Consumption and degradation of different consumer plastics by mealworms (Tenebrio molitor): Effects of plastic type, time, and mealworm origin

Abstract

The larvae of the Tenebrionidae-family beetles, i.e., mealworms, have been identified as potential consumers of polystyrene (PS). This may have major implications for reduction of PS waste in the environment. However, there is a lack of information on the ability of mealworms to consume other types of plastics beyond PS and quantify their degradation rates. The purpose of this work is to systematically determine the ability of mealworms to consume other sources of commonly used commercial plastics [e.g., polypropylene (PP), polyvinyl chloride (PVC), high density polyethylene (HDPE), and low-density polyethylene (LDPE)] over various periods of time (e.g., 10-, 20-, and 30-days). Additionally, this work addresses the effects of specific plastic type on changes in mealworm mass and viability. Mealworms from three different commercial sources were used. All five plastics were discovered to be consumable by mealworms to various degrees. Overall, PS was consumed most, with average consumption rates of 7.02 (±0.66), 7.13 (±2.37), and 8.70 (±1.38) mg plastic consumed per 100 mealworms per day from three different sources. This was followed by PP, which had average consumption rates of 2.53 (±0.03), 4.55 (±2.97), and 3.21 (±1.39) mg plastic consumed per 100 mealworms per day. Overall, 9.11 mg PS were consumed by 100 mealworms per day, and 0.85 mg PS were consumed by 1 g mealworm per day. The other three plastics (PVC, HDPE, and LDPE) were the least favorable for mealworm consumption. Novel findings from this work indicate that mealworms lost mass during the first 10 days of the experimental time period, yet they still consumed plastics. Additionally, larger-sized mealworms displayed a lower viability rate. Overall, this work contributes new understanding for the capabilities of mealworms to degrade several common and environmentally problematic (i.e., recalcitrant) plastics. Additionally, it provides critical information, such as Specific Consumption Rates (SCRs), for several plastics that have not been previously reported.