Postdoc Spotlight: Dr. Jim Barnett

Glass frogs, ghost shrimp and clearwing butterflies use transparency to evade predators

A glasswing butterfly’s see-through wings help predators see right through them. (Shutterstock)
James B. Barnett, McMaster University

What would you do if you could be invisible? Would you use your power for good? For evil? Or just to avoid awkward conversations?

Transparency may seem like the simplest form of camouflage, but in the last year, research has revealed new complexities behind what some animals do to vanish into their surroundings.

In my research, I have experienced first-hand how effective and sophisticated transparency really can be. That story begins on a dark night in the pouring rain in the thick of French Guiana’s tropical rainforest.

My colleagues and I could only see as far as the beams of our headlamps would permit. We scanned the branches overhead for the source of a strange, high-pitched chirp: an almost metallic sound cutting sharply through the nightly cacophony of buzzing, rasping and squeaking.

Finally, our headlamps revealed a pair of googly eyes peering down on us, and we knew we had found what we had been searching for: a tiny glass frog (Teratohyla midas), only a couple of centimetres long. These bizarre frogs have transparent skin that lets us look directly at their intestines and bones — even at their beating hearts.

A frog with see-through skin and eggs on a black background
A transparent dusty glass frog with eggs visible through her skin. (Shutterstock)

Transparent, not invisible

Glass frogs are an amazing sight but seeing one raises an interesting question: what’s the point of having transparent skin if your predators can still see you, or your internal organs?

Let’s take a step back to see how transparency works and understand why we’re not constantly bumping into invisible creatures. Although transparency seems like an obvious type of camouflage — if that’s not too much of a contradiction in terms — becoming transparent is not easy.

We can see what’s around us because of how different objects interact with light. If something is opaque, light is either reflected or absorbed at its surface. For something to be transparent, light must instead travel straight through it.

But as light moves between transparent materials it can be bent and scattered. Think about how a straw in a glass of water appears to bend. This is refraction, and results from the different ways that light moves through air and water.

An animal’s body is made up of many organs and tissues, each with a different thickness, structure and chemical makeup. For the animal to be transparent, light must not be reflected, absorbed, scattered or refracted as it travels through each of these different layers.

Water-dwelling animals are at a clear advantage in terms of achieving transparency. Animal bodies are mostly made of water, and if a creature is already in the water, there is much less refraction and scattering of light. As a result, some of the most effective examples of transparency are oceanic species like jellyfish and shrimp.

A ghost shrimp on an aquarium bottom
Ghost shrimp are a popular aquarium pet. (Shutterstock)

On land, transparency is much rarer, but we are now learning that it can be very effective, sometimes in unexpected ways.

Clearwing butterflies, for example, are not bound by the colours and patterns other butterflies use to blend into specific backgrounds. Instead, their fully transparent wings mean that predators look straight through them, and they can blend effectively into any background.

Several large moth species have taken a different route. Instead of making the whole wing transparent, their wings have transparent panes that allow patches of the background to show through. By combining these transparent panels with opaque colours, the wing surface is broken up and the moth transformed into an unrecognizable mosaic.

Translucence

So, what of our little transparent frogs back in the rainforest? Here, transparency provides yet another form of camouflage. Unlike butterflies and moths with their transparent wings, these frogs have all of their internal organs on show, preventing true transparency. Instead, by combining their transparent underside with a green topside, the frogs become translucent: allowing some light through but not showing a clear image.

Their green colouring is a close match to that of a generic leaf, and the trick of translucency allows the frog to brighten or darken in keeping with the leaves around it. What’s more, the frogs’ legs are more translucent than their bodies, providing an extra advantage from a process called “edge diffusion,” further blending frog and leaf together in the eyes of its predators.

Transparency makes animals hard to find, but there are many ways for animals to achieve invisibility.

Understanding how animals evade detection can help us protect species as humans continue to change the natural world around us.The Conversation

James B. Barnett, Postdoctoral Fellow in Behavioural Ecology, McMaster University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Postdoc Spotlight: Dr. Cayleih Robertson

Baby mice ‘shut down’ to survive extreme cold on the highest mountain tops

North American deer mice pups have adapted to extreme cold conditions in an unusual way. (Shutterstock)
Cayleih E. Robertson, McMaster University

It’s early 2019, and biologist Jay Storz is struggling to breathe. He has just made it to the top of Llullaillaco, a Chilean volcano about three-quarters the height of Mount Everest, in search of a rumour.

Up this high, the air is thin, so there isn’t much oxygen and every step is an effort. Storz’s colleague, Mario Perez Mamani, spots movement among the rocks and Storz springs into action. He makes a successful grab and sits back, smiling. In his fist is the highest-dwelling animal in the world: A yellow-rumped leaf-eared mouse (Phyllotis xanthopygus rupestris).

