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  • 1
    Electronic Resource
    Electronic Resource
    Life-history analysis in “physiological” compared with “sidereal” time: An example with an amphipod (Gammarus lawrencianus) in a varying environment (1990)
    Springer
    Marine biology 107 (1990), S. 129-139 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The multivoltine, estuarine amphipodGammarus lawrencianus has four generations per year in an environment where temperatures range seasonally from −1° to 25°C. Temperature-response curves for rates of brood production and development were determined by laboratory experiments and field observation. The life history and population dynamics were observed over a full annual cycle (1981) for a field population located at Rocky Run, Porter's Lake, Nova Scotia, Canada. On a natural (i.e., sidereal) time scale, the generations appear to have very different life histories: the two summer generations have short lives, rapid development and mature at small size (classicr-selection), whereas the overwintering generations have relatively low rates of mortality, slow development and mature at large size (classicK-selection). This pattern (larger size at maturity at lower temperatures) is widespread in aquatic poikilotherms. Similar life-history differences are evident among cohorts of the summer generations that mature at different temperatures. When time is expressed on a physiological scale that removes the effect of temperature on embryonic development and reproductive rate, the variation within and among generations is greatly reduced. In particular, an apparent alternation betweenr- andK-selection largely disappears. Because the generations are temporally isolated, it might be surmised that natural selection acting on the summer generations might antagonize the effects of natural selection acting on the fall and winter generations. However, the scaling of the rates of development, maturation, growth, reproduction and mortality on the physiological time scale derived from the temperature dependence of development and reproductive rate gives a very different and more homogeneous pattern.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01313250
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  • 2
    Electronic Resource
    Electronic Resource
    Choosing between darkness and light: The ecological genetics of photic behaviour in the planktonic larva of Spirorbis borealis (1974)
    Springer
    Marine biology 25 (1974), S. 311-317 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The light-dark preference of individual Spirorbis borealis larvae was measured by the relative amount of time spent in the lighted half of a container. Specimens taken from a tidal pool were 20% more photonegative than those obtained outside the pool, probably because of natural selection against being washed out of the pool at high tide. The between-population behavioural difference was maintained in the laboratory, and is genetic in origin. Applying biometrical genetic analysis to larvae grouped into half-sib families, the within-population variation was used to estimate an upper limit to the heritability of 0.36. It is concluded that the differences among populations greatly exceed heritable variation within populations. A numerical selection model based on the estimated maximum heritability suggests, however, that the populations could diverge by 20% in less than a year, in response to local differences in the selection regime.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00404973
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  • 3
    Electronic Resource
    Electronic Resource
    Genetic analysis of shell-shape variation in Littorina saxatilis on an environmental cline (1975)
    Springer
    Marine biology 30 (1975), S. 227-237 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Three shell-shape parameters of Littorina saxatilis were measured and found to vary in a regular pattern with distance up an estuary. The translation rate of the shell increased, the rate of whorl expansion decreased and the circularity of the aperture decreased proceeding from the exposed shore to the protected shore. The genetic variance of these traits was estimated from the full-sib covariance and the motheroffspring covariance. The genetic variance of the translation rate and the circularity of the aperture was low in all populations, but the genetic variance of the rate of whorl expansion was high on the exposed shore and low on the protected shore. It is argued that the change in mean phenotype of these traits is the result of natural selection produced by varying degrees of wave action and desiccation. The observed genetic variance is consistent with the theory that a trait under selection will show little additive genetic variance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00390745
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  • 4
    Electronic Resource
    Electronic Resource
    Development of polymorphic microsatellite DNA loci for characterizing Oreochromis shiranus subspecies in Malawi (2000)
    Oxford, UK : Blackwell Science, Ltd
    Journal of applied ichthyology 16 (2000), S. 0 
    Details
