The Life Cycle of Sphaerospora truttae (Myxozoa: Myxosporea) and Some Features of the Biology of Both the Actinosporean and Myxosporean Stages

Abstract

A previously undescribed echinactinomyxon type actinosporean was shown experimentally to be the alternate stage of Sphaerospora truttae. The echinactinomyxon type spores were found to be released from Lumbriculus variegatus and occasionally Tubifex tubifex. Overall infection prevalence of the echinactinomyxon was 0.14%. Peak release was in March-May each year. S, truttae spores developed in experimentally infected salmon 4.5 mo post-exposure to echinactinomyxon spores. Extrasporogonic stages of S, truttae first appeared in naturally infected salmon in early July and persisted for 8 to 10 wk. Correlation between peak release of echinactinomyxon spores and appearance of extrasporogonic stages of S. truttae is discussed.