Pathogenicity of Allantonematidae (Nematoda) infecting bark beetles (Coleoptera: Scolytidae) in Manitoba

Abstract

Histological examination of pathogical changes caused by allantonematid nematodes infecting bark beetles was conducted using beetles collected from Nopiming Provincial Park and Belair, Whiteshell, and Agassiz provincial forests in Manitoba. Nematodes were classified into three groups according to the pattern and nature of damage caused to their hosts. Sulphuretylenchus (three species) induced the earliest and most dramatic changes in their hosts, affecting fat body integrity and ovary and sperm development, and causing massive damage to muscles throughout the body. A Parasitylenchus species induced less severe damage, affecting ovarian development and causing tissue damage only after numerous juvenile nematodes had been released by parasitic females. Neoparasitylenchus, Allantonema, and Contortylenchus caused gradual depletion of fat body reserves, and only minor tissue damage was caused by juvenile nematodes. The degree of pathological change was related to the timing of infection and release of juveniles by parasitic females and to the relative abundance of juveniles present in the haemocoel. Bark beetle species infected by Sulphuretylenchus constructed aberrant galleries, coincident with tissue degradation caused by juvenile nematodes.