The common killifish, Fundulus heteroclitus, inhabits

• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Crawford; Griffith; Newfoundland
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.717.8608; http://www.biology.mcmaster.ca/fcl/scott/web/Articles%20etc/Scott-2004-JEB.pdf

brackish water estuaries and salt marshes along the eastern coast of North America. The species distribution is latitudinal, from Newfoundland to Florida, and thus spans a cline of environmental temperatures. Correspondingly, many previous studies have investigated thermal adaptations in populations across the range. Differences between populations include latitudinal differences in glycolytic enzyme expression and activity (Powers et al., 1986; Pierce and Crawford, 1996), endocrinology (DeKoning et al., 2004; Picard and Schulte, 2004), metabolism (Podrabsky et al., 2000), morphology and behaviour (Powers et al., 1993), and, as a result, these fish are sometimes divided into two subspecies, F.h. macrolepidotus (northern) and F.h. heteroclitus (southern). By contrast, few studies have assessed whether intraspecific physiological differences exist between populations of F. heteroclitus in response to other environmental factors (e.g. tidal cycle; DiMichele and Westerman, 1997). Species within the genus Fundulus are suggested to have arisen from brackish water ancestors, and there is substantial variation in both the salinity of their native habitats (ranging from freshwater to seawater) and their salinity tolerance (Griffith, 1974). Intraspecific differences in salinity tolerance and distribution also appear to exist within some Fundulus species. For example, northern populations of F. heteroclitus have higher fertilization success and larval survival in hyposmotic salinities than southern populations (Able and Palmer, 1988). Furthermore, the proportion of northern genotypes increases in freshwater habitats, even at latitudes and temperatures that are typical for the southern subspecies (Powers et al., 1993). It is therefore likely that molecular or physiological differences exist within F. heteroclitus that form the basis for variation in freshwater tolerance.