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"Deep diving Physiological aspects."
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Biophysics and Diving Decompression Phenomenology
The biophysics of diving and decompression in the human body are complex. The average individual experiences atmospheric pressure swings of 3% at sea level and over 20% at altitudes greater than a mile. Divers and their equipment can experience compressions and decompressions in orders of greater magnitude than pressures outside water, all within considerably shorter time spans. The understanding of the mechanics behind diving is based on absolute pressure and pressure changes. While these mechanics are readily quantified in physics, chemistry, and engineering applications, the physiological and medical aspects of pressure changes in living systems need to be understood clearly to assess the safety of routine divers. This monograph is a compilation of a body of knowledge on biophysics, gas transport, bubble studies and physiological models used for diving and hyperbaric applications. Information in the monograph is divided into three parts that cover biophysics and models, data correlation and validation approaches and practical applications, respectively. The book is a useful resource for researchers and maritime professionals who wish to understand the biophysics behind underwater diving and decompression for the purpose of maritime operations as well as diving simulation applications.
eBook
Pygmy sperm whale multi-omics data reveal hypoxia adaptations in deep-diving cetaceans
Background
Deep-diving cetaceans tolerate acute hypoxia better than their terrestrial ancestors and shallow-diving counterparts. However, our poor understanding of how genetic factors, cellular functions, and physiological characteristics combine to drive hypoxia adaptation in deep-diving cetaceans remains a critical gap.
Results
Here, we studied the genetic basis for this ability by creating a de novo genome assembly for the pygmy sperm whale (
Kogia breviceps
) and comparatively analyzing genomes from 12 cetacean species, including 2 other deep-diving cetaceans. We also sequenced and compared single-nucleus RNA data from the muscle and heart of the pygmy sperm whale and its terrestrial relative
Bos taurus
. We found that genetic and cellular changes in the HIF-1 pathway, electron transport chain, glucose and fatty acid catabolism, and heart rate may contribute to hypoxia tolerance in deep-diving cetaceans. Key adaptations include rapid evolution of glycolysis-related genes (
PYGM
and
ENO3
), differential expression of HIF-1 pathway genes like
ARNT
, and accelerated conserved noncoding elements in genes such as
ATP5F1E
(ATP synthase) and
DMD
(dystrophin). We found an increase in myocytes and type II cardiomyocytes in the pygmy sperm whale’s muscle and heart tissues, which may support energy metabolism and homeostasis during deep dives.
Conclusions
These findings suggest deep-diving cetaceans have unique genetic and cellular adaptations to cope with hypoxia, offering insights into how mammals handle low oxygen levels at the cellular level.
Journal Article
microRNA profiling in the Weddell seal suggests novel regulatory mechanisms contributing to diving adaptation
Background
The Weddell Seal (
Leptonychotes weddelli
) represents a remarkable example of adaptation to diving among marine mammals. This species is capable of diving > 900 m deep and remaining underwater for more than 60 min. A number of key physiological specializations have been identified, including the low levels of aerobic, lipid-based metabolism under hypoxia, significant increase in oxygen storage in blood and muscle; high blood volume and extreme cardiovascular control. These adaptations have been linked to increased abundance of key proteins, suggesting an important, yet still understudied role for gene reprogramming.
In this study, we investigate the possibility that post-transcriptional gene regulation by microRNAs (miRNAs) has contributed to the adaptive evolution of diving capacities in the Weddell Seal.
Results
Using small RNA data across 4 tissues (brain, heart, muscle and plasma), in 3 biological replicates, we generate the first miRNA annotation in this species, consisting of 559 high confidence, manually curated miRNA loci. Evolutionary analyses of miRNA gain and loss highlight a high number of Weddell seal specific miRNAs.
Four hundred sixteen miRNAs were differentially expressed (DE) among tissues, whereas 80 miRNAs were differentially expressed (DE) across all tissues between pups and adults and age differences for specific tissues were detected in 188 miRNAs. mRNA targets of these altered miRNAs identify possible protective mechanisms in individual tissues, particularly relevant to hypoxia tolerance, anti-apoptotic pathways, and nitric oxide signal transduction. Novel, lineage-specific miRNAs associated with developmental changes target genes with roles in angiogenesis and vasoregulatory signaling.
Conclusions
Altogether, we provide an overview of miRNA composition and evolution in the Weddell seal, and the first insights into their possible role in the specialization to diving.
