December 7, 2021

I, Science

The science magazine of Imperial College

From the ingenious to the ridiculous: Hannah Wilson describes startling super biological adaptations

From the ingenious to the ridiculous, the direction evolution has taken in creating creatures great and small never fails to amaze. Here is a selection of six startling super adaptations, from high flying circulatory systems to self-applied sun cream.

bar headed goose Noel Reynolds

High flyers

Bar-headed geese breathe more deeply and efficiently under low oxygen conditions, which helps them fly at high altitude. Their hemoglobin has greater affinity for oxygen, which has been attributed to a single amino acid mutation that causes a conformational shift in the hemoglobin molecule. Also, the left ventricle of their hearts – responsible for pumping oxygenated blood to the body via systemic circulation – has significantly more capillaries in bar-headed geese than in lowland birds, maintaining oxygenation of cardiac muscle cells and therefore cardiac output. This enables the geese to sustain the huge metabolic demands of high altitude flight.

No laughing matter

The poor female spotted hyena has a vagina that is fused shut, resulting in a pseudo-scrotum. Intercourse, urination, and birth are all performed through the female’s massively enlarged clitoris. The strange organ matches the male’s penis in both size and hardness. Scientists are still struggling to understand why the female hyena has evolved this trait, especially given that one out of every ten births results in the death of the mother. The evolutionary benefit of this trait remains a complete mystery.

spotted hyena by Gwendolen Tee

Crème du soleil

Surviving in the sub-Saharan African sun is a challenge not many could achieve, but hippos have developed their own natural sunscreen. The substance oozes out of their pores in a shocking, bright red color. This strange secretion is aptly named “blood sweat,” although it contains neither of those two bodily fluids. Instead, it is made up of a number of highly acidic compounds that absorb ultraviolet light, preventing sunburn and also inhibiting the growth of bacteria.

Bang, bang you’re dead

Pistol shrimps have one disproportionately large claw with two interlocking parts in the place of pincers. When it pulls the limb structure back and releases, the built up pressure creates a wave of bubbles that contain energy with as much heat as the surface of the sun. These ‘bullets’ from the John Waynes of the sea create shock waves that knock out potential predators. They can also shoot-from-the-claw to stun prey for the shrimp to eat.

pistol shrimp by Vishal Bhave
western painted turtle

Icy gamble

Several species of frogs and turtles (including the western painted turtle) have evolved to freeze solid during the winter and then thaw back to life in the spring. This outstanding way of surviving cold spells is explained by the fact that the urea and glucose in their blood reduces the osmotic shrinkage of cells caused by the cold conditions, which would otherwise lead to their death. There is, however, a limit to their resistance: although they appear rock solid when frozen, the survival of these animals is compromised if more than 65% of the water in their bodies freezes.

Touch sensitive

The pantropical weed Mimosa pudica, which grows mostly in shady areas under trees or shrubs, has leaves that fold up when touched. The mechanism for the adaptation involves specific regions on the stem that are stimulated to release potassium ions. These force water to diffuse out of the cell leading to a loss of cell pressure and cell collapse. The differential turgidity between different regions of cells results in the closing of the leaflets and collapse of the leaf petiole. The mechanism is thought to act as a defense against herbivores that may otherwise feed on the plant.

mimosa pudica 1024w

Images: Bar-headed Goose (Anser indicus) by Noel Reynolds;  Tiniest Tail by Gwendolen Tee; Hippo close-up (Wikimedia); Pistol shrimp (Front) by Vishal Bhave; Western Painted Turtle (Chrysemys picta bellii)) by John ClareMimosa pudica by Roberto Verzo