摘要:

The prevalence and relative density of branchial and gut parasites taken fromAlmafullaxin the estuary of the River Severn, at the start of the freshwater phase of its spawning migration, were compared with those taken from their spawning grounds in fresh water.Mazocrues alosueshowed no significant difference in prevalence between the two habitats, though their relative density did fall significantly. Because of the direct relationship between length and relative density, this difference may be explained by the estuary samples ofA. fulluxbeing of fish significantly larger than those from fresh water. Other possible causes are discussed. The prevalence and relative density ofM. alosaeshowed a trend to increase with age of the host. Repeat spawningA. fallaxhad a significantly greater relative density and prevalence of M.alosuewhen compared to virgin fish.Analysis of the sampled population showed thatClavellisu emarginatadeclined significantly in both prevalence and relative density in fresh water, and this was confined to the younger and first time spawningA. fullux. Thynnuscuris aduncumshowed significant reductions in prevalence and relative density of infection in fresh water when compared to the estuarine samples.The speciesHemiurus uppendiculatusandPomphorhynchus laevisshowed no significant difference in prevalence and relative density of infection, andPronoprymna ventrzcosano significant difference in prevalence, between the two habitats.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1985.tb03199.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Lahontan cutthroat trout thrive in saline‐alkaline lakes, where other trout species often cannot survive. We examined Lahontan cutthroat trout from nine lakes in which salinity and alkalinity ranged from about 90 to 12 000 mg1−1and 60 to 3500mgl−1as HCO3−respectively, for sublethal histological changes in gill, kidney, and liver tissues. Gill chloride cell hyperplasia, gill lamellar epithelial separation, kidney glomerular swelling, blood congestion in kidneys, and deposition of hyalin droplets in kidney glomeruli, tubules, and hemopoietic tissues were the histological alterations statistically associated with differences in lakewater chemistry.Deposition of hyalin in kidney tubules was the only histological change judged pathological and whose severity appeared sufficient to jeopardize normal organ function. Differences in lakewater chemistry explained nearly 90% of the variability observed in severity of tubular hyalin degeneration, and SO42−was the ion most positively correlated with increasing tubular hyalin. Our results suggest that Lahontan cutthroat trout will develop slight to moderate hyalin degeneration in kidney tubules if stocked into lakes where salinity and SO42−concentrations equal or exceed 5000 mgl−1and 2000mgl−

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1985.tb03200.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The alarm substance cells and mucous cells of various species of Ostariophysi do not react uniformly to treatment with androgen and other steroid hormones. This indicates that the mechanism controlling formation of alarm substance is not uniform in the Ostariophysi and three exist at least two such mechanisms, one of which is operated by androgens and perhaps other steroid hormones of the gonads. Steroid hormones from the adrenal cortex proved ineffective. In the European minnow, anti‐androgen (androcur®, cyproteroneacetate) had an efrect opposite to that of androgen, while androgen treatment upon this species led to an increase in the size of mucous cells and a reduction in the alarm substance cells. The epidermis of androgen‐treated European minnows contained neither alarm substance cells nor alarm substance, and skin extracts of such fish proved ineffective in behaviour experiments upon fish schools. The effect of further hormone treatments are discussed and the reactions of the European minnow are compared to those of other spe

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1985.tb03201.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The dynamics of a subtoxic pulse of non‐dietary109Cd was followed for up to 304 days after the exposure period in female zebrafish. The retention of dietary109Cd was also estimated.The distribution of109Cd was studied by autoradiography, whole‐body analysis and tissue sampling. After exposure to non‐dietary109Cd for 10 days there was a rapid loss of109Cd from the gills. The109Cd content of the alimentary canal exceeded that which could have been expected from normal drinking. Based on the distribution pattern of non‐dietary109Cd in tissues, two groups of tissues were distinguished:(i)the gills, alimentary canal and heart which showed maximum109Cd values directly after exposure, followed by a pronounced decrease up to day 21;(ii)the liver, kidney, ovary and muscle, in which there was a delay in maximum109Cd activity to days 21–42, with subsequent loss.Small amounts of109Cd were noted in fry and fertilized eggs originating from zebrafish exposed to non‐dietary109Cd. After exposure to dietary109Cd, less than 5% was retained in the zebrafish body, mainly in the alime

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1985.tb03202.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

There were significant inverse correlations between rearing density of rainbow trout,Salmo gairdneriRichardson, and final body weight, plasma L‐thyroxine (T4), trüodo‐L‐tryronine (T3), cortisol and protein concentrations, plasma T4/T3ratios and thyroid epithelial cell height. In addition, hepatosomatic indices and plasma free fatty acid concentrations were higher in fish reared at low (134 g 1−1) density compared with groups reared at medium (210g1−1) or high density (299g 1−1), and the post‐feeding (3.5‐4h) elevation in plasma glucose and triglyceride levels evident in trout maintained at low rearing density was not found in those fish reared at higher densities. There were no significant effects of rearing density on hematocrit, carcass composition, hepatic glycogen and lipid levels and interreg

