Latitudinal Differentiation in Copepod Growth: An Adaptation to Temperature

Abstract

We demonstrate the presence of significant differentiation in development rate, adult body length, and stomatic growth rate in the estuarine harpacticoid copepod Scottolana canadensis (Willey) collected from a broad range of latitudes (27°—43° N) and reared in the laboratory for several generations under the same conditions (15 g salts per 1000 g seawater, and 15°, 20°, 25°, or 28°C). The changing pattern of differential growth with increased temperature suggests local adaptation to maximize scope for growth under prevailing temperatures conditions; northern—derived individuals grew faster at low but not at high temperatures.

Radiocaesium elimination in fish: variation among and within species

“…The metabolic rate of bream should be generally low, and much lower than the salmonids, consistent with its small gill area and performance at low oxygen concentrations (Hughes 1980(Hughes , 1984. Our observations are also consistent with the metabolic compensation hypothesis (Levinton 1983;Lonsdale & Levinton 1985), which states that ectothermal species from warm environments have lower metabolic rates than species from colder environments. Bream has the southern-most natural distribution of the examined species.…”

Latitudinal compensation in oyster ciliary activity

“…When Long Island Sound oyster populations were tested, some individuals produced water currents at temperatures as low as 2°C (Loosanoff 1958), and Galtsoff (1964) found ciliary beating as low as the freezing temperature of water which is -1 to -2°C, depending on the salinity of the water, in Long Island Sound oysters. However, all of this evidence could be based on physiological acclimatization to temperature differences with no long-term genetic changes in the local populations (Prosser 1973;Lonsdale & Levinton 1985;Present & Conover 1992).…”

“…The temperature compensation hypothesis predicts that individuals from colder temperature regimes have greater physiological activity at lower temperatures than individuals from warmer temperature regimes to compensate for the temperature-associated slowing of physiological functions (Lonsdale & Levinton 1985). The Long Island Sound origin oysters had significantly greater cilia activity at lower temperatures than the Delaware Bay origin oysters.…”

“…Variation in growth rates of local populations across latitudinal clines is common in many species (Dehnel 1955;Ament 1979;Lonsdale & Levinton 1985;Prosser 1986;Conover & Present 1990;Schultz, Reynolds & Conover 1996). One hypothesis suggested to account for these growth rate differences is latitudinal physiological compensation for local environmental differences associated with latitude (Levinton & Monahan 1983;Conover & Schultz 1995).…”

“…The first model proposes that organisms adapt to their local temperature regimes, maximizing their scope for growth at those local average temperatures (Levinton & Monahan 1983;Lonsdale & Levinton 1985). The second model concentrates on compensation for differences in seasonality (Conover & Present 1990).…”