An investigation of the effects of temperature on the melanophores of some teleost fishes with special reference to chromatic nervous control in Phoxinus phoxinus (L.)

Abstract

The effects of locally applied high and low temperatures on the melanophores of Phoxinus phoxinus (L) are investigated. The results of v.Frisch (1911) on Phoxinus and of Smith (1928) on Fundulus are in general confirmed and several new features of the responses are described. The effects are found to occur in several species of teleost fishes but are absent in others of the 31 species which are newly investigated.Reflex mediation of the responses from sensory endings in the skin is rejected and a new theory is put forward to account for the phenomena observed. This requires no novel anatomical elements but demands double reciprocal nervous control of melanophore action.The question of double innervation is reinvestigated by means of selective electrical accommodation in a nerve-melanophore preparation. The experiments of v.Gelei (1942) involving the use of ergotamine as a selective blocking agent are confirmed but the arguments put forward by that author for the pathways of melanophore dispersing fibres are shown to be false. An alternative theory, consistent with the results of other authors, is proposed to explain these results. The possibility that ergotamine reverses the responses of melanophores to sympathomimetic agents is examined.The effects of certain other selective blocking and stimulating drugs on the responses of melanophores to background colour, extreme temperatures and electricalstimulation are examined.No conclusive solutions to the initial problems are reached but several new questions are raised and suggestions for further experimental work are put forward.