title: Determination of the effects of temperature on viability, metabolic activity and proliferation of two Perkinsus species, and its significance to understanding seasonal cycles of perkinsosis.
abstract: The range of water temperatures in which Perkinsus species can survive and proliferate remains ill-defined, particularly at lower temperatures. The in vitro viability, metabolic activity, and proliferation of 3 isolates each of P. marinus and P. olseni trophozoites at 28 degrees C, and at 15 and 4 degrees C, after transfer from 28 degrees C, were compared. Both species showed declines in metabolic activity and proliferation from 28 degrees C to 15 degrees C. At 4 degrees C, both species had viability after 30 days incubation time (P. marinus 49%, P. olseni 58%), but limited metabolic activity and no proliferation. Perkinsus marinus viability was further compared when transferred directly from 28 degrees C, 18 degrees C and progressively from 18 degrees C (0.5 degrees C/day) to 2, 4 and 6 degrees C and maintained for up to 4 months. Viability was highest under progressive transfer (77% and 54% after 30 and 60 days exposure to test temperatures). The decrease in P. marinus viability at the lower temperatures in vitro only partially explains decreasing parasite infection intensities in eastern oysters in the colder months of the year. Moreover, the significant decrease in parasite infection intensities in late winter and early spring, as temperatures increase, is likely due to an active process of elimination by oyster host defences.
authors.affiliation: US Geological Survey, Louisiana Fish and Wildlife Cooperative Research Unit, School of Renewable Natural Resources, Louisiana State University Agricultural Center, Baton Rouge, Louisiana 70803, USA.
authors.forename: M K
authors.initials: MK
authors.lastname: La Peyre
authors.forename: S M
authors.initials: SM
authors.lastname: Casas
authors.forename: A
authors.initials: A
authors.lastname: Villalba
authors.forename: J F
authors.initials: JF
authors.lastname: La Peyre
mesh_terms: D000064:Acclimatization / Q000502:physiology; D000818:Animals; D002470:Cell Survival / Q000502:physiology; D003080:Cold Temperature; D049896:Crassostrea / Q000469:parasitology*; D056890:Eukaryota / Q000254:growth & development* / Q000378:metabolism; D016018:Least-Squares Analysis; D010078:Oxazines / Q000378:metabolism; D012621:Seasons; D053058:Trophozoites / Q000254:growth & development / Q000378:metabolism; D014966:Xanthenes / Q000378:metabolism
chemical_list: D010078:Oxazines; D014966:Xanthenes; C005843:resazurin