Chaloner, Dominic Thomas; (1995) The Role of Particles in Structuring the Midge (Diptera: Chironomidae) Community of Temporary Ponds (slow sand filter beds). Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

This thesis describes an investigation of the possible role of particles in structuring a midge (Diptera: Chironomidae) community associated with slow sand filter beds. A "particle" is defined as an entity greater in size than 0.45 μm in diameter. Particle types found in filter beds include sand, schmutzdecke (detritus) and Cladophora. Larvae use particles to construct tubes and as food; particles, as substratum, can also create potential habitats. Filter beds provide an ideal model system, because they can be emulated in laboratory microcosms and support a limited number of species. Three species were known to dominate a filter bed midge community: Cricotopus sylvestris (Fabricius) (dominant), Psectrocladius limbatellus (Holmgren) (subdominant), and Tanytarsus sp. (subdominant). Laboratory microcosms were used to discover differences in particle use, and therefore evidence of resource partitioning, between larvae of these species. Rearing experiments were also conducted to examine whether larvae of C. sylvestris, responded differently, in terms of larval growth, to different particle regimes, but also the microbial and physical regime associated with filter beds. Differences were found between species in their preferences for certain particle types as substratum, on the basis of type but not size, reflecting the published literature. Subtle differences were also found in the tube-building behaviour of these species. Such differences could be inferred from other studies, but had not been previously considered as a possible mechanism promoting coexistence. Little evidence was found of differences in feeding, which is consistent with the literature. C. sylvestris was also found to exhibit differences in its growth on different particle and microbiological regimes. However, no evidence was found that a vertical through-flow of water, characteristic of filter beds, affected larval growth. This study provides evidence of the importance of particles, especially through tube-building and substratum preferences, in structuring midge communities.

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