James E. Blum

The ontogenetic changes in the thermal properties of blubber from Atlantic bottlenose dolphin Tursiops truncatus.

SUMMARY In Atlantic bottlenose dolphins Tursiops truncatus, both the thickness and lipid content of blubber vary across ontogeny 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 blubbers 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 blubbers fatty acid composition, suggest that dolphin integument may function as a phase change material.

Signature-whistle production in undisturbed free-ranging bottlenose dolphins (Tursiops truncatus).

Data from behavioural observations and acoustic recordings of free–ranging bottlenose dolphins (Tursiops truncatus) were analysed to determine whether signature whistles are produced by wild undisturbed dolphins, and how whistle production varies with activity and group size. The study animals were part of a resident community of bottlenose dolphins near Sarasota, Florida, USA. This community of dolphins provides a unique opportunity for the study of signature–whistle production, since most animals have been recorded during capture–release events since 1975. Three mother–calf pairs and their associates were recorded for a total of 141.25 h between May and August of 1994 and 1995. Whistles of undisturbed dolphins were compared with those recorded from the same individuals during capture–release events. Whistles were conservatively classified into one of four categories: signature, probable signature, upsweep or other. For statistical analyses, signature and probable signature whistles were combined into a ‘signature’ category; upsweep and other whistles were combined into a ‘non–signature’ category. Both ‘signature’ and ‘non–signature’ whistle frequencies significantly increased as group size increased. There were significant differences in whistle frequencies across activity types: both ‘signature’ and ‘non–signature’ whistles were most likely to occur during socializing and least likely to occur during travelling. There were no significant interactions between group size and activity type. Signature and probable signature whistles made up ca. 52% of all whistles produced by these free–ranging bottlenose dolphins.

Whistles as Potential Indicators of Stress in Bottlenose Dolphins (Tursiops truncatus)

Abstract We examined the possibility that parameters of bottlenose dolphin signature whistles may serve as indicators of stress. Bottlenose dolphins (Tursiops truncatus) in Sarasota Bay, Florida, were recorded during brief capture–release events, which are potentially a source of short-term stress to these dolphins, although no effects of chronic or long-term stress have been observed over the 37+-year duration of the research. Whistles recorded during both brief capture–release and undisturbed, free-ranging conditions were examined to determine whether whistle parameters differ during capture–release versus undisturbed conditions; at the beginning of a capture–release session versus at the end of a session; during an individuals 1st capture–release session versus later capture–release sessions; and when a mother is caught and released with a dependent calf versus without a dependent calf (i.e., she has no dependent calf at the time of capture–release). We examined a variety of acoustic parameters, including whistle rate, number of loops (repetitive elements), maximum and minimum frequency, and loop, interloop, and whistle duration. We found that whistle rate and number of loops were greater during brief capture–release events than during undisturbed conditions; number of loops decreased and loop duration increased over the duration of a capture–release session; whistle rates decreased with number of capture–release sessions; and females caught and released with dependent calves produced whistles with higher maximum frequencies and shorter interloop intervals than when they did not have dependent calves. Thus, whistles appear to have potential as noninvasive indicators of stress in bottlenose dolphins. Further research is warranted in this area, for example by correlating physiological indices to whistle rates under varying levels of stress. Reliable, noninvasive correlates of stress could be used to monitor dolphins in a variety of circumstances, such as during exposure to anthropogenic noise.

Maize Leaf Epiphytic Bacteria Diversity Patterns Are Genetically Correlated with Resistance to Fungal Pathogen Infection

Plant leaves host a specific set of microbial epiphytes. Plant genetic and solar UV-B radiation effects on the diversity of the phyllosphere were examined by measuring epiphytic bacterial ribosomal DNA diversity in a maize recombinant inbred (RI) mapping population. Several chromosomal quantitative trait loci (QTL) with significant effects on bacterial diversity were identified, some of which had effects only in the presence of UV-B radiation and others that had effects both with and without UV-B. Candidate genes with allele-specific effects were mapped to the bacterial diversity chromosomal regions. A glutamate decarboxylase candidate gene was located at a UV-B-specific chromosomal locus, and in a comparison between two RI lines with contrasting bacterial diversity phenotypes, high bacterial diversity was associated with high levels of glutamate decarboxylase enzyme activity, a component of the gamma-aminobutyric acid (GABA) pathway. The bacterial diversity loci exhibited a significant overlap with loci connected with Southern leaf blight (SLB) susceptibility in the field. A SLB-resistant inbred genotype had less beta bacterial diversity, and antibiotic treatment of inbreds increased this diversity. These results suggest that the GABA pathway is genetically associated with phyllosphere bacterial diversity. Furthermore, the colocalization of QTL between low bacterial diversity and fungal blight-resistance and the increase in beta diversity in antibiotic-treated leaves suggest that occupation of leaf habitats by a particular set of suppressive bacteria may restrict phyllosphere bacterial variability and increase resistance to fungal infection.

Seasonal patterns of heat loss in wild bottlenose dolphins (Tursiops truncatus)

This study investigated patterns of heat loss in bottlenose dolphins (Tursiops truncatus) resident to Sarasota Bay, FL, USA, where water temperatures vary seasonally from 11 to 33°C. Simultaneous measurements of heat flux (HF) and skin surface temperature were collected at the body wall and appendages of dolphins during health-monitoring events in summer (June 2002–2004) and winter (February 2003–2005). Integument thickness was measured and whole body conductance (W/m2 °C) was estimated using HF and colonic temperature measurements. Across seasons, HF values were similar at the appendages, but their distribution differed significantly at the flipper and fluke. In summer, these appendages displayed uniformly high values, while in winter they most frequently displayed very low HF values with a few high HF values. In winter, blubber thickness was significantly greater and estimated conductance significantly lower, than in summer. These results suggest that dolphins attempt to conserve heat in winter. In winter, though, HF values across the body wall were similar to (flank) or greater than (caudal keel) summer values. It is likely that higher winter HF values are due to the steep temperature gradient between the body core and colder winter water, which may limit the dolphin’s ability to decrease heat loss across the body wall.

Metabolic influences of fiber size in aerobic and anaerobic locomotor muscles of the blue crab, Callinectes sapidus.

SUMMARY Diameters of some white locomotor muscle fibers in the adult blue crab, Callinectes sapidus, exceed 500 μm whereas juvenile white fibers are <100 μm. It was hypothesized that aerobically dependent processes, such as metabolic recovery following burst contractions, will be significantly impeded in the large white fibers. In addition, dark aerobic fibers of adults, which rely on aerobic metabolism for both contraction and recovery, grow as large as the white fibers. These large aerobic fibers are subdivided, however, thus decreasing the effective diameter of each metabolic functional unit and enabling aerobic contraction. The two goals of this study were: (1) to characterize the development of subdivisions in the dark levator muscle fibers and (2) to monitor post-contractile metabolism as a function of fiber size in aerobic and anaerobic levator muscles. Dark levator muscle fibers from crabs ranging from <0.1 g to >190 g were examined with transmission electron microscopy to determine the density of mitochondria and subdivision diameters. Across all size classes, there was a constant mitochondrial fractional area (25% of the total subdivision area) and subdivision size (mean diameter of 36.5±2.7 μm). Thus, blue crab dark levator fibers are unusual in having metabolic functional units (subdivisions) that do not increase in size during development while the contractile functional units (fibers) grow hypertrophically. The body mass scaling of post-contractile lactate dynamics was monitored during recovery from anaerobic, burst exercise in white and dark muscle, and in hemolymph. There were no differences among size classes in lactate accumulation during exercise in either muscle. However, in white fibers from large crabs, lactate continued to increase after exercise, and lactate removal from tissues required a much longer period of time relative to smaller crabs. Differences in lactate removal among size classes were less pronounced in dark fibers, and post-contractile lactate accumulation was significantly higher in white than in dark fibers from large animals. These data suggest that the large white fibers invoke anaerobic metabolism following contraction to accelerate certain phases of metabolic recovery that otherwise would be overly slow. This implies that, in addition to the typical mass-specific decrease in oxidative capacity that accompanies increases in animal mass, aerobic metabolic processes become increasingly limited by surface area to volume and intracellular diffusion constraints in developing white muscle fibers.

