摘要:

The ultrastructure of the intestinal epithelium has been studied in three species of freshwater fishes, differing from one another in the type of feeding. The pike (a typical predator), the burbot (a predator‐facultative benthophage), and the bream (a typical benthophage) were examined. The differences in the condition of epithelial ceils and peculiarities in the structure of the brush border of enterocytes in fishes have been revealed in winter periods. The role of the brush border of enterocytes in the increase of the digestive and transport surface of the intestine in fish is discusse

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb01197.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Male and femaleCarassius auratuswere exposed to safe (SC; 0.01 ppm) and sublethal (SL; 0·1 ppm) concentrations of an organochlorine pesticide γ‐hexachlorocyclohexane (γ‐HCH) for 4 weeks during the pre‐spawning phase (June) of the annual reproductive cycle. Gonadosomatic index and gonadotropin levels were significantly lower after exposure to both γ‐HCH concentrations than in control fish. After 4 weeks exposure, gonadal tissue from control, SC and SL exposed fish was incubated with carp hypophyseal homogenate (chh). The chh stimulated production of testosterone, 17,20β‐dihydroxy‐4‐pregnen‐3‐one (17,20βP), 11‐deoxycortisol, and 11‐ketotesterone (11‐KT) was estimated in the unconjugated (free) and conjugated (glucuronide) fractions by radioimmunoassay. In both sexes, testosterone production was greatly decreased in γ‐HCH exposed fish compared to controls. 17,20βP production was low in all fish and was unaffected by γ‐HCH. Free 11‐deoxycortisol production by testicular fragments was higher in SL and SC compared with controls, while conjugated 11‐deoxycortisol was increased only higher in the SL. In ovarian fragments from exposed fish, free 11‐deoxycortisol decreased while glucuronide concentrations increased compared with controls. 11‐KT production was significantly decreased in testicular fragments of exposed fish. The results indicate that γ‐HCH inhibits gonadal recrudescence by decreasing both gonadotropin secretion and i

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb01198.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Spawning time and sizes at first sexual maturity and at sex‐reversal are described in the tropical blue‐spotted grouperCephalopholis taeniops. All juvenile fish possess non‐functional ovaries. At sexual maturity, most juvenile fish become functional females. Some of these later change sex to become males. The remaining juvenile females change immediately to males, without time as functional females. This is a new scheme for sexual differentiation of gro

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb01199.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Electrophoretic data were analysed from 49 species of freshwater fish, 57 species of marine fish, and seven anadromous species. For each species, at least 15 individuals had been assayed for at least 15 loci in two or more subpopulations. The results showed that while average total heterozygosity (H̄T) was approximately equal in freshwater and marine species (0·062 and 0·064 respectively), subpopulation heterozygosity (H̄s) was significantly less in the former group (0·046 and 0·059 respectively). Consequently the average degree of genetic subpopulation differentiation (H̄ST) was significantly greater for freshwater species (0·222 v. 0·062). On average, it is likely that marine subpopulations exchange between 10 and 100 times more migrants per generation than freshwater subpopulations, presumably because of the relative absence of barriers to dispersal in the marine environment. The reduced values ofHsin freshwater species are likely to reflect reduced effective subpopulation sizes relative to marine species. The few andromous species that have been analysed show intermediate leve

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb01200.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Morphometric measurements were carried out on some of the structural parameters affecting oxygen diffusing capacity in red muscle of 15 specimens ofO. niloticusbody weight (b.w.) 0.65–812.3 g. Total capillary length and surface area and total morphometric oxygen diffusing capacity in body trunk red muscle had average values of 4792·7 (± 1740.7 s.e.) m, 415·4 (± 157·3 s.e.) cm2and 0·0213 (± 0·0075 s.e.) ml−1min−1cm−2mmHg respectively. When expressed as functions of b.w. these parameters had scaling values of 1·02, 1·07 and 0·993 respectively. These figures show a slight increase or almost no change in these structural parameters (which affect diffusion of oxygen to mitochondria in red muscle) per unit weight of fish. This should be important as the role of sustained swimming (by red muscle) becomes more important in larger tilapia. Oxygen diffusion distances were short [3·11 (±0·16 s.e.) μm] which facilitates diffusion of oxygen to mitochondria. The scaling value for oxygen diffusion distances of 0·067 (with respect to body weight) shows a slight increase in this parameter with development. This value is significan

