Ref ID : 1576
M.J. McElhone; Some factors influencing the diet of coexisting, benthic, algal grazing Naididae (Oligochaeta). Can.J.Zool. 58:481-487, 1980
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A population of Chaetogaster diastrophus which lived in the periphyton on the surface of slates in the shallow, littoral zone of Llyn Llygeirian ingested longer diatom cells than those found in the periphyton and in the gut of the co-occurring naid, Nais pseudobtusa, Chaetogaster diastrophus preferentially ingested diatom cells with large volumes. Seasonal changes in the volume of Cymbella cells in the periphyton influenced whether C. diastrophus ingested greater numbers of either Cymbella or Navicula cells. In the spring of 1976, as the population density of C. diastrophus and N. pseudobtusa increased, the number of diatom cells in the gut of both species decreased and the number of individuals of C. diastrophus with empty guts increased. Chaetogaster diastrophus also ingested a larger number of green unicellular algae cells in response to an increase in density of the corresponding cells in the periphyton. The proportion of detritus and mineral particles in the gut was greater at high densities of C. diastrophus. Populations of C. diastrophus and N. pardalis in Llyn Coron reached peak densities of 5800 m-2 and 10,000 m-2 respectively in the summer of 1975. At low worm population densities in February, C. diastrophus ingested large numbers of Navicula cells, whereas the gut contents of N. pardalis consisted mainly of detritus and diatoms. In June when population densities were higher, the guts of both species were empty.