Morphological Development and Differentiation of Little and Winter Skate

Little and winter skate are sister species with largely overlapping geographic distributions.  Both are important components of northeast Atlantic coastal marine communities. Their juveniles are visually indistinguishable up to a total length of roughly 30 cm, however above this they diverge substantially with respect to body size and morphology. Previous studies on the two species have described specific morphological characters at one life stage or another. However none have focused on their morphological development, comparing the timing and nature of key ontogenetic events that result in species with much different adult forms. We collected little and winter skate, ranging from juvenile to adults stages and imaged their endoskeletons in order to compare overall differences in structural form. Juveniles were cleared and stained with alcian blue dye while sub-adults and adults were radiographed. Morphological variables were then determined using geometric morphometrics. We used principle components analysis (PCA) and multivariate analysis of variance (MANOVA) in order to describe and statistically differentiate morphologies among species and life stages. Overall, the unique developmental trajectories of each species describe their occupation of morphospace and may begin to yield clues about functional and ecological consequences of their morphological evolution.