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb01201.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The ontogenetic development of serotonin immunoreactivity (5‐HTir) neurons was investigated by immunocytochemistry in the brain of the mackerel, from fertilization to the complete resorption of the yolk sac (201 h). 5‐HTir appears first in cell bodies in the diencephalon, on both sides of the third ventricle. At hatching time 5‐HTir perikarya are also present in the mesencephalon and the inferior raphe but in small numbers. During larval stages, immunoreactivity appears consecutively in the area thalamo piaetectalis, the nuclei raphe pallidus and obscurus, the nuclei tegmenti dorsalis lateralis, recessus posterioris, lateralis hypothalami and paragigantocellularis lateralis. These results, together with previous findings, suggest a common pattern of distribution of the different 5‐HTir neuronal populations in the brain of a teleost during ontogeny but a different sequence of appearance of initial 5‐HTir in these populations betwee

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb01202.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

In turbot larvae,Scophthalmus maximus, deprived of food for 24 h there was a significant increase in the specific surface of the epithelium and the corresponding microvillous border of the foregut accompanied by slight cellular degeneration. Following 48 h starvation Sarvae showed severe tissue degeneration in the foregut mucosa, progressing to extensive mucosal desquamation and cellular sloughing. Intracellular vacuolation of the epithelium and loss of microvilli was also extensive and the ability of the gut to absorb food must be severely impaired, with further starvation probably resulting in larval death. There was no evidence of parasitic infection in any of the larvae sampled and all observed alterations are attributable to food deprivation.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb01203.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The presence of adult maleCorynopoma riiseiwas found to inhibit the maturation of juvenile males. Males in a conspecific community tank took longer to mature and did so at increasingly slower rates compared to isolated controls, providing a positive correlation between size and time of maturational onset. The inhibitory effect increased with greater numbers of adult males. The first males to mature did so at accelerated rates, suggesting positive as well as negative control. Tanks in which adult males were removed as soon as maturation was complete showed an intermediate pattern, with no lengthening of the maturational time course but an increase in standard length. Histological examination revealed immature males with lengths greater than the control range; these appear to represent inhibited animals. Both the testes and pituitary gonadotropic zone of these males appeared undeveloped, arguing for inhibition at least at the hypothalamic level. This phenomenon has also been described in poeciliids The presence of a similar complex mechanism in two distant groups of fishes suggests convergent evolution. It also suggests that this phenomenon may be physiologically possible for a wide range of fish species.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb01204.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Young‐of‐the‐year, predator‐naive fathead minnows,Pimephales promelas, from a pikesympatric population did not respond to chemical stimuli from northern pike,Esox Indus, while wild‐caught fish of the same age and size did. These results suggest that chemical predator recognition is a result of previous experience and not genetic factors, Wild young‐of‐the‐year minnows responded to pike odour with a response intensity that was similar to that of older fish, demonstrating that the ability to recognize predators is learned within the first year. The intensity of response of wild minnows which had been maintained in a predator free environment for 1 year was similar to that of recently caught minnows of the same age, suggesting that reinforcement was not required for predator recognition to be retained. Naive minnows that were exposed simultaneously to chemical stimuli from pike (a neutral stimulus) and minnow alarm substance exhibited a fright response upon subsequent exposure to the pike stimulus alone. Predator‐naive minnows exposed simultaneously to chemical stimuli from pike and glass‐distilled water did not exhibit a fright response to the pike stimulus alone. These results demonstrate that fathead minnows can acquire predator recognition through releaserinduced recognition learning, thus confirming a known mechanism through which alarm substance may benefit the receivers

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb01205.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Specific binding of gilthead sea bream growth hormone (sbGH) to liver membrane preparations was a time and temperature dependent process, and was saturable by increasing amounts of membrane proteins. Scatchard analysis evidenced a single class of high‐affinity and lowcapacity binding sites. Ovine prolactin, recombinant tilapia prolactin, carp gonadotropin and chinook salmon gonadotropin did not compete for the125I‐sbGH binding sites, while recombinant trout GH, bovine GH and human GH displaced iodinated sbGH in a dose dependent‐manner. IGF‐I‐like immunoreactivity was detected after acidification of plasma and removal of IGF‐I binding activity. A parallel displacement to the rhIGF‐1 standard was observed with extracted plasma samples. Free and total hepatic GH‐binding decreased during long‐term starvation (3–9 weeks), returning to control values during the refeeding period. Plasma IGF‐I‐like immunoreactivity showed a similar trend. To our knowledge, this is the first report that indicates a coordinated regulation of GH‐binding and plasma somatomedin‐like activi

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb01206.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY