Black chickens exist, but the reality involves more than simply black feathers. Certain breeds exhibit a rare genetic trait causing an extreme accumulation of dark pigment throughout their entire bodies. This coloration extends beyond the exterior, making these birds entirely black, not just in their plumage, but in their internal tissues as well. This phenomenon has captivated breeders and scientists alike.
The Ayam Cemani: The Purest Black Chicken
The most striking example of this deeply pigmented fowl is the Ayam Cemani, a rare breed originating from Java, Indonesia. “Ayam” means chicken in Indonesian, and “Cemani” is a Javanese word meaning “thoroughly black.” This breed has been revered for centuries, often playing a role in religious and mystical ceremonies. Historically, the Ayam Cemani was associated with the Javanese elite and royalty. They are regarded as the most intensely pigmented chicken in the world, making them highly sought after globally. Breeders must carefully select for the purest black traits to maintain the standard.
The Biological Mechanism of Hyperpigmentation
The intense black coloration is caused by fibromelanosis, a genetic condition involving a complex rearrangement on chicken chromosome 20. The mutation leads to the duplication of a gene called endothelin 3, or EDN3.
In a normally pigmented chicken, EDN3 controls the development and migration of pigment cells, called melanoblasts. However, in chickens with fibromelanosis, the duplicated EDN3 gene is drastically overexpressed, with expression levels up to ten times higher than in normal chickens. This overexpression causes an abnormal mis-migration of the melanin-producing cells into connective tissues throughout the bird’s body.
This migration results in an excessive accumulation of the dark pigment melanin in the dermis and connective tissue formations. All fibromelanotic breeds, including the Silkie and the Swedish Svarthöna, possess the same unique genetic mutation, suggesting it arose spontaneously in a single ancestral bird. This genetic change is dominant, meaning the trait can be passed on easily, though the degree of pigmentation can vary depending on modifying genes.
Visual Appearance and Internal Characteristics
The result of fibromelanosis is a bird that is uniformly black across nearly all its anatomy. Externally, the feathers, beak, legs, feet, comb, wattles, and tongue are a deep, iridescent black. The pigmentation extends into the bird’s musculature and skeletal system, meaning the meat and the bones are also jet-black. The internal organs, including the heart and viscera, also exhibit hyperpigmentation. Despite the pervasive dark pigment, the chicken’s blood and eggs remain normal in color, with the eggs typically being a cream or tinted hue.