摘要:

This study investigates cryptic coloration and the phenomenon of colour change in the sand flathead,Platycephalus arenarius(Ramsay and Ogilby), a shallow‐water marine species. The chromatophore configurations of the dorsal integument are described and the responses to a range of artificial backgrounds studied. Certain visual cues used by this species in colour change are deduced, and the existence of a linear relationship between the shade of the integument and that of the background is propose

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03804.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Electrophoretic studies of five polymorphic enzyme loci (G‐3‐PDH‐2, LDH‐I, LDH‐5, PGI‐2, PGI‐3) in brown trout from Lough Melvin in northwestern Ireland have demonstrated that the morphotypes known by the vernacular names of ‘ferox’, ‘gillaroo’ and ‘sonaghen’, are not merely ecophenotypes but represent genetically distinct and reproductively isolated populations. The results suggest that the long life and higher growth potential of ferox trout of this lake, and possibly others, has a genetic basis. These separate demes of brown trout are probably the result of multiple invasions in post‐glacial times of allopatrically derived stocks. Lough Melvin's isolated position and absence of pike,Esox lucius, and large cyprinids have probably contributed to its pristine condition. As such it is one of the few remaining examples of what may once have been a widespread situa

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03805.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Whereas spring salmon,Oncorhynchus kisutch, from Lake Ontario had no overt thyroid goiters, comparable Lake Erie spring salmon had a 44% goitre incidence. Goitre incidence in sexually precocious ‘jacks’ from Lakes Ontario and Michigan was 43–45% and 100% in ‘jacks’ from Lake Erie.All fish displayed thyroid hyperplasia. The degree of hyperplasia (as indicated by thyroid follicle colloid content, thyroid follicle size and shape and thyroid follicle epithelial cell size) in Lake Ontario fish tended to be greater in the ‘jacks’ than in the spring fish; the reverse was true in Lake Erie fish. Serum total L‐thyroxine (T4) concentrations in Lake Ontario spring fish were higher than in any other group. There were no differences in serum T, levels between the groups of ‘jacks’, nor were serum T, levels in ‘jacks’ and spring salmon from Lake Ontario significantly different. Serum total triiodo‐thyronine (T) concentrations in Lake Ontario spring salmon were significantly higher than in all other groups and that in Lake Erie spring salmon greater than in all groups of ‘jacks’. Serum T, levels in Lake Ontario ‘jacks’ were higher than in Lake Erie ‘jacks’. Serum free fatty acid (FFA) and cholesterol levels showed significant interlake differences with lower levels present in Lake Erie salmon. Lake Erie ‘jacks’ appeared to have fewer and less well vacuolated pituitary gonadotropic basophils than ‘jacks’ from Lakes Michigan and Ontario. Putative thyrotrop cells appeared to be more numerous and more active in the Lake Erie spring salmon compared with Lake Ontario spring salmon. Prolactin, corticotrop and melanotrop cells appeared les

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03806.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Diseased American eels,Anguilla rostrata, were collected from an eel culture facility in South Carolina and examined. The disease was characterized by skin lesions located on the body. A bacterium identified asAeromonas salmonicidawas isolated from the lesions and shown to be the causative agent. The bacterium was also isolated from the kidney during later stages of the disease.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03807.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The nucleotide triphosphate/haemoglobin (NTP/Hb) and nucleotide triphosphate/red cell (NTP/cell) ratios of rainbow trout increased during prolonged starvation. A decline was noted in blood lactic acid concentration. Red cell count, haemoglobin concentration and haematocrit also declined. Changes in mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC) were found not to be significant. The NTP/Hb and NTP/cell ratios of both fed and starved trout rose seven days following a 15% reduction in blood volume by cardiac puncture. A rise in whole blood NTP concentration was found only in the bleeding response of fed animals. No significant change was noted in blood lactic acid concentration. The decline in haematocrit was significant only in the starved group. In both groups, however, red cell count and blood haemoglobin concentration fell. MCV rose whereas MCHC declined in all bled animals. Changes in MCH were not significant in either group. Negative correlations were noted between red cell count and both the NTP/Hb and NTP/cell ratios and between haemoglobin concentration and the NTP/Hb ratio. Positive correlations were seen between the two ratios and between red cell count and haemoglobin concentration.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03808.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Sand gobies (Pomatoschistus minutus) collected from beaches with a large tidal range (Scotland) exhibit a circatidal rhythm of activity in constant conditions in the laboratory. There is no endogenous circadian component to the rhythm. The phasing of the rhythm is such that peak activity occurs at the predicted time of ebb tide. Light‐dark (LD) cycles applied in the laboratory have a marked effect on activity greatly enhancing it at night so that the original tidal rhythm becomes nocturnal. Some evidence was obtained that LD cycles can entrain a weak nocturnal circadian rhythm in fish removed from tidal conditions. Contrary to expectations, some fish from beaches with a small and unpredictable tidal range (Oslofjord, Norway) also show a weakly persistent circatidal thythm without an endogenous circadian component, but great variability was noticed between individual fish. Laboratory LD cycles did not entrain a persistent circadian rhythm in the fish from the Oslofjor

