Fine structure of sporogonic stages of Goussia clupearum (Apicomplexa: Eimeriidae) in the liver of infected fish (Belone belone L.), using light and electron microscopy.

A coccidian species, Goussia clupearum (L.) is reported to parasitize the liver of a new host, Belone belone (Teleostei: Belonidae), caught on the Atlantic coast at the north of Portugal. The parasitophorous vacuole containing oocysts was attached to the host's liver cells. Spherical oocysts (approximately 21.2 microm diameter), each containing four ellipsoidal elongated sporocysts (10.5 x 6.3 microm), were enclosed in the parasitophorous vacuole. Each sporocyst contained two sporozoites. The micropyle was absent, but a polar granule (without Stieda body) was present. Each sporozoite possessed four refractile bodies. During sporoblastogenesis and sporogenesis, one or two dense polar bodies were found within the oocysts. They were composed of a dense homogeneous core, surrounded by a ring of dense granular material. On occasion, we observed some sporocysts in direct contact with host cells. This paper describes the morphology and ultrastructural details of the oocysts, sporocysts and sporozoites of G. clupearum. This species seems to represent the only coccidium described in fish from this Atlantic coast.