Chemicals sorbed to environmental microplastics are toxic to early life stages of aquatic organisms.

Microplastics are ubiquitous in aquatic ecosystems, but little information is currently available on the dangers and risks to living organisms. In order to assess the ecotoxicity of environmental microplastics (MPs), samples were collected from the beaches of two islands in the Guadeloupe archipelago, Petit-Bourg (PB) located on the main island of Guadeloupe and Marie-Galante (MG) on the second island of the archipelago. These samples have a similar polymer composition with mainly polyethylene (PE) and polypropylene (PP). However, these two samples are very dissimilar with regard to their contamination profile and their toxicity. MPs from MG contain more lead, cadmium and organochlorine compounds while those from PB have higher levels of copper, zinc and hydrocarbons. The leachates of these two samples of MPs induced sublethal effects on the growth of sea urchins and on the pulsation frequency of jellyfish ephyrae but not on the development of zebrafish embryos. The toxic effects are much more marked for samples from the PB site than those from the MG site. This work demonstrates that MPs can contain high levels of potentially bioavailable toxic substances that may represent a significant ecotoxicological risk, particularly for the early life stages of aquatic animals.

Polyps of the Jellyfish Aurelia aurita Are Unaffected by Chronic Exposure to a Combination of Pesticides.

Pesticides are a major contaminant in coastal waters and can cause adverse effects in marine invertebrates such as jellyfish. Most studies have investigated short-term responses of organisms to unrealistically high concentrations of pesticides; however, chronic exposure to persistent low concentrations, which are more likely to occur in the environment, are rarely analyzed. We tested the response of polyps of the moon jellyfish Aurelia aurita to environmental concentrations of the herbicide atrazine and the insecticide chlorpyrifos, individually and in combination, over 9 wk. We hypothesized that exposure to individual pesticides would reduce rates of asexual reproduction and alter polyps' metabolite profiles, and that the results would be more severe when polyps were exposed to the combined pesticides. Polyps survived and reproduced (through budding) in all treatments, and no differences among treatments were observed. Proton nuclear magnetic resonance spectroscopy revealed no difference in profiles of polar metabolites of polyps exposed to the individual or combined pesticides. Our results suggest that A. aurita polyps are unaffected by chronic exposure to atrazine and chlorpyrifos at concentrations recommended as being protective by current Australian water quality guidelines. Environ Toxicol Chem 2020;39:1685-1692. © 2020 SETAC.

An investigation on the impact of substrate type, temperature, and iodine on moon jellyfish production.

Jellyfish are a popular public aquarium species, however, their collection from natural populations is undesirable due to impact on species abundance and bycatch. Thus, a sustainable supply of jellyfish bred in-house would be highly desirable. Here we describe an investigation into developing a sustainable moon jellyfish, Aurelia aurita, breeding program by determining the impact of substrate type on reattachment of polyps and the influence of iodine and temperature on strobilation and ephyra production. To test whether reattachment and growth of moon jellyfish polyps are influenced by substrate type polyps were provided with anthropogenic and natural substrates after being dislodged in experimental aquaria. Polyps selectively re-attached to plastics rather than natural materials. However, polyp growth was similar on all tested substrates. We tested whether cooling and addition of iodine affected strobilation. A period of cooling of around 10 °C while also introducing soluble iodine to the polyps enhanced strobilation rate. This method produced ephyra at a reliable rate in captivity negating the need for collection of wild individuals providing a supply of individuals for exhibit and for conservation research within a public aquarium. These results demonstrate that plastics should be adopted as an easier to colonize substrate and the use of cooling with iodine addition can enhance sustainable breeding protocols of moon jellyfish and may be relevant to the production of comparable jellyfish species.

Effect of tea saponin on ephyrae and polyps of the moon jellyfish Aurelia sp.1.

The moon jellyfish (Aurelia sp.1) is thought to be a nuisance for the sea cucumber aquaculture, which commonly occur in the sea cucumber (Apostichopus japonicus) culture ponds of the Yellow Sea, China. To develop an appropriate method to control Aurelia sp.1 blooms, the toxic effects of tea saponin on Aurelia sp.1 ephyrae and polyps were tested in laboratory experiments. Our results revealed that tea saponin caused significant morphological changes, behavioral abnormality and mortality in Aurelia sp.1 ephyrae and polyps in 24 h and 48 h exposure experiments. The 24 h and 48 h median lethal concentrations (LC50) values of tea saponin for Aurelia sp.1 ephyrae were 1.9 and 1.1 mg L-1 respectively, while the LC50 value for Aurelia sp.1 polyps was 0.4 mg L-1 after 24h and 48 h of exposure to tea saponin. Comparison with literature results of tea saponin on A. japonicus indicates that the resistance of A. japonicus to tea saponin is 12-18 times greater than that of Aurelia sp.1 ephyrae. Therefore, the appropriate tea saponin dosage for the control of Aurelia sp.1 should be paid enough attention in order to minimize possible damage for sea cucumber. We suggest that the recommended level of tea saponin to eradicate Aurelia sp.1 ephyrae and polyps in sea cucumber culture ponds be lower than 1.35 mg L-1.

Multicellular redox regulation in an early-evolving animal treated with glutathione.

Redox signaling has emerged as a unifying theme in many seemingly disparate disciplines. Such signaling has been widely studied in bacteria and eukaryotic organelles and is often mediated by reactive oxygen species (ROS). In this context, reduced glutathione (GSH) acts as an important intracellular antioxidant, diminishing ROS and potentially affecting redox signaling. Complementing this cell-level perspective, colonial hydroids can be a useful model for understanding organism-level redox signaling. These simple, early-evolving animals consist of feeding polyps connected by tubelike stolons. Colonies treated exogenously with GSH or reduced glutathione ethyl ester (GEE) were expected to show a morphological change to sheetlike growth typical of low levels of ROS. Contrary to expectations, diminished stolon branching and polyp initiation was observed. Such runnerlike growth is associated with higher levels of ROS, and surprisingly, such higher levels were found in GSH- and GEE-treated colonies. Further investigations show that GSH triggered a feeding response in hydroid polyps, increasing oxygen uptake but at the same time relaxing mitochondrion-rich contractile regions at the base of polyps. Diminished gastrovascular flow and increased emissions of mitochondrial ROS also correlated with the observed runnerlike growth. In contrast to cell-level, "bottom-up" views of redox signaling, here the phenotype may arise from a "top-down" interaction of mitochondrion-rich regions and organism-level physiology. Such multicellular redox regulation may commonly occur in other animals as well.

Checkpoints in the life-cycle of Cassiopea spp.: control of metagenesis and metamorphosis in a tropical jellyfish.

Experimental data reveal that most, if not all, major events in the metagenetic life-cycle of Cassiopea spp. at these checkpoints depend on the interaction with specific biotic and physical cues. For medusa formation within a permissive temperature range by monodisk strobilation of the polyp, the presence of endosymbiotic dinoflagellates is indispensable. The priming effect of the algal symbionts is not primarily coupled with photosynthetic activity, but was found to be enhanced in the light. Budding of larva-like propagules by the polyp, however, is independent from such zooxanthellae. On the other hand the budding rate is influenced by various rearing conditions. Exogenous chemical cues control settlement and metamorphosis into scyphopolyps of both sexually produced planula larvae and asexual propagules. In laboratory experiments two classes of metamorphosis inducing compounds have been detected: a family of oligopeptides, featuring a proline-residue next to the carboxyterminal amino acid, and several phorbol esters. Using the peptide 14C-DNS-GPGGPA, induction of metamorphosis has been shown to be receptor-mediated. Furthermore, activation of protein kinase C, a key enzyme within the inositolphospholipid-signalling pathway appears to be involved in initiating metamorphosis. In mangrove habitats of Cassiopea spp. planula larvae specifically settle and metamorphose on submerged, deteriorating mangrove leaves from which biologically active fractions have been isolated. The chemical characterisation and comparison of these compounds from the natural environment with the properties and mode of action of oligopeptide inducers is in progress.

Statolith formation in Cnidaria: effects of cadmium on Aurelia statoliths.

Statolith formation in Cnidaria was reviewed with an emphasis on Aurelia statoliths. The review provides information on the chemical composition, mechanisms of initiation of mineralization, and effects of environmental factors on Cnidarian statolith formation. Environmental factors discussed included modified sea water ingredients, X-irradiation, clinostat rotation, and petroleum oil ingredients. A detailed account of the effects of cadmium on mineralization and demineralization of Aurelia statoliths is given. Cadmium at dosages of 2 to 4 micromoles significantly reduces statolith numbers in developing ephyrae. At a dosage of 3 micromoles, cadmium accelerates statolith loss in unfed ephyrae studied at 4 and 8 days following ephyrae release from strobilae. Cadmium, therefore, is shown to reduce statolith numbers in developing ephyrae and to cause greater reduction of statolith numbers in unfed ephyrae after 4 and 8 days than occurred in controls. Supplementation of Cd(2+)-containing artificial sea water (ASW) with calcium (3X and 5X ASW calcium content) results in higher numbers of statoliths at day 4 as compared with cadmium-treated ephyrae. At 8 days only the 5X calcium supplemented ASW is effective in enhancing statolith numbers in Cd(2+)-treated ephyrae. These results suggest that cadmium competes in some manner with calcium at the mineralizing sites of Aurelia.