Arnoldus Schytte Blix

Diving behaviour of hooded seals (Cystophora cristata) in the Greenland and Norwegian Seas

Abstract Satellite-linked dive recorders were used to collect data on depths and durations of ∼120,000 dives by 16 hooded seals (Cystophora cristata). Following tagging after moult (four males, eight females) and breeding (four females) off east Greenland, seals dispersed widely in the northeast Atlantic during 172 ± 97 days (mean satellite-linked dive recorder lifetime ± SD). Meso/bathypelagic dives of 5- to 25-min duration to 100–600 m dominated (75%), but some very deep (≥1016 m) and long (>52 min) dives occurred. Diving in open ocean was continuous, with an estimated 90.7±0.8% (mean±SE) of time spent submerged. The proportion of time spent submerged was similar during night and day, but dives during the day were generally deeper and longer (P < 0.05) than during the night. Also, dives in winter were deeper and longer than in summer. Published data on the distribution of likely prey suggest that Greenland halibut (Reinhardtius hippoglossoides), redfish (Sebastes spp.), polar cod (Boreogadus saida), herring (Clupea harengus), squid (Gonatus fabricii) and blue whiting (Micromesistius poutassou) are important prey of hooded seals.

Annual distribution of hooded seals (Cystophora cristata) in the Greenland and Norwegian Seas

Nineteen hooded seals (Cystophora cristata) were tagged with satellite-linked platform terminal transmitters (PTT) on the sea ice near Jan Mayen. Fifteen were instrumented after completion of the mouly in July 1992 (five males, ten females, at 71°N, 12°W), and four during breeding in March 1993 (four females, at 69°N, 20°W). Sixteen of the seals were tagged with Satellite-Linked Time-Depth-Recorders (SLTDR), yielding location, dive depth and dive duration data. The average (±SD) longevity of all PTTs was 199±84 days (n=19; range: 43–340 days), and they yielded 12,834 location fixes. Between tagging in July 1992 and pupping in March 1993, two seals remained in or near the ice off the east coast of Greenland for most of the tracking period. However, most of the seals made one or several trips away from the ice edge, mostly to distant waters. These excursions had an average (±SD) duration of 47±22 days (n=46; range: 4–99 days). Eight seals travelled to waters off the Faeroe Islands, three to the continental shelf break south of Bear Island, and three to the Irminger Sea southwest of Iceland. Eleven seals were tracked in the period between breeding (March/April) and moulting (July). Several of these spent extended periods at sea west of the British Isles, or in the Norwegian Sea.

Distribution and diving behaviour of crabeater seals (Lobodon carcinophagus) off Queen Maud Land

Eight crabeater seals (Lobodon carcinophagus) (three females, five males), ranging in body mass between 125 and 220 kg, were captured off Queen Maud Land (70–72°S, 7–16°W) during the last week of February, just after moulting, and tagged with Argos satellite-linked dive recorders to provide data on location and diving depth and duration. During the first few weeks of March the seals were moving in the pack ice along the continental shelf edge, close to the coast of Queen Maud Land. In April and May, when the pack ice extended northwards, most of the seals moved north, one reaching 63°S in late May. In the first half of June the two remaining seals turned south and moved back deep into the pack ice. The seals made about 150 dives per day each throughout the study period. Ninety percent of these were made to depths of less than 52 m. Individual maximum diving depths varied between 288 and 528 m. In March the seals were most active at night, when the dive depth was shallower than during the day. In April and May the seals were more active during day-time, with an absence of any diurnal change in divng depth. These results support the notion that crabeater seals predominantly feed on krill in Antarctic pack ice, even when winter returns to the waters off Queen Maud Land.

When the brain goes diving: glial oxidative metabolism may confer hypoxia tolerance to the seal brain.

