Stroke frequency, but not swimming speed, is related to body size in free-ranging seabirds, pinnipeds and cetaceans

It is obvious, at least qualitatively, that small animals move their locomotory apparatus faster than large animals: small insects move their wings invisibly fast, while large birds flap their wings slowly. However, quantitative observations have been difficult to obtain from free-ranging swimming animals. We surveyed the swimming behaviour of animals ranging from 0.5 kg seabirds to 30 000 kg sperm whales using animal-borne accelerometers. Dominant stroke cycle frequencies of swimming specialist seabirds and marine mammals were proportional to mass(-0.29) (R(2)= 0.99, n = 17 groups), while propulsive swimming speeds of 1-2 m s(-1) were independent of body size. This scaling relationship, obtained from breath-hold divers expected to swim optimally to conserve oxygen, does not agree with recent theoretical predictions for optimal swimming. Seabirds that use their wings for both swimming and flying stroked at a lower frequency than other swimming specialists of the same size, suggesting a morphological trade-off with wing size and stroke frequency representing a compromise. In contrast, foot-propelled diving birds such as shags had similar stroke frequencies as other swimming specialists. These results suggest that muscle characteristics may constrain swimming during cruising travel, with convergence among diving specialists in the proportions and contraction rates of propulsive muscles.     

Mechanism of fibrin-specific fibrinolysis by staphylokinase: participation of alpha 2-plasmin inhibitor

When the extent of plasminogen activation by staphylokinase (SAK) or streptokinase (SK) was measured in human plasma, SAK barely induced plasminogen activation, whereas SK activated plasminogen significantly. When the plasma was clotted with thrombin, the plasminogen activation by SAK was markedly enhanced, but that of SK was little enhanced. Similarly, in a purified system composed of plasminogen, fibrinogen and alpha 2-plasmin inhibitor (alpha 2-PI, alpha 2-antiplasmin), such a fibrin clot increased the activity of SAK significantly. However, when alpha 2-PI was removed from the reaction system, enhancement of the SAK reaction was not observed. In addition, SAK as distinct from SK, showed very little interference with the action of alpha 2-PI. Plasminogen activation by SAK is thus essentially inhibited by alpha 2-PI, but this reaction is not inhibited in fibrin clots. These results suggest that SAK forms a complex with plasminogen, which binds to fibrin and induces fibrinolysis.     

Visual information without thermal energy may induce thermoregulatory-like cardiovascular responses

Background

Human core body temperature is kept quasi-constant regardless of varying thermal environments. It is well known that physiological thermoregulatory systems are under the control of central and peripheral sensory organs that are sensitive to thermal energy. If these systems wrongly respond to non-thermal stimuli, it may disturb human homeostasis.

Methods

Fifteen participants viewed video images evoking hot or cold impressions in a thermally constant environment. Cardiovascular indices were recorded during the experiments. Correlations between the ‘hot-cold’ impression scores and cardiovascular indices were calculated.

Results

The changes of heart rate, cardiac output, and total peripheral resistance were significantly correlated with the ‘hot-cold’ impression scores, and the tendencies were similar to those in actual thermal environments corresponding to the impressions.

Conclusions

The present results suggest that visual information without any thermal energy can affect physiological thermoregulatory systems at least superficially. To avoid such ‘virtual’ environments disturbing human homeostasis, further study and more attention are needed.     

Foraging on buds and bark of mulberry trees by Japanese monkeys and their range utilization

The Japanese monkey (Macaca fuscata) winter range utilization and the effects of foraging on mulberry trees (Morus bombycis) were studied in the Shimokita Peninsula during four winter seasons. The monkeys ate mainly winter dormancy buds when they visited the mulberry tree clumps for the first time within the winter, but they ate mainly bark when they visited for the second or third times. In the areas utilized by the monkeys over the recent three years, the mulberry trees compensated for the decrease in their number of shoots by producing longer shoots with more buds against the monkey foraging. In the areas used every year for more than four years, however, the mulberry trees were unable to compensate for the foraging pressure. Thus, although the monkeys had apparently operated prudent herbivory within three years, they did not do so on a longer time-scale. They shifted their utilization ranges after having over-exploited the mulberry trees.     

Water temperature sampling by foraging Brünnich's Guillemots with bird-borne data loggers

We describe the features of waters where seabirds were feeding by sampling vertical water temperature profiles with data loggers mounted on five Brünnich's Guillemots in Svalbard, Norway. The guillemots foraged in a cold water (−0.5–0.5°C SST (sea surface temperature)) by making 1.8 dive bouts in short trips (32–257 min duration) as well as in moderate (0.5–2.0°C SST) and warm waters (2.5–4.0°C SST) by making 6.0 dive bouts during long trips (411–688 min duration). Judging from outbound flying time (15.7–24.4 min), time between dive bouts (23.9–43.3 min) and water types, the birds probably fed in fjord or coastal waters during short trips and in both coastal and offshore waters during long trips. Water temperature and diving behaviour can be simultaneously recorded by small data loggers, which therefore will provide useful information on marine features and foraging activity of top predators.     

Strouhal number for flying and swimming in rhinoceros auklets Cerorhinca monocerata

Alcids propel themselves by flapping wings in air and water that have vastly different densities. We hypothesized that alcids change wing kinematics and maintain Strouhal numbers (St = fA/U, where f is wingbeat frequency, A is the wingbeat amplitude, and U is forward speed) within a certain range, to achieve efficient locomotion during both flying and swimming. We used acceleration and GPS loggers to measure the wingbeat frequency and forward speed of free‐ranging rhinoceros auklets Cerorhinca monocerata during both flying and swimming. We also measured wingbeat amplitude from video footage taken in the wild. On average, wingbeat frequency, forward speed, and wingbeat amplitude were 8.9 Hz, 15.3 m s^?1, and 0.39 m, respectively, during flying, and 2.6 Hz, 1.3 m s^?1, and 0.18 m, respectively, during swimming. The smaller wingbeat amplitude during swimming was achieved by partially folding the wings, while maintaining the dorso‐ventral wingbeat angle. Mean St was 0.23 during flying and 0.36 during swimming. The higher St value for swimming might be related to the higher thrust force required for propulsion in water. Our results suggest that rhinoceros auklets maintain St for both flying and swimming within the range (0.2–0.4) that propulsive efficiency is known to be high and St in both flying specialists and swimming specialists are known to converge.     

Cytochrome P-450 for 11beta- and 18-hydroxylase activities of bovine adrenocortical mitochondria: one enzyme or two?

The 11beta- and 18-hydroxylase activities of a highly purified cytochrome P-450 from bovine adrenocortical mitochondria have been examined in detail with a view to determining whether the two activities are shown by a single protein or by two distinct proteins. The purified enzyme shows a single N-terminal residue (glutamic acid) and its amino acid composition is reported. Both enzyme activities decay considerably during storage at 4 degrees C for 11 days and the rates of decay are similar for the two activities. Metyrapone inhibits both activities competitively (Ki = 1.50 and 1.43 micrometer for 11beta- and 18-hydroxylase, respectively). Carbon monoxide inhibits both activities and the ratio CO:O2 for 50% inhibition is similar for the two activities (K = 1.69 and 1.53). A variety of nonspecific inhibitors produce approximately the same inhibition of both activities. Finally, antiserum produced by rabbits to the purified enzyme on double diffusion in agarose gels gives a single band with the purified enzyme. Increasing concentrations of antiserum added to the assay system produce increasing and proportionate inhibition of both activities. The evidence strongly supports earlier suggestions that the two hydroxylase activities occur in a single protein.     

Diving pattern and performance in the macaroni penguin Eudptes chrysolophus

The pattern and characteristics of diving in two female macaroni penguins Eudyptes chrysolophus was studied, during the brooding period, using continuous-recording time-depth recorders, for a total of I8 days (15 consecutive days) during which the depth, duration and timing of 4876 dives were recorded. Diving in the first 11 days was exclusively diurnal, averaging 244 dives on trips lasting 12 hours. Near the end of the brooding period trips were longer and included diving at night. About half of all trips (except those involving continuous night-time diving) was spent in diving and dive rate averaged 14–25 dives per hour (42 per hour at night). The duration of day time dives varied between trips, and averaged 1.4–1.7 min, with a subsequent surface interval of 0.5–0.9 min. Dive duration was significantly directly related to depth, the latter accounting for 53% of the variation. The average depths of daytime dives were 20–35 m (maximum depth 11 5 m). Dives at night were shorter (average duration 0.9 min) and much shallower (maximum 11 m); depth accounted for only 6% of the variation in duration. Estimates of potential prey capture rates (3–5 krill per dive; one krill every 17–20 s) are made. Daily weight changes in chicks were directly related to number of dives, but not to foraging trip duration nor time spent diving. Of the other species at the same site which live by diving to catch krill, gentoo penguins forage exclusively diurnally, making longer. deeper dives; Antarctic fur seals, which dive to similar depths as macaroni penguins, do so mainly at night.     

Incubation capacity limits maximum clutch size in black-tailed gulls Larus crassirostris

Factors determining clutch size of birds have long been the central issue in studies in life histories. It is assumed that the configuration of brood patches could limit the maximum clutch size. To test this hypothesis we manipulated clutch sizes and measured egg temperature as well as reproductive consequences in black-tailed gulls Larus crassirostris , which usually lay two egg clutches and have three brood patches. Mean egg temperature in 4-egg clutches (32.6±1.0°C) was significantly lower than in 2-egg (34.6±0.4°C) and 3-egg clutches (34.1±0.4°C), because egg temperature of the coolest egg within a 4-egg clutch was often substantially lower than the other three eggs. The proportion of eggs hatching from 4-egg clutches (11.6%) was lower than those of 2-egg (49.1%) and 3-egg clutches (52.0%). Four-egg clutches had longer incubation periods (29.6±1.3 day) than 2-egg (28.1±1.7 day) and 3-egg clutches (28.0 ±1.3 day). The results indicate that incubation capacity, which may be determined by the configuration of brood patches, limits the maximum clutch size in black tailed gulls, but not the actual clutch size typically laid.     

Biological characteristics of euphausiids preyed upon by Adélie penguins in relation to sea-ice conditions in Lützow-Holm Bay,Antarctica

We examined the biological characteristics of euphausiids found in the stomachs of Adélie penguins in relation to sea-ice conditions in Lützow-Holm Bay over three seasons. Euphausiids, especially Euphausia superba, proved to be a staple food for Adélie penguins irrespective of the ice condition. Body length and maturity-stage compositions of euphausiids were different among seasons, probably reflecting sea-ice condition in summer. The mean body length decreased and maturity regressed during each season in E. superba, which was partly attributable to the selective feeding on large, mature female krill by Adélie penguins. The 1995/1996 year class of E. superba, which was spawned when the sea ice was most developed, was strong and conspicuous in the 1996/1997 and 1997/1998 seasons. This vigor indicates that sea ice provided females with good spawning conditions and larvae with good growth and survival rates.