Johan B. Steen

The respiratory function of teleostean gills

Abstract 1. 1. Histological methods revealed that blood entering the gill filament may reach the efferent artery (1) through the lamellae, (2) through a central, lymphatic compartment and (3) directly from the afferent to efferent artery at the tip of the filament. 2. 2. In gill filaments immersed in saline, blood was shown to pass through the lamellae in the presence of adrenaline, and through the other vascular paths in the presence of acetylcholine. 3. 3. Inravascular injection of adrenaline caused a marked increase in the degree of blood oxygenation in the eel. 4. 4. The arterial oxygen tension was much higher in active than in resting eels, whereas the oxygen tension of efferent water was higher in resting than in active eels. The average difference in oxygen tension between blood and water was the same in resting and active eels. 5. 5. The expected oxygen uptake, as calculated from the anatomical dimensions of the gills and the measured blood-to-water oxygen tension difference, corresponded to the oxygen uptake which has been measured for active eels. 6. 6. It is concluded that the vascular arrangement of the gills of the eel permits variations in blood oxygenation, and thereby in oxygen uptake, by directing a varying proportion of the blood to circulate the respiratory lamellae while the rest is shunted through the alternate non-respiratory path of the central cavity. 7. 7. A double, intercommunicating vascular system, more or less similar to that of the eel, was demonstrated in all the other ten teleost species investigated, and we suggestthat it is common to all teleosts.

Physiological mechanisms for aerial respiration in the eel

Abstract 1. 1. The oxygen uptake of eels in air is about half of that in water. During the first hour of air exposure oxygen removal from the swimbladder may be almost equal to the oxygen uptake from the air. 2. 2. The eel receives 85–90 per cent of its oxygen uptake in water through the gills. In air about a third of the total oxygen uptake occurs via the gills. 3. 3. During air exposure eels keep the gill cavity inflated with air which is slowly depleted in oxygen and renewed at intervals. 4. 4. Eels develop pronounced bradycardia upon air exposure. 5. 5. After 20 hr in air at 15°C eels have accumulated a substantial oxygen debt and the concentration of H + -ions and lactic acid in their blood is elevated for about 1 hr after return of the animal to water. At 7°C these reactions are almost absent. 6. 6. In general the eel reacts upon air exposure as do air-breathing divers upon water immersion.

The permeability of the swimbladder

Abstract 1. 1. The O 2 and CO 2 permeability of the eel swimbladder is about one-tenth of values reported for connective tissue. 2. 2. The impermeability resides principally in the silvery outer layer of the swimbladder. 3. 3. The silvery layer contains many needle-shaped crystals. 4. 4. Guanine accounts for about 13 per cent of the dry weight of the silvery layer.

Permeabilty of the shell and shell membraes of hens' eggs during development

Abstract The O 2 and CO 2 permeabilities of the shell plus shell membranes of newly laid eggs are not sufficient to permit the gas exchange which occurs in later development. We have found that the C 2 and CO 2 permeabilities increase with incubation in fertilized eggs, but not in unfertilized ones, to levels compatible with the embryos survival. Drying the shell membranes greatly increases their permeability. We have found that water content of the shell membranes of fertilized eggs decreases from 70% to about 40% in 17 days of incubation, while the membranes of unfertilized eggs lose very little of their water content. Preliminary results suggest that an increased colloid osmotic effect of the albumen plays a role in loss of water by the membranes of fertilized eggs. The ratio of CO 2 to O 2 permeability suggests that permeation occurs principally via gas-filled channels even in newly laid eggs. From measurements of hydraulic conductivity, hemoglobin permeability, and reflection coefficient for hemoglobin, we have calculated equivalent pore radii for the inner and outer shell membranes of 126 A and 0.53 μ, respectively, and fractional pore areas of 0.175 and 0.0011, respectively.

The gills of two species of haemoglobin-free fishes compared to those of other teleosts--with a note on severe anaemia in an eel.

Abstract 1. 1. The gills of two species of congenitally haemoglobin-free fishes CHaenocephalus aceratus and Champsocephalus esox (icefishes) and twelve species of normal fishes have been investigated by anatomical and histological techniques. 2. 2. Active fishes were found to have a large gill area composed of a large number of lamellae with a very thin epithelium separating blood from water. More sluggish species had a smaller gill area, more coarse gill structure and a longer diffusion distance. 3. 3. C. aceratus had unusually coarse gills with few thick lamellae and a long distance between blood and water. C. esox had gills with dimensions similar to those of normal fishes. The gill area of C. aceratus was normal, that of C. esox relatively large when compared to normal fishes of similar size. 4. 4. We have thus found no parameter in the gill structure which parallels lack of hemoglobin. We suppose that if these fishes have oxygen uptake comparable to that of normal fishes, they must have an increased blood circulation of the lamellae.

Breeding biology of the Svalbard Rock Ptarmigan Lagopus mutus hyperboreus

The breeding biology of Svalbard Rock Ptarmigan was studied by recording moult, body weight, egg laying dates, clutch size, hatching success, brood behaviour and chick growth in 1981 and 1982. Adult hens were heavier and moulted and laid eggs earlier than first year hens. Hens in good condition laid eggs earlier and produced larger clutches with higher hatching success than hens in poor condition. The body weight of hens decreased about 130 g during incubation. Hens with chicks lost weight during the first weeks after hatching, whereas hens without chicks gained weight. The physical condition of hens prior to breeding seemed to be the most important factor in determining chick production.

Thermoregulatory responses to egg cooling in incubating bantam hens

SummaryO2 consumption, electromyographic activity (EMG), heart rate (HR), cloacal temperature (Tb) and broodpatch temperature (Tsb) were measured in bantam hens incubating eggs of different temperatures (Te). For comparison, the metabolic response to low ambient temperature (Ta) was measured in non-incubating hens.O2 consumption increased nearly linearly with decreasingTe down to 30°C. At this temperature O2 consumption was about 3.5 x the resting level. Below 30°C O2 consumption increased non-linearly, and reached 4.6 x the resting consumption at 15°C. Eggs of 10 and 0°C gave no further increase. Pectoral muscle EMG and HR also increased in response to egg cooling. The onset of egg cooling was associated with a decrease inTb andTsb. Hens exposed to lowTa showed a lower critical temperature of about 24°C.It is concluded that heat loss from the brood-patch during incubation of cold eggs is compensated by shivering thermogenesis. AtTe below 15°C heat production is at a maximum level, corresponding to the expected O2 consumption at exposure to an ambient temperature of −65°C.

Behaviour and social structure in Svalbard Rock Ptarmigan Lagopus mutus hyperboreus

The behaviour and social structure of Svalbard Rock Ptarmigan were studied by direct observation, trapping, weighing, marking, and telemetry from August 1980 to August 1982 on five breeding areas around Ny-Alesund. The first cocks arrived there in late March. Until mid April territorial cocks were solitary and hostile towards both cocks and hens. Pairs formed from late April. Mate guarding was conspicuous. Pairs were monogamous until hens started to incubate. Later, promiscuity was common. Territorial cocks banded in 1981 were all found on the same territory in 1982. Some hens changed cock and territory but always within the same breeding area. Birds banded as chicks were never recovered as breeding birds on the area where they were banded.

Social organization and territorial behaviour in a Willow Ptarmigan population

Willow Ptarmigan in Norway showed the same postures and calls as Red Grouse. Territorial behaviour occurred at dusk and dawn from September to December and from April to June. During the day cocks did not defend territories. This daily rythm was apparently acquired rather than genetic, since captive birds did not show it. Whereas Red Grouse at high density display at all times of day, Willow Ptarmigan seldom do so, regardless of density. Cocks showed higher site tenacity than hens. There was no tendency for young cocks to establish territory close to the territory of their parents.

Thermoregulatory importance of the beaver's tail

Abstract 1. 1. When totally surrounded by air, the beaver is able to maintain a normal body temperature at ambient temperatures below 20°C. Above this temperature it becomes hyperthermic. 2. 2. If the air-surrounded beaver is allowed to keep its naked tail in cool water the animals body temperature is maintained at a normal level also at an ambient air temperature of 25°C. In this situation heat loss from the tail to water amounts to about 20 per cent of the total heat production. 3. 3. It is concluded that the beavers tail, like poorly insulated body parts of many other animals, has an important secondary function as an organ for controlled heat dissipation.