Association of pre-hatch temperature with body size traits of emergent Meloidogyne hapla second-stage juveniles

Previous research strongly associates the body size of poikilotherms with variations in environmental temperature. To investigate this relationship in Meloidogyne hapla, eggs were incubated at 5, 10, 20 (control), 30, 35, and 40°C for durations of 1, 2, 8, or 24 h (10 eggs per Petri dish × 3 dishes, n = 30 eggs per treatment). Following treatment, eggs were maintained at 20°C until hatching into second-stage juveniles (J2), at which point body size traits including body length, width, and mass were evaluated. The findings demonstrate that both incubation temperature and duration are strongly linked to those body size traits of emergent J2. Notably, an incubation temperature of 40°C was consistently associated with a complete absence of embryogenesis across all durations. The most pronounced size reductions occurred at 35°C, corresponding to the minimum J2 dimensions recorded, where length, width, and mass were lower by 5,5%, 11,5%, and 25.4% relative to the control, respectively. Conversely, maximum body length aligned with the 30°C treatment (a 0.85% increase over the control), whereas peak values for width and mass coincided with the 20°C control temperature. These data indicate that while successful egg development aligns with the 20 to 30°C thermal range, morphometric trends vary by specific trait (length vs mass/width), a pattern that corresponds with established literature on the developmental range of M. hapla eggs.