摘要:

Glass eels and elvers of the American eel were negatively buoyant. Those adapted to sea water were more dense (1.072 ± 0.001 g cm−3) than those adapted to fresh water (1.061 ± 0.001 g cm−3). Adaptation to fresh water increased relative body water content, but did not account for the observed decrease in total body density. Histological examination revealed the presence of a potentially functional swimbladder in the glass eels, although this hydrostatic organ did not becomegas‐filled until after freshwater residency had occurred. Calculation of lift as used in the selective tidal transport mechanism suggests that hydrodynamic compensation for horizontal swimming during the estuarine phase of migration is energetically a

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03792.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Plasma corticosteroid concentrations in channel catfish,Ictalurus punctatus, (normally 1.0 ± 0.3 μg/100 ml) increased significantly (to 5.9 ± 1.2μg/100 ml) in response to acute oxygen depletion and then returned to control levels within 30 min after the dissolved oxygen concentration was increased; however, a secondary increase in plasma corticosteroid levels was observed 6 h after exposure. Corticosteroid levels also increased in fish exposed to dissolved oxygen concentration of<0.2 mg/1 for three days. Methylene blue was not effective in preventing interrenal response to low dissolved oxygen. No diurnal plasma corticosteroid rhythm was observed in fish exposed to diurnal chemical rhythms of culture po

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03793.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The absorptive cells lining the mucosa of the intestine, caeca and rectum of farm‐reared adult rainbow trout (Salmo gairdneriRich.) were studied by light and electron microscopy. Most of the intestinal absorptive cells showed morphological characteristics of lipid absorption. The cytoplasm of a few cells was closely packed with mitochondria. The caecal absorptive cells resembled those of the intestine but contained more apical dense bodies and more complex lamellar structures which, in conjunction with the intercellular spaces, appeared to play more active roles in lipid absorption. The rectal lumen was divided into peripheral and central parts by the complex mucosal folds. The surface of the peripheral part was mostly lined by vacuolated cells except for small patches of non–vacuolated (generative) cells between the bases of the folds. The central lumen was lined mainly by a second type of non‐vacuolated cell. The vacuolated cells showed structural indications of a function of absorption of protein macromolecules.There is morphological evidence to suggest that the pattern of absorption of lipids and proteins in the adult rainbow trout is similar to that demonstrated in stomachless teleosts and that both intraluminal and intracellular digestion of proteins co‐exist in this

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03794.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

The respiratory mechanisms of a shallow‐water, marine and estuarine flathead,Platycephalus fuscusC.&V. are described. Morphological and behavioural adaptations enabling respiration while the fish is buried in fine, unconsolidated sediments are investigated and related to the ecology of the specie

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03795.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Portions of the livers of fingerling rainbow trout were studied by light and electron microscopy. The histology, cytology and ultrastructure of mesothelial cells, serosal fibroblasts, hepatocytes, sinusoidal endothelial cells, endothelial cells of central veins and blood cells were described. Mesothelial cells and fibroblasts constituted a very thin capsule. Hepatocytes contained extensive areas of rough surfaced endoplasmic reticulum, consisting mainly of parallel cisternae and pools of glycogen. One or two nuclei and numerous mitochondria occurred in the areas of endoplasmic reticulum, but never in the pools of glycogen. Hepatocyte surface possibilities included hepatocyte to hepatocyte, hepatocyte to bile canaliculus, hepatocyte to space of Disse and hepatocyte to serosa. The trout liver was compared compared to channel catfish liver and to rat liver. Functional implications of the structural features were discussed.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03796.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

During metamorphosis from the yellow to the silver phase inAnguilla rostrata, the length of the swimbladder retial capillaries increases by a factor of 2.5, the mean retial capillary lumen diameter and total retial cros‐sectional area increase by 1.5 and the calculated counter current exchange efficiency increases by 3.4. Metamorphosis of the retia begins before changes in integument pigmentation become apparent. These changes in retial morphology are part of a complex of transformations that permit. The maintenance to swimbladder function at greater depths during the spawning migratio

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03797.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Pre‐exposure of rainbow trout,Salmo gairdnerito sublethal levels of arsenic or cyanide, resulted in significant changes in the incipient lethal levels of the respective toxicants. Fish gradually increased their tolerance to arsenic (as arsenite) by 47% during a three week preexposure to 0.22 of the incipient lethal level. Mean whole‐body aresenic concentrations increased from 2 to 27 μg g−1dry weight during the first week, then decreased to a stable level of 15 after two and three weeks. Fish decreased their tolerance to cyanide (as HCN) by 32 and 15% after one and two weeks of pre‐exposure to 0–35 of the incipient lethal level. This initial sensitization disappeared after three weeks. Renal tubular parenchymatous oedema was observed after two and three weeks of cyanide pre‐exposure. Neither arsenic nor cyanide affected growth at these levels of

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03798.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Sub‐adult channel catfish,Ictalurus punctatus, were exposed to sublethal hypoxia for 24, 48 or 72 h. Haematological parameters were used to assess the physiological state of the catfish subjected to prolonged, sublethal hypoxia. Haemoglobin, mean corpuscular haemoglobin, mean corpuscular haemoglobin concentreation, plasma lactic acid and plasma glucose deviated significantly from control values in channel catfish exposed to hypoxia for 24, 48 or 72 h. Haematocrit, total plasma protein, total erythrocyte counts, total leukocyte counts mean corpuscular volume and differential leukocyte counts were not sensitive indicators to the catfish's physiological status. After five days, of reacclimation to oxygen levels saturation, channel catfish continued to exhibit haematological responses to prolonged hypoxi

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03799.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Twenty four marine fish species of the Gulf of Thailand were studied. The results suggested that increased acclimation temperature resulted in increased mean avoidance temperature (AT), critical thermal maximum (CTM) and upper incipient lethal temperature (UILT). At the acclimation temperature, which is normally the ambient seawater temperature of the Gulf of Thailand (28° C), the upper incipient lethal temperature ranged from 34° C to 37–5° C.Monocanthus chinensisandCynoglosus puncticepshad the lowest thermal resistance.Mugil dussumerii, Therapon theraps and Scatophagus argusthe highest and the rest in the middle r

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03800.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

A comparison of mean trawl catch rates (kg/h) from 128 collections in 1969 and 1970 and 63 collections in the fourth quarter of 1976 showed the following changes.1A reduction in mean total catch rates at all seven depth intervals from 1970–1976.2Reductions of 6.8, 6.1, 3.9, 6.2, 1.5, 2.9 and 5.9 times from shallow to deepest 10m depths respectively.3No Tilapiu esculenfu were collected in 1976.The trend that emerges shows a marked reduction in mean total trawl catch rates in the Kenya waters of Lake Victoria which should sound a note of caution for proponents of a mechanized fishing industr

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1981.tb03801.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY