To resort to the comparison with distinctive characters of different species of animals to define our congeners is something very human. Sometimes we do it on grounds, sometimes based on legends and hearsay. The virtues and defects of the neighbor have been illustrated with wide and varied references to the animal world.
As we are little to praise, the memory of the elephant or the sight of the eagle are moderately used resources. On the contrary, the statistics of our linguistic uses overflow in paragons when it comes to highlighting the defects of others. During childhood, when we have not yet tamed the insulter that we carry inside, we fill the classrooms with moles, frogs or elephants according to the unfortunate companion who stands out for the excessive development of his teeth, eyes or ears, respectively.
However, the king of insults is the ‘seal’ (very frequently maintained and enhanced in the adult state). The poor diet and sedentary lifestyle of recent generations have led to this term being used more than one might expect by chance. But if malicious languages knew of the evolutionary success of a seal’s biological design, perhaps they would not use it as cheerfully as a throwing (verbal) weapon.
The morphology of a seal is an absolute triumph for life in polar environments since three attributes coincide in their biological architecture that, although they may seem the same, they are not. The seals are fat, the seals are big and the seals are round: they have all the ballots to eat the world, when it comes to a frozen world.
Why are seals fat?
Few animal groups have the physiological capacity to maintain a constant temperature. This mechanism, called endothermy, enables the optimal performance of most biological functions, regardless of the thermal records of the environment where it is inhabited.
Endothermy is achieved by matching active and passive mechanisms in the same body design.
In an active way, the uncoupled oxidative metabolism of the respiratory chain of oxidative phosphorylation within the mitochondria of brown adipose tissue (the brown fat) generates heat (rather than chemical energy or ATP). This internal brazier effect is compounded by the fact that brown fat adipocytes are very rich in mitochondria, which increases the burning rate of fats and sugars. Thus, the more brown fat you have, the more calories you can generate from the catabolism of the food you eat. And it is easier to keep the animal warm.
In a passive way, endothermic vertebrates resort in cold areas to something very similar to what we do when we take home frozen in a cork box. Namely: they surround the area that has to remain at a constant temperature with the best thermal insulator in the biological world, adipose tissue. The larger the fat pad (that is, the fatter the michelin), the more isolated the underlying musculature and viscera will be. And more will bring the animal cool (and pun intended) the cold outside.
Fat, on the other hand, is the biological reservoir of energy for mammals (among other animal taxa). The resulting energy surplus between what we eat and what we burn is saved for when needed in adipose tissue. This becomes a pantry that no one can steal from us because we carry it within our own anatomy.
The more fat, then, the more heat energy that can be generated, the more the generated heat can be retained and the more reserve fuel will be available in times of food shortage.
That’s why the seals are fat.
Why are the seals round?
According to the Zero Principle of Thermodynamics, if two objects contact at different temperatures, both will exchange heat until they equalize temperatures. Although the seal uses strategies (active and passive) to insulate itself thermally, the passage of heat to the outside is inevitable and continuous. This heat loss, which is so expensive for the seal, is carried out through its contact surface with the environment.
Therefore, the more surface area the animal has, the more easily it will cool down. What rent more, then? Well, having a shape that encloses a lot of volume (and, therefore, a lot of thermogenic and cold-insulating mass) in a minimal area (since it is on the surface where heat dissipates). And what is that perfect geometric figure that contains a maximum of volume with a minimum of surface area and that, therefore, is omnipresent in the physical world? Well, the sphere.
For this reason, seals tend to distribute their fat in a ball-like appearance.
Why are seals big
The combination of success therefore lies in enclosing the maximum amount of fat in a volume that offers a minimum surface contact with the outside. That is, in being spherical. If we transfer these key concepts of volume and surface to the mathematical formulas that define this geometric body we see that:
Volume = 4 / 3πr³
Surface = 4πr²
That is, in a sphere that grows in size (that is, its radius r increases), while its surface (where it loses heat) grows squared, its volume (with which it generates heat and isolates itself from the cold) makes the cube. In other words, it pays to be big instead of small because the surface / volume ratio is reduced. That is why the seal is not the size of a mouse but is a piece of seal.
Well, you know why seals are like seals. Although I am sure that my readers are not the type to insult but to those who know that adipose tissue has another not inconsiderable quality: tenderness.
A. Victoria de Andrés Fernández, Associate Professor in the Department of Animal Biology, University of Malaga
This article was originally published on The Conversation. Read the original.
