摘要:

During the past century, the endemic range of the brook trout,Salvelinus fontinalis(Mitchill), has been extended to include western North America and the continents of Europe, Asia, Africa, and South America. Water temperature appears to be the most important single factor limiting the geographic range, but adequate precipitation and suitable spawning areas are necessary also for the establishment of self-sustaining populations. It is improbable that, with the possible exception of Asia, the present range of the brook trout will be greatly extended through further attempts at introduction.

ISSN:0706-652X    

DOI:10.1139/f69-159

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Twenty-four species are listed with synonomies according to the classification of Spencer and Wright (Treatise on invertebrate paleontology, p. U78–U107, Vol. 1, 1966). Geographical and bathymetrical distributions are also listed. The feeding habits and substrate preferences are listed wherever possible and are correlated with the distributions. A key to the 24 species is presented.

ISSN:0706-652X    

DOI:10.1139/f69-160

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The feeding behaviour of eight species of medusae was studied; total food consumed, rates of digestion, and growth rate were noted, especially inCyaneaandAurelia.Aureliaup to 5 cm diam can accept a wide range of size of food organisms obtained by filtering sea water through the curtain of tentacles during pulsation, whereas most other species find their food by random contact with the tentacles. InBougainvilliait is the dichotomously branched oral tentacles that capture the food. The apparent selectivity ofSarsiain feeding on copepods is shown to be a physical effect produced by its method of swimming.Leuckartiaracan catch and eat active organisms larger than itself. None of the medusae examined showed any reaction to artificial stimulation by a vibrating probe.The method of transfer of food from the tentacles to the mouth is closely associated with the structure of the medusa. Long trailing tentacles contract and lift food towards the mouth and if the manubrium is long it can be manipulated to pick off the food from the tentacles. If the tentacles are short the umbrella edge folds inwards towards the mouth. If there is no manubrium, as inStaurophora, the cruciform stomach can accept food at any point.Larval fish are important in the diet of most medusae and rough estimates are given of a probable consumption of 50–250 larval fish per hydromedusa, about 450–500 by eachAurelia, and in the order of 15,000 byCyanea. A conversion factor is given for food eaten by medusae of 37%, though this is based on only few data.Following the work of Horridge and Boulton (Proc. Roy. Soc. (Ser. B) 168: 413–419, 1967), who found thatSpadellacould be artificially stimulated to bite vibrating probes, similar experiments were made withSagitta elegans. Although the chaetognaths were successfully kept alive the probes produced no feeding reaction. The methods are outlined for the benefit of others wishing to continue such investigations.

ISSN:0706-652X    

DOI:10.1139/f69-161

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Seasonal changes in physical, chemical, and biological features are described in four small lakes which show different types and degrees of meromixis. There is a wide range in total dissolved solid content between lakes as well as within lakes (surface to near-bottom): Yellow, 282 (surface) to 337 (bottom); White, 6229–7918; Mahoney, 10,003–86,906; Lyons, 12,116–222,195 mg/liter, but no marked seasonal changes. In Yellow Lake meromixis is probably maintained by morphometric features of the lake basin rather than a strong chemocline; in the other lakes complete mixing is inhibited by chemical density gradients, those in Mahoney and Lyons being especially sharp.Summer, autumn, winter (under ice), and spring vertical profiles are presented for temperature, dissolved oxygen,pH, alkalinity, specific conductivity; differences within and between lakes are discussed. Other physical–chemical characteristics are given in less detail.Purple sulphur bacteria occur in three of the lakes (White, Mahoney, Lyons) and in the latter two form discrete "plates" detectable by high frequency echo sounding (confirmed by sampling). Seasonal changes in depth of the bacterial plates are considered in relation to some physical and chemical parameters. Phytoplankton, zooplankton, and benthos communities are discussed in relation to the degree of meromixis shown by the lakes.

ISSN:0706-652X    

DOI:10.1139/f69-162

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Gonadectomized female sockeye salmon (Oncorhynchus nerka) were injected intramuscularly with cortisol, estradiol, estradiol cypionate, or peanut oil for 8 weeks. The metabolic clearance rate of cortisol was determined by the single injection technique and calculated from the formula for a two pool system. The cortisol secretion rate was determined from the metabolic clearance rate and the plasma cortisol concentration.The volume of distribution of cortisol in the inner compartment (V1) and the outer compartment (V2), the metabolic clearance rate (MCR), the resting secretion rate (S), and the resting plasma cortisol concentration were all significantly higher in the estradiol-injected group than in the peanut oil-injected control group, and the plasma cortisol concentration at the end of the experiment was lower. V1, MCR, and S were also significantly higher in the estradiol cypionate-injected group. There were no significant differences between the cortisol-injected group and the peanut oil-injected control group or in the biological half life of cortisol between any groups.There were no significant changes in the red colour of the flesh or in body weight during the experiment. However, the cortisol-injected group did show the largest weight loss.

ISSN:0706-652X    

DOI:10.1139/f69-163

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Quantitative data are presented for three laboratory experiments concerning rate of gastric evacuation of pellets (fed in gelatin capsules) and pellet components. Rainbow trout,Salmo gairdneri, acclimated to a constant water temperature of 15 C were killed 12 hr after consuming an experimental meal. Subtraction of amount of dry matter remaining at autopsy from dry matter consumed yielded amount of food digested or evacuated or both, from the stomach per unit time.Meals of encapsulated pellet were evacuated from the stomach more rapidly (65.8% decrease in 12 hr) than encapsulated corn oil (42.6%), gelatin (50.8%), a combination of corn oil and gelatin (47.3%), saturated fat (28.8%), or methyl cellulose (50.3%).Groups of fish consuming five capsules equal to approximately 0.65 % of their body weight evacuated 35.9, 45.1, 64.2, 95.5, and 100% at intervals after killing from 6 to 36 hr, respectively. Similar groups consuming seven capsules equal to approximately 1.0% of their body weight evacuated 23.7, 57.9, 70.5, and 86.6% at intervals after killing from 4 to 20 hr, respectively.Ten groups of trout consuming amounts of dry matter equal to 0.24, 0.40, 0.74, 1.11, 1.31, 1.19, 1.59, 1.56, 1.91, and 2.26% of their body weight evacuated 90.7, 81.3, 64.2, 57.9, 56.6, 52.5, 53.4, 51.3, 58.7, and 50.0% in 12 hr, respectively. Gastric motility remains relatively constant once food has entered the stomach. However, when larger meals are fed a greater quantity is evacuated per unit time. This could only be accomplished by changes in volume of gastric contents pumped per peristaltic stroke or number of strokes per unit time.

ISSN:0706-652X    

DOI:10.1139/f69-164

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The effects of temperature and body weight on endogenous nitrogen excretion (ENE) rate were examined for fish acclimated at 7.2, 15.6, 23.9, and 29.4–32.2 C. Nitrogen excretion rates were very high at the highest temperature and decreased with a decrease in acclimated temperature from 29.4–32.2 C to 15.6 C. Nitrogen excretion rates were equal at 15.6 and 7.2 C. From these data, an estimate of maintenance protein for a population of bluegidl sunfish (Lepomis macrochirus) was calculated on a seasonal and yearly basis.

ISSN:0706-652X    

DOI:10.1139/f69-165

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The mineralocorticoid activity of 1α-hydroxycorticosterone, an interrenal steroid in elasmobranch fish, was determined by the in vitro toad bladder bioassay. It stimulated the transport of sodium across the toad bladder at concentrations of 10−6, 10−7, and 10−8M. The elasmobranch steroid had approximately 80% of the activity ofd-aldosterone; it was slightly less active than aldosterone and corticosterone at the lower concentrations. Protein binding alone does not seem to explain the relative potencies of the two steroids. The concentrations of 1α-hydroxycorticosterone required to stimulate sodium transport across the toad bladder are comparable with those reported in the peripheral blood plasma ofRaja radiataandR.ocellata. A seasonal variation in the number of positive responses was observed.

ISSN:0706-652X    

DOI:10.1139/f69-166

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

Antibodies to porcine adrenocorticotrophic hormone (ACTH), Synacthen (synthetic corticotrophin, Ciba), and ovine prolactin were prepared in rabbits and the antisera were tested for specificity against several pituitary hormones. The gamma-globulin fractions of the antisera were conjugated with fluorescein isothiocyanate and the labelled antibodies were "purified" by column chromatography.Fresh-frozen sections of pituitary glands of adult migratory sockeye salmon were incubated with the antibody solutions and examined with a fluorescence microscope. The resulting antigen–antibody complex could be localized by re-photographing the same or alternate sections after fixation and staining. Anti-ACTH and anti-Synacthen appeared to be bound specifically by the epsilon cells, whereas anti-prolactin reacted with the eta cells of the rostral pars distalis. Pituitary glands collected at various stations along the migratory route, including one seawater sample, showed the same reactivity. Other glands were prepared for histological examination. Microspectrophotometric analysis of cell types showed that the granule density of the ACTH cells increased gradually during the later part of migration. In the prolactin cells, no change in granulation could be detected during entrance into the river or subsequent spawning migration.

ISSN:0706-652X    

DOI:10.1139/f69-167

出版商:NRC Research Press    

年代:1969

数据来源: NRC

摘要:

The effects of aortic catheterization upon the hematology and water-electrolyte regulation of brook trout have been followed for a period of 72 hr after completion of the procedure. The data indicate the markedly traumatic character of techniques of this general type, and the need for much longer recovery periods than have generally been allowed in studies on the cardiovascular physiology of salmonids.

ISSN:0706-652X    

DOI:10.1139/f69-168

出版商:NRC Research Press    

年代:1969

数据来源: NRC