In addition, the same genetic mutations can underlie different phenotypic expressions of syndactyly. In humans, syndactyly can arise from as many as nine unique subtypes with their own clinical, morphological, and genetic fingerprints. Reductions in the BMP-induced apoptosis likely allowed this trait to arise. Different vertebrate species with webbed feet have different mutations that disrupt this process, indicating that the structure arose independently in these lineages.Д«ats have also developed interdigital webbing for flight. Apoptosis, or programmed cell death, in development is mediated by a variety of pathways, and normally causes the creation of digits by death of tissue separating the digits. Webbed feet are the result of mutations in genes that normally cause interdigital tissue between the toes to apoptose. This is in contrast to a more hydrofoil-like flipper of many permanently aquatic animals. The roughly triangular design of webbed feet, with a broad distal end, is specialized to increase propulsive efп¬Ѓciency by affecting a larger mass of water over generating increased lift. Paddles generate less lift than hydrofoils, and paddling is associated with drag-based control surfaces. Aquatic control surfaces of non-piscine vertebrates may be paddles or hydrofoils. Webbed feet are a compromise between aquatic and terrestrial locomotion. This shape allows for the production of large forces during swimming through both drag-based and lift-based propulsion. This delta wing shape is a solution that has convergently evolved in many taxa, and is also used in aircraft to allow for high lift forces at high attack angles. However, one of the most common is the delta (О”) or triangular shape seen in most waterfowl and frogs. Webbed feet take on a variety of different shapes in birds, the webbing can even be discontinuous, as seen in lobate-footed birds like grebes. In birds, the legs utilize countercurrent heat exchange so that blood reaching the feet is already cooled by blood returning to the heart to minimize this effect.

One of the consequences of this modification in some species, specifically birds, is that the feet are a major location for heat loss. This modification significantly increases the surface area of the feet. The webbing can consist of membrane, skin, or other connective tissue and varies widely in different taxa. Several distinct conditions can give rise to webbed feet, including interdigital webbing and syndactyly. Here, the foot has a delta (triangular) shape that allows for the formation of leading edge vortices and likely increases swimming efficiency.ДЄ webbed foot has connecting tissue between the toes of the foot. The webbed foot of Rana temporaria, the common frog.

Webbed toes