A simple and inexpensive spawning and egg collection system for fish with pelagic eggs

A spawning and egg collecting system for fish with pelagic eggs is described and discussed. The spawning unit is a 175 m³ submersible plastic pen supported by a polyethylene floating collar. The eggs are collected by rotating the water column in the pen and placing a net in the rotating water. The system is inexpensive and easy to operate. Temperature and illumination control are feasible.The quantity collected in the 1981 spawning season was 138 million eggs. Obtained eggs were of good quality. The theoretical spawning potential of the brood stock was 271 million eggs. This difference was mainly ascribed to suboptimal collection, but also to incomplete spawning and sinking of unfertilized and dead eggs.     

The cytochrome P450 system of Atlantic salmon (Salmo salar): II. Variations in hepatic catalytic activities and isozyme patterns during an annual reproductive cycle

A group of Atlantic salmon (Salmo salar) was followed through their first year of maturation and spawning. At monthly intervals, starting with juvenile fish in December, 5–7 fish of each sex were killed, and liver and plasma were sampled. The last sampling point was of spawning fish in November a year later. Variables in the cytochrome P450 (P450) system were studied in hepatic microsomes, and estradiol 17 was measured in the plasma of females to assess the maturational status. The P450 1A1-mediated 7-ethoxyresorufin O-deethylase (EROD) started at high levels in winter, but decreased to non-detectable activities in pre-spawning females. Decreases, but not to the same extent, were also observed during this period in total cytochrome P450, cytochrome b₅, NADPH-cytochrome P450 reductase, and in the content of two immunochemically determined P450 isozymes. At the same time, LSI levels increased in maturing females (starting in July), and GSI levels increased in both sexes (starting in May). Sex specific differences were observed in pre-spawning fish in September and October, with levels of total P450, b₅, NADPH-cytochrome P450 reductase, EROD and P450 isozymes significantly lower in females. At the same time, plasma estradiol-17 levels reached peak values in females. The results point to the important role of sex steroids such as estradiol-17 as major factors in the regulation of final sexual maturation. However, this study also indicates that there may be estradiol-17 independent events of equal importance in the early stages of gonadal maturation that may involve the P450 system. The changes observed in the P450 system (as a major drug and steroid metabolizing system) of Atlantic salmon during sexual maturation may be of importance both in the endogenous transduction of hormonal signals, and as a pharmacological basis for designing therapeutic treatment of diseases in the aquaculture industry.Parts of this work were presented at the 5th International Symposium on Responses of Marine Organisms to Pollutants, April 1989 in Plymouth, United Kingdom (Larsen and Goks\/oyr 1989).     

Tenerife's freshwater macroinvertebrates: Status and threats (Canary Islands,Spain)

• 1 This paper lists 171 freshwater macroinvertebrate taxa from Tenerife (excluding chironomids) based on this study and other published information. Canarian endemism and a Mediterranean origin are dominant features in the data set. At least 14 species are Tenerife endemics. Endemism is especially high in the Diptera, Trichoptera and Coleoptera.
• 2 Extensive investigations were carried out at 57 sites in six different habitat categories and from at least two seasons. The most species-rich habitats were those with permanently running water, a biotope that is rare and diminishing in Tenerife.
• 3 The principal threat to freshwater environments is an increase in human exploitation of the water resources, which, if it is not moderated, will cause extinctions in the near future. Taxa that do not favour man-made canals are especially at risk—a risk that is increased by the small number of populations. These include the Canarian endemics Wormaldia tagananana, Tinodes canariensis (Trichoptera), Dixa tetrica (Diptera) and Baetis pseudorhodani (Ephemeroptera). Thirty-nine species were found at five or fewer sites.
• 4 Some species can survive in intermittent streams, although we found less than half of the taxa present in this habitat, indicating the extent of the diversity reductions that might be expected to follow the drying up of permanent streams.
• 5 Species living in the thin film of water in the madicolous habitats are similarly at risk. Three Canarian endemics were found exclusively in this habitat: Hydrotarsus pilosus, Limnebius punctatus (Coleoptera) and Satchelliella binunciolata (Diptera).
• 6 As a first step, protective measures are proposed for five of the most species-rich streams. If these were to be implemented, they would make a significant contribution towards maintaining biodiversity in the fresh waters of Tenerife.

     

Distribution and induction of cytochrome P450 1A1 in the rainbow trout brain

Cytochrome P450 (CYP) 1A1 participates in the activation as well as detoxification of environmental pollutants such as aromatic hydrocarbons. This CYP form is also efficiently induced by aromatic hydrocarbons. The presence of CYP 1A1 in the brain might thus be of physiological and toxicological importance. In the present investigation on rainbow trout, the distribution of 7-ethoxyresorufin-O-deethylase (EROD) activity, a cytochrome CYP 1A1 catalyzed reaction, was measured in whole tissue homogenates from brain parts. In control fish, a relatively high activity was found in the rainbow trout olfactory bulb compared to the other brain parts. Although an EROD induction (3 to 7-fold) by β-naphthoflavone (BNF) was recorded in all brain parts from the rainbow trout, the highest induced activity was measured in the olfactory bulbs. To ascertain the distribution of EROD activity in cells, whole brain tissue was subfractionated by differential centrifugation. The fractionation scheme separated mitochondria (P2 fraction) and microsomes (P3 fraction) as determined by marker enzymes and electron microscopy. In control rainbow trout, a low EROD activity could be measured in the P2 fraction. BNF induced the EROD activity in both P2 and P3 fractions. Western blotting showed the induction by BNF of a protein band in the P2 and P3 fractions with a molecular mass around 58,000 when highly specific anti-cod CYP 1A1 antibodies were used. ELISA measurements confirmed the induction of CYP 1A1 protein in the rainbow trout brain subcellular fractions.     

摄食促进剂对对虾生长的影响

IntroductionMeasures to assure that all feed offered to animals in commercial operation is consumed and to reduceformulated feed waste pollution,have been considered as some of the most relevant for lowering productioncosts in aquaculture.Considering the importance of chemical stimulant in development of the crustacean lifecircle,it is logical to assume that by adding attractants to the feed,the animal would rapidly find potentialfeed and ingest it.Additionally,measures involving the incorpora…     

Changes in arterial PO₂, physiological blood parameters and intracellular antioxidants in free-swimming Atlantic cod (Gadus morhua) exposed to varying levels of hyperoxia

Free-swimming Atlantic cod (Gadus morhua) were exposed to water oxygen pressures (P _wO₂) ranging from 18.1 to 41.5 kPa and sampled for blood using an indwelling caudal artery cannula. Arterial blood oxygen pressure (P _aO₂) increased with increasing P _wO₂, from 12.0 kPa in normoxia (18.1 kPa) to 34.2 kPa in the highest hyperoxic level tested (41.5 kPa). Blood CO₂ pressure and plasma bicarbonate concentration increased with P _wO₂, indicating reduced ventilation with increased P _wO₂. Plasma glucose, sodium and potassium were not affected by water oxygen level. Blood oxidative stress biomarkers, reduced glutathione, oxidized glutathione and the oxidative stress index (ratio between oxidized and total glutathione) differed intermittently between normoxia and hyperoxia. The oxidative stress index was higher in the blood of exposed compared to unexposed control cod. Together with elevated P _aO₂, these findings suggest increased production of reactive oxygen species and increased oxidative stress in Atlantic cod exposed to hyperoxia.     

The use of historical collections to estimate population trends: A case study using Swedish longhorn beetles (Coleoptera: Cerambycidae)

Long term data to estimate population trends among species are generally lacking. However, Natural History Collections (NHCs) can provide such information, but may suffer from biases due to varying sampling effort. To analyze population trends and range-abundance dynamics of Swedish longhorn beetles (Coleoptera: Cerambycidae), we used collections of 108 species stretching over 100 years. We controlled for varying sampling effort by using the total number of database records as a reference for non-red-listed species. Because the general frequency of red-listed species increased over time, a separate estimate of sampling effort was used for that group. We observed large interspecific variation in population changes, from declines of 60% to several hundred percent increases. Most species showed stable or increasing ranges, whereas few seemed to decline in range. Among increasing species, rare species seemed to expand their range more than common species did, but this pattern was not observed in declining species. Historically, rare species did not seem to be at larger risk of local extinction, and population declines were mostly due to lower population density and not loss of sub-populations. We also evaluated the species’ declines under IUCN red-list criterion A, and four currently not red-listed species meet the suggested threshold for Near Threatened (NT). The results also suggested that species’ declines may be overlooked if estimated only from changes in species range.     

