CHROMATOSOME-DISPERSING HORMONE 



is more easily demonstrated in certain amphibia than in 

 animals of other classes.' 



The importayice of the pituitary body in regulating chromato- 

 some dispersion in fishes. — In fishes hypophysectomy often 

 is followed by a marked concentration of the melanosomes 

 (the "melanophore contraction" of some authors). However, 

 the change appears more sluggishly than in amphibia. Most 

 of the successful experiments have been performed in various 

 elasmobranchs. Lundstrom and Bard had shown that the 

 removal of the neuro-intermediate lobe from the dogfish, 

 Mustelis canis^ is followed by a marked pallor of the skin 

 due to the concentration of the melanosomes in the central 

 part of the melanophores. As a phase of his investigation of 

 the physiology of the chromatophores of various animals, 

 Hogben (1936) studied the effects of hypophysectomy in 

 several elasmobranchs. Figure 26 is reproduced from Hog- 

 ben's article and illustrates the cutaneous pallor of Rhina 

 squatina following hypophysectomy. The adaptation of 

 fishes such as dogfishes {Scy Ilium catulus^ S. canicula)^ the 

 angel shark {Rhina squatina), and rays {Raia maculata, R. 

 brachiura) to a black background is abolished by hypophy- 

 sectomy. However, in some species the operation may not 

 be followed by as striking a macroscopic effect as is illus- 



■ Abramovitz (1936-37) has published several reports extending the observa- 

 tions of Megasur and of Carlson on the hormone in the eye-stalks of Crustacea. This 

 hormone appears to be responsible for melanosome dispersion in Crustacea such as 

 Callinectes, Libinia, Palaemoyietes, and Uca. Extirpation of the eye-stalks of the 

 crab, Uca, is followed by paleness of the integument (Megasur); if an extract of 

 eye-stalks be injected into such pale crabs, dispersion of the melanosomes occurs 

 and the animal becomes dark (Carlson). Abramovitz found that an extract of the 

 eye-stalks of Palaemonetes vulgaris produces effects similar to those of the chromato- 

 some-dispersing hormone of the pituitary. This was shown by the dispersion of 

 the pigment in the melanophores following injection of the extract into Hght-adapt- 

 ed or hypophysectomized fishes {Anieiurus nebulosus, Mustelis), frogs [Rana 

 pipiens), or reptiles {Anolis carolinensis). The erythrophores and melanophores of 

 the dace (Chrosomus erythrogaster) were similarly affected. 



The substance responsible for these effects was found to be remarkably stable. 

 It could survive boiling in water or in aqueous solutions of i per cent HCl or KOH. 

 It appeared to be soluble in water and in methanol or ethanol — although the extent 

 to which this is true was not accurately described. 



[245] 



