Divergent Egg Physiologies in Two Closely Related Grasshopper Species:Taeniopoda equesversus Romalea microptera (Orthoptera: Romaleidae)

Abstract

We compared egg survivorship and egg development time at different soil moistures for two closely related grasshopper species from divergent habitats: marsh-inhabiting Romalea microptera (Beauvois) versus desert-inhabiting Taeniopoda eques (Burmeister). These two species can interbreed and produce viable offspring. In nature, both species have a similar 8–9 mo subterranean egg stage, but their soil environments differ dramatically in water content. We predicted that the eggs of the two species would exhibit differential survivorship and development times under different moisture levels. Our laboratory results show that the eggs of both species survived a wide range of soil moistures (≈ 0.5 to 90%), maintained for 3 mo. However, the eggs of the marsh grasshopper, R. microptera, better tolerated the highest soil moistures (95 and 100%), whereas the eggs of the desert species, T. eques, better tolerated the lowest soil moistures (0.0 and 0.1%). Sixty-five percent of marsh-inhabiting R. microptera eggs, but no desert T. eques eggs, survived 3 mo submersion under water. In contrast, 49% of desert T. eques eggs, but only 3.5% of R. microptera eggs, survived after being laid into oven-dried sand and then maintained with no additional water until hatch. In the laboratory at 26°C, the two species differed significantly in the mean length of the oviposition-to-hatch interval: 176 d for R. microptera versus 237 d for T. eques. These divergent traits presumably benefit these insects in their divergent habitats. Our results suggest the evolution of physiological divergence that is consistent with adaptations to local environments.

Daily Temperature Cycle Induces Daily Hatching Rhythm in Eastern Lubber Grasshoppers,Romalea microptera

“…Egg cups were sealed with a tight-fitting lid and stored on open shelves in the laboratory at 26 ± 1.5 o C; we periodically opened and added small amounts of tap water to the cups to maintain the sand at approximately 7% moisture level. In the laboratory, pods begin to hatch 4.5 to 6.5 months after laying, and individual pods may continue hatching for 1 to 3 weeks (Stauffer et al 2011). Individual eggs can be as deep as 9 cm under the ground, and this depth causes some vermiform (fresh-hatched) nymphs to die before reaching the surface.…”

Effects of Soil Temperature and Moisture on the Development and Survival of Grasshopper Eggs in Inner Mongolian Grasslands

“…The response of the egg hatching rate to soil moisture clearly differed from that of egg hatching time and egg water content in the three grasshopper species. The distinct responses of grasshopper eggs reflect species-specific ecological traits associated with their phenology and habitat use (Stauffer et al, 2011).…”

Surviving a flood: effects of inundation period, temperature and embryonic development stage in locust eggs

“…However, a two-stage temperature regime was not used and the development stage of the eggs at inundation was not reported. Most strikingly, Stauffer et al ( 2011 ) reported that 64% of eggs of the grasshopper, Romalea microptera , survived 90 days of submersion in sand at a relatively high 24–28°C. However, this species has a very different life history compared with C. terminifera (e.g., longer development times, larger size) and inhabits salt marsh that is subject to seasonal flooding for extended periods that would be exceedingly rare in C. terminifera oviposition habitat.…”