328 



THE BIOLOGY OF MARINE ANIMALS 



Crustaceans are the only marine invertebrates in which colour vision 

 has been postulated. The evidence is derived from: decorating-responses of 

 spider crabs in coloured aquaria; selection of coloured shells by hermit 

 crabs; background responses of shrimps (Crangon); and optomotor res- 

 ponses of crabs and prawns to vertically oriented moving coloured 

 stripes. The latter can change colour with respect to yellow and red 

 environments independently of intensity (147, 165). 



There is a wealth of observations relating to colour vision in fishes. 

 Experimental techniques have involved the preference method (e.g. 



wo 



Larvae of 



Pa.la.emonetes 



vulgaris 



100 



450 500 550 600 650 450 500 550 500 550 600 



Wave- I ength (mfj) 



Fig. 8.17. Action Spectra of Various Animals, Determined 

 by Behaviour Studies 



(Sources: Cerianthus, from Moore (111); Palaemonetes, White (159); Mya, Hecht 

 (67); Myxine, Steven (136); Lepomis, Grundfest (58).) 



voluntary selection of one among several colours), learning and back- 

 ground responses. Minnows which have been taught to associate a given 

 colour with food subsequently distinguish blue and green from each other, 

 and from yellow and red. On different backgrounds, or in lights of differ- 

 ent colours, various teleosts show chromatic adjustments which depend 

 on environmental colour independently of intensity. The most convincing 

 proof of colour vision in fish has been secured by means of conditioned 

 reflexes. Blennies {Blennius pholis) were given a visual stimulus associated 

 with an electric shock. During the course of training the fish learnt to 

 discriminate grey from other colours whenever they were contrasted, but 



