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Blackwell, W. H., Letcher, P. M., & Powell, M. (2013). An oomycete parasitizing algae occurring on dorsal shells of turtles. Phytologia, 95(1), 34–41. 
Added by: Admin (06 Jan 2014 18:22:39 UTC)
Resource type: Journal Article
BibTeX citation key: Blackwell2013
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Categories: General
Keywords: Chrysemys picta, Emydidae, Habitat - habitat, Kinosternidae, Nordamerika - North America, Parasiten - parasites, Schildkröten - turtles + tortoises, Sternotherus odoratus, Trachemys scripta
Creators: Blackwell, Letcher, Powell
Collection: Phytologia
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Abstract     
This paper reports the identity of a parasite (belonging to the Oomycota—and more broadly, the Straminipila), found in cladophoraceous algae (Basicladia) growing in tufts or more extensive coverings on the external surface of the carapace of freshwater turtles collected in Alabama and Mississippi. Whereas this Oomycete might have been placed in genus Lagenidium (historically a large group of plant and animal parasites), investigation by various workers has shown Lagenidium to be nomenclaturally (and systematically) questionable—its identity interwoven with a related (and also problematic) genus Myzocytium. We do not attempt to resolve the nomenclatural origins of Lagenidium and Myzocytium, but rather, after discussion of taxonomic problems, focus on placement of this Oomycete within current segregate genera (of Lagenidium)—established by Dick (1997, 2001), partly in response to taxonomic confusion. The best candidate for assignment of this Oomycete is Dick’s genus Syzygangia. Since there is also some question about the particular species of the algal host (genus Basicladia), occurring on turtles we examined, the specific identity of the alga is given consideration herein as well. Turtle-inhabiting species of Basicladia in the United States occur mainly east of the Rocky Mountains—B. crassa is a northern species, and B. chelonum is more wide-spread (cf. Hoffmann and Tilden, 1930; Smith, 1950; Prescott, 1962). These species are distinguished by dimensions of vegetative cells—larger in B. crassa. Both were reported mainly on snapping turtles (genus Chelydra), cf. Prescott (1962) and Graham et al. (2009), but other turtle hosts were noted (Hoffmann and Tilden, 1930). Anderson and Sinclair (1966) studied Basicladia crassa collected from “western painted turtle,” “Chrysemys picta bellii,” in Illinois. Basicladia has been examined infrequently in the southeastern US; B. chelonum was reported in North Carolina (Whitford and Schumacher, 1969) “on several species of turtles, especially the common mud turtle” (identities now difficult to determine). In our study—central Alabama, western Mississippi—the alga was found on turtles identified, respectively, as “stink-pots” (Sternotherus odoratus) and “red-eared slider” (Trachemys scripta elegans). It is not surprising to find Basicladia on these turtles, given habits of shallow submersion. Neill and Allen (1954) noted that a number of kinds of turtles (including Sternotherus odoratus, and Macrochelys temmincki, the alligator snapping turtle) may be “epizoized” by algae, presumably Basicladia, in Florida. The closest fit for the Basicladia we found (similar in Alabama and Mississippi) is B. chelonum. But, cell-widths of our specimens (distal filaments)—typically in the 30 to 60μm range—overlap measurements for B. chelonum and B. crassa (Hoffmann and Tilden, 1930). Also, pre-zoosporogenesis germination papillae (Figs. 7-8) are more prominent than illustrated for either species. Thus, the alga (as well as the Oomycete) here considered could bear future scrutiny.
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