Arthropoda

3.1.4. Arthropoda

The aquatic group of arthropods includes Crustacea and Merostomata. Crustaceans, which comprise economically important species such as crabs, shrimps, lobsters, and barnacles, play vital roles in ecosystems. They are widely distributed from aquatic areas to brackish waters, estuaries, freshwaters, rivers, and terrestrial areas and are used as human food. However, their true significance lies in their role as food sources for many creatures such as fish, sharks, birds, and mammals. The larval stages of crustaceans, often found within zooplankton groups like Ostracoda, Isopoda, and Copepoda, are pelagic and constitute food for many creatures. Crustaceans exhibit diverse diets, including filter feeding, detritivory, carnivory, and omnivory.

The uptake of MPs and their effects have been studied in many groups of crustaceans, such as Decapoda , Stomatopoda, Cirripedia, Cladocera , and Amphipoda . This review examined the effects of MPs on arthropods based on the findings of 65 studies (Appendix Table 1 View Table 1 ).

The highest number of studies on MP concentrations in Crustaceans have been carried out in the GIT, including many studies of the gills, stomach, intestine, gut, hepatopancreas, digestive tracts, muscles, and soft tissues, with rare studies on the carapace and only one study on eggs (Appendix Table 1 View Table 1 ). The most frequently used method for digesting tissues was 10% KOH, followed by 30% hydrogen peroxide. µFTIR, followed by FTIR, was the most commonly used method for polymer analysis. MPs were mainly obtained as fibers, followed by fragments. PE, PET, and PP were the most commonly identified polymers. Most studies have been carried out on decapods and the blue crab Callinectes sapidus (Appendix Table 1 View Table 1 ).

The lowest MP rate was reported in the krill Euphasia , a zooplankton (0.019 MPs/individual) in the Bohai Sea, China (Zheng et al., 2020). The highest MP rate was reported as 327.56 MPs/individual in the mangrove crab Metopograpsus quadridentata in Jakarta Bay, Indonesia (Patria et al., 2020) . The size of M. quadridentata was large, and a positive correlation between the weight of the crabs and MP abundance was revealed. Additionally, there were no data indicating that contamination conditions were minimized in the study, so contamination may be another important reason for the high concentration of MPs.

Barnacles are sessile benthic filter-feeding organisms. In the Capo Milazzo Marine Protected Area, the pelagic barnacle Lepas (Lepas) anatifera was found to contain an average of 1.74 ± 0.80 MPs and natural fibers in its GIT, as reported by Scotti et al. (2023). This concentration is higher than that reported in two other studies on barnacles (Xu et al., 2020b; Zhang et al., 2022). MPs have been detected even in Antarctica , where human density is limited (Sfriso et al., 2020; Primpke et al., 2024). In the South Shetland Islands and the South Orkney Islands, MP concentrations in the Antarctic krill Euphausia superba have been studied. The average MP rate in Antarctic krill was found to be 0.29–0.33 MPs/individual, with sizes ranging from 20 to 195 µm (Zhu et al., 2023a). The primary polymers within the compositions of MPs found in Antarctic krill are PE, PP, and PS, which are also the main constituents of MPs in subsurface seawater surrounding the Antarctic Peninsula (Zhang et al., 2022). PE and PP are commonly used in household materials and have emerged as the predominant types of plastic polymers manufactured globally (Liao et al., 2021).

A total of four species of the class Merostomata have been found along the coasts of North and Central America and in the Indo-Pacific. Horseshoe crabs are prey for many birds, fish, and sea turtles. They also provide a habitat for many species of mollusks and crustaceans, leading to symbiotic relationships. In Asia, they are economically important due to their biomedical use. In a study conducted in the Beibu Gulf of China, which has the world’s highest horseshoe crab population, researchers investigated the contamination of juvenile three-spined horseshoe crab Tachypleus tridentatus by MPs. The average MP content in the GIT was found to be 21.1 ± 13.4 MPs per individual, which was significantly higher than the MP content in other mollusks and crustaceans in the same region of China. That study also revealed that 99% of the MPs were fibers, with cellophane being the most abundant polymer (Wang et al., 2022).