Salmonid Whirling Disease: Dynamics of Experimental Production of the Infective Stage — the Triactinomyxon Spore

Abstract

In two trials, spores of the myxosporean Myxosoma cerebralis were added to aquaria containing specific-parasite-free tubificid oligochaetes held at 12.5 °C. After 104–113 d, the tubificids gave rise to and released actinosporean spores of triactinomyxon form, the alternate life stage of M. cerebralis and the initiator of salmonid whirling disease. Production of triactinomyxon spores peaked during days 154–190, and then declined almost as abruptly as it had risen. The triactinomyxon spores were released at trace levels for 9 mo after they first appeared. In a second trial, 26–50 million triactinomyxon spores were produced. The approximate yield from each tubificid was 730–3420 spores. The prevalence of experimentally infected tubificids was about 20%.