Triploid hard clamsMercenaria mercenariaproduced by inhibiting polar body I or polar bodyII

Abstract

Two types of triploid hard clams Mercenaria mercenaria were produced by inhibiting polar body I (PB1) or polar body II (PB2) with cytochalasin B. Treatments were applied at 22-23°C, with PB1 inhibition starting at 4-7 min postfertilization and ending when PB2 was first observed in control groups, and with PB2 inhibition starting at 17-23 min postfertilization and ending when 80% of control eggs released PB2. Triploid induction success was evaluated by chromosome counting in 2-4 cell embryos and by flow cytometry at larval and juvenile stages. PB2 inhibition produced more triploids (82%-100%) than PB1 inhibition (71%-83%), although the difference was not significant (p ≥ .088). Triploid percentages in PB1-or PB2-inhibited groups showed a small but insignificant decline during the first 6 months. At month 3, PB1 and PB2 triploids were not different from their within-group diploids, but significantly larger than control diploids; PB1 triploids were significantly larger than PB2 triploids (p ≤ .003). At month 6, PB1 triploids were not different from either within-group or control-group diploids, while PB2 triploids were significant larger than both within-group and control diploid; PB1 triploids were smaller than PB2 triploids. At month 16, PB1 and PB2 triploids in one remaining replicate were not different from their within-group diploids. Overall, this study shows that triploids can be efficiently produced by PB1 or PB2 inhibition, and their growth performance relative to diploids is variable depending on age and replicates or parental genotype.

Effect of three triploidy induction methods on the growth and survival of larvae and post-larvae of the Caribbean scallopArgopecten nucleus

“…This effect has been mainly attributed to the total or partial sterility in triploid animals, which allows them to redirect the energy involved in reproduction to somatic growth (Ruiz‐Verdugo, Racotta, & Ibarra, ; Wang, Guo, Allen, & Wang, ; Zhang et al., ). Triploidy in bivalves may be induced by inhibiting the production of the first or second polar body (Beaumont & Fairbrother, ; Yang & Guo, ). Alternatively, triploid individuals can also be produced by crossing tetraploid females (4N) with diploid males (2N) (Guo, DeBrosse, & Allen, ).…”

Effects of salinity on pre- and post-fertilization developmental events in the clam Anomalocardia flexuosa (Linnaeus, 1767)

“…The use of polyploidy has become popular in bivalve aquaculture ( Ma et al, 2019 ), either due to gonadal sterility ( Piferrer et al, 2009 ; Dheilly et al, 2014 ; Zhang et al, 2017 ), to the increase in the cell volume and lack of compensation of cell number ( Guo and Allen, 1994 ), or even to the increased heterozygosity that promote larger and faster growth in bivalves ( Guo et al, 2009 ; Yang and Guo, 2018 ).…”

Triploid induction by hyperosmotic shock in the Yesso scallop, Patinopecten yessoensis

“…We found that inhibiting PB2 resulted in a higher TR than inhibiting PB1 in the Yesso scallop. PB1 inhibition leads to abnormal chromosome segregation during second meiosis, which results in tetraploids and aneuploids along with triploids (X. M. Guo, Cooper, Hershberger, & Chew, ; Yang & Guo, ; Yang, Que, He, & Zhang, ). Although TR should theoretically rise with increased salinity and treatment duration because of developmental asynchrony, it also resulted in decreased hatching and survival ratios in our study.…”

“…The triploid larvae were obtained using the optimal aforementioned induction parameters and cultured to the spat stage in 20,000‐L tanks. The larvae were fed with fresh Isochrysis galbana , as well as N. closterium and Platymonas subcordiformis, once the shell length reached 160 μm (Meng et al, ; Yang & Guo, ; Y. H. Zhang et al, ), and the quantity of algae was gradually increased from 2,000 to 80,000 cells/mL daily as the larvae grew (G. F. Zhang & Yan, ). The larval density was maintained at 5–6 larvae/mL at the D‐larval stage (Huo et al, ), and the swimming larvae were cultured at 15 ± 0.5°C with 2/3 water changes daily.…”