摘要:

Fine structural characteristics of the columnar mucus cells lining the surface and pits of the gastric mucosa, oxyntic cells lining the glands and the gastric endocrine cells were studied. The surface mucus cells, in addition to their primary involvement in production of mucus, showed structural adaptations. Release of the mucus vesicles was achieved by exocytosis. Transition from pit gland cells was abrupt since no mucus neck cells were observed. The oxyntic cells possessed apical and basal microvillous processes, a well developed tubulovesicular system, zymogen granules and extensive RER associated with many large mitochondria. When stimulated by distension of the stomach, the apical cytoplasm was converted into a labyrinth of cytoplasmic processes, while annular lamellae, each of which showed a short peripheral linear density appeared in the basal cytoplasm. The endocrine cells showed apical modifications as microvilli, cilia and reduced glycocalyx covering. Three types were distinguished on the basis of their granular morphology.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03828.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Grass carp,Ctenopharyngodon idella,>300 mmt.l.were stocked in Lake Baldwin, Florida during 1978 (24 fish ha−1) to evaluate their effectiveness for hydrilla control. Hydrilla,Hydrilla verticillata, was nearly eradicated from Lake Baldwin 2 years after stocking. Control was effective with 130 kg grass carp ha−1of hydrilla and control was definite when biomass exceeded 185 kg ha−1of hydrilla. Grass carp growth was rapid during the first two years as fish reached 9.17 kg by June 1980. Grass carp>6 kg consumed 25–28% of their body weight of hydrilla per day. The use of grass carp for vegetation management is di

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03829.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

An experiment to induce anadromy in a population of wild brook trout,Salvelinus fontinalis, was conducted near Sept‐Iles, Quebec, in 1978–1979. Brook trout were captured from the Matamek River, tagged and transported to the Matamek River estuary during late spring and early summer, and allowed free movement between an impassable waterfall 0.7 km upstream and the sea. Fish were recaptured in autumn as they returned to fresh water. Over two years, 34.0% of the released fish were recaptured. Best returns were in the 2+ and 3+ age classes with 38.0 and 62.1% recaptured, respectively. Straying of transplanted fish appeared to be<1%. All age classes included sea run brook trout (sea trout) but the largest percentages of sea trout occurred in older fish. Growth was better in sea trout than in fish which did not develop anadromy, presumably a function of an increased food supply at sea. Severe tagging effects stunted growth and probably suppressed anadromy, especially among younger fish. Sexual characteristics of recaptured fish indicated suppressed maturation of gonads in sea trout compared to fish remaining in fresh water and there was a shift to a larger percentage of females in the sea trout. Comparisons between our results and data on other anadromousSalvelinusspecies underscore the potential for sea‐ranching of trout and char as a moderate effort, high yield aquaculture tech

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03830.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Distribution ratios (intracellular/extracellular concentration) of α‐amino isobutyric acid (AIB) and activities of the transaminases of alanine (Ala AT), aspartate (Asp AT), leucine (Leu AT) and glutamate dehydrogenase (GDH) were determined in tissues of freshly caught plaice,Pleuronectes platessa, deprived of food for three months. Liver, red muscle and white muscle demonstrated increased distribution ratios for AIB, while the ratios decreased in kidney and gill with deprivation. Values of the distribution ratio were below 1.0 only in white muscle, with kidney and liver having the highest absolute values. Transaminase activities generally rose with deprivation in all tissues, although the absolute increases were greatest in liver and for the two enzymes Ala AT and GDH. These data indicate that with food deprivation, the role of the liver in amino acid metabolism is maintained and slightly enhanced, while that of the kidney is reduced. Both muscle types (red and white) showed increased water content implicating protein mobilization which could enhance the availability of amino acids for liver gluconeogenesis and metabolite sparing in other tissues during conditions of depleti

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03831.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

In this study some comparative observations on the growth‐rate and year‐class strength of bream,Abramis brama, in three Shropshire‐Cheshire meres are given. All populations are exposed to variable recruitment. The occurrence of four strong year‐classes (1959, 1966, 1969,1973) suggests that climate is an important factor influencing spawning success. Water temperatures ≥16°C in July and August may be particularly important. All other intervening year‐classes are absent. The growth‐rate of bream in Tatton Mere and Ellesmere Mere is good (L∞= 541–561 mm) but comparatively poor (L∞= 448 mm) in Cole Mere. The significance of population density, food supply and parasitic infestation byLigula inte

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03832.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The effects of temperature, photoperiod and powdered carp pituitary on ovarian development (measured by change in diameter of intraovarian eggs and gonadosomatic index), ovulation and ovarian ascorbic acid have been studied in crucian carp in winter. Short photoperiods stimulated ovarian development but long photoperiods were inhibitory. Photoperiod seemed to exert this effect by altering the release of pituitary gonadotropin. Temperature affected ovarian development independently of photoperiod. High temperatures were stimulatory and overcame the negative effect of a long photoperiod. The results suggested that temperature acts at the level of the gonad rather than the pituitary. On the basis of these findings a hypothesis is suggested to explain gonadal cycles in cyprinids and similarities to previous findings in other fish groups are discussed.Levels of ovarian ascorbic acid varied according to treatments. Ovulation was associated with a decreased level. The results suggested that this vitamin aids biosynthesis of sex steroids in a similar fashion to that observed in higher animals. The results also demonstrated that measurement of gonadal ascorbic acid can provide a useful indication of physiological events at the level of the gonad.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03833.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Multiple regression analyses were conducted to relate rate of toxic action, body weight and concentration for fry, male and female populations ofLebistes reticulatusexposed to copper solutions. For each of these three populations, copper susceptibility decreased as body weight increased. On the basis of the rate of toxic action adjusted with the size factor, the copper susceptibility differed significantly among the fry, male and female populations at the ratios of 2.20:1.55:1.00. When the size factor was not included in calculation, the rate of toxic action or median survival time did not show such a difference between the males and females.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03834.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Eggs ofOryzius latipesin the blastula stage were exposed to M/100 artificial sea water which contained cadmium at the concentrations of 0.1, 1.0, 10.0, 20.0 or 50.0 mg 1−1. The 96 h TL50, value for cadmium was estimated to be 20 5 mg 1−1. When the eggs were incubated for 24 h in the M/100 sea water with 10.0 mg Cd 1−1and then rinsed in glycine buffer solution (pH; 2.0), the cadmium content of the egg decreased markedly. Cadmium levels were determined in parts of the embryonic body, the chorion and the yolk sac. The most cadmium was detected in the chorion (94.6%). Prolonged cadmium exposure revealed that most of the cadmium was absorbed by the chorion and little was detected in the embryonic body and the yol

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03835.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The biology of the small offshore goby,Pomatoschistus norvegicus(Collett), was studied on the west coast of Scotland over a period of 19 months. Catches were highest in April‐June and lowest in August‐September. Virtually all growth takes place in the first two summers, very little in those fish surviving to a third summer. The fish mature after their first winter and the breeding season lasts from March‐July. Fecundity is linearly related to standard length and varies from approximately 1000–4000 eggs. Approximately 75% of fish survive their first breeding season but all die after their second. Males live slightly longer than females. The diet consists mainly of amphipods and small caridean decapods. The life history ofthe species is compared with other members ofth

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03836.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY