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In Atlantic bottlenose dolphins ( Tursiops truncatus) the thickness and lipid content of blubber (the integument's specialized hypodermis) varies across ontogeny and with reproductive and nutritional state. Because the integument comprises up to 25% of total body mass in this species, ontogenetic changes in its lipid content may influence whole body buoyancy. The density and volume of the integument were measured and its buoyancy calculated across an ontogenetic series of dolphins and in pregnant and emaciated adults (total n= 45). Regional differences between the metabolically labile trunk integument and the structural tailstock integument were also investigated. Mean densities of both trunk and tailstock integument were similar across life history categories (trunk = 1,040.7 ± 14.1 kg/m3; tailstock = 1,077.1 ± 21.2 kg/m3) and were statistically similar to the density of seawater (1,026 kg/m3). The mean buoyant force of integument from the trunk (−1.01 ± 1.74 N) and tailstock (−0.30 ± 0.21 N) did not vary significantly across ontogeny. In contrast, pregnancy and emaciation did influence the integument's buoyancy, which ranged between 9 N and −45 N in these categories. Although neutral during growth, the integument's contribution to whole body buoyancy can be influenced by an individual's reproductive and nutritional status. [ABSTRACT FROM AUTHOR]

In Atlantic bottlenose dolphins Tursiops truncatus, both the thickness and lipid content of blubber vary across 0ntogeny and across individuals of differing reproductive and nutritional status. This study investigates how these changes in blubber morphology and composition influence its thermal properties. Thermal conductivity (W m-1 deg.-1, where deg. is °C) and thermal insulation (m² deg. W-1) of dolphin blubber were measured in individuals across an ontogenetic series (fetus through adult, N=36), pregnant females (N=4) and emaciated animals (N=5). These thermal properties were determined by the simultaneous use of two common experimental approaches, the heat flux disc method and the standard material method. Thickness, lipid and water content were measured for each blubber sample. Thermal conductivity and insulation varied significantly across ontogeny. Blubber from fetuses through sub-adults was less conductive (range=0.11–0.13±0.02 W m-1 deg.-1) than that of adults (mean=0.18 W m-1 deg.-1). The conductivity of blubber from pregnant females was similar to non-adult categories, while that of emaciated animals was significantly higher (0.24 ± 0.04 W m deg.-1) than all other categories. Blubber from sub-adults and pregnant females had the highest insulation values while fetuses and emaciated animals had the lowest. In nutritionally dependant life history categories, changes in blubber's thermal insulation were characterized by stable blubber quality (i.e. conductivity) and increased blubber quantity (i.e. thickness). In nutritionally independent animals, blubber quantity remained stable while blubber quality varied. A final, unexpected observation was that heat flux measurements at the deep blubber surface were significantly higher than that at the superficial surface, a pattern not observed in control materials. This apparent ability to absorb heat, coupled with blubber's fatty acid composition, suggest that dolphin integument may function as a phase change material. [ABSTRACT FROM AUTHOR]