A morphometric study of the effects of a mermithid parasite on its host, the Chironomid Midge Einfeldia dissidens (Walker) (Diptera).

Abstract

The modifying effects of a mermithid infestation on the structure of imagines of Einfeldia dissiden (Walker) were investigated by canonical variates analysis, using 11 body measurements as variates. Morphometric changes induced in parasitised hosts were found in both males and females, the most strongly affected characters were measurements of the head and wings. The analysis succeeded in distinguishing between parasitised and normal individuals using leg measurements, although this only accounted for a small proportion of the variability in the data. The two groups of parasitized individuals (genetic males and females) were morphologically indistinguishable, except for the structure of the genitalia by which they were still separable. The modifications are discussed in relation to the changes in behaviour of parasitised individuals and the life cycles of both parasite and host.