Dear MARMAMers,
We are pleased to share our publication on cranial asymmetry and aspects of sound production in odontocetes of the superfamily Delphinoidea. Our models revealed associations of the magnitude of cranial asymmetry with source level of echolocation clicks, and dive depth of the species. Laeta, M.; Ruenes, G.F.; Siciliano, S.; Oliveira, J.A.; Galatius, A. 2021. Variation in cranial asymmetry among the Delphinoidea. Biological Journal of the Linnean Society 132 (2): 414-430. Abstract: The remarkable directional cranial asymmetry of odontocete skulls has been proposed to be related to sound production. We investigated the variation in quality and quantity of cranial asymmetry in the superfamily Delphinoidea using geometric morphometrics and then investigated the relationship between asymmetry and aspects of sound production. In the average asymmetric shape, the dorsal aspect of the skull outline and interparietal suture crest were displaced to the right, while the nasal septum, nasal bones and right premaxilla were displaced to the left. The nasal bone, premaxilla and maxilla were all larger on the right side. Three delphinoid families presented similar expressions of asymmetry; however, the magnitude of the asymmetry varied. The Monodontidae showed the greatest magnitude of asymmetry, whereas the Phocoenidae were much less asymmetric. The most speciose family, the Delphinidae, presented a wide spectrum of asymmetry, with globicephalines and lissodelphinines among the most and least asymmetric species, respectively. Generalized linear models explaining the magnitude of asymmetry with characteristics of echolocation clicks, habitat use and size revealed associations with source level, dive depth and centroid size. This supports a relationship between asymmetry and sound production, with more asymmetric species emitting louder sounds. For example, louder clicks would be beneficial for prey detection at longer ranges in deeper waters. Please let us know of any questions! The paper can be accessed at https://doi.org/10.1093/biolinnean/blaa161, or you send me an email to mairala...@gmail.com requesting the pdf. Best regards, Maíra.
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