摘要:

This paper compares some morphological and endocrinological characteristics of diploid and triploid rainbow trout.Significant differences were found between diploid and triploid females in GSI, condition factor, gut weight, liver weight and percentage dress‐out, and between diploid and triploid males in GSI, condition factor and gut weight.Diploid females had large, well‐developed ovaries containing yolk‐filled secondary oocytes whereas the triploids had only string‐like ovaries containing nests of oogonia. No primary oocytes were present.All the diploid males produced copious quantities of milt but it was possible to express a thin, watery milt containing motile spermatozoa from only two of the 12 triploid males. Testes weights in triploids were similar to those of diploids but, while the diploid testes were packed with spermatozoa, those of the triploids consisted mainly of spermatocytes and spermatids with few spermatozoa present. Measurements of the heads of spermatozoa revealed that those from triploids were larger and had a wider size range than those from diploids.Levels of testosterone and 11‐ketotestosterone in triploid and diploid males were not significantly different. However, levels of testosterone and 17β‐oestradiol in diploid females were considerably higher than those of trip

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04886.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The mortalities of washed and unwashed rainbow trout embryos exposed to Birmingham tap water, 50% and 100% settled effluent from filter beds has been compared. Differences in the hatching success between washed and unwashed embryos in the three treatments were also compared and the effect of saprophytic microbial growths assessed. There was a significant difference in mortality between washed embryos exposed to tap water (5%) and 50% effluent (12%) and 100% effluent (12%) when dissolved oxygen levels were maintained near 100% air saturation value. Mortalities of unwashed embryos were 4%, 26%, and 26% respectively for the three treatments. Hatching success of washed embryos was similar in the three treatments but unwashed embryos were significantly affected by the effluent treatments because ofSphaerotilusgrowths.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04887.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Food resource partitioning in a community consisting of three sticklebacks (Gasterosteidae) was studied in a tidal salt‐marsh near Isle Verte, Québec in the St Lawrence Estuary. From May to July 1981 stomachs of all species were analysed. In general four prey items composed greater than 70% of the diet. There were differences in the relative proportions of prey items eaten between the sexes and species and on the different sampling dates, indicating resource partitioning. However, experiments, where allopatric and sympatric populations were established in tidal pools, did not reveal and significant shift in either type of prey or size of prey consumed, suggesting that food competition was unimportant. Microhabitat partitioning was also observed between the three species which may have served to reduce interspecific competition for fo

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04888.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Dry weights of unfixed eggs and larvae of Pacific herring,Clupea harengus pallasi, taken at six different periods during development, were compared to those of larvae stored for 10 days in fixatives varying in salinity (0, 15, 28%‰) and formalin (4, 10, 20%) concentration. In most instances there was some weight loss of the fixed specimens. In general weight loss varied inversely with salinity and formalin concentration and was greater in larvae than eggs. Weight loss was greatest in recently fertilized eggs and decreased in older eggs. Weight loss in recently hatched larvae varied from 19 to 36% depending upon the salinity and formalin concentration. Weight loss varied inversely with larval size and fixation increased weight in some large larvae. Weight change during fixation could result in an artificial inflation of the estimate of condition factors, particularly in the younger smallest larva

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04889.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

In previous studies on gastric emptying time inLimanda, data were obtained which predict that food will empty from the stomach according to:after a temperature sensitive delay. This curve gives an excellent prediction of the emptying of both artificial and natural food items given as single meals when stomachs are sampled directly. However, when two meals are given 3 h apart, emptying rate depends on whether the two meals remain separate or are allowed to mix by omitting the binding agent. In the absence of a binder, both meals are slowed so that the overall emptying rate is as predicted by the equation. When binder is present, the first meal is not delayed and the overall gastric emptying rate is increased 35%.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04890.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Copper (0.21 mgl−1) caused a decrease in whole body oxygen consumption in bluegills exposed for 32 days, but no changes occurred during days 3, 4 or 9 of copper exposure.In vitrooxygen consumption of gill and brain, were not significantly altered, whereas liverQO2, was slightly elevated which suggests that copper is acting to decrease oxygen consumption of the whole animal at a higher level of integration than these individual tissues. In fish subjected to an increase in temperature as well as sublethal copper exposure, whole body oxygen consumption was higher than controls 5 days after the temperature was increased, indicating a delay in temperature acclimation in the copper exposed fish. This difference was reflected in higherin vitrooxygen consumption in the liver and gill of these fish suggesting the metal was delaying the process of temperature acclimation by at least in part acting directly on the tissue

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04891.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The critical thermal maximum (CTM) ofEtheostoma spectabilediffered significantly among four populations whose habitats ranged from thermally constant to highly fluctuating conditions. Mean CTM of the population at the most fluctuating location was highest, populations in intermediate thermal environments were intermediate in thermal tolerance, and a population in a constant temperature spring run had thelowest CTM. The results support the view that thermal physiology can be evolutionarily labile within a species, and that changes respond to directional selection.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04892.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The effect of short‐term, experimentally‐induced stress on the branchial water permeability ofOreochromis niloticuswas studied. Both handling and thermal stress increased water permeability but apparently by different mechanisms. The enhancement of water permeability by acclimation temperatures and acute temperature changes hadQ10of 3.52 and 2.24 respectively. Environmental sodium concentration and acute hypoxia had no effect while hypercapnia and mild anaesthesia decreased water permeability. Both hypercapnia and mild anaesthesia probably elevated arterial pCO2with a concomitant reduction of metabol

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04893.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The seasonal population dynamics of adult and larvalCystidicoloides tenuissimawere studied in its definitive hosts brown trout,Salmo truttaand juvenile Atlantic salmon,S. salar, and mayfly intermediate host,Leptophlebia marginata, from the River Swincombe, Dartmoor National Park, Devon, U.K. Infective larvae were present in each mayfly generation for almost its entire duration in the steam benthos. The infection parameters (prevalence and mean intensity) and maturation in the fish indicatedC. tenuissimawas an annual parasite exhibiting a seasonal periodicity and also systematic variation with the host age. Maturation was correlated to river water temperature. Infection parameters increased from September to May, then declined in June and July and remained relatively constant for the rest of the summer. Variation in the fish infection parameters over time, site, and host species appeared to be controlled by transmission related events; the availability of infective larvae, host feeding behaviour and water temperature. The availability of infective larvae and host diet controlled the rate at which parasites were added to the parasite population, but the pattern of gains and losses was determined by a temperature dependent rejection response.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04894.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Changes in the relative proportions of protein, lipid, water and caloric contents of bluntnose minnow growing at various temperatures (15, 25, 30° C) were investigated by application of the allometry equation,y=axb. Fish grew significantly faster at 25° C (closest to optimum), more slowly at 30° C and most slowly at 15° C. Protein, as a percentage of body wet weight, tended to increase with fish size at all temperatures (b>1.000), whereas in juveniles (<0.7 g) it decreased (b<1.000). However, with the exception of the 15° C group, protein as a percentage of body dry weight, decreased in all groups (b0.9) so that estimates of body composition can be obtained from body weight for all temperat

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04895.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY