Meeting Abstract
Fish scales are morphologically diverse, both among species, within species, and on an individual. Scales are often categorized into three main types: cycloid scales have smooth edges; spinoid scales have spines protruding from the body of the scale; ctenoid scales have interdigitating spines protruding from the edge of the scale. For this study, we used 3D visualization techniques to investigate the scale morphology of the Bluegill sunfish (Lepomis macrochirus) over different parts of the body. Micro CT scanning was used to visualize individual scales taken from different parts of the bluegill. Also, a new technique called Gelsight was used to rapidly measure the 3D surface structure of scale patches from different parts of the fish. We used these data to compare scales on different parts of the fish, using simple morphological measurements and surface metrology metrics to amass a set of variables. We found that bluegill scales do change across the body – scales are cycloid on the opercle, ctenoid on the body and tail, and the proportion of ctenii coverage increases ventrally on the fish. Scales on the opercle and below the start of the dorsal fin were also shorter in height and length and less thick than scales elsewhere on the body. Surface roughness does not appear to change over the body of the fish, although scales at the start of the caudal peduncle have higher skew than other scales, indicating they have a surface that contains more peaks than valleys. Scale shape also changes, with scales near the base of the tail having a more elongated shape. This study illustrates how fish scale structure can vary over the body, and demonstrates how Gelsight can be used to image fish surface structures in 3D.
