摘要:

The role of gill chloride cells (CCs) and pavement cells (PVCs) in acid‐base regulation was evaluated in brown bullhead catfish (Ictalurus nebulosus) subjected to acute hypercapnia (water Pco2=15 torr). Chronic (10 day) cortisol treatment was used as a tool to cause CC proliferation to permit a comparison of the regulatory capacities in groups of fish with widely different gill CC populations. Cortisol (4mg kg−1day−1) caused a pronounced increase (170%) in the surface area of CCs exposed to the water based on scanning and transmission electron microscope analysis. The density of PVC apical membrane microvilli was significantly increased (20%) by cortisol treatment. Exposure of either group of fish to hypercapnia caused similar changes in gill epithelial morphology including: (i) a marked reduction in the surface area of exposed CCs (52 and 78% reduction in the control and cortisol‐treated fish, respectively); and (ii) pronounced increases in PVC apical membrane microvilli density (21 and 27% in the control and cortisol‐treated fish, respectively).The rates of Cl−uptake (Jincl−) and Na+uptake (JinNa+) were elevated (150 and 262%, respectively) in the cortisol‐treated fish. Regardless of treatment, Jincl−was markedly reduced to approximately the same levels after 6 h of hypercapnia, JinNa+was stimulated in the control group and reduced in the cortisol‐treated group and thus, after 6 h of hypercapnia, JinNa+was equal in each group. The similar morphological responses in fish possessing different initial populations suggests that the predominant mechanism of acid‐base regulation during hypercapnia, reduction of C1−/HCO3−exchange, is accomplished by removal of the CC‐associated C1‐/HCO3−exchange sites from the water. The increase in PVC microvilli density during hypercapnia suggests a role for

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb00938.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Spawning time of female Atlantic cod (Gadus morhuaL.) can be predicted to within 3 days using vitellogenic oocyte diameters measured over the last month before spawning. Simulations show that a l°C drop in temperature during vitellogenesis delays spawning by about 8–10 days. Similar results were obtained with fish on low ration for 4–8 months before spawning. Moderately fed females held over two to four consecutive spawning seasons demonstrated a significant delay (⋍3–40 days) in the date of first spawning as the fish grew older and more fecund. Forecasting studies on spawning migrating Arcto‐Norwegian cod gave no evidence of a significant effect of fish length on the time of spawning. Warmer water temperature during vitellogenesis for the larger fish appears to compensate for the negative effect of fecundity On spa

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb00939.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Four species of icefishes were sampled in the Yellow River estuary of the Bohai Sea from April 1984 to April 1985 and from February 1988 to June 1989. Morphological analysis showed that they belonged to three subfamilies of Salangidae: one species from Protosalangicae,Protosalanx chinensis; two species from Salanginae,Salanx ariakensisandSalanx prognathus; and one species,Neosalanx andersoni, from Salangichthyinae, a new subfamily. External morphological characteristics, population composition, growth, maturity, food habits, longevity, fecundity, abundance and distribution of these icefishes are described. Based on these analyses, a clear outline of taxonomy, zoogeography aod biology of icefishes in the Yellow River estuary of the Bohai Sea was established.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb00940.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Aspects of the abundance, reproduction, and feeding habits ofDormitalor maculatus, Eleotris pisonis, andGuavina guavinawere assessed in the shallow waters of the Mundaú/Manguaba estuarine system, north‐east Brazil.Dormitator maculatus, the most abundant species, was caught in salinities ranging from 0·1 to 20·3 ppt and temperatures from 25·0 to 36·0° C.Eleotris pisonis, the second most abundant species, occurred in salinities from 0·1 to 18·2 ppt and temperatures from 25·0 to 33·0° C.Guavina guavinawas rare at the stations sampled. Peak gonadal development was found during the winter (wet season) inD. maculatusandE. pisonis, and probably may occur during this season inG. guavina. Size‐at‐maturity was 51 and 46 mm T.L. for males and females ofD. maculatus, respectively, and 57 and 43 mm T.L. for males and females ofE. pisonis, respectively.Dormitator maculatuswas omnivorous, and ingested primarily macrophytes, followed by sediment, and unidentified eggs;E. pisonisandG. guavinawere predaceous, with the former preying mainly upon the gastropodNeritina virginea, and the latter mainly upon the crabGoniopsis cruentata. Dormitator maculatusandE. pisonisappear to coexist because of differences between the two in microhabitat and food utilization. The two more similar species,E. pisonisandG. guavinaappear to coexist due to differences in spat

