Claws may be the most common biological attachment devices in animals but relatively few studies have examined the ecological and evolutionary significance of their morphology. We performed the first geometric morphometric investigation of arthropod claws ever using 15 intertidal oribatid mite species from two different families living in three different habitat types to determine if claw shape is correlated with ecology. Our results show that species living on rocky shores show remarkably high and strongly curved claws while species from mangrove habitats show significantly lower and less curved claws. Euryoecious species being able to dwell in a wide range of habitats show an intermediate claw type. These results indicate a strong relationship between claw shape and microhabitat whereas the best predictors of microhabitat use seem to be claw height and curvature. Claw length varied to some degree between the species but without any noticeable ecological pattern. A comparison with terrestrial and freshwater aquatic oribatid mite species, on the other hand, confirms that their claws are only half as long as that of intertidal mites and it is suggested that tidal flooding and wave action strongly selects for long claws. The present results indicate that claw morphology may play an important role in niche separation and hence demonstrate the importance of ecomorphological studies, especially in the microarthropod group which occupies a vast array of microhabitats.

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