Track the turtles

Those of you who love Neuroscience and Neuroscience only, I must warn you: This is not a Neuroscience-related article! This article is about turtles. And as much as I would like to get an insight into these creatures’ minds, knowing how invasive the current techniques¬†are and that there is not yet a vast literature on this subject, the today’s article will not consider the brain.

Why turtles then? Are they interesting enough for us to mind them? The answer is YES! I am an animal lover, and I believe that all beings of any sort are fascinating and that they deserve to live a happy life. That is not how I became so amazed by the turtles, though.

This summer I volunteered in Kefalonia (one of the Ionian Sea’s Greek islands) for two weeks to work in the only sea turtle conservation there. I spent a wonderful time and I came back with lots of memories and things to share. But the most important thing I gained through my experience there was what I have learnt about sea turtles. The organisation that runs the conservation volunteering projects is called Wildlife Sense. ¬†You can have a look and if you are turtle lovers and enjoy adventures, you should definitely sign up for volunteering work, which I can assure you, is very rewarding.

As volunteers in the egg-laying season, our task was to take many types of measurements, observe and analyse turtle tracks, the sand, the temperature on the beach, the amount of light and estimate light pollution, find turtle nests, relocate (if necessary) these eggs, tag and microchip the adult turtles etc. It might not sound so exciting, but I felt like both a researcher and an animal protector and I acquired a lot of skills needed for future experiences of this sort and much more.

Know your sea turtle

It is important to know the difference between a turtle and a tortoise. The latter are the ones who walk on the ground and can retract all four limbs and head. Turtles have fins (or flippers) and these are not completely retractable. There are 7 species of sea turtles: leatherbacks (the biggest), loggerheads, greens, kemp’s Ridley, olive Ridley, hawkbill and flat-back. On Kefalonia one can only find loggerheads (Caretta caretta)¬†and some say, greens (but we’ve never seen those).

A few anatomy things

Loggerheads are big turtles, with 80 to 110 cm in carapace length and contrary to what some of you might think, they are very strong and can be very aggressive: they can bite and scratch with their claws (one of the volunteers in my team got her trousers ripped off by a turtle). Marine turtles, just like tortoises, terrapins and other reptiles, are covered in scutes and scales. The scales are on the carapace, while the scutes cover the skin and the ones on the head profile are like human fingerprints Рthey are unique to each turtle. There are some differences between male and female turtles, including size (females tend to be a bit bigger), but to be sure about the gender, look at their tails: males have a tail coming out from underneath the carapace. Nevertheless, some males hide their tails from time to time, giving researchers a hard time about gender identification.

Laying eggs

When a turtle needs to lay her eggs, some very interesting things happen: she usually returns to the same beach she was born on, even though they travel long distances and get in the ocean throughout their lifetime. For that, she uses something called¬†geomagnetism¬†which involves¬†Jacobson’s organ for olfaction and the geomagnetic orientation trigeminal system. When she comes out of the sea, a turtle pays a lot of attention to the environment: she wants to make sure there are no predators and that the sand is good enough, so she is very focused on anything that is moving, as well as noises and lights.

Loggerheads alternate their tracks when they move on sand and the tracks are a good indicator for the directions to and from¬†the sea. When they start digging the nest, marine turtles use their front flippers to remove the sand around them, while their bodies form a distinctive (and very relevant for researchers) shape in the sand –¬†a body pit (or an extended body pit). They lay around 100-120 eggs, but due to external factors only few of them (1 in 1000) can reach maturity and lay¬†eggs. Temperature determines the embryo’s sex – eggs kept warmer become females – but it can also affect the embryo’s survival. Therefore, the depth of the whole is¬†very important (16-34 cm from the top five eggs), because it significantly influences the temperature of the¬†egg chamber.

It is said that turtles cry after they lay their eggs. There is a grain of truth here, the turtle does indeed drop a few tears, but this is not because she is sad to leave her babies out in the nowhere (even though, that does not mean she has no feelings of this sort, we do not yet know). It all comes down to maintaining the salt balance and those tears actually help the turtles excrete the excess of salt in their eyes.

After she lays her eggs, the turtle returns to the sea and she might never see her babies again. The hatchlings come out of the eggs after one month and a half-two months and orient¬†themselves towards the sea using light (the sea is the brightest thing on the beach if there’s moon light to reflect in it). They show a¬†tropotactic behaviour¬†(they compare intensities in both eyes and move accordingly). Light pollution from artificial¬†lights on the beach is fatal for many hatchlings¬†(amongst other factors like predators), because the poor babies often get confused and don’t know where to go. Sea turtles do not perceive red light, so volunteers were advised to use red lights when looking for turtles at night, in order not to disturb the egg-laying process. The wavelength of light perceived by¬†marine turtles usually ranges between 360 and 600 nm; green turtles see yellow light and do not mind it, while loggerheads are xanthophobic¬†(averse to yellow-orange light). Once in the sea, baby turtles¬†can encounter many other dangers, but if they survive, they swim to other seas and oceans and they can live up to 60 years.

A sea turtle story’ link – A MUST WATCH

As for genetics…

It was discovered that male turtles do not have an SRY gene on their Y chromosome, although the presence of another gene, the SOX9 gene, influences the formation of testies. ¬†Steroidogenic genes¬†are also thought to be involved in sex determination, along with the¬†DAX1 nuclear receptor protein¬†(encoded by¬†an ‘antitestis’ gene) and the¬†anti-m√ľllerian hormone¬†(for testis differentiation).

Marine turtles, and turtles in general, are still a mystery for biologists, but what has been discovered so far about them did nothing but prove how marvellous these animals are. If what you have read in this article aroused your curiosity, I can only hope you will allow the turtles to amaze you in the future as well.

Below, I have inserted a link to a very interesting paper that raises awareness about relocating eggs and explains it from a different point of view.

For further information:

Lutz et al., 2003. The biology of Sea Turtle, Vol. 2. CRC Press

Paper

Wildlife Sense link

Emotions and the brain

Once upon a time, I promised I was going to write an article about how emotions affect our decision-making and why it is actually important not to ignore the feelings we have in certain situations…For several, unexplainable reasons I kept postponing this idea, and for that I am very sorry. Having said that, there is no better way of making up for this than to finally keep my promise. So, here we go!

I think I should start off with a small mention:¬†emotions¬†and feelings¬†are distinct things, according to neuroscientist Joseph LeDoux.¬†As he well puts it: “…feelings are what happen when we become consciously aware that our brain is reacting to some significant stimulus,” while it is possible that some brain structures, such as the¬†amygdala “respond to emotional stimuli without the organism being aware of the stimulus.”

In order to achieve a better understanding of what the process of forming emotions involves, scientists talk about emotional experience and emotional expression. The latter refers to body manifestations and behaviours in response to certain stimuli, for example changes in facial expression, heart rate, sweating, skin conductance etc. It has been a subject of debate for several decades whether emotional experience or emotional response is the one responsible for formation of the other, or that they act independently. It is now believed that different emotions depend on specific parts of the brain and are determined by different neural circuits.

But why should we care about emotions in the first place? Some of you might find it strange, but emotions are intensely interconnected with reasoning and decision-making. And no, I don’t mean that they impair the process of making the right decision, it’s actually quite the opposite: most of the times we need emotions in order to be able to do what is best for us in a certain situation.

An interesting case: Phineas Gage 

A man who has gone down in history for surviving a terrible accident at the work place, but maybe mostly because of his importance in understanding the role of emotions in decision-making, is a late 19th century foreman, Phineas Gage. He had been hired as a foreman on a railroad construction site in Vermont and one of his tasks was to sprinkle explosive powder into blasting holes. This sounds like a dangerous thing to do, but Gage was regarded as one of the best people in this field: he was said to be very efficient, energetic, balance-minded, tenacious, a smart and successful business man etc.

One moment of carelessness dramatically changed his life forever, and at the same time had a huge impact on the way scientists began to think of emotions. The powder exploded and a tamping iron entered¬†Gage’s head under his left eye, passing through his left frontal lobe, and exited the skull, leaving a hole which measured more than 9 cm in diameter.

Gage survived, but he “was no longer Gage”, as his friends and acquaintances used to say. Apart from losing vision in his left eye, the man had no motor or sensory deficits, he could hear, touch, sense, walk and talk. It was his personality that was completely changed. He became capricious, irreverent, impatient, and behaved as if he did could not predict, nor care about any professional or personal failure. He was soon fired and¬†found different jobs over time, most of which were related to the accident and the iron rod, which had turned him into some sort of freak.

Some explanations and brain functions

The limbic system is probably the first to come to mind if you refer to brain areas involved in emotions. It consists of structures around the thalamus or in the temporal lobe, such as the amygdala, the hypothalamus, the limbic cortex, the cingulate gyrus, the fornix, the corpus callosum etc. Each one of these structures is involved in specific types of emotion and in triggering certain behaviours or responses through the autonomic nervous system. For example, the amygdala is linked to fear and aggression. Different regions (nuclei) in the amygdala are associated certain functions, so that both emotional expression and experience require the amygdala in order to be formed. Projections from amygdala are sent to the hypothalamus, which determines the autonomic response, the brain stem for behavioural reaction and the cerebral cortex, which is involved in emotional experience. The amygdala is also thought to play a role in enhanced emotional memory.

Regulation of specific emotional behaviours depending on the limbic system is facilitated by one of the major neurotransmitters, serotonine. Neurones containing serotonin originate in the brain stem (in the Raphe nuclei) and send projections to the hypothalamus. Serotonine is associated with a decrease in aggressive behaviour, but at the same time is involved in dominance, as proven by studies in rhesus monkeys.

The Papez Circuit¬†(named after the neurologist James Papez who came up with the idea of an “emotional system”) is composed of¬†interconnected anatomical structures (many of which are part of the limbic system) that link emotional expression and emotional experience together. Papez proposed that¬†the cingulate cortex¬†determines emotional experience, while the major structure involved in emotional expression is¬†the hypothalamus.¬†

Below I have inserted a diagram showing the Papez Circuit, based on information from Bear et al. Note that the hippocampus is now thought to have less importance in the process of emotion formation.

The Papez Circuit

The discussion above¬†does not fully explain what happened in the case of Phineas Gage. There is much more to emotion than that! Given the fact that the iron rod severely affected Gage’s frontal lobe, we should definitely focus our attention on this structure, too.¬†The frontal lobe and the prefrontal cortices¬†are involved in planning, reasoning, social behaviour, motivation, defining our personalities etc. Damage to these regions, especially to the ventromedial prefrontal cortices, results in decision-making impairment. While the intelligence and the other body functions remain intact, the patient who has suffered the damage is no longer able to exhibit normal social behaviour. The patient becomes emotionless and this lack of emotions and self motivation makes them¬†incapable of making the right decisions.

If instead of the ventromedial prefrontal cortices, another region of the prefrontal cortices is affected, there is a very strong possibility that the patient’s intellectual abilities are compromised, along with their ability to form emotions. This region is called the dorsolateral prefrontal cortices. The person with a damage in this brain area would encounter severe difficulties when it comes to operations on numbers, words, space etc.

Another brain structure involved in the process of emotion forming is located in the¬†right hemisphere.¬†If the somatosensory cortices of this area are injured, the result would be similar to what can be seen in the case of a damaged ventral prefrontal cortex, but there is something more…the processes of basic body singling are also disrupted. This can be observed in patients suffering from anosognosia,¬†a disease in which the patient is unaware and denies their disability.

I have tried to comprise a lot of information and simplify things as much as possible. If you managed to get here with both eyes open, I couldn’t be happier. Hopefully, you can see now why we should also “think with our hearts” when we need to decide¬†about a certain situation…because the “heart” is somewhere in the brain and it knows better than us what we need to do.

For further information:

Antonio Damasio,1995. Decartes’ Error. Vintage Books

Bear et al., 2006. Neuroscience ‚Äď Exploring the Brain. s.l.:Lippincott Williams & Wilknins pp. 564-581

Article about Phineas Gage

Image by Isuru Priyaranga