摘要:

Female American eels,Anguilla rostrata(LeSueur), were artificially matured with injections of salmon and carp pituitary and human chorionic gonadotropin.In vivoovulation was induced with 4‐pregnene‐17α,20β‐diol‐3‐one and eggs were spontaneously released. Eggs were fertilizedin vitroand survived to the gastrula stage. Males were matured with injections of human chorionic gonadotropin. They were attracted by the sight and odour of maturing and mature females. Ovulated females released a sex pheromone which was especially attractive to mature males and triggered the relea

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04874.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Morphological and karyological comparisons of 25–28 hybrid grass carp from each of 3 year‐classes (1979–1981) indicated that diploid fish resulted during 1979 (82.1%) and 1980 (76.0%) the others being triploid. All of the fish tested from the 1981 year‐class were triploid. Most triploid fish differed from diploid fish by having a faster growth rate, fewer scales in the lateral line and transverse series below the lateral line, a relatively longer gut, and fewer defo

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04875.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Prey intake, amount of time feeding, pursuit and manipulation times and growth rate were studied in the pike,Esox lucius, in relation to prey weight. Predator and prey were observed in tanks at 15°C and with a 14:10 h LD photoperiod. A total of 444 captures were recorded from five 1 g prey weight groups varying from 0 to 4.9 g. Ten pike were used weighing between 50 and 149 g.As prey weight increased, the number and weight of prey consumed decreased as did the time spent feeding, which became concentrated into the first trial of the day. Pursuit time did not vary with prey weight, but manipulation time and the weight of prey gained per unit pursuit plus manipulation time increased with prey weight.The growth rate of pike was a positive function of ration size and a negative function of the amount of time spent capturing each gramme of prey (capture cost). Growth rate was also correlated with the mean length and weight of prey eaten.The most profitable prey, as estimated from optimal foraging theory, need only be available once every 84 min for pike to maximize their net energy gain. The data show that feeding behaviour can have a direct influence on the reproductive success of pike through its effect on growth rate

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04876.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

A method is described by which the adult females of marine and freshwater teleosts can be distinguished by a biochemical test performed on a blood sample. The test depends on the measurement in the blood plasma of alkali‐labile protein‐linked phosphorus, a specific measure of yolk protein (vitellogenin). In vitellogenic females, values of 20–100 μg protein phosphorus ml plasma−1are usually found, while in males, non‐vitellogenic females and immature fish of both sexes the value is<7.5 and usually<5 μg ml−1. At the appropriate season, most females can be positively identified. Good results can be obtained 2–3 months before spawning, and in some species for an undefined period after spawning. The advantages of this method over immunological techniques for the determination of vitellogenin, such as radioimmunoassay and immunoelectrophoresis, are the wide range of vertebrate species to which it can be applied, and its low cost. Its disadvantages are its lower sensitivity and the larger volume of plasma (0.5 ml) whi

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04877.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Six hundred and two arctic charr,Salvelinus alpinus, from a small lake (30 ha) were examined for infection with plerocercoids ofDiphyllobothrium ditremumthe only species of this genus present; 466 (77.4%) harboured the parasite in an overdispersed infection. The prevalence of infection increased with age and reached 100% at 7+ years for males and 8+ years for females. The rate of infection appeared to be related to the feeding biology of the charr which did not change within the age span studied. The rate of increase in density of infection (plerocercoids per fish) decreased with age as did the degree of overdispersion. It is concluded that the infection probably induces mortality in the fish population, and that such mortality is dependent on parasite density.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04878.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Mucus is secreted to the surface of the body and fin webs ofBlennius pholisby superficial epithelial cells and by goblet cells. Some goblet cells secrete sulphated acid glycoproteins, others produce a mucus which is neutral or mixed in its reactions. The superficial epithelial cells of these areas secrete sulphated acid glycoproteins, seen by electron microscopy as electron‐lucent or moderately lucent vesicles; this secretion is not normally visible external to the skin in transmission electron microscope (TEM) sections. These cells do not react to the bromphenol blue test for proteins. Over part of the surface of the pelvic fins and the distal parts of the rays of the pectoral fins, the skin contains no goblet cells and bears a thick external secretion, or cuticle, containing protein and glycoprotein which is mainly neutral in reaction, although some cells at the edges of the region secrete weakly sulphated or non‐sulphated acidic glycoprotein. The protein content of the columnar superficial epithelial cells of these regions correlates with the fibrous nature of the secreted cuticular layer as seen by TEM; the columnar cells are characterized by extensive ribosomal endoplasmic reticulum and vesicles which stain darkly with phosphotungstic acid, less so with uranyl acetate. The distal part of the cell, containing these vesicles, reacts positively to the PAS stain. In some places the borders of the zones with fibrous cuticle are characterized by cuboidal superficial epithelial cells which give a strong positive reaction to alcian blue at pH 1.0, indicating the presence of sulphated acid glycoproteins, but also react positively to the bromphenol blue test for prote

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04879.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Some effects of low concentrations of zinc on the eggs and yolk‐sac larvae ofClupea harengusL. are examined. Deformations of the jaw, head, optic capsules, otic capsules and vertebral column are described. With some of these deformations, induced by lower zinc concentrations, the larvae survive and continue development but others, in the higher zinc concentrations, di

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04880.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Triploid rainbow trout were produced by hydrostatic pressure applied to eggs 40 min after fertilization. Treatment for 10 min with or without exposure to 2% ether produced high hatching rates. Nuclear measurements from serial section of 40‐day‐old fry and from blood smears of 5‐month‐old juveniles showed that the proportion of triploid individuals was 80–90%. Ether treatment alone did not induce triploidy. Attempts to produce tetraploids by hydrostatic pressure treatment of eggs at 8 h after fertilization failed. Parallel results were also obtained with h

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04881.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

Histological and ultrastructural studies of the thymus of the dogfish,Scyliorhinus caniculaL., revealed paired lobular masses above the first two gill arches of embryonic and newly hatched dogfish, involuting at approximately 3 weeks. It did not have defined cortex and medullary regions and ultrastructural investigations showed the tissue to be composed mainly of a range of different sized lymphocytes within a connective tissue capsule and reticular epithelial cell framework. Lymphoblasts often in mitosis were also present being more electron lucent and larger than lymphocytes. Macrophages contained cellular debris and frequently whole small lymphocytes. A cell with cytoplasmic granules was occasionally observed.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04882.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY

摘要:

The stages in the life cycle ofBothriocephalusacheilognathi have been studied with the aid of scanning electron microscopy. Emergence of the coracidium occurred after 3–5 days at 20°C. Soon after hatching the coracidium began to swell and the cilia became coiled and lost their locomotory function. The surface of the coracidium was covered in protuberances of unknown function. After consumption by the copepod intermediate host, the coracidium developed into a procercoid. Upon development of a cercomer the procercoid could infect the fish definitive host. Identification of adultB. acheilognathishould be made on specimens relaxed in cold water for 10 min, and be based on the heart shaped scolex and prominent square apical di

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1984.tb04883.x

出版商:Blackwell Publishing Ltd    

年代:1984

数据来源: WILEY