Bird Colours and Feather Structure

**25**

**Chapter 2**

**Abstract**

natural pigments, plumage

**1. Introduction**

Haloarchaea May Contribute to

the Colour of Avian Plumage in

*Rosa María Martínez-Espinosa and Javier Torregrosa-Crespo*

Some seabirds or coastal birds such as flamingos or pelicans display elegant pink or reddish colours. These colours are due to pigments that birds cannot synthesize de novo. Thus, this coloration is mainly originated from carotenoids ingested trough carotenoid rich food sources like microalgae (*Dunaliella*) or small shrimps (*Artemia*), which are microorganisms inhabiting the salty environments where the mentioned birds live. New advances in this field of knowledge have revealed that extreme microorganisms belonging to the haloarchaea group (Archaea Domain) may contribute significantly to the characteristic pink- red colour of flamingos' feathers for instance. Alive haloarchaea cells have been found on the surface of the feathers. Besides, the major carotenoid produced by haloarchaea (bacterioruberin) has also been identify within the feathers structure. This work summarizes the main contributions recently reported about this topic as well as general aspects regarding bacterioruberin as a powerful colour carotenoid. Discussions about potential role of

these microorganisms in the life of seaside birds are also included.

**Keywords:** bacterioruberin, bird coloration, carotenoids, flamingos,

UV radiation for instance), and sexual dimorphism [3–6].

Coloration is one of the most conspicuous traits that varies among organisms. In the case of animals, colour is mainly due to: (i) the presence of pigments (carotenoids, melanin, turacoverdin, biliverdin, protoporphyrin, etc); (ii) light phenomena such as reflection/emission from animal structures (skin, feathers, etc.); (iii) the presence of microscopic structure in scales, bristles, or feathers, which give them brilliant iridescent colours (commonly named "structural colours") [1]; and (iv) general aspects related to genetics [2]. Due to these reasons, animals show different colours, which can slightly vary even between individuals belonging to the same species. Animal colorations are strongly linked to different biological roles: camouflage, sexual, social, and interspecific signalling, physical protection (against

In the case of the birds, feathers play a key role in general coloration. Those that are red orange show these colours thanks to the presence of different carotenoids within their structures. Carotenoids are natural pigments widely spread in nature: chloroplasts and chromoplasts of plants, bacteria, archaea, microalgae,

Marine Ecosystems
