Ecomorphological and Age-Related Adaptations in the Tongues of Phocoena dioptrica (Spectacled Porpoise) and Phocoena spinipinnis (Burmeister’s Porpoise) (Phocoenidae: Cetacea)

Abstract

The tongues of vertebrates reflect their adaptations to various feeding strategies,the types of food they consume, and the environments they inhabit. In cetacean, the macro- andmicroanatomical aspects of the tongues of few species have been studied. Here, we analyzed, forthe first time, the morphology of the tongues of two porpoise species (Spectacled and Burmeister’sPorpoises; juvenile and adults), whose biology is little known. We describe a range of novel aspectsrelated to ontogenetic morphological differences and document the finding of thermoregulatorystructures and components of the immune system. Differences between juvenile and adult individuals of the same species, as well as between juveniles and adults of both species, may be related totheir feeding types and/or geographical distribution. Additionally, we found a lingual vascularsystem, which has only been mentioned for baleen whales and the sperm whale (but never forsmaller-toothed cetaceans), that may participate in the thermoregulation of these individuals. Bothspecies have marginal papillae, but only in Burmeister’s Porpoise were small taste buds, possiblyvestigial, found. A better understanding of the biology of these two porpoise species will help todevelop useful strategies that contribute to their protection in the near future.