Establishment of medium for laboratory cultivation and maintenance of Fredericella sultana for in vivo experiments with Tetracapsuloides bryosalmonae (Myxozoa)

Abstract

The freshwater bryozoan Fredericella sultana (Blumenbach) is the most common invertebrate host of the myxozoan parasite Tetracapsuloides bryosalmonae, the causative agent of proliferative kidney disease in salmonid fish. Culture media play an important role in hatching of statoblasts and maintaining clean bryozoan colonies for Malacosporea research. We developed a novel culture medium, Bryozoan Medium C (BMC), for the cultivation and maintenance of F. sultana under laboratory conditions. Statoblasts of F. sultana were successfully hatched to produce transparent-walled, specific pathogen-free (SPF) colonies that were maintained >12 months in BMC at pH 6.65. Tetracapsuloides bryosalmonae was successfully transmitted from infected brown trout, Salmo trutta L., to newly hatched F. sultana colonies in BMC, then from the infected bryozoan to SPF brown trout. This study demonstrated the utility of BMC (pH 6.65) for hatching statoblasts, long-term cultivation of clean and transparent bryozoan colonies and maintenance of the Tetracapsuloides bryosalmonae life cycle in the laboratory for molecular genetic research and other studies such as host-parasiteinteraction.

Figure 1

Three-week-old Fredericella sultana zooid, hatched in the laboratory in bryozoan medium C (pH 6.65) (x100).

Figure 2

Clean and transparent laboratory-cultured Fredericella sultana colony, showing tentacles (x40).

Figure 3

Two spore sacs of Tetracapsuloides bryosalmonae (arrows) within a laboratory-infected Fredericella sultana colony (x100).