KITTREDGE ET AL: CHEMICAL SIGNALS IN THE SEA 



The threshold for response by the snail, 

 Biicc'nium uudatiim is 0.2-0.4 X lO"-' M 

 (Mackie, 1970). and the structure of these 

 steroid glycosides has been determined (Turner 

 et al., 1971). 



A behavioral bioassay of one of the ortho- 

 quinones derived from L-DOPA, dopachrome, 

 utilizing the feeding response of the lined shore 

 crab PachygmpsHS crassipes indicated that this 

 quinone might also be a "cryptic odor." Electro- 

 physiological studies, however, demonstrated 

 that these results were misleading. Utilizing a 

 preparation of the dactyl chemoreceptors of 

 the spiny lobster Pa)udinis interruptus, we 

 detected chemoreceptors for this quinone that 

 were about a hundred times as sensitive as the 

 general amino acid receptors in this prepara- 

 tion (Figure 2). While we have not explored the 



range of specificity of these receptors, the 

 results suggest that these crustaceans, the 

 natural prey of the octopus, have evolved a 

 mechanism for detecting the presence of the 

 predator. Our results with the bioassay likely 

 reflect a priority of responses to the two chem- 

 ical stimuli (Kittredge, Takahashi, and Lindsey, 

 unpublished data). 



PHEROMONES 



Unicellular chemical communication, 

 analogous to Haldane's primordial protistan 

 communication, is evident in the conjugation 

 of ciliates. The microconjugant of a peritrichous 

 ciliate, which is free swimming, can identify the 

 macroconjugant, which is sessile, by chemicals 

 released by the latter. Although evidence for 



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Figure 2. — Electrophysiological recordings from the dactyl chemoreceptors of a spiny lobster, Panulims interruptus. (1) 

 Seawater blank, (2) IQ-'i M dopachrome in seawater, (3) Persisting spikes in dopachrome receptors (continuation of 2), (4) 

 10-3 M taurine in seawater, (5) 10"3 M taurine after dopachrome and a seawater wash. 