Prey‐type‐dependent foraging of young‐of‐the‐year fish in turbid and humic environments

Abstract – Fish, which are generally visual foragers, experiences reduced reaction distance in visually degraded environments, which has consequences for encounter rates with prey. Small prey is detected at shorter distances than larger prey, and piscivores are therefore predicted to be more strongly affected by visual degradation. In experiments, roach (Rutilus rutilus) were fed two plankton prey types and pike (Esox lucius) were fed Daphnia and larval roach, in clear water, algal turbid water and water coloured brown by dissolved organic matter (DOM). Planktivorous foraging in roach was not affected by visual degradation, while pike foraging on both Daphnia and larval roach was. Pike showed increased reaction distance to Daphnia in visually degraded water, while it was severely reduced with roach as prey even if the visual range was not reduced below pike reaction distances in clear water. Pike foraging on Daphnia was not affected, but when foraging on roach, the reduced search efficiency was counteracted by increased attack rates. However, there was no increase in movement and no difference between turbid and DOM treatments. Effects on piscivores will likely become more pronounced at later life stages as prey size and the reliance on long‐distance detection increases at the same time as changing climatic conditions may further deteriorate the visual conditions in future.     

PPR‐B‐31: a new maintainer allele in the male‐fertility restorer gene of radish (Raphanus sativus) Ogura cytoplasm

The PPR‐B gene is responsible for male‐fertility restoration of the Ogura‐type male‐sterile radish plants, and it is located in the complex Rfo locus in the vicinity of similar PPR‐A gene and PPR‐C pseudogene. The aim of this study was to identify PPR‐B alleles and understand the structure of the Rfo locus in radish breeding lines. Five lines of radish with normal male‐fertile cytoplasm were tested. The entire PPR‐B gene was amplified, sequenced and allelic PPR‐B sequences were identified. The results indicated that the maintainer lines 7, 15 and 21 contained a non‐restoring form of PPR‐B protein. A unique PPR‐B was found in lines 24/15 and 31 that are restorer and maintainer lines, respectively. The substitutions might be responsible for the loss of a restoring function of the PPR‐B‐31 allele. Amplification of the PPR‐A/PPR‐B and PPR‐B/PPR‐C intergenic regions allowed to identify rearrangements within Rfo locus. Obtained results confirm the wide allelic variation within the Rfo locus, as well as high genetic complexity of the fertility restoration mechanism in radish.     

Using perlite as a substrate carrier for measuring microbial available phosphorus by respiration kinetics in soils

The release of CO₂ by soil microorganisms after the addition of nitrogen and glucose in excess and calibration additions of phosphorus has successfully been used to assess microbial available P, assuming the native soil P pool is then limiting respiration. However, in P-fixing soils and soils with high P content, carbon can be exhausted before the available soil P pool. It is not possible to simply increase the amount of glucose as then the glucose concentration would be lethal for microorganisms. A modified method was tested where soil is mixed with perlite. It was hypothesised that perlite, having a high water holding capacity, would dilute the concentration of glucose, while maintaining the bioavailability of added nutrients, thus avoiding carbon limitation. Factorial combinations of amount of soil and perlite (both adjusted to −25 kPa water potential) were tested to examine if perlite as such had any effect on the respiration. Five tropical soil samples with a sharp gradient in P availability and one N-limited compost material were used. The method successfully reduced the risk of carbon limitation. Microbial indices, such as basal respiration, substrate-induced respiration and maximum P-limited respiration, were directly proportional to the amount of soil in the experiments but unrelated to the amount of perlite, showing that perlite did not affect microbial measurements.