Diploid Siblings Research Articles

Syntaxin1A overexpression and pain insensitivity in individuals with 7q11.23 duplication syndrome.

Genetic modifications leading to pain insensitivity phenotypes, while rare, provide invaluable insights into the molecular biology of pain and reveal targets for analgesic drugs. Pain insensitivity typically results from Mendelian loss-of-function mutations in genes expressed in nociceptive (pain-sensing) dorsal root ganglion (DRG) neurons that connect the body to the spinal cord. We document a pain insensitivity mechanism arising from gene overexpression in individuals with the rare 7q11.23 duplication syndrome (Dup7), who have 3 copies of the approximately 1.5-megabase Williams syndrome (WS) critical region. Based on parental accounts and pain ratings, people with Dup7, mainly children in this study, are pain insensitive following serious injury to skin, bones, teeth, or viscera. In contrast, diploid siblings (2 copies of the WS critical region) and individuals with WS (1 copy) show standard reactions to painful events. A converging series of human assessments and cross-species cell biological and transcriptomic studies identified 1 likely candidate in the WS critical region, STX1A, as underlying the pain insensitivity phenotype. STX1A codes for the synaptic vesicle fusion protein syntaxin1A. Excess syntaxin1A was demonstrated to compromise neuropeptide exocytosis from nociceptive DRG neurons. Taken together, these data indicate a mechanism for producing "genetic analgesia" in Dup7 and offer previously untargeted routes to pain control.

Performance and Fecundity of Triploid Eastern Oysters Crassostrea virginica (Gmelin, 1791) and Challenges for Tetraploid Production

The goal of this study was to initiate a program for producing Florida tetraploid founders to meet the needs of the fast-growing oyster farming industry in the Gulf of Mexico. The objectives were to: (1) produce chemically induced triploids originated from Florida wild stocks and (2) screen and identify triploid females for induction of tetraploid founders. By use of Florida wild stocks from different locations, chemically induced triploids were produced in three spawn groups. Compared with diploid siblings, triploids at juvenile stages did not show significant fast growth (shell metrics and body weight) in every group, but at 1-y-old in spawning season did show significantly faster growth (P < 0.0001) than their diploid siblings. Among triploids, the occurrence of female averaged 1.66% (43 out of 2,597 triploids), ranging from 0.68%, 1.2%, and 4.26% in the three spawn groups. Oocytes from these 43 triploid females averaged 214,715 per female ranging from <100 to 1,800,000. Flow cytometry analysis of gonad from the nonfemale triploids (n = 186) showed five types of ploidy composition. A majority of these nonfemale triploids (66.1%) showed 3n only, indicating no gametogenesis occurred, and other different ploidy compositions showed initiation of gametogenesis with different chromosome segregations. Tetraploid induction was conducted by fertilizing the oocytes from triploid females with sperm from diploid males followed by polar body inhibition. The fertilization varied greatly ranging from 12% to 91%, and survival to D-stage swimming larvae ranged from 0% to 24%. Ploidy of pooled D-stage larvae indicated a tetraploid composition ranging from 38% to 80%. Heavy mortality of putative tetraploid larvae occurred at about 7–9 days and juveniles (1, 3, and approximately 200) were harvested in three groups. Unfortunately, these juveniles were lost during a hurricane in October 2018 at the growout site of one collaborating farm before individual ploidy examination. Although no confirmed tetraploid founders were harvested, the occurrence and fecundity of triploid females were documented in detail, which should be useful for future development of tetraploid stock for oyster aquaculture.

