摘要:

The eels of the Lower Elbe (15–35 cm total length, freshwater age groups III–V) show a high incidence of epidermal papillomas. These neoplasms, situated mainly in the snout region, show a marked seasonal fluctuation. The incidence is low in spring and autumn (min. 2–3 %) and rises sharply in summer (max. 28 %). The size of the papillomas is also smaller during the colder seasons of the year (up to 300 mm3) reaching a maximum in August/ September (up to 900 mm3). The increase in growth of the tumours follows the rise in frequency with a delay of 3–4 weeks. These seasonal fluctuations of tumour growth are possibly related to the alteration of the water temperature and oxygen

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1975.tb04617.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

An account is given of some aspects of the biology ofTilapia mossambicaPeters in Lake Sibaya, South Africa. Lake Sibaya is a warm shallow coastal lake with extensive shallow terraces in the littoral which shelve abruptly into underwater valleys. The substrate is predominantly sandy. Aquatic macrophytes are generally restricted to water 1–7 m deep. Adult fishes (over 8 cm standard length) are usually absent from water deeper than 12m and shallower than 0–5 m, whereas juveniles may occur at all depths, and fry only in very shallow water.T. mossambicainhabits the littoral and sublittoral in the warm and transition periods (August–April) but moves into deep water in the cool season (May–July). Exposed and sheltered areas are utilized for different purposes by adult fishes, the former for nesting, and latter for feeding and mouth–brooding. Habitat selection by males is governed by the availability of suitable nest sites. Nests are most common in sparsely–vegetated sheltered areas. Brooding females preferred sheltered littoral areas but ventured onto the terrace to release the fry. Juveniles and fry inhabited exposed shores with a temperature gradient which reversed diurnally. The breeding, shoaling and feeding behaviour is described. The biology ofT. mossambicain Lake Sibaya is compared to data on the same, and similar species, in other systems. The utilization of available resources in the lake byT. mossambicais discussed and reference is made to the importance of the retention of generalized characters for the successful habitation of the cyclically–renewed habitat of

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1975.tb04618.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

A method is described for the transport of fish resulting in very few or no mortalities during or after this procedure. Commercial salt is added to the water to give a final conentration of 0–5 %, compressed air is bubbled through the water and the fish are kept in ‘salt water’ after transportation to decrease the incidence of skin infec

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1975.tb04619.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

A histochemical study has been made on the myotomal musculature of the rainbow troutSalmo gairdneriRichardson. Four main types of fibre can be distinguished on the basis of differences in fibre size, lipid content and succinic dehydrogenase and myofibrillar adenosine triphosphatase activity (ATPase activity). Early histological studies have concluded that in addition to a superficial strip of muscle small diameter ‘red’ fibres occur throughout the trout myotome. These small diameter fibres occurring in the bulk of the myotome are shown to differ from the superficial fibres with respect to their oxidative metabolism and myofibrillar ATPase. The relevance of this finding to studies on the energetics and swimming efficiency of this species are discus

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1975.tb04620.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Some aspects of anaerobic metabolism in the red and white (mosaic) muscles of the rainbow trout have been studied during environmental hypoxia. Evidence has been obtained for the operation of anaerobic pathways other than glycolysis, especially in the superficial red muscle. L‐alanine and succinate were observed to accumulate as anaerobic endproducts in this tissue. Anaerobic glycolysis also increased significantly during hypoxia, but only in the white muscle. Glycogen stores were depleted by 70–85 % in both red and white muscle. Glucose increased in concentration in the red but not in the white muscle. In an attempt to understand some of the species differences in the susceptibility of fish to hypoxia the results of the present study have been compared with an earlier study on the carp (Johnston, 1975). The effect of death from hypoxia on the levels of muscle metabolites has also been stud

