Early Life History of the Sheepnose (Plethobasus Cyphyus) (Mollusca: Bivalvia: Unionoida)
JOURNAL OF NATURAL HISTORY, 2016 VOL. 50, NOS. 9–10, 523–542 http://dx.doi.org/10.1080/00222933.2015.1083059 Early life history of the sheepnose (Plethobasus cyphyus) (Mollusca: Bivalvia: Unionoida) Mark C. Hovea,b, Bernard E. Sietmanc, Matthew S. Bergd, Erika C. Frosta, Kiru Wolfa, Tony R. Bradye, Sarah L. Boyerb and Daniel J. Hornbachb aDepartment of Fisheries, Wildlife and Conservation Biology, University of Minnesota (UMN), Saint Paul, MN, USA; bBiology Department, Macalester College, Saint Paul, MN, USA; cDivision of Ecological and Water Resources, Minnesota Department of Natural Resources (MN DNR), Saint Paul, MN, USA; dBiology Department, Grantsburg High School, Grantsburg, WI, USA; eNatchitoches National Fish Hatchery, U.S. Fish and Wildlife Service, Natchitoches, LA, USA ABSTRACT ARTICLE HISTORY Managing a rare species can be improved with knowledge of Received 2 March 2015 its natural history. The sheepnose (Plethobasus cyphyus)isa Accepted 11 August 2015 freshwater mussel recently listed by the US as federally endan- Online 29 September 2015 gered. We used standard methods to study P. cyphyus brood- KEYWORDS ing behaviour, host fishes in the laboratory and under natural Unionoida; brooding conditions, and glochidial morphology. We monitored a popu- behaviour; glochidia; hosts; lation of P. cyphyus in the Chippewa River, WI during spring morphology and summer 2007–2009 and 2011 and found brooding animals between mid-May and early August. Gravid individuals ranged between 5 and 27 yr (mean age ± 1 s.d. = 13 ± 4 yr). Plethobasus cyphyus brooded glochidia in outer gills, which varied in colour from red, orange, pink, cream, or white. We observed mature glochidia more commonly in individuals with cream or white gills and these glochidia were released in a clear, adhesive, mucus matrix.
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