I stayed for almost 3 weeks, May and June 2013. My research focuses on the evolution of body plans of vertebrates and I address questions such as, why do some traits (e.g. number of eyes, digits, lungs, cervical vertebrae) hardly ever change, whereas others (e.g. tooth and nipple number) are extremely variable? What are the developmental mechanisms that underly strong or weak constraints on evolutionary changes?
I hope to understand more about the exceptional conservation of the number of neck vertebrae in mammals. Almost all mammals have seven cervical vertebrae, giraffes with a long neck and dolphins with extremely short necks. Changes of this number are strongly selected against, due to a coupling with congenital abnormalities. Many whales, especially balein whales, form an exception, because their seventh vertebra tends to bear a small rib, so that they effectively have only 6 instead of 7 neck vertebrae and one extra thoracic one with a rib.
The Swedish Museum of Natural History has a wonderful collection of mammal skeletons, including whales. It provides a unique opportunity for me to study the larger whales that are in the depot in the harbor. Synthesys provides a very good opportunity for visiting collections abroad. I have also visited other museums with synthesys grants, with good results, but I am particularly pleased by the excellent and well-organized collection at this museum.
I am a researcher at Naturalis Biodiversity Centre in Leiden, the Netherlands and I carry out research, supervise students and am involved in the organization of the 5th conference of the European Society for Evolutionary Developmental Biology in Vienna next year (22-25 July 2014, http://www.evodevo.eu/).
Everybody is extremely helpful. The whale bones are heavy and difficult to access, but no effort is spared to efficiently help me carry out the research.
I visited the modern art museum and the historical museum, which I both enjoyed very much. I can recommend to have lunch on the terrace of the modern art museum overlooking the water and city.
We study why the mammalian cervical number of vertebrae is strongly conserved and why the constraint has rarely been broken. We have shown for humans that mutations that change the number of cervical vertebrae are strongly selected against due to a coupling with congenital abnormalities. Sloths and manatees are exceptions with aberrant numbers of cervical vertebrae.
We found that sloths and manatees often have abnormalities that are similar to those of deceased human fetuses with an aberrant number of cervical vertebrae, e.g. fused cervical vertebrae and incompletely fused sterna. The extremely low activity of sloths and manatees presumably allows them to survive despite these abnormalities. Cetaceans exceptionally often have abnormal cervical vertebral numbers, usually due to rudimentary cervical ribs on the seventh vertebrae.
We hypothesize that stabilizing selection against cervical ribs is reduced in most cetaceans. Firstly, because the most common abnormalities associated with cervical ribs are normal traits in cetaceans, i.e. fused cervical vertebrae and incomplete fusions of the sternum. Secondly, because the absence of forward rotation of the front limbs will prevent other commonly associated abnormalities: pressure on nerves and blood vessels that run to the front limbs.
Furthermore, we hypothesize that cervical ribs are selectively advantageous in large, large-headed whales that lunge-feed (e.g. large Rorqual whales), or that ram their heads against competing males (e.g. Sperm and Killer whales), because these behaviours create huge forces on the neck and most cervical ribs strengthen the neck.
To test our hypotheses, we plan to compare cervical rib frequencies in large, large-headed cetaceans that lunge-feed or ram males with smaller and smaller-headed ones that do not lunge-feed or ram, or to a lesser extent. In addition, we plan to investigate the type of cervical rib and associations with (unusual) cervical rib fusions and other potential anomalies.
For more information about Frietson Galis research see: http://frietsongalis.nl/