ECR Spotlight is a series of interviews with early-career authors from a selection of papers published in Journal of Experimental Biology and aims to promote not only the diversity of early-career researchers (ECRs) working in experimental biology but also the huge variety of animals and physiological systems that are essential for the ‘comparative’ approach. Ayaka Saito is an author on ‘ Heart rate reduction during voluntary deep diving in free ranging loggerhead sea turtles’, published in JEB. Ayaka is a PhD student in the lab of Kentaro Q. Sakamoto at the Atmosphere and Ocean Research Institute, The University of Tokyo, Japan, investigating physiological adjustment of air-breathing vertebrates during diving.
Ayaka Saito
How did you become interested in biology?
I have always loved animals and was interested in the mechanisms and evolution of their behaviour. The more I learnt about animals, the more I wanted to study the physiological mechanisms underlying their unique behaviors such as flying and diving, and their adaptation to ever-changing environments.
Describe your scientific journey and your current research focus
During my undergraduate degree, I had a strong desire to study wild animals in their natural environment. I then discovered the field of biologging, in which small recorders are fitted to animals to record their behaviour and other data. This led me to join my current lab. I learnt that marine animals such as sea turtles dive very deep and long. Their diving ability was incredible, considering that they are air-breathing animals like humans. My current research focuses on one of the key physiological mechanisms during diving: the diving response. Specifically, I am studying the variation in heart rate and its control during diving.
How would you explain the main findings/message of your paper to a member of the public?
In aquatic air-breathing animals, physiological regulation including heart rate reduction is important for diving. Field studies on aquatic mammals and birds have shown that the intensity of heart rate reduction can vary depending on diving behaviour, such as the depth of dives and dive duration. However, in aquatic reptiles, the variation in heart rate during deep dives under natural conditions has not been fully investigated. Among marine reptiles, sea turtles have outstanding diving abilities. In this study, we measured the heart rate and diving behaviour of loggerhead sea turtles (Caretta caretta) under natural conditions for the first time. The heart rate during dives was lower than that at the surface to breathe. When the turtle dived deeper than 140 m, the heart rate dropped rapidly to approximately 2 beats per minute temporarily. The minimum instantaneous heart rate during dives was lower at deeper dive depths. Our results indicate that loggerhead sea turtles show variations in heart rate depending on their diving behaviour, similar to that shown by marine mammals and birds.
A loggerhead sea turtle (Caretta caretta) outfitted with recorders and electrodes for electrocardiogram measurements.
A loggerhead sea turtle (Caretta caretta) outfitted with recorders and electrodes for electrocardiogram measurements.
What do you enjoy most about research, and why?
I really enjoy the scientific process of exploring various questions in nature. The biologging approach is very exciting because it allows us to measure the behaviour and physiological states of animals that we cannot observe visually. However, there are many difficulties in measuring the behaviour and physiological states of wild marine animals. For example, sea turtles cannot be recaptured once they have been released into the sea, so we had to charter a boat and search for a recorder that had been detached from the turtles at sea. Sometimes the recorders could not be found due to some trouble. However, after overcoming these difficulties, the moments when new data were obtained were also enjoyable.
What is the most important piece of equipment for your research, what does it do and what question did it help you address?
The most important equipment for my research is the electrocardiogram (ECG) recorder. Its capacity to record ECG data at a high sampling rate allowed detailed analysis of the changes in heart rate associated with diving behaviour. The waterproof adhesive material covering the electrodes is also important to prevent water intrusion, which can cause noise in ECG data. After trying various materials, the waterproof adhesive bandage that I used to use when I was injured was the best for the measurements. It allowed us to obtain ECG data with less noise and to calculate the heart rate more accurately.
What is your favourite animal, and why?
I like all animals, but penguins are my favourite. They are cute and make me happy just to look at them. I am also very interested in the fact that, although they are birds, they cannot fly, but they can dive very well. I would like to study them one day.
Ayaka Saito's contact details: Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan.
E-mail: [email protected]