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Setti PG, Borra RC, Sassi FDMC, Cioffi MDB, Fukushima HCS. Zebrafish ( Danio rerio) Gynogenetic Production by Heat Shock: Comparison Between Mitotic and Meiotic Treatment. Zebrafish 2023; 20:181-188. [PMID: 37527193 DOI: 10.1089/zeb.2023.0013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/03/2023] Open
Abstract
Inbred species are useful resources for a variety of biomedical research applications. To create isogenic zebrafish, it is feasible to stop meiosis II (repeatedly) or mitosis (two times) in a haploid embryo by applying pressure or by delivering a heat shock, respectively. In this study, to improve the repeatability, we suggest a less complicated approach based on sperm ultraviolet-C (UV-C) exposure for a shorter period followed by heat shock at various temperatures, eliminating the use of pressure in meiotic therapy since heat shock is more accessible to laboratories. In this study, the survivability rates of meiotic (Mei) and mitotic (Mit) gynogenesis offspring produced by various combinations of irradiation (28.5, 105, and 210 mJ/cm2) and temperature (Mei: 40.40°C, 40.60°C, or 40.90°C; Mt: 41.40°C, 41.90°C, or 42.45°C) were compared with diploid (C) and haploid (H) controls. Our findings demonstrated that 40.60°C and 41.90°C were the most suitable temperatures to produce meiotic and mitotic gynogenesis, respectively, whereas 28.5 mJ/cm2 was more successful in ensuring haploid embryos. As a result, we deduced that meiotic gynogenesis produces more viable offspring than the mitotic approach and requires a lower temperature to maintain the second polar body.
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Affiliation(s)
- Príncia Grejo Setti
- Department of Genetic and Evolution, Federal University of São Carlos, São Carlos, Brazil
| | - Ricardo Carneiro Borra
- Department of Genetic and Evolution, Federal University of São Carlos, São Carlos, Brazil
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Rivers N, Daly J, Temple-Smith P. New directions in assisted breeding techniques for fish conservation. Reprod Fertil Dev 2021; 32:807-821. [PMID: 32527372 DOI: 10.1071/rd19457] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Accepted: 04/26/2020] [Indexed: 12/13/2022] Open
Abstract
Fish populations continue to decline globally, signalling the need for new initiatives to conserve endangered species. Over the past two decades, with advances in our understanding of fish germ line biology, new exsitu management strategies for fish genetics and reproduction have focused on the use of germ line cells. The development of germ cell transplantation techniques for the purposes of propagating fish species, most commonly farmed species such as salmonids, has been gaining interest among conservation scientists as a means of regenerating endangered species. Previously, exsitu conservation methods in fish have been restricted to the cryopreservation of gametes or maintaining captive breeding colonies, both of which face significant challenges that have restricted their widespread implementation. However, advances in germ cell transplantation techniques have made its application in endangered species tangible. Using this approach, it is possible to preserve the genetics of fish species at any stage in their reproductive cycle regardless of sexual maturity or the limitations of brief annual spawning periods. Combining cryopreservation and germ cell transplantation will greatly expand our ability to preserve functional genetic samples from threatened species, to secure fish biodiversity and to produce new individuals to enhance or restore native populations.
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Affiliation(s)
- Nicola Rivers
- Department of Obstetrics and Gynaecology, School of Clinical Sciences, Monash University, Melbourne, Vic. 3168, Australia; and Corresponding author.
| | - Jonathan Daly
- Smithsonian Conservation Biology Institute, Front Royal, VA 22360, USA; and Hawaii Institute of Marine Biology, 46-007 Lilipuna Road, Kaneohe, HI 96744, USA
| | - Peter Temple-Smith
- Department of Obstetrics and Gynaecology, School of Clinical Sciences, Monash University, Melbourne, Vic. 3168, Australia
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Glazier DS. Genome Size Covaries More Positively with Propagule Size than Adult Size: New Insights into an Old Problem. BIOLOGY 2021; 10:270. [PMID: 33810583 PMCID: PMC8067107 DOI: 10.3390/biology10040270] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Revised: 03/18/2021] [Accepted: 03/23/2021] [Indexed: 12/17/2022]
Abstract
The body size and (or) complexity of organisms is not uniformly related to the amount of genetic material (DNA) contained in each of their cell nuclei ('genome size'). This surprising mismatch between the physical structure of organisms and their underlying genetic information appears to relate to variable accumulation of repetitive DNA sequences, but why this variation has evolved is little understood. Here, I show that genome size correlates more positively with egg size than adult size in crustaceans. I explain this and comparable patterns observed in other kinds of animals and plants as resulting from genome size relating strongly to cell size in most organisms, which should also apply to single-celled eggs and other reproductive propagules with relatively few cells that are pivotal first steps in their lives. However, since body size results from growth in cell size or number or both, it relates to genome size in diverse ways. Relationships between genome size and body size should be especially weak in large organisms whose size relates more to cell multiplication than to cell enlargement, as is generally observed. The ubiquitous single-cell 'bottleneck' of life cycles may affect both genome size and composition, and via both informational (genotypic) and non-informational (nucleotypic) effects, many other properties of multicellular organisms (e.g., rates of growth and metabolism) that have both theoretical and practical significance.
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Park IS, Gil HW. Comparative Analysis of Fluctuating Asymmetry between Ploidy and Sex in Marine Medaka, Oryzias dancena. Dev Reprod 2018; 22:275-281. [PMID: 30324164 PMCID: PMC6182228 DOI: 10.12717/dr.2018.22.3.275] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Revised: 08/16/2018] [Accepted: 09/03/2018] [Indexed: 11/17/2022]
Abstract
The purpose of this study is to examine fluctuating asymmetry of eye diameter, maxilla length, operculum length, and the number of pectoral fin ray and pelvic fin ray between ploidy and sex in diploid and triploid marine medaka, Oryzias dancena. In all experimental groups, eye diameter and maxilla length showed no significant difference between left side and right side (p>0.05). Results of operculum length in triploid male group and pectoral fin ray's number in diploid male group showed similarity ones with results of operculum length in triploid female group and pectoral fin ray's number in diploid female group (p<0.05). However, the operculum length in diploid male group and pectoral fin ray's number in triploid male group showed consinderable difference with those of operculum length in diploid female group and pectoral fin in triploid female group. Findings of pelvic fin ray's number in all groups were similar to those of pectoral fin ray's number in all groups (p<0.01).
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Affiliation(s)
- In-Seok Park
- Division of Marine Bioscience, College of
Ocean Science and Technology, Korea Maritime and Ocean University,
Busan 49112, Korea
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Park IS, Gil HW, Kim DS. Morphometric Characteristics of Diploid and Triploid Marine Medaka, Oryzias dancena. Dev Reprod 2018; 22:183-192. [PMID: 30023468 PMCID: PMC6048304 DOI: 10.12717/dr.2018.22.2.183] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 04/19/2018] [Accepted: 05/20/2018] [Indexed: 11/17/2022]
Abstract
The morphometric truss characteristics and classical dimensions of the marine
medaka, Oryzias dancena, that might distinguish diploid and
triploid fish were examined. Significant differences in all the classical and
truss dimensions of the diploid and triploid fish were observed in both sexes
(p<0.01). All the dimensions of the triploid fish
were greater than those of the diploid fish. The triploid marine medaka shows
sexual dimorphism in these characters, and the sexual dimorphism of the triploid
marine medaka is similar to that of the diploid marine medaka. Thus, when their
classical dimension and truss dimension was measured, the growth of triploid
marine medaka is faster than that of the diploid fish, and it displays clear
sexual dimorphism, with male fish having longer dorsal and anal fins than female
fish.
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Affiliation(s)
- In-Seok Park
- Division of Marine Bioscience, College of Ocean Science and Technology, Korea Maritime and Ocean University, Busan 49112, Korea
| | | | - Dong Soo Kim
- Dept. of Marine Bio-Material & Aquaculture, Pukyung National University, Busan 48513, Korea
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Lee HB, Kim DS, Gil HW, Park IS. Pysiological Responses of Diploid and Triploid Far Eastern Catfish, Silurus asotus to Water Temperature Stress. Dev Reprod 2018; 22:165-174. [PMID: 30023466 PMCID: PMC6048303 DOI: 10.12717/dr.2018.22.2.165] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2018] [Revised: 04/10/2018] [Accepted: 05/30/2018] [Indexed: 11/30/2022]
Abstract
The aim of study is to contribute to this knowledge-base by investigating the respiratory function, the metabolic rate and the difference of physiological responses un-der low water temperature (20℃→15℃) stress be-tween diploid and triploid far eastern catfish, Silurus asotus. During the 48 hrs of water temperature stress exposure time, the respiratory frequencies, CO2 and NH4+ concentrations of diploid had higher values than those of triploid (p<0.05). However, pH of triploid was higher than those of diploid (p<0.05), and oxygen consumption rate was not different between diploid and triploid (p>0.05). The level of plasma cortisol and plasma glucose of triploid was lower than those of the diploid (p<0.05). However, in case of lactic acid, there were not significant between triploid and diploid (p>0.05). These results suggest that diploid was more sensitive for low water temperature stress response than triploid in this species.
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Affiliation(s)
- Hyo Bin Lee
- Dept. of Fisheries Biology Center for Risk
Assessment of Oceans and Fisheries Living Modified Organisms, Pukyong National
University, Busan 48513, Korea
| | - Dong Soo Kim
- Dept. of Marine Bio-Materials &
Aquaculture, Pukyong National University, Busan 48513,
Korea
| | | | - In-Seok Park
- Division of Marine Bioscience, College of
Ocean Science and Technology, Korea Maritime and Ocean University,
Busan 49112, Korea
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Gil HW, Lee TH, Han HJ, Park IS. Comparative Analysis of Tissue and Cell Cycle on the Far Eastern Catfish, Silurus asotus between Diploid and Triploid. Dev Reprod 2017; 21:193-204. [PMID: 28785740 PMCID: PMC5532311 DOI: 10.12717/dr.2017.21.2.193] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Revised: 05/20/2017] [Accepted: 05/24/2017] [Indexed: 11/27/2022]
Abstract
The influence of triploidization on histological characteristics of retina, trunk
kidney, liver and midgut tissue, and cell cycle of tail fin and gill tissue in
far eastern catfish, Silurus asotus were analyzed. In the
infertile triploid fish, the nucleus and/or cell size of secondary proximal
tubule cells of trunk kidney, hepatocyte and midgut epithelium are much larger
than those of the corresponding cells in the diploid fish
(P<0.05). However, triploid tissue showed fewer number of
outer nuclear layer in retina and nuclei in secondary proximal tubule of trunk
kidney than those for diploid tissue. The mean percentages of the
Gl-, the S- and the G2+M-phase fractions were 92.5%, 3.2%
and 4.3% in tail fin tissue of diploid, and 93.4%, 2.6% and 4.0% in those of
triploid, respectively. There were no significant differences in the percentages
of each cell cycle fraction between diploid and triploid. The mean percentages
of each phase fractions were 75.1%, 11.1% and 13.8% in gill tissue of diploid
and 85.2%, 8.9% and 5.9% in those of triploid, respectively. The differences of
cell cycle between tail fin tissue and gill tissue were statistically
significant in diploid and triploid (P<0.05). Also, the
differences between diploid and triploid were statistically significant in tail
fin tissue and gill tissue (P<0.05). Cyclin D1 and cyclin E
expressions were not significantly difference between gill tissue and tail fin
tissue, and protein expressions of induced triploid were higher than those of
diploid. Results from this study suggest that some characteristics in the
triploid exhibiting larger cell and nucleus size with fewer number of cell than
diploid can be used as an indicator in the identification of triploidization and
ploidy level in far eastern catfish.
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Affiliation(s)
- Hyun Woo Gil
- Division of Marine Bioscience, College of Ocean Science and Technology, Korea Maritime and Ocean University, Busan 49112, Korea
| | - Tae Ho Lee
- Division of Marine Bioscience, College of Ocean Science and Technology, Korea Maritime and Ocean University, Busan 49112, Korea
| | - Ho Jae Han
- College of Veterinary Medicine and Research Institute of Veterinary Science, Seoul National University, Seoul 08826, Korea
| | - In-Seok Park
- Division of Marine Bioscience, College of Ocean Science and Technology, Korea Maritime and Ocean University, Busan 49112, Korea
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Park IS, Gil HW, Lee TH, Nam YK, Kim DS. Comparative Study of Growth and Gonad Maturation in Diploid and Triploid Marine Medaka, Oryzias dancena. Dev Reprod 2016; 20:305-314. [PMID: 28144636 PMCID: PMC5270606 DOI: 10.12717/dr.2016.20.4.305] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2016] [Revised: 11/19/2016] [Accepted: 12/12/2016] [Indexed: 01/18/2023]
Abstract
The marine medaka, Oryzias dancena is a suitable sample as a laboratory animal
because it has a small size and clearly distinguishes between female and male. Data on the growth
and maturity of the diploid and triploid sea cucurbit species suitable for laboratory animals are
very useful for studying other species. Triploidy was induced in the marine medaka by cold shock
treatment (0°C) of fertilized eggs for 45 min, applied two minutes after fertilization. The diploid
and triploid male fish were larger than their female counterparts
(P<0.05), and the concentrations of thyroid stimulating
hormone (TSH) and thyroxine (T4) were higher in the induced triploids over 1 year
(P<0.05). In both the diploid and tri-ploid groups the
concentrations of TSH and T4 were higher in the male fish than in the females
(P<0.05), while the testo-sterone and estradiol-17ß
concentrations in the induced triploids were lower than in the diploids
(P<0.05). The gonadosomatic index (GSI) of the triploid
fish was lower than that for the diploids, and the GSI for females in each ploidy group were higher
than that for the males. For both groups the GSI was highest at 4 months of age, and decreased
thereafter to 12 months. Analysis of the gonads of one-year-old triploid fish suggested that the
induction of triploidy probably causes sterility in this species; this effect was more apparent in
females than in males.
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Affiliation(s)
- In-Seok Park
- Division of Marine Bioscience, College of Ocean Science and Technology, Korea Maritime and Ocean University, Busan 49112, Korea
| | - Hyun Woo Gil
- Division of Marine Bioscience, College of Ocean Science and Technology, Korea Maritime and Ocean University, Busan 49112, Korea
| | - Tae Ho Lee
- Division of Marine Bioscience, College of Ocean Science and Technology, Korea Maritime and Ocean University, Busan 49112, Korea
| | - Yoon Kwon Nam
- Institute of Marine Living Modified Organism (iMLMO), Pukyung National University, Busan 48513, Korea
| | - Dong Soo Kim
- Institute of Marine Living Modified Organism (iMLMO), Pukyung National University, Busan 48513, Korea
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Embryonic and larval developmental stages of African giant catfish Heterobranchus bidorsalis (Geoffroy Saint Hilaire, 1809) (Teleostei, Clariidae). SPRINGERPLUS 2014; 3:677. [PMID: 25512884 PMCID: PMC4254889 DOI: 10.1186/2193-1801-3-677] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Accepted: 11/11/2014] [Indexed: 11/25/2022]
Abstract
The dearth of African giant catfish Heterobranchus bidorsalis seeds poses great threat to its aquaculture and biodiversity, hence detailed knowledge and understanding of its embryology is indispensable for its artificial propagation and conservation programmes. Photomicrographs of extruded oocyte through all developmental cell stages of live embryo to larval stage are documented with the aid of a light microscope. The optical transparency of the developing embryo enabled us to describe its deep structures, distinctive features and characterize the stages pictorially. Extruded oocyte had a mean diameter of 1 ± 0.1 mm, ~20% increase when hydrated, and bounded by double thin perivitelline membranes. The first mitotic cleavage occurred at 69 min post-fertilization (pf) resulting in 2, 4 (2 × 2 array of cells), 8 (2 × 4), 16 (4 × 4), 32 (4 × 8), 64 (2 × 4 × 8) blastomeres, then developed to morula, blastula and gastrula stages. Blastula was featured by formation of enveloping layer and yolk syncytial layer. Onset of epiboly at 3 h 57 min depicted the commencement of gastrula while closure of blastopore at 11 h 8 min marked its completion. Neurulation period was distinct from segmentation where organogenesis was fully active. Embryo sudden muscular contraction was noticed at ~17 h pf, increased prior to hatching with caudal locomotion firstly at 42 s interval. Heartbeat of embryo commenced at ~1 h before its unique eclosion at average of 72 beats/min while first larva emerged at 21 h at a controlled temperature of 28.5 ± 0.5°C. Mean total length (TL) of larvae and their pouch thickness were 5 ± 1 mm and 0.05 ± 0.02 mm respectively. 1 –day old larvae revealed 8 distinctive neuromeres and by day 3, epicanthus folds of the eyes were fully uncovered; and thereafter commenced exogenous feeding. At day 4, larvae recorded mean TL of 9 ± 1 mm and 15 caudal fin rays. The fin bifurcation to dorsal and adipose fins was observed at third and half weeks post-hatchability with the dorsal fin length to adipose fin was 1.7:1. This study, for the first time, presents significant morpho-sequential developmental stages of H. bidorsalis and registers its unique form of eclosion.
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Alonso M, Tabata YA, Rigolino MG, Tsukamoto RY. Effect of induced triploidy on fin regeneration of juvenile rainbow trout, Oncorhynchus mykiss. THE JOURNAL OF EXPERIMENTAL ZOOLOGY 2000; 287:493-502. [PMID: 11110163 DOI: 10.1002/1097-010x(20001201)287:7<493::aid-jez5>3.0.co;2-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Triploidy was induced in the rainbow trout in order to evaluate whether the altered numbers and sizes of triploid cells could modify fin regeneration. Amputation of one lobe of the tail fin of diploid and triploid juveniles resulted in regeneration for experimentals and controls. Nevertheless, both rate and frequency of regeneration in triploids were significantly increased as compared with diploids, a fact that can be attributed to the increased nuclear and cellular volume in a wide range of tissues, whereas the cell numbers were reduced. These data suggest that a great deal of interesting and important research could be done using triploid animals as experimental models for studying the regeneration of appendages.
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Affiliation(s)
- M Alonso
- Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, Brazil.
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Mol K, Byamungu N, Cuisset B, Yaron Z, Ofir M, Mélard C, Castelli M, Kühn ER. Hormonal profile of growing male and female diploids and triploids of the blue tilapia,Oreochromis aureus, reared in intensive culture. FISH PHYSIOLOGY AND BIOCHEMISTRY 1994; 13:209-218. [PMID: 24198191 DOI: 10.1007/bf00004359] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 03/29/1994] [Indexed: 06/02/2023]
Abstract
Triploidy as a result of thermal shock exposure of fertilized eggs decreases the growth rate ofOreochromis aureus as compared to their diploid controls, but this is due to the higher female ratio present in triploids (86%) and the lower growth rate of females. When females and males are considered separately, the growth rate is not significantly different in diploids and triploids. Since triploidy results in a malfunctioning steroidogenesis in females (mainly testosterone (T) and 17β-estradiol (E2)), but does not affect the growth rate, it is concluded that female gonadal steroids do not influence growth unless in pharmacological concentrations. These low levels of gonadal steroids are generally accompanied by higher levels of gonadotropin (GtH), but the difference is not always significant.Despite their lower growth rate diploid females have higher plasma concentrations of growth hormone (GH) during several months compared to the triploid females and diploid males. 3,5,3'-triiodo-L-thyronine (T3) levels, however, are comparable between diploid and triploid females (except for 1 month), but higher in diploid males in 4 of the 5 months studied. 11-ketotestosterone (11kT) is always higher in males. These results indicate that the higher growth rate of males may be related to the high circulating levels of T3 and 11kT.
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Affiliation(s)
- K Mol
- Laboratory of Comparative Endocrinology, Catholic University of Leuven, Naamsestraat 61, B-3000, Leuven, Belgium
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Hussain MG, Chatterji A, McAndrew BJ, Johnstone R. Triploidy induction in Nile tilapia, Oreochromis niloticus L. using pressure, heat and cold shocks. TAG. THEORETICAL AND APPLIED GENETICS. THEORETISCHE UND ANGEWANDTE GENETIK 1991; 81:6-12. [PMID: 24221152 DOI: 10.1007/bf00226105] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/1990] [Accepted: 07/19/1990] [Indexed: 06/02/2023]
Abstract
The results of a study aimed at the identification of treatment optima for triploidy induction in recently fertilised Oreochromis niloticus L. eggs by altering the intensity, duration and timing of application of pressure, heat and cold shocks are reported. Preliminary, but not directly comparable, trials suggested the following treatments to be close to the individual agent optima. Pressure: 8,000 psi 2-min duration applied 9 min after fertilisation (a.f.); heat: 41 °C, 3.5-min duration applied 5 min a.f., cold: 9°C, 30-min duration applied 7 min a.f. In a directly comparable trial in which the eggs of eight different females were separately exposed to the optimum shocks listed above, individual triploid yields were more variable following cold shocks and mean triploid yields were, therefore, higher following pressure and heat shock. These and other results obtained are presented and the light they shed on the timing of the second meiotic division in this species is discussed.
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Affiliation(s)
- M G Hussain
- Institute of Aquaculture, Stirling University, FK9 4LA, Stirling, Scotland
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14
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Don J, Avtalion RR. Production of F1 and F 2 diploid gynogenetic tilapias and analysis of the "Hertwig curve" obtained using ultraviolet irradiated sperm. TAG. THEORETICAL AND APPLIED GENETICS. THEORETISCHE UND ANGEWANDTE GENETIK 1988; 76:253-259. [PMID: 24232113 DOI: 10.1007/bf00257853] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/1987] [Accepted: 02/09/1988] [Indexed: 06/02/2023]
Abstract
In this study, a Hertwig effect with a non-typical biphasic curve was obtained using sperm irradiated with increasing intensities of UV. The first phase of the UV curve appeared to be quite different from that normally demonstrated using γ or x-ray irradiation. This difference is characterised throughout the length of the first phase by (1) low and stable embryo hatching rates of about 3.5%, and (2) exclusive formation of haploid embryos at any irradiation intensity. Additionally, at both phases, the ability of the sperm to induce morula formation was not affected at all, and no aneuploidy nor chromosomal fragments could be seen. Therefore, it was suggested that in this fish the lethal effect of UV irradition on sperm is mainly expressed on early differentiative events during embryogenesis, which lead to a degeneration of the embryos during early stages of their development. The possible mechanism by which haploidy is achieved during the first phase is discussed. Two generations of diploid gynogenetic tilapias were induced by activating Oreochromis aureus eggs with UV-irradiated O. niloticus sperm and by using the heat-shock technique, at optimized conditions, for the prevention of the second polar body extrusion. Species specific dominant genetic markers (serum esterases and tail striation) were used to confirm the exclusive content of the maternal genome in gynogenetic offspring. Very low survival rates (0.36%) were shown in F1 gynogenetic fish as well as a high incidence of malformations among survivors. In the second gynogenetic generation, both significantly higher survival rates (3.6%) and a considerably reduced incidence of malformations were obtained. We suggest that low frequencies of recombination occur in this species and cause a rapid increase in the inbreeding level. This is followed by the expression of lethal and defective genes that are considerably reduced after second generation selection.
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Affiliation(s)
- J Don
- Laboratory of Fish Immunology and Genetics, Department of Life Sciences, Bar-Ilan University, Ramat-Gan, Israel
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