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.

Variations of age and total length of Sotalia guianensis from the state of Espírito Santo, Brazil, were evaluated. Specimens were found stranded. Age and total length of 44 Guiana dolphins were assessed based on tooth analysis. Age varied between 0.5 year and 33 years (mean = 8.23 years). Most specimens were between zero and 6 years old (47%). Total length varied from 119 cm to 198 cm, with mean of 172.52 cm. Asymptotic length was reached at 185 cm and approximately 5-6 years of age. Mean total length and age were higher than in other regions of the distribution range of the species. Nevertheless, more studies have to be carried out to evaluate the morphological variations in S. guianensis populations in the study area and Brazil.Keywords: Guiana dolphin, age, total length. Variação etária e de comprimento total de

The skeleton is often the only remaining structure of the Guiana dolphin, Sotalia guianensis, after decomposition of carcasses. This study investigates the bone development of Guiana dolphins beached on the coastline of the state of Espírito Santo, Brazil. External measurements of 43 thoracic limbs were obtained. Internal structures (radius, ulna, and humerus) were also measured. Dual-energy X-ray absorptiometry (DXA) was used to evaluate bone mass. The variables concerning the thoracic limb were tested using the Akaike information criterion to scale the best growth model when correlated with age and by the allometric model when they were correlated with total body length. The efficacy of DXA was also tested. The Brody growth model (best fit) showed that the thoracic limb stopped growing around the age of 2, while total body length ceased to grow at the age of 5.5. The thoracic limb presented early growth (negative allometry) compared with total body length. The methodology used to measure bone mass was efficient when considering ash weight. No difference in bone density was observed between the right and the left forelimb (P > 0.05), male and female (P > 0.05), or between dolphins found in the 3 sites we monitored. The deposition of bone mass was high in the early stages of life, and stabilization occurred at around the age of 13. O esqueleto muitas vezes é a estrutura que resta da espécie Sotalia guianensis, boto-cinza, devido ao processo de decomposição em que as carcaças são encontradas. O objetivo do presente estudo é entender o desenvolvimento ósseo dos animais encontrados encalhados no litoral do Espírito Santo. Para isso, 43 pares de nadadeiras peitorais foram submetidos às mensurações externas e de estruturas ósseas internas (rádio, ulna e úmero) e à técnica de absorciometria de raio-x de dupla energia (DEXA) para massa óssea. As variáveis das nadadeiras foram testadas pelo critério de Akaike para escalonamento do melhor modelo de crescimento quando correlacionadas com a idade, e para o modelo alométrico quando correlacionadas com o comprimento total (CT). Foi testada a eficácia da DEXA. através do modelo de crescimento de Brody (melhor ajuste) e pode-se observar que as nadadeiras param de crescer por volta dos 2 anos de idade e o comprimento total do corpo aos 5.5 anos, apresentando essas estruturas crescimento precoce (alometria negativa) em relação ao CT. A metodologia aplicada para mensuração da massa óssea mostrou-se eficaz quando correlacionada com peso das cinzas. Não houve diferença de densidade óssea entre nadadeira direita e esquerda (P > 0.05), macho e fêmea (P > 0.05) e nem entre os animais dos três diferentes locais de ocorrência, pois todos estavam dentro do mesmo intervalo de confiança. A deposição da massa óssea é acentuada no início da vida com posterior estabilização por volta dos13 anos de idade.

RESUMOEstudou-se o desenvolvimento do boto-cinza (Sotalia guianensis) do litoral do Espírito Santo e verificouse se a análise das radiografias da aleta peitoral pode ser utilizada para tal. Trinta e sete botos passaram pela determinação do comprimento total (CT), análise do grau de fusionamento das vértebras e radiografia das aletas peitorais. O CT ao nascimento foi de 103,3cm e o de animais maduros fisicamente 187,5cm. Observou-se correlação entre o CT, as epífises distais do rádio e da ulna e correlação entre o grau de fusionamento vertebral e a epífise distal do rádio. Concluiu-se que a análise radiográfica das aletas peitorais é uma boa maneira de avaliar o grau de maturação física do boto.Palavras chave: Sotalia guianenis, radiografia, maturação física ABSTRACT The aim of this study is to analyze the development of the estuarine dolphin from the coast of Espírito