THE REPRODUCTIVE POTENTIAL OF A SINGLE CLONE OF PELMATOHYDRA OLIGACTIS

¹ Department of Biological Sciences, Northwestern University, Evanston, Illinois

1. A single Pelmatohydra oligactis, when maintained under favorable conditions of temperature and water and given maximal amounts of food, reproduces rapidly and continually. New buds are formed every five hours when reproduction is at its height and buds may be detached in 17 hours after their first appearance.

2. Periods of maximal reproduction alternate with periods of depression during which specimens become inactive and in many instances degenerate at the apical ends. Some specimens die during the periods of depression but most of them regenerate the lost parts and resume reproduction by budding.

3. The average daily rate of bud production in 184 specimens, including those which eventually died during depressions, was 1.14.

4. There is no general decline, during a 75 day period, in reproductive vigor and rate in single specimens or in succeeding generations. During the 75 day period 18 generations were produced.

5. The total potential production by a single animal for a 75 day period can be obtained by using the average total number of doubling (budding) for the period, 75 x 1.14, as an exponent of 2.

6. Sudden reductions in population may be directly caused in natural habitats by unfavorable environmental factors, but the physiological depressions which follow rapid reproduction contribute to the decline by rendering the animals inactive and unable to accommodate themselves to changing conditions.

7. The depressions which follow rapid reproduction are basic intrinsic physiological states which may be genuine states of senescence. They may be caused by exhaustion of some substance essential to normal metabolism or to the accumulation of some substance which interferes with metabolism. Specimens appear capable of repeating the cycles of reproduction and depression indefinitely under favorable circumstances.

This article has been cited by other articles:

				W. F. Loomis The Cultivation of Hydra Under Controlled Conditions Science, May 22, 1953; 117(3047): 565 - 566. [PDF]