Blind as a Bat: Certainly Not

And also not bad or beastly   

In the early 1980s in Finland I met a bat researcher who explained to me a device called the bat detector which works by changing the high frequencies of a bat’s cry, inaudible to humans, into audible lower frequencies. That device allows the researcher to look for the bats that s/he then knows are around. Sadly, that very bat researcher died in 1985 after being bitten by a bat that had transmitted the rabies virus to him. This was such a rare and isolated case in Finland that it made headlines and led to a hiatus in Finnish bat research. Despite the fact that bats can indeed harbour loads of viruses and other pathogens (but don’t get sick themselves) and may be pestered by parasitic flies of the families Nycteribiidae and Streblidae (because of the bats’ habit to be colonial, which involves close contact between individuals), they are, generally, of absolutely no danger to humans. Their life is an alien life that can last 40 years, a life in the dark, a quiet and secret life (except that of the thousands of fruit bats in Australia roosting in trees of parks and gardens). However, bats are absolutely fascinating mammals and earlier I already pointed out some of their remarkable reproductive adaptations with suspended pregnancies and (in some species) milk-producing “father bats” helping “mother bats” in parenting.

There are at least 1200 species of bats, which means 20% of all mammals can fly. Their sizes range from that of a bumblebee to that of a small dog but none of them is blind; a fossil Burrowing Bat from New Zealand is estimated to have weighed 40 kg. Their food habits are amazingly varied: some tropical species are important pollinators and visit flowers, others munch leaves or attack fruits; many species feast on insect pests like moths and beetles that fly around at night and some (the fish-eating bats) have even become accomplished piscivores. The notorious vampire bat of Central and South America is the only mammal that depends on blood for its diet, but although that may not be very nice, their habit of sharing a blood meal through a kiss with a colony member that hadn’t been able to find a food source shows an altruistic side. It is well known that bats form friendships with other bats and that bat orphans will be adopted by not even genetically closely related individuals of a colony. Bats are not blind but locate obstacles and food in the dark by echolocation (which I mentioned in an earlier blog).

Scientifically referred to as Chiroptera (from Greek “cheir” = hand and “pteron” = wing), bat wings are the result of a thin membrane between four of their fingers and are thus analogous to bird wings. Being able to fly, bats colonized far away islands like New Zealand, Hawaii and Galapagos, but being nocturnal only a handful species could survive in northern Finland despite the abundance of mosquitoes and other insects in the summer (only daylight in summer nights). The cold and long winters are no problem: many species enter into a state of torpor and hibernate in caves or other sheltered places. To rest and roost, most bats hang upside down, which required special adaptations with regard to their hind extremities, joints, muscles, tendons and circulatory system (a human would die if in an upside-down position for too long). An exception, as Daniel Riskin & Paul Racey could show in 2010, are sucker-foot bats like the Madagascar Myzopoda aurita: it clings head-up to leaves using specialized pads on its wrists and ankles.

I’m not aware of bats other than the large fruit-eating species being consumed as food by humans, but falsely accused of being a symbol of evil in many western societies, people should focus on the charming side of bats and revere them as harbingers of Good Luck and Prosperity as in some parts of China where bats often adorn wedding cards. Actually, in Europe killing a bat can result in hefty fines – that’s a start.

© Dr V.B. Meyer-Rochow and, 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 with appropriate and specific direction to the original content. 

biology zoology blog benno meyer wrinkle

“Wrinkle-wrinkle, au revoir”

How I wonder what you are

I have recently been reading about wrinkles. Not because I am worried about my wrinkles (I actually think wrinkles can make a face look more interesting than if it was “as smooth as a baby’s bottom”), but because so many people here in East Asia seem terrified of getting wrinkles and avoid an exposure to direct sunlight through face masks, parasols, summer hats, lotions, creams, etc. The scientific literature on wrinkles includes information on skin structure and function, biochemical and physiological reasons to develop wrinkles, but I couldn’t find anything about perhaps the most obvious reason: you get older, you shrink!  As we age, our height diminishes. During the time I passed university examination I was 184 cm tall; now I am 181 cm tall. People who have spent some time in the space station circling around our planet Earth under zero gravity conditions reverse that trend and are a little bit taller when they return to Earth. An apple that ages shrinks and becomes wrinkly. And humans  – how about us?

Wrinkles consist of more or less deep furrows and bulges and they usually develop along locations of microlines in the skin. The latter form a polygonal network of fine lines easily visible on the outer skin layer (the epidermis) with a magnifying glass. Under the epidermis lie the dermis and hypodermis with their stabilizing connective tissue component proteins collagen for structural integrity and elastin for flexibility and plasticity. And, not to forget, there is hyaluronic acid in the skin with its multiple functions. All the skin layers are associated with underlying lymphatic vessels along with perilymphatic and subcutaneous fat tissue, known as panniculus adiposus and p. carnosus. What is most damaging and a cause of the skin to age is oxidative stress, in other words free oxygen radicals. These radicals are highly reactive and may be produced by the breakdown of double-bond fatty acids following an exposure to UV-radiation. There are, of course, ways the skin tries to protect itself: a higher sebaceous gland density of the skin is correlated with shallower wrinkles, but as the pillars of the skin (like collagen and hyaluronic acid) slowly diminish and the skin becomes drier the decline in skin cell renewal of older people can only be slowed down with a nutrition that is rich in vitamins and anti-oxidants.

