Albinism in the smooth butterfly ray Gymnura micrura (Elasmobranchii, Gymnuridae): first record and morphometric comparisons
Albinism is a hereditary abnormality characterized by a lack of the pigment melanin. In fishes, albinism has been recorded several times in teleosts, both less frequently in sharks and rays. This note reports a record of albinism in one smooth butterfly ray Gymnura micrura (Bloch & Schneider, 1801) caught by artisanal fishermen inside the continental shelf of Northeastern Brazil. No significant differences were observed between morphometric data of this specimen, which exhibited total albinism, and normally pigmented individuals of the same sex caught in the same area. Regression analyses of disc width and total length against weight of 28 individuals (including the albino) demonstrated that the albino was within the normal range of sample values. Moreover, an analysis of principal components (PCA) using morphometric data placed the albino within the same boundaries as normally pigmented individuals and confirmed that the albino was morphometrically similar to normal specimens. As observed in previous studies, we conclude that the albinism in Gymnura micrura has little or no influence on growth and morphometric characteristics.