Deep diving mammals have developed strategies to cope with limited oxygen availability when submerged. These adaptations are associated with an increased neuronal hypoxia tolerance. Brain neurons of the hooded seal Cystophora cristata remain much longer active in hypoxic conditions than those of mice. To understand the cellular basis of neuronal hypoxia tolerance, we studied neuroglobin and cytochrome c in C. cristata brain. Neuroglobin, a respiratory protein typically found in vertebrate neurons, displays three unique amino acid substitutions in hooded seal. However, these substitutions unlikely contribute to a modulation of O(2) affinity. Moreover, there is no significant difference in total neuroglobin protein levels in mouse, rat and seal brains. However, in terrestrial mammals neuroglobin resided exclusively in neurons, whereas in seals neuroglobin is mainly located in astrocytes. This unusual localization of neuroglobin is accompanied by a shift in the distribution of cytochrome c. In seals, this marker for oxidative metabolism is mainly localized in astrocytes, whereas in terrestrial mammals it is essentially found in neurons. Our results indicate that in seals aerobic ATP production depends significantly on astrocytes, while neurons rely less on aerobic energy metabolism. This adaptation may imbue seal neurons with an increased tolerance to hypoxia and potentially also to reactive oxygen species, and may explain in part the ability of deep diving mammals to sustain neuronal activity during prolonged dives.

Effects of improved nutrition in pregnant reindeer on milk quality, calf birth weight, growth, and mortality