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1985.tb03203.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The unisexual fishPoecilia formosa(the Amazon molly) reproduces by gynogenesis, a process in which sperm from the males of the host bisexual species activates development of its eggs. Unisexuals live with one of the host species in nature and compete with bisexual females for the males. It was long thought that male discrimination and mate selection established a balance between the unisexual and bisexual populations. Thus, hierarchies of males were set up in which dominant males mated with their conspecific females and subordinates mated with the Amazon molly. Recent evidence suggested, however, that male fish do not discriminate between their own females and the Amazon molly, and that there always are more males available than sexually receptive females of both species.Our findings indicate that male behaviour may be more complex than suggested by either hypothesis. Mate discrimination and courtship behaviour appear to increase with age, so that large males show almost complete preference for their conspecific females, but smaller males will mate with the Amazon molly. In complex groups, small males often dart in and mate with their own females whilst the large males are engaged in courtship activities and defence of territory.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1985.tb03204.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The karyotypes of six species of Acestrorhynchinae (Acestrorhynchus alus, A. lacustris, Oligosarcus hepsetus, O. jenynsii, O. macrolepisandO. pinloi) and of one species of Cynopotaminae (Galeocharax knerii) were studied. The six Acestrorhynchinae species have 2n= 50, whileGaleocharax kneriihas 2n= 52 chromosomes. Some chromosomal characteristics were detected which permit establishing some karyotypic relationships among the different species investigated. Thus, among the Acestrorhynchinae, the fourOligosarcusspecies are relatively more related to one another than the twoAcestrorhynchusspecies, at least with respect to the cytogenetic data considered. On the basis of the methods used, no sex chromosome heteromorphism was detected in the species for which a comparative study between male and female specimens was possible.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1985.tb03205.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Chronic elevation of plasma cortisol levels in the brown trout by means of slow‐release, intraperitoneal implants increased the susceptibility of the fish to disease. Elevation from a mean basal level of 1–4ng ml−1to ∼10ngml−1for a period of 2–4 weeks was sufficient to increase the mortality rate due to furunculosis,Saprolegniainfection and bacterial fin‐rot. This level of plasma cortisol is well within that capable of being produced by the fish under conditions of chronic stress. The increase in susceptibility to disease was not accompanied by a reduction in the number of circulating lymphocytes and it is suggested that under certain conditions chronically‐elevated cortisol levels may be more sensitive, predictive indicators of reduced disease‐resistance than are changes in

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1985.tb03206.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The nutritive quality of ingested material of adultOreochromis mossambicuswild populations from 12 perennial, man‐made lakes were evaluated for four climatic seasons. The seasonal variation in condition of each population, and the overall condition of each population, considered as the theoretical weight of a 20cm individual, was computed from the length‐weight regressions, which were curvilinear. The mean overall condition of theO. mossambicusreservoir population was 152.6 g (s.d.± 9.5) and ranged between 139.8 and 167.8 g. Distinct patterns in the seasonal changes in condition of an individual population were not apparent. The mean percentage of protein and total organic matter (TOM) and calorific content (kJg−1) of the ingested material were 20.7% (s.d.± 3.7; range 9.6–35.2%), 46.0% (s.d.± 9.8; range 20.9–73.7%) and 11.6 (s.d.± 3.4; range 4.6–20.9) respectively. The amount of each of the above components for any one population varied seasonally in relation to the changes in feeding habit. The protein content of the ingested material of those populations devouring predominantly detritus also showed seasonal variability. The amount of protein (mg) in the digestible total organic matter (DTOM) and the calorific content (Cal) in the ingested material were related to the TOM content as follows:The overall body condition (BC) ofO. mossambicuspopulations was linearly rebated to the digestible protein: energy ratio (PER) thus:The study indicates that a mixed diet was superior in nutritional quality to a single‐component diet. especially with respect to

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1985.tb03207.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

This study examined the influence of body size and temperature on oxygen consumption and food converstion in juvenile American eels (Anguilla rostrata). The weight‐specific oxygen consumption rate for underdeveloped eels (18 months old) was significantly higher than the weight‐specific oxygen consumption rate of developed eels of the same weight (6 months old). Oxygen consumption rates increased linearly with weight at each experimental temperature (15, 20, 25°C) when data were transformed logarithmically. No significant differences were found among slopes oflog transformed data at varying temperatures. Oxygen consumption was significantly higher at night (2300 h) as compared to morning (0900 h). The results indicate that underdeveloped eels use more energy and use less food less efficiently than developed

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1985.tb03208.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY