The life cycle of Myxobolus lentisuturalis (Myxozoa: Myxobolidae), from goldfish (Carassius auratus auratus) involves a raabeia-type actinospore.

We studied a natural infection of the oligochaete Branchiura sowerbyi Beddard, 1892 with the Raabeia-type actinosporean stage of Myxobolus lentisuturalis Dyková, Fiala et Nie, 2002 which infected goldfi sh Carassius auratus auratus (L.) in Italy, using molecular analysis of the SSU rRNA gene. The existence of intraoligochaete development shows that this parasite follows the lifecycle pattern described by Wolf and Markiw (1984) for Myxobolus cerebralis. Histological examinations of the goldfi sh infected by M. lentisuturalis showed at low magnifi cation the presence of two bilateral crescent-shaped masses in the dorsal epaxial muscle. These lesions were not circumscribed, presented irregular edges and infi ltrated the underlying bundles of skeletal muscle and interstitial tissue. At higher magnifi cation, disappearance of muscle fi bres and substitution of the muscle tissue with Myxobolus spores and plasmodia were observed.