As Tears Go By

A look at animal and human tears

Children cry easily and even after a minor bump or hurt will shed tears. Adults may feel pain, cry and scream when hurt, but unlike children will not shed tears. An adult’s tears are associated with emotions or may be caused by some disorder, an eye infection or irritation, but not pain. And animals? They, too, have lacrimal (= tear) glands and can have watery eyes as the result of an infection or as part of a physiological control to remove excess salt from the body, but apparently not in connection with an injury. Sea turtles and a few other reptiles remove excess salt not only via their kidneys but with the help of their orbital eye glands as “white tears of saline” that drip out of their eyes.

Although human tears are not white, but watery, transparent and very slightly sticky because of mucins in them, they too contain salt  – as do, in fact, the tears of all land vertebrates that may not ‘shed tears’ but use the lacrimal fluid to lubricate their eyes and keep the cornea moist. Chemically tears are mostly water (ca. 98%); and apart from salts the lacrimal fluid contains a cocktail of amino acids and proteins, antibacterial enzymes and minute quantities of stress hormones. A tear’s chemical composition depends on the cause of its shedding and varies on whether the tear’s function is to wash out dust from the eye, to fight off irritants such as fumes (smoke or onions come to mind), to lubricate the eye’s surface, and as a response to physical pain and emotional upheaval. The autonomic nervous system through its parasympathetic branch governs the production and release of tears from the lacrimal glands, which are located in the upper region of the eye’s orbit. The tears are stored in the lacrimal sac near the nasal corner of the eye; from there the fluid via lacrimal canaliculi is released into the eye upon a signal from the parasympathetic nerve’s acetylcholine transmitter. In healthy individuals, there is a constant release of minute quantities that are distributed with each eye blink across the cornea, but of greater amounts if required. Excessive fluid is drained through the nasolacrimal duct and causes the ‘sniffle’ during weeping.

Basal tears are continually-produced via the 5^th cranial nerve’s innervation to keep the eye’s cornea moist and to prevent bacterial infections. In humans, about 0.75-1.1 ml of the liquid is produced each day. Reflex tears are produced when the eye is irritated, and through their copious amount and high water content function to remove the irritation from the eye. Psychic, also known as ‘emotional’  tears, occur in response to strong feelings, which could be sadness, but also joy, stress and  physical pain. Because these tears contain such natural painkillers like leucine-enkephalin and prolactin, it may explain the role of the parasympathetic nervous system and that “a good cry can feel relieving”.  But it does not explain why men shed tears less often than women, a fact that is often explained with the traditional roles men and women are expected to play in life (the advice “boys don’t cry” is a case in point).

The fourth reason for tears is related to diseases and the release of tears accompanying other activities (e.g. yawning). Although elephants have been described as shedding emotional tears, crocodile tears are not an expression of emotional distress, but the result of compression of a nerve that controls the jaw muscles during feeding. In humans suffering from Bogorad syndrome “crocodile tears” also accompany swallowing. Reference to tears can generate resolve (Churchill’s famous “Blood, Sweat and Tears” comes to mind); tears evoke empathy: children know that (and actors train to shed tears at will) and tears appear in poems and songs (the record “Tears on my Pillow” is in my collection) and who wouldn’t remember Marianne Faithful’s beautiful song “As Tears Go By” or Eric Clapton’s touching “Tears in Heaven” (which I heard it for the first time in Chile in 1993). I actually heard of people who shed tears when listening to it.

© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2022. Unauthorized use and/or duplication of this material without express and written permission from this site’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to V.B Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com with appropriate and specific direction to the original content.

Bumble Bees Near the North Pole

Is that a fact?

It depends, of course, what you mean by “near”: England seems quite near for birds that fly from France across the Channel (la Manche) to reach the English coast, but for insects it sure is a long, long way. The distance from the southernmost edge of Greenland to its northernmost coastline is over 2,600 km, which is (when I heard that bumble bees live in North Greenland) ‘only’ about 800 km away from the North Pole, corresponding to the distance between San Francisco – San Diego or Le Havre in the north and Marseille in the south of France). I was pretty amazed. How can these insects survive there?

It was at the South Korean Ecology Conference that I saw a poster that a scientist by the name of Dr Won Young Lee had put up to report on his research in Greenland as well as in Antarctica. I was curious to meet that person, as there simply aren’t many researchers who have been active in both Arctic and Antarctic environments. When I explained to him where in Greenland I had been and that I had also visited Antarctica nine times, he told me about his research and then happened to mention how surprised he was when in North Greenland at a latitude of nearly 83° N, he had seen bumble bees. I had come across two species of bumble bee (Bombus polaris and B. hyperboreus) in southern Greenland, but had not been aware of the fact that these cold-hardy insects would be distributed to the furthest north of the island. It hadn’t been an interest of my Polar research till then (despite an electrophysiological study of mine in 1981 of the functional properties of the eye of the North Finnish species B.hortorum). 

