Life history trait analysis of the entomopathogenic nematode Steinernema riobrave

Abstract

Life history traits (LHT) of Steinernema riobrave strain Sr 7-12 and Sr HYB19 were assessed at 25°C in monoxenic culture using a hanging drop technique. The LHT were studied with 5 × 109, 10 × 109 and 20 × 109 cells ml−1 of Xenorhabdus cabanillasii in semi-solid Nematode Growth Gelrite. Increased X. cabanillasii densities had a significant positive influence on offspring production on both Sr 7-12 and the hybrid Sr HYB19. At the higher bacterial food density, the total fertility rate (TFR) per female of Sr 7-12 was 2022 offspring and the net reproductive rate () reached 1904 offspring. Similarly, for Sr HYB19, the TFR per female was 2434 and was 1903. The percentage offspring produced via intra-uterine development (endotokia matricida) was relatively higher at 5 × 109 bacterial cells ml−1 than at higher bacterial density, with 64% and 66% of the total offspring produced by Sr 7-12 and Sr HYB19, respectively. A positive correlation () was recorded for offspring production and bacterial food density and for female body volume with bacterial density (). Female nematodes survived longer at higher bacterial food density; however, females of both strains could not survive longer than 7.8 days, beginning from hatching and always ending 1 day after initiation of endotokia matricida. Based on LHT results, there is a potential to maximise yield of dauer juveniles in liquid culture through increasing bacterial food density.