摘要:

The gastric evacuation of juveniles ofCoregonus lavaretusL. fed on livingDaphnia pulicariawas investigated. Three successive stages of stomach evacuation were observed when one meal per day was given: (i) a lag phase between the end of food intake and the beginning of stomach evacuation, (ii) a linear reduction of stomach content, (iii) a long residence time for food relics in the stomach. The initial stomach content and the stomach evacuation time are correlated positively. The stomach content increased during feeding when three meals day−1were provided and it decreased when no food was available. During the course of an experiment the highest stomach content found increased with increasing daly ration. Excess feeding resulted in a low stomach content similar to that found with rations about 30–50% of the maximum daily food intake. Therefore the daily food intake cannot be determined by the single parameter of stomach content alone. Identical initial stomach contents showed significantly higher stomach evacuation rates under three meals day−1conditions than under one meal day−1con

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05779.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

In a clear‐water Nigerian stream,Tilapia mariaeshowed lunar periodicity in breeding activity over a 9‐week study period. Most clutches were laid during the last quarter of the moon cycle. It is suggested that spawning before full moon enhances the effectiveness of the parental care by allowing a maximal amount of moonlight during the most critical phases in the development of the young and by providing a cue for the pairs to spawn at the same t

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05780.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Wild plaice from two locations were examined for liver metallothionein and liver and serum zinc content, before, during and after the breeding season. During the early stages a number of females had very high liver metallothionein and zinc levels. Egg formation and ripening were accompanied by a reduction in serum zinc. In males, the metallothionein levels did not reach such high values and were not correlated with gonad development.There was a correlation between the zinc concentration of the liver and the metallothionein concentration of the liver. Above the threshold value for metallothionein formation, approximately half the additional zinc was found in the metallothionein and half in non‐metallothionein pool(s).Intramuscular injection of oestradiol 3‐benzoate into immature females caused a significant increase in liver weight but a depression in metallothionein concentration relative to the contr

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05781.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The blood granulocyte composition of 10 species of dogfish is given, together with ultrastructural observations made onEtmopterus baxteriLeydig organ and blood, and on spleens ofOxynotus bruniensis, Deania calcea, Scymnodon plunketiand blood ofCentroscymnus crepidator. Neutrophilic granulocytes, which were common, had spherical granules that developed a dense core, which then lost contents to become lucent. Eosinophilic granulocytes had ovoid or elongated granules with a fibrillar content that became aligned longitudinally, and rarely formed an axial rod. Eosinophils had large spherical granules that were electron‐dense but in early stages had a disorganised fibrillar content. These cells correspond to the neutrophils, heterophils and eosinophils, respectively, of other elasmobranchs.Dogfish granulocytes are compared with those of other elasmobranchs, and their lack of similarity to those of higher vertebrates is note

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05782.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The blood granulocyte composition of seven species of ray is given together with ultrastructural observations made on the epigonal organ and blood ofPavoraja spiniferaand the spleen of a deepwater rajid skate. Under the light microscope three granulocyte types, eosinophils, eosinophilic granulocytes and neutrophilic granulocytes could be distinguished. At the EM level two granulocyte types were apparent, one with elongated granules containing longitudinal fibrils that consolidated to form an axial rod‐like inclusion, and the other with large, spherical, uniformly electron‐dense granules. Correlation of light and electron microscope observations indicated that the neutrophilic granulocytes with weakly basophilic, elongated granules become weakly eosinophilic, as eosinophilic granulocytes, and these in turn develop to eosinophils with granules containing axial rods. The other granulocyte type forms another population of eosinophils with spherical granules.The inter‐relationship of these granulocytes, the identification of eosinophilic granulocytes, or heterophils, as immature eosinophils, and the co‐existence of two morphologically distinct eosinophil forms are di

