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A whale that made me grit my teeth

I recently had the pleasure and honour to publish a study that investigated the vestigial dentition of beaked whales in the New Zealand Journal of Zoology. My research area is on marine mammal teeth, as teeth can help us decipher the animal’s age, its diet, relationships and interactions with the environment. Vestigial teeth are reduced, rudimentary and without function in beaked whales. This was the first publication of its kind, sparking attention from marine mammal researchers overseas.

 

Cuvier’s beaked whale, Ziphius cavirostris © Moyna K. Müller, Dunedin

 

Cuvier’s beaked whale, Ziphius cavirostris © Moyna K. Müller, Dunedin

 

Beaked whales are rare and poorly-know mammals despite their large size.  Their open-ocean habits and deep-diving abilities make it difficult to study those animals in the wild. The little that is known about them comes from studying stranded carcasses and museum specimens. 

 

Juvenile Cuvier’s beaked whale skull (OMNZ VT2765), Otago Museum Collection

 

Juvenile Cuvier’s beaked whale skull (OMNZ VT2765), Otago Museum Collection

   

A skull of a juvenile of a Cuvier’s beaked whale from our Natural Science collections made me grit my teeth and soon I started studying it in more detail. This animal was special because it has a set of needle-like teeth still present in its jaw. This is pretty rare to see in museum specimens. Among whales and dolphins, beaked whales have the strangest dentitions. They lack functional teeth (no chewing and biting) and possess only 1 or 2 pairs of tusks in the lower jaw. They don’t chew their food and suck squid directly from the water into their mouths. Our specimen, in addition to the pair of lower tusks, also had 49 vestigial teeth preserved.

 

Unusual needle-like teeth in the jaw of this whale

 

 

 

 

 

 

 

 

 

 

 

 

Unusual needle-like teeth in the jaw of this whale

 

Vestigial teeth in beaked whales is not a new discovery to science, but they have never been studied in detail before. When I am not at the Museum, I am a researcher at the Faculty of Dentistry at the University of Otago. I was excited to find out more about those teeth and teamed up with Faculty of Dentistry’s Ludwig Jansen van Vuuren to study this animal.

We used a range of techniques from zoology and dentistry to study the specimen, such as skull and teeth measurements, and extracted one tooth for scanning electron microscopy, chemical analysis and mechanical testing. We found that, surprisingly, the vestigial teeth also have a layer of enamel the same as normal teeth do, and we characterised for the first time the chemistry and mechanical properties of those teeth (how strong and tough they are). These vestigial teeth had a similar shape and chemistry to normal teeth, but they were weaker possibly because they are not used for chewing and biting.

 

  Scanning electron microscope image showing the tooth structure

 

 Scanning electron microscope image showing the tooth structure

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

This shows that our collection stores hold many treasures and new science breakthroughs just waiting to be discovered!