Eff ect of polystyrene microplastics and temperature on growth,intestinal histology and immune responses of brine shrimp Artemia franciscana

Microplastics pollution and seawater temperature rise have been the major environmental issues,threatening the survival and biodiversity of marine organisms.This study evaluated the combined effect of temperature and polystyrene microplastics(MP)on Artemia,a filter-feeding crustacean that is widely used for environmental toxicology studies.Brine shrimp Artemia franciscana were exposed to three MP concentrations(0,0.2,and 2.0 mg/L)and three temperatures(22,26,and 30℃)for 14 d.In general,higher MP concentration and temperature led to a decreased survival rate and growth.Two-way ANOVA analysis indicated that the survival rate of Artemia was significantly impacted by both MP concentration and temperature(P<0.05),but there was no significant interaction between two factors(P>0.05).Growth of Artemia was significantly impacted by temperature(P<0.05),and with a significant interaction between two factors(P<0.05).Furthermore,the enzymatic activity,intestinal histological analyses,and immune gene expression were determined for Artemia reared at 30℃ with three MP concentrations(0,0.2,and 2.0 mg/L).The results showed that 2.0-mg/L MP resulted in reduced Artemia intestinal microvilli and exfoliated epithelia cells,significantly increased acid phosphatase(ACP)activity(P<0.05)and immunerelated gene ADRA1 B and CREB3 expression,revealing that higher MP concentration could induce oxidative and immunological stress on Artemia at 30℃.Overall,our study suggests that MP and temperature have combined adverse effect on Artemia,especially at relatively high temperature and polystyrene MP concentration.These findings are important to understand the potential ecological risks posed by these two factors on the organisms in marine environment.

Diversity and connectedness of brine shrimp viruses in global hypersaline ecosystems

Brine shrimp(Artemia)has existed on Earth for 400 million years and has major ecological importance in hypersaline ecosystems.As a crucial live food in aquaculture,brine shrimp cysts have become one of the most important aquatic products traded worldwide.However,our understanding of the biodiversity,prevalence and global connectedness of viruses in brine shrimp is still very limited.A total of 143 batches of brine shrimp(belonging to seven species)cysts were collected from six continents including 21 countries and more than 100 geographic locations worldwide during 1977–2019.In total,55 novel RNA viruses were identified,which could be assigned to 18 different viral families and related clades.Eleven viruses were dsRNA viruses,16 were+ssRNA viruses,and 28 were−ssRNA viruses.Phylogenetic analyses of the RNA-directed RNA polymerