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1.
Long-term changes in growth and age at maturity of mackerel, Scomber scombrus L., from the North Sea
A.-L. Agnalt 《Journal of fish biology》1989,35(SA):305-311
Mean length and mean weight at age of Atlantic mackerel in the North Sea increased significantly between 1960 and 1979, then, decreased markedly during the 1980s. In contrast, median age at maturity decreased (c. 1-1.5 years) from 1960. Median length at maturity remained stable until the 1980s, when it declined sharply. The significance of these changes is discussed in relation to variation in sea temperature, food availability and stock size. It is speculated that the changes during the 1980s resulted from immigration of western stock mackerel. 相似文献
2.
Male aggression,limited female choice and the ontogeny of mating behaviour in the flesh fly Sarcophaga crassipalpis
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J. Dylan Shropshire Darrell Moore Edith Seier Karl H. Joplin 《Physiological Entomology》2015,40(4):325-335
Previous work has shown that male flesh flies (Sarcophaga crassipalpis Macquart) exhibit an ontogeny of behaviour from eclosion through sexual maturity that includes extensive changes in the expression of aggressive, non‐aggressive interactive and non‐interactive behaviours. To determine how the presence of a female flesh fly influences the manifestation of these behaviours, male flesh flies of different ages post‐eclosion are paired with same‐age females and their behaviours are monitored in a simple arena during a 50‐min observation period. All flies are socially isolated until pairing. Although the levels of expression of aggressive and non‐aggressive interactive behaviours are depressed relative to previous findings in male‐opponent pairs, the ontogeny of aggression still occurs as indicated by a significant increase, with age, in the agonistic behaviour ‘hold’. Similar to male‐opponent pairs and individual males, the performance by males of the non‐interactive behaviours ‘walking’ and ‘standing’ diminishes, whereas ‘upside‐down’ increases with age. By contrast, ‘grooming’ shows a significant age‐related decline. No courtship behaviours are observed in the males, although the aggressive behaviour ‘hold’ is a significant transition to mating. Females show no obvious courtship or rejection behaviours, although the significant increase in ‘upside‐down’ with age could possibly be a behavioural gateway to mating. The results of this study indicate that extensive age‐related changes encompassing the entire behavioural repertoire are intrinsic to male flesh flies and persist under a variety of different social contexts. 相似文献
3.
Jianyong Wu 《Cytotechnology》1996,22(1-3):103-109
Animal cells in suspension culture can suffer severe mechanical damage from bursting gas bubbles or other hydrodynamic force sources. Certain chemical additives in the culture media, particularly some surface-active chemicals, can effectively protect animal cells against such damage. Previously we proposed that the protective effect is associated with the adsorption of the additives in the cell membrane through hydrophobic binding of the surface-active molecules to the membrane. Adsorption of the additives to the cell membrane may lead to decreased hydrophobicity of the cell surface, thus eliminating cell adhesion to bubbles and reducing cell damage from bursting bubbles. In this study, we measured the hydrophobicity of two insect cell lines based on cell adhesion to hydrocarbon phase and its influence by surface-active chemicals, Pluronic F68, a methylcellulose and a polyethylene glycol. The experimental results showed strong support for the aforecited cell protection mechanism. 相似文献
4.
Empirical relationships are presented to estimate in fishes, asymptotic length (L∞) from maximum observed length (Lmax ), length at first maturity (Lm ) from L∞ , life span (tmax ) from age at first maturity (tm ), and length at maximum possible yield per recruit (Lopt ) from L∞ and from Lm , respectively. The age at Lopt is found to be a good indicator of generation time in fishes. A spreadsheet containing the various equations can be downloaded from the Internet at http://www.fishbase.org/download as popdynJFB.zip. A simple method is presented for evaluation of length–frequency data in their relationship to L∞ , Lm and Lopt . This can be used to evaluate the quality of the length–frequency sample and the status of the population. Three examples demonstrate the usefulness of this method. 2000 The Fisheries Society of the British Isles 相似文献
5.
The light-harvesting and protective functions of carotenoids in photosynthetic membranes 总被引:9,自引:0,他引:9
Dorothea Siefermann-Harms 《Physiologia plantarum》1987,69(3):561-568
Siefermann-Harms, D. 1987. The light-harvesting and protective functions of carotenoids in photosynthetic membranes. 相似文献
6.
