© SFI Ichthyological notes – Notes ichtyologiques Albinism in the smooth butterly ray Gymnura micrura (Elasmobranchii, Gymnuridae): irst record and morphometric comparisons Received: 29 Aug. 2011 Accepted: 23 Mar. 2012 Editor: R. Causse by Marcelo REIS*, Henrique GRANDE, Morgana Maria MACEDO & Vandick da Silva BATiSTA (1) Résumé. - Un cas d’albinisme chez la raie-papillon glabre Gymnura micrura (Elasmobranchii, Gymnuridae). L’albinisme est une anomalie héréditaire caractérisée par l’absence d’un pigment, la mélanine. Des cas d’albinisme ont été rapportés fréquemment chez les téléostéens, mais moins souvent chez les requins et les raies. Cette note présente un cas d’albinisme chez une raie-papillon glabre Gymnura micrura (Bloch & Schneider, 1801), femelle capturée par des pêcheurs artisanaux sur le plateau continental du nord-est du Brésil. Aucune différence signiicative n’a été observée entre les données morphométriques de ce spécimen, qui présentait un albinisme total, et des individus normalement pigmentés du même sexe capturés dans la même zone. Les régressions de la largeur du disque et la longueur totale contre les largeurs du disque et le poids de 28 individus femelles (en plus de l’albinos) ont démontré que l’albinos était dans la fourchette normale des valeurs de l’échantillon. Par ailleurs, une analyse en composantes principales (PCA), utilisant les données morphométriques, a placé l’albinos dans les mêmes limites que les individus normalement pigmentés et a démontré que l’albinos était semblable morphométriquement aux échantillons normaux. Comme cela a été observé dans des études antérieures, nous concluons que l’albinisme chez Gymnura micrura a une inluence mineure sur sa croissance et son histoire de vie. Key words. - Elasmobranchii - Rajiformes - Gymnuridae - Gymnura micrura - Northeastern Brazil - Pigment abnormality - Rays. 1992). The colour pattern for normal specimens is a grey, brown, light green or purple dorsal surface with round spots, and a white ventral surface (Bigelow and Schroeder, 1953). Ecologically, this species prefers the neritic waters of the continental shelf and is usually found on soft bottoms. The species can also be found on brackish estuaries or hyper-saline lagoons (Cervigón et al., 1992). Here, we report the irst record of albinism in the smooth butterly ray, and present detailed morphometric comparisons of the albino exemplar with normal specimens caught in the same area. We test, with such comparisons the hypothesis that the albinism has no negative inluence above morphometrics relations and characteristics. The albino specimen of G. micrura was caught on 8 August 2010 by artisanal fishermen on the continental shelf of Alagoas State (9º40’S, 35º40’W) at 22 m depth, in a ishing site known as São Miguel mud. As the name suggests, this site has a soft bottom of silt and is located in the delta of São Miguel River, 8.4 km from the coast. The specimen was caught using shrimp trawling nets (40 mm mesh in the body and 20 mm mesh in the bag). In the laboratory, the specimen was identiied, photographed, measured, and ixed in 10% formalin. The morphometric data were acquired according to the guidelines of Compagno (1984). After processing, the specimen was deposited under registration MUFAL-1448 in the Museum of Natural History of the Federal University of Alagoas, Northeastern Brazil. In order to eliminate the effects of sexual dimorphism and regional phenotypic variation, morphometric comparisons were made between the albino and apparently ‘normal’ specimens of the same sex caught in the same area. We used the data from 28 normal female plus the albino. Regression and variance analyses (one-way ANOVA) were used to comparison between the albino and normal specimens. Principal component analysis (PCA) was applied using Albinism is a hereditary lack of pigmentation caused by an enzyme deiciency involving the metabolism of melanin. The type of albinism can be characterized in terms of whether the lack of pigmentation is restricted to part of the body or the entire body (Boncinelli, 1998). The proximate cause of albinism is generally attributed to lack of activity of the enzyme tyrosinase, a key component of the pathway leading to the formation of melanin (Bechtel, 1991). Total or partial albinism has been previously reported for several species of sharks and rays (Clark, 2002; Bottaro et al., 2005; Sandoval-Castillo et al., 2006). The smooth butterly ray Gymnura micrura (Bloch & Schneider, 1801) is a Rajiformes that is physically characterized by a broad, rhomboid-shaped body with a short tail lacking a dorsal spine. The snout is obtuse and angular, with front edges of the disk concave. The tail has low dorsal and ventral infolds and 3-4 dark crossbars (Cervigón et al., Figure 1. - Albino (left) and normal (right) specimens of