PHYSIOLOGICAL OBSERVATIONS UPON A LARVAL EUSTRONGYLIDES. IV. INFLUENCE OF TEMPERATURE, pH AND INORGANIC IONS UPON THE OXYGEN CONSUMPTION

¹ Department of Biology, The Catholic University of America, Washington, D. C.

1. The temperature range tolerated by a larval Eustrongylides is great. The worms were not harmed by temperatures between 5° C. and 45° C., but 48° C. proved to be injurious.

2. The oxygen consumption was studied in this temperature range. Its increase with rising temperature could be expressed by two lines only, if the Q₁₀ was calculated or if Arrhenius' formula was used. A fairly good fit to a single line resulted however if Blehrádek's formula was applied.

3. The oxygen consumption remained practically unchanged in the pH range 3.4 to 8.3, but it was increased in the pH ranges 1.1 to 2 and 9 to 10.7. It is possible that the increase in the extreme acid range is of biological significance, while that in the extreme alkaline range is probably only a reaction to unfavorable environmental conditions.

4. The oxygen consumption was studied in a series of isotonic solutions of various inorganic substances. Of all the solutions tested, only NaNO₂ and to a lesser degree KCl were definitely toxic. The oxygen consumption was stimulated by various ions according to the following series:

Cations: Na = or slightly < Mg < Ca = NH₄ < K

Anions: Cl = or slightly < SO₄ < NO₂ = NO₃ < PO₄.