J. Siebel K. P. Pauls 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1989,78(4):473-479
Summary A direct comparison of microspore culture and anther culture was made in Brassica napus using F1 crosses of Regent (canola) by Golden (rapeseed), and their reciprocals, as well as a hybrid between Reston and a highly embryogenic, canola-quality breeding line (G231) as donor plants. The study confirmed that microspore culture can be ten times more efficient than anther culture for embryo production. Embryo yields from cultures initiated from the Reston x G231 were four-fold greater than those initiated from the Regent x Golden crosses, and significant differences were also detected among cultures initiated from the different Regent x Golden crosses. These results illustrate the influence that donor plant genotype has on embryo production. However, superior embryogenic potential among donor material was not always coincident with superior plant production. The average haploid-todiploid ratio in microspore-derived regenerates was 21 for the population obtained from the Regent x Golden crosses but 11 for the Reston x G231 cross. For both types of material, the frequency of diploids increased upon repeated cycles of explanting. A field study showed that there were no differences between the populations of anther-derived and microspore-derived spontaneous diploid and doubled haploid lines, with respect to the days required for them to flower or to mature. The information is valuable for canola breeding programs considering the use of haploidy. 相似文献
7.
Joe W. Dorner Richard J. Cole Timothy H. Sanders Paul D. Blankenship 《Mycopathologia》1989,105(2):117-128
Samples of Florunner peanuts were collected throughout a period of late-season drought stress with mean geocarposphere temperatures of 29 and 25 °C, and determinations of maturity, kernel water activity (aw), percent moisture, capacity for phytoalexin production, and aflatoxin contamination were made. Results showed an association between the loss of the capacity of kernels to produce phytoalexins and the appearance of aflatoxin contamination. Kernel aw appeared to be the most important factor controlling the capacity of kernels to produce phytoalexins. Mature peanuts possessed additional resistance to contamination that could not be attributed solely to phytoalexin production. Kernel moisture loss was accelerated in the 29 °C treatment compared to the 25 °C treatment, and data indicated that the higher soil temperature also favored growth and aflatoxin production by Aspergillus flavus in peanuts susceptible to contamination.Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products that may also be suitable. 相似文献
8.
Fumio Hayashi 《Ecological Research》1992,7(2):171-178
The life history of three populations ofProtohermes grandis and two populations ofProtohermes immaculatus (Megaloptera: Corydalidae) was compared. In general, the larvae lived in stream riffles for 2 years and the adults appeared
in summer. Adult body size differed between these closely related species and also between the populations ofP. grandis. Dwarfism occurred inP. immaculatus, a species that is endemic to the small, isolated island, Amami Island. The population ofP. grandis on Yaku Island, located between Amami Island and the mainland Kyushu, had an intermediate body size between that ofP. immaculatus and the mainland population ofP. grandis. Despite being an insular population,P. grandis on Tsushima Island had a similar body size to mainlandP. grandis. In these populations with large adults, some larvae lived in the streams for 3 years. The size distribution of benthic animals,
which are the prey available toProtohermes larvae, differed between the streams studied. The density of large prey was lowest on Amami Island, intermediate on Yaku
Island, and highest on the mainland and Tsushima Island. Different size distributions of available prey may be caused by the
differences of benthic fauna; most of Ecdyonuridae and Ephemerellidae (large mayflies) and Perlidae (large stoneflies) were
not found on Amami and Yaku Islands. Thus, there is a tendency to dwarfism in the populations ofProtobermes inhabiting streams where the density of large prey is low. 相似文献
9.
I J O'Donnell J K Dineen T L Rothwell R C Marshall 《International journal for parasitology》1985,15(2):129-136
Comparison of antisera from sheep during primary infection and following vaccination and challenge with Trichostrongylus colubriformis, with antisera obtained following primary infection of high- and low-responder guinea pigs, failed to reveal different antigenic patterns in proteins separated from fourth stage larval extracts by two-dimensional electrophoresis and probed by the immunoblot technique.Generally, serum IgG reacted specifically with worm antigens of mol. wt greater than 94,000, whereas protection against challenge infection was elicited most effectively in the guinea pig by fractions in the 67,000–94,000 range.Most distinct separations of larval proteins by SDS-polyacrylamide gel electrophoresis were obtained by extraction of live larvae and the extracts used within 2–3 days. 相似文献
10.
Synopsis
Sardinella aurita were sampled from catches of the lampara fishery at Tripoli, Libya during October 1979 through to September 1980. Landings
consisted mainly of adult fish with large (mode 21–26 cm total length), relatively fast growing 3–5-group individuals in winter
and spring and smaller (mode 14–20 cm total length), slow growing 2- and 3-group fish in summer. Gonad growth commenced in
April, when the fish were feeding on zooplankton, and continued at the expense of mesenteric fat until July. It is suggested
that the older and bigger fish spawn first, probably after having moved westwards, and that this results in spatial and temporal
differences in length at age within the population. There was no consistent difference in growth rate between the sexes, but
because first maturity in males tends to occur earlier than in females, there were length distribution differences between
the sexes in the youngest (2+) age group as sampled. 相似文献