CHARACTERIZATION OF ONE TYPE OF RAABEIA ACTINOSPORE WITH SUBSIDIARY PROTRUSIONS ON THEIR CAUDAL PROCESSES IDENTIFIED IN GIBEL CARP POND

Actinosporea is a synonym of Myxosporea and is the infective stage for fish. This study identifies and characterizes one type of Raabeia actinospore in oligochaete specimen of Branchiura sowerbyi Beddard collected from a fish pond used for rearing gibel carp located in Caidian Experimental Station of the Institute of Hydrobiology. The spore is of characteristic “anchor” shape and without style, possesses a spore body with sporoplasm, 3 polar capsules and 3 caudal processes. Three pyriform polar capsules locate at apex of spore body with equal size (5.2 mm in length and 2.9 mm in width). Spore body shows oblong oval shape on lateral view average with 16.4 mm in length and 9.5 mm in width. Three caudal processes are approximately equal in length and width. Distally, each process possesses subsidiary protrusions which are irregularly distributed. Molecular analyses on 18S rDNA sequences indicate that this Raabeia actinospore type is most closely related to Myxobolus cultus with 98.14% identities, which indicated the type of Raabeia actinospore identified in this study is the counterpart actinosporean stage of Myxobolus cultus.