Stretchy nerves help whales feed

Zoologists have discovered that stretchy nerves allow whales to balloon their mouths to capture prey during feeding dives.

A research team at the University of British Columbia (UBC) studied a type of whales – known as rorqual – and found a nerve structure in the mouth and tongue that can double in length and then recoil.

“This discovery was totally unexpected and unlike other nerve structures we’ve seen in vertebrates, which are of a more fixed length,” said Dr Wayne Vogl of UBC’s Cellular and Physiological Sciences Department.

Rorqual whales are among the largest group of baleen whales which include blue whales and fin whales. The specimens the researchers studied were obtained at a commercial whaling station in Iceland.

In the study, published in Current Biology, the team investigated the feeding mechanisms of rorqual whales and found that their nerve cells are packed in such a way that the individual nerve fibres unfold but never really stretch. This allows whales to balloon an immense pocket between their body wall and the overlying blubber. The team found that the volume of water engulfed during a lunge can exceed the volume of the whale itself.

[caption id="attachment_43257" align="aligncenter" width="400"] CREDIT: University of British Columbia.[/caption]

The scientists estimated that the blubber in fin whales expands by 162% in terms of distance around the blubber and 38% in length. They also found that multiple lunges can occur during a single dive, and the average time between lunges is over 40 seconds.

Dr Vogl added: “The rorquals’ bulk feeding mechanism required major changes in anatomy of the tongue and mouth blubber to allow large deformation, and now we recognise that it also required major modifications in the nerves in these tissues so they could also withstand the deformation.”

As part of other research, evolutionary biologists have suggested that lunge feeding is the development that allowed whales to reach their enormous sizes. The stretchy nerves therefore could be one of most important adaptations that led to their current size.

The team now plan to study how the nerve is folded during feeding dives.

“Our next step is to get a better understanding of how the nerve core is folded to allow its rapid unpacking and re-packing,” said UBC zoologist Professor Robert Shadwick.