Haematological and rheological characteristics of blood in seven marine mammal species: physiological implications for diving behaviour

Abstract

The haeniatological and rheological characteristics of blood from seven marine mammal species have been examined to determine the relationship between increased haematocrit. which is correlated with the ability to increase aerobic dive limits. and blood viscosity. The species examined reflect adaptations to a variety of marine niches ranging from coastal to pelagic to iceedge environments. and exhibit a wide range of diving behaviours. Average haematocrits ranged from43–45% in bottlenose dolphins. killer whales and California sea lions to more than 60% in the deeper diving species (beluga whales and northern elephant seals). Whole blood viscosity () increased exponentially with haematocrit (= 0.96*e0‐0335*Hct). representin a two‐fold increase from 4.1 cP for killer whale blood to 8.9 cP for northern elephant seal. There was no apparent compensatory mechanism to reduce viscosity at any shear rate. The optimal haematocrit for oxygen transport was calculated to be40–50% for all species tested. The species with lower haematocrits were within optimal values for oxygen transport. while the two species with the highest haematocrits (beluga whales and northern elephant seals) were above predicted optimal oxygen transport values. On the basis of comparisons of the diving behaviour of these seven species, we suggest that marine mammal species with the greatest adaptation for increased oxygen stores via increased haematocrit have the capacity for deep, long‐duration dives, but a limited oxygen transport capacity. We predict that this compromise precludes fast sustainable swimming behaviour in these species.

Hematology and Plasma Chemistry as Indicators of Health and Ecological Status In Beluga Whales, Delphinapterus Leucas

“…Erythrocyte parameters have been correlated with diving ability (Ridgway and Johnston, 1966;Ridgway et al, 1984;Hendrick and Duffield, 1991) and used to distinguish ecological variants of the same species (Duffield et al, 1983). Environmental conditions associated with seasonal changes in habitat can influence levels of circulating thyroid hormones in beluga whales, Delphinapterus leucas (St. Aubin and Geraci, 1989a).…”

Running, swimming and diving modifies neuroprotecting globins in the mammalian brain

“…Cetaceans, pinnipeds and sea otters showed Hb concentrations greater than 0.37 g Hb 100 g brain wet wt K1 and often much higher within comparable areas of the cerebral cortex. There was also a general trend for higher Hb concentrations in larger deeper-diving animals (based on dive records in Kooyman 1989, Hedrick & Duffield 1991and Noren & Williams 2000, although two of the purportedly deepest divers (Tyack et al 2006), the Blainville's beaked whale (Mesoplodon densirostris) and Risso's dolphin (Grampus griseus), had Hb levels only 2.1 times the mean value for terrestrial species.…”

“…Here 'swimming specialist' and 'diving specialist' encompasses more than performance capability. Rather, the designations follow those of Hedrick & Duffield (1991) for marine mammals in which swimmers generally reside in shallower waters, dive for shorter periods and demonstrate faster sustained aerobic swimming activities than deep-diving specialists. The pattern of mRNA expression for neuroglobin confirmed this distinction with comparatively greater globins levels evident for fast-swimming species (figure 1b).…”

“…Among marine mammals, the variation in globin levels for swimmers and divers also reflects the haematological and rheological trade-offs for aquatic performance. Haematological characteristics of deep-diving specialists facilitate oxygen storage in the blood through increased haematocrits, which concomitantly restricts fast-sustained swimming behaviour due to elevated blood viscosity (Hedrick & Duffield 1991). Conversely, swimming specialists optimize oxygen transport through lower haematocrits but display comparatively limited diving ability.…”

“…The blue line is the least-squares curvilinear regression as described in the panel and the green horizontal line shows mean RNG and breath-hold capability for terrestrial mammals. Data for RNG levels are from figure 1b for the mammalian cerebral cortex; dive durations are from previously reported maximum values (Kooyman 1989;Hedrick & Duffield 1991;Neal 1997;Noren & Williams 2000).…”