Environmental Factors Affecting the Acclimatory Responses of Ectotherms

Abstract

Patterns of Acclimatory Responses in Ectotherms Most studies on thermal acclimation of whole organisms have involved direct or indirect measurements of the effects of short-term experimental temperature change on easily measurable phenomena such as growth rates (Dehnel, 1955), heart rates (Segal, Rao and James, 1953; Pickens, 1965; Ahsanullah and Newell, 1971), cirral activity in barnacles (Crisp and Ritz, 1967 a, b; Ritz and Foster, 1968), feeding rates (Rao, 1953 a, b), radular activity (Newell, Pye and Ahsanullah, 1971a) or temperature tolerance (Fry, 1957; Vernberg, Schlieper and Schneider, 1963; Newell, Pye and Ahsanullah, 1971b). As is well-known, the rates of activity commonly vary directly with experimental temperature with aQ 10 of approximately 2.0 over the normal environmental temperature range of the organism. Higher values than 2.0 for the Q 10 are obtained at low experimental temperatures and lower values than this at high experimental temperatures. Compensation for long-term changes in temperature has been discussed in detail by Bullock (1955), Precht, Christophersen and Hensel (1955), Prosser (1955, 1958), Precht (1958) and Prosser and Brown (1961). Briefly, one may recognise (a) a relatively non-specific increase in enzyme concentration in response to cold acclimation, (b) translation or (c) rotation of the rate: temperature curve or a combination of these responses following thermal acclimation.