In North America, sheepshead minnow, Cyprinodon variegates, dominate some of the harshest aquatic habitats known. This small cyprinodontid is common to shallow saltwater swamps, sloughs, and tide pools from Cape Cod, south to the Yucatan Peninsula, Venezuela, and throughout the Gulf of Mexico. The species is well known for its ability to thrive in harsh abiotic environments that prove lethal to other fishes . Some Gulf of Mexico populations, for example, survive seasonal water temperature shifts of more than 36°C; diurnal fluctuations of up to 15°C; and rapid, unpredictable temperature drops of up to 5°C/h. Not surprisingly, sheepshead minnow display the widest range of temperature tolerance and the highest upper thermal limit known in fish, characteristics that no doubt contribute to their wide distribution range and successful occupation of harsh thermal habitats. Aquatic temperature fluctuations concomitantly bring along alteration in water oxygen tension, and potentially a flux in salinity concentration. Thus, the sheepshead minnow is an excellent study organism to demonstrate many of the physiological extremes that can be experienced by one species within a life –time, making it a great example for comparative environmental physiology laboratory experiments. In particular, we are interested in gauging the sheepshead minnow’s various physiological tolerances as a means of assessing the species’ adaptive capacities in the face of widespread ecological climate change. Additionally, we posit that our data may help to define an ‘upper limit’ in physiological adaptations for numerous other species – that is to say, that the adaptive plasticity demonstrated by sheepshead minnows under the following circumstances is unlikely to be matched or exceeded by many, if any other species assuming roughly the same ecological conditions and shifts.
For this project, five separate cohorts of 30 fish apiece will be acclimated to the following temperature regimes (one per cohort): 10°C, 15°C, 25°C, 30°C, 35°C. These animals will be used for CTmax and hypoxia trials.
The novelty of our study lies in applying well-known whole-organism methods to determine whether temperature acclimation has an effect on anoxia tolerance and comparing those whole-organismal measurements to cellular level parameters. The student involved in this project will be able to learn confocal microscopy and enzymatic techniques to determine muscle fiber size changes due to temperature acclimation.
Number of Student Researchers
Applications open on 01/15/2017 and close on 02/07/2017