What matters also are the genetic factors and how rapidly a person ages. In addition, smoking and heat are often mentioned as wrinkle-promoting, and so is lack of sleep; in fact, anything that causes skin to become dehydrated. However, there is one cause that is related to facial expressions.  Grooves on the forehead during thinking, or wrinkles during laughter, or the vertical lines between your eyes during squinting to see more clearly: such lines can become permanently visible as expressive wrinkles. There is generally not terribly much that an ageing person can do to avoid getting wrinkles, but there is one dog breed (the “Shar-pei”), in which the wrinkles disappear with age. For other and much bigger animals with wrinkled skins, the wrinkles can actually be an advantage as they can hold moisture that can then evaporate from a larger surface area and in this way lead to the cooling of the wrinkled individual. This suggestion has often been advanced to explain the folds and wrinkles of the skins of elephants and rhinoceroses. However, fact is that any animal (other than a Shar-pei dog) develops wrinkles as it ages, especially around the joints. But because animals are covered in fur we tend to overlook their wrinkles  -with one exception: the beautiful, pain-free naked mole rats. Their incredibly wrinkled bodies help these subterranean, naked rodents to turn around in their narrow tunnels and navigate corners with ease.

To return to my earlier statement that we shrink as we age and that space travellers are taller when returning to Earth: my hypothesis is that they would not only be slightly taller but also less wrinkled (provided they got enough sleep and had good vitamin-rich food while at the space station). In any case: Every wrinkle has a story to tell and as for me, there will be a lot more stories when I’m older.

© Dr V.B. Meyer-Rochow and, 2020.
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 with appropriate and specific direction to the original content. 

“Vermis in Vesica”

Studied by Rembert Dodoens in 1581

I stumbled across the works of this 16th century Flemish physician, because he shares his first name with that of my first son’s and because I myself looked at “vermis in vesica” (worms in bladders). However, there were three big differences between Dr Dodoens (who published his observations in  Latin under the name Rembertus Dodonaeus) and myself: I publish in English and not in Latin and my observations on worms dealt mostly with the urinary bladders of frogs and were carried out with the aid of a microscope, while Dr Dodaens had worked on human corpses and had no microscope for his studies (the microscope was invented years later by Antoni Van Leeuwenhoek in 1674).

I concentrated on frog urinary bladders and frog intestine, because these tissues are ideal structures for the students of the parasitology course I had to teach at Waikato University. Very frequently one can locate some flatworms, known as Digenea trematodes or flukes, in the urinary bladder. Some of these worms are so closely linked to their frog host species that the name Batrachotrematidae of the worm’s family already indicates the close relationship between host and parasite. Other types of flatworms, also present and visible without the help of a microscope because of their large size, are so-called polystomatid Monogenea. Adult tapeworms never reside in the bladder, but their larvae known as plerocercoids can occur in some muscle tissue outside the bladder. Specimens of the ubiquitous nematodes, simply called roundworms, are almost always noticeable in the gut but not the bladder. Because of their whitish coloration and small size it is best to use a microscope to identify them.

When it comes to a microscopic examination of the liquid bladder content the students are usually in for a surprise. If they happen to have a nice frog specimen, then its bladder could be like an “aquarium” for protozoans like flagellates with their undulating membrane or whip-like flagella. Ciliates and amoeba are larger, but the former are fast and the latter are slow. The urinary habitat is not an easy one to survive in. Nitrogenous wastes like urea have to be tolerated and frequent emptying represents a danger of being flushed out. Residing in blood or lymph vessels avoids that, but of course it poses other problems.

Rejection and attacks of the pathogen by antibodies is one problem, the flow of the blood is another, but it is also a boon for the parasite as it supplies nutrients and facilitates transport. The blood flukes Schistosoma mansoni, S. japonicum and 4 others reside in veins and produce eggs that pass out with the faeces, hatch into larvae that mature in a freshwater snail from which the infectious stage is released into the water to find a human host’s skin. Once in the human host, the larvae enter the blood system, mature in the liver and as adults lodge themselves in the blood vessels of the intestines. If that is not worse enough, another parasite, the nematode Wucheria bankcrofti seeks out lymph vessels to live in and then blocks the lymphatic system, causing ‘elephantiasis’. This can lead to grotesque deformations of limbs and other body parts. Varicose veins, so common in the legs of elderly people, however, have nothing to do with parasites in the blood or lymphatic system (although Dr Dodoens had different ideas), but are thought to be the result of a life on two legs. Incidentally, mammals using all four legs to support their bodies throughout their lives fail to develop varicose veins (not even the legs of an elephant have them).

However, animals do suffer from blood parasites (and in the case of seal pups there can even be larval Uncinaria lucasi hookworms in the seal mother’s milk), which takes us back to Dr Rembert Dodoens “Vermis in Vesica”:  worms in humans, yes; but worms in human breast milk, no!

© Dr V.B. Meyer-Rochow and, 2020.
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 with appropriate and specific direction to the original content.