Researchers have been studying the evolution of blowholes in cetaceans such as dolphins and whales.
A cetacean is an order of aquatic, mostly marine mammals that have a torpedo-shaped, nearly hairless body.
Rachel Roston, researcher at the University of Washington School of Dentistry, and V. Louis Roth, Duke University professor of biology, contributed to the research, which was published in the Journal of Anatomy.
Modern cetaceans breathe air, and as embryos, start with nasal passages that terminate at the tip of a snout like most mammals, but during development, the nasal passage switches to an angled path ending in a blowhole.
“The shift in orientation and position of the nasal passage in cetaceans is a developmental process that’s unlike any other mammal,” Roston said, according to Current Science Daily. “It’s an interesting question to see what parts remain connected, what parts shift orientation and how might they work together through a developmental process to bring about this change.”
The researchers measured the details of dolphin embryos and fetuses to gauge the change of the orientation of nasal passages and were able to discern three distinct phases of development.
Roston and Roth analyzed data from photographs and CT scans from the Smithsonian Institution’s National Museum of Natural History and the Natural History Museum of Los Angeles County to track dolphins’ embryonic and fetal development.
“We discovered that there are three phases of growth, primarily in the head, that can explain how the nasal passage shifts in orientation and position,” Roston said, according to Current Science Daily.
Roth and Roston’s model may inform how scientists view evolution of cetaceous animals.
“This model gives us a hypothesis for the developmental steps that had to occur to make that anatomical transformation happen, and will serve as a point of comparison for additional studies of growth and development in whales, dolphins and porpoises,” Roston told Current Science Daily.
Funding for the project was provided by Duke University, and Roston has also been supported by the National Institutes of Health.
