A study of the oxygen consumption of the five species of leech

A correlation between the oxygen consumption of aquatic animals and their ecology has been demonstrated on many occasions (see Prosser, 1950, table 42; Whit-ney, 1942; Walshe, 1948; and Berg, 1952). Regarding fresh-water forms, two main conclusions emerge: (1) that many inhabitants of rapid streams have a higher rate of oxygen consumption than similar and closely related forms from slow streams or standing water; and (2) that inhabitants of oxygen-deficient water are often able to maintain a steady rate of oxygen consumption in the face of falling oxygen tension in the medium, until a critical level of oxygen tension is reached, below which the oxygen consumption falls rapidly. This paper records a preliminary investigation into the oxygen consumption of five species of leech, Glossiphonia complanata (L.), Helobdella stagnalis (L.), Erpo-bdella octoculata (L.), E. testacea (Sav.) and Piscicola geometra (L.). An earlier study of the ecology of leeches (Mann, 1955) had shown that, while several of these species are widely distributed in various types of fresh-water habitat, each has a distinct habitat optimum, where it is the most abundant leech species and can be found i