Induced diploid gynogenesis and polyploidy in the ornamental (koi) carp Cyprinus carpio L.
The results of a series of experiments conducted in our laboratory on the ornamental common carp (koi), aimed at optimizing heat-shock chromosome-set manipulation procedures, are described. The timing of heat-shock initiation was expressed in the relative unit of embryological age (τ0) in order to standardize this parameter, the absolute time for heat-shock initiation being calculated from duration of one τ0 at two different pre-treatment water temperatures. Heat shocks were applied within the periods of 0.05–0.60 τ0 and 1.20–2.20 τ0 which, respectively, cover the successive phases of the 2nd meiotic division and the 1st cleavage. The highest production of diploid gynogenetic offspring was observed when heat shocks were initiated at 0.15–0.25 τ0 and at 1.5 τ0, after insemination, corresponding to anaphase of meiosis-II, and metaphase of the 1st cleavage, respectively. Similar results were obtained irrespective of the different pre-treatment water temperatures, thus confirming the possibility of standardizing heat-shock timing by τ0.
Diploid gynogenesis induced by heat shocks after activation with UV-irradiated sperm in common carp
Abstract Diploid gynogenetics of common carp (Cyprinus carpio L.) have been produced by heat shocks applied 3–5 min after insemination with sperm genetically inactivated by UV irradiation. The use of red female (visible recessive marker) confirmed the effectiveness of this irradiation. The minimal temperature inducing second polar body retention is approximately 38°C. The highest percentages of diploid viable fry were observed for water temperature shocks at 39, 39.5 and 40°C lasting 1 min 20 s to 2 min.
The risk of Listeria monocytogenes infection in beef cattle operations
Aim:  To determine the prevalence of Listeria monocytogenes and associated risk factors among beef operations (cow‐calf and feedlot) in central and southern California.