Swimming capabilities of deep-sea sharks through velocity, anatomical, physiological, and morphological analyses

• Main Author: Pinte, Nicolas
• Other Authors: UCL - SST/ELI - Earth and Life Institute, UCL - SST/ELI/ELIB - Biodiversity, UCL - Faculté des Sciences, Mallefet, Jérôme, De Keersmaecker, Marie-Laurence, Debier, Cathy, Silvestre, Frédéric, Seret, Bernard, Zintzen, Vincent
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: 2019
• Subjects: Deep-sea; Buoyancy; Morphology; Metabolism; Sharks; Swimming capabilities; Physiology; Greenland; Somniosus microcephalus
• Online Access: http://hdl.handle.net/2078.1/227670

In marine biology, one of the main objectives is to characterize the ecology of organisms: how they live, move, hunt, reproduce, etc. For that purpose, the study of swimming capabilities remains a feature providing several ecological information, especially for sharks which are mainly active predators. Studies regarding shark swimming capabilities have been initiated a long time ago for shallow-water species. They allowed highlighting differences between species explaining shark distribution, home range but also several internal adaptations related to their locomotor capabilities. While swimming capabilities start to be well known for shallow-water species, information regarding deep-sea sharks is still poorly documented. Indeed, only the speeds of the Greenland shark (Somniosus microcephalus) and the bluntnose sixgills shark (Hexancheus griseus) were measured using satellite telemetry and revealed the slowest velocity recorded for a shark. Other studies have focused on indirect measurements (proxies) of the locomotor muscle metabolism to estimate the swimming capabilities. They have shown that anaerobic metabolism of deep-sea species is lower than their shallow-water counterparts. In contrast, the aerobic metabolism does not show significant difference. Therefore, authors have concluded that deep-sea sharks should have lower swimming capabilities than their shallow-water counterparts. This conclusion is mainly based on two hypotheses: (i) the effect of the cold environment decreasing muscle activity and (ii) the visual interaction hypothesis which suggests that the swimming capabilities of an organism decrease when it lives in a darker environment. However, the low number of deep-sea shark species considered in these studies does not allow to draw this general conclusion for all deep-sea sharks. In this work, we studied the swimming capabilities of several deep-sea sharks from the Squaliformes order. Cruise swimming speed values were obtained using stereo-video analyses. Data analyses have revealed that not all ...