DIURNAL MIGRATION OF PLANKTON 



27 



PHOTOTAXIS 



KINESIS 



Vf:-*t 



NAUPLIUS ETE 



/lOLET RECEPTOR 



:mperature ^^ 



RESSURE 



■^ 



ORIENT 



ATION VIGOR 



SIGN6- 



^>^ red: - 



REDOX 



<''?-;• 



v.. 



^<^> 



'< ^ 





CHANGES OF TEMP. 



& PRESSURE: DOTH 

 EYES MUST BE STIM 



COMPOUND EYE 



BLUE 

 RECEPTOR 



YELLOW 

 RECEPTOR 



ANTENNAL 



GRAVITY 

 RECEPTORS 



Fig. 3. Behavior patterns mediated by the naupHus eye, the compound eye, and 

 the antennal gravitational receptors. Arrows indicate relationships. Signs on the 

 arrows refer to the positive and negative taxes. Words on arrows indicate intensity 

 of stimulus. Broken lines show relationships present in the Cladocera, absent in 

 Eubranchipus. 



backed up by an opaque curtain. Gravity receptors appear to be localized 

 in the swimming antennae of Daphnia magna and monitor this force only 

 when the animal is not swimming. (Grosser, Baylor, and Smith, 1954). 

 Rose (1925) has obtained results with pH and temperature similar to ours. 



The Nauplius Eye and Vertical Migration 



The nauplius eye of adult Crustacea is smaller and of less importance 

 as a taxononiic character than the compound eye. Thus, its functional sig- 

 nificance has been somewhat neglected. Unpublished data of Lockhead 

 (personal communication) indicate that it has photosensitivity in the fairy 

 shrimp. It was completely unanticipated that the nauplius eye of daphnids 

 would be concerned with responses to pH, pressure, temperature, and 

 redox potentials as well as being sensitive to ultraviolet and x-rays. 



