A Pest or Otherwise? Encounter of Oryctes rhinoceros (Coleoptera: Scarabaeidae) with Persistent Organic Pollutants

SIMPLE SUMMARY: A native, widely spread beetle, Oryctes rhinoceros, in Southeast Asia may clean up some of the persistent organic pollutants (POPs) for us if guarded in a controlled manner. Some xenobiotics persisting in our environment may cause harmful effects to the living creatures within their food web via a so-called “bioaccumulation effect”. The encounter of wild creatures with the POPs appears inevitable. Luckily, this study revealed that the proper breeding of the commonly seen beetle could degrade more than 95% of some studied POPs simply by ingestion. The beetle larvae tolerated different POPs at various extents, yet through an acclimation operation, the beetle’s mortality rate could be greatly reduced. Even though O. rhinoceros is considered a pest for some valuable corps, its removal of POPs in a natural, efficient and passive (i.e., fewer energy inputs) manner makes this alternative promising and deserving of further explorations. ABSTRACT: The potential use of invertebrates as bioreactors to treat environmental pollutants is promising and of great interest. Three types of the persistent organic pollutants (POPs), namely pentachlorophenol (PCP), PAHs (naphthalene and phenanthrene) and dieldrin (DLN), were spiked in soil and treated by using Oryctes rhinoceros larvae, a known pest of coconut trees in southeast Asia, and also the indicators of POP toxicity and the fate and degradability of the ingested POPs were assessed. The larvae were tested at various levels of the POPs and went through an acclimation process. Without acclimation, the tolerance limits of the larvae toward PCP, PAHs and DLN were 200, 100 and 0.1 mg/kg-soil, respectively, yet with acclimation, the tolerance levels increased to 800, 400 and 0.5 mg/kg-soil, respectively. Biodegradation rates of all the tested POPs were >90% by week 2, with <5% and nearly 0% remaining in the feces and body of the larvae, respectively. The results suggest that the use of the beetle larvae in soil POP decontamination is doable.