title: Unique fur and skin structure in harbour seals (Phoca vitulina)--thermal insulation, drag reduction, or both?
abstract: Vertebrate surface structures, including mammalian skin and hair structures, have undergone various modifications during evolution in accordance with functional specializations. Harbour seals rely on their vibrissal system for orientation and foraging. To maintain tactile sensitivity even at low temperatures, the vibrissal follicles are heated up intensely, which could cause severe heat loss to the environment. We analysed skin samples of different body parts of harbour seals, and expected to see higher hair densities at the vibrissal pads as a way to reduce heat loss. In addition to significantly higher hair densities around the vibrissae than on the rest of the body, we show a unique fur structure of hair bundles consisting of broad guard hairs along with hairs of a new type, smaller than guard hairs but broader than underhairs, which we defined as 'intermediate hairs'. This fur composition has not been reported for any mammal so far and may serve for thermal insulation as well as drag reduction. Furthermore, we describe a scale-like skin structure that also presumably plays a role in drag reduction.
authors: Institute for Biosciences, Sensory and Cognitive Ecology, University of Rostock, Albert-Einstein-Strasse 3, 18059 Rostock, Germany Marine Science Center, Am Yachthafen 3A, 18119 Rostock, Germany.
authors: Nicola
authors: N
authors: Erdsack
authors: Institute for Biosciences, Sensory and Cognitive Ecology, University of Rostock, Albert-Einstein-Strasse 3, 18059 Rostock, Germany Marine Science Center, Am Yachthafen 3A, 18119 Rostock, Germany.
authors: Guido
authors: G
authors: Dehnhardt
authors: Department of Anatomy, Rostock University Medical Center, Gertrudenstrasse 9, 18057 Rostock, Germany.
authors: Martin
authors: M
authors: Witt
authors: Department of Anatomy, Rostock University Medical Center, Gertrudenstrasse 9, 18057 Rostock, Germany.
authors: Andreas
authors: A
authors: Wree
authors: Institute for Terrestrial and Aquatic Wildlife Research of the University of Veterinary Medicine Hannover, Werftstrasse 6, 25761 Buesum, Germany.
authors: Ursula
authors: U
authors: Siebert
authors: Institute for Biosciences, Sensory and Cognitive Ecology, University of Rostock, Albert-Einstein-Strasse 3, 18059 Rostock, Germany Marine Science Center, Am Yachthafen 3A, 18119 Rostock, Germany wolf.hanke@gmail.com.
authors: Wolf
authors: W
authors: Hanke
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D001831:Body Temperature; D001833:Body Temperature Regulation; D006197:Hair / Q000502:physiology*; D018859:Hair Follicle / Q000502:physiology; D057446:Hydrodynamics; D046049:Phoca / Q000502:physiology*; D012679:Sense Organs; D012867:Skin / Q000378:metabolism*; D013550:Swimming; D013696:Temperature; D014110:Touch; D014738:Vibrissae / Q000502:physiology*
keywords: guard hair; hydrodynamics; intermediate hair; pilosebaceous unit; skin structure; surface drag
references: J Appl Physiol. 1956 Nov;9(3):447-50
references: 13376471
references: Am J Anat. 1957 Jan;100(1):81-113
references: 13410806
references: J Morphol. 1964 Sep;115:291-303
references: 14214411
references: Am J Physiol. 1955 Aug;182(2):369-76
references: 13258817
references: Anat Rec A Discov Mol Cell Evol Biol. 2006 Jan;288(1):13-25
references: 16342212
references: Bioinspir Biomim. 2006 Jun;1(2):R17-25
references: 17671302
references: Brain Behav Evol. 2009;74(4):268-79
references: 19996585
references: J Exp Biol. 2010 Aug 1;213(Pt 15):2665-72
references: 20639428
references: J Exp Biol. 2011 Jun 1;214(Pt 11):1922-30
references: 21562180
references: Philos Trans R Soc Lond B Biol Sci. 2011 Nov 12;366(1581):3077-84
references: 21969689
references: J Exp Biol. 2014 Jan 15;217(Pt 2):252-60
references: 24431145
references: J Exp Biol. 2000 Jul;203(Pt 14):2125-31
references: 10862725
references: Science. 2001 Jul 6;293(5527):102-4
references: 11441183
references: Q Rev Biol. 1970 Mar;45(1):16-54
references: 5446769
references: Comp Biochem Physiol A Comp Physiol. 1974 Feb 1;47(2):403-10
references: 4156200
references: Comp Biochem Physiol B. 1993 Jul-Aug;105(3-4):547-52
references: 8365110
references: Somatosens Mot Res. 1997;14(3):181-8
references: 9402648
references: J Exp Biol. 1998 Nov;201(Pt 22):3023-9
references: 9787122
references: Biol Bull. 1950 Oct;99(2):225-36
references: 14791421
references: Ann N Y Acad Sci. 1951 Mar;53(3):476-92
references: 14819875
references: J Appl Physiol. 1955 Jan;7(4):355-64
references: 13233122