摘要:

Carbonic anhydrase (CA) activity was measured in the respiratory swimbladder, gill filaments and red blood cells of the primitive air‐breathing holostean fish, the bowfin,Amia calva. The activity of swimbladder CA, relative to gill and red cell CA activities, was within the range reported previously for unimodally‐breathing fishes and was comparable to the CA activities reported for the air‐breathing organs of teleosts. It is unlikely that carbon dioxide excretion across the bowfin swimbladder is limited to the uncatalyzed rate of HCO3‐dehydration. Bowfin blood plasma lacked any endogenous inhibitor(s) of CA, in contrast with information on teleostean fishes. This absence may have interesting phylogenetic implications and may offer some potential for investigating the nature and physiological role of plasma CA inh

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1986.tb05175.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

A histochemical study of the myotomal muscles in the grass pickerel,Esox americanus vermiculatus, and the muskellunge,E. masquinongy, was performed using actomyosin ATPase and NADH diaphorase activities. Three fibre types, i.e., red, white and pink were distinguished on the basis of their enzyme activities. White muscle fibres comprised the bulk of the myotomal musculature. The relative proportion of red muscle fibres was greater in the caudal region than in more anterior regions of the body. Pink fibres formed only a few layers between red and white. These findings are discussed in relation to the possible functional significance of the muscle fibre types in swimming and feeding behaviour in these species.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1986.tb05176.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

The osmotic fragilities of erythrocytes in blood sampled from rainbow trout adapted to sea water or fresh water did not differ significantly although blood chloride concentration and osmolarity were lower in the freshwater group.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1986.tb05177.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Eighteen populations ofNotropis lutrensis, representing all of the major river systems occupied by this species across an 1100km north‐south span of its range, showed no significant differences in mean critical thermal maximum (CTM), although general north‐south differences in climatic temperatures exist. There were no clinal trends in CTMs, and CTMs were unrelated to stream size or any other discernible feature of the local habitats. Previous research has shown thatN. lutrensiscan adapt rapidly to an artificially altered thermal regime. The present results suggest that even though a species may have potentially ‘labile’ thermal physiology, it may nonetheless be ‘static’ or evolutionarily conservative in such characters when natural populations are examined

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1986.tb05178.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

C‐banded mitotic chromosomes ofKatsuwonus pelamis(Linnaeus) were examined by transmission electron microscope (TEM) and results compared with light microscopy images. Advantages of the TEM technique are note

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1986.tb05179.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Sequential changes in water content and inorganic ion concentrations occurring in intra‐ovarian oocytes of the grey mullet,Mugil cephalusL., during hormone‐induced final maturation are described. Post‐vitellogenic oocytes have a water content of 59.4%. During final maturation, oocyte water increases rapidly to a maximum of 84.8% at oviposition. Hydration is accompanied by a relatively small increase in dry matter due to the concurrent uptake of inorganic ions and an apparent uptake of organic matter.Net uptake of Ca2+during hydration is negligible. Net uptake of Mg2 +and Na+occurs in less than equimolar proportions. Net uptake of K+and Cl−occurs in greater than equimolar proportions prior to ovulation, returning to equimolarity at oviposition. Hence, hydration results in a dilution of intracellular Ca2+, Mg2+and Na+to minimum concentrations at oviposition. In contrast, K+and Cl−concentrations are slightly elevated prior to ovulation, returning to initial levels at oviposition. A 1:1 stoichiometric relationship in net uptake of K+andCl−is evident.Intracellular osmotic pressure in post‐vitellogenic oocytes is 203.4 ± 18.0 mOsmolkg−1. Osmotic pressure rises to a peak of 421.3+ 17.3 mOsmol kg−1prior to ovulation, then declines to 313.3 ± 15.0 mOsmol kg−1at oviposition. This rise in osmotic pressure prior to ovulation cannot be accounted for solely on the basis of inorganic ion uptake and must be attributed to changes in intracellular concentrations of organic solutes as well. An apparent increase in non‐ash dry matter during hydration suggests that a net uptake of organic solute is involved. A relatively small organic molecule with high osmotic activity (e.g., ami

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1986.tb05180.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

When shoaling minnows encounter a stalking pike, fish leave the shoal, approach the potential predator and then usually halt briefly before returning to the group. This behaviour, termed predator inspection, has been reported from encounters with both real and model pike. A description of inspection behaviour is given using data from experiments with a model pike made to approach foraging minnows with a standardised stalk. Evidence is presented that inspecting fish assess the risks involved. Individual minnows which have carried out an inspection visit to the predator model exhibit changes in behaviour on return which are contingent upon the state of the model, demonstrating that information is gained. Other fish change their behaviour after an inspector returns to the group, suggesting that information about the threat is transferred among the shoal. Possible costs of predator inspection behaviour may balance these benefits of knowledge, but require further investigation.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1986.tb05181.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

The change of egg size in sardine of the Saronikos Gulf (Greece) during the course of the spawning season is examined in relation to the changing conditions of temperature and plankton biomass. It is suggested that the intraspecific variation of egg size is an ecophenotypic rather than a genetic phenomenon, arising from the disturbance of the normal ratio between growth and differentiation rates during the oocyte stage. Assuming that a positive relation between the growth rate of the mother and the growth rate of the eggs during maturation exists, environmental or endogenous factors promoting or retarding the adult growth rate will accelerate or decrease the growth rate of the eggs in relation to the rate of differentiation, resulting in smaller or bigger eggs respectively.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1986.tb05182.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

Samples of brown trout,Salmo trutiaL., from 34 locations throughout the Lough Neagh system in north‐east Ireland were electrophoretically examined for genetic variation at 28 enzyme loci. Patterns of allelic variation at 12 polymorphic loci indicated the existence of genetic differentiation within as well as among several river systems, suggesting the existence of multiple brown trout populations. Significant gene frequency differences were detected over distances as little as 3 km, demonstrating the propensity of this species for microgeographic genetic differentiation. This was confirmed by a hierarchical analysis of genetic variance, some 35% of among‐sample variance being distributed within tributaries. Within Lough Neagh itself significant genetic differentiation was detected between two morphotypes (dollaghan and salmon‐trout) and for one of these (dollaghan) among samples from different years and from different areas of the lough. This suggests the existence of genetically differentiated subpopulations of originating from separate river catch

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1986.tb05183.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY

摘要:

The relative effects of inter‐ and intra‐specific competition on the survival and growth of stocked salmon were investigated in an upland trout stream during summer and winter sampling periods. The stream was divided into two areas by an impassable fish barrier, and trout were removed from the upstream section prior to 2 years of salmon stocking. Salmon fry stocked into the cleared area survived more than twice as well and grew significantly larger than those stocked into the area containing trout and older salmon. Intra‐specific competition from older salmon in the second year of stocking in the cleared area significantly reduced the survival and growth of the O+ salmon. However, these were still significantly larger and survived better than those in the control area where inter‐specific competition from trout was maintained. Some immigration of trout to the cleared area occurred; these showed greatly enhanced growth rates compared to those in the control area, reflecting low intra‐specific trout competition in the former. Inter‐specific competition effects of older salmon on both trout fry growth and survival were also detected, although the latter did not become apparent until the winter. This is discussed in terms of the relative importance of biotic and abiotic regulating mechanisms. Evidence of allopatric niche segregation is also discussed, since salmon in the cleared area did not have a biomass equivalent to that in the area which also cont

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1986.tb05184.x

出版商:Blackwell Publishing Ltd    

年代:1986

数据来源: WILEY