Dr Kimberley Bennett
I am a Lecturer in marine biology and Deputy Programme leader for BSc (Hons) Marine Biology at Plymouth I am a personal tutor and I run field and skills week, a locally-based week of practical activities, for the Marine Biology degree programme. I am a staff member on the first and second year residential field courses to Roscoff and Portugal, respectively I teach the marine vertebrates component of BIOL115, Natural History, and MBIO215, Biology of Marine Organisms, which includes the taxonomy, evolution and physiology of key marine vertebrate groups I teach on the Conservation and Ecology of Marine Vertebrates third year module, focussing on telemetry, diet estimation and physiological ecology, I lead the third year Biology and Physiology of Marine Vertebrates module, focussing on the physiology of stress at whole animal and cellular levels.
Biological responses to stress are energetically costly. By diverting resources into the stress response, organisms shift their priorities for energy allocation. Changes to energy balance can have consequences for fitness and survival. Exposure to stress is therefore a strong selective pressure that acts at the population level to shape natural history.
Seals are interesting and informative model animals for the study of the stress, and its impact on energy balance. They routinely experience physiological stress as a normal part of their daily and seasonal activities. Seals are air breathing mammals that make a living under water in the cold, deep dark ocean, but need to come to the surface to breathe, and to come ashore to rest, breed and moult.
On a dive by dive basis they are exposed to a barrage of potentially damaging conditions. Diving on a single breath hold means they need to conserve oxygen and they restrict blood flow largely to the heart and brain. Other tissues therefore experience repeated ischaemia reperfusion, and the resulting sporadic and repeated hypoxia that can result in free radical damage. High levels of dissolved nitrogen in the blood stream, as a result of repeated diving, and their rapid rate of ascent at the end of a dive means they need to have mechanisms in place to avoid the bends and shallow water black out. All this is in the face of the high thermal conductivity of the water, which adds the risk of hypothermia if an animal has an insufficient amount of insulation. To avoid this problem seals have a thick blubber layer, which then creates added energetic costs of overcoming buoyancy during the descent phase of a dive.
While they are on land they are away from their food source, and so they need to fast. They face the possibility of overheating as a result of thick blubber. While they are fasting they are often engaged in highly metabolically costly activities such as regenerating hair, lactating, defending pups or territory, or just undergoing rapid development. Particularly during the breeding season, tension runs high on close packed breeding colonies and animals experience considerable aggression with the risk of injury and infection. Even if they find a quiet corner, it is possible that they experience oxidative damage or dehydration. Seals have a high fat diet, high body fat content and high levels of circulating glucose, all of which are reminiscent of the diabetic condition in humans. Seals are apex predators. Their individual and population level health can act as an indicator of the health of the ecosystem. However in addition to their ‘lifestyle stressors’, they face anthropogenic stress from direct or indirect competition from humans and other predators for access to fish; disturbance on haul out or displacement from foraging grounds as a result of human activity; and the accumulation of lipophilic contaminants in their blubber layer, which acts as a metabolic fuel source while they are fasting as well as insulation while at sea.
Being fat is very important for seals: in their first year, the survival of seal pups depends on how fat they are. Clearly, if stress has a negative impact on energy balance in these animals, it will have a detrimental effect at the population level by reducing recruitment.
I am interested in how these animals regulate storage and use of metabolic fuel sources, and the similarities and differences between seals and the development of obesity and diabetes in humans. I am also interested in how they withstand the natural (fasting, pressure change, hypoxia etc) and man-made (pollutants, disturbance etc) stressors that they encounter on a dive –by dive, daily or seasonal basis, and the links between susceptibility/ resilience and body condition.
Papers, chapters and proceedings published
Bennett, K.A., Macmillan, I.S., Hammill, M. and Currie, S. (2014) HSP70 abundance and antioxidant capacity in feeding and fasting gray seal pups: suckling is associated with higher levels of key cellular defenses. Physiol. Biochem. Zool. 87: 663-676.
Squires, N., Hodgson-Ball, K., Bennett, K.A., Votier, S. and Ingram, S. (2014) Using passive acoustics and shore based surveys to investigate the use of Lundy Island’s near shore water by small odontocetes. J. Lundy Field Soc. 4: 39-56.
Bennett, K.A., Hammill, M. and Currie, S. (2013) Liver glucose-6-phosphatase proteins in suckling and weaned grey seal pups: structural similarities to other mammals and relationship to nutrition, insulin signalling and metabolite levels. J. Comp. Physiol. B 183: 1075-1088.