    ISSN: 1439-0426
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Six sets of microsatellite primers were developed from Oreochromis shiranus nuclear DNA. These cross-primed in species of the genera Sarotherodon and Tilapia, and were polymorphic in most of the species. The total number of alleles ranged from 18 to 30 per locus; the mean heterozygosity per population ranged from 0.51 ± 0.12 to 0.82 ± 0.03, which is higher than reported in allozyme studies. Five sets of primers were used to characterize five putative populations of O. shiranus, an indigenous mouth brooding tilapia which has been widely distributed in fish farms and reservoirs in Malawi. Two postulated subspecies of O. shiranus (subspecies shiranus and subspecies chilwae) have been difficult to distinguish morphologically. Lake Chilwa, Lake Chiuta and Bunda Reservoir populations cluster together as O. sh. chilwae, while the Lake Malombe and Bishop Reservoir populations form a second cluster as O. sh. shiranus. The assignment of the Chiuta and Chilwa populations of O. sh. chilwae to a single subspecies is consistent with the fact that the two lakes were a single open lake until about 8000–9000 bp. There is no connection between them and the Lake Malawi-Malombe drainage system where the O. sh. shiranus subspecies is found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1439-0426.2000.00166.x
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  • 5
    Electronic Resource
    Electronic Resource
    Genetic changes in Oreochromis shiranus (Trewavas) associated with the early stages of national aquaculture development in Malawi (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: A study was carried out to investigate the genetic diversity during domestication of Oreochromis shiranus (Trewavas) and to see if it could be associated with events in the known history of aquaculture development in Malawi. Five polymorphic microsatellite loci were scored in 14 populations of O. shiranus and one population of O. mossambicus (Peters). The mean number of alleles per locus ranged from 4.4 ± 1.03 to 13.2 ± 3.31 and was higher in the wild populations than in the domesticated populations. Other measures of genetic diversity were also lower in the domesticated compared with the wild populations, and the decline in diversity was correlated with the time elapsed since the founding of the farm stocks. Ordination analysis grouped domesticated populations into three: (1) those that trace their genealogy from Lakes Chiuta and Chilwa populations and are now spread all over the country; (2) those that come from Lakes Malawi and Malombe; and (3) hybrids between O. shiranus and O. mossambicus. Genetic differentiation among farms was strongly influenced by the pattern of known exchanges among the farmers and introgressive hybridization that had occurred between O. shiranus and O. mossambicus in the farmers’ ponds. Thus, the process of genetic changes in the species subsequent to domestication are best explained and predicted by socio-economic factors that influence the behaviour of farmers, rather than by the time-and-distance models of standard population genetics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00364.x
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  • 6
    Electronic Resource
    Electronic Resource
    Test of size-specific mass selection for Nile tilapia, Oreochromis niloticus L., cage farming in the Philippines (1999)
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 30 (1999), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: One generation of mass selection based on the collimation procedure (early culling of large fry) was applied on Nile tilapia, Oreochromis niloticus L., in net cages set in Laguna de Bay, Philippines. The objective was to test the effectiveness of a low-cost, small-scale broodstock improvement procedure in this culture environment. Directional selection was performed in two steps after initial removal of large fry at 21 days. Selection of parents and testing of the offspring were also conducted in hapa net cages set up in Laguna de Bay. The selection resulted in a significant positive response of 3% relative to the control, which represents a projected 34% gain over 5 years in Laguna cage culture. The realized heritability is ≈16%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2109.1999.00340.x
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  • 7
    Electronic Resource
    Electronic Resource