Performance of triploid Haliotis discus hannai cultured in a subtropical area using sea-based suspended systems

Considerable research has been conducted on the induction of triploids in Haliotis discus hannai. However, very few studies have focused on the performance of triploids. In this study, we present the first report of a comprehensive comparative field study on triploids of H. discus hannai and their diploid siblings cultivated for up to 30 months on a sea-based suspended system in a subtropical environment. Two types of triploids were created using cytochalasin-B (CB) and 6-dimethylaminopurine (6-DMAP). The triploid percentages were 89.10% (CB group) and 100.00% (6-DMAP group) at the larval stage, which fell to 28.58% (CB group) and 86.91% (6-DMAP group) at 30 months post-fertilization (mpf). The survival rates in both treatments were similar to that of the control group, except for the 6-DMAP group at 9 mpf and both treated groups during the first high-temperature period (Jun-Dec), when significant decreases in survival were observed (P < 0.05). Surprisingly, there was no difference in thermal tolerance between triploids and diploids through the assessment of heat adhesion duration (P > 0.05). The growth of the triploids differed across the two ploidy levels. The triploids within the CB group did not differ from control diploids throughout the observation period (P > 0.05), whereas triploids in the 6-DMAP group showed superior growth in body weight at 20 mpf (P < 0.05). After the end of the maturation season (30 mpf), a significant increase (19.57%) in foot muscle weight was found in the 6-DMAP group triploids, and a significant increase (7.22%) in the foot muscle-soft tissue index (FMSI) was found in the CB group triploids in comparison to diploid individuals (P < 0.05). The advantage of meat yield may be attributed to the hypothesis of the diversion of energy from gonadal to somatic growth. Despite the normal sex ratio (1:1) of triploids, their reproductive potential was significantly reduced, showing infertility in the females with highly reduced numbers of oocytes or abnormal oogonia and sterility in the males with an absence of spermatozoa. Our study confirms a definite advantage in the meat yield of triploid H. discus hannai and provides insights for the commercial promotion of triploid strains in the abalone aquaculture industry in southern China.

Reduced growth may be linked to lower aerobic scope in juvenile triploid white sturgeon (Acipenser transmontanus)

Previous studies have provided evidence of a reduced aerobic metabolic capacity, both at the cellular (metabolic enzyme activity) and the whole organism (aerobic scope) level in juvenile triploid white sturgeon, compared to diploid siblings. The downstream costs of this reduced metabolic capacity are still unclear, yet a lower aerobic scope suggests triploid white sturgeon likely have less energy to allocate to biological processes like growth and development. We conducted a 15-week growth trial to assess energy allocation to somatic growth in 2-month-old diploid and triploid white sturgeon. Spontaneous swimming activity, hepatosomatic index, condition factor, and deformities were also measured throughout the growth trial as indices of energy allocation to activity and fish condition. In general, our results indicate that triploid white sturgeon may have less energy available for processes beyond basal maintenance. This could be linked to a reduced overall performance as evidenced by lower weights and more deformities when compared with their diploid counterparts. However, many indices were still mostly unaffected by triploidy (condition factor, hepatosomatic index, and swimming activity). Whether this lower growth performance seen in juvenile triploid white sturgeon continues through sub-adulthood, puberty and final maturation requires further long-term studies.

Transcriptome expression profiles between diploid and triploid Pacific abalone (Haliotis discus hannai) juveniles in response to acute heat-stress and hypoxia treatments.

With an increasing interest for the use of triploids in abalone aquaculture, it is crucial to understand their physiological responses to environmental stress, particularly such as heat-stress and hypoxia, which are significant factors that cause adverse effects on the efficiency and capacity of farming practice in abalone production. However, nothing is known about gene expression of triploid abalone to modulate physiological responses under different environmental stresses. Transcriptomic response to the acute heat-stress and hypoxia were explored in hepatopancreas of diploid and triploid Pacific abalone (Haliotis discus hannai) juveniles. A total of 316 million clean reads were de novo assembled into 271,039 contigs, of which a transcriptome with 209,974 non-redundant transcripts was produced. Using generalized fold change (GFOLD) algorithm with a cut-off │GFOLD value│>4, we identified differentially expressed transcripts (DETs) from diploid and triploid abalone in responses to acute heat-stress and hypoxia treatments, respectively. Comparative analysis of the identified DETs revealed alteration of transcript expression profile, level, and process in triploid abalone compared to their diploid siblings. Thus, our study will provide not only comprehensive insight into understanding of the transcriptional regulation to environmental stresses in triploid abalone but a framework for efficient management of triploid abalone aquaculture.

