A comparative analysis of setae on the pereiopods of reproductive male and female Orconectes rusticus (Decapoda: Astacidae)

Abstract

The pereiopods (walking legs) of crustaceans have been shown to have both mechano- and chemosensory functions including: detecting various odors, mechanical stimuli, as well as being used for grooming of gills and brood care. Using scanning electron microscopy, we examined the pereiopods of reproductive male (form I) and reproductive female (glair) crayfish Orconectes rusticus Girard, 1852 and found that the distal portion (dorsal surface) of the propodus of pereiopods 2 through 5 contain smooth, plumose, serrate and cuspidate setae. Various studies have implicated both smooth and serrate setae as being important for grooming; therefore, we used scanning electron microscopy to examine and compare the distribution of smooth and serrate setae on the pereiopods of reproductive male and female crayfish in order to determine if there were differences between sexes. We found that there were no differences in the number of tufts (pockets) or number of smooth setae on the second and third pereiopods (chelipeds) between male and female crayfish. Further, the second and third pereiopods of both male and female crayfish had significantly more smooth setae than the fourth and fifth pereiopods. When the distribution of serrate setae was compared, we found that reproductive female crayfish possess significantly more serrate setae on their fifth pereiopods than their fourth pereiopods and both pereiopods 4 and 5 of form I male crayfish. Overall, increases in serrate setae on the fifth pereiopods of reproductive female crayfish are significant. We suggest that female crayfish may use serrate setae of the fifth pereiopods extensively for grooming eggs and brood care during reproduction.