Figure 1. The contrasting skin colours of the three studied species.

(A) Photograph showing, from top to bottom, a blue whale (pale grey skin colour, the lightest species), a sperm whale (dark grey skin colour) and a fin whale (black skin colour, the darkest species). This photograph was taken by DG. (B) Differences in density of melanocytes (thick bars) and melanin (thin bars) amongst the three studied species (n = 53, n = 17, n = 45 for blue, sperm and fin whales respectively). (C) Association between melanin abundance and melanocyte counts in whales. Grey dots correspond to blue whales, black dots to fin whales and crosses to sperm whales. The counting area was determined as previously described (see⁸). Briefly, the number of melanocytes per 100 arbitrary units was determined in triplicate along the entire epidermal ridge. The number of epidermal ridges to count was established a priori based on a cumulative curve⁸.