Chromosome aberrations in pressure-induced triploid Atlantic salmon

BackgroundTriploid organisms have three sets of chromosomes. In Atlantic salmon, hydrostatic pressure treatment of newly fertilized eggs has been extensively used to produce triploids which are functionally sterile due to their unpaired chromosomes. These fish often perform poorly on commercial farms, sometimes without explanation. Inheritance patterns in individuals subjected to pressure treatment have not been investigated in Atlantic salmon thus far. However, work on other species suggests that this treatment can result in aberrant inheritance. We therefore studied this in Atlantic salmon by genotyping 16 polymorphic microsatellites in eyed eggs and juveniles which had been subjected to pressure-induction of triploidy. Communally reared juveniles including fish subjected to pressure-induction of triploidy and their diploid siblings were included as a control.ResultsNo diploid offspring were detected in any of the eggs or juveniles which were subjected to hydrostatic pressure; therefore, the induction of triploidy was highly successful. Aberrant inheritance was nevertheless observed in 0.9% of the eggs and 0.9% of the juveniles that had been subjected to pressure treatment. In the communally reared fish, 0.3% of the fish subjected to pressure treatment displayed aberrant inheritance, while their diploid controls displayed 0% aberrant inheritance. Inheritance errors included two eyed eggs lacking maternal DNA across all microsatellites, and, examples in both eggs and juveniles of either the maternal or paternal allele lacking in one of the microsatellites. All individuals displaying chromosome aberrations were otherwise triploid.ConclusionsThis is the first study to document aberrant inheritance in Atlantic salmon that have been subjected to pressure-induction of triploidy. Our experiments unequivocally demonstrate that even when induction of triploidy is highly successful, this treatment can cause chromosome aberrations in this species. Based upon our novel data, and earlier studies in other organisms, we hypothesize that in batches of Atlantic salmon where low to modest triploid induction rates have been reported, aberrant inheritance is likely to be higher than the rates observed here. Therefore, we tentatively suggest that this could contribute to the unexplained poor performance of triploid salmon that is occasionally reported in commercial aquaculture. These hypotheses require further investigation.

Why are triploid zebrafish all male?

Adult triploid zebrafish Danio rerio has previously been reported to be all male. This phenomenon has only been reported in one other gonochoristic fish species, the rosy bitterling Rhodeus ocellatus, despite the fact that triploidy is induced in numerous species. To investigate the mechanism responsible, we first produced triploid zebrafish and observed gonad development. Histological sections of juvenile triploid gonads showed that primary growth oocytes were able to develop in the juvenile ovary, but no cortical alveolus or more advanced oocytes were found. All adult triploids examined were male (n = 160). Male triploids were able to induce oviposition by diploid females during natural spawning trials, but fertilization rates were low (1.0 ± 3.1%) compared with diploid male siblings (67.4 ± 16.6%). The embryos produced by triploid sires were aneuploid with a mean ploidy of 2.4 ± 0.1n, demonstrating that triploid males produce aneuploid spermatozoa. After confirming that adult triploids are all male, we produced an additional batch of triploid zebrafish and exposed them (and a group of diploid siblings) to 100 ng/L estradiol (E2) from 5 to 28 dpf. The E2 treated triploids and nontreated triploids were all male. The nontreated diploids were also all male, but the E2 treated diploids were 89% female. This demonstrates that triploidyacts downstream of estrogen synthesis in the sex differentiation pathway to induce male development. Based on this and the observations of juvenile gonad development in triploids, we suggest that triploidy inhibits development of oocytes past the primary growth stage, and this causes female to male sex reversal.

Quality characteristics and consumer acceptance of diploid and triploid cold smoked Atlantic salmon reared at 5, 10 and 15 °C

This study determined the processing characteristics, textural and colorimetric properties, NaCl content and consumer's acceptability of dry salted cold smoked triploid Atlantic salmon (average weight of 1.6 ± 0.3 kg) reared at different temperatures (5, 10 and 15 °C). As a reference, diploid siblings kept and processed under equal conditions was used. Ploidy did not affect the raw material biometrics but increased holding temperature gave increased blood lactate and decreased muscle pH at point of death. Triploid Atlantic salmon was found to be suitable for cold smoke processing but the differences in quality between diploid and triploid was significant. Cold smoked triploid salmon have on average lower processing yield, higher weight loss throughout processing and storage, and was softer as compared to diploids. Ploidy did however not affect the NaCl content. A consumer test did also distinguish between cold smoked diploid and triploid salmon originally kept at 10 °C. In addition, increased holding temperature was found to give a step-wise lower weight loss during processing and significant darker fillets after cold smoking and storage.

Single or dual experimental infections with Vibrio aestuarianus and OsHV-1 in diploid and triploid Crassostrea gigas at the spat, juvenile and adult stages

French production of the Pacific cupped oyster, Crassostrea gigas, is currently threatened by two pathogens, OsHV-1 and V. aestuarianus. While oysters selected for their higher resistance to OsHV-1 are now available for the industry, the impact of V. aestuarianus on such oysters is unknown, especially for triploids. In addition, experimental infection has used the virus or the bacteria alone, but there have been no investigations of dual exposure to these pathogens. This study is the first report of single or dual exposure in spat (Spat1 and Spat2), juvenile and adult naïve oysters. For each of the two stocks evaluated, unselected oysters and oysters selected for their higher resistance to OsHV-1 infection were tested, as well as their triploid siblings of the selected oysters produced using cytochalasin B. We confirmed that resistance to OsHV-1 infection and susceptibility to V. aestuarianus increased with age and size, although selected oysters were not significantly impacted by OsHV-1 whatever their ploidy, size or age. We found different mortality patterns depending on the pathogen tested. The mortality pattern was similar for oysters exposed to OsHV-1 or to both pathogens in the Spat1 trial (4months old and 1.9g). The mortality pattern was similar for oysters exposed to V. aestuarianus or to both pathogens in the Adult trial (25months old and 63.1g). Surprisingly, mortality was much higher (ranging from 75.9% to 100%), in particular for the selected oysters, for the Spat2 (8months old/3.9g) and Juvenile trials (16months old/18.4g) given a dual exposure, regardless of the level of selection for OsHV-1 and the ploidy state. Our findings highlight an important threat for oyster farmers: oysters exposed to both pathogens could experience dramatic mortality rates, even in oysters selected for their higher resistance to OsHV-1. Finally, our study demonstrated for the first time that triploid oysters were more susceptible to experimental challenges with V. aestuarianus at the spat stage than their diploid siblings. However, the difference in mortality between the triploids and diploids remained limited and ranged from 22.9% to 6.6% for spat and adults, respectively with a relatively regularly decrease in the difference with increased age.

Growth and muscle cellularity of diploid and triploid Atlantic cod (Gadus morhuaLinnaeus, 1758) larvae

Summary The aim of this study was to compare somatic growth and muscle fibre development in diploid and triploid siblings of Atlantic cod (Gadus morhua Linnaeus, 1758) during the larval stage. Newly hatched larvae were transferred into 200-L tanks, three tanks per ploidy group (70 larvae L−1, continuous light, gradually increasing seawater temperature 7–11°C and flow rates 50–117 L h−1). Larvae were fed rotifers from 2 to 22 days post hatch (dph), Artemia 19–31 dph and weaned onto a microparticulate diet from 26 dph until the end of the experiment. Measurements of growth (dry weight, standard length) and muscle cellullarity were taken at intervals between 1 and 44 dph. Ploidy groups showed a similar performance throughout the trial, although a marked stagnation in growth was observed for triploids during the weaning from Artemia onto dry feed. Overall, diploid and triploid cod larvae showed a similar development in muscle fibre growth pattern during the experimental period. For both groups, the total number of fast muscle fibres showed a 10-fold increase (from 384 to 3462), whereas the diameter of fast fibre increased from 8.9 to 13.3 μm (mean number from all treatments). Thus, a temporary but significant effect of triploidy on fast muscle fibre growth pattern was observed in 19 dph larvae in terms of fibre size and number, with triploids showing larger mean fast fibre diameter (11.62 ± 0.63 vs. 10.05 ± 0.34) and a lower number of fibres with a diameter <5 μm than their diploid siblings. Thus, this was found to be related to larvae size and to the differences in total fast fibre cross sectional areas rather than to ploidy status. Overall, our results suggest possible deficiencies in nutrients’ digestion and absorption of triploid cod larvae particularly during the transitional period from live food to inert diets.

Growth and gut morphology of diploid and triploid juvenile Atlantic cod (Gadus morhua )

The objective of this paper was to compare the growth and gut morphology of juvenile diploid and triploid Atlantic cod (Gadus morhua) reared under similar conditions. Individually tagged 36-week-old diploid (mean weight 49.3 ± 13.8 g) and triploid (mean weight 43.6 ± 11.2) juvenile cod were measured at intervals during a 29-week growth trial. Data for weight, length, condition factor (K), hepato-somatic index (HSI), gonado-somatic index (GSI), Relative Gut Length (RGL) and pyloric caeca number were collected and results were analysed in relation to ploidy status, gender and family contribution. At the end of the experiment, only one family (M2xF3) had many representatives with a relatively even distribution of sexes and ploidies. Diploid females were significantly heavier and had higher K than triploid females in the M2xF3 family (body weight 371.2 ± 120.2 vs. 298.4 ± 100.7 g; K 1.1 ± 0.1 vs. 0.93 ± 0.1), but no differences were found between diploid and triploid males. In the other families (pooled data), no differences in body weight were found between the ploidy groups. In general, triploids had a shorter intestine (RGL) and fewer pyloric caeca than their diploid siblings regardless of gender suggesting possible impairments in nutrient utilization and growth.

Adult triploid Atlantic salmon (Salmo salar) have higher dietary histidine requirements to prevent cataract development in seawater

The study investigated cataract preventive effects of dietary histidine (His) supplementation in triploid Atlantic salmon during seawater grow-out. Groups of individually PIT tagged diploid (2N) and triploid (3N) postsmolts were fed one of two supplemented dietary histidine levels; low (L, 12.6 g kg−1 diet) or high (H, 17.4 g kg−1 diet) from March to September following their first sea winter. Low severity cataracts were detected in both ploidy prior to supplemented His diet application. Thereafter, 3N-L showed progression of cataract development in the second spring-summer period, while development was inhibited in 3N-H. Severity of cataract showed a strong family effect. A positive correlation between initial triploid seawater growth (weight and TGC) under increasing water temperature and cataract severity was identified as a major risk factor. The relationship was reversed at harvest, where triploids were on average 7.5% smaller than their diploid siblings. Lens N-acetyl-histidine content reflected dietary His inclusion level and cataract severity, although no significant differences in lens His content were evident between ploidy or dietary groups. Results indicate that triploid Atlantic salmon appear to have a higher dietary histidine requirement than diploids and that preventative measures can be taken to mitigate further cataract development.

Gut morphology of diploid and triploid Atlantic cod,Gadus morhua

Summary Little is known about the functional consequences of triploidy in Atlantic cod. This study compared the gut morphology of diploid and triploid offspring of wild and selected broodstock. Three-year-old triploid offspring of wild cod (mean weight 1695 ± 346 g) had approximately 18% fewer pyloric caeca (125 ± 9 vs 172 ± 14, P < 0.001) and a 23% shorter intestine [Relative Gut Length, (RGL); 1.40 ± 0.17 vs 1.81 ± 0.17, P < 0.05] than their diploid siblings (mean weight: 1820 ± 262 g). Two-year-old triploid offspring of selected broodstock (mean weight: 640 ± 64 g) had 20% fewer pyloric caeca (309 ± 17 vs 387 ± 27, P < 0.001) but similar RGL to their diploid siblings (mean weight: 820 ± 69 g). The average number of mucus cells in the columnar epithelium of pyloric caeca was significantly higher in triploid than in diploid cod (54 ± 9 vs 25 ± 5, P < 0.001). There was no correlation between pyloric caeca number and RGL, or between mucus cells and pyloric caeca number, and no significant differences between sexes for any of the measured variables. Overall, the observations highlight some differences in the digestive system of these two ploidy groups that could have an influence on nutrient utilization and performance capacity in triploids compared to diploids.

Growth Performance of Triploid Red Tilapia Reared Under Laboratory Conditions

Triploidy could reduce breeding activity in tilapia without the use of hormones. In this study, the effect of triploidy on survival, growth, and gender of a line of red hybrid tilapia (Oreochromis mossambicus X Oreochromis niloticus) was assessed relative to the performance of diploid siblings. Triploidy was induced by preventing second polar body extrusion by applying either heat or cold shock. Growth was similar for both ploidies during the first 90 days of culture. However, at the age of 120 days, the average body weight of triploids produced by heat shock (215.5 ± 3.61 g) was significantly higher than that of cold shock (192.7 ± 2.6 g) and the diploid control (191.9 ± 1.74 g). Survival among triploids was inferior to diploids. Percentage of males in the triploid population was 82.9% in the heat-shocked treatment group, 54.8% in the cold-shock treatment, and 50% in the diploid control. Maximum attainable weight of red tilapia was calculated by applying the Ford-Walford growth plot: 650 g (heat-shocked triploids), 490 g (cold-shocked triploids), and 440 g in the diploid control.

Triploidy Induction in the Pacific White Shrimp Litopenaeus vannamei: An Assessment of Induction Agents and Parameters, Embryo Viability, and Early Larval Survival

In this study, we trialed 6-dimethylaminopurine (6-DMAP) chemical shocks to induce meiosis I or meiosis II Pacific White shrimp, Litopenaeus vannamei, triploids for the first time, and cold temperature shocks to induce meiosis II L. vannamei triploids as done previously. Inductions were performed on 37 spawnings in total with experiments being progressively designed in a factorial manner to allow optimization of induction parameters. Treatment with a 200-μm 6-DMAP final concentration at 1min post-spawning detection for a 6 to 8min duration resulted in the most consistent induction of chemically induced meiosis I triploids while treatment at 7min 30s post-spawning detection for a 10-min duration resulted in the most consistent induction of chemically induced meiosis II triploids. A cold temperature shock of 11.7°C to 13.25°C (final treatment temperature; spawning water temperature 28.5°C) applied at 8min post-spawning detection for a 4 to 10min duration resulted in the most consistent induction of cold-temperature-induced meiosis II triploids. 6-DMAP shocks resulted in meiosis I induction rates from 29% to 100% in unhatched embryos and 50% in nauplii, and meiosis II induction rates from 65% to 100% in unhatched embryos and 52% to 100% in nauplii. Cold shocks resulted in induction rates from 5% to 100% in unhatched embryos and nauplii. Confocal microscopy analysis of embryos revealed that there are major developmental abnormalities in a large proportion of later stage triploid L. vannamei embryos compared to their diploid sibling controls. Despite this, however, some triploid embryos did appear normal and both shock agents induced small numbers of viable triploid L. vannamei nauplii which were successfully reared to protozoeal stage 3 as confirmed by flow cytometry. Triploids beyond this life-history stage were not observed in the present study as confirmed by flow cytometry at mysis stages. This study adds to our knowledge base of triploid induction in L. vannamei and further highlights the inherent difficulties with triploid embryonic and larval viability in this species.

Parr–smolt transformation in out-of-season triploid Atlantic salmon (Salmo salar L.)

Production of sterile triploid Atlantic salmon (Salmo salar) would appear to be the best strategy to address the growing concerns on environmental impacts of escapees. However, the industry relies on a year round supply of smolts to ensure continual production and to date the production of out-of-season (S0+) triploid smolts has not been reported. The present study demonstrates that S0+ triploid smolts can be produced using an accelerated “square-wave” photoperiod (LL–LD 9.5:14.5–LL) under ambient water temperature. Such a regime advanced the timing of smoltification by 3months (S0+) relative to their siblings under an ambient photoperiod (S1+) as observed through body silvering, fin darkening, decrease in condition and significantly increased gill Na+, K+-ATPase activity. Importantly, triploid S0+ fish smolted 4weeks earlier than their diploid siblings. In S1+ populations, no difference in smolt time was observed although triploid fish also achieved a higher weight. Furthermore, deformity prevalence was very low during the fresh (≤5%) and seawater (≤2.5%) stages within both ploidies mainly represented by spinal deformity and operculum shortening. Family effects for growth and condition were clear, however, no significant family/ploidy interactions were observed although this was based on only two full-sib crosses. These results are promising but there is still a long way to go before triploid can become a commercial reality. Further studies are required to optimize and refine husbandry protocols, define breeding strategies especially regarding family selection and overall better understand triploid salmon physiology.

Ploidy effects on hatchery survival, deformities, and performance in Atlantic salmon ( Salmo salar)

The production of sterile triploid Atlantic salmon ( Salmo salar) may help address the increasing pressure on the industry to reduce potential breeding between farmed escapees and wild fish populations. However, many previous studies have observed poor performance at sea in triploid stocks (growth, survival, and deformity). This may result from poor early hatchery performance and a strong parental effect. Therefore, in the present study, two year classes (2007 and 2008) of mixed sex fish were created (10 males:10 females) to examine ploidy interactions on hatchery performance. Egg batches were divided in two at fertilisation with one group subjected to a hydrostatic pressure shock to induce triploidy. Triploid rate was confirmed at 100% in all groups, verified by red blood cell nucleus length measurements. Survival to hatch did not differ between ploidy. However, reduced survival was found to strongly correlate with gamete quality. During the hatchery phase ploidy significantly affected size at hatch, with diploids generally larger than triploids. Growth advantage of diploids over triploids was only maintained for 6 weeks post-first feeding, with triploids generally out-growing their diploid siblings by the end of the hatchery phase. Deformity prevalence in first feeding stages was generally low (mean < 2%), with no overall effect of ploidy. Our findings show that triploid salmon can perform as well if not better than their diploid siblings. The low incidence of deformity during the hatchery and freshwater phases is also a significant improvement over previous reports in triploid salmon stocks.

Triploidy and full-sib family effects on survival and growth in juvenile Arctic charr ( Salvelinus alpinus)

This study evaluated the survival and growth of juvenile Arctic charr in comparison to their diploid siblings. Eight triploid full-sib families were produced by hydrostatic pressure treatment of eggs (5 min at 65.5 × 10 3 kPa) beginning 210 °C-min post-fertilization. Diploid siblings came from the same eight families, but without pressure treatment. Mean survival from eyed-egg to first size-grading (at 1980 °C-days post-hatch) was 70% for triploids and 84% for diploids. In two growth studies using 4 m 3 tanks containing 100 juveniles per ploidy level of each family, triploidization resulted in higher levels of phenotypic variance for growth traits. Specifically, triploids consistently had smaller mean body weight and fork length than their diploid siblings. Juveniles were first measured at 850 °C-dph and again every four weeks over a 24 week period. The proportion of the overall variance in weight was due to ploidy level in the first tank experiment whereas this variance was due to the effect of family in the second tank experiment. Mean specific growth rates of triploids and diploids were 2.01 and 2.09% for weight and 0.64 and 0.66% for length, respectively, which was not significant. The condition factor of triploids was less than that of diploids at every sampling date, except for the initial assessment. After transfer to a commercial site following completion of the tank trials, the same families were grown until market size (1 kg) and were measured again nine and 11 months after the conclusion of the growth studies. The condition factor of triploids improved at the commercial site and was not different from that of diploids. The difference in weight of triploid and diploid populations was significant at the conclusion of the study. These results indicate that as juveniles, triploids have reduced performance in important aquaculture traits. However, because triploid performance was reduced in a predictable fashion in comparison to sibling diploids, triploids of some full-sib families outperformed diploids of others. Any overall advantage of triploids may not be realized until the diploids begin to mature.

The effects of triploidy on Penaeus (Marsupenaeus) japonicus (Bate) survival, growth and gender when compared to diploid siblings

In this study the effect of triploidy on survival, growth and gender of the Kuruma shrimp, Penaeus (Marsupenaeus) japonicus (Bate), was assessed by making comparisons to diploid sibling performance. Triploidy was induced by preventing polar body II extrusion using 6-dimethylaminopurine (6-DMAP) chemical shock. Four families with a triploid induction rate greater than 70% were reared for approximately 300 days (10 months), during which time their survival, growth, gender ratios and individual ploidy level were assessed. All triploids were found to be female resulting in significantly skewed gender ratios. Males treated with 6-DMAP were either diploid or mosaic (having both diploid and triploid cell populations). 6-DMAP treated shrimp in families 1 and 2 had significantly poorer (P<0.05) survival performance from PL10 to tagging size (PL187) compared to controls. Survival of family 4 control animals from PL10 to tagging size (PL118) was also significantly greater than the treatment animals, however, there was no difference in the survival performance of control and 6-DMAP treated shrimp for family 3 (P>0.05) over the same period. Similarly, for all four families, survival of 6-DMAP treated and control shrimp was not significantly different (P>0.05) from tagging through to assessment age (PL251 for families 1 and 2, and PL173 for families 3 and 4). Treatment with 6-DMAP had a significantly negative effect on weight of females at assessment age when compared to controls of families 1, 2 and 3, and males of families 1 and 4. Diploid females that had received treatment with 6-DMAP were significantly heavier (P<0.05) than triploid females for family 3 at assessment age, and family 4 from assessment age through to the end of the rearing period. The discovery that all triploid P. japonicus are female could be of significant commercial interest in the future, as shrimp growth rates are sexually dimorphic with females growing faster and larger than males. However, triploidy induced by 6-DMAP chemical shock appears to have detrimental effects on growth and survival performance from sub-adult to reproductive size when compared to diploid siblings. The production of only female triploids supports the hypothesis that the female is the heterogametic gender for P. japonicus.

Evaluation of induced triploid shrimp Penaeus ( Fenneropenaeus) chinensis cultured under laboratory conditions

Triploid Penaeus ( Fenneropenaeus) chinensis was successfully produced by heat shock. Their metamorphosis, the relationship between body weight and length and difference in appearance between triploids and their diploid siblings under laboratory culture were studied. Hematological studies showed a smaller number of haemocytes, but larger cell volume, in triploids than in diploids. Triploid shrimp did not show higher growth during the immature stage, but exhibited superior growth during the maturation stage. Characteristics of reproductive organs indicated that triploid shrimp may be sterile and sex ratio can be changed through triploidization of shrimp. This paper summarizes the progress made in triploid shrimp research which would be helpful in understanding more about triploids of crustaceans.