Bioconcentration, Metabolism, and Spatial Distribution of¹⁴C‐Labeled Laurate in the Freshwater AmphipodHyalella azteca

Abstract

Regulatory assessment of the bioaccumulation from water is commonly based on bioconcentration factors (BCFs) derived from fish flow-through tests. Such experiments require many laboratory animals and are time-consuming and costly. An alternative test setup for organic, neutral compounds using the amphipod Hyalella azteca was recently suggested, resulting in BCF values which show a strong correlation with fish BCF data. In the present study, the bioconcentration potential of the ionic compound laurate was elucidated in H. azteca. The sodium salt of 1-14 C laurate was applied to H. azteca in a flow-through and a semistatic approach. Because of rapid biodegradation, a semistatic approach with frequent medium replacements was required to ensure a stable medium concentration. Laurate was also rapidly metabolized by H. azteca. A large proportion of the total radioactivity measured in the amphipod tissue was not extractable, suggesting that mineralized laurate was accumulated in the calcified exoskeleton of H. azteca. This was confirmed in a further study using carbonate [ 14 C]. A lipid-normalized (5.0%) Hyalella BCF of 8.9 was calculated for laurate, measured as free fatty acids. The results of the bioconcentration studies with H. azteca confirm the low bioaccumulation potential of the test item previously observed in fish. However, more organic ionic compounds with various properties need to be tested to assess whether a general correlation between fish and Hyalella BCF data exists. Environ Toxicol Chem 2020;39:310-322. Chemicals 14 C-lauric acid (carbonyl carbon-labeled), dissolved in ethanol, was obtained from Hartmann Analytics (98.4% wileyonlinelibrary.com/ETC FIGURE 1: Experimental setup of the flow-through system (left) and the (semi-)static system (right). a = mixing chamber; b = aeration; c = steel grid; d = DECOTAB; e = stirrer (not during study III); f = spiked medium. Bioconcentration of laurate in the amphipod Hyalella azteca-Environmental Toxicology and Chemistry, 2020;39:310-322 311

Are Fragrance Encapsulates Taken Up by Aquatic and Terrestrial Invertebrate Species?

“…The amphipod H. azteca is an omnivorous grazer and an excellent model organism for bioaccumulation tests (Kosfeld et al, 2020; Othman & Pascoe, 2001; Raths et al, 2020; Schlechtriem et al, 2019). Because the fragrance encapsulates applied in the present study tend to sediment under aquatic conditions, the benthic organism is especially suitable for testing the uptake of the test item under realistic exposure conditions.…”

“…The use of radiolabelled materials may solve this problem by allowing a more precise quantitative analysis after combustion analysis of spiked soil and samples. This may further allow a localization of the ingested material within the test organisms by the method of autoradiography as described by Raths et al (2020) for 14 C-laurate in H.azteca (Raths et al, 2020). This article is protected by copyright.…”

Ingestion of bivalve droppings by benthic invertebrates may lead to the transfer of nanomaterials in the aquatic food chain

“…The ingestion of the MNMs by the amphipods and potential chronic effects of the MNMs present in the F/pF were investigated. H. azteca has previously been used in a wide range of bioavailability and bioaccumulation tests using neutral and ionic organic compounds, metals and nanomaterials [59][60][61][62][63][64][65][66][67] and has recently been proposed as a test organism for the regulatory bioaccumulation assessment of MNMs [68]. The results of this study help to further elucidate the role of filter feeding bivalves and their F/pF in the transfer of MNMs along the aquatic food chain.…”

Moving Toward Standardized Toxicity Testing Procedures with Particulates by Dietary Exposure of Gammarids

“…Although not specifically tested in the present study, it is likely that supplemented DECOTABs can also be used to feed organisms other than G. roeseli (Kampfraath et al 2012). Decomposition and consumption tablets with and without supplements were already successfully used to feed other amphipods, like Gammarus fossarum (Straub et al 2017) or in experiments with Hyalella azteca (Raths et al 2020) and microbes (Hunting et al 2017); but standardization of production and homogeneous distribution of the particles and tabs as a sufficient nutrient supply were not extensively tested. Also, mixtures containing similar ingredients and supplements were successfully used to provide food for the caddisfly Allogamus mortoni (Fenoy et al 2020).…”

“…Decomposition and consumption tablets (DECOTABs; Kampfraath et al 2012) can meet these prerequisites and have been successfully used as a food source in aquatic toxicity tests (Straub et al 2017; Raths et al 2020). It was recommended by the authors, and applied by several studies, that DECOTABs can be amended by adding food supplements for specific applications or loading them with chemicals during production (Kampfraath et al 2012).…”