Unusual chromosome numbers and polyploidy in invasive fire ant populations

Fire ants (Solenopsis invicta Buren in J Ga Entomol Soc 7:1-26, 1972), an invasive alien ant species, first spread from South America to the United States in the 1930s, the southern part of the United States by the end of the twentieth century, Oceania, Taiwan, and China in the twenty-first century, and finally to Japan and South Korea in 2017. As these ants have significant negative economic, human health, and environmental impacts, the purpose of this research was to accumulate cytogenetic information regarding fire ants and provide basic data for developing management strategies for their control. Fire ants were collected from invasive populations from Taiwan, Florida (USA), and Buenos Aires (Argentina), and a native population from Puerto Iguazu (Argentina), their point of origination, and analyzed with regard to chromosome number, morphology, and polyploidy, silver-stained nucleolar organizer regions (Ag-NORs), and 18S rDNA and telomere fluorescence in situ hybridization (FISH). The results showed that (1) fire ants from invaded populations differed in chromosome morphology compared to those from native populations; (2) the Florida and Taiwanese fire ant populations evinced greater variability in chromosome numbers and polyploidy variations; (3) the Taiwanese population exhibited significantly increased Ag-NOR signals in interphase cells, with signal number significantly positively correlating with distance from native populations; and (4) substantial diversity of signals was also apparent following 18S rDNA and telomere FISH analyses. Variation in these characteristics were hypothesized to be due to (1) the effect of hybridizations and interbreeding between closely related species or genetically distant populations, and (2) the potential effect of large amounts of insecticides sprayed for pest control.

Parturition induction two days prior to term decreases birth weight and lactational growth, but not piglet maturity, health or post-weaning growth

Premature parturition induction may adversely affect postnatal health and performance. The objective of this study was to evaluate the impact of cloprostenol induction 2 d prior to term on piglet maturity (liver glycogen), postnatal productivity (birth weight, growth rate), and health (morbidity, mortality, passive antibody, fecal Clostridium perfringens). Two hundred and sixteen pregnant sows and their progeny (2827 piglets) were assigned to the study. Induction decreased gestation length 2.1 d (P < 0.0001), birth weight 107.2 g pig-1 (P = 0.0004), lactational growth 10.1 g d-1 (P = 0.05), and day 16 weight 0.30 kg pig-1 (P < 0.05). Liver glycogen concentration was 71.2 µg g-1 higher in the stillborns of induced sows (P = 0.03), suggesting the pre-term sows were catabolic. No group differences in post-weaning growth rate, pre-weaning mortality or morbidity, passive antibody transfer or fecal Clostridium perfringens level were found. Reduced lactational growth appeared attributable to the reductions in gestation length and birth weight, rather than in piglet maturity. In spite of reducing lactational growth and body weight at 16 d of age, the administration of cloprostenol 2 d prior to term, under the conditions of this study, resulted in no measureable long-term health or performance consequences. Key words: Porcine, parturition-induction, cloprostenol, prostaglandin F2α, glycogen, Clostridium perfringens