And offers protection
Humans, perhaps because of the form of their own heads (or a distant memory of where their very first nourishment came from), have a particular relationship to round shapes. Big round eyes, bulging foreheads and puffy cheeks touch parental instincts and elicit exclaims such as “Gosh, how cute”. Images of angels, but also seal pups, polar bear cubs and, of course, human babies come to mind. Spheres may be beautiful from an aesthetic viewpoint, but they are also fascinating to mathematically interested people, as they represent perfect shapes whose characteristics like circumference and surface area can only be approximated on account of the open-ended decimals of the number π (pi).
Roundness, even if only partial as in the case of tortoises or horseshoe crabs, offers protection, reduces friction and increases strength. The sphere has the smallest exposed surface of any three-dimensional object and no other shape can cram as much volume into as small a body as a sphere. And that is precisely why eggs are roundish (for one might think that longish, sausage-shaped eggs would be easier to lay) and why many animals turn into something like a sphere in moments of danger, molestation or stress.
Hedgehogs assume the shape of a prickly ball and reduce their surface area at the slightest alarm; armadillos, although lacking spines but possessing dermal bone plates, do the same, while sea-urchins are naturally rotund as well as spiky. Certain millipedes, appropriately termed “pill millipedes”, and some woodlice of the genus Armadillidium, roll up into perfect little spheres, which children in some countries use as temporary marbles. It has even been suggested that it was Sumerian children playing with these living marbles thousands of years ago that gave our ancient ancestors the idea of building the first rotating object: the wheel.
Certain species of insects and spiders, too, are not bad at imitating a spherical blob and hamsters and other hibernating animals habitually curl up and, reducing their surface area in this way, become less vulnerable and exposed to both enemies and the elements. Roundness is also observed in some desert organisms such as the termite frogs in Africa and Australia, which with their seemingly blown-up bodies and tiny legs look like a weird caricature. The balloon principle is employed by the marine puffer fish as I found out many years ago, when I picked up two such fish from a tide pool in Djibouti (East Africa). These normally sleek fish can blow themselves up with either water or air and the two individuals that I had picked up did just that. Inflated like that and suddenly a lot bigger than before they would have become more than a mouthful and quite unmanageable for a predator, especially when, as in the case of my Djibouti specimens, they are further armoured with spines or prickles on their spherically distended bodies. I must admit, a little ashamed though, that it did not help the bigger of the two fish that I had collected, for it ended up as a dried, spherical trophy hanging from the ceiling in my study at home now.
© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2018.
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