Observation methods for species in Harpellales using Simuliidae larvae

Abstract

　The fungal parasites Harpellales live in the digestive tracts of aquatic insects. To observe this group, dissection of hosts is required. Dissection methods to obtain digestive tracts of Simuiidae larvae are described. Simuliidae larvae are suitable host insects to study Harpellales because of the following reasons: (i) collection is easy because of slow movement; (ii) larvae are infected with Harpella melusinae in high ratio; (iii) the two families comprising Harpellales (Harpellaceae, Legeriomycetaceae) can be observed in one larva; and (iv) infection-site specificity (a remarkable feature of this order) is shown if both families are observed. To obtain digestive tracts, the head and part of the abdomen at the base of anal gills were transversely cut out. Inner tissue was pinched with forceps and removed. The hindgut and midgut were removed in a line. After dividing the guts, followed by rinsing the contents of each gut in a water droplet on glass slides, each translucent gut was prepared as a separate glass slide. The simplest method to obtain the midgut was to cut out the thorax of the larva. The midgut was expelled by shrinking the abdomen after the incision.