Reciprocal Hybrid Crosses Research Articles

INDEPENDENT INHERITANCE OF PREFERENCE AND PERFORMANCE IN HYBRIDS BETWEEN HOST RACES OF MITOURA BUTTERFLIES (LEPIDOPTERA: LYCAENIDAE)

Divergent natural selection contributes to reproductive isolation among populations adapting to different habitats or resources if hybrids between populations are intermediate in phenotype and suffer an associated, environmentally dependent reduction in fitness. This prediction was tested using two host races of Mitoura butterflies. Thirty-five F1 hybrid and parental lines were created, larvae were raised on the two host plants, and oviposition preferences were assayed in choice arenas. Larvae from both reciprocal hybrid crosses suffered a host-specific reduction in performance: when reared on incense cedar, hybrid survival was approximately 30% less than the survival of pure lines of the cedar-associated host race. The performance of hybrid larvae reared on the other host, MacNab cypress, was not reduced relative to parental genotypes. Females from both reciprocal hybrid crosses preferred to oviposit on incense cedar, the same host that resulted in the reduced survival of hybrid larvae. Thus, dominance is implicated in the inheritance of traits involved in both preference and performance, which do not appear to be genetically linked in Mitoura butterflies. Gene flow between host races may be reduced because the correlation between preference and performance that was previously described in parental populations is essentially broken by hybridization.

INDEPENDENT INHERITANCE OF PREFERENCE AND PERFORMANCE IN HYBRIDS BETWEEN HOST RACES OF MITOURA BUTTERFLIES (LEPIDOPTERA: LYCAENIDAE)

Divergent natural selection contributes to reproductive isolation among populations adapting to different habitats or resources if hybrids between populations are intermediate in phenotype and suffer an associated, environmentally dependent reduction in fitness. This prediction was tested using two host races of Mitoura butterflies. Thirty-five F1 hybrid and parental lines were created, larvae were raised on the two host plants, and oviposition preferences were assayed in choice arenas. Larvae from both reciprocal hybrid crosses suffered a host-specific reduction in performance: when reared on incense cedar, hybrid survival was approximately 30% less than the survival of pure lines of the cedar-associated host race. The performance of hybrid larvae reared on the other host, MacNab cypress, was not reduced relative to parental genotypes. Females from both reciprocal hybrid crosses preferred to oviposit on incense cedar, the same host that resulted in the reduced survival of hybrid larvae. Thus, dominance is implicated in the inheritance of traits involved in both preference and performance, which do not appear to be genetically linked in Mitoura butterflies. Gene flow between host races may be reduced because the correlation between preference and performance that was previously described in parental populations is essentially broken by hybridization.

Lower fitness of hatchery and hybrid rainbow trout compared to naturalized populations in Lake Superior tributaries.

We have documented an early life survival advantage by naturalized populations of anadromous rainbow trout Oncorhynchus mykiss over a more recently introduced hatchery population and outbreeding depression resulting from interbreeding between the two strains. We tested the hypothesis that offspring of naturalized and hatchery trout, and reciprocal hybrid crosses, survive equally from fry to age 1+ in isolated reaches of Lake Superior tributary streams in Minnesota. Over the first summer, offspring of naturalized females had significantly greater survival than offspring of hatchery females in three of four comparisons (two streams and 2 years of stocking). Having an entire naturalized genome, not just a naturalized mother, was important for survival over the first winter. Naturalized offspring outperformed all others in survival to age 1+ and hybrids had reduced, but intermediate, survival relative to the two pure crosses. Averaging over years and streams, survival relative to naturalized offspring was 0.59 for hybrids with naturalized females, 0.37 for the reciprocal hybrids, and 0.21 for hatchery offspring. Our results indicate that naturalized rainbow trout are better adapted to the conditions of Minnesota's tributaries to Lake Superior so that they outperform the hatchery-propagated strain in the same manner that many native populations of salmonids outperform hatchery or transplanted fish. Continued stocking of the hatchery fish may conflict with a management goal of sustaining the naturalized populations.

Equivalent Survival and Different Development Rates in Reciprocal Apache Trout × Rainbow Trout Hybrids

Abstract Hybrid individuals from naturally spawning populations of Apache Trout (Oncorhynchus gilae apache) and Rainbow Trout (Oncorhynchus mykiss) have been reported to hybridize successfully in only one direction. This is suggested by the absence of Rainbow Trout mitochondrial haplotypes in hybrid individuals. By artificially producing reciprocal crosses of Apache Trout and Rainbow Trout, the apparent unidirectional fertilization in naturally spawning hybrid populations was shown not to be the result of gametic incompatibility or early zygote death. Although survival rate differences between the reciprocal hybrid crosses were not significantly different, development rate differed significantly between the groups (P < 0.001). Using time to hatch as the indicator of development rate, Apache female by Rainbow male hybrids had a mean time to hatch seven days faster than Rainbow female by Apache male hybrids with both developing intermediate to the pure crosses. Although this could account for the perceived ...

Disruption of doubly uniparental inheritance of mitochondrial DNA in hybrid mussels (Mytilus edulis x M. galloprovincialis).

Blue mussels of the genus Mytilus have an unusual mode of mitochondrial DNA inheritance termed doubly uniparental inheritance (DUI). Females are homoplasmic for the F mitotype which is inherited maternally, whereas males are heteroplasmic for this and the paternally inherited M mitotype. In areas where species distributions overlap a varying degree of hybridization occurs; yet genetic differences between allopatric populations are maintained. Observations from natural populations and previous laboratory experiments suggest that DUI may be disrupted by hybridization, giving rise to heteroplasmic females and homoplasmic males. We carried out controlled laboratory crosses between Mytilus edulis and M. galloprovincialis to produce pure species and hybrid larvae of known parentage. DNA markers were used to follow the fate of the F and M mitotypes through larval development. Disruption of the mechanism which determines whether the M mitotype is retained or eliminated occurred in an estimated 38% of M. edulis x M. galloprovincialis hybrid larvae, a level double that previously observed in adult mussels from a natural M. edulis x M. galloprovincialis hybrid population. Furthermore, reciprocal hybrid crosses exhibited contrasting types of DUI disruption. The results indicate that disruption of DUI in hybrid mussels may be associated with increased mortality and hence could be a factor in the maintenance of genetic integrity for each species.

WOLBACHIA INTERACTIONS THAT DETERMINE DROSOPHILA MELANOGASTER SURVIVAL

We have recently described a mutualistic symbiosis in which Wolbachia bacteria were shown to improve the fitness of some Drosophila melanogaster stocks. Wolbachia did not extend longevity in all Drosophila genotypes, even though 16s rDNA sequences indicated that our Drosophila stocks were infected with the same Wolbachia strain. Here, we use reciprocal hybrid crosses between two Drosophila strains, one that lived longer with Wolbachia (Z53) and one that did not (Z2), to investigate the inheritance of the survival phenotype and its dependence on the host genotype, sex, and mating conditions. Wolbachia's positive effects were more apparent in hybrid flies than in parental flies, ruling out exclusive maternal inheritance or the dependence of the survival phenotype on Wolbachia strain differences. The Wolbachia survival effects were more apparent in single-sex cages, where courtship and mating were not permitted. In these cages, nearly all flies with Wolbachia lived longer than uninfected flies, even though strain Z2 showed no Wolbachia effect in mixed-sex mating cages. We used comparisons between single- and mixed-sex cages to estimate the cost of reproduction for both sexes. Our data suggest that Wolbachia infection may increase the inferred cost of reproduction, particularly in males. Wolbachia can even produce a positive survival effect almost as large as the negative survival effect associated with reproduction. We discuss the implications of our experiments for the study of insect symbioses.

Dietary Supplementation of Vitamin C and/or Vitamin E before or after Experimental Infection withStreptococcus iniaeHas Limited Effects on Survival of Hybrid Striped Bass

Abstract To examine the prophylactic and therapeutic value of dietary vitamins C and/or E given in megadoses against disease, juvenile reciprocal-cross hybrid striped bass (female white bass Morone chrysops × male striped bass M. saxatilis) were fed experimental diets with 2,500 mg vitamin C/kg diet (100× the established dietary requirement), 300 mg vitamin E/kg (10× the dietary requirement), or both at the requirement or megadose levels for 3 or 6 weeks before and 0, 3, or 7 d after experimental exposure to Streptococcus iniae. The first dead fish was observed 3 d following intraperitoneal injection with S. iniae, and mortality did not appear to be significantly affected by dietary vitamin level or length of feeding. Infection with S. iniae reduced tissue total ascorbate and α-tocopherol levels at 14 and 21 d postinjection relative to those in uninfected control fish. Dietary vitamin E at 300 mg/kg significantly increased mortality when fed for 3 weeks before exposure. Additionally, dietary vitamin C at ...

A Low Cost Bar Grader for the Harvest of Hybrid Striped Bass (Morone chrysops x M. saxatilis)

Four bar graders were designed and built to separate a mixed-size population of market-size reciprocal cross hybrid striped bass Marone chrysops x M. saxatilis in rectangular culture tanks in an indoor, recirculating aquaculture system. Grader frames were constructed of 5.1 cm (2 inch) PVC pipe and fittings. PVC electrical conduit ( 1.27 cm, 0.5 inch) was used to form a series of parallel, equally spaced vertical bars within the frame. Bar slot spaces were 1.90, 2.54, 3.20, or 3.80 cm (0.75, 1.0, 1.25, 1.5 inches). A strip of flexible vinyl siding was attached to the outer edges of the bar grader to permit a tight fit between the grader and tank walls, and prevent fish from swimming around the grader. The graders were placed sequentially into one end of the tank, largest slot size first, and maneuvered to the opposite end. Each grader International Journal of Recirculating Aquaculture, Volume 3 5 remained in the tank for 60 min. Fish too large to pass through a grader were netted and measured for weight, length and width. Regression analysis was performed for average weight retained at each bar spacing (Y = 7.13619 + 0.070716 X; r2 = .9987). By rearrangement, an equation was derived which allows a culturist to select a bar spacing that retains fish of a predetermined weight : Grader bar slot size (mm)= Fish weight (g) -177.9 I 31.7) Construction of each grader required approximately 2 h, and materials cost $20.

Evaluation of Different Stocking Densities for Hybrid Striped Bass in Small-Scale Recirculation Systems

Abstract The maximum density of fish that can be grown in an aquacultural system is an important factor determining the economic feasibility of individual operations. We conducted two separate studies with reciprocal-cross hybrid striped bass (striped bass Morone saxatilis × white bass M. chrysops) reared in a recirculating-water system. Densities initially established in the first experiment were 0.8, 1.4, 1.5, 1.9, 2.3, and 2.7 kg/m3. At the end of 70 d, weight gain, feed efficiency, survival, and dress-out were not significantly different among density groups. Standing crop increased significantly as stocking density increased; the highest density obtained was 28 kg/m3. In the second experiment, initial densities of 2.5, 5.0, 7.5, 10.0, 12.5, and 15.0 kg/m3 were established. After 86 d, mean weight gain, feed efficiency, and dress-out were not significantly different. Standing crop increased significantly with increasing density; the highest mean value was 55.5 kg/m3. Ash concentrations in the muscle o...

Dietary lipid level but not l-carnitine affects growth performance of hybrid striped bass ( Morone chrysops ♀× M. saxatilis ♂)

The objectives of this experiment were to determine if dietary lipid levels in excess of previously reported minima would increase performance of hybrid striped bass, and to determine if supplementation of l-carnitine would improve growth and/or body composition when feeding elevated dietary lipid. Therefore, a 2×4 factorial design was utilized to test the efficacy of dietary l-carnitine at 0 and 3000 mg/kg diet at each of four lipid levels (5%, 10%, 15% and 20%). Semipurified diets were formulated to contain 40% crude protein and dextrin was substituted for menhaden oil at a rate of 2.25 to 1 to maintain digestible energy at approximately 14.2 kJ/g. Juvenile reciprocal cross hybrid striped bass initially averaging 2.5 g/fish were cultured in a 5‰ brackish water recirculating system and fed twice daily at a rate approaching apparent satiation. At the end of the 8-week feeding trial, l-carnitine supplementation did not influence weight gain, but dietary lipid level did, with the lowest value (1084% of initial weight) achieved by fish fed 5% lipid and the highest (1343%) by fish fed 15% lipid; fish fed 20% lipid had intermediate weight gain (1215%). Feed efficiency also was influenced by dietary lipid with fish fed the 10% and 20% lipid diets having higher feed efficiency values than those fed the 5% and 15% lipid diets. Body condition indices were only slightly altered by l-carnitine supplementation, but dietary lipid over 10% influenced body condition. Liver composition was altered by dietary lipid level but not l-carnitine supplementation. As dietary lipid level increased, liver lipid increased and liver glycogen decreased dramatically, especially in fish fed the diet with 20% lipid, which had no soluble carbohydrates. Muscle composition was unaltered by any dietary treatment. In conclusion, hybrid striped bass generally did not utilize dextrin as efficiently as lipid, and lipid levels between 10% and 15% of diet provided maximum growth with intermediate lipid deposition.

