The Cross Breeding Of Northern Largemouth Bass And Florida Largemouth Bass

The largemouth bass (Micropterus salmoides L.), common name Californian bass,was subordinate to Perciformes, Porcoidei, Cehtrachidae, Micropterus. The nativerange of the northern largemouth bass M. s. salmoides extended throughoutnortheastern Mexico, southeastern Canada, and the U.S. corridor in between,while theFlorida largemouth bass M. s. floridanus consisted of peninsular Florida. The northernlargemouth bass was introduced into Taiwan province of China in the late1970s andinto mainland in1983.Now it’s one of important cultivated fish in China.Cultivate moreexcellent cultured stocks is very necessary for aquaculture industry. Hybridization as animportant means of fish breeding,can effective transfer good traits of their parents andincrease genetic variation.A large number of lab tests show some hybrid can improvethe growth and stress resistance of the hybrid offspring. In this paper,growth difference,low lethal temperature tolerance,oxygen consumption rate，asphyxiation point，morphology and genetic structure were compared,aimed to provide basic data forcrossbreeding.1.The growth comparison experiments between parental and offspringThe experiment were between northern largemouth bass and two reciprocalhybrids.The growth rates had no difference between northern largemouth bass(N),northern largemouth bass♀×florida largemouth bass♂(N♀×F♂) and northernlargemouth bass♂×florida largemouth bass♀(F♀×N♂) on152days.After152days thenorthern largemouth bass growth more rapidly than two hybrids.2.Low lethal temperature tolerance,oxygen consumption rate and asphyxiation point offour largemouth bass speciesThe tolerance to low water temperature, oxygen consumption rate andasphyxiation point were compared among northern largemouth bass, florida largemouthbass and their reciprocal hybrids. The results were as follows: when the acclimationtemperature was20℃and the rate of temperature decrease was2h/℃,the low semi-lethal temperatures of northern largemouth bass was the lowest(3.1±0.17℃),florida largemouth bass was the highest(5.05.0±0.21℃).One-way ANOVA analysisindicated that there were significant differences(P<0.05) in the tolerance to lowtemperature of four largemouth bass species.The oxygen consumption rate andasphyxiation point of four largemouth bass species were studied.The resultdemonstrated that,under the natural water temperature(24~27℃), the oxygenconsumption rate were0.1368mg/g.h,0.1811mg/g.h,0.1681mg/g.h and0.1388mg/g.h,respectively. There were no significantly difference for the oxygen consumption rate atthe four groups in day and night. Under constant temperature15℃,the asphyxiationpoint of them were0.33mg/L,0.40mg/L,0.38mg/L and0.34mg/L, respectively.Therewas no significantly difference between the oxygen consumption of the four largemouthbass species(P>0.05).3. The morphological characteristics of four largemouth bass stocksAs meristic characters,the numbers of soft ray of pelvic,spine of anal fin,gill rakerand vertebra were consistent in these four populations,and the chi-square analysis ofmeristic characters showed high significant differences between parents and hybrids onsoft of dorsal,soft ray of pectoral,soft ray of anal fin,soft ray of tail fin,scales abovelateral line and scales below lateral line.The results of cluster analysis have revealedthat the morphometric characters of N and F were much closer,as well to the reciprocalhybrids groups.Three principal components with accumulative variance percentage71.44%were summarized in principal component analysis.The principal components1,2and3reflected the morphological variations of frame,head and caudalpeduncle,with the variance percentage being54.9%,11.2%and5.33%.In discriminantanalysis,11paramenters were selected from35measured paramenters to establishdiscriminant functiond of the populations.Discriminant accuracy was83.9%-100%.3. Genetic analysis of northern largemouth bass, Florida largemouth bass and theirreciprocal hybridsEighteen pairs of microsatellite primers were used to study genetic variation andgenetic structure of northern largemouth bass(N),florida largemouth bass(F) and theirobverse cross(N♀×F♂),inverse cross(F♀×N♂). The result suggested the number ofalleles generated from each locus was2to8,the mean allele number was5.0.Sixsubspecies specific loci(Jzl48,Jzl68,Jzl84,MiSaTPW76,Msal21,Mdo6and Mdo7)were screened out among these primers which could effectively identify those twosubspecies of largemouth.Moreover,2loci(Jzl48,Mdo7) could be used to distinguishparents and their reciprocal hybrids. The number of effect alleles(Ne),expected heterozygosity(HE) and polymorphic information content were all the highest inF♀×N♂as3.1997,0.6389,0.5706respectively.The observed heterozygosity(HO) wasthe highest in N♀×F♂as0.8488.FSTanalysis of all groups and loci indicated that theall of the two reciprocal hybrids got a lower genetic differentiation with N species. TheUPGMA clustering analysis showed that the offspring was near female brood stock inthe obverse cross and near to male brood stock in the inverse cross.