摘要:

Liver stores the major part of lipids in both mature and immatureTorpedo torpedoof both sexes. Fluctuations in the lipid contents of liver, muscles and gonads of immature fish followed the relative change in food intake throughout the year. Hepatic and muscular lipids in mature females diminished before ovulation and were intensively consumed in the last stages of gestation (in pregnant females). After parturition, the recovery of the lipid stores was very rapid due to intensive food uptake. Storing of hepatic lipids in mature males started a little before gonadal maturation and reached a maximum in January and February while gonadal lipids decreased in the same period. Gonadal lipid for both sexes fluctuated in parallel to fluctuations in the GSI. Water content showed significant inverse correlation with lipid content in both liver and gonad tissues, but no significant correlation was recorded in the muscle tissues.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1993.tb00419.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Three Arctic charr strains and their crosses were evaluated with respect to growth and sexual maturation frequency. No significant heterosis was observed for growth. One out of five crosses was heavier, but not significantly so, than the best performing parental strain at ages 1 + and 2. The five other crosses did not perform better than the best performing parental strain at any age. Cross‐breeding was not recommended as an effective method to improve growth performance in Arctic charr. Growth performance of reciprocal crosses differed significantly in all strain combinations: crosses resembled more the male parent strain than the female parent strain. ANOVA for male maturation frequency showed a highly significant effect of the male parent strain and a weakly significant effect of female parent strain. In the Ottsjö strain mature males were significantly larger than immature fish and females. Such size difference was also observed in the offspring when sires of the Ottsjö strain were crossed with dams of the faster growing Honavan strain or with dams of the Rensjö strain. When Ottsjö dams were crossed to sires of the other strains no significant size difference between mature males and other fish was

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1993.tb00420.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Great diversity was found in the correlation between absolute fecundity (F) and the length (L) and age (t) of pikeperch,Stizostedion lucioperca(L.) in 10 water bodies that differed in their geography, morphology, and ecology. However, this diversity is only apparent, and theFlt(L)relationships are logistic, with the linear, power, exponential and logarithmic functions found in different populations, representing segments of the sigmoid curve. The expected linear relationship between fecundity and weight was found for the fish in seven water bodies, but it was curvilinear in three others. In the latter waters, pikeperch matured at a comparatively young age, with shorter length, and lighter weight, yet their initial fecundity was comparatively lower.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1993.tb00421.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The early development ofGaleichthys feliceps(Valenciennes, 1840) was investigated using a combination of incubator‐reared embryos and embryos removed from the buccal cavities of wild‐caught parents. The eggs were 15·7 mm in diameter and the average brood size was 49. Hatching occurred at an advanced developmental state after approximately 75–80 days, when branchial and fin differentiation were complete. Exogenous feeding began within the adult buccal cavity shortly after hatching. The young were released as juveniles after approximately 140 days, at a total length of

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1993.tb00422.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Opening the pericardium to the ambient bathing fluid surrounding thein situperfused dogfish (Squalus acanthias) heart caused a precipitous fall in cardiac output. Cardiac output fell by 55% despite the rise of mean input pressure from subambient, to near zero levels. Lower cardiac output caused a fall in mean output pressure but not diastolic pressure as this was set by the experimenters. With the pericardium intact, the heart was filled by suction. With an open pericardium the magnitude of negative input pressures was severely reduced. None the less, far short periods within the cardiac cycle, the heart was still able to generate subambient pressures in the atrium and so draw fluid from the central veins.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1993.tb00423.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

A modal diploid number 2n=38 has been determined in both sexes of the pleuronectiformBothus podasfrom the Gulf of Palermo (Mediterranean). An XX‐XY sex‐determining mechanism presumably occurs in this species. Application of silver staining (NORs) along with G‐ and C‐banding techniques showed that secondary constrictions occurring in a large metacentric pair were variable in length in different fish. Polymorphisms of these areas seem to have a genetic, rather than transcriptional

