Effect of larval thermal conditions on limb regeneration in a ladybird beetle, Cheilomenes sexmaculata

Abstract

In view of global environmental change, ecological factors especially temperature, affect development of the poikilotherms like insects. Since ladybirds are at risk of injury under mass‐rearing conditions, their ability to regenerate injured limbs is highly crucial for their survival. Therefore, the effect of limb regeneration in relation to temperature forms the basis of the present study. The immature stages of insects, being more vulnerable to the surrounding temperature, were considered to study the effect of the prior thermal experience of larvae on regeneration. We exposed the early larval stages of the ladybird beetle, Cheilomenes sexmaculata, to different temperature conditions pre‐ and postamputation. Exposure of immature stages to extreme temperatures did not affect the ability to regenerate and regeneration occurred at given temperature conditions. However, the regenerated legs were smaller in size across given temperatures as compared to unamputated legs. Body weights in amputated treatments showed no difference and remained unchanged across temperatures when compared to unamputated treatments. Postamputation developmental duration, equivalent to recovery time postlimb amputation, was found to be affected by larval thermal conditions. Recovery was faster in larval treatments exposed to higher temperatures. Thus, larval thermal conditions though did not affect the ability to regenerate lost limbs directly, it does modulate the time taken to regenerate.

Limb regeneration is blastema dependent in a ladybird beetle,Cheilomenes sexmaculata(Fabricius)

“…Interestingly, the pupal duration in scraped treatment was similar to control. This difference from previous studies where maximum delay was reported in the pupal stage (Wang et al, 2015;Saxena et al, 2016;Michaud et al, 2020;Rai et al, 2023), can be attributed to the absence of blastemal cells for the initiation of regeneration and hence no regeneration occurred in pupa. While delay in the developmental duration of the fourth larval stage of the amputated treatment demonstrated the attempt to form the blastema via cellular proliferation, with no blastema in the larvae entering pupation there was no initiation of regeneration.…”

The extent of regeneration is impacted by the stage of amputation in ladybird beetles: A case study in Cheilomenes sexmaculata

“…However, the latter three instars showed an extension in their PD, which was not visible for first instar. Thus, regenerated adults exhibited an increase in their PADD either by extending their development duration at the stage of amputation or by extending their PD, eventually delaying their TDP (Dewes, 1973;Kunkel, 1977;Rai et al, 2023;Wang et al, 2015;. This might be ascribed to a stress response of the entire animal due to the trauma of amputation.…”

“…Previous studies on limb regeneration in ladybird beetles (Abdelwahab et al, 2018;Michaud, Nedved, et al, 2020;Wang et al, 2015;Wu, Ma, et al, 2019;Yang et al, 2016) have reported a few developmental and reproductive costs. Till now, regeneration studies on C. sexmaculata have reported the influence of limb regeneration on the adult reproductive fitness (Saxena et al, 2016) and the effect of thermal conditioning during limb regeneration (Rai et al, 2023). The comparative study by Michaud, Nedved, et al (2020) reported that broad geographic distribution, guild dominance, polyphagy and interspecific competitiveness are some characteristics of this species with high levels of regeneration.…”

“…However, they did not look into the effect of limb regeneration on the morphometry of other appendages. Regeneration experiments using Cheilomenes sexmaculata (Fabricius) (Coleoptera: Coccinellidae) have found that an appendage lost during the larval stage gets regenerated in the adult (Saxena et al, 2016), but the regenerated legs were found to be smaller in comparison to the unamputated legs (Rai et al, 2023). It is still unclear, nevertheless, whether the extent of these expenditures diminishes or rises with the developmental stages at which the injury occurred.…”