Conditioned Variation in Heart Rate During Static Breath-Holds in the Bottlenose Dolphin (Tursiops truncatus)
Abstract
Previous reports suggested the existence of direct somatic motor control over heart rate (fH) responses during diving in some marine mammals, as the result of a cognitive and/or learning process rather than being a reflexive response. This would be beneficial for O2storage management, but would also allow ventilation-perfusion matching for selective gas exchange, where O2and CO2can be exchanged with minimal exchange of N2. Such a mechanism explains how air breathing marine vertebrates avoid diving related gas bubble formation during repeated dives, and how stress could interrupt this mechanism and cause excessive N2exchange. To investigate the conditioned response, we measured thefH-response before and during static breath-holds in three bottlenose dolphins (Tursiops truncatus) when shown a visual symbol to perform either a long (LONG) or short (SHORT) breath-hold, or during a spontaneous breath-hold without a symbol (NS). The averagefH(ifHstart), and the rate of change infH(difH/dt) during the first 20 s of the breath-hold differed between breath-hold types. In addition, the minimum instantaneousfH(ifHmin), and the average instantaneousfHduring the last 10 s (ifHend) also differed between breath-hold types. The difH/dt was greater, and the ifHstart, ifHmin, and ifHendwere lower during a LONG as compared with either a SHORT, or an NS breath-hold (P< 0.05). Even though the NS breath-hold dives were longer in duration as compared with SHORT breath-hold dives, the difH/dt was greater and the ifHstart, ifHmin, and ifHendwere lower during the latter (P< 0.05). In addition, when the dolphin determined the breath-hold duration (NS), thefHwas more variable within and between individuals and trials, suggesting a conditioned capacity to adjust thefH-response. These results suggest that dolphins have the capacity to selectively alter thefH-response during diving and provide evidence for significant cardiovascular plasticity in dolphins.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Nov 24, 2020
- Source ID
- 10.3389/fphys.2020.604018
Entities
People
- Andreas Fahlman
- Ashley M Blawas
- Bruno Cozzi
- Marek Malik
- Mercy Manley
- Sandra Jabas
- Vincent M Janik
Organizations
- Office of Naval Research