Do Animals Have Personalities?

Leaders and followers. What makes personality? Photo by Thang Nguyen at Wikimedia Commons.

The heart of science lies in existential questions such as "Who am I?" and "Where did I come from?" Yet somehow, these are the very questions that scientists tend to shy away from. It's as if we're afraid that by unraveling the mysteries of our world and ourselves, we'll be left with nothing but a handful of yarn. But many of us see the quest for personal understanding differently - as a journey to gain appreciation for all the complexities and rare events that came together to weave the glorious tapestry that is life. It is in this push and pull of wanting to know more while still wanting to maintain mystery that the study of personality lies. And for this reason (and many others), the science of personality has been woefully understudied and underappreciated.

This week I am at Accumulating Glitches pondering personality: What is it? How do we study it? And do other animal species have it? Check it out here.

And to learn more, check these out:

1. Réale, D., Reader, S., Sol, D., McDougall, P., & Dingemanse, N. (2007). Integrating animal temperament within ecology and evolution Biological Reviews, 82 (2), 291-318 DOI: 10.1111/j.1469-185X.2007.00010.x

2. Huntingford, F.A. (1976). The Relationship between anti-predator behavior and aggression among conspecifics in the three-spined stickleback, Gasterosteus aculeatus Animal Behaviour, 24, 245-260

3. Sinn, D., Moltschaniwskyj, N., Wapstra, E., & Dall, S. (2009). Are behavioral syndromes invariant? Spatiotemporal variation in shy/bold behavior in squid Behavioral Ecology and Sociobiology, 64 (4), 693-702 DOI: 10.1007/s00265-009-0887-2

Thanks Dad!

Daddy's girl. Photo from freedigitalphotos.net.

Let’s take a moment to appreciate just how special dads are. Across the animal kingdom, fathers caring for their young is the exception, not the rule. Paternal care is most often seen in species in which males can be pretty sure that they are indeed the father (for example, in species that fertilize eggs outside of the mothers’ bodies or in socially monogamous species). Mammals rarely act fatherly - Only 10% of mammalian species show paternal care at all. But among mammals, primates (including ourselves) are more likely to do so.

Dads do a number of things to care for their young: Depending on the species (and the individual), they may incubate them, provide them with food, groom them, keep them close to home, guard and protect them, and help them gain survival and mate-attraction skills. These behaviors are costly to a male, who could often be reproductively more successful by spending his time and resources courting more females. But they do it nonetheless.

Regardless of whether a dad is behaviorally involved with his offspring, he contributes a fair amount to the individuals we grow up to be. Dads provide nearly half of our genes, which are the instructions for the production of all of our bodies’ tissues and chemicals. These tissues and chemicals don’t just make up our physical bodies, they underlie much of our physical abilities, susceptibilities to disease, and behavior patterns (including personalities).

Just because about half of your genes are from dad and about half of your genes are from mom, doesn’t mean that you are strictly half-your-dad and half-your-mom. Imagine you are given two books of Thanksgiving Day recipes: Both books have the same recipe for turkey, so that is the one you are going to follow. But one book has a recipe for garlic mashed potatoes and the other has a recipe for plain mashed potatoes. If no one in your family likes garlic, you will likely follow the recipe for plain potatoes. In addition to choosing between recipes, you can also combine them: If one book has a recipe for stuffing with lots of garlic and onions and the other has a recipe for stuffing without garlic or onions, you could make stuffing with onions and no garlic. Your pairs of genes work in similar ways: if the two copies of a gene are different, you may get the trait of one of them or they could combine to give you an intermediate trait. If the versions of the gene are the same, you will likely just get that trait.

When something is made by following the instructions in a gene, this process is called gene expression. Not all genes are expressed equally everywhere: All of the cells of our body have the same genes, but the way they express in a particular cell determines whether that cell is part of a lung, a heart, a brain or something else. If for a particular gene the instructions in the gene from one parent are followed and the gene from the other parent is ignored, this is called parent-specific gene expression. We have several traits that occur as a result of dad-specific gene expression.

Your genes are lined up on doubled-stranded DNA, which is tightly coiled around proteins called histones. The DNA is then wrapped even more and packed into chromosomes. You have 23 different pairs of chromosomes in each cell, where one of each pair came from mom and the other came from dad.  Figure adapted from an image by KES47 at Wikimedia.

More variation is caused by the fact that two individuals with identical genes may not have identical traits. Our genes are encoded in strings of DNA, which are coiled around proteins called histones and then packed into chromosomes. Biological factors can cause the string of DNA to coil tightly around these histones, hindering access to any genes in that section of DNA. This reduces or even prevents gene expression from happening (Imagine what would happen if two pages of your Thanksgiving Day recipe book stuck together). Alternatively, other biological factors can relax the DNA string, increasing gene expression. Gene expression is often decreased or increased as a result of life experiences (such as social experiences, nutrition, or exposure to drugs and toxins). If a particular gene is decreased or increased this way in a sperm or egg cell, this effect can be passed on to the children (and often grandchildren and great-grandchildren and so on). This process of inheritance that is not a strict passing on of genes is called epigenetics. Epigenetics is a new and emerging field, but we have already learned that mothers that provide more parental care create lasting changes in their offspring that are passed down for multiple generations. It is likely that fatherly care has a similar effect. We also know that a father’s nutrition and exposure to drugs and toxins can pass several traits down the generational line through epigenetics.

