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Maria Kim: Master's Degree: Graduated June 2012


Photo: S.G.Dunbar


Sexual Dimorphism and Behavioral Responses to Conspecific
Chemical Cues in Pagurus samuelis

Click here to open her Thesis (pdf)




Maria worked on chemical communication in the hermit crab Pagurus samuelis for her MS degree.

She predicted that males and females would respond differently to cue waters created from their own sex. Females were exposed to female cue treatment odors and males were exposed to male cue treatment odors. She recorded hermit crabs exposed to cue treatment waters and analyzed four behaviors: withdrawn, head-extended, walking, and meral spread. Females were more likely than males to remain withdrawn in their shells when in non-agonistic cue treatment waters. Males were more likely than females to display meral spread when sensing conspecific cues.

During the study Maria also measured morphological differences between males and females and found there to be significant differences in the relation of carapace length and cheliped length between males and females.She found that males had significantly larger chelipeds in relation to carapace length than females (see Figure 1 below).

Regression Graph

Maria also found subtle differences betweem males and females in their responses to same- sex agonistic cue water. Females tended to remain more withdrawn in female agonistic water than males in male agonistic water. Both sexes tended to increase the time spent walking when compared to non-agonistic cue water. This may suggest that when hermit crabs sense agonistic interactions in other individuals around them they may exhibit flight responses, although females may remain withdrawn in the shell if there is only a single conspecific present.

For more details and an entire description of these studies, see the link for the full thesis above.