STUDIES IN THE PIGMENTARY SYSTEM OF CRUSTACEA. IV. THE UNITARY VERSUS THE MULTIPLE HORMONE HYPOTHESIS OF CONTROL

¹ From the Marine Biological Laboratory of the United Kingdom, Plymouth, England, the Stazione Zoologica, Naples, Italy, and the Biological Laboratories, Harvard University, Cambridge, Mass.

1. Experiments were performed to determine whether one or more than one hormone is involved in the control of the crustacean pigmentary system.

2. Transfusions of blood from black- and from white-adapted individuals into white-adapted Crangon result in the darkening of an equally low percentage of the test animals. Injection of rostral region extract produced darkening in slightly over 50 per cent of the injected animals.

3. Superficial cautery of the rostral region has no permanent effect on color mutability. Deep cautery in 69 animals resulted in 9 individuals which became permanently pale. In each of these 9 Crangon, however, swimming and equilibratory movements were abnormal. It is suggested that the deep cautery injured the supraesophageal ganglion, resulting in interference with the regulation of Hanström's sinus gland.

4. The validity of the unitary hormone hypothesis was subjected to a biological test by a study of the retinal and integumentary pigments in Hippolyte which has been reported to undergo a diurnal rhythm in the activity of the integumentary effectors.

5. No evidence of persistent activity could be found in the retinal pigments of H. varians; the eyes of H. pleuracantha showed a persistent cyclic rhythm of the distal retinal pigment, but this was not in the phase expected in H. varians.

6. Further study showed that the reported periodicity of color change in H. varians was due to a direct effect of darkness on the body chromatophores.

7. The threshold limits of the retinal and integumentary pigment cells to eye-stalk hormones were determined in Leander adspersus. The lower threshold limit for the distal retinal pigment was found to be equivalent to 0.016 mg. (wet weight) of eye-stalk; that for the integumentary pigment was 0.0008 mg. These values do not support the unitary hormone hypothesis which requires that the minimal threshold for the retinal pigments be lower than that for the body chromatophores.

8. The responses of the distal retinal pigment to various concentrations of stalk extract are plotted in curves which show a direct relation between the response and the injected dosage.