"Ino" colour aberration in gentoo penguin (Pygoscelis papua) in Antarctica

MARIANA A. JUARES; JAVIER NEGRETE; JORGE A. MENNUCCI; LUCRECIA LONGARZO; NÉSTOR R. CORIA

Notornis

Ornithological Society of New Zealand, Nelson, Nueva Zelandia

Año: 2011 vol. 58 p. 169 - 172

0029-4470

Two main types of pigments, carotenoids and melanin, determine plumage colouration. Carotenoids are obtained from food, while melanin formation involves chemical reactions and is genetically determined. Melanin pigments comprise pheomelanin (red/brown) and eumelanin (brown/black). Any change in the formation processes of these types of pigments may lead to abnormal colouration of an individual (van Grouw 2006). For instance, a strong qualitative reduction of both types of melanin defines a colour mutation called Ino. In this case phaeomelanin almost disappears and there is a poor oxidation of eumelanin. As a result black feathers turn very pale brown although remaining highly visible the natural colour pattern of the species. However sun exposure can bleach the plumage to a nearly white colour. Additionally, Ino individuals present reddish eyes but with better eyesight, and higher probability of reaching adult age, than albino individuals. According to van Grouw (2006), any adult white bird with red eyes in nature is an ino, not an albino. On 15 December 2003 an Ino chick Gentoo penguin Pygoscelis papua was observed at Stranger Point, 25 de Mayo/King George Island. The following year, on 5 December 2004 an Ino prebreeder Gentoo penguin was seen at the same locality. During 2006/07 breeding season an Ino adult of the same species successfully reared two normally coloured chicks. In the subsequent two seasons (2007/08 and 2008/09) an Ino adult was recorded nesting at the same breeding group, but reproductive performance in these seasons was not established. Due to the philopatry of Pygocelid penguins (Williams 1995) and the low occurrence of the colour aberrations in natural populations (Hosner and Lebbin 2006) we suppose that all cases reported here corresponds to different life stages of the same individual. The reported Ino penguin shows pale brown colour in the coloured areas of the plumage in this species. It presents reddish eyes and grey claws. The beak remains orange but its dark part (culmen) is grey. In summary the Ino penguin shows a clear reduction of the darkest areas of the body changing from black to pale brown in plumage and from black to grey in other tissues such as beak and claws. Nevertheless the distinct colour pattern of this species is still recognizable. Colour aberrations are sometimes related to a low survival due to increasing risk of predation or decreasing foraging success. Moreover colour aberrations are thought to affect breeding success by increasing intraspecific conflicts mainly during courtship stage (see Holt et al. 1995; Alaja and Mikkola 1997). Nevertheless the Ino individual reported here bred successfully, like other Pygocelid penguins with colour aberrations (Stirling 1969; Valencia et al. 1997; Forrest and Naveen 2000; Nishikawa et al. 2000). To our knowledge this is the first report of an Ino Gentoo penguin, following van Grouws (2006) classification. A brief review of the literature regarding colour aberrations in penguins shows great diversity of terms and classification adopted, thus is possible that this type of colour aberration in Gentoo penguins was already reported for other localities under other names. We consider that a complete description of the colour of plumage, skin, eyes, beak and other part of the body would allow comparison between species and/or individuals of different localities beyond the classification adopted.