Legs awkwardly close together and stiff wings spread wide to maintain some balance. When it walks upright on land, the macaroni penguin waddles, a bit as if it has a thick elastic band around its legs. And that is not far from the truth, American veterinarians discovered. The bird appears to have a muscle in its abdomen on both sides that pulls the bones of its legs inwards.
Exactly how this works anatomically has been a subject of discussion for more than a hundred years, the Americans write in a scientific article that recently appeared in The Anatomical Record. They carefully examined the anatomy of two macaroni penguins that had been euthanized for veterinary reasons at the SeaWorld Zoo in San Diego. This, they say, has allowed them to clearly establish for the first time that penguins have a symmetrically paired muscle that connects the legs to the torso. They have the muscle adductor tibialis muscle named after its function.
In birds, and therefore also in penguins, the tibia (tibia) fused with a foot bone (tarsus) and thus forms the tibiotarsusa bone that is located between the thigh and the toe phalanges of the legs. The newly found skeletal muscle runs from the bottom of the sternum to the tibiotarsus. The muscle is unique to the penguin, as no other bird is known to be built like this.
Underwater, where macaroni penguins spend half their lives and must gather their food, the extra muscle gives a clear advantage. The legs can be pulled tightly against the abdomen, causing the animals to shoot through the water like a torpedo. And although it may seem uncomfortable on land, the adductor tibialis muscle also an advantage on land, the researchers write. This contributes to the reverse pendulum movement that helps penguins on land to save energy when walking.
The Americans made another discovery during the dissection of the two penguins: the supracoracoideus muscle is noticeably much thicker in macaroni penguins than in other birds. This muscle is responsible for the upright wing beat. In the air, the wing beat downwards is fed by the bird’s pectoral muscle elevator and propulsion; the upward stroke is only necessary to repeat the same movement. This is different under water: both the downward and upward stroke can give the animal effective propulsion. And that is reflected in the construction of macaroni penguins.
For those wondering what penguins have to do with macaroni, they were given that name by British explorers. It refers to young English men who traveled to Northern Italy in the eighteenth century and returned in flamboyant clothing, often with a striking feather on their hat. They were derisively called macaronis. The penguin with the striking orange plumage feathers on its head was very reminiscent of this.
