Neurotoxicity in Marine Invertebrates: An Update

Abstract

Invertebrates represent about 95% of existing species, and most of them belong to aquatic ecosystems. Marine invertebrates are found at intermediate levels of the food chain and, therefore, they play a central role in the biodiversity of ecosystems. Furthermore, these organisms have a short life cycle, easy laboratory manipulation, and high sensitivity to marine pollution and, therefore, they are considered to be optimal bioindicators for assessing detrimental chemical agents that are related to the marine environment and with potential toxicity to human health, including neurotoxicity. In general, albeit simple, the nervous system of marine invertebrates is composed of neuronal and glial cells, and it exhibits biochemical and functional similarities with the vertebrate nervous system, including humans. In recent decades, new genetic and transcriptomic technologies have made the identification of many neural genes and transcription factors homologous to those in humans possible. Neuroinflammation, oxidative stress, and altered levels of neurotransmitters are some of the aspects of neurotoxic effects that can also occur in marine invertebrate organisms. The purpose of this review is to provide an overview of major marine pollutants, such as heavy metals, pesticides, and micro and nano-plastics, with a focus on their neurotoxic effects in marine invertebrate organisms. This review could be a stimulus to bio-research towards the use of invertebrate model systems other than traditional, ethically questionable, time-consuming, and highly expensive mammalian models.

Acute Cd Toxicity, Metal Accumulation, and Ion Loss in Southern Catfish (Silurus meridionalis Chen)

“…Fish have high affinity to Cd. Metals are not degradable but rather accumulate in the environment, and due to the biomagnification effect, they move up the food chain, progressively increasing their concentrations in the tissues of fish [ 7 ]. This can be a public health concern.…”

“…Anthropogenically derived impacts have unequivocally contributed to environmental poisoning by metals in aquatic ecosystems during the last few decades [ 1 ]. Among these heavy metals, cadmium (Cd) is of particular concern because of its widespread distribution in the aquatic environment [ 2 , 3 ], and because it is highly toxic to both fish and invertebrate marine organisms [ 4 , 5 , 6 , 7 ]. Heavy metals have a bioaccumulative nature.…”

“…Bioaccumulation means the accumulation over time of a substance, especially a contaminant (such as a heavy metal), in a living organism [ 8 ]. Cd tends to accumulate in fish and invertebrate marine organisms [ 7 ]; as fish and invertebrate marine organisms represent the main contaminated foods that are consumed by humans, Cd is indirectly becoming toxic to human beings [ 7 ]. In China, the Cd concentration in normal fresh water ranges from 10 ng/L to 8 μg/L [ 9 ]; Cd and Cd concentrations in polluted water range from 0.8 to 12.05 mg/L [ 9 , 10 ].…”

Study of Heavy Metals Pollution and Vitellogenin Levels in Brown Trout (Salmo trutta trutta) Wild Fish Populations

“…Among the essential metals, Co and Ni were present in all of the trout samples, but at very low concentrations. Both metals are considered essential trace elements for animals, but exposure to excess levels of Ni and Co may result in adverse effects, causing neurotoxicity, hepatotoxicity, nephrotoxicity, gene toxicity, reproductive toxicity, and increased risk of cancer [39,40].…”

Potential Effects of Persistent Organic Contaminants on Marine Biota: A Review on Recent Research

“…The wide variety of effects observed in non-target species exposed to pesticides include detrimental impacts to biota with photosynthetic symbionts (e.g., marine microalgae Rhodomonas salina [178], diatoms Phaeodactylum tricornutum [179] and Chaetoceros muelleri [180], tropical marine cnidarian, sea anemones Exaiptasia pallida and symbiotic zooxanthellae microalga Symbiodinium spp. [181], Cassiopea maremetens medusae [182]), but also disruptions to non-photosynthetic animals such as reduced growth and reproduction rates of invertebrates (e.g., sea urchin Paracentrotus lividus [183]) and vertebrates (Pacific oyster Crassostrea gigas [184] and Sheepshead minnow Cyprinodon variegatus [185]), disruptions of nerve impulses which can ultimately lead to paralysis and death of invertebrates, and several sub-lethal effects on physiological or metabolic endpoints that are usually measured during the exposure treatments and provide unambiguous information about responses to pesticide exposure [175,186,187].…”