Evaluation of malacosporean life cycles through transmission studies

Diseases of Aquatic Organisms

T. S. McDowell¹  B. Okamura¹  D. V. Baxa¹  R. P. Hedrick¹  S. Tops¹ 

关键词: Myxozoa;    Malacosporea;    Proliferative kidney disease;    Freshwater bryozoans;    Transmission;    Potential hosts;    Life cycles;   

DOI  :  10.3354/dao060109

学科分类：生物科学（综合）

来源: Inter-Research

【 摘 要 】

ABSTRACT: Myxozoans, belonging to the recently described Class Malacosporea, parasitise freshwater bryozoans during at least part of their life cycle, but no complete malacosporean life cycle is known to date. One of the 2 described malacosporeans isTetracapsuloides bryosalmonae, the causative agent of salmonid proliferative kidney disease. The other is Buddenbrockia plumatellae, so far only found in freshwater bryozoans. Our investigations evaluated malacosporean life cycles, focusingon transmission from fish to bryozoan and from bryozoan to bryozoan. We exposed bryozoans to possible infection from: stages of T. bryosalmonae in fish kidney and released in fish urine; spores of T. bryosalmonae that had developed inbryozoan hosts; and spores and sac stages of B. plumatellae that had developed in bryozoans. Infections were never observed by microscopic examination of post-exposure, cultured bryozoans and none were detected by PCR after culture. Our consistentnegative results are compelling: trials incorporated a broad range of parasite stages and potential hosts, and failure of transmission across trials cannot be ascribed to low spore concentrations or immature infective stages. The absence of evidence forbryozoan to bryozoan transmissions for both malacosporeans strongly indicates that such transmission is precluded in malacosporean life cycles. Overall, our results imply that there may be another malacosporean host which remains unidentified, althoughtransmission from fish to bryozoans requires further investigation. However, the highly clonal life history of freshwater bryozoans is likely to allow both long-term persistence and spread of infection within bryozoan populations, precluding therequirement for regular transmission from an alternate host.

【 授权许可】

Unknown