Fungal self-parasitism in Saprolegnia megasperma

Abstract

The phenomenon of self-parasitism in the aquatic phycomycetes has apparently been overlooked since it was first mentioned in the work of Klebs in 1899. This study documents fungal self-parasitism for the first time in Saprolegnia megasperma Coker (isolate 369A). The 369A isolate was grown for 48 h at 16 °C in shake cultures of a medium containing glucose, lactalbumin hydrolysate, phosphate, and micronutrients. The resulting vegetative growth was then transferred to shake-and-standing flasks at 16 °C and standing flasks at 4 °C containing either a dilute salts solution or double-distilled water to enhance the formation of both sexual and asexual structures. The results in both shake and standing cultures were comparable. When oogonia were produced in the absence of antheridial branches, the oospheres developed into normal oospores. When an antheridial branch was produced, an antheridial cell was never observed and the branch penetrated the oogonium via a pit and destroyed all or some of the oospheres (oospores?). This parasitic antheridial branch could reemerge from an oogonium via a pit and penetrate additional oogonia. The possible implications of self-parasitism for the relationship between S. megasperma and Saprolegnia unispora (Coker and Couch) Seymour are discussed.