Dads play a special role in the individuals we become. Their behavior with us, genetic makeup, and even personal experiences shape our physical appearances, health, abilities and personalities. If you haven’t yet, take a minute to say “Thanks, Dad!”

Happy (late) Father’s Day, Dad!


Want to know more? Check these out:

1. Curley, J., Mashoodh, R., & Champagne, F. (2011). Epigenetics and the origins of paternal effects Hormones and Behavior, 59 (3), 306-314 DOI: 10.1016/j.yhbeh.2010.06.018

2. Wilkins, J., & Haig, D. (2003). What good is genomic imprinting: the function of parent-specific gene expression Nature Reviews Genetics, 4 (5), 359-368 DOI: 10.1038/nrg1062


And a special thanks to Tony Auger, Cathy Auger, Stacey Kigar, and Robin Forbes-Lorman for their feedback.

Science Song Playlist

Are you looking for songs to add to your summer playlist? Try some of my favorite geeky life-science songs. Even bona-fide and popular bands (and apparently Daniel Radcliffe) can’t help getting into the science song scene!

Meet the Elements by They Might be Giants:

Pancreas by Weird Al:

The Bad Touch by The Bloodhound Gang:

And then there’s this…

Vote for your favorite in the comments section below and check out sciency song battles by actual scientists at The Science Life, Science Beat, Scientist Swagger and Battle of The Grad Programs! And if you feel so inspired, make a video of your own, upload it on YouTube and send me a link to include in a future battle!

Cicadian Rhythms: Why Does The 17-Year Cicada Emerge Like Clockwork?

Does your back yard look like this?
This swarm of periodical cicadas was photographed by Greg Hume at Wikimedia.

The 2013 Swarmageddon is here! After years of their absence, cicadas are overrunning parks, forests and communities all across the central-eastern United States. Periodical cicadas (from the genus Magicicada) are known for their synchronized emergence at 13- and 17-year intervals. Simply the fact that they can live this long is extraordinary: periodical cicadas have the longest life span of all insect species! But their precise 13- and 17-year emergence cycles have long been an evolutionary enigma.

Today I am over at Accumulating Glitches talking about periodical cicadas! I ponder questions like: How do periodical cicadas know when to emerge (and where are they before that)? How did different species living in the same regions get synchronized to the same cycle? And what evolutionary pressures led to life cycles that are precisely 13- and 17-years long?

Check it out here!

And to find out more, check these out:

1. Koenig, W., & Liebhold, A. (2013). Avian Predation Pressure as a Potential Driver of Periodical Cicada Cycle Length The American Naturalist, 181 (1), 145-149 DOI: 10.1086/668596

2. Koenig WD, Ries L, Olsen VB, & Liebhold AM (2011). Avian predators are less abundant during periodical cicada emergences, but why? Ecology, 92 (3), 784-90 PMID: 21608486

What Has No Legs And The Most Amazing Feet Ever?

 

This starfish photo is by Mike Murphy at Wikimedia.

We often think of echinoderms, like starfish, sand dollars, and sea urchins, as static ocean decorations. But if you watch them for long enough (or on fast-forward if you lack the patience) you will find that they have exciting motile lives. They hunt, they flee predators, and they mate. But how do they get around without any legs to stand on? Their secret is tube feet.

If you look at the underbelly of these critters, you will see lots and lots of little tubes with suction cups on the ends. These are the tube feet. Tube feet work through hydraulic pressure, the pressure created when incompressible fluids are pushed around. Tube feet extend when a muscular bulb at the top of the foot (called an ampulla) contracts, forcing water down the length of the tube. As the tube foot extends, it swings like a pendulum and then lands and plants itself on the surface. If the surface is smooth, muscles can contract causing the cup-shaped tip to form a vacuum, sticking the foot to the surface. When the ampulla relaxes, the tube foot retracts. To get around, the animal contracts and releases these ampullae in waves, causing the tube feet to extend and retract in a coordinated way that moves the animal in a particular direction (albeit very slowly). They can also use their tube feet in a coordinated way to manipulate objects, like food items.


If you take a close look at this Pycnopodia helianthoides, you can
see the structure of its tube feet. Photo by Stickpen at Wikimedia.

But tube feet aren’t just for movement! They can also be used for breathing, smelling, tasting, and even seeing! These abilities relate to the structure of the membrane in the tube feet. Echinoderms are slow moving and have a low metabolism, so they can get away with taking in oxygen and expelling carbon dioxide at low rates. The membranes in the tube feet are permeable to both of these gasses, and thus play an important role in respiration in these species. Additionally, tube feet often have chemoreceptors (receptors sensitive to smell and taste chemicals) and photoreceptors (receptors sensitive to light). It is largely through their tube feet that echinoderms perceive their world.

Echinoderm tube feet are far simpler than our own feet, with fewer muscles, no bones, and no toenails to trim. Yet their feet can look out for predator shadows, grab and taste prey and walk up walls. Sometimes, simplicity is just cooler than complexity.

Want to know more? Check these out:

1. Lesser, M., Carleton, K., Bottger, S., Barry, T., & Walker, C. (2011). Sea urchin tube feet are photosensory organs that express a rhabdomeric-like opsin and PAX6 Proceedings of the Royal Society B: Biological Sciences, 278 (1723), 3371-3379 DOI: 10.1098/rspb.2011.0336

2. Santos, R. (2005). Adhesion of echinoderm tube feet to rough surfaces Journal of Experimental Biology, 208 (13), 2555-2567 DOI: 10.1242/jeb.01683