A group of 35 pregnant reindeer (Rangifcr tarandus) was divided into two groups in mid-February. Until calving in May one of the groups (L) received lichen ad lib., while the other group (IN) received an improved diet, rich in protein and minerals. After calving both groups received the same improved diet. In both groups it was distinguished between young ( 3 years) animals. At the start of the experiment the body weight of L-young animals was 58.5 ± 4.6 kg, IN-young 56.2 ± 2.8 kg, L-old 70.3 ± 6.0 kg and IN-old 68.2 ± 4.8 kg. At calving the weights of the same animals were 55.9 ± 4.5 kg (L-young), 68.1 ± 2.5 (IN-young), 70.0 ± 6.9 kg (L-old) and 81.6 ± 6.8 kg (IN-old). Birth weight of IN-young calves was 4.5 ± 0.7 kg and of L-young calves 3.7 ± 0.5 kg. Birth weight of IN-old calves was 5.7 ± 0.8 kg and of L-old calves 4.4 ± 0.6 kg. The birth weight of the calves in all groups was correlated to the weight of the female just prior to calving. Growth rates in all but the IN-old group were not different, the IN-old group showing a significantly higher growth rate than the other groups. In mid-September, however, the average body weight for the calves from the L and IN-groups did not differ significantly. Neither chemical composition nor total energy content of the milk differed significantly between the groups. Total mortality in the L-group was 28% as compared to 7% in the IN-group. Two females in the IN-old group had not given birth at the end of the experimental period. Virkningen av bedret ernaering til drektige reinsimler pa melkekvalitet, kalvenes fodselsvekt, vekst og dodelighet. Abstract in Norwegian / Sammendrag: En flokk pa 35 drektige reinsimler (Rangifer tarandus) ble delt i to grupper i midten av februar. Frem til kalving i mai ble den ene gruppen gitt lav ad lib. (L-gruppe), mens den andre gruppen ble tilleggsforet med 2 kg RF - 71/dag (IN-gruppe). Etter kalving ble begge gruppene gitt 2 kg RF - 71/dag. Innen begge gruppene ble det skilt mellom unge ( 3 ar) simler. Ved forsokets start var kroppsvekten for unge simler ca. 57 kg, og for gamle simler ca. 69 kg, i begge ernaeringsgruppene. Ved kalving var kroppsvekten for unge simler 55.9 ± 4.5 kg (L-gruppe), og 68.1 ± 2.5 kg (IN-gruppe) mens kroppsvekten for gamle simler var 70.0 ± 6.9 kg (L-gruppe) og 81.6 ± 6.8 kg (IN-gruppe). Fodselsvekt for kalver etter IN-unge simler var 4.5 ± 0.7 kg, og 3.7 ± 0.5 kg for kalver etter L-unge simler. De tilsvarende fodselsvektene for kalver etter gamle simler var 5.7 ± 0.8 kg (IN-gruppe) og 4.4 ± 0.6 kg (L-gruppe). Fodselsvektene var korrelert til simlenes kroppsvekt like for kalving. Kalveveksten i de forste tre ukene etter fodselen var signifikant hoyere for kalver etter IN-gamle simler, sammenlignet med kalveveksten i de ovrige tre gruppene, som ikke var innbyrdes signifikant forskjellige. I midten av september var det ingen signifikante forskjeller i kalvenes kroppsvekt gruppene imellom. Det var ingen signifikante forskjeller hverken i totalt energiinnhold eller i kjemisk sammensetning av melken fra simlene i de to ernaeringsgruppene. Total dodelighet for kalver i L-gruppen var 28% mot 7% i IN-gruppen i lopet av de tre forste ukene etter fodselen. To av de gamle simlene i IN-gruppen hadde ikke kalvet ved forsokets slutt. Kantavien porovaatimien parannetun ravinnon vaikutus maidonlaatuun, vasojen syntymapainoon, kasvuun ja kuolleisuuteen. Abstract in Finnish / Yhteenveto: 35 kantavan porovaatimen (Rangifer tarandus) lauma jaettiin kahteen ryhmaan helmikuun puolivalissa. Vasomiseen saakka toukokuussa annettiin toiselle ryhmalle jakalaa ad. Ub. (L-ryhma), kun taas toinen ryhma sai lisaravintona 2 kg RF-71 rehua paivassa (IN-ryhma). Vasomisen jalkeen annettiin molemmille ryhmille 2 kg RF-71 rehua paivassa. Molemmissa ryhmissa erotettiin nuoret ( 3-vuotiaat) vaatimet toisistaan. Tutkimuksen alkuvaiheessa oli nuorten vaatimien ruumiinpaino n.57 kg, ja vanhojen vaatimien n.69 kg, molemmissa ravintoryhmissa. Vasomisen aikana oli nuorten vaatimien ruumiinpaino 55,9 ± 4,5 kg (L-ryhma), ja 68,1 ± 2,5 kg (IN-ryhma), kun taas vanhojen vaatimien ruumiinpaino oli 70,0 ± 6,9 kg (L-ryhma) ja 81,6 ± 6,8 kg (IN-ryhma). Vasojen syntymapaino IN-nuorten vaatimien ryhmassa oli 4,5 ± 0,7 kg, ja 3,7 ± 0,5 kg L-nuorten vaatimien ryhmassa. Vastaavat syntymapainot vanhojen vaatimien vasoilla olivat 5,7 ± 0,8 kg (IN-ryhma) ja 4,4 ± 0,6 kg (L-ryhma). Syntymapainot olivat vastaavuussuhteessa vaatimien ruumiinpainoon vahaa ennen vasomista. IN-vanhojen vaatimien vasojen kasvu ensimmaisten kolmen viikon aikana syntyman jalkeen oli merkittavasti korkeampi, verrattuna niiden kolmen muun ryhman vasankasvuun, jotka eivat olleet keskenaan merkittavan erilaisia. Vasojen ruumiinpainossa ryhmien kesken ei ollut mitaan merkittavia eroavaisuuksia syyskuun puolivalissa. Naiden kahden ravintoryhman vaatimien maidossa ei ollut mitaan merkittavia eroja kokonaisuudessa ravinnon sisaltoon eika kemialliseen kokoonpanoon nahden. Vasojen kokonaiskuolleisuus L-ryhmassa oli 28% ja IN-ryhmassa 7% kolmena ensimmaisena viikkona syntyman jalkeen. Kaksi vanhaa vaadinta IN-ryhmassa ei ollut vasonut tutkimuksen lopussa.

Remarkable neuronal hypoxia tolerance in the deep-diving adult hooded seal (Cystophora cristata)

