Reproduction and chromosome inheritance in triploid Pacific oyster (Crassostrea gigas Thunberg) were studied in diploid female  triploid male (DT) and reciprocal (TD) crosses. Relative fecundity of triploid females was 13.4% of normal diploids. Cumulative survival from fertilized eggs to spat stage was 0.007% for DT crosses and 0.314% for TD crosses. Chromosome number analysis was conducted on surviving progeny from DT and TD crosses at 1 and 4 years of age. At Year 1, oysters from DT crosses consisted of 15% diploids (2n ¼ 20) and 85% aneuploids. In contrast, oysters from TD crosses consisted of 57.2% diploids, 30.9% triploids (3n ¼ 30) and only 11.9% aneuploids, suggesting that triploid females produced more euploid gametes and viable progeny than triploid males. Viable aneuploid chromosome numbers included 2n þ 1, 2n þ 2, 2n þ 3, 3nÀ2 and 3nÀ1. There was little change over time in the overall frequency of diploids, triploids and aneuploids. Among aneuploids, oysters with 2n þ 3 and 3nÀ2 chromosomes were observed at Year 1, but absent at Year 4. Triploid progeny were significantly larger than diploids by 79% in whole body weight and 98% in meat weight at 4 years of age. Aneuploids were significantly smaller than normal diploids. This study suggests that triploid Pacific oyster is not completely sterile and cannot offer complete containment of cultured populations.

When two heavy ions near the Fermi energy collide, a warm and low-density region can form in which fragments appear. This region is mainly dominated by proton (p) and alpha (α) particles. In such an environment, the αs interact with each other, and especially through strong resonances, form complex systems such as 8 Be and 12 C. Our experiments show that in the reactions 70(64) Zn( 64 Ni)+ 70(64) Zn( 64 Ni) at E/A=35 MeV/nucleon levels of 8 Be appear around relative energies E i j =0.092 MeV, 3.03 MeV as well as above 10 MeV and 100 MeV. For the 3α systems, multi resonance processes give rise to excited levels of 12 C. In particular, the Hoyle state at 7.654 MeV excitation energy shows a decay component through the ground state of 8 Be and also shows components where two different α couples are at relative energies consistent with the ground state of 8 Be at the same time. A component where the three α relative energies are consistent with the ground state of 8 Be (i.e., E 12 =E 13 =E 23 =0.092 MeV) is also observed at the 7.458 MeV excitation energy, which was suggested as an Efimov state.Several decades after the suggestion by Fred Hoyle [1] of a 0 + resonance near the 3α threshold to accelerate 12 C formation in stars, the Hoyle state (HS) is still a hot topic in nuclear structure [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. While its energy, i.e., 7.654 MeV, and width, 8.5 eV, are firmly established, there are debates on its decay. It is commonly accepted [5][6][7][8][9][10][11][12][13][14][15][16] that almost 100% of the HS decay is through the ground state of 8 Be ( 8 Be g.s. ), thus corresponding to a sequential decay (SD), i.e., first an α particle is emitted, and then 8 Be decays into 2αs with 0.092 MeV relative kinetic energy. Other decay modes, for example, the theoretically predicted direct decay (DD) of 12 C into 3αs of equal energy (DDE) or into a linear chain (LD) [4,5] have been studied in high precision/high statistical experiments [8][9][10][11][12][13][14][15][16] giving an upper limit of 0.043% [14], 0.036%[15] and 0.024%[15] for DD, DDE, and LD, respectively. While we are probably at the limit of the experimental sensitivity, higher statistical experiments might be performed, or different strategies might be explored. In this paper, we will discuss a completely new approach, i.e., we will generally explore the 12 C decays also in the presence of nearby nuclear matter. This is surely relevant since stellar processes, where 12 C (or larger nuclei) are formed, might occur inside a dense star or on its surface, thus occurring under different conditions of density and temperature. One way to simulate some stellar conditions is to collide two heavy ions at beam energies near the Fermi energy. In central/peripheral collisions of the two ions, first we have a gentle increase in the density slightly above the ground state density, ρ 0 =0.16 f m −3 [17,18] as revealed by microscopic calculations and experiments [19][20][21][22]. The system expands while cooling, and for densities below (1/3-1/...

No abstract