Morphological skin colour changes in teleosts

Abstract

Morphological skin colour change in fish is often referred to in the sole context of background adaptation. It is becoming increasingly apparent that it is a broad phenomenon elicited by a variety of factors. To date, no review has attempted to integrate the different types of morphological colour changes occurring in teleosts, their ecological origins and the regulatory mechanisms involved, often restricting the view on the subject. First, the origin of skin colour is addressed in teleosts including chromatophore type and distribution, pigment biosynthetic pathways and their interactions to one-another. Second, the different types of morphological colour changes occurring in teleosts are categorized and a key distinction is made between proximate and ultimate morphological colour changes. These are defined respectively as the change of phenotype during an established life-stage in response to environmental interactions and during the transition between two developmental-stages phenotypically pre-adapted to their ancestral ecosystems. Nutrition and UV-light are primary factors of proximate morphological colour changes beyond the control of the organism. By contrast, background light conditions and social interactions are secondary proximate factors acting through the control of the organism. Highly diversified among teleosts, ultimate morphological skin colour changes are presented in term of alterations in skin structure and pigment deposition during metamorphosis in different species. Finally, the physiological and endocrine mechanisms regulating both proximate and ultimate morphological colour changes are reviewed

Morphological differences in the skin of marble trout <i>Salmo marmoratus</i> and of brown trout <i>Salmo trutta</i>

“…The phenotypic differences between the species are inherited, and therefore the marble color pattern formation can be categorized as an ultimate morphological change as defined by Leclercq et al [3].…”

“…In earlier stages, the phenotypes tend to be very similar, composed of dark vertical spots on the flanks, known as parr marks [1,2]. Such variations in skin color pattern between species and life-stage are primarily dependent upon differences in the morphology, density and distribution of chromatophores in the skin defined as morphological color changes [3,4]. Morphological color changes have a fundamental and longlasting impact on external coloration, as opposed to quick and reversible physiological color changes.…”

“…Recently, Leclercq et al [3] proposed a distinction of morphological color changes into two types: ultimate and proximate. Ultimate morphological color changes are associated with the transition between two life stages such as larvae-juvenile and juvenile-adult.…”

“…In contrast, proximate morphological color changes refer to the morphological modulations of a given life-stage skin color in response to variations in different environmental factors (nutrition, solar-radiation, background adaptation) and social interactions. [3].…”

Anomalous coloration of a yellow tail damselfish Stegastes arcifrons (Actinopterygii: Pomacentridae) at Isla del Coco National Park, Costa Rica

“…Color patterns are important elements of inter-and intra-specific species interactions (e.g., predation, competition, sexual selection, life stage identification), learning and communication (Siebeck, Wallis, & Litherland, 2008;Leclercq, Taylor, & Migaud, 2010). Coloration patterns relate to the economic value of reef fish species used in the ornamental trade, with rare patterns increasing value (Leclercq et al, 2010).…”