    A statistical power analysis of the ‘internal reference’ technique for comparing growth and growth depensation of tilapia strains (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 49 (1996), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Experiments were conducted to compare the growth and growth compensation of three strains of juvenile Oreochromis niloticus. Ten full sib families (10 replicates) per strain were split and grown under crowded and uncrowded conditions for 3 weeks (the treatment). Both treatments were then grown an additional 12 weeks under less crowded conditions (the compensation). Standard length measurements were made at the end of crowding and the end of compensation. Each replicate included a size-matched control population of a fourth (red) reference strain. ANCOVA with the reference strain used as a cofactor revealed significant strain effects on specific growth throughout the experiment. The reference strain removed most of the random among-replicate error variance as shown by an increase of r 2 from 0.06 to 0.91 when it was included in the statistical models. If the reference fish had not been used, approximately 450 replicate families would have been needed to achieve the sensitivity of the present experiment (a difference of 7% among strains significant at P=0.05). We conclude that the CLSU strain grows significantly more slowly than the Israel and NIFI strains under the experimental conditions, that the crowding effect was essentially eliminated after 12 weeks of compensation, and that the reference strain greatly improved the resolution of the strain-testing experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1996.tb00023.x
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  • 8
    Electronic Resource
    Electronic Resource
    Behavioural and growth responses to the intensity of intraspecific social interaction among medaka, Oryzias latipes (Temminck and Schlegel) (Pisces, Cyprinodontidae) (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 37 (1990), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: When access to food is restricted, faster growing fish may be those whose behaviour is relatively unaffected by the presence of nearby conspecifics. Behavioural experiments were carried out to determine the relation between growth and motor activity levels in crowded and uncrowded conditions, and measures of aversion/attraction to groups of conspecifics. Two experimental groups of Or)-ius laripes (Temminck and Schlegel) were grown for several weeks in two environments manipulated so as to maximize differences in social interactions. In the high interaction environment (HI), food was provided inside a floating cork ring. In the low interaction environment (LI), food was spread over the container's surface. Fish were measured at the end of the growth period and tested for their activity levels in the presence of conspecifics and for their preference for, or tolerance of crowded conditions. The correlation between motor activity and growth was significantly more positive in the HI environment than in the LI environment. The relationship between preference for crowded conditions and growth was negative for both groups of fish, although less so for HI than for LI. We conclude that artificial selection for faster growth may produce more aggressive fish only under very high levels of forced social interaction (competition), if at all. Under conditions of reduced social interaction, the social-aversive or socially indifferent fish grow faster.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1990.tb02531.x
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  • 9
    Electronic Resource
    Electronic Resource
    Analysis of early growth of guppy strains, Poecilia reticulata, with different color patterns (1989)
    Springer
    Theoretical and applied genetics 77 (1989), S. 645-650 
    Details
    ISSN: 1432-2242
    Keywords: Poecilia reticulata ; Guppy strains ; Color genes ; Growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The guppy, Poecilia reticulata, is economically the most important species of freshwater ornamental fish cultured in Singapore. About 30 strains with different color patterns and fin shapes are reared in guppy farms practising monoculture in Singapore. To compare the growth rates of domesticated strains with different color patterns, newborn fry of 11 strains were obtained on the same day from a single farm in Singapore and were reared experimentally in the laboratory for about 100 days. Each strain was distributed randomly into 4 tanks with 30 fish/tank. Weekly weighings of 10 fish/tank were made from 17 to 100 days of age. Three strains were homozygous for the autosomal recessive blond gene which gives rise to a pale yellow background pigmentation (bb). These blond strains had significantly smaller body weights than corresponding ones with the same color pattern but with the wild-type grey-brown background coloration due to the dominant allele (BB). The strains with the red tail pattern due to a dominant X-linked gene (Rdt) had more rapid growth than those with other tail color patterns including the blue, black, green snakeskin and variegated. However, no significant differences were detected among the other color pattern strains. Thus among the strains studied, the blond strains were associated with slower growth while those with the red tail color were associated with faster growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00261237
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  • 10
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    Life-history analysis in ?physiological? compared with ?sidereal? time: An example with an amphipod (Gammarus lawrencianus) in a varying environment (1990)
    Springer
    Details
    Publication Date: 1990-02-01
    Print ISSN: 0025-3162
    Electronic ISSN: 1432-1793
    Topics: Biology
    Published by Springer
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