SEX PHEROMONE ACTIVITY OF THE MOLTING HORMONE, 

 CRUSTECDYSONE, ON MALE CRABS 



(Pachygrapsus crassipes. Cancer antennarius, AND C. anthonyi) 



James S. Kittredge,' Michelle Terry,' and Francis T. Takahashi' 



ABSTRACT 



The pheromone released by premolt female Pachygrapsus crassipes is a heat stable non-ionic polar lipid. 

 The coincidence of the release of the pheromone and the nubial molt suggested that the molting hormone, 

 crustecdysone, may also function as a sex pheromone. Adult male crabs were observed to display 

 typical precopulatory behavior when exposed to dilute solutions of crustecdysone. The threshold con- 

 centration for behavioral response was found to be 10~i3 m fgj. p crassipes, 10^ i" M for Cancer 

 antetmariiis and 10-8 m for C. anthovyi. These findings provide the basis for a theory of the evolu- 

 tion of pheromone communication in the Arthropoda. 



The dominant position of chemoreception in the 

 behavior of marine invertebrates and the impli- 

 cation of sex pheromones in the reproductive 

 activities of many species is supported by many 

 behavioral observations, but no pheromone has 

 yet been characterized from the marine environ- 

 ment. In many marine decapod Crustacea copu- 

 lation takes place immediately after the female 

 molts. The male of the species recognizes the 

 premolt condition of the female, is attracted to 

 her, and usually seizes and carries her until 

 she molts. This recognition at a distance has 

 been repoi-ted for many genera of Crustacea 

 (Hay, 1905 ; L. Agassiz in Verrill, 1908; Needier, 

 1931; Burkenroad, 1947; Williamson, 1953; 

 Hughes and Matthiessen, 1962; Knudsen, 1964; 

 Snow and Neilsen, 1966). Ryan (1966) de- 

 scribed the search and display behavior exhib- 

 ited by male Portunus anguinotentus when a 

 premolt female crab was placed in the holding 

 tank with them. Each male became active, 

 walked about on the tips of its dactyls, elevated 

 its body, and extended its chelae. When thus 

 stimulated they often attempted to pull any 



' Division of^eurosciences. City of Hope National 

 Medical Center, Duarte, Calif. 91010. 



' Zoology Department, Oregon State University, Cor- 

 vallis, Oreg. 97331. The data in this paper are taken 

 in part from a dissertation by F.T.T. to be submitted 

 to Oregon State University in partial fulfillment of the 

 requirements for the degree of Doctor of Philosophy. 



Manuscript received January 1971. 

 FISHERY BULLETIN; VOL. 69, NO. 



crab they met into a precopulatory carrying 

 position. Ryan demonstrated that this behavior 

 is released by a sex pheromone in the urine of 

 the premolt female crab. 



METHODS 



BIOASSAY 



Observation vessels for determining the re- 

 sponse of male Pachygrapsus crassipes to dilute 

 solutions of molting hormone were constructed 

 from 4-liter beakers. With a glass blowing 

 torch and the edge of a carbon flat we formed 

 an indent in the side of each beaker approxi- 

 mately 4 cm deep, parallel to and 3 cm above 

 the bottom of the beaker. The outside of the 

 beakers was masked with black paint with the 

 exception of an 8 cm window opposite the in- 

 dent. When a crab was placed in seawater in 

 the observation chamber, they always scurried 

 into the niche between the bottom of the beaker 

 and the indent. If the seawater contained molt- 

 ing hormone, the crabs were stimulated to come 

 out of the niche and assume a premating stance. 

 The time elapsing after adding a solution of 

 crustecdysone in seawater to an empty vessel 

 containing a male crab until the crab elevated 

 its cephalothorax in a typical stance was noted. 

 Six crabs were timed at each concentration of 



337 