Lung size and thoracic morphology in shallow- and deep-diving cetaceans

Shallow‐diving, coastal bottlenose dolphins (Tursiops truncatus) and deep‐diving, pelagic pygmy and dwarf sperm whales (Kogia breviceps and K. sima) will experience vastly different ambient pressures at depth, which will influence the volume of air within their lungs and potentially the degree of thoracic collapse they experience. This study tested the hypotheses that lung size will be reduced and/or thoracic mobility will be enhanced in deeper divers. Lung mass (T. truncatus, n = 106; kogiids, n = 18) and lung volume (T. truncatus, n = 5; kogiids, n = 4), relative to total body mass, were compared. One T. truncatus and one K. sima were cross‐sectioned to calculate lung, thoracic vasculature, and other organ volumes. Excised thoraxes (T. truncatus, n = 3; kogiids, n = 4) were mechanically manipulated to compare changes in thoracic cavity shape and volume. Kogiid lungs were half the mass and one‐fifth the volume of those of similarly sized T. truncatus. The lungs occupied only 15% of the total thoracic cavity volume in K. sima and 37% in T. truncatus. The kogiid and dolphin thoraxes underwent similar changes in shape and volume, although the width of the thoracic inlet was relatively constrained in kogiids. A broader phylogenetic comparison demonstrated that the ratio of lung mass to total body mass in kogiids, physeterids, and ziphiids was similar to that of terrestrial mammals, while delphinids and phocoenids possessed relatively large lungs. Thus, small lung size in deep‐diving odontocetes may be a plesiomorphic character. The relatively large lung size of delphinids and phocoenids appears to be a derived condition that may permit the lung to function as a site of respiratory gas exchange throughout a dive in these rapid breathing, short‐duration, shallow divers. J. Morphol., 2010.

Ontogenetic changes in the structural stiffness of the tailstock of bottlenose dolphins (Tursiops truncatus).

SUMMARY Late-term fetal bottlenose dolphins (Tursiops truncatus) are bent ventrolaterally en utero, requiring extreme flexibility of the axial skeleton and associated soft tissues. At birth, neonatal dolphins must immediately swim to the surface to breath, yet the dorsoventral oscillations used during locomotion may be compromised by the lateral flexibility evident in the fetus. The unique fetal position of dolphins, coupled with their need to swim at birth, places conflicting mechanical demands on the tailstock. Our previous research demonstrated that neonatal dolphins possess laterally placed, axial muscles that are functionally specialized to actively maintain the straightened posture of the tailstock. Here, we investigated the development of passive lateral stability in the tailstock of bottlenose dolphins by performing whole-body bending tests on an ontogenetic series of stranded dolphin specimens (N=15), including fetuses, neonates and juveniles (total length 58–171 cm). Structural stiffness increased, while overall body curvature decreased, with increasing body length. Scaling analyses suggest that increased structural stiffness is due to increases in size and probably changes in the passive material properties of the tailstock through ontogeny. The neutral zone was approximately constant with increasing size, while the relative neutral zone (neutral zone/total length) decreased. The lateral stability of the tailstock appears to be controlled by a combination of active and passive systems and the role of these systems varies through ontogeny. While neonates use active, muscular mechanisms to limit lateral deformations of the tailstock, the stability of the maturing tailstock is due primarily to its passive tissue properties.

Assessment of DNA Damage as a Tool to Measure UV-B Tolerance in Soybean Lines Differing in Foliar Flavonoid Composition

Damage to DNA, in the form of cyclobutane pyrimidine dimers (CPD), may occur in soybean (Glycine max (L.) Merr) plants when they are exposed to increasing levels of ultraviolet-B (UV-B) radiation. Flavonoids and other phenolics accumulate in the epidermal layer of leaves and may provide protection for sensitive tissues including DNA molecules. We evaluated the steady state levels of accumulated damage and the protection afforded by flavonoids in two soybean isolines: Clark producing high levels of flavonoids, and Clark-magenta producing extremely low flavonoid levels. Both cultivars were grown in the field under ambient and supplemental UV-B radiation. Leaf tissue was harvested in a diurnal sequence, and the samples were analyzed. Two methods of analysis were used in order to develop a common reference point between the two. In one method, DNA was isolated and treated with UV endonuclease, and the DNA fragments were separated using unidirectional pulsed field electrophoresis and quantified through electronic imaging. In the alternate method, a western blotting procedure, immobilized DNA was reacted with monoclonal antibodies specific to CPD DNA damage. Results were similar in both techniques and show lesion frequency to be low in both isolines. However significant differences were found between cultivars, UV treatments, time of day collected, and levels of PAR. The average level of dimers per megabase for the isoline Clark was ∼4 (with or without supplemental UV), and for Clark-magenta, ∼4 for samples with no supplemental UV and ∼6 for those exposed to supplemental UV radiation. Diurnally, dimer levels were frequently higher in the Clark-magenta isoline, especially when exposed to supplemental UV-B. Both isolines appear to be either well-protected from DNA damage, or repair is efficient enough to minimize biologically significant accumulation of DNA damage. This suggests that protection mechanisms, other than flavonoids alone, contribute to maintenance of DNA integrity in soybean.