Robert Van Hoff

Publication Date


Advisor(s) - Committee Chair

Rudolph Prins, E.O. Beal, Larry Gleason

Degree Program

Department of Biology

Degree Type

Master of Science


Immature Orconectes immunis were obtained from Michigan in August, 1973, and July 1974 to determine the effects of photoperiod and temperature on the molt cycle of the crayfish and to test the effects of preconditioning on this species at a cold (7C) temperature from 45 to 90 days. Two sets of 3 experiments were conducted, each involving photoperiod, temperature and preconditioning. The first experiment of each set was initiated within a day after bringing the animals from the field, the subsequent two experiments of each set being initiated at 45-day intervals thereafter.

There were significant responses to photoperiod among the experimental animals; however, these positive responses were from large animals (17 mm+). Small animals (less than 17 mm) did not respond to photoperiod.

Combined experimental analyses indicated a highly significant (.01) positive linear relationship between temperature and molt frequency and photoperiod and molt frequency.

Larger animals (19.0-24.9 mm CT) exhibited a more definite photoperiod response than smaller animals (13.4-18.9 mm CT).

At 14 C 64.9%, at 18 C 45.8% and at 22 C 17.4% of the animals formed gastroliths but did not molt.

Data relating to feeding, effects of temperature on molting and gastrolith formation suggest that either premolt was prolonged or that molting was inhibited by cold temperature.


Biology | Life Sciences

Included in

Biology Commons