The Relation of Oxygen Consumption to Substrate Particle Size in Two Burrowing Mayflies

Abstract

1. This study is concerned with the relation of oxygen consumption to substrate particle size in the morphologically similar burrowing mafies Ephemera simulansand Hexagenia limbata. 2. Nymphs, 16-24 mm. in length, were placed at 13.0°C. for 24 hr. before experimentation. Oxygen consumption experiments employed the standard ‘oxygen consumed in a closed bottle ’ technique and a modification. The standard technique was referred to as the ‘blank-bottle’ method, while the modification was called the ‘substrate-bottle’ method (washed substrate fractions were placed in the bottle). 3. The relationship between substrate particle size and oxygen consumption was indicated by a bimodal curve. The oxygen consumption fell, rose and fell once more as the particle size decreased from χ - 4 to χ + 5. 4. Substrate selection experiments with E. simulans nymphs revealed an inverse relationship between selection for particle size and oxygen consumption. 5. The burrowing front legs of the nymphs seem to be modified for a given substrate (coarse for E. simulans; fine for H. limbata) and, the less favourable the substrate, the more work that must be done to gain admittance or to burrow further. The particle size in which the nymphs showed the least oxygen consumption was considered to be an ‘optimal substrate’(χ- 1 for E. simulans and probably silt for H. limbata).