Washington, District of Columbia 2021-08-05 12:17:11 –
August 5, 2021
Modern cetaceans such as dolphins, whales and porpoises are well adapted to aquatic life. They have fat to insulate and fins for propulsion and maneuvering. Today’s cetaceans also have a unique type of nasal cavity. It rises at an angle to the palate (or palate) and emerges as a blowhole from the top of the head.
This is a suitable adaptation for air-breathing animals at home underwater. However, as an embryo, the whale’s nasal cavity begins in a more typical position in mammals: parallel to the palate and exiting the tip of the nose, or snout. Whale experts have long been confused about how the nasal passages switch from a pathway parallel to the palate to an angle ending at the blowhole during embryonic and fetal development.
“Changes in the orientation and position of the cetacean’s nasal passages are a developmental process, unlike other mammals,” he said. Rachel Roston, Postdoctoral fellow, Faculty of Dentistry, University of Washington. “It’s an interesting question to see which parts remain connected, which parts change direction, and how they work together throughout the development process to bring about this change.”
New study with Roston V. Louise RossA professor of biology at Duke University, sheds light on this process. By measuring the anatomical details of the spotted dolphin embryo and fetal, they determined important anatomical changes that pointed the nasal cavity upwards. Their discovery, Release The Journal of Anatomy, July 19, is an integrated model of this developmental transition of cetaceans.
Roston, the lead author who began the study as a PhD student at Duke, said:
The three phases of growth are:
- Initially parallel, as the area between the palate and nasal cavity grows into a triangle, the area between them separates. This stage begins during embryogenesis after the face begins to form. This is the first two months after fertilization for spotted dolphins.
- The nose grows longer at an angle to the nasal passages, further separating the nostrils from the tip of the nose. This stage begins late in fetal development and can continue after birth.
- The skull is folded backwards so that the head and body are more aligned. This causes the nasal passages to rotate upwards, approximately perpendicular to the body axis. This stage begins late in embryonic development and continues to fetal development.
“While the nose is moving to the top of the head, many of the important angular changes are actually at the base of the skull, the base of the skull. That’s not necessarily what you expect to find!” Roston said. Said.
Roston says the three stages of growth do not evolve in a step-by-step process, but overlap in time. Together, they represent distinct developmental changes that move the nasal passages to the top of the head.
Roston and Roth used photographs of 21 embryo and fetal spotted dolphin specimens and anatomical data obtained from CT scans held by the Smithsonian Institution’s National Museum of Natural History and the Natural History Museum of Los Angeles County to model this model. Was developed. Specimens represented widespread embryonic and fetal development.
For comparison, they also obtained data from eight fin whale foets at the National Museum of Natural History and found that there was a significant difference between them and the spotted dolphins. In fin whales, the skull was folded in the area behind the skull, near where it joins the spinal column. In spotted dolphins, folding is concentrated near the center of the skull.
Models developed by Roston and Roth give scientists an idea of how whales evolve. These creatures began to evolve from the ancestors of four-legged land-dwelling mammals that had a nasal cavity parallel to the palate more than 50 million years ago. As cetaceans evolved, fumaroles gradually moved from the tip of the nose to the back of the nose and then gradually to the top of the skull.
In addition, the two species represent different branches of the whale family tree that diverged over 30 million years ago. Dolphins, along with porpoises, orca, sperm whales, and beaked whales, are commonly known whales. Fin whales belong to a group called baleen whales and are named after their unique feeding system.
“I was impressed with the two interesting discoveries that emerged from this work,” Ross said. “Both develop fumaroles, but there are important differences between baleen whales and toothed whales in how they turn their nasal passages during development. And, surprisingly, in the process of developing upward nostrils. With that, there are significant changes in the brain. “
In the future, examining more species from both strains will show whether all baleen and baleen whales are this different, Roston said.
“This model gives us a hypothesis of the developmental stages that had to occur to cause that anatomical change, and serves as a point of comparison for additional studies of whale, dolphin, and porpoise growth and development. “I will,” Roston said.
The study was funded by Duke University. Roston is also supported by the National Institutes of Health.
Now how did that get up there? New study sheds light on development and evolution of dolphin, whale blowholes Source link Now how did that get up there? New study sheds light on development and evolution of dolphin, whale blowholes