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1993.tb00424.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The reproductive cycle of the red mullet is described on a macroscopic scale in terms of the GSI, HSI andK, and on a microscopic scale in terms of histological changes in the ovary and changes in the oocyte size frequency distribution. On the southern coast of Brittany the red mullet breeds in May and June. During oogenesis, the previtellogenic period lasts 6 months and the secondary phase of vitellogenesis no more than 3 months. When spawning commences the process of vitellogenesis ceases and up to 20% of the vitellogenic oocytes become atretic. Prior to spawning a single batch of oocytes can be seen to be entering secondary vitellogenesis. During the immediate prespawning and spawning periods the existing vitellogenic oocytes mature but there is no recruitment from the stock of previteilogenic oocytes. This results in a gap or hiatus in the oocyte size frequency distribution between previtellogenic and vitellogenic oocytes within which there are very few resting or maturing oocytes. The red mullet appears to be a determinate spawner, in which egg loss through atresia considerably reduces the potential fecundity.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1993.tb00425.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Groups of recently hatched fry of rainbow trout,Oncorhynchus mykisswere maintained in the laboratory in order to investigate the effects of age, ration level and temperature on whole body growth, nucleic acid concentrations, protein synthesis rates and enzyme activities. In fry of up to 30 days after hatching, which were feeding but still had some yolk sac, no significant change in mean RNA concentration was observed with ration level. In older fry of 50 days or more, when the yolk sac was completely absorbed and exogenous feeding fully established, the concentration of RNA was correlated with the rate of protein growth. RNA concentrations and activities of citrate synthase and lactate dehydrogenase were significantly different between fed and starved fry. As water temperature was raised (from 5 to 15° C), higher rates of protein growth were brought about by an increase in the rate of protein synthesis and also by increased efficiency of retention of synthesized protein (reduced protein turnover). In fed fry, no change in RNA concentration was found with increasing temperature, while the amount of RNA per cell (RNA: DNA) decreased, indicating that increased rates of protein synthesis were due to increased RNA efficiency

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1993.tb00426.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Aquaria with added river red gum,Eucalyptus camaldulensis, litter became hypoxic, with decreased pH and contained up to 30 mg 1−1tannin and lignin. Survival of golden perch,Macquaria ambigua, larvae in aquaria treated with a simulated annual litter density of 450 g m−2for 72 h was 14·9% for 15‐day‐old larvae and 0% for 8‐day‐old larvae. A litter density of 1223 g m−2resulted in total mortality for both age groups of larvae. Aeration increased survival of larvae to a minimum of 68·8% in 1223 g m−2litter treatments compared to 89·8% in aerated controls and 86·8% in non‐aerated controls. A kinetic behavioural assay was used to detect alarm responses in golden perch larvae and juveniles exposed to leachates from river red gum bark, leaves and wood. Eight‐day‐old larvae exposed to bark and wood leachates (0·001–10 g 1−1) exhibited an initial period of hyperactivity, followed by a concentration‐dependent decrease in spontaneous activity. Larvae exposed to leaf leachates displayed only a decrease in spontaneous activity. Four‐month‐old juveniles exposed to wood leachates were also initially hyperactive, then progressively developed mild hypoactivity at increasing leachate concentrations. Juveniles exposed to wood leachates at 20g 1−1for 30min suffered 97·5% mortality in 96 h. Wood leachates induced dose‐dependent lamellar fusion, epithelial dissociation and necrosis in the gills. The presence of toxic leachates and low oxygen availability in flooded river red gum forests may make these habitats un

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1993.tb00427.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The caryophyllidean monozoic tapewormMonobothrium wageneriis recorded for the first time in the U.K. in tenchTinca tincafrom four different sites in S.E. England. The likelihood that this is an exotic import is discussed. It is considered that the weight of evidence indicates that it has been introduced into the U.K. probably in ornamental tench.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1993.tb00428.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY