Abstract
The estuarine dolphin, Sotalia guianensis, is one of the most abundant cetacean species in Brazil. Determination of age and of aspects associated with the development of this species is significant new studies. Counts of growth layer groups in dentin are used to estimate age of these animals, though other ways to evaluate development are also adopted, like the measurement of total length (TL). This study presents a procedure to evaluate the development of the estuarine dolphin based on the ossification pattern of forelimbs. Thirty-seven estuarine dolphins found in the state of Espírito Santo, Brazil, were examined. Age was estimated, TL was measured and ossification of epiphyses was examined by radiography. We analyzed results using the Spearman correlation. Inspection of radiographs allowed evaluation of the significance of the correlation between age and development of the proximal (r = 0.9109) and distal (r = 0.9092) radial epiphyses, and of the distal ulnar epiphyses (r = 0.9055). Radiographic analysis of forelimbs proved to be an appropriate method to evaluate physical maturity, and may be a helpful tool to estimate age of these animals in ecological and population studies.
Highlights
Sotalia guianensis, known as the estuarine dolphin, is one of the most abundant cetaceans in Brazil and is distributed along a large part of the South and Central American coasts [1, 2]
Ossification of Guiana Dolphin Forelimb area, though little is known about S. guianensis by The World Conservation Union [3] and the Brazilian government [4]
Sexual maturity is reached at the age of six years, while physical maturity occurs at seven years, when the animal reaches 185 cm in total length (TL) [7]
Summary
Known as the estuarine dolphin, is one of the most abundant cetaceans in Brazil and is distributed along a large part of the South and Central American coasts [1, 2]. This species is readily observed, and has been the focus of research in this geographic. The estuarine dolphin is a small cetacean of the Family Delphinidae [5] Maximum lifespan of this species is estimated at between 30 and 35 years, though exact longevity is unknown [6]. Carvalho et al [9] report that mean TL of individuals older than seven years of age found in this state is 187.5 cm
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