differed in their chemical composition by region. Conductivity was related to hardness and alkalinity. In addition, hardness was positively associated with chloride and sulfate. RDA showed that several species were positively associated with chloride concentration. Other factors that were significantly associated with rotifer species included the presence of macrophytes, nitrate content, oxygen concentration, TDS, latitude and whether the habitat was a large lake or reservoir.

Conclusion

This study illustrates the diversity of the rotiferan fauna of inland saline systems and the uniqueness among waterbodies. Conservation of these systems is needed to preserve these unique sources of biodiversity that include rotifers and the other endemic species found in association with them.