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03809.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Bucephaloides gracilescensmetacercaria is a common encysted trematode parasite of whiting,Merlangius merlangus(L), haddock,Melanogrammus aeglefinus(L), and hake,Merluccius merluccius(L), in the Irish Sea. The incidence of infection over an 18‐month period was uniformly high (whiting, 95%; haddock and hake, 100%). The major site of infection in all three hosts was the cranial fluid surrounding the brain. Large numbers of cysts were also found embedded in the spinal nerves posterior to the anus in haddock and hake and in the auditory capsules in whiting and haddock. Other sites of infection included the spinal canal, cranial nerves (V, VII, VIII, X), eye muscles, orbits and nasal region. Results are discussed in the light of previous records of gasterostome trematodes in the Gadida

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03810.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Communities of metazoan parasites in ten species of fishes from Cold Lake, Alberta are described and compared. Relative abundances in the overall community of parasites in the lake were estimated using data on abundance in each host species, plus estimates of the relative abundances of the species of hosts. Parasites of the numerically dominant salmonid fishes dominated the overall community, with over half of the individual parasites beingMetechinorhynchus salmonis. Exchange of parasites between host species was greatest between related and/or abundant host species. Parasite communities in cisco and whitefish,Coregonusspp., were relatively rich in species and diverse (Simpson's index) compared with communities in those species in other lakes in North America; communities in lake trout,Salvelinusspp., and the non‐salmonid fishes were poor in species and low in diversity compared with communities in other lakes. Parasite species overlaps (Jaccard index) between related host species in Cold Lake were greater than overlaps within host species between lakes. The same pattern is seen in data from some other lakes. These features support the hypothesis of Wisiewski (1958); that the parasite community within an ecosystem is characterized by parasites of the numerically dominant host

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03811.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Myofibrillar ATPase activity was measured in the epaxial musculature of rainbow trout acclimated to 5 and 21.°C, and goldfish acclimated to 5 and 30°C. The acclimated goldfish showed considerable differences in the specific activity and thermostability of this enzyme. However, such alterations were not apparent in the acclimated trout. The evolutionary implications of these findings are discusse

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03812.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The effects of growth inhibiting factors on the total lipid content of zebrafish was studied. Crowded zebrafish were subjected to extraction of the aquarium water using activated charcoal. Control fish were crowded, but were not subjected to extraction. This resulted in a gain in mean wet weight of 10.9% for the crowded, extracted fish (experimentals) as compared to the controls. In order to determine the effects of crowding on the total lipid content of the crowded fish, lipid analyses were conducted at the conclusion of the growth studies. These studies indicate that the fish in the extracted system had a greater lipid content than those in the‐non‐extracted system (15.4% v. 10.4% mean lipid). It is proposed that growth inhibiting factors libeerated from the crowded fish may affect the thyroid gland, causing lipid mobilization from the tissues resulting in resulting in lowered total lipid in these animals. Extraction of the aquarium water with activated charcoal removes the growth inhibiting factor, possibly decreasing thyroid function with a resulting higher total lipid cont

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03813.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY