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. 2012 Aug 13;54(1):46.
doi: 10.1186/1751-0147-54-46.

Skin histology and its role in heat dissipation in three pinniped species

Wael A Khamas  1 , Hrvoje Smodlaka, Jessica Leach-Robinson, Lauren Palmer
Affiliations

Skin histology and its role in heat dissipation in three pinniped species

Wael A Khamas et al. Acta Vet Scand. .

Abstract

Background: Pinnipeds have a thick blubber layer and may have difficulty maintaining their body temperature during hot weather when on land. The skin is the main thermoregulatory conduit which emits excessive body heat.

Methods: Thorough evaluation of the skin histology in three pinniped species; the California sea lion-Zalophus californianus, the Pacific harbor seal-Phoca vitulina richardsi, and the Northern elephant seal-Mirounga angustirostris, was conducted to identify the presence, location and distribution of skin structures which contribute to thermoregulation. These structures included hair, adipose tissue, sweat glands, vasculature, and arteriovenous anastomoses (AVA). Thermal imaging was performed on live animals of the same species to correlate histological findings with thermal emission of the skin.

Results: The presence and distribution of skin structures directly relates to emissivity of the skin in all three species. Emissivity of skin in phocids (Pacific harbor and Northern elephant seals) follows a different pattern than skin in otariids (California sea lions). The flipper skin in phocids tends to be the most emissive region during hot weather and least emissive during cold weather. On the contrary in otariids, skin of the entire body has a tendency to be emissive during both hot and cold weather.

Conclusion: Heat dissipation of the skin directly relates to the presence and distribution of skin structures in all three species. Different skin thermal dissipation patterns were observed in phocid versus otariid seals. Observed thermal patterns can be used for proper understanding of optimum thermal needs of seals housed in research facilities, rescue centers and zoo exhibits.

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Figures

Figure 1
Figure 1
Diagram showing sites where skin tissue samples were collected (see Table 1).
Figure 2
Figure 2
California sea lion, hind flipper skin. Magnification 4X. Hematoxylin and eosin stain. Sweat gland (arrowhead). Picture insert from the same slide A. Magnification 20 X. Stratum basale with prominent presence of melanin pigments (arrow).
Figure 3
Figure 3
Pacific harbor seal, hind flipper dermis. Magnification 20 X. Hematoxylin and eosin stain. Sebaceous gland (S), indirect arteriovenous anastomosis, glomus body present (arrow). Picture insert from the same slide A. Magnification 100X. Indirect arteriovenous anastomosis.
Figure 4
Figure 4
Pacific harbor seal, hind flipper dermis. Magnification 20 X. Hematoxylin and eosin stain. Sebaceous gland (S), direct arteriovenous anastomosis (arrow). Picture insert from the same slide A. Magnification 100X. Direct arteriovenous anastomosis.
Figure 5
Figure 5
Pacific harbor seal, hind flipper. Indirect arteriovenous anastomosis. Magnification 100X. Hematoxylin and eosin stain. Arteriole (A), venule (V), glomus body with epitheloid cells (GB).
Figure 6
Figure 6
Pacific harbor seal, lateral head skin region, dermis. Magnification 10 X. Elastic stain. Secondary hair follicles (arrows).
Figure 7
Figure 7
Pacific harbor seal hind flipper, thermograph. Note the hind flippers appear to emit very little heat, whereas, the body (trunk) of the seal is significantly more emissive. Environmental temperature was 17°C. T max =28.4°C (Sp2), T min =16.3°C (Sp2), ΔT = 12. 2°C, T bkg = 16.1°C (Sp3).
Figure 8
Figure 8
Pacific harbor seal fore flipper and head thermograph. Note that the fore flippers appear to emit very little heat together with the muzzle, whereas; the body (trunk), neck and the rest of the head is significantly hotter. Environmental temperature was 17°C. T max =29.5°C (Sp2), T min =17.4°C (Sp1), ΔT = 12.1, T bkg =16.6°C (Sp3).
Figure 9
Figure 9
Northern elephant seal, thermograph. Wet region of the skin on right side of the body (blue) and dry skin region on the left side of the body (red). Note the clear demarcation between heat emitting dry skin region and rather cold wet skin region. Environmental temperature was 20.5-22.7°C. T max =33.4°C (Sp2), T min =24.2°C (Sp1), ΔT = 9.2°C, T bkg =24.7°C (Sp3).
Figure 10
Figure 10
Northern elephant seal, thermograph. Please note “hot” hind flippers and “cold” fore flippers. Note the thermal windows or “hot” spots on the ventral abdomen. Environmental temperature was 20.5-22.7°C. T max =31.8°C (Sp1), T min =22°C (Sp2), ΔT = 9.8°C, T bkg =18.5°C (Sp3).
Figure 11
Figure 11
California sea lion, thermograph. Note diffuse skin region that dissipate heat. Note fore and hind flipper appeared hotter. Animal shows thermoregulatory behavior. Environmental temperature was 20°C. T max =34.5°C (Sp1), T min =29.5°C (Sp2), ΔT = 5°C, T bkg =19.7°C (Sp3).
Figure 12
Figure 12
Northern elephant seal, thermograph. Note very emissive and hot hind flippers when compared with colder regions of the body. Environmental temperature was 29-32°C. T max =36.9°C (Sp1), T min =27.8°C (Sp2), ΔT = 9.1°C, T bkg =23.2°C (Sp3).
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References

    1. White FN, Odell DK. Thermoregulatory behavior of the northern elephant seal, Mirounga angustirostris. J Mammal. 1971;52:758–774. doi: 10.2307/1378924. - DOI
    1. Odell DK. Behavioral thermoregulation in the California sea lion. Behav Biol. 1974;10:231–237. doi: 10.1016/S0091-6773(74)91851-3. - DOI - PubMed
    1. Gentry RJ. Thermoregulatory behavior of eared seals. Behav. 1973;46:73–93. doi: 10.1163/156853973X00175. - DOI - PubMed
    1. Ohata CA, Miller LK. Northern fur seal thermoregulation: Thermal responses to forced activity on land. J Therm Biol. 1977;2:135–140. doi: 10.1016/0306-4565(77)90019-5. - DOI
    1. Whittow GC. Thermoregulatory behavior of the Hawaiian monk seal (Monachus schauinslandi) Pac Sci. 1978;32:47–60.

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