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1975.tb04621.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Specimens ofCottus gobioandNoemacheilus barbatulusfrom the River Avon, Hampshire, were examined between July 1970 and July 1971. Both fish were found to act as hosts forNicolla gallica(adult),Pomphorhynchus laevis(adult) andTriaenophorus nodulosus(plerocercoid). The incidence and intensity of infection were lower inN. barbatulusthan inC. gobio, and this was related to differences in host diet. A small number ofN. barbatuluswere also found to harbourProteocephalus torulosus. Seasonal cycles of incidence and intensity were evident inN. gallica, with a peak occurring in the winter.P. laevisandT. nodulosusshowed no such cycles. Increasing host size was associated with a higher infection of bothN. gallicaandP. laevis, but notT. nodulosus. The diet of the host was considered to be important in influencing this increase. Differences in host reproductive condition affected the population levels ofN. gallicaonly, where an increased parasite burden was evident in gravid female fish. This was considered to influence the observed increase in incidence and intensity of this parasite during the winter. None of the parasites showed any seasonal maturation cycles. There was no evidence of any interactions between the parasite populations. Host diet and the availability of infective larvae were considered to be the most important features influencing the number of parasites which became established, and the rate at which this occurred. Temperature probably acted indirectly on the establishment ofN. gallica, by controlling the availability of the larval stages, and also, by influencing the host reproductive condition, on the length of time for which the parasite was retained by the host.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1975.tb04622.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

Ulvaria subbifurcatais found on the north‐east Atlantic coast of North America. Fish less than 55 mm preyed predominantly on copepods, while larger ones ate mainly nereids; polynoids and amphipods were eaten by all sizes. These four food items comprised the main food of the radiated shanny. Spawning occurred in May with the fish first spawning at age three to five. No conspicuous secondary sexual characters were observed. Females spawned once per year, producing a demersal egg mass. Males spawned up to four times and tended the egg mass (or masses). Incubation lasted 35–40 days, and the pelagic larvae settles on the bottom by August. Adult males tended to be larger than females of the same age but little difference was found sexually in the length–weight relationships.Ulvaria subbifurcatalarger than 60 mm are nocturnal. This may reduce predation by, and competition with, other inshore benthic f

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1975.tb04623.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

The effects were studied of a 24 h exposure to a subacute concentration of parathion (0.33 p.p.m., which is approximately equivalent to 0.5 of the 48‐h LC50) on the locomotor orientation of mature goldfishCarassius auratusL., 26–30 cm long, in response to a food odour and a water flow differential, singly and in combination, in a free choice situation. Prior to exposure, food odour alone was significantly attractive but the combination ‘food odour with increased water flow’, as compared with the control situation, was avoided. Factorial analysis demonstrated interaction between odour and increased flow. After exposure to parathion the food odour ceased to be attractive and was significantly avoided. This avoidance was not present in the ‘food odour‐increased flow’ combination. The parathion exposure did not affect the response to the flow conditionsper sebut reversed the interaction between food odour and increased flow. In addition, the exposure to the pesticide itself, in a second order interaction, interacted with ‘food odour‐flow’ response. Hence, the short term exposure to the subacute organophosphate concentration affected not only the perception of food odour and flow individually, but also the interaction between these common en

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1975.tb04624.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

This paper describes the determination in rainbow trout of the normal levels in the plasma of eight enzymes known to be significant in animal pathology. Some relationships between plasma enzyme levels and the enzyme activities in selected tissues are discussed. For LDH which is ubiquitously distributed, we chose, by way of saturation tests, the optimum concentrations of pyruvate and NADH in the assay medium. The LDH ‘isoenzyme ratio’ was determined for heart tissue, liver, and white muscle. When blood was withdrawn from caudal vessels, we observed a net increase of plasma enzyme activities, mainly of CPK and LDH, which was demonstrated to originate from surrounding muscle. Thus cardiac sampling was the only suitable way of obtaining blood for this kind of study. Slightly haemolyzed blood appeared suitable for enzyme determinations except for Alk Pase which is about 50 times more concentrated in erythrocytes than in plasma. CPK was highly concentrated in the heart and the muscle, GOT was concentrated in the heart while the liver appeared to be a valuable source of GDH (as well as the kidney) and

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1975.tb04625.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY

摘要:

It was shown experimentally that at 22°C, adultTilapia rendallican descend to a maximum compensation depth of 8.5 m and thatTilapia sparrmannipenetrate to a maximum depth of 15m. AdultHemihaplochromis philandermales can descend to 16m, and females to 26m at 22°C. At 30°C, the rate at which‐pressure compensation occurred and the maximum depth reached was increased. Fry and juveniles were able to penetrate to greater depths and to descend more rapidly than ad

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1975.tb04626.x

出版商:Blackwell Publishing Ltd    

年代:1975

数据来源: WILEY