J. Moll. Stud. (2001), 67, 407-416
© The Malacological Society of London
2001
SEASONAL METABOLISM AND BIOCHEMICAL COMPOSITION OF TWO UNIONID MUSSELS, ACTINONAIAS LIGAMENTINA AND AMBLEMA PLICATA
Department of Biology, Macalester College, 1600 Grand Ave., St. Paul, MN 55105 USA.; 1 Correspondence to: Shirley M. Baker, Department of Fisheries and Aquatic Sciences, University of Florida, 7922 NW 71st, St Gainesville, FL 32653. Phone: (352) 392-9617 x264; FAX: 352-846-1088
e-mail: smbaker{at}mail.ifas.ufl.edu
We examined the seasonal patterns of physiology and biochemical composition in two unionid bivalves, Actinonaias ligamentina (subfamily Lampsilinae) and Amblema plicata (subfamily Ambleminae). We found that (i) A. ligamentina and A. plicata displayed different seasonal changes in physiology and biochemical composition, (ii) larval brooding affected the physiology but not the biochemical composition of A. ligamentina, and (iii) A. plicata had a greater carbohydrate content and condition index than A. ligamentina. A. ligamentina and A. plicata had different patterns of ammonia excretion rate, O:N ratio, and clearance rate, while patterns of oxygen uptake rate were similar between the two species. Overall, weight specific metabolic rates were higher in A. ligamentina than in A. plicata. Both species had low protein and high carbohydrate content in early summer. Brooding specimens of A. ligamentina had lower oxygen uptake and ammonia excretion rates and higher O:N ratios than non-brooding specimens. Differences in condition and carbohydrate content between the two species could explain some of the species-specific mortalities observed since the introduction of zebra mussels.
(Received 6 April 1998; accepted 8 March 2001)