Journal Article
Size Distribution of Sperm Whales Acoustically Identified during Long Term Deep-Sea Monitoring in the Ionian Sea
The sperm whale (Physeter macrocephalus) emits a typical short acoustic signal, defined as a \"click\", almost continuously while diving. It is produced in different time patterns to acoustically explore the environment and communicate with conspecifics. Each emitted click has a multi-pulse structure, resulting from the production of the sound within the sperm whale's head. A Stable Inter Pulse Interval (Stable IPI) can be identified among the pulses that compose a single click. Applying specific algorithms, the measurement of this interval provides useful information to assess the total length of the animal recorded. In January 2005, a cabled hydrophone array was deployed at a depth of 2,100 m in the Central Mediterranean Sea, 25 km offshore Catania (Ionian Sea). The acoustic antenna, named OνDE (Ocean noise Detection Experiment), was in operation until November 2006. OνDE provided real time acoustic data used to perform Passive Acoustic Monitoring (PAM) of cetacean sound emissions. In this work, an innovative approach was applied to automatically measure the Stable IPI of the clicks, performing a cepstrum analysis to the energy (square amplitude) of the signals. About 2,100 five-minute recordings were processed to study the size distribution of the sperm whales detected during the OνDE long term deep-sea acoustic monitoring. Stable IPIs were measured in the range between 2.1 ms and 6.4 ms. The equations of Gordon (1991) and of Growcott (2011) were used to convert the IPIs into measures of size. The results revealed that the sperm whales recorded were distributed in length from about 7.5 m to 14 m. The size category most represented was from 9 m to 12 m (adult females or juvenile males) and specimens longer than 14 m (old males) seemed to be absent.
Journal Article
Southern elephant seals (Mirounga leonina Linn.) depredate toothfish longlines in the midnight zone
Humans have devised fishing technologies that compete with marine predators for fish resources world-wide. One such fishery for the Patagonian toothfish (Dissostichus eleginoides) has developed interactions with a range of predators, some of which are marine mammals capable of diving to extreme depths for extended periods. A deep-sea camera system deployed within a toothfish fishery operating in the Southern Ocean acquired the first-ever video footage of an extreme-diver, the southern elephant seal (Mirounga leonina), depredating catch from longlines set at depths in excess of 1000m. The interactions recorded were non-lethal, however independent fisheries observer reports confirm elephant seal-longline interactions can be lethal. The seals behaviour of depredating catch at depth during the line soak-period differs to other surface-breathing species and thus presents a unique challenge to mitigate their by-catch. Deployments of deep-sea cameras on exploratory fishing gear prior to licencing and permit approvals would gather valuable information regarding the nature of interactions between deep diving/dwelling marine species and longline fisheries operating at bathypelagic depths. Furthermore, the positive identification by sex and age class of species interacting with commercial fisheries would assist in formulating management plans and mitigation strategies founded on species-specific life-history strategies.
Journal Article
Extensive use of mesopelagic waters by a Scalloped hammerhead shark (Sphyrna lewini) in the Red Sea
Background
Despite being frequently landed in fish markets along the Saudi Arabian Red Sea coast, information regarding fundamental biology of the Scalloped hammerhead shark (
Sphyrna lewini
) in this region is scarce. Satellite telemetry studies can generate important data on life history, describe critical habitats, and ultimately redefine management strategies for sharks. To better understand the horizontal and vertical habitat use of
S. lewini
in the Red Sea and to aid with potential future development of zoning and management plans for key habitats, we deployed a pop-up satellite archival transmitting tag to track a single female specimen (240 cm total length) for a tracking period of 182 days.
Results
The tag was physically recovered after a deployment period of 6 months, thus providing the complete archived dataset of more than one million depth and temperature records. Based on a reconstructed, most probable track, the shark travelled a circular distance of approximately 1000 km from the central Saudi Arabian Red Sea southeastward into Sudanese waters, returning to the tagging location toward the end of the tracking period. Mesopelagic excursions to depths between 650 and 971 m occurred on 174 of the 182 days of the tracking period. Intervals between such excursions were characterized by constant oscillatory diving in the upper 100 m of the water column.
Conclusions
This study provides evidence that mesopelagic habitats might be more commonly used by
S. lewini
than previously suggested. We identified deep diving behavior throughout the 24-h cycle over the entire 6-month tracking period. In addition to expected nightly vertical habitat use, the shark exhibited frequent mesopelagic excursions during daytime. Deep diving throughout the diel cycle has not been reported before and, while dive functionality remains unconfirmed, our study suggests that mesopelagic excursions may represent foraging events within and below deep scattering layers. Additional research aimed at resolving potential ecological, physiological and behavioral mechanisms underpinning vertical movement patterns of
S. lewini
will help to determine if the single individual reported here is representative of
S. lewini
populations in the Red Sea.
Journal Article
Dive into the deep blue yonder : anatomy of a freedive
Explains the physical and mental processes involved in freediving at the surface, 10 metres down, 20m, 30m, 40m to 100m, 102m, the return and the surface. Includes biographical material about the freediver. Source: National Library of New Zealand Te Puna Matauranga o Aotearoa, licensed by the Department of Internal Affairs for re-use under the Creative Commons Attribution 3.0 New Zealand Licence.
Newspaper Article
Fighting the Bends in the Indian Ocean
A scientific cruise in the Seychelles ended in a dramatic cooperative effort to rescue two Soviet researchers suffering from the bends.
Journal Article