FISHERY BLLLETIN: VOL, 69, NO. 2 



1970; Cherbas and Cherbas, 1970; Heinrich 

 and Hoffmeister, 1970). 



The isolation and analysis of the material 

 released into seawater by active female P. cras- 

 sipes, C. mac/ister, and C. i)roductus demon- 

 strated that a compound could be detected that 

 is eluted from two different columns in the same 

 position as crustecdysone and has a UV absorp- 

 tion spectra that is similar to that of crustec- 

 dysone. 



The semilogs plot of the response times for 

 male P. cmssiiies to varying concentrations of 

 crustecdysone is approximately ]3arabolic, and 

 the scatter of response times at each concen- 

 tration is remarkably narrow. This, the range 

 of response times, and the continued resjionse 

 of the male crabs after removal from the stim- 

 ulus, permit an interpretation of the chemore- 

 ception of pheromones from dilute solutions. 

 The observations suggest that the pheromone 

 has a high affinity for the receptor site resulting 

 in a long half life for the receptor-pheromone 

 complex. Indeed, one might have postulated that 

 even a polar steroid might be strongly bound to a 

 lipoid receiitor in an aqueous medium. It is aj)- 

 parent that the crabs are capable of summating 

 the chemical information for a considerable per- 

 iod of time before a threshold which releases re- 

 sponse liehavior is reached. Though summation 

 may take place at any level in the nervous sys- 

 tem, the simplest interpretation suggests that 

 this takes place at the receptors. This summa- 

 tion of "information quanta" can function either 

 in extremely dilute solutions or, in nature, it 

 would permit the accumulation of subthreshold 

 amounts presented in random turbulences of 

 the current from the source. 



This finding has significance in a consider- 

 ation of the evolution of pheromone communi- 

 cation. It has been suggested that chemical 

 signals between cells were evolved before the 

 evolution of the metazoans and that these sig- 

 nals were later internalized as hormones and 

 synaptic transmitters (Haldane, 195r); Wilson, 

 1968). In the present instance we have a re- 

 versal of this internalization. The Crustacea, 

 having evolved polar steroid hormones to reg- 

 ulate molting, on externalization of the receptor 



site onto chemoreceptor organs and on altera- 

 tion of the resorption process in the antennual 

 gland during the premolt stage of the females 

 were then capable of signaling the approach of 

 the nubial molt. This interpretation obviates 

 the concern over the improbability of the simul- 

 taneous de novo origin of both the genetic in- 

 formation directing the biosynthesis of the pher- 

 omone and that concerned with the architecture 

 of the i-eceptor site. We may assume that an 

 unmasking of that portion of the chromosome 

 that specifies the receptor site for the hormone 

 on the membranes of the target organs occurred 

 in the chemosensory neurons. A masking of the 

 active transport system for the hormone from 

 the fluid of the antennule gland of the female 

 is also assumed. These two innovations are 

 reasonably small evolutionary steps and con- 

 ceptually preferable to the two de nova origins 

 that must be assumed otherwise. This evolu- 

 tionary step, the pheromone function of a hor- 

 mone, may have been the origin of pheromone 

 communication in the Arthropoda, for once fixed 

 because of its reproductive value, it was then 

 susceptible to a gradual evolutionary drift to- 

 ward a variety of more specific pheromones. 



ACKNOWLEDGMENTS 



We thank the National Marine Fisheries Ser- 

 vice, Fishery-Oceanography Center, La Jolla, 

 Calif., for providing seawater facilities. This 

 research was supported by ONR Contract 

 N00014-70-C-0059 and NSF Institutional Sea 

 Grant GH-10 and was also made possible in 

 ]iart by an Irving Genett Research Fellowship 

 (J. S. Kittredge) and a California Biochemical 

 Foundation Summer Student Fellowship (M. 

 Terry). 



LITERATURE CITED 



BOVBJERG, R. V. 



19G0. Courtship behavior of the lined .shore crab, 

 Paclij/grapsus crassipes (Randall). Pac. Sci. 14: 

 421-422. 

 Bradlow, H. L. 



1968. Extraction of steroid conjugates with a 

 neutral re.sin. Steroids 11: 265-272. 



342 