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb00941.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Three species of closely related armoured catfishes,Hoplosternum littorale, H. thoracatumandCallichthys callichtkys, are widely distributed throughout (sub)tropical South America, but a detailed inspection of collection localities in both Suriname and the South American continent reveals a clear pattern.Hoplosternum littoraleis not found in rainforest creeks and clear‐water rivers draining the Precambrium Guiana and Brazilian Shields. Here, waters are extremely poor in dissolved minerals. In salinity tolerance experiments, 1‐week‐old larvae ofH. littoralewere found to be incapable of surviving in rainwater that is also very poor in electrolytes. Probably for the same reason,H. littoraleis not collected in black‐water rivers like the Rio Negro. Within the Amazon river‐systemH. litioraleis found in sediment‐laden white‐water rivers originating in the Andes. Larvae ofH. thoracatumandC. caiiichthysare able to survive and develop further in rainwater and consequently have a less restricted distribution thanH. littorale. Both species are found in clear water and black water. All three species tolerate salinities up to 2000 mg Cl/1, and show a marked decrease in growth at l

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb00942.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The effects of very intensive exploitation on a roach stock over 5 years are estimated. The total roach catch of the mass removal carried out with trawls was 507 metric tons (195 kg ha−1, 54% of the total catch). According to the virtual population analysis the biomass of the stock has decreased from 180 kg ha−1in 1989 toc. 50 kg ha−1in 1993. The production of the stock has fallen from 64 to 33 kg ha−1. The stock is dominated by younger age groups than before the mass removal. The future development of the stock is predicted by considering different levels of natural and fishing mortality. If the exploitation is stopped totally after 1993, roach biomass is predicted to double in 3 years. A constant fishing mortality rate of 0.3 (yearly catches 45–50 metric tons) would prevent the recovery of the stock, providing that 1–year–old and older roaches

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb00943.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

High frequency (200kHz) echosounding was used to determine vertical structuring and seasonal changes in the depth distributions of limnetic fish in three New Zealand lakes. Juvenile (f.l. 30–50 mm) and large‐sized (f.l. 50–80 mm) smeltRetropinna retropinnawere segregated into discrete layers by depth in all three lakes throughout the year. Larval and post‐larval bulliesGobiomorphus cotidianus(f.l. 8–20 mm) formed a further layer between the layers of small and iarge‐sized smelt. Although the depths of the large‐sized smelt and bully layers changed on a seasonal basis, vertical segregation between the three layers of fish persisted throughout the year, even when the lakes were homothermal. Seasonal movements of fish were disrupted by the autumnal deoxygenation of the hypolimnion in Lake Rotoiti. The schools of large‐sized smelt were forced to ascend towards the layer of bullies, but segregation between these smelt and the bullies was maintained as the smelt occupied a much reduced depth range above the hypolimnion, and just below the bullies. The winter descent of bullies, which precedes their transition to a benthic existence failed to occur in Lake Rotoiti, even though the lake was fully mix

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb00944.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Anti‐proteinase activity has been found in seminal plasma of three teleost fish: rainbow trout, whitefish and yellow perch. The activity was effective against trypsin (bovine and cod) and acrosin (boar), but not bovine chymotrypsin. Inhibitor activity against fish trypsin was nine‐ to ten‐fold higher than against bovine trypsin. All anti‐proteinase activity remained in the retentate after filtration through molecular filter with 30 kDa cut‐off membrane and eluted from a column of Sephacryl S‐200 HR at the volume characteristic for molecular weight of approximately 90 kDa (data for rainbow trout). Inhibitor(s) had low thermal stability (50–60% activity remained after 15 min at 60° C). The discovery of proteinase inhibitor(s) in the seminal plasma of teleosts raised the question of the regulatory function of this protein in the systematic group of fishes having anacrosom

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb00945.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Two saithe (35 and 38 cm) and two pollack (43 and 44 cm) were tracked simultaneously for 170 h. During the day, saithe generally patrolled over the whole of an underwater reef as part of a school, making occasional excursions off the reef to another smaller reef 250m distant. At night, saithe movements were largely limited to the reef. Pollack covered less than 50% of the reef during the study period, moving only small distances off the reef. Pollack swam more slowly than saithe during the day, but at the same speed at night.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb00946.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

In this paper we present data on the breeding ecology and patterns of nest aggregation in a population ofSalaria pavo(Pisces: Blenniidae), in an area where hard substrates are very scarce. The study site was at Ria Formosa, an extensive littoral lagoon on the south coast of Portugal. The only hard materials available are bricks, tiles, stones and debris that clam culturists use to delimit their fields. The males ofS. pavoestablish nests intertidally in the holes of the bricks where they guard the eggs. Data were collected at low tide inspections of these artificial ridges and underwater behavioural observations during high tide. The main results are: (i) the same male can establish sequentially more than one nest in the same breeding season; the number of males that stay within the bricks increases before the start of the breeding season and declines towards its end; (ii) there is a large excess of mature males that do not establish nests and they are significantly smaller than the nesting males, suggesting very strong competition for nest sites; (iii) the nests of several males occur in adjacent holes of the same brick, sometimes being entirely surrounded by other nests. Thus, in this population, there is virtually no defended territory around the nest, a situation not known for other blenniid species. This pattern of nest aggregation implies both strong competition among males and reduction of aggression between neighbour parental fishes. This can be explained by the extreme scarcity and spatial distribution of available nest sites.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1994.tb00947.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY