Bull. nat. Hist. Mus. bond. (Zool.) 67( 1 ): 1-24 



K*£33*U"&-0 



Issued 28 June 2001 







Freshwater nematodes from Loch Ness, 

 Scotland Part I. The orders Tylenchida 

 Thorne, 1949 and Rhabditida Chitwood, 1933 

 (Nematoda, Secernentea). 



JUN 2001 



D 

 siL^rWTY 



F. R. WANLESS AND R. HUNTER* 



Department of Zoology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK 



CONTENTS 



Introduction 1 



Nematode fauna 2 



Materia] and Methods 2 



Abbreviations 4 



Species list 4 



Descriptions of species 5 



Acknowledgements 22 



References 22 



SYNOPSIS. During a survey of the nematodes of Loch Ness. Scotland ( Project Urquhart 1 993-94 ) 94 nematode species were 

 identified from benthic core samples collected from the profunda! (90-2 1 1 m) and from river mouth areas (< 0.5 m). This paper 

 presents a taxonomic review of the nematodes of the two orders Tylenchida Thorne. 1949 and Rhabditida Chitwood, 1933. Thirty 

 five species are described and figured; some morphological features are illustrated by Normarski interference-contrast 

 microscopy. 



INTRODUCTION 



This study is based on nematodes collected in Loch Ness, Scotland 

 during Project Urquhart (1993-94). The first part presented here 

 deals with species that belong in the orders Tylenchida Thorne. 1 949 

 and Rhabditida Chitwood, 1933. The second part, now in prepara- 

 tion, will cover species of the remaining orders. The results of 

 ecological studies (R. David, 1998 - Ph.D. thesis) will be published 

 elsewhere. The following brief profile of Loch Ness is essentially 

 based on the literature Maitland (1981) and Shine & Martin (1987). 

 Loch Ness is the largest body of freshwater in the United King- 

 dom. It runs in a north-east/ south-west direction and is 39 km in 

 length, but only 2.4 km at its widest point with an average depth of 

 132 m. A new maximum depth of 239.5 m was found during a 

 Project Urquhart sonar survey. The loch basin has in most places 

 very steep, sometimes precipitous shelving sides, thus it has a very 

 small shore zone for its surface area Maitland (1981). The flat bed of 

 the loch is divided into two basins of 220 m depth as a result of 

 fluvial deposits of material opposite the entrance to the River 

 Foyers. The floor is extensively covered by black lake sediments 

 which occupies over 50% of the area of Loch Ness greater than 1 50 

 m depth. Shine & Martin (1987) found that a 4 m core only just 

 penetrated to clay, suggesting that the organic sediment is at least of 

 that depth. Sediments analysed from a single core obtained from the 

 profundal area of Loch Ness were found to consist of fine size 

 fractions with clay (< 39 urn, 45.8%), fine silt (39-63 urn, 18.1%) 



and sand (63-125 urn. 36.4%) (Smith B. D. etal, 1981). 



Water levels remain relatively constant throughout the year al- 

 though stream levels vary because of snow melt in spring, but more 

 importantly because of fluctuations in rainfall. The loch has a 

 catchment area of 1775 km : providing 84 m 3 S" 1 mean inflow with 

 the majority of the catchment being rough ground or forest, and only 

 7.5 km : urbanized. Surface water is slightly acidic with an annual 

 mean pH 6.7; it has low conductivity 30 uS cm -1 at 20°C and is 

 stained with humics. Low conductivity levels in lake water are often 

 associated with dark colouration and a high concentration of organic 

 compounds because they have been drained through swampy/peaty 

 regions. The total organic carbon concentrations of the surface water 

 is 3 mg Cl _l Maitland (1981). In many systems of lake classifica- 

 tion. Loch Ness falls within the nutrient-poor Spence (1967) and 

 oligotrophic category Vollenweider (1968). However, Bailey etal., 

 1981 debate whether Loch Ness along with Loch Awe should be 

 described as dystrophic (acid), a category considered by Jarnefelt 

 (1958) as supplementary to. rather than comparable with oligotropic 

 and eutrophic categories. 



The dissolved oxygen content of the Loch Ness water column 

 was, along with other lochs studied, consistently found to be over 

 80% saturated (often approaching 100%) even during periods of 

 stratification Smith, I. R. et al, (1981 ) 



Under the classification system of Yoshimura (1936), Loch Ness 

 is a warm monomictic lake which means that the temperature never 

 falls below 4°C at any depth, there is one circulation of the water 

 column every year in winter and the loch is stratified during the 



'R. Hunter nee R. David. 



© The Natural History Museum, 2001 