But now I wanted to know more and requested to join the next expedition to North Greenland (which, however, did not happen as it ‘fell victim’ to the Corona pandemic) to catch some of these bees. Luckily, though, Dr Lee had preserved a Bombus polaris queen bee from North Greenland and with the help of my Iranian colleague Dr Saeed M. Namin (a skillful molecular entomologist) and the support of our Department’s Head (Prof Chuleui Jung), we embarked on a study to investigate the phylogenetic relationships between all known “High Arctic” bumble bee species and to speculate how B. polaris  got to North Greenland and how global warming could possibly affect its distribution and survival there.

We concluded that the female specimen we analysed was most closely related to Canadian populations of B. polaris. Geographic proximity, occurrence of B. polaris on Ellesmere Island 500 km to the west and wind direction were thought likely factors that aided B. polaris to establish itself in North Greenland. A moderately high level of genetic diversity of B. polaris in Greenland was determined reflecting the successful adaptation of the species. However, bumble bees need food and shelter and only the queen overwinters. But where and how in North Greenland’s permafrost-hard soil is there sufficient shelter? And how about pollen and nectar for food? In the broader context of entomological life in the high Arctic, our results on B. polaris allow us to conclude that the survival of pollinating species in the high Arctic under the changing climate scenario depends not only on the weather but also on an individual’s opportunity to continue to locate suitable food sources, which in North Greenland are provided by flowers of the abundant Pedicularis spp., Salix arctica and Ericaceae of the region. Other plants with a northern distribution like Stylophorum sp. and crowberries can be considered pollen and nectar providers, respectively, and are likely to be also visited by B. polaris. Will climate change affect them?

According to one of the foremost Arctic bumble bee researchers (Dr Grigory Potapov), some High Arctic species used to occur much more widely in the past. Will it help us predict the fate of B.polaris? More research may be needed and I’d love to be part of it. My next destination? I hope it’s North Greenland!

© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2021. Unauthorized use and/or duplication of this material without express and written permission from this site’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to V.B Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com with appropriate and specific direction to the original content.

Yawning? 

I Hope It’s Never Happened Reading “Bioforthebiobuff”

At high school we had a history teacher by the name of Dr. L., who had spent 11 years in a Soviet prisoner-of-war camp before being released in 1955. He used to put the history book on the classroom’s desk, positioned himself comfortably on a chair near the side of the classroom and asked some of the best readers in class to take turns to read from the book. That’s how his lesson went. Although he can perhaps be forgiven for killing our interest in history by this behavior of his, his antics were also a cause of hilarity, especially when we noticed the regularity of his yawns and could predict when another big yawn of his would appear (silently counting: 14, 15, 16, 17, “yawn”!). But what made him yawn so much? Boredom, lack of sleep, or something else? And why is it so ‘contagious’? Mirror neurons perhaps?

The common view has always been that yawning was related to a lack of oxygen, a build-up of carbon dioxide and a room that was too warm and stuffy. Consequently, a call to open the window and let in ‘fresh air’, could often be heard in situations where people were seen to yawn frequently and appear sleepy. Yet, numerous studies have shown that lack of oxygen and carbon dioxide increases are by themselves not a cause of yawns. The situation is complex and although the amount of yawning appears to be correlated with boredom and sleepiness, it must leave us puzzled to notice that even after a good night’s sleep we wake up and then more often than not yawn upon awakening. Why yawn at that time? And cooling the brain in the morning or at other times by gaping wide: does it make sense? The idea that yawning is a component of thermoregulation has not yet achieved the acceptance it hoped to get.

If we examine objectively what happens during a yawn, we notice that it involves a wide open mouth and a long and deep inspiration of several seconds, sometimes accompanied by some soft vocalization during expiration. It is an involuntary behaviour that can be triggered by thinking and reading about yawning and/or seeing someone yawn. Yawning is communicative and is generally coupled with inactivity, lethargy and sluggishness (sometimes worry as well). To suppress the yawns can be difficult, especially when hindered to move as in boring meetings, lectures, and waiting rooms. And this actually gives us a clue: our bodies need us to stretch occasionally, to shake our arms and legs, to release tension.

The realization that yawning is a stretch response has been gaining attention ever since it was observed that when hemiplegic individuals that not normally can move their arms do move them when they pandiculate with an associated yawn. Yawning when pandiculating, i.e. stretching and thereby contracting and relaxing muscles, reduces muscular tension, is resetting and restoring the control over muscles, something that is critical for posture and movement and something that yoga instructors constantly emphasize. Obviously, the fact that the slow expiration following a yawn is associated with a sympathetic activation marked by an increase in blood pressure, suggests that at the start of the yawn it is associated with a sympathetic suppression that favours a parasympathetic dominance. This might also explain the observation of a paraplegic’s involuntary movement of its toes during a yawn.

Yawning must have ancient roots in the animal kingdom, for it can be observed in almost any animal group and is not even restricted to vertebrates alone as this delightful recording of a yawning leech shows here . Lizards, frogs, toads and even fish can be seen to yawn and all of them are ectothermic (often referred to as ‘cold-blooded’). As such, they would not be expected to use the yawning response to cool their brains as has been suggested for mammals, but could find yawning useful in connection with stretching and therefore the restoration of muscle control. Yawning:  a kind of physical exercise without having to get up? I think that that is a distinct possibility.

© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2021. Unauthorized use and/or duplication of this material without express and written permission from this site’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to V.B Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com with appropriate and specific direction to the original content.