WILLIAMS, K.L.; Texas A&M University: Color complexity in the dactyls of the blue crab, Callinectes sapidus: a new method to evaluate biologically significant characteristics.

Many species use color during courtship displays, with the more colorful individuals often selected as potential mates. Studies of mate choice have typically viewed multi-colored attributes as a single homogenous color, whereas they may instead be combinations of several similar, but distinct colors. Specific colors within the attribute may thus have greater biological significance. Digital imaging techniques were used to examine and quantify a pattern of coloration in the female blue crab (Callinectes sapidus), which possess a prominent red stripe along the edge of the upper dactyl. Morphometric measurements were made using digital images of the carapace and chelae of crabs collected along the Gulf of Mexico coast in Galveston, Texas. A regression analysis found a significant relationship between the area of dactyl coloration and body size. Color complexity was then examined on digital images of the chelae using Adobe Photoshop and Image J. Specific wavelengths were selected and their presence within the attribute quantified and evaluated. The complexity of this attribute and its relationship to the crab�s spectral sensitivity is discussed.