Ingested microplastics impair the metabolic relationship between the giant clam Tridacna crocea and its symbionts

Zhi Zhou; Xingzhen Ni; Shiquan Chen; Zhongjie Wu; Jia Tang; Yilu Su; Xingjuan Wang; Lingui Wang

doi:10.1016/j.aquatox.2022.106075

Ingested microplastics impair the metabolic relationship between the giant clam Tridacna crocea and its symbionts

Aquat Toxicol. 2022 Feb:243:106075. doi: 10.1016/j.aquatox.2022.106075. Epub 2022 Jan 10.

Authors

Zhi Zhou¹, Xingzhen Ni², Shiquan Chen³, Zhongjie Wu³, Jia Tang², Yilu Su², Xingjuan Wang², Lingui Wang⁴

Affiliations

¹ State Key Laboratory of Marine Resource Utilization in South China Sea, Hainan Aquaculture Breeding Engineering Research Center, Hainan University, Haikou, Hainan, China; Key Laboratory of Tropical Hydrobiology and Biotechnology of Hainan Province, Hainan University, Haikou, Hainan, China. Electronic address: zhouzhi@hainanu.edu.cn.
² State Key Laboratory of Marine Resource Utilization in South China Sea, Hainan Aquaculture Breeding Engineering Research Center, Hainan University, Haikou, Hainan, China.
³ Hainan Academy of Ocean and Fisheries Sciences, Haikou, Hainan, China.
⁴ State Key Laboratory of Marine Resource Utilization in South China Sea, Hainan Aquaculture Breeding Engineering Research Center, Hainan University, Haikou, Hainan, China; Key Laboratory of Tropical Hydrobiology and Biotechnology of Hainan Province, Hainan University, Haikou, Hainan, China.

PMID: 35033793
DOI: 10.1016/j.aquatox.2022.106075

Abstract

Microplastics are emerging as widespread pollutants in coral reef ecosystems worldwide; however, there is limited knowledge regarding their impact on giant clams, which are important reef builders. In the present study, the cytological, physiological, and molecular response of the giant clam Tridacna crocea to a 5 d exposure of microplastics was investigated. The concentration of microplastics in the intestine and outer mantle increased significantly and gradually after the exposure to microplastics. There were no significant changes in the density of symbiotic Symbiodiniaceae throughout the exposure period, but symbiont chlorophyll content increased significantly after 1 d of exposure. There was a significant increase in symbiont superoxide dismutase (SOD) activity, but a decrease in giant clam SOD activity and symbiont glutathione S-transferase (GST) activity. No significant changes in catalase (CAT) activity and caspase3 activation level were observed in the two symbiotic partners. Transcriptomic analysis of the giant clam revealed 138 significantly upregulated and 1390 significantly downregulated genes after 5 d of microplastic exposure. The top 20 GO terms overrepresented by these significantly downregulated genes were related to primary metabolic processes and cellular metabolic processes. No significantly upregulated genes were observed in symbionts, but 28 genes were significantly downregulated, including chloroplast oxygen-evolving enhancer, photosystem I reaction center subunit II, peptide/nitrate transporter, sodium-coupled neutral amino acid transporter, beta-glucosidase, and TPA: lipase. These results suggest that T. crocea ingests microplastics through the outer mantle and intestine, and these microplastics can suppress the photosynthesis, organic nutrient transportation, and detoxification ability of the symbionts, as well as the primary metabolism of the giant clam. This eventually could threaten their metabolic relationship and long-term survival.

Keywords: Acclimation; Giant clam; Microplastic; Stress; Symbiosis.

MeSH terms

Animals
Bivalvia*
Ecosystem
Microplastics
Nitrate Transporters
Plastics
Water Pollutants, Chemical* / toxicity

Substances

Microplastics
Nitrate Transporters
Plastics
Water Pollutants, Chemical