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Biol Bull 137: 79-94. (August 1969)
© 1969 Marine Biological Laboratory
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THE INFLUENCE OF LIGHT ON ASEXUAL REPRODUCTION IN GREEN AND APOSYMBIOTIC HYDRA

LEONARD G. EPP 1 and CHARLES F. LYTLE 1

1 Department of Biology, Pennsylvania State University, University Park, Pennsylvania 16802

1. Experiments were conducted with three strains of green and aposymbiotic hydra to study the effects of light on asexual reproduction. Animals used were the Kenilworth Green and Kenilworth Albino (aposymbiotic) strains of Chlorohydra hadleyi and the Burnett Green strain of Chlorohydra viridissima.

2. Budding of both the Kenilworth Green hydra and the Kenilworth Albino hydra was significantly greater in constant light and with 12 hours light/12 hours darkness than under constant darkness, indicating that some factor other than the green algae promotes budding of albino hydra in lighted cultures.

3. Budding was less in Burnett Green hydra in constant light and 12 hours light/12 hours darkness than under continuous darkness.

4. Budding increased with increasing photoperiods in the Kenilworth Albino hydra but decreased with increasing photoperiods in the Burnett Green hydra.

5. No difference was observed in the budding of Kenilworth Green and Albino hydra at 250 and 3200 foot candles, but budding was greatly reduced in Burnett Green hydra at 3200 foot candles.

6. Kenilworth Green hydra produced more buds during starvation when exposed to constant darkness, 12 hours light/12 hours darkness, and constant light than Kenilworth Albino hydra.

7. Prior exposure to crowding conditions resulted in decreased budding in starved Kenilworth Green and Albino hydra grown in constant darkness, 12 hours light/12 hours darkness, and constant light. Similarly treated Burnett Green hydra, however, showed increased budding under all three light regimes.

8. The results suggest that budding in green and albino hydra is regulated by levels of some undefined critical metabolite which can be derived both from food and symbiotic algae. Burnett Green hydra appear to maintain smaller metabolic pools of this substance than Kenilworth Green and Albino hydra, and excessive levels of this metabolite tend to inhibit budding in this strain.






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Copyright © 1969 by the Marine Biological Laboratory.