Temperature and Food as Factors Influencing Oxygen Consumption of Intertidal Organisms, Particularly Limpets

Abstract

SYNOPSIS: In intertidal animals rates of oxygen consumption span an order of magnitude (even when standardised for body size and temperature). This may reflect different adaptations to this variable habitat. Temperatures range widely and potentially increase metabolic expenditure during the heat of the day, while periods of feeding may be restricted. The balance between intake and expenditure of energy may limit zonation, body size, and even mode of reproduction. One pattern is that species suffering shortage of food (“conservers”) have low rates of oxygen consumption while those with abundant food (“exploiters”) have high rates. Conservers appear to have several means of reducing metabolic costs, but exploiters maintain high (seemingly wasteful) rates of oxygen consumption. Oxygen consumption cannot, however, be considered separately, since it reflects turnover,including growth rate and reproductive output. There is also the question whether differences between species are genetically controlled, or simply phenotypic responses to food availability. Comparisons of populations with different amounts of food suggest that exploiters substantially reduce oxygen consumption when food is scarce, but conservers are relatively fixed in their pattern of slow growth and low reproductive output, even if food is experimentally increased. Growth and reproduction are positively correlated, at least within taxonomically related groups (as exemplified by patellacean limpets) but both are inversely related to longevity.Thus growth and reproduction are not necessarily “traded off,” but are both low in “conservers” and both high in “exploiters.”