INVESTIGATION ON THE ECOLOGY AND RESPIRATORY RESPONSES OF THE HEMICHORDATE PTYCHODERA FLAVA TO TIDAL CYCLES AND SALINITY CHANGES

¹ Department of Zoology, University of Madras, Madras-600005, India

1. Some aspects of the ecology and respiratory physiology of Ptychodera flava have been studied.

2. Increase in body weight involves a decrease in the rate of oxygen consumption. At high tides, the rates of oxygen uptake of nonbreeding P. flava are 0.7629 (smallest) and 0.3363 (largest) in ml/g/hr. At high tides, mature and spawning female rates are 6.732 (smallest) and 0.8877 (largest) ml/g/hr. Rate of oxygen uptake is a function both of body size and of maturity stage in P. flava.

3. Respiratory responses of 15 specimens of P. flava fell into three classes: 1, showing a rhythm synchronized with tidal phases; 2, showing a tidal rhythm with additional peaks during low tides; or 3, with no detectable rhythm.

4. P. flava reacts to lowered salinity by showing a sudden rise in respiration. The sustained level of respiration is subsequently a little higher than in normal sea water.

5. The deep-seated tidal rhythm shows variations, and it is suggested that locomotor activity, spawning, temperature, and salinity may all be factors involved.