Diploid Siblings Research Articles

Growth of triploid oyster, Crassostrea madrasensis (Preston)

The performance of I and II meiotic triploids and control oysters (Crassostrea madrasensis) reared at Tuticorin Bay was compared to determine if the improvements in the growth of edible oysters were additive to faster growth in triploids. After a grow-out period of 12 months, both mean whole weights and shell heights were in order I meiotic triploid>II meiotic triploid>control. Mean whole weights and shell height of different oyster lines were all significantly different (P<0.05). On an average, larger morphological traits indicated that growth improvements from triploids were additive, and throughout the study triploid oysters maintained faster growth rate than their diploid siblings. Condition index and adductor muscle diameter of both triploids were higher than those of control.

In vitro steroid production by triploid ovarian follicles

Triploid female fish are unlike normal diploids in that they show impaired oocyte growth and are unable to produce viable offspring. Compared to diploid siblings, triploid female brook trout ( Salvelinus fontinalis) have significantly lower levels of plasma vitellogenin, testosterone (T), and estradiol-17β (E 2), and show significantly lower gonadosomatic indices. The purpose of this study was to compare in vitro steroid production by diploid and triploid ovarian follicles in order to determine whether delayed oocyte growth in triploids is the result of a decreased capacity for E 2 synthesis by triploid follicles. Intact oocytes (i.e., including follicular tissue) from several age 3 + triploids were pooled and sorted according to small (<2 mm), medium (2.2–3.0 mm), and large (4.0–5.0 mm) diameter size, and compared to same-sized vitellogenic oocytes from 3 + diploids. Oocytes were incubated for 8 h at 15 °C in the presence or absence of gonadotropin stimulus (SG-G100) and the precursors E 2, T, and cholesterol. Estradiol-17β output following SG-G100 treatment was significantly higher than in controls for both diploid and triploid follicles. Production of E 2 was dependent on stage of oocyte and follicular development in triploids, with triploid and diploid follicles of similar diameter producing similar amounts of E 2 with SG-G100 stimulus. This suggests that ovarian steroidogenesis is similar in diploids and triploids.

Influences of triploidy, parentage and genetic diversity on growth of the Pacific oyster Crassostrea gigas reared in contrasting natural environments.

An increasing number of hypotheses are being proposed to explain the faster growth potential of triploids in molluscs, including their partial sterility or their higher heterozygosity compared to diploids. Triploid advantage however, remains controversial for poorer sites, because of a potential trade-off with survival. These questions were addressed in Crassostrea gigas by deploying meiosis II triploids and their diploid siblings from a single mass spawning of three males and seven females, in two contrasting locations for their trophic resources. One hundred and fifty individuals were sampled at each site after nine months, measured for weight and biochemical composition, and genotyped using three microsatellite and seven allozyme loci. Higher performance was observed at the fast-growing site for all traits except shell weight, and triploids had greater weights and biochemical contents than diploids at harvest. Triploids also grew faster at the poorer site, and showed similar survival rates to diploids at both sites. Triploids had significantly higher average allozyme and microsatellite diversity. However, they performed better for a wide range of individual heterozygosity values, arguing for an advantage of the triploid state per se, that could be due to positive effects on growth of both sterility of triploids with subsequent resource re-allocation and possible faster transcription with three copies of each gene. Despite evidence of very low or no inbreeding in the diploid sample, positive associations between individual allozyme diversity and growth were detected, which explained little but significant amounts of phenotypic variation. These associations were interpreted as direct effects of allozymes, either alone or including epistatic interactions with other loci. In addition, measures of individual distance (mean-d2) specific to microsatellites, were negatively correlated with growth in diploids, indicating possible effects of outbreeding depression between more distant genomes of parents from distinct populations.

Monosomic addition lines of Beta corolliflora in sugar beet: plant morphology and leaf spot resistance

AbstractMonosomic addition lines in Beta vulgaris from Beta corolliflora were described morphologically and characterized for disease resistance. Monosomic addition plants (2n= 19) were selected among segregating offspring by a squash dot technique in combination with B. corolliflora‐specific probes. Plants carrying an added chromosome were characterized by leaf shape, plant size and plant vigour. In this way, most addition lines could be distinguished from diploid beets, however, to identify those plants unequivocally, molecular marker analysis was also necessary. Transmission frequencies of each addition line were determined to be in the range 13.9% (Cor‐4) to 60% (Cor‐9). High transmission rate of addition line Cor‐9 was assumed to be due to apomictic propagation because transmission rate after selfing cannot exceed 50%. Cercospora leaf spot resistance tests were performed on 167 monosomic plants from seven different addition lines, two fragment addition lines and 89 diploid controls. No line exhibited complete resistance, but the monosomic additions Cor‐3 and Cor‐4 showed significantly lower infection rates than their diploid sibling plants. The identification of monosomic addition lines with apomictic and disease resistance characters offers the possibility of transferring those genes to sugar beet.

Comparative feeding and physiological energetics in diploid and triploid Sydney rock oysters ( Saccostrea commercialis) : II. Influences of food concentration and tissue energy distribution

This study determined the potential roles of food concentration and distribution of energy between body components in the greater growth rates of triploid Sydney rock oysters ( Saccostrea commercialis) compared to diploids. Laboratory studies were conducted using rehydrated microalgae, Spongiococcum excentricum, up to 20 mg l −1, to assess food concentration effects on the feeding and physiological energetics of juvenile and adult diploid and triploid S. commercialis. The parameters clearance rate (CR), absorption efficiency (abs. eff.), pseudofaeces production (PF), respiration ( R) and ammonia excretion ( E) were measured to determine the energy available for growth and reproduction, defined as scope for growth (SFG). The cost of respiration and excretion was significantly higher for adult diploid oysters across a range of food concentrations (3 to 20 mg l −1). Juvenile diploids also used more energy in excretion across this range of food concentration. These differences in energy expenditures contribute to marginal differences in scope for growth (SFG). Triploid S. commercialis have higher SFG than their diploid siblings at low food; however, they have less ability to handle higher food concentrations than diploid oysters. Because of this inability of triploids to outperform their diploids at high food concentrations, feeding and physiological energetics probably play only minor roles in the observed differences in growth of diploid and triploid S. commercialis. Analyses of the energy content of soft and shell tissues in adult oysters revealed major differences between the ploidy conditions. Triploid oysters have total energy content that is much higher than diploids of the same shell length, and their soft tissue content is relatively higher. In adult triploids, either or both of two things are occurring to enhance their growth advantages over diploids: (1) the proportion of energy devoted to soft tissue production (flesh and reproductive tissue) is greater or (2) the stunted reproductive cycle of triploids helps them maintain energy levels stored in the soft tissue, whereas diploids expend and must replenish these levels following a reproductive episode.

The kinetics of the hypoferraemic response and changes in levels of alternative complement activity in diploid and triploid Atlantic salmon, following injection of lipopolysaccharide

To study any possible effects of triploidy on the kinetics of the response of two non-specific disease factors, full sibling diploid and triploid Atlantic salmon were injected intraperitoneally with either lipopolysaccharide (1mg kg−1body weight) or saline. Individually marked fish were repetitively blood sampled for up to 19 days. Total serum protein concentrations remained constant throughout the experiment indicating that the sampling regime did not cause haemodilution. The alternative complement pathway activity (measured by the titre of haemolytic activity against rabbit erythrocytes) in the serum of saline injected fish remained constant but in LPS-injected fish it fell to barely detectable levels 2 days after injection, but recovered to pre-treatment levels by about day 5. Triploid fish took slightly longer to reach full recovery levels than diploids. All groups of fish showed a hypoferraemic response, suggesting that the sampling regime was at least partially responsible. However, the response was more rapid and pronounced in the LPS-injected fish. In the latter, serum iron concentrations decreased to very low levels by day 2 post-injection in the diploid fish and by day 3 in the triploid fish. Pre-treatment iron levels were re-established by about 15 days post-injection in all groups. The data show only slight differences between the diploid and triploid fish, but the longer time taken for the triploids to recover complement activity and the slower onset of the hypoferraemic response following injection of LPS, suggest that they may be at a disadvantage compared with their diploid siblings in their defence against bacterial infections.

Ocean migration and recaptures of tagged, triploid, mixed-sex and all-female Atlantic salmon (Salmo salar L.) released from rivers in Ireland.

Fiftyfour thousand diploid and triploid Atlantic salmon were tagged with coded-wire micro-tags and released to the sea as smolts from two freshwater sites in Ireland in 1996 and 1997. Over 36,000 were mixed-sex groups in which the triploids (MS3N) were treated batches and the diploids (MS2N) were untreated batches of a single group of fertilized eggs at each site and year class. Over 17,000 were all-females, the triploids (AF3N) being treated batches and the diploids (AF2N) untreated batches of a single group of fertilized eggs at each site and year class. Adult tagged fish were subsequently recovered in the coastal fishery and in freshwater traps and angling fisheries in the rivers of release during 1997, 1998 and 1999. Recoveries from migration ranged from 0.08 to 9.79%. Diploid recoveries were within the normal ranges for salmon ranched from these sites, being between 0.64 and 1.82% at one site and between 3.85 and 9.79% at the other. Triploid recoveries, which occurred in the coastal fishery and in freshwater, ranged from 0.08 to 0.40% at the first site and from 0.98 to 2.05% at the other. Overall, triploid recoveries were between 12 and 24% of their diploid siblings within each release group. There were two peaks of recapture in the coastal fishery, the first in mid-June and the second in mid to late July. All-female diploids appeared to enter the fishery in advance of mixed-sex diploids. Triploids were the latest to arrive. There was no evidence of increased straying in triploids relative to diploids and the mean lengths, weights and condition factors were not significantly different between the ploidy groups. Triploidisation therefore reduced the home water harvest of treated salmon to less than 25% but did not completely eliminate triploid recaptures. The way in which triploidisation may influence the return of salmon from the oceanic feeding grounds is discussed.

The First Findings on the Differences in Complete Blood Count Between Diploid and Triploid Tench, Tinca tinca L.

Svobodova. Z .. 1. Kolarova, M. Flajshans: The First Findings of the Differences in Complete Blood COltllt Between Diploid and Triploid Tench. Tinea tinca L. Acta vet. Bmo 1998, 67: 243-248. The aim of this work was to evaluate differences in complete blood count of diploid and triploid tench and concentration of total protein in blood plasma of these fish. Haematological examination of 78 specimens of three-year-old tench. consisting of 21 triploids and their 57 diploid siblings was performed in July 1996. Analysis of variance test confirmed a significantly lower erythrocyte count in triploids (P < 0.01). as well as a significantly lower haemoglobin content (P < 0.05), significantly higher medium corpuscular volume. higher medium corpuscular haemoglobin and lower medium corpuscular haemoglobin concentration (all at P < 0.01) compared to diploids. The haematocrit value of triploids was insignificantly lower compared to diploids. The differences of erythrocyte nuclear area. perimeter. average size, major axis and aspect ratio between diploids and triploids were found signiticant at P < 0.01 and the effect of ploidy level on these dimensions was considered highly significant (P < 0.000 I). No effect of ploidy level was proven for erythrocyte nuclear minor axis. The leukocyte count of triploids was insignificantly lesser compared to diploids. Triploid tench were found of significantly lower concentration of total protein in blood plasma compared to diploids (P < 0.01). Triploid tench could be hypothesized to have a lower oxygenation capacity of blood. as well as a lower non-specific immunity level compared to diploids. Insigniticantly higher erythrocyte count, haemoglobin content. haematocrit value. and significantly higher concentration of total protein in blood plasma (P < 0.0 I) was reported for diploid females compared to males.

Identification of triploid Citrus by isozyme analysis

Seedlessness is a desirable horticultural attribute in Citrus and is positively associated with triploidy. The conventional cytological method for triploid identification is a laborious technique involving the preparation of root tips for chromosomal analysis. Digital densitometry of isozymes, however, offers the possibility of distinguishing triploid Citrus from large populations of seedlings both quickly and cheaply. Where there are no gene dosage regulation effects, greater band density should be evident in the allozyme contributed by the diploid gamete for a heterozygous locus. The isozymes of 4 enzymes; malate dehydrogenase, 6-phosphogluconate dehydrogenase, shikimate dehydrogenase, and phosphoglucose isomerase, were investigated with polyacrylamide gel electrophoresis. Band densities of these isozymes for triploid Citrus, their diploid siblings and diploid progenitors were measured using a digital densitometer. Of the 4 enzymes investigated only allozymes for shikimate dehydrogenase exhibited consistent differences over a wide range of Citrus cultivars. Greater band density was evident in the allozyme contributed by the diploid gamete. The band density ratio between allozymes for triploid Citrus was close to 0.5, while for diploid Citrus band density ratios were close to 1.0. This effect is due to the extra protein coded by the additional gene dose and was not observed in diploids. Shikimate dehydrogenase proved to be an accurate molecular marker for distinguishing between diploid and triploid Citrus for heterozygous progeny.

Spontaneous structural rearrangements in Solanum phureja Juz. et Buk. 2. Meiotic behaviour and identification of interchange chromosomes using primary trisomics

Meiosis was studied in two diploid (2n = 2x = 24) siblings of Solanum phureja Juz. et Buk. and in 11 disomic and 2 trisomic descendants. The diploid siblings carry the same heterozygous interchange and either one or two inversions. The frequency of quadrivalents at diakinesis/metaphase I in these clones was 0.56 and 0.62 per pollen mother cell. In two plants from the first inbred generation (I1) this frequency was about the same but in some other I1 plants and a full sib the frequency was substantially lower, varying from 0.00 to 0.16. Most quadrivalents, 78-83%, were rings. A variety of quadrivalent configurations at diakinesis and metaphase I was observed, giving rise to balanced and unbalanced gametes. The absence of ring quadrivalents in trisomic descendants of one of the siblings implied that tertiary trisomics or primaries being homozygous for the interchange were present in the I1 generation. Regular chromosome distribution (12-12) at anaphase I occurred in 46.5 and 73.2% of the pollen mother cells studied in the two original clones. Irregularities, such as 11-13 distribution, lagging chromosomes, and a bridge and fragment, were detected on average in 2.7, 3.3, and 32.5%, respectively, of the anaphase I cells analysed. In hybrids from crosses between 6 primary trisomics as females with the interchange heterozygote, the involvement in the interchange of chromosomes 3 and 12 was clearly demonstrated.

A genetic and metabolic basis for faster growth among triploids induced by blocking meiosis I but not meiosis II in the larviparous European flat oyster, Ostrea edulis L.

This study establishes a genetic and metabolic basis to faster triploid growth in the oyster Ostrea edulis. Triploidy was induced using cytochalasin B, and image analysis of biopsied tissue employed to ensure similar ploidy of all animals within each class. Results indicate that lifetime growth in total dry tissue weight over 15 months was more than 60% faster ( p<0.001) in meiosis I triploids than in diploid siblings or meiosis II triploids, with no difference between meiosis II triploids and their diploid siblings. For six polymorphic enzyme loci, single-locus heterozygosity was consistently greatest in meiosis I triploids ( p<0.001), so that average multiple-locus heterozygosity in meiosis I triploids was 49% higher than in normal diploids, and 55% higher than in meiosis II triploids ( p<0.001). This suggests that faster growth resulted from increased allelic diversity, rather than the increased allelic quantity that results from the addition of one entire set of chromosomes among triploids generally. Results also confirm that the faster growth of meiosis I triploids resulted from reduced energy expenditure, associated with lower concentrations of RNA per unit total tissue protein, which infer reduced rates of whole-body protein turnover. Statistical analyses confirmed that differences in oxygen consumption and growth were associated with both ploidy class and average multiple-locus heterozygosity, indicating that performance in meiosis I triploids is not only improved as a result of reduced reproductive output, but also through the metabolic consequences associated with increased heterozygosity.

Studies on triploid oysters in Australia. I. The farming potential of triploid Sydney rock oysters Saccostrea commercialis (Iredale and Roughley)

A two-and-a-half-year study was conducted to compare the performance of sibling diploid and triploid Sydney rock oysters Saccostrea commercialis (Iredale and Roughley) at three intertidal and one subtidal site in Port Stephens, New South Wales (N.S.W.). The triploid Sydney rock oysters were on average 41% heavier than their diploid siblings after 2.5 years of growth. The triploid oysters also maintained higher dry meat weight and higher condition index (CI) values than their diploid siblings at all sites during the final 10 months' growth to market size (40 to 60 whole weight). The triploid oysters at the subtidal site had the highest CI values recorded in this study. When exposed to the protistan parasite Mikrocytos roughleyi which causes winter mortality disease, no differences in mortality between diploid and triploid groups occurred. These findings have major implications for the N.S.W. oyster industry as triploid Sydney rock oysters can reach market size 6–18 months faster and maintain better meat condition than diploid oysters without an increased risk of winter mortality.

Genetic studies of tench ( Tinca tinca L.): induced triploidy and tetraploidy and first performance data

Triploidy was successfully induced with cold shocks of 0–2°C, lasting 35 min and starting 2–5 min after gamete activation and with hydrostatic pressure shocks with 1, 2 and 5 min exposure at 50.01–52.47 MPa starting 2–5 min after gamete activation. Tetraploidy was successfully induced with heat shocks of 40.5°C, lasting 1.5 min and starting 45 min after gamete activation and with hydrostatic pressure shocks starting 50 min after gamete activation without further changes in the remaining parameters. Temperature shocks were considered to be the most suitable treatments, based on observed proportions of viable polyploids and incubation rates. The τ 0 unit for tench was used for standardization of shock initiation. Results of rearing triploid and/or tetraploid tench in experimental earthen ponds were assessed. A sample of 19 4-year-old triploid and their 43 diploid siblings was used for analysis of weight differences, gonadosomatic index and dressing percentage. Triploid females displayed 13.52% higher live weight and 3.94% higher dressing percentage than diploid females ( P<0.001) and their gonadosomatic index reached 25.10% of that of diploid females ( P<0.001). Triploid males displayed 23.66% higher live weight than diploid males ( P<0.01). Their dressing percentage was 1.30% lower ( P<0.1) while gonadosomatic index reached 60.00% of that of diploid males. Differences in live weight and gonadosomatic index between triploid females and triploid males were found statistically significant ( P<0.01 and P<0.05, respectively) while no difference was found in dressing percentage.

Growth of the induced triploid pearl oyster, Pinctada martensii (D.)

Treatment with cytochalasin B has been used to induce triploidy. During 2 years of culture in the sea, periodic measurements in Group I (treated by blocking meiosis I) and in Group II (treated by blocking meiosis II) have shown: (1) In juveniles the measurements of size and weight in triploids in Group I were significantly higher than those of diploid siblings ( P<0.001) but the difference in Group II was not significant. (2) In adults the measurements of size and weight of triploids in both groups were significantly higher than those of diploid siblings ( P<0.001). (3) During reproductive seasons, the daily growth rates of shell height and body weight of triploids were higher than those of diploid siblings in both groups, but in most months of nonreproductive seasons there were no differences. Gonad development in triploids was abnormal. During reproductive seasons, the gonads of most triploids remained at the inactive or proliferation stages, and only a few of them reached the growth stage. Comparative study on heterozygosities of three gene loci between triploids and diploids showed no positive relationship between the number of heterozygous loci and the size measurements in either group. Results suggest that the faster growth rate of triploid adults is caused by the retarded development of gonads in triploids.

Induced triploidy in the soft-shelled clam Mya arenaria: energetic implications

Given that triploid adult bivalves reportedly grow larger and faster than their diploid siblings, such differences should be traceable to variation in energy allocation. In one proposed mechanism, retarded gametogenesis found in triploid adults may allow them more energy for somatic growth. Another hypothesis states that triploids are more heterozygous; increased heterozygosity has been positively correlated with enhanced growth. Juvenile soft-shelled clams, Mya arenaria, were treated with cytochalasin B to induce triploidy and examined with respect to components of a balanced energy equation (C=P+R+E). The variables measured were oxygen uptake (Vo2), filtration rate (FR), dry tissue weight, shell length, shell height and shell inflation. Energy budgets were constructed and diploid and triploid groups compared. Few significant differences were found between diploid and triploid juvenile clams with respect to energy budget components. However, at seven loci assayed electrophoretically the triploid individuals were nearly twice as heterozygous as their diploid siblings. Moreover, tripoloid variances were less than diploid variances for every variable measured. Increased heterozygosity has been correlated with the decreased variance of morphological parameters. This study is believed to be the first to show decreased variance of physiological properties as well as morphological characters. Overall the data clearly indicate that energy allocation in juvenile M. arenaria is not related to ploidy.

The distribution of marked dermal cells from small localized implants in limb regenerates

Numerous experiments have demonstrated that skin has a profound influence on the pattern of limb regeneration in urodeles. In this investigation, the fate during regeneration of marked cells derived from narrow strips of skin inserted into different positions around the limb circumference has been followed. Skin strips were taken from triploid axolotls and transplanted into diploid sibling animals. The distribution of trinucleolate cells was determined at the site of amputation and in the regenerated limb. The results indicate that at the time of amputation marked cells appear to be localized to the graft, whereas in the regenerate marked cells may be found at all proximal-distal levels and at any position around the circumference of the limb. These results are discussed in terms of a possible mechanism for distal outgrowth.

Growth of American oysters increased by polyploidy induced by blocking meiosis I but not meiosis II

Triploidy in American oysters ( Crassostrea virginica) was induced by blocking polar body formation with cytochalasin B. Triploid oysters created by treatment during meiosis I grew faster during the first 3 years of life than did diploid siblings. Triploid oysters created during meiosis II grew at the same rate as their controls. Because heterozygosity was higher in oysters created during meiosis I than in other groups, the increased growth must be due to heterozygosity rather than to triploidy per se.

Adhesion and the Toe-Pads of Treefrogs

Various hypotheses concerning the functional mechanism of the toe-pads of treefrogs are discussed. A test of the relative adhesive abilities of the tetraploid treefrog Hyla versicolor and its diploid sibling species Hyla chrysoscelis shows little difference in ability to adhere to glass despite known large differences in the sizes of the pad cells. The adhesion of the toe-pads is thus related to the area of contact and not to the size or number of pad cells. Freshly killed treefrogs are as sticky as live treefrogs. The reduction of surface tension by soap solutions or detergent reversibly diminishes adhesive ability. Surface tension is the primary means by which treefrog toe-pads adhere to glass.

Size Differences in Adhesive Toe-Pad Cells of Treefrogs of the Diploid-Polyploid Hyla versicolor Complex

The tetraploid treefrog, Hyla versicolor, possesses larger cells on the adhesive digital pads than does its diploid sibling species, H. chrysoscelis. Examination of these cells with scanning electron microscopy shows apical surface areas to differ by a factor of 1.46 between the two species, which may be translated to a relative volumetric ratio of 1.77. This is comparable to the 1.8 ratios previously reported in comparisons of blood and sperm cells, mating call pulse rates and DNA content per cell of the two species. A strong correlation between cell size and ploidy is found in these frogs, the two species being discerned by this criterion 79% of the time.

IDENTIFICATION OF A FACTOR IN MAIZE THAT INCREASES EMBRYO FATTY ACID UNSATURATION BY TRISOMIC AND B-A TRANSLOCATIONAL ANALYSES

Trisomics and B-A translocations were utilized in Zea mays L. (maize) to detect a genetic factor(s) in the long arm of chromosome 5 expressing dosage effects which increases the fatty acid unsaturation level in embryos. In all lines analyzed, trisomic-5 embryos had significantly less oleic acid and significantly more linoleic acid than diploid sibling embryos. Oleic and linoleic acid levels were unaltered by trisomy of chromosomes 3, 4, or 6; thus, trisomy per se does not cause these changes. B-A translocations involving the long arm and the short arm of chromosome 5 were used to further locate this factor(s). Altering the number of copies of the short arm of chromosome 5 had no detectable effect on the fatty acids measured; however, altering the number of copies of the long arm of chromosome 5 produced the same alterations as trisomy of chromosome 5. Thus, this factor(s) is in the long arm of chromosome 5.