Center for Marine Biodiversity and Conservation

Brain organization in elasmobranchs has been shown to reflect habitat complexity and sensory demands across species, yet whether geography alone can drive similar patterns within a single species remains an open question. This study examined whether brain region proportions vary across the latitudinal range of the Atlantic Sharpnose Shark, Rhizoprionodon terraenovae, using a dataset of 47 specimens collected across six sites spanning the species' distribution, with populations compared between the Atlantic Ocean and the Gulf of Mexico. Three brain regions differed significantly between Atlantic and Gulf populations after controlling for body size. The olfactory bulb was proportionally greater in Atlantic sharks, consistent with the chemosensory demands of navigating low-visibility estuarine environments. The mesencephalon and cerebellum were proportionally greater in Gulf sharks, consistent with the visual and locomotor demands of clearer, more open coastal waters. These findings provide the first evidence of latitudinal variation in brain organization within R. terraenovae and suggest that regional environmental differences may influence sensory investment at the population level, contributing to a broader understanding of how environmental gradients may shape neurobiological traits within marine species.