Ossification Pattern of Estuarine Dolphin (Sotalia guianensis) Forelimbs, from the Coast of the State of Espírito Santo, Brazil

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.

Variation of age and total length in Sotalia guianensis (Van Bénéden, 1864) (Cetacea, Delphinidae), on the coast of Espírito Santo state, Brazil

“…Age estimates of cetaceans stand is a good tool to characterize populations and to understand the biology of individuals (Pinedo and Hohn, 2000;Butti et al, 2007;Azevedo et al, 2015;Carvalho et al, 2015). In this sense, the ability to estimate the age of small cetaceans is extremely important in natural history studies (Hohn et al, 1989).…”

Review and experimental evaluation of the embryonic development and evolutionary history of flipper development and hyperphalangy in dolphins (Cetacea: Mammalia)

“…Although scientists have speculated about the cellular processes driving the development of hyperphalangy within cetaceans for over 120 years (Fedak & Hall, ; Howell, ; Kükenthal, ; Richardson & Oelschläger, ), a lack of fresh embryonic tissues created a major obstacle in experimentally testing molecular hypotheses (Fedak & Hall, ). Nevertheless, considerable advances were made by documenting patterns of phalangeal ossification (Benke, ; Calzada & Aguilar, ; de Carvalho et al, ; Fedak & Hall, ; Gihr et al, ; Mellor, Cooper, Torre, & Brownell, ; Ortega‐Ortiz, Villa‐Ramirez, & Gersenowies, ; Richardson & Oelschläger, ; Sterba, Klima, & Schlidger, ). Morphology‐based hypotheses were then augmented by a mechanistic understanding of limb development, leading to detailed hypotheses of the developmental prerequisites for hyperphalangy (Fedak & Hall, ).…”

Radiographic assessment of pectoral flipper bone maturation in bottlenose dolphins (Tursiops truncatus), as a novel technique to accurately estimate chronological age

“…In the majority of cetaceans previously studied, there is an established sequence of ossification progression pattern from proximal to distal including the radius, ulna, carpal, metacarpal and phalangeal bones. This pattern is remarkably constant, symmetrical and the same for both sexes [25, 37–39]. Physiological delayed perichondral ossification of the phalangeal diaphysis demonstrates shape changes in the proximal diaphysis, progressing from ovoid, to deltoid (triangular) and then dumbbell / rectangular [38].…”