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05783.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The peripheral blood granulocyte composition of five species of shark is given together with ultrastructural observations made on the epigonal organ and blood ofMustelus lenticulatusand spleen ofApristurussp. Three granulocyte lineages occurred inMustelus. Ultrastructurally, eosinophilic granulocytes contained granules that were very variable in size and contained parallel fibrillar arrays that were unidirectional in small granules, but which were often orientated in several directions in larger granules. This dense core material sometimes formed angular crystalloids.Eosinophils had ovoid or irregular granules that were usually uniformly electron‐dense, but some had an eccentric ovoid area of greater electron‐density. Some eosinophils enter the blood where they are phagocytic, but others, in blood and epigonal organ, showed an unusual but characteristic process of disintegration, leaving a ragged cell full of cellular debris.The third granulocyte type had features of mast cells and basophils of higher vertebrates and was tentatively identified as belonging to that lineage. The inter‐relationships of these cells, and of them with granulocytes of other elasmobranchs, are disc

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05784.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Response ofChanna punctatusto acidic water was studied by exposing fishes to pH 3.5, 4.5, 5.5 and 6.5 for 6 weeks. Growth and mortality data indicated increasing stress as the acid level in the ambient water increased. While no mortality was recorded at pH 6.5, a distinct loss of weight compared to continuous gain in body weight in control fish indicated stress. As the pH level decreased, the rate of loss in body weight increased accompanied by mortality which rose to as high as 60% within 3 weeks in fishes exposed to water at pH 3.5.Haematological investigations confirmed the general stress indicated by growth and mortality data. Thus. RBC and related values indicated overall polycythemia. However, eosinophils, basophils. and large and small lymphocytes showed a distinct fall in number as compared to the control.Correlated haematopoietic studies revealed that both the initial and penultimate stages in RBC and neutrophil development recorded an increase parallel to that observed in peripheral blood, but intermediate stages, probably because they were unable to keep pace with the fast turnover, showed a relative decrease.Biochemical investigations showed an increase not only in blood glucose level but also in liver glycogen content. However, there was a significant decrease in muscle glycogen reserves.The significance of these changes is discussed.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05785.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The histology of the gonads of free and captive summer whiting,Sillago ciliata, were compared to assess the potential of this fish for aquaculture. There were no qualitative differences between the free and captive males: both completed spermatogenesis through to spermiation. The captive females were non‐reproductive, reaching only the vitellogenic stage before the eggs were resorbed by atresia.A reproductive score was devised to assess reproductive potential in the comparison of the two populations. The females in the captive population had lower reproductive potentials, as shown by the score, and started development a month later than the normal free population. The captive males had higher reproductive scores than the free fish but they were also not spawning and, therefore, the higher score indicated that this potential was not realized. The score provides a standard against which experimental results can be compared and subsequently assesse

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05786.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

The occurrence ofHaemogregarina bigeminainBlennius pholiswas studied at four localities on the Portuguese west coast. Prevalence ranged from 2.9 to 78.6% and was significantly different (P<0.01) at the various localities. Intensity of infection in individual fish was usually low (<0.01 % of erythrocytes infected) but one specimen was heavily parasitized (2.8% erythrocytes infected). The smallest infected fish was 3.2 cm long; all 7.0 cm and longer fish were infected. Development was not seen outside erythrocytes or within leucocytes. Some erythrocytes (<0.01%) in one fish were unusual in containing four mature gametocytes. Circumstantial evidence indicates that prevalence was higher in polluted waters. Possible transmission routes for the parasite are discussed.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05787.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY

摘要:

Sex‐inversion ofCoris julis, a protogynous hermaphrodite, was studied using histological and cytological criteria. Four stages were recognized: oocyte and oogonial atresia; occurrence of spermatogonia with primordial germ cells (PGC) in the ovarian wall; onset of spermatogonial proliferation; considerable proliferation of spermatogonia and PGC with build‐up of seminiferous tubules. Spermatogonia arise from PGC, undifferentiated and bipotential cells, in which mitotic activity was detec

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1987.tb05788.x

出版商:Blackwell Publishing Ltd    

年代:1987

数据来源: WILEY