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Peter Shaw et al.
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Peter Shaw Department of Life Sciences, Roehampton University, Whitelands College,
Holybourne Ave., London SW15 4JD, England;


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Mark Dunscombe


 
Anne Robertson    

 

Collembola in the hyporheos of a karstic river: an overlooked habitat for Collembola containing a new genus for the UK


Abstract

Collembola are well known to occur in soils and litters, as well as inter-tidal habitats, caves and tree canopies, but are not normally thought of as members of the groundwater community. Here we report on studies of the colonisation of gravels in the hyporheic zone under the river Skirfare, a karstic river in Yorkshire. Unexpectedly, flooding during the second experimental run allowed a comparison between low- and high-flow conditions. Five species of Collembola were found in permanently saturated habitats 30 cm below a river bed. One of these species, Hymenaphorura nova, is the first record of its genus in the UK, and appears to be a groundwater specialist. The other named species (Anurida granaria and Mucrosomia (= Cryptopygus) garretti), Deuteraphorura cebennaria (= D. inermis) have wider distributions but are often associated with mines and caves; D. cebennaria is known to occur in the Scoska cave, whose waters feed into the Skirfare shortly upstream of the experimental location. There was some evidence of differences between dates (more first instars and fewer adults after the flood) and between sediments (adults found mainly in coarser materials, first instars in finer sediments), but the statistical significance was weak (0.1 > p > 0.05). The distribution of animals was not clumped (as is typical for Collembola) but followed a Poisson distribution, suggesting it to be primarily random. These results agree with previous authors who suggested that several species of Collembola may live for prolonged periods wholly submerged. The random distribution and their water-repellent cuticles suggest a model of eggs or early instars being washed underground following groundwater, surviving underwater for prolonged periods. We do not have evidence that these Collembola are able to complete their life cycle underwater.

Keywords

Collembola, hyporheic, interstitial fauna


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