Seals cope with regular exposure to diving hypoxia by storing oxygen in blood and skeletal muscles and by limiting the distribution of blood-borne oxygen to all but the most hypoxia vulnerable tissues (brain, heart), through dramatic cardiovascular adjustments. Still, arterial oxygen tension of freely diving seals regularly drops to levels that would be fatal to most non-diving mammals. Some cerebral protection is offered through diving-induced brain cooling and, possibly, enhanced oxygen delivery due to a particularly high brain capillary density. Here we test the hypothesis that seal neurons are in addition also intrinsically hypoxia tolerant. For this purpose we compared neuronal hypoxic responses in adult hooded seals and mice using intracellular recordings from the pyramidal layer of isolated visual cortex slices. Neurons from both species maintained normoxic membrane potentials of -60 to -70 mV, which in seals increased by only 13.4 +/- 19.2 mV (n = 7) during the first 10 min of severe hypoxia (oxygen content of saline perfusate reduced from approximately 75 to approximately 5%), while the corresponding depolarization of mouse neurons was significantly larger (65.0 +/- 44.9 mV; n = 14; p = 0.006). Mouse neurons moreover lost the ability to discharge after 5 +/- 2 min in hypoxia, while seal neurons continued on average for 19 +/- 10 min, in one case for a full hour. These results show that seal neocortical neurons exhibit a remarkable intrinsic hypoxia tolerance, which may partly explain why seals can dive for more than 1 h and stay alert without suffering from detrimental effects of hypoxia.

Arctic animals and their adaptations to life on the edge

Conceived in order to provide students and those interested in the Arctic with a comprehensive overview of Arctic ecosystems, processes and animal adaptations to life in the cold, this textbook of 10 chapters draws on the 30 year research experience of Dr Arnoldus Blix, an accomplished Arctic physiologist. Topics covered by the book range from the climate, oceanography and ecology of the Arctic region to the distribution, behaviour and life cycles of marine and terrestrial invertebrates and through to higher resident marine and terrestrial predators. The textbook begins with a poetic definition of the Arctic— describing it as the region under Arctos, the polar star— and thereby setting the scene for the rest of the text, which combines concise descriptions of Arctic processes and species distributions interspersed with accounts of the author’s research experience and almost 200 illustrations.

Thermal conductivity of minke whale blubber

Abstract 1. 1. Four blubber samples were taken from each of nine minke whales (Balaenoptera acutorostrata) caught in the north-east Atlantic between May and September, and thermal conductivity, blubber thickness, per cent lipid and per cent water content were determined. 2. 2. A positive correlation between blubber conductivity and water content, and a negative correlation between conductivity and lipid content, were found, while the relationship between blubber thickness and thermal conductivity was not significant. 3. 3. Thermal conductivity, blubber thickness and total thermal resistance of the blubber layer varied significantly between different regions. 4. 4. The average weighted blubber conductivity was 0.25 (SD = 0.03) Wm−1K−1 (n = 9), which implies that the heat loss rates of baleen whales have been underestimated in a number of previously published studies.

A new device for measurement of the thermal conductivity of fur and blubber

Abstract 1. 1. A new and simple device for measurements of thermal conductivity of fur and blubber is described. 2. 2. The device measures temperature differences across the sample and across a polyethylene plate with known conductivity which is placed in series with the sample. 3. 3. The conductivity of the polyethylene was determined from the steady state temperature difference and heat flux through the wall of a polyethylene pipe with a central heat source. 4. 4. The accuracy of the device is ±4.0%. 5. 5. The thermal conductivity of harp seal (Phoca groenlandica) and minke whale (Balaenoptera acutorostrata) blubber, as determined by use of this device, is very close to previously reported values.

Survival strategies in arctic ungulates

Arctic ungulates usually neither freeze nor starve to death despite the rigours of winter. Physiological adaptations enable them to survive and reproduce despite long periods of intense cold and potential undernutrition. Heat conservation is achieved by excellent insulation combined with nasal heat exchange. Seasonal variation in fasting metabolic rate has been reported in several temperate and sub-arctic species of ungulates and seems to occur in muskoxen. Surprisingly, there is no evidence for this in reindeer. Both reindeer and caribou normally maintain low levels of locomotor activity in winter. Light foot loads are important for reducing energy expenditure while walking over snow. The significance and control of selective cooling of the brain during hard exercise (e.g. escape from predators) is discussed. Like other cervids, reindeer and caribou display a pronounced seasonal cycle of appetite and growth which seems to have an intrinsic basis. This has two consequences. First, the animals evidently survive perfectly well despite enduring negative energy balance for long periods. Second, loss of weight in winter is not necessarily evidence of undernutrition. The main role of fat reserves, especially in males, may be to enhance reproductive success. The principal role of fat reserves in winter appears to be to provide a supplement to, rather than a substitute for, poor quality winter forage. Fat also provides an insurance against death during periods of acute starvation.