How tuna stay warm with cold hearts

Working with colleagues at Stanford University, Dr Holly Shiels and her team have discovered how bluefin tuna keep their hearts pumping during temperatures that would stop a human’s heart from beating. The research answers important questions about how animals react to rapid temperature changes, knowledge which becomes more important as the earth warms.

Bluefin tunaPacific bluefin tuna are top predators renowned for their epic migrations. They are unique among bony fish as they are warm-bodied and capable of elevating their core temperature up to 20°C above that of the water that surrounds them. They are also capable of diving down to the colder waters below 1000m, which affects their heart temperature. Dr Holly Shiels said:

“When tunas dive down to cold depths their body temperature stays warm but their heart temperature can fall by 15°C within minutes. The heart is chilled because it receives blood directly from the gills which mirrors water temperature. This clearly imposes stress upon the heart but it keeps beating, despite the temperature change. In most other animals the heart would stop.”

 

The team conducted their research at Stanford University’s Tuna Research and Conservation Center, one of the only places on the planet with live tuna for research. They used archival tags to track and monitor the fish in the wild, measuring the depth they swam to, their internal body temperature, and the ambient water temperature. They then used the data to set experimental conditions in the lab with single heart tuna cells, investigating how they beat. Dr Shiels explained the findings:

“We discovered that changes in the heart beat due to the temperate, coupled with the stimulation of adrenalin by diving, adjusts the electrical activity of the heart cells to maintain the constant calcium cycling needed to keep pumping. If we went through this temperature change our calcium cycling would be disrupted, our hearts would stop beating, and we would die.”

The next step for the team will be to test other fish species to see if this method of keeping the heart pumping at low temperatures is unique to bluefin tuna. Dr Shiels concluded:

“This research was about understanding how animals perform under dramatic environmental changes. This gives us a clear insight into how one species maintains its heart function over varying temperatures, something we will need to study further given recorded changes in the earth’s temperature.”

 

 

Research could improve breeding of endangered sea creature

Undulate ray - undersideFaculty scientists are attempting to map the genes of the endangered undulate ray, a protected British species which has declined sharply in the last few decades. Their data will be used to check the heritage of around 120 undulate rays in European aquariums, helping to pair up breeding adults and produce healthy offspring.

The team is investigating the diversity of the rays’ DNA to infer how inbred individuals are. Inbreeding causes frequent still-births and shortens the lifespans of offspring. Dr John Fitzpatrick, lead researcher on the project, says:

“This approach has never been used to aid captive breeding in rays before. It’s exciting to be working on a project with such a worthwhile practical application and strong scientific value.”

Marine biologist Jean-Denis Hibbitt has been managing the UK population since 2010 and is now monitoring the breeding programme across Europe. There have been 29 successful births in the UK since the programme was launched. Jean-Denis says:

“The first objective of the breeding programme is to provide undulate rays for public display to help raise awareness Ray Markingsof their plight. This added awareness, and the ability for people to identify the species, will subsequently allow them to question whether illegally landed rays are on sale in their local fishmongers. If numbers in the wild fall to a critical level, it is feasible that we could help with a reintroduction programme.”

Faculty student Iulia Darolti has taken DNA swabs from all 45 of the rays in British aquariums. She also accompanied Jean-Denis to swab two wild rays for comparison. Iulia says:

“It has been a challenging assignment. To expose the rays to as little stress as possible we developed non-invasive sampling techniques that allowed us to collect DNA from the skin. Travelling the country working with rays is something I never imagined myself doing, but it has been a very rewarding experience.”

PhD student Graeme Fox has been doing much of the laboratory work. He says:

“We developed a set of genetic markers to help discover whether the rays are related or not. After screening the DNA, we were able to identify regions that were likely to be highly variable. Our hope is that this data will enable Sea Life to plan the optimum management strategy to secure the genetic health of this beautiful and increasingly scarce species.”

Norwegian reindeer herds boosted by climate change

According to Faculty researchers and their colleagues from The Arctic University of Norway in Tromsø, climate change is not Reindeer in Norwaythreatening the reindeer of the Norwegian archipelago of Svalbard. Instead, their long-term study indicates that the population is thriving because of rising temperatures.

In one of the very few studies of animal population and climate change that has actually counted the number of animals instead of simply estimating, the research team discovered that the number of reindeer on Svalbard has increased by 30% in the last year.

Since 1979 there has been an annual census of the animals in the valley of Adventdalen, led by Dr Nicholas Tyler.  Over that period the population has increased in close parallel with winter warming, growing from around 600 animals in the early 1980s to an average of around 1000 in recent years. Dr Tyler said:

“Winter warming is widely held to be a major threat to reindeer across the arctic. But, in the high arctic archipelago of Svalbard, global warming has had the opposite effect. Our data provides remarkable confirmation of this counter-intuitive observation.”

A Faculty team led by Dr Jonathan Codd and Nathan Thavarajah assisted with this summer’s reindeer census. Dr Codd said:

“The results revealed a remarkably successful year for Svalbard reindeer. Despite very high numbers in 2013, the population reached a new record of just over 1300 animals. The substantial increase in the numbers of reindeer is linked with frequent and pronounced periods of warm weather last winter.”

Does it pay to be a lover or a fighter?

As mating season approaches male animals are faced with a question that can determine their chances of reproducing: shouldwalrus (1) they be a lover or a fighter? A recent study, led by Faculty researcher Dr John Fitzpatrick, has found that where animals fall on the lover/fighter scale depends on the extent to which they are able to ensure continued mating rights with females.

In species where fighting for the right to mate means greater control of the female, males invest more in weapons and less in testes size. But males produce large weapons and testes in species where fighting for females occurs both before mating – with weapons – and after mating – with sperm. Some males found fighting the most successful method. Others found fighting was only the first step in sexual relations and also had to rely on large testes to ensure their fertility.

The study looked at over 300 species and found that male ability to monopolise females for continued mating drove the way they evolved. Looking at mammals, birds, fish, insects, and flatworms, they discovered that males only traded-off investment in weapons and testes when they were sure that females wouldn’t fool around with another male when their back was turned. Dr Fitzpatrick said:

“We set out to see why some species show trade-offs in sexual traits and others do not – the answer lies in how successfully males are able to keep females from mating with rivals. We know animals try to get females in a couple of ways. When they fight for them they sometimes evolve weaponry – such as antlers, big body size, or big teeth. The other way they do this is not to bother to compete before they mate, but to have big testes and the highest sperm quality so that they can fertilise the most eggs.”

Dr Stefan Lüpold, from Syracuse University, said:

“You don’t get something for nothing in evolution. We wanted to see which species invested in weapons over testes. Some of these species invest in both, and that is a bit of a mystery. We will now look at whether maximising investment in sexual traits means you pay the price in some other aspect of life. Understanding the way animals reproduce is important as it helps us understand how species evolve and can prove important for conservation.”

‘Meet the Sloths’ with Faculty alumni Becky Cliffe

slothsSwansea University PhD student Becky Cliffe, who graduated from our Faculty in 2011, will be discussing her experiences of working at Costa Rica’s Sloth Sanctuary on the Animal Planet TV channel at 8 pm on Thursday, November 14th. ‘Meet the Sloths’ is an eight part documentary series which will feature dramatic sloth rescues, emotional releases, and all of the daily dramas associated with providing a home to over 100 orphaned and injured sloths.

The series will also feature a lighthearted look at the groundbreaking research undertaken in Costa Rica. Becky and her colleagues will be doing exclusive interviews and Q&A sessions in the coming weeks, so keep a look out for updates.