Ingestion and excretion dynamics of microplastics by black soldier fly larvae and correlation with mouth opening size

Abstract

Black soldier fly (BSF) larvae (Hermetia illucens) are voracious feeders that can be reared on food waste streams originating from the food industry and retailers. Because these food waste streams are automatically being unpacked in substantial amounts, they can contain microplastics, potentially jeopardising the larvae’s chemical safety when applied as compound feed ingredients. During this study, the dynamics of ingestion and excretion of microplastics by BSF larvae reared on substrates containing different contents (wMP = 0.00, 0.01, 0.10, 0.50, 1.00, 3.00%) of fluorescent blue-labelled microplastics (median size, Dv(50) = 61.5 µm) were monitored. To correlate the particle size with their uptake, larval mouth opening dimensions were measured during the rearing process. In conclusion, it appeared that ingestion of microplastics by BSF larvae depends on initial particle load, mouth size, and consequently also age. The larvae took up between 131 (wMP = 0.01%) and 4866 (wMP = 3.00%) particles leading to bioaccumulation factors (BAF) between 0.12 (wMP = 3.00%) and 1.07 (wMP = 0.01%). Larvae also appeared to excrete the microplastics, lowering the BAFs to values between 0.01 (wMP = 3.00%) and 0.54 (wMP = 0.01%).

A comparative study of effects of biodegradable and non-biodegradable microplastics on the growth and development of black soldier fly larvae (Hermetia illucens).

“…However, when comparing the T1 and T2 larval gut, no MP accumulation over time is detectable. This is also in line with the study of [23], who showed that BSFL ingest and defecate MPs together with the feeding substrate. Unfortunately, the guts of BSFL at T3 were too fragile and the extraction of an entire gut and its content was not feasible.…”

“…The average mortality was lowest for PA (9.4% ± 6.3) and highest for PLA (14.9% ± 3.7). Other studies showed similar results, where the Control was compared to MP treatment [13,21,23]. With 33% ± 4.3 and 32% ± 4.4 average pupation rates and 7 ± 1.7 and 7 ± 1.7 days until the rst pupation, respectively, PLA and PA treatments showed similar performance.…”

“…5j-k), which would mitigate the risk of introducing MPs into the feed chain via products derived from BSFL biomass. In addition, a starvation period before harvesting could be a possible solution to remove MPs from the larval guts [23]. However, the potential bioaccumulation of undesirable substances in the prepupal stage, such as MPs and heavy metals and other toxic compounds, should be monitored more closely [21,30].…”

“…However, the potential bioaccumulation of undesirable substances in the prepupal stage, such as MPs and heavy metals and other toxic compounds, should be monitored more closely [21,30]. So far, BSFL were not found to be able to degrade the MPs [21,23]. Moreover, the role of the BSFL gut microbiome in processing ingested MPs has yet to be explored, while earlier ndings have suggested that changes in the gut microbiome's composition have no impact on its functional capacities, alongside the maintenance of a stable core microbiome [31,32].…”

Frass fertilizers from mass-reared insects: species variation, heat treatment effects, and implications for soil application

“…Organic wastes suitable as rearing substrate are prone to be contaminated with microplastics. While first studies suggest that the development of farmed insects is not significantly affected by microplastics, these particles are excreted in their original form after passing through the larvae’s digestive tract and accumulate in the frass (Heussler et al, 2023; Lievens et al, 2023). Temperatures exceeding 60 °C have been shown to melt or clump specific microplastics, and temperatures nearing 100 °C might even lead to their elimination (Munno et al, 2018).…”