Nematopsis marinus n. sp., a new septate gregarine from cultured penaeoid shrimp Litopenaeus vannamei (Boone), in Ecuador

The septate gregarine Nematopsis marinus n. sp. (Apicomplexa: Cephaline) heavily infected the midgut of cultured Pacific white shrimp Litopenaeus vannamei (Boone) in Ecuador. It is morphologically similar to other species of the genera Nematopsis, but it can be distinguished from them, by having gamonts with a prominent hemispherical protomerite that contained numerous refractile granules and unusual strong gliding movement. There is evidence that shrimp acquired the infection in the ponds, as larval or postlarval stages do not showed infection. Juveniles and adult shrimp had a prevalence and intensity of infection ranging from 50% to 80% and 10 to > 5000 parasites respectively. When voided from the gut, the gregarine keep alive in seawater. This gregarine have been associated with the marine environment and there are no records of this species in low salinity waters or freshwater. Results suggest that N. marinus could have most of the life cycle of the species within the host L. vannamei.