Gymnura micrura. (1) LAEPP/LABMAR/UFAL, Rua Aristeu de Andrade 452 Farol, Maceió, Alagoas, Brasil CEP. 57021-090. [henriquegrande@ymail.com] [morgana_bio@ibest.com.br] [tchoni@uol.com.br] * Corresponding author [marcelo_reiz@hotmail.com] Cybium 2013, 37(3): 217-219. Albinism in Gymnura micrura Reis et al. Figure 2. - Regressions of log of disc width vs. log of weight (A) and log of total length vs. log of weight (B) using the albino specimen and data from 28 female individuals of G. micrura. The albino specimen is represented by the white dot. Figure 3. - Principal component analysis (PCA) of morphometric data. The ellipse highlights the group formed by the albino and normally pigmented specimens of the same size class. The albino is represented by the white square. Squares (N3 = 20-30 cm size-class); inverse triangles (N4 = 30-40 cm), circles (N5 = 40-50 cm), lozenges (N6 = 50-60 cm), and triangles (N7 = 60-70 cm). following variables: disc width, total length, pre-oral length and mouth width, with the objective to verify if the albino fell within the typical morphometric boundaries of the species. In this analysis the specimens were grouped into six size classes according to disc width (10-20 cm; 21-30 cm; 31-40 cm, 41-50 cm, 51-60 cm; 61-70 cm). The albino specimen was a juvenile female measuring 252 mm in disc width, 175 mm in total length, and 120.32 g total weight. It lacked pigmentation in the entire integument and retina compared with normal specimens (Fig. 1). Such a combination indicates that the specimen may be considered a case of complete albinism. Regression analyses of disc width and total length against weight of 28 individuals (plus the albino) demonstrated a highly signiicant relationship (p < 0.001). These results demonstrated that the albino was within the normal range of sample values (Fig. 2). Univariate analysis made using the disc width, total length and weight, also indicated that there are no signiicant morphometric differences (p0.05 = 0.71) between the albino and the normally pigmented specimens. The PCA model explained 99.91% of the data variability. Factor 1 explained 99.77% of explained variation and mainly represents disc width, total length and weight. When the PCA data is plotted, it reveals the existence of morphometric groups that relate to individuals within the same size class. The albino was within the group formed by the individuals of the same size-class (21-30 cm), demonstrating that it possessed the same morphometric characteristics as normally pigmented individuals (Fig. 3). To our knowledge, the literature contains no record of albinism for Gymnuridae. There are, however, cases of albinism recorded in four species of Rajidae, two species of Dasyatidae, and one species 218 of Rhinopteridae, Myliobatidae, Mobulidae, Torpedinidae, Narcinidae (Sandoval-Castillo et al., 2006) and Rhinobatidae (Ben Souissi et al., 2007). The number of albinism reports in elasmobranchs is lower than in teleosts. One possible reason for the lower frequency of observations of this unusual phenotype in elasmobranchs is a lower relative abundance of cartilaginous ish in nature (Bonil, 1994) and a lower relative frequency of cartilaginous ish captured in commercial catch as compared to teleosts. Although the precise age of the specimen was not determined by growth marks in the calciied structures, the size-weight relationship did not reveal morphometric differences between the albino and normal specimens. Moreover, the literature already shows that albino elasmobranchs of considerable size have been captured (Clark, 2002). This fact may suggest that albino individuals may eat and grow just like normal individuals. It is possible that albinism may be disadvantageous by making these phenotypically distinct individuals more conspicuous to predators. By contrast, it seems that albinism may have low inluence in feeding, growth and another aspects of life, such reproduction (Joseph, 1961). Our results, in agreement with previous studies (Sandoval-Castillo et al., 2006) allows us to make the assumption that, despite being an albino phenotype that makes an individual more visible to predators, it can exert little inluence on aspects of growth and performance of these specimens. Acknowledgements. - The authors would like to thank CAPES, CNPQ and the Fundação de Amparo à Pesquisa de Alagoas – FAPEAL for inancial support, our team in the Laboratório de Ecologia, Peixes e Pesca for the help with the ield and laboratory work, Dr. Richard Ladle and Dr. Ana Malhado for the revisions, and Dr. Nídia Fabré for constant guidance. Cybium 2013, 37(3) Albinism in Gymnura micrura Reis et al. RefeRences BECHTEL H.B., 1991. - inherited color defects. Comparison between humans and snakes. Int. J. Dermatol., 30: 243-246. 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