Is the worm-like organism found in the statoblasts of Plumatella fungosa (Bryozoa, Phylactolaemata) the vermiform phase of Tetracapsuloides bryosalmonae (Myxozoa, Malacosporea)?

Tetracapsuloides bryosalmonae is a malacosporean parasite causing Proliferative Kidney Disease (PKD) of salmonids, which develops in a sac-shaped phase producing infective spores in freshwater bryozoans. From 2001-2003, several samples of bryozoans were collected along the Sile River (Treviso Province, northern Italy) from sites which are in close communication with two trout farms where PKD is enzootic. All the colonies found were observed under a stereomicroscope in search of T bryosalmonae and to isolate statoblasts. The bryozoans were classified by studying the superficial microarchitecture of the statoblasts using a scanning electron microscope (SEM). The following species were identified: Cristatella mucedo, Fredericella sultana, Plumatella casmiana, P. emarginata, P. fungosa, P. repens, P. reticulata, R rugosa, and F similirepens. Developmental stages of T bryosalmonae were never found in the colonies. In 11 out of 40 R fungosa floatoblasts, treated with KOH for SEM study, vermiform structures of 0.5-8 mm in length were observed. The possibility that these structures could represent the vermiform phase of T bryosalmonae with a developmental stage similar to those described for Buddenbrockia plumatellae is discussed.