A CAMADA DE GORDURA DAS TONINHAS, PONTOPORIA BLAINVILLEI (MAMMALIA, CETACEA) NO LITORAL SUL DO RS: VARIAÇÃO NA ESPESSURA E NA COMPOSIÇÃO DE ÁCIDOS GRAXOS EM RESPOSTA A FATORES AMBIENTAIS E FISIOLÓGICOS.
In order to investigate the usefullness of blubber thickness to estimate the body fat condition in Pontoporia blainvillei, axillary girth measurements were taken from dorsal, ventral and lateral regions, between the pectoral flipper and the dorsal fin. Blubber measurements were obtained for 116 franciscana dolphins, accidentally caught by the coastal artisanal fishery from Rio Grande (32º 05? S e 52º 08? W), between 1999 e 2003. Sexual maturity was determined from macroscopic and histological analysis of gonads. Dorsal blubber thickness (DBT) had the highest variation among the 3 measurements taken, and was considered the best measurement assess body fat condition in this species. DBT was lowest for pups and highest for mature females. Immature and mature males did not differ in DBT measurements. Dorsal blubber thickness also exhibited inter-annual variation such that 2002 individuals had thicker layers and thus better body condition that those accidentally caught in 2000 and 2001. Ventral blubber thickness (VBT) did not vary as much as DBT but seemed to be affected by seasonality. VBT was lowest in the fall and highest in the winter. Inter-annual variation in blubber thickness may be the result of changing environment conditions and/or prey composition, condition and availability. This study showed the potential use of blubber thickness as a proxy to estimate body fat condition in franciscana dolphins. Additionally, the fatty acid composition and stratrification of the blubber layer (skin-muscle) at the middle-ventral region was studied in 30 franciscanas. The lipids were extracted using chloroform-methanol and fatty acids methyl esters were obtained using BF3-methanol. Analyses were performed by gas-liquid chromatography. Fatty acids were identified by comparison of the retention time against commercial standards. Age determination estimated by counting GLGs (Growth Layer Groups) from teeth. Twenty-seven fatty acids were quantified (27/37), of which 16:1n-7 (37,14%) and 18:1n-9 (19,70%) exhibited the highest concentrations. Stratification of fatty acid concentration across the blubber layer was found where a continuous gradient of FA concentrations was evident either increasing or decreasing from the inner layer towards the skin. The shorter-chain saturated and monounsaturated fatty acids (12:0, 18:0, 15:1 and 14:1n-5) exhibited the highest relative amounts in the outer layer whereas polyunsaturated fatty acids (PUFA) 20:3, 20:5n-3, 22:6n-3, 20:4n-6 and 22:2 and the monounsaturated fatty acid 24:1n-9 exhibited the highest relative amounts in the inner blubber layer. The array of fatty acids identified differed among age categories and between females and males. Total PUFA in the inner layer increased with the age and this relationship was stronger for male franciscanas. On the other hand, total saturated fatty acids found in the outer layer decreased with the age an this relationship was stronger for females. There was no correlation between the ratio omega-3/ omega-6 and the age of the individuals for either the outer or inner blubber layer. The strongest degree of stratification was exhibited by adult males. This study describes for the first time the existence of stratification and the fatty acid composition of the blubber layer of franciscana dolphins from FMA IIIs.
Advisor:Jorge Pablo Castello; Eliana Badiale Furlong; Mirtha Lewis; Mônica Mathias Costa Muelbert
School:Fundação Universidade Federal do Rio Grande
Source Type:Master's Thesis
Keywords:Pontoporia blainvillei toninha blubber thickness body condition fatty acid composition stratification
Date of Publication:08/19/2005