Collecting tissue samples from whales and dolphins
How can we get a tissue sample from a living whale?
That was a question scientists asked themselves and one of the many challenges faced by cetacean researchers. One of the first systems was developed by R. H. Lambertsen in 1987 and involved firing a biopsy dart from a crossbow. The disadvantage of this system is that you can’t modify the pressure of the hit and is less accurate than an air rifle.
Biopsy sampling using a cross bow. Photo Credits: (c) Reisinger et al.2014, PLos ONE
In 2002, Dr Michael Krutzen joined forces with Paxarm New Zealand and developed a new system. This system uses a modified veterinary gun to propel a dart. The advantage of using a rifle is that it is more accurate than a crossbow, which is vital when sampling small, fast-moving dolphins that are frequently encountered in tight groups. Furthermore, the system allows modification of the velocity (i.e. air pressure) at which the dart leaves the barrel depending on the distance to the animal and its size (Krutzen et al. 2002). It also has varying cutting tips to collect larger samples from whales and smaller from dolphins.
Paxarm Biopsy Sampling system. Photo Credit: Dr M. Oremus
This system provided a significant advantage, allowing for the safe collection of tissue samples of cetaceans. The main safety features are the design of the darts, the ability to modify the pressure of the hit and a scope that facilitates aiming. Paxarm darts have a wide barrel body made of light polycarbonate to spread the impact over a wider area and therefore, reduce the risk of injury by penetration. The dart has a stainless-steel cutting end that varies in size, depending of the animal to be sampled (i.e. larger for whales and smaller for dolphins) and it’s aerodynamic.
The disadvantages are the cost and the quality of the dart. The dart bodies and tails break easily and cost expensive. A full dart costs around $320 NZD.
The way the biopsy system works involves the dart being fired, it hits the whale, bounces off and floats, retaining a small tissue sample on the tip. We then collect the dart from the water with a net.
We have been using the Paxarm biopsy sampling system to collect tissue samples from whales and dolphins around the world for over two decades. We evaluated the short-term reactions and long-term responses of bottlenose dolphins after the collection of samples. Results agreed with previous findings showing that remote biopsy sampling causes only short-term reactions in both the targeted individual and its group (Tezanos-Pinto and Baker 2011).
Photos showing a biopsy dart a) hiting a Humpback whale (left) and b) after it hit bouncing back. (c) Dospinguinas.com
We went searching for whales on 10 occasions in Antarctica. We found whales on 7 days and managed to collect 12 samples (11 Humpbacks and 1 Minke whale). Passengers from MV Fram came with us in all trips. They spotted whales, collected data and shared the excitement of searching for whales, tracking them and observing how we collected samples. We later conducted a DNA extraction workshop, where passengers were able to extract the DNA of the samples we collected, how exciting!
One legendary day I sampled a humpback whale that was quite close to the boat, the dart hit the whale in a funny angle, bounced back on the same trajectory it went…meaning that I was able to catch it with my hand before it landed. I got an ovation from the surprised passengers in the boat!
Collection biopsy samples from Humpback whales in Antarctica. Photo Credits: (C) Yuri Choufour