Early life development of winged mapleleaf mussels was the subject of a recent article published in the American Midland Naturalist. - Photo courtesy of the U.S. Geological Survey

The results of winged mapleleaf mussel early life history investigations conducted by Service investigators from the La Crosse Fishery Resources Office and colleagues from the U.S. Geological Survey were recently published as a journal article in the American Midland Naturalist (Volume 157, pp. 297-311). 

The article, entitled “Thermal criteria for early life stage development of the winged mapleleaf mussel”, presents detailed analyses of corresponding water temperature and mussel metamorphosis data collected over a period of three years.

At the outset, these studies were intended solely to identify suitable host fish species for a federal endangered mussel species.  However, due to a modification of the original study protocol, laboratory tests of channel catfish (a species that ultimately proved to be a suitable host) were conducted at three different temperature regimes rather than one. 

The introduction of a single variable (temperature) in this replicated series of tests later provided the opportunity to compare the time required for encysted mussel larvae to metamorphose into juveniles under different thermal regimes and to develop a quantitative model that describes this thermal-temporal relation. 

The model was then used to empirically estimate the species-specific low-temperature threshold for development of winged mapleleaf larvae into juveniles on channel catfish (9.26 C) and the cumulative temperature units of development required to achieve peak excystment of juveniles (395 C·d). 

Additional tests simulated the long-term (over-winter) development of larvae into juveniles in natural thermal regimes and consistently affirmed the validity of these estimates, as well as provided evidence for a thermal cue (17-20 C) that is needed to trigger peak excystment of juvenile winged mapleleaf. 

This new information is now being used to guide work to successfully propagate juvenile winged mapleleaf for restoration efforts in the St. Croix National Scenic Riverway.

Journal publication of these peer-reviewed findings ensures widespread distribution of unique knowledge that can be used as a framework to determine thermal criteria for early life development of other mussel species and improve juvenile mussel production in propagation programs designed to help recover imperiled species. 

This article will soon be available to view at the Region 3 Fisheries Internet web site (http://www.fws.gov/midwest/Fisheries/pubpolicy.html).