Bennett, K.A., Fedak, M.A., Moss, S.E.W., Pomeroy, P.P., Speakman, J.R. and Hall A.J. (2013) The role of glucocorticoids in naturally fasting grey seal (Halichoerus grypus) pups: dexamethasone stimulates mass loss and protein loss, but not departure from the colony. J. Exp. Biol. 216: 984-991. DOI:10.1242/jeb.077438
Bennett, K.A. and Burchell, A. (2013) von Gierke Disease In Brenner’s Online Encyclopedia of Genetics, 2nd Edition. Elsevier. P 304-307.
Hammond, J.A., Hauton C., Bennett, K.A. and Hall A.J. (2012) Phocid seal leptin: tertiary structure and hydrophobic receptor binding site preservation during distinct leptin gene evolution. PLoS One 7: e35395. DOI:10.1371/journal.pone.0035395
Bennett, K. A., Moss, S.E.W., Pomeroy, P.P., Speakman, J. R. and Fedak, M. A. (2012) Effects of handling regime and sex on changes in cortisol, thyroid hormones and body mass in fasting grey seal pups. Comp. Biochem. Physiol. A 161: 69-76. DOI: 10.1016/j.cbpa.2011.09.003
Bennett, K.A., Forsyth, L. and Burchell, A. (2011) Functional analysis of the 5’ flanking region of the human G6PC3 gene: regulation of promoter activity by glucose, pyruvate, AMP kinase and the pentose phosphate pathway. Mol. Genetics Metab. 103: 254-261.
Bennett, K. A., McConnell, B. J., Moss, S. E.W., Pomeroy, P.P., Speakman, J.R. and Fedak, M. (2010) Effect of age and body mass on the development of diving capabilities of grey seal pups: costs and benefits of the postweaning fast. Physiol. Biochem. Zool. 83: 911-923.
Hall, A.J., K.A. Bennett and J.A. Hammond (2009) Evolution of the blood–gas barrier in diving mammals. In: S.F. Perry, S. Morris, T. Breuer, N. Pajor and M. Lambertz, Editors, 2nd International Congress of Respiratory Science, Tharax Verlag, Hildesheim, Berlin, pp. 87–88.
Bennett, K. A., Speakman, J. R., Moss, S.E.W., Pomeroy, P.P. and Fedak, M. A. (2007) Effects of mass and body composition on fasting fuel utilisation in grey seal pups (Halichoerus grypus; Fabricius): an experimental study using supplementary feeding. J. Exp. Biol. 210: 3043-3053.
Hammond, J., Bennett, K. A., Walton, M. and Hall, A.J. (2005) Molecular cloning and expression of leptin in grey and harbor seal blubber, bone marrow and lung and its potential role in marine mammal respiratory physiology Am. J. Physiol. 289: R545-R553.
McCafferty, D., Moss, S., Bennett, K. A., Pomeroy, P.P. (2005) Factors influencing the radiative surface temperature of grey seal (Halichoerus grypus) pups during early and late lactation. J. Comp. Physiol. B. 175: 423-431.
Bennett, K. A., McConnell, B. J. and Fedak, M. (2001). Diurnal and seasonal variations in the duration and depth of the longest dives in southern elephant seals (Mirounga leonina): possible physiological and behavioural constraints. J. Exp. Biol. 204: 649-662.
Papers and chapters in press
Bennett, K. A. Using a discussion about scientific controversy to teach central concepts in experimental design. Accepted in Teaching Statistics. 24th Nov 2014.
Bennett, K. A. Hughes J., Stamatas S., Brand S., Foster N.L., Moss S.E.W. and Pomeroy, P.P. Adiponectin and insulin in grey seals during suckling and fasting: relationship with nutritional state and body mass during nursing in mothers and pups. Accepted in Physiol. Biochem. Zool. 31st January 2015. Due for publication May/ June 2015
Reports & invited lectures
Hall, A., Hammond, J., Bennett, K.A., Walton, M. and Fedak, M. (2004) Leptin and its role in lung inflation and the regulation of fat stores In: Sea Mammal Research Unit Scientific Report. Sea Mammal Research Unit/ Broglia Press/ NERC
Bennett, K. A., McConnell, B. J. and Fedak, M. (2003). Dispersal of grey seal pups. SCOS briefing paper available at www.smru.st-and.ac.uk
Invited lectures and talks
Life in the Fast Lane. Guest speaker. Durham University. Feb 2014
Whole Animal and Cellular Stress in Seals. Stress Physiology and Behaviour Workshop. Glasgow University. Jan 2015