Biology subjects

Fahlman, A.

Publications and source records attributed to Fahlman, A..

3 recordsLinked to original sources

bioRxiv2026

Quantitative Ultrasound Analysis of Gas Embolic Disease in Bycaught Sea Turtles

ObjectivesBycatch-related decompression after forced submersion can result in severe gas embolic disease in sea turtles. This work used qualitative and quantitative ultrasound analyses, including gas grading, brightness analysis, and texture feature extraction, to investigate organ-specific gas burden and temporal evolution in the hearts, kidneys, and livers of bycaught sea turtles. Materials and MethodsUltrasound imaging of the hearts, kidneys, and livers of bycaught turtles was performed as part of veterinary evaluation either onboard fishing vessels immediately after surfacing (boat group, n=47) or after longer periods at shore-based facilities (shore group, n=30). Gas burden in each ultrasound scan was graded on an ordinal scale from 0 (no gas) to 5 (gas completely shadowing organ anatomy). Temporal differences in gas burden were compared between the shore and boat groups. Quantitative brightness and texture features were extracted from all organs, including contrast, correlation, homogeneity, and energy from liver and kidney data. A multivariate logistic regression model with leave-one-out cross-validation was conducted, with shore versus boat as a binary outcome (surrogate of post-surfacing decompression state) and ultrasound texture metrics as independent variables. ResultsMedian grades from the first ultrasound scan were significantly higher in the boat group than in the shore group for the liver, kidney, and heart (3, 3, and 3 vs 1, 1, and 0, respectively). This pattern coincided with a difference in the mean duration until the first scan which was conducted being 54 min for the onboard studies vs 330 minutes in the shore group. Mean pixel brightness within cardiac and liver regions of interest increased with rising bubble grade before decreasing at the highest grades, consistent with acoustic shadowing at severe gas burden. Texture features demonstrated significant organ-specific changes with increasing gas burden, and the regression models achieved areas under the receiver operating characteristic curve of 0.92 for liver texture features and 0.83 for kidney texture features. ConclusionsThese findings demonstrate organ-specific differences in gas evolution over time. Quantitative ultrasound features were associated with gas burden and post-surfacing interval in bycaught sea turtles. These findings support the feasibility of quantitative ultrasound biomarkers for assessment of decompression-related gas burden.

physiology↗

bioRxiv2026

Food reward in Bottlenose Dolphins (Tursiops truncatus) and Belugas Whales (Delphinapterus leucas) reduces heart rate and increase heart rate variability.

1.BackgroundHeart rate (HR) and HR variability (HRV) reflect the autonomic modulation of cardiac activity and are key indicators of physiological state and stress in vertebrates. However, measuring these parameters in cetaceans has been historically challenging due to the difficulty of recording electrocardiograms (ECGs) underwater. MethodsWe developed an all-in-one ECG suction-cup to record HR during apnea, respiration and food rewards in bottlenose dolphins (Tursiops truncatus, N = 8) and belugas (Delphinapterus leucas, N = 2). Moreover, we obtain comparative measurements of ECG waveform and HR oscillation in one killer whale (Orcinus orca). ResultsSpecies-specific ECG patterns were observed, including biphasic T waves in all three species and bifid P waves unique to belugas. All three species exhibited oscillations in resting HR and pronounced bradycardia during short apnea ([~]1 min), reflecting respiratory-linked autonomic modulation. Moreover, HR oscillations persisted throughout apnea, possibly reflecting a mechanism to cyclically improve body oxygenation during diving. Short-term food deprivation had no significant effects on bottlenose dolphins and belugas HR, while subsequent feeding ad libitum reduced HR (by [~]20% in dolphins, [~]40% in belugas) and increased HRV, suggesting the activation of vagal modulation. ConclusionsThis study establishes baseline HR and HRV parameters during breathing, apnea and food reward in three cetacean species, highlighting autonomic modulation across different behaviors and conditions and validate a non-invasive tool for studying marine mammal physiology.

physiology↗

bioRxiv2021

An integrated comparative physiology and molecular approach pinpoints mediators of breath-hold capacity in dolphins

Ischemic events, such as ischemic heart disease and ischemic stroke, are the number one cause of death globally. Ischemia prevents blood, carrying essential nutrients and oxygen, from reaching tissues and organ systems, leading to cell and tissue death, and eventual organ failure. While humans are relatively intolerant to these ischemic events, other species, such as marine mammals, have evolved remarkable tolerance to chronic ischemia/reperfusion during diving. Here we capitalized on the unique adaptations of bottlenose dolphins (Tursiops truncatus) as a comparative model of ischemic stress and hypoxia tolerance to identify molecular features associated with breath-holding. Using RNA-Seq we observed time-dependent upregulation of the arachidonate 5-lipoxygenase (ALOX5) gene during breath-holding. Consistent with the RNA-Seq data, we also observed increased ALOX5 enzymatic activity in the serum of dolphins undergoing breath holds. ALOX5 has previously been shown to be activated during hypoxia in rodent models, and its metabolites, leukotrienes, induce vasoconstriction. The upregulation of ALOX5 occurred within the estimated aerobic dive limit of the species, suggesting that ALOX5 enzymatic activity may promote tolerance to ischemic stress through sustained vasoconstriction in dolphins during diving. These observations pinpoint a potential molecular mechanism by which dolphins, and perhaps other marine mammals, have adapted to the prolonged breath-holds associated with diving.

physiology↗