COMPOSIÇÃO MINERAL ÓSSEA DAS NADADEIRAS PEITORAIS DA Sotalia guianensis, NO LITORAL DO ESPÍRITO SANTO

Sotalia guianensis is an odontoceti cetacean that is broadly distributed on Central and South American coasts, from Honduras to Brazil, and is currently categorized as “Near threatened” by the IUCN. Previous studies proved that the mineral content increases with bone maturation and decreases after reaching maturity. Therefore, this study evaluated the mineral composition of 33 specimens of S. guianensis and verified if this factor influences bone development. The ages of the animals were estimated by counting the annual growth layers on the teeth. Bone mineral content (BMC) analysis was performed by atomic emission spectrometer. To evaluate the correlation between BMC and the variables age and total length, the Spearman correlation test was carried out. The average Ca was 360.2μg g-1, the average P was 171μg g-1, and the average magnesium was 3.34μg g-1. The analysis of the bone mineral composition of the S. guianensis species showed a low statistical correlation with age and total length; however, a higher concentration of P was observed in immature individuals compared to the mature ones.Sotalia guianensis é um cetáceo odontoceto amplamente distribuído ao longo da costa da América Central e do Sul, desde Honduras até o Brasil, e está atualmente categorizada como “quase ameaçada” pela IUCN. Estudos anteriores demonstraram que o teor mineral aumenta com a maturação óssea e decresce após atingir a maturidade. Desta forma, este trabalho avaliou a composição mineral de 33 espécimes de S. guianensis e verificou se este fator influencia o desenvolvimento ósseo. As idades dos animais foram estimadas, a partir da contagem das camadas anuais de crescimento nos dentes. A análise do conteúdo mineral ósseo (CMO) dos úmeros foi realizada por espectrômetro de emissão atomizado. De modo a avaliar a correlação entre o CMO e as variáveis idade e comprimento total, foi realizado o teste de correlação de Spearman. O Ca médio foi de 360,2µg g − 1, P de 171µg g − 1 e Mg de 3,34µg g − 1. A análise da composição mineral óssea da espécie S. guianensis apresentou baixa correlação com a idade e comprimento total; entretanto, foi observada uma maior concentração de P em indivíduos imaturos, em comparação aos maduros

Population genetic structure of Guiana dolphin (<i>Sotalia guianensis</i>) from the southwestern Atlantic coast of Brazil

<div><p><i>Sotalia guianensis</i> is a small dolphin that is vulnerable to anthropogenic impacts. Along the Brazilian Atlantic coast, this species is threatened with extinction. A prioritized action plan for conservation strategies relies on increased knowledge of the population. The scarcity of studies about genetic diversity and assessments of population structure for this animal have precluded effective action in the region. Here, we assessed, for the first time, the genetic differentiation at 14 microsatellite loci in 90 <i>S</i>. <i>guianensis</i> specimens stranded on the southeastern Atlantic coast of the State of Espírito Santo, Brazil. We estimated population parameters and structure, measured the significance of global gametic disequilibrium and the intensity of non-random multiallelic interallelic associations and constructed a provisional synteny map using <i>Bos taurus</i>, the closest terrestrial mammal with a reference genome available. All microsatellite loci were polymorphic, with at least three and a maximum of ten alleles each. Allele frequencies ranged from 0.01 to 0.97. Observed heterozygosity ranged from 0.061 to 0.701. The mean inbreeding coefficient was 0.103. Three loci were in Hardy-Weinberg disequilibrium even when missing genotypes were inferred. Although 77 of the 91 possible two-locus associations were in global gametic equilibrium, we unveiled 13 statistically significant, sign-based, non-random multiallelic interallelic associations in 10 two-locus combinations with either coupling (<i>D</i>' values ranging from 0.782 to 0.353) or repulsion (<i>D</i>' values -0.517 to -1.000) forces. Most of the interallelic associations did not involve the major alleles. Thus, for either physically or non-physically linked loci, measuring the intensity of non-random interallelic associations is important for defining the evolutionary forces at equilibrium. We uncovered a small degree of genetic differentiation (F_ST = 0.010; <i>P</i>-value = 0.463) with a hierarchical clustering into one segment containing members from the southern and northern coastal regions. The data thus support the scenario of little genetic structure in the population of <i>S</i>. <i>guianensis</i> in this geographic area.</p></div

Population parameters and genetic diversity of microsatellite loci genotyped in <i>Sotalia guianensis</i>.

<p>Population parameters and genetic diversity of microsatellite loci genotyped in <i>Sotalia guianensis</i>.</p

Intensity and significance of sign-based gametic disequilibrium between two-locus combinations.

<p>Intensity and significance of sign-based gametic disequilibrium between two-locus combinations.</p

Thoracic limb bone development in Sotalia guianensis (Van Beneden 1864) along the coastline of Espírito Santo, Brazil

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

Provisional synteny map.

<p>For each <i>Bos taurus</i> chromosome, synteny segments for <i>Tursiops truncatus</i> are positionally indicated by colored bars. <i>Bos taurus</i> chromosomes are ordered by number. The U chromosome represents sequences that are unmapped to a particular chromosome.</p

Two-locus combinations that exhibited significant global gametic disequilibrium.

<p>Two-locus combinations that exhibited significant global gametic disequilibrium.</p

Collection localities of <i>Sotalia guianensis</i> along the coast of the State of Espírito Santo, Brazil.

<p>(A) State map of Brazil. The black rectangle indicates the State of Espírito Santo, highlighted in dark green. (B) Zoom in on image map area. (C) Range distribution of the sample localities (red dots). The dashed line represents the South and North State midline with the geographic coordinates set at 20°03'18.8"S 40°11'26.8"W.</p

Population parameters used to estimate the levels of mutability at the 14 microsatellite loci.

<p>Population parameters used to estimate the levels of mutability at the 14 microsatellite loci.</p