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Biol Bull 108: 160-174. (April 1955)
© 1955 Marine Biological Laboratory
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THE DEMONSTRATION OF TWO CHROMATOPHOROTROPICALLY ACTIVE SUBSTANCES IN THE LAND ISOPOD, TRACHELIPUS RATHKEI

M. A. McWHINNIE 1 and H. M. SWEENEY 1

1 Department of Biological Sciences, Dc Paul University, Chicago 14, Illinois

1. The terrestrial isopod Trachelipus rathkei was found capable of exhibiting weak physiological color changes in response to changes in background. Under the stimulus of diffuse light, animals maintained upon a light background became lighter than animals maintained in the dark. Under the stimulus of more intense light, the animals darkened even upon a light background.

2. Structures showing a marked resemblance to the sinus glands of decapods are located at the distal end of each optic tract and agree in position with the sinus glands of other isopods.

3. Extracts of the sinus glands of Trachelipus induce a strong dispersion of the red pigment of Cambarus.

4. Extracts of the optic tracts or cerebral ganglia induced a weak dispersion of the red pigment of Cambarus, while extracts of the connectives or any segment of the thoracic cord induced a strong concentration of the same pigment.

5. A comparison of the influence of change in concentration upon the effectiveness of the two chromatophorotropins indicates that above a minimal concentration, the rate of response is only slightly increased, whereas the magnitude of response remains unaltered. Below this level, both the rate and magnitude of response decline with decreasing concentrations.

6. An antagonistic action was found to exist between the two chromatophorotropins such that high concentrations of either factor prevented the more dilute factor from exerting its influence. When very dilute extracts known to contain small quantities of both factors were assayed, both responses were elicited, such that the chromatophores assumed a condition of intermediate dispersion.

7. The response of Trachelipus to injected extracts proved inconclusive. The initiated responses suggest that the reactions of the pigmentary system of Trachelipus to injected extracts are opposite to those of Cambarus.






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