Acute Toxicity of Ammonia and Nitrite to Reciprocal Cross Hybrid Striped Bass Morone chrysops×M. saxatilis Eggs and Larvae

Acute Toxicity of Ammonia and Nitrite to Reciprocal Cross Hybrid Striped Bass <i>Morone chrysops</i>×<i>M. saxatilis</i> Eggs and Larvae

Experimental evidence for reduced hybrid viability between dwarf and normal ecotypes of lake whitefish (Coregonus clupeaformis Mitchill)

Forces driving the evolution of reproductive isolation among natural populations, as well as the mechanisms involved to maintain it, are still poorly understood. Because sympatric fish ecotypes mainly differ in phenotypic traits associated with occupying distinct trophic niches, it is generally believed that reproductive isolation is mainly driven by ecological divergent selection, excluding genome incompatibility as a basis for postmating isolation. We did cross experiments between dwarf and normal ecotypes of lake whitefish (Coregonus clupeaformis Mitchill) originating from distinct glacial refugia to test the hypothesis that their geographical isolation during the Pleistocene may have led to sufficient genetic divergence for the development of reproductive isolation between them before their secondary contact. Similar fertilization success in pure and hybrid crosses indicated the absence of gametic incompatibility between the two ecotypes. In contrast, daily embryonic mortality rates were 2.4–4.7 times higher in reciprocal hybrid crosses compared to pure crosses, which supports our working hypothesis. These results, along with previous morphological and population genetic studies, indicate that both genetic and ecological mechanisms may jointly act to promote speciation among northern freshwater fish ecotypes.

Putative Location of Common Region and Coat Protein Gene of Blackgram Isolate of Mungbean Yellow Mosaic Geminivirus

Reciprocal cross hybridization between DNA-A and ONA-B molecules showed that MYMV genome contains certain regions common to each other. “Common region” of MYMV belongs to the 0.55 kb Kpnl-Clal fragment of DNA-A and 0.25 kb Xbal-Hind III fragment of DNA-B. Hybridization of DNA-A restriction fragments with the full length coat protein region probe to Indian cassava mosaic virus (ICMV) showed the location of MYMV coat protein coding region in DNA-A. The greater extent of homology of ICMV coat protein region falls within the 400 base pair region of Clal-Clal fragment in DNA-A of MYMV-Bg. The homology between ICMV and MYMV-Bg coat protein gene appeared to be less than 50%. Cross hybridization between DNA-A and DNA-B molecules helped to trim out the homologous region and the DNA-A and DNA-B specific probes could be tailored.

Dietary threonine requirement of juvenile hybrid striped bass (Morone chrysops ♀×M. saxatilis ♂)

Two growth studies were conducted to determine the dietary threonine requirement of reciprocal cross hybrid striped (sunshine) bass. Semipurified diets were prepared with crystalline amino acids and lyophilized fish muscle to supply 350 g crude protein kg−1 diet. The basal diet contained 4.9 g threonine kg−1 from fish muscle, and test diets were supplemented with graded levels of L-threonine. In the first experiment, fish initially averaging ≊ 9.8 g each were fed diets containing threonine levels of 4.9, 7.5, 10.0, 12.5, 15.0 and 17.5 g kg−1 dry diet for 7 weeks. Weight gain, feed efficiency and protein efficiency ratio (PER) were significantly (P < 0.01) influenced by dietary threonine level. Based on weight-gain responses, a threonine requirement (± SE) of 8.4 (± 0.8) g kg−1 dry diet was determined, and dietary threonine levels of 10.0 g kg−1 diet or greater resulted in the highest levels of free threonine in plasma. Based on the results of the first experiment, a second feeding trial was conducted with diets containing threonine levels of 4.9, 6.5, 8.0, 9.5, 11.0 and 12.5 g kg−1 dry diet. Fish initially averaging ≊ 3.0 g each were fed each diet for 8 weeks. Weight gain, feed efficiency and PER values of fish were markedly improved, with increases in dietary threonine up to 8.0 g kg−1 dry diet. Regression analysis of weight gain, feed efficiency and PER data using the broken-line model resulted in threonine requirement estimates of 9.7, 8.5 and 8.6 g kg−1 dry diet, respectively. Based on these data, the threonine requirement of juvenile sunshine bass was determined to be ≊ 9.0 g kg−1 dry diet or 26 g kg−1 of dietary protein.

Geographic variation in development rate between populations of the teleost Fundulus heteroclitus

The teleost Fundulus heteroclitus (Linnaeus) employs a semilunar spawning strategy, whereby eggs deposited on a spring tide optimally hatch on the following spring tide. This spawning strategy constrains the development period to ≃2 wk, regardless of the mean water temperature, which varies throughout the species' range (Nova Scotia, Canada, to Florida, USA). We hypothesized that F. heteroclitus embryos would exhibit development-rate compensation among populations to ensure appropriate hatching during the spring tide. Development rates of embryos from Massachusetts and Florida were examined. Northern embryos had faster temperature-specific development rates than southern embryos, while data from the literature showed that embryos from Delaware have an intermediate development rate. Results from reciprocal hybrid crosses indicated that there may be a genetic basis for these differences. In addition, northern embryos were more cold-tolerant and southern embryos more heat-tolerant. Field studies showed that embryos in their local environments develop at similar rates despite large temperature differences. Embryos seldom, if ever, experience lethal temperatures in their native habitats, but would do so if exposed to the temperature regimes at the extreme ends of the species' range. Thus, F. heteroclitus populations along the Atlantic coast have specifically adapted their development rates and thermal tolerances to the local thermal regime.

Cross-screening: a new method to assemble clones rapidly and unambiguously into contigs.

We have developed a new procedure that relies on an array of cross-hybridization tests to order a set of random clones into a contig. The method, called cross-screening, uses each clone as a target and its end sequences as probes, in a matrix of reciprocal cross-hybridization tests performed on a single blot. The relationships among the clones are determined rapidly from the pairwise tests, allowing clone order to be determined directly. We have applied this technique to DNAs from a set of overlapping lambda clones from Drosophila chromosome 4. The location and orientation of each clone derived from the cross-screening data was that expected from the map assembled from overlapping restriction sites and chromosomal walking. The procedure provided additional information on a previously unknown, internally repeated DNA sequence. To demonstrate the general utility of the procedure, we have applied it to a previously described clone set within a contig in region 22q12 of human chromosome 22. The correct relative position and orientation of these clones were derived from the cross-screening data without knowledge of, or reference to, any nucleotide sequence or restriction site analysis of the DNA concerned. The cross-screening procedure is fast, economical, and robust and allows clone overlaps to be determined efficiently, with minimal interference from repeated DNA sequences. This new procedure is specifically designed for small groups of overlapping clones (tens to hundreds) and should facilitate the ordering of subclone libraries derived from small chromosomes or the large cloned inserts carried in YAC, BAC, and P1 vectors.

Relationship of blood loss to worm numbers, biomass and egg production in Haemonchus infected sheep

Chromium51 labelled erythrocytes were used to measure blood loss in sheep infected with either H. contortus, H. placei or the F1 of their reciprocal cross hybrids (H. contortus males × H. placei females = CXP, H. placei males × H. contortus females = PXC). CXP consisted of sterile males and semi-sterile females and sheep infected with this hybrid had nil egg counts; while PXC consisted of semi-sterile males and females and their hosts had some eggs in their faeces. Immediately after their blood loss was estimated the sheep were killed and their worms counted. One hundred male and 100 female worms from each sheep were dried at 60°C overnight and then weighed to give an estimate of the biomass in each infection. Total daily egg production was calculated from egg counts made on 3 random 2 g samples from the 24 h faecal collection. The relationship of the log blood loss to log worm number, to log biomass of infection in each sheep and to log total egg production in the parental species was linear. Biomass was no better an estimator of blood loss than was worm number. There was no improvement in the estimation of blood loss by regressing the male and female worms separately. In all of the analyses, there was no improvement by regressing H. contortus and H. placei or their hybrids separately. It appeared that egg production was not a major factor in the requirement for blood by Haemonchus. The size of individual female worms was negatively correlated with the number of worms in the infection. The linear nature of the relationship of blood loss to worms number, worm biomass and worm egg production indicated that sheep have very little control of blood loss and that the limitation of the pathology of Haemonchus infections is likely to be exerted at the establishment stage of the infection.

Comparative growth of reciprocal carp hybrids between Catla catla and Labeo fimbriatus

Intergeneric hybrids between catla ( Catla catla) and fimbriatus ( Labeo fimbriatus) were produced by employing the technique of hypophysation and dry stripping. Detailed investigations on their embryonic and larval development, taxonomic characters and aquaculture potential in terms of growth, feed utilization, body carcass composition, meat yield etc. were carried out. The growth experiment was conducted in concrete tanks (5 × 4 × 1.2 m) in triplicate following normal rearing practice for a period of 154 days. Growth was assessed at 14-day intervals. At the time of fish sampling, water and plankton were also analyzed. It was revealed that the growth of the hybrids was intermediate to the parental species. The final individual weights attained by catla, fimbriatus, catla X fimbriatus (male parent named first) and fimbriatus X catla were 64.2, 24.1, 39.8 and 57.8 g, respectively. Among the hybrids, the growth of fimbriatus X catla was faster than the slow-growing parent fimbriatus and the reciprocal cross hybrid and slightly less than fast-growing catla. The increase in weight attained by fimbriatus X catla was 153.4 and 45.0% more than fimbriatus and the reciprocal hybrid, respectively, but not different from catla. During the course of the investigation it was also observed that the hybrids combined desirable qualities such as the small head of the fimbriatus and the deep body of the catla and exhibited heterosis in terms of meat yield with higher flesh content than either of the parents. Hence the hybrids appear to be of considerable importance to aquaculture.

Composition and Quality of Aquacultured Hybrid Striped Bass Fillets as Affected by Dietary Fatty Acids

ABSTRACTFive groups of reciprocal cross hybrid striped bass were fed semipurified isocaloric diets containing varying concentrations of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Fatty acid compositions of the edible muscle tissue generally reflected the fatty acid contents of the diets with greater concentrations of DHA being accumulated compared to EPA. Descriptive sensory evaluation of cooked fish fed diets containing at least 0.50% EPA and 0.24% DHA showed a significant increase in fishy flavor intensity compared to cooked fish fed diets containing trace amounts of these n‐3 fatty acids. Hybrid striped bass can be a good source of nutritional n‐3 fatty acids when sufficient quantities are incorporated into their diet.

Effects of trichlorfon, fenthion, and diflubenzuron on the zooplankton community and on production of reciprocal-cross hybrid striped bass fry in culture ponds

The application of trichlorfon, diflubenzuron, or fenthion to fertilized culture ponds stocked with 5-day-old, reciprocal-cross, hybrid striped bass fry resulted in an initial reduction in the concentration of rotifers and longer-term alteration of zooplankton successional stages, including changes in concentrations of rotifers, cladocerans, and copepods. Culture ponds without applied chemicals had the highest concentrations of small rotifers when fry were stocked, followed by high concentrations of cladocerans, copepod nauplii, and adult copepods. Fry survival in untreated ponds was higher than in chemically-treated ponds. Initial high concentrations of copepods in some ponds corresponded with low fry survival. Untreated ponds that were filled at the time of broodfish spawning, and stocked with fry 5 days later, had the highest fry survival rates, corresponding with peak rotifer concentrations, followed by a typical zooplankton succession.