Melanocyte counts are reduced in grey-morph relative to wild-type SRW skin.

<p>Bars represent the absolute number of melanocytes counted in grey-morph and wild-type whales. Darkly shaded bars represent the number of melanocytes in each of 5 high-powered fields and lightly shaded blue bars represent the number of melanocytes along each 0.25 mm of the basement membrane measured. Data were compared for both measurement methods using T-tests. Both tests yielded p-values smaller than 1x10^-5.</p

Wildtype, grey-morph and partial grey-morph phenotypes of southern right whales.

<p><i>Wild-type</i> adults (panel a) have black skin and often have white skin patches on their bellies. <i>Grey morphs</i> (calf in panel b) are primarily white at birth with splatterings of rounded black spots that extend dorso-laterally around their bodies (calf in panel b). Their white skin becomes light grey or brown with age (panel c). <i>Partial grey morphs</i> are primarily black with splatterings of white skin at birth (calf in panel d) which also darkens with age (adults in panels b and d).. (Photos: J. Atkinson, Ocean Alliance).</p

Light microscopy reveals reduced pigmentation and a decreased number of melanocytes in the affected skin of grey-morph SRWs.

<p>A comparison of Fontana Masson melanin staining is shown in wild type (Panels A, C, and E) versus grey-morph SRWs (Panels B, D, and F) at low-power (20X, Panels A and B), high-power (400X, Panels C and D), and extra high-power (600X, Panels E and F) magnification. Low-power magnification shows less melanin staining, particularly in the melanocytes distributed along the basal layer of the epidermal rete ridges (arrowheads, Panels A and B). Rete ridges and dermal papillae appear similar in grey-morph and wild-type whales. Dermal papillae are marked with “= >” in panels A, B and C. High-power magnification shows reduced melanin content and fewer positively-stained cells in the grey-morph skin (Panels C and D). Extra high-power magnification shows typical melanocyte dendrite morphology (arrowhead, Panels E and F) and normal melanosome transfer and capping of keratinocyte nuclei (asterisks, Panels E and F).</p

Identities and characteristics of sampled whales.

<p>Identities and characteristics of sampled whales.</p