摘要:

The balanced selective nature of protein polymorphism in fishes is reviewed, noting its diversity and association with molecular structure and size. The functional and kinetic differences between allelic variants are discussed for the few species within which they have been studied, and related to population size, habitat and clinal variation. Heterosis is discussed in relation to heterozygote excess and deficit in natural and in reared populations, and the nature of heterozygote advantage considered. Natural selection of protein loci is evidenced in changes of allele frequency with age, with experience of environmental extremes (heated effluents), and in culture. Finally, it is argued that protein polymorphism has a primarily adaptive nature, arising through selection pressures rather than through genetic drift.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02548.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

In the families produced by diallel 2 × 2 crosses there were positive relationships in two experimental groups between individual heterozygosity (H0) at four allozyme loci (PGM*,G3PDH*,sMEP*,sMDH−3,4*) and the size of the fish, their morphological variability (10 traits) and the viability among families. An integrativeH0influence on complexes of morphological traits was also obtained. On the basis of factor and discriminant analysis it was shown thatH0correlated with morphological homeostasis at least within one experimental gro

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02549.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Ten polymorphic enzyme coding loci were assayed using starch gel electrophoresis in anadromous (sea trout) and freshwater‐resident trout,Salmo trutta, from two neighbouring river systems draining into Clew Bay in western Ireland. Samples were collected from the Burrishoole and from the neighbouring Newport river system. In the Burrishoole system, two samples were from above waterfalls impassable to migratory trout, two consisted of anadromous smolts or post‐smolts and the remainder were freshwater‐resident trout from freely accessible areas. There were large differences in gene frequency between trout from above impassable barriers and all others sampled, and these two groups also differed substantially from each other. More minor differences were evident between some other samples, particularly between trout from the upper lake and streams entering it and a stream associated with the lower lake. Two anadromous populations therefore occur in the Burrishoole system. In contrast, no differences were evident in two sampling years between anadromous trout and cohabiting freshwater‐resident trout from the upper part of the Burrishoole system. Thus, in the upper part of this system, anadromous trout do not appear to comprise a separate population from non‐migratory trout and interbreeding

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02550.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Mitochondrial DNA (mtDNA) was examined in six wild populations of chum salmon (Oncorhynchus ketaWalbaum) distributed over the Primorye Region which extends approximately 1000 km along the Sea of Japan coast, and six populations from Sakhalin, using restriction enzyme analysis. By means of two restriction enzymes (BamHI andEco81I) eight mtDNA clonal lines were revealed in the 346 chum salmon studied. Mitochondrial DNA variants grouped the fish into two major clusters representing the Primorye and Sakhalin regions. Analysis of different chum salmon generations showed stability in the temporal population genetic structure in the three Primorye populations studied, but instability in the Sakhalin population of the Naiba River. We succeeded in detecting four major mtDNA clonal variants in Primorye chum salmon. The geographic distribution of clonal frequencies in Primorye populations has a clinal U‐shape associated with the north‐south axis of the Primorye region. On the whole, Sakhalin populations are less heterogeneous than Primorye ones. Two hatchery‐seeded stocks from south west Sakhalin showed no mtDNA clonal vari

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02551.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

The effects of starvation on daily growth and increment formation in the otolith were examined using a double oxytetracycline‐labelling method on larval milkfish,Chanos chanos(Forsskål), reared under different feeding regimes. The results indicated that the differences in body and otolith growth between the larvae fed once and three times a day were not significant, and that the otolith growth increment was deposited daily in both groups of fed larvae. In contrast, the starved larvae grew at a slower rate than fed larvae in body length and otolith dimensions, and the otolith growth increment in the starved larvae was not deposited on a daily basis. After undergoing starvation, the larvae were unable to recover their normal growth either in otolith increment deposition or in body and otolith growth even though they were fed. Therefore, the application of ageing techniques based on counting otolith growth increments seems to be inaccurate for starved larv

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02552.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

This paper is the first detailed analysis of situation‐specific temporal patterning of electric organ discharges (EODs) in a strong electric fish. Using a resident‐intruder paradigm EODs were recorded during interactions between dyads composed ofMalapterurus electricus(Gmelin) and four different types of fish: (1) conspecifics; (2) large prey‐type mid‐water fish, goldfish (Carassius auratus, Linnaeus 1758) and tilapia (Oreochromis melanotheron, Rüppel, 1852); (3) a sympatric competitor,Polypterus palmas(Ayres 1850) and (4) a larger, threatening catfish,Clariassp.An analysis of the EODs emitted showed that in the presence of conspecifics the average EOD volley consisted of a single long‐duration, low frequency train of EODs. The presence of the midwater fish (goldfish and Tilapia) elicited volleys consisting of two short trains, andP. palmaselicited long duration volleys with two trains and long inter‐train intervals. Finally, an attackingClariasresulted on average in volleys consisting of two high‐frequency trains of EODs. With nonconspecific partner species resident electric catfish emitted volleys with more pulses, more trains that were longer in duration and higher in frequency than the EODs in volleys emitted by intruder electric catfish with the same species

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02553.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

A detailed study on reproduction indicated that femaleC. gariepinusmature earlier (5–7 months) than femaleH. longifilis(12–14 months). In the reciprocal hybrids, female first sexual maturity was attained at 20–21 months. Both reciprocal hybrids and parental species displayed an equilibrated sex ratio. Macroscopical and microscopical observations revealed numerous abnormalities in gonadal development of the hybrids. GSI and fecundity in female hybrids were considerably lower than those found in the parental species. Moreover, intra‐ovarian tumors occurred in 20% of the hybrids. In hybrid males, GSIs were generally higher than those found in the parental species, but the spermatozoa concentration in the semen was about 100 times less. Despite these abnormalities, viable larvae, resulting from F2 and backcross fertilizations, were o

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02554.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

A karyological analysis of an artificial hybridization (reciprocal crosses) between two African clariid catfish,Clarias gariepinus(Burchell, 1822) andHeterobranchus longifilisValenciennes, 1840, was performed.C. gariepinushas a standard karyotype of 2n= 56, whileH. longifilishas 2n= 52. The hybrids revealed an intermediate karyotype (2n= 54), and it appears as if they have totalized the haploid chromosome number of both parental species, excluding gynogenesis or androgenesis. The hybrid karyotype is considered as aneuploid, although the hybrids proved to be fertile. No variation was found in the hybrids karyotypes.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02555.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Enzymatic polymorphism was examined at 13 protein loci in four African clariid catfish species:Clarias anguillaris(Linnaeus, 1758),C. ebriensisPellegrin, 1920,C. gariepinus(Burchell, 1822) andHeterobranchus longifilisValenciennes, 1840. The latter appears to be closer toC. anguillarisandC. gariepinusthanC. ebriensis. These results correspond with recently published karyological and morphometrical data.Reproductive compatibility, under laboratory conditions at least, is demonstrated betweenC. gariepinusandH. longifilis. The hybrids were shown to be completely intermediate between the parental strains.

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02556.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

Measurements of muscle dimensions that affect respiration in relation to body weight were carried out in a tilapia,Oreochromis niloticus. The fish used in all measurements weighed 0.65–812.3 g. The data were analysed with respect to body weight using logarithmic transformations (log Y=loga+blogW).The slopes (b) of the log/log regression lines for weight of body trunk red muscle, average cross‐sectional area of muscle fibre, average number of capillaries in direct contact with a muscle fibre, average capillary contact length with a fibre as a fraction of average fibre circumference and number of capillaries mm2of fibre cross‐sectional area [NA(cƒ)] were 1.16, 0.221, 0.084, 0.015, and −0.137 respectively.These results show that there is an increase in muscle cross‐sectional fibre area and number of capillaries in contact with muscle fibres whereas number of capillaries supplying a unit area of muscle fibre decreases during development. There is development of new capillaries with increase in cross‐sectional area of red m

ISSN:0022-1112    

DOI:10.1111/j.1095-8649.1992.tb02557.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY