ON THE SPECIFICITY AND RELATED PROPERTIES OF THE CRUSTACEAN CHROMATOPHOROTROPIC HORMONE

¹ From the Marine Biological Laboratory, Woods Hole, Massachusetts

1. A method for determining within an hour the relative activity of eye-stalk extracts of Uca pugilator has been described.

2. The amount of hormone present in one eye-stalk of Uca (5.0 grams) was calculated to be 0.2. The minimal amount of hormone detected by the method described was calculated to be 0.000016 , which represents a minimal unit of eye-stalk activity.

3. Distilled water is effective in expanding melanophores when injected into blinded specimens. The effect seems to be related to osmotic changes induced in the animal. Excepting the effect of distilled and tap water, the response of blinded animals to the eye-stalk hormone seems to be quite specific. Sixteen different drugs were ineffective in causing melanophore expansion.

4. Blinded animals immersed in distilled water become and remain dark for a week, after which they become refractory. However, they have not lost the ability to respond to injections of either eye-stalk hormone or distilled water.

5. Extracts of several organs other than the eye-stalk were found to be inactive on blinded specimens, even when 100 times more concentrated than a minimal unit of eye-stalk extract. Extracts of entire bodies, 2,000 times more concentrated than a minimal unit, were active.

6. Isolated leg melanophores respond slowly and irregularly to various ions. Na, K, Ca, Li chlorides all induce melanophore contraction. Na and K do not produce opposed responses in isolated leg melanophores as they do in isolated scale melanophores.

7. The relative solubility of the eye-stalk hormone in various organic solvents was determined. The hormone is inactivated by alkali, but the activity cannot be regenerated by treatment with acid.

8. Animals blinded for 2 weeks or more remain continuously pale, with the exception of 2-4 per cent of the specimens, which show slight periodic changes in coloration.

9. The diurnal rhythm of Uca is affected by constant light, and black background, both of which delay the appearance of the nocturnal hue on the legs.