Antibacterial and antimycotic effect of a newly discovered secretion from larvae of an endoparasitic insect, Pimpla turionellae L. (Hym.)

Abstract

The larvae of Pimpla turionellae, that develop in pupae of various Lepidoptera, discharged through their anus up to 8μl/h of a hyaline liquid, which is termed “anal secretion”. It exerted a strong bacteriostatic effect on Enterobacter cloacae, a highly virulent intestinal microorganism isolated from the midgut of the host pupa, Pieris brassicae. Growth inhibition of Escherichia coli, Micrococcus luteus and Pseudomonas phaseolicola was also evident, but less pronounced. Inhibition depended upon the concentration of the anal secretion. This was also true regarding the effect on growth of Beauveria bassiana, a fungus pathogenic on insects. The antimycotic action of the anal secretion was less effective against Chaetomium pululiferum, a soil-inhabiting fungus. Growing hyphae of B. bassiana were malformed, exhibiting the so-called “curling effect”, when treated with anal secretion. Parenteral injection of a low dosis of Enterobacter cloacae resulted in 100% mortality of non parasitized pupae of Pieris brassicae; however, simultaneous injection of 3μl of anal secretion resulted in higher survival.