Cellular and ultrastructural characterization of the grey-morph phenotype in southern right whales (Eubalaena australis).
Southern right whales (SRWs, Eubalena australis) are polymorphic for an X-linked pigmentation pattern known as grey morphism. Most SRWs have completely black skin with white patches on their bellies and occasionally on their backs; these patches remain white as the whale ages. Grey morphs (previously referred to as partial albinos) appear mostly white at birth, with a splattering of rounded black marks; but as the whales age, the white skin gradually changes to a brownish grey color. The cellular and developmental bases of grey morphism are not understood. Here we describe cellular and ultrastructural features of grey-morph skin in relation to that of normal, wild-type skin. Melanocytes were identified histologically and counted, and melanosomes were measured using transmission electron microscopy. Grey-morph skin had fewer melanocytes when compared to wild-type skin, suggesting reduced melanocyte survival, migration, or proliferation in these whales. Grey-morph melanocytes had smaller melanosomes relative to wild-type skin, normal transport of melanosomes to surrounding keratinocytes, and normal localization of melanin granules above the keratinocyte nuclei. These findings indicate that SRW grey-morph pigmentation patterns are caused by reduced numbers of melanocytes in the skin, as well as by reduced amounts of melanin production and/or reduced sizes of mature melanosomes. Grey morphism is distinct from piebaldism and albinism found in other species, which are genetic pigmentation conditions resulting from the local absence of melanocytes, or the inability to synthesize melanin, respectively.
Huntsman Cancer Institute, Salt Lake City, Utah, United States of America.|University of Georgia, Athens, Georgia, United States of America.
Guy D
GD
Eroh
Department of Pathology, University of Utah, Salt Lake City, Utah, United States of America.
Fred C
FC
Clayton
Department of Dermatology, University of Utah, Salt Lake City, Utah, United States of America.
Scott R
SR
Florell
Huntsman Cancer Institute, Salt Lake City, Utah, United States of America.|Department of Dermatology, Oregon Health & Science University, Portland, Oregon, United States of America.
Pamela B
PB
Cassidy
Programa de Monitoreo Sanitario Ballena Franca Austral, Puerto Madryn, Chubut, Argentina.
Andrea
A
Chirife
Department of Biology, University of Utah, Salt Lake City, Utah, United States of America.|Instituto de Conservación de Ballenas, Buenos Aires, Argentina.
Carina F
CF
Marón
Department of Biology, University of Utah, Salt Lake City, Utah, United States of America.|Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Ciencias Sociales, Universidad Nacional del Centro de la Provincia de Buenos Aires, Buenos Aires, Argentina.
Luciano O
LO
Valenzuela
Department of Pediatrics, University of Utah, Salt Lake City, Utah, United States of America.|Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, United States of America.
Michael S
MS
Campbell
Department of Biology, University of Utah, Salt Lake City, Utah, United States of America.
Jon
J
Seger
Programa de Monitoreo Sanitario Ballena Franca Austral, Puerto Madryn, Chubut, Argentina.|Department of Biology, University of Utah, Salt Lake City, Utah, United States of America.|Instituto de Conservación de Ballenas, Buenos Aires, Argentina.|Ocean Alliance/Whale Conservation Institute, Gloucester, Massachusetts, United States of America.
Victoria J
VJ
Rowntree
Huntsman Cancer Institute, Salt Lake City, Utah, United States of America.|Department of Dermatology, Oregon Health & Science University, Portland, Oregon, United States of America.
Sancy A
SA
Leachman
D000818:Animals; D002452:Cell Count; D005260:Female; D008297:Male; D008544:Melanocytes / Q000166:cytology; D010641:Phenotype; D012867:Skin / Q000166:cytology / Q000648:ultrastructure; D014907:Whales / Q000033:anatomy & histology*