Amoebae were found to cause severe gill tissue damage in turbot, Scophthalmus maximus L. from a grow-out facility in northwestern Galicia (Spain). The nature and extent of lesions along with negative results of bacteriological and virological examination made this agent responsible for mortalities in four turbot stocks supplied with water from a single source. We present our findings, although we failed to isolate amoebae, since there was a clear evidence of their primary role in the development of disease condition and occurrence of mortalities. In addition, this is a record both of a new host endangered by amoebae in intensive cultures and pathogenesis of the gill lesions.
Six young tortoises Testudo marginata Schoepff, 1792 were experimentally infected with Hemolivia mauritanica (Sergent et Sergent, 1904). The prepatent period ranged from 6 to 8 weeks. Young, smaller, club-like forms (6-9 × 3-6 µm) of gametocytes appeared in the peripheral blood first, whereas mature, elongated, cylindrical forms (9-12 × 5-7 µm) were detected after 1-2 weeks and predominated during later patency. Three of the infected tortoises were euthanized and dissected to study the endogenous stages. Meronts occurred in the cells of the reticulo-endothelial system and in the erythrocytes; these were observed mostly in parenchymatous organs. Mature forms measured 14.2 × 9.3 µm and contained 7-12 merozoites. Cysts with two (exceptionally one) cystozoites were also found predominantly in parenchymatous organs and measured 14.8 × 7.9 µm. Pathological changes attributable to Hemolivia were mild and limited to liver and kidneys. The role of individual developmental stages of haemogregarines is discussed with respect to evolution of heteroxenous life cycle and long-term persistence of parasites in their intermediate hosts.
Ileterosporous (polymorphic) microsporidia in mosquitoes are characterized by intricate life cycles involving multiple spore types responsible for horizontal (per os) and vertical (transovarial) transmission. They affect two generations of the mosquito and some involve an obligate intermediate host. Heterosporous microsporidia are generally very host and tissue specific with complex developmental sequences comprised of unique stages and events. Full details on the intricate relationships between heterosporous microsporidia and their mosquito hosts have only recently been elucidated. Edhazardia aedis (Kudo, 1930) and Culicospora magna (Kudo, 1920) have developmental sequences in larvae that involve gametogony followed by plasmogatny and nuclear association to form diplokarya. These diplokaryotic stages then undergo karyogamy and form binucleate spores responsible for transovarial transmission. In the filial generation, haplosis occurs as a result of nuclear dissociation to produce uninucleate spores infectious to larval mosquitoes. Amblyospora cali-fornica (Kellen et Lipa, 1960) has similar sequences except that haplosis is by meiosis to produce spores infectious for a copepod intermediate host. A third spore type is formed in the intermediate host responsible for infection in a new generation of the mosquito host.
Neopolystoma liewi sp. n. is described from the conjunctival cavity of the Malayan box turtle Cuora amboinensis (Daudin, 1802), in Peninsular Malaysia, This is the first record of Neopolystoma in Malaysia and the fourth polystomatid species described from C. amboinensis. Of the 27 Malayan box turtles examined, 8 were found to be infected. A maximum of 2 parasites per eye and 4 individuals per host was recorded. N. liewi sp. n. differs from all other members of the genus by possessing few and short genital spines and small marginal hooks. The oncomiracidium has 64 ciliated cells arranged symmetrically about the sagittal axis.