Biologists Jay Storz and Mario Perez Mamani capture a yellow-rumped leaf-eared mouse.

I’m a Canadian biologist who is part of an international team of scientists that includes Storz; we study mountain top mice to learn how animals adapt to extreme environments. When it comes to living the high life, small rodents and lagomorphs (relatives of rabbits) are the undisputed high-altitude champions from the Andes to the Himalayas. Our study species, the North American deer mouse (Peromyscus maniculatus), is found from sea level to the summit of the highest Rocky Mountains, giving it the broadest altitudinal range of any mammal on the continent.

Surviving extreme environments as a pup

Mountain tops are some of the most extreme environments on Earth, and many summits are freezing cold all year round. For small mice, this can be a big problem. Their surface area is large relative to their mass, so they lose heat quickly.

Most warm-blooded animals like birds and mammals — endotherms — use energy from food to make their own heat and prevent their body temperature from dropping too low. Mammals use muscle to shiver or a special kind of fat called brown adipose tissue that makes heat without shivering. Both shivering muscle and brown fat need energy and oxygen to make heat.

Oxygen is in short supply on a mountain top but high-altitude mice have found a way around this problem. Highland populations of the North American deer mouse, native to the Rocky Mountains and the White Mountains, have evolved to maximize heat production. Their brown fat and skeletal muscle are fat-burning machines, and their specialized cardiovascular and respiratory systems deliver all the oxygen and fuel needed. Maximizing heat production means an adult mouse is more likely to survive on the cold mountain top.

Generating heat for survival

Some mammals are born with fully functioning heat-generating mechanisms. But for many species, these systems mature after birth. In these animals — including humans and mice — brown fat matures first and takes on early heat production.

At sea level, a baby mouse’s brown fat takes about eight days to develop. By that point, the babies, or pups, have tripled in size and are starting to grow fur. In another two short weeks, they will be old enough to leave home, but these first few weeks are treacherous. High predation risk and the energetic costs of growth mean less than half of baby mice born in the wild make it to adulthood.

But high-altitude mice have evolved a surprising strategy to help survive this early life stage: they let themselves get cold. Our research found that heat-producing systems of high-altitude deer mouse pups mature slowly compared to mice from lower elevations. When we looked at the genes responsible for these traits, we found that in both brown fat and skeletal muscle, the metabolic pathways associated with heat production were turned off in high-altitude pups, who had to rely on their mothers for warmth.

A hand holding a very young mouse.
A 10-day-old North American deer mouse pup. At this age, a lowland pup is able to stay warm using specialized heat-producing brown fat. Pups native to high altitudes have evolved to delay the maturation of this tissue. (Cayleih Robertson), Author provided

Mother rodents will sit on their pups while they nurse, keeping them nice and toasty. If pups can’t produce their own heat, their body temperature will slowly drop whenever the mother is away.

Tolerance for cold

Humans get hypothermia if our body drops by 2 C, so this may seem dangerous. But baby mice are remarkably cold-tolerant. Their body temperature can drop almost to freezing for hours, warming up again when their mother returns.

Our research leads us to believe that high-altitude mice conserve their energy use for growing, rather than staying warm. The combination of cold and low oxygen means that most mammalian babies (from humans to rats) can’t grow properly at high altitude.

The deer mouse is able to survive to adulthood at high altitudes because of its ability to slow down metabolic activity and conserve energy. Since this is the exact opposite strategy used by adult deer mice, our work highlights how important it is to study young animals if we want to understand how a species has evolved.The Conversation

Cayleih E. Robertson, Postdoctoral Fellow in Comparative Physiology, McCall MacBain Teaching and Leadership Fellow, McMaster University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Postdoc Spotlight: Dr. James McKendry

Dangers of a sedentary COVID-19 lockdown: Inactivity can take a toll on health in just two weeks

Being inactive even for short periods of time can affect health. (Pixabay)
James McKendry, McMaster University

As the world digs in for the second wave of COVID-19, flu season and winter, people also face a serious risk from reduced physical activity — especially older adults. Developing a plan to be physically active now will help you to stay strong and healthy through the long winter ahead.

While most people are aware of the benefits of physical activity — increased muscle and strength, reduced risk of disease, better quality of life and a lower risk of death — we tend to be less aware of how damaging and expensive reduced physical activity can be.

The loss of muscle and strength as you get older (known as sarcopenia) is something with which we are all familiar. We have all heard older family members say, “I’m just not as strong as I used to be,” or “I just can’t do that anymore.” But did you know that inactivity can make muscle loss a whole lot worse?

Health effects of inactivity

Physical inactivity can be forced on a person by an acute event such as a broken arm or leg or becoming bed-bound due to illness. However, reduced physical activity, such as step reduction, is a long-term choice that brings about multiple negative health consequences.

Insulin resistance (a warning sign for the development of type 2 diabetes), reduced muscle mass, increased body fat and poor sleep quality are just some of the health concerns caused by physical inactivity. Physical inactivity is also a major contributor to poor mental health and social isolation, which can be particularly problematic for older adults.

The health effects of inactivity start piling up within days.

A man and a woman with gray hair with small dumbbells in their hands.
The most effective way to maintain muscle is strength training. (Shutterstock)

McMaster University researchers have shown that reducing daily steps to fewer than 1,500 — similar to the activity level of people who are housebound during this pandemic — for just two weeks can reduce an older person’s insulin sensitivity by as much as one-third. The same period of inactivity also led to individuals over age 65 losing as much as four per cent of their leg muscle.

To make matters worse, once an older individual loses muscle, it is much more difficult to restore. Even when the research subjects returned to their normal daily routines, they did not regain their lost muscle. Effectively, older individuals simply don’t possess the same ability to bounce back that younger people do.

Regaining muscle requires deliberate effort. So, it truly is a case of use it or lose it.

Resistance is not futile

As a muscle physiologist with a keen interest in healthy aging, I’m pleased to report it’s not all doom and gloom. There are some things you can do — resistance exercise and eating your protein — to keep and even build muscle, get stronger and maintain your health for this winter and beyond.

The most effective way to maintain the muscle you have is strength training, or resistance exercise, which, put simply, means performing work against an additional load. And it doesn’t have to be complicated. If you have access to a gym to use free-weights and guided-motion machines, that’s great. However, there are many valuable alternatives you can easily do at home. Body-weight exercises such as push-ups, squats and lunges, elastic-band exercises and stair-climbing are just a few options that will help you to meet the World Health Organization’s latest physical activity guidelines.

A woman and her dog on a yoga mat.
Lower-intensity strength exercises such as yoga or Pilates can have significant physical and mental health benefits. (Pexels)

The good news for those who may be put off by the sound of resistance exercise is that doing any exercise with a high degree of effort will help you to get stronger and prevent (at least some) muscle loss. If, for any reason, performing resistance exercise isn’t possible, simply adding a walk, a bike ride or some lower-intensity strength exercises such as yoga or Pilates to your daily routine can have significant physical and mental health benefits.

Protein and muscle

Of course, a healthy diet and avoiding overeating are also critical to staying healthy. Protein-rich foods are particularly important, since they make you feel fuller for longer and provide building blocks for your muscles.

It is generally agreed that older adults need more protein than current guidelines suggest.

A good, easily achievable, target would be to eat 25 to 40 grams of protein with each meal (about one or two palm-sized portions). This equates to approximately 1.2 to 1.6 grams of protein per kilogram of body mass each day. Also, getting your protein from both animal (dairy, meat, fish, and eggs) and plant-based (beans, nuts, seeds, and lentils) sources may be beneficial.

Given how quickly inactivity and poor nutrition can sap your strength and your health, doing something now is the best way to power through the cold, dark winter and beyond.The Conversation

James McKendry, Postdoctoral Research Fellow in exercise physiology, muscle protein metabolism and aging, McMaster University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Information Session Handout

Click here to get a PDF copy of this handout

McCall MacBain Postdoctoral Fellows Teaching and Leadership Program

Applications are due August 14 at 5pm

This program supports the development of leadership and educational skills of Postdoctoral Fellows, training them with evidence-based teaching methods to build the next generation of world-class instructors. This program aims to create better teachers, and in turn, better students.

The program consists of 3 training opportunities:

  • Monthly Workshops aimed to teach essential teaching and leaderships skills
  • Weekly Journal Club readings designed to supplement workshops with core papers in education cognition research
  • Monthly Invited speakers presenting on cutting-edge education research

Sample Workshops

The series of workshops will build a foundation for program members to create their INSPIRE course module and pursue discipline-based education research.

How and why you should write an Op/Ed (Wade Hemsworth)

This workshop will prepare Program Members for how to write an Op/Ed article on the topic of their choice. Writing an Op/Ed will help members fine tune their communication skills by writing for a lay-audience about a complex topic. Op/Eds can be published on the McCall-MacBain program website and submitted to other publication outlets (The Sil, The Spec, etc.)

How to prepare/design a presentation or lecture (Joe Kim)

In these two workshops, Joe will first describe how he plans out his lectures (before converting them to PowerPoint). He will then teach the program members how to design PowerPoint slides (including multimedia).

How to give a lecture that incorporates Education Cognition research (Faria Sana)

Faria will give some background about active learning and why it is so vital to use in the classroom, as well as practice active learning techniques in the workshop.

How to write effective multiple-choice questions (Joe Kim)

This workshop will have program members practicing how to write effective multiple-choice questions (MCQs) using Bloom’s Taxonomy

Email Connie Imbault (Program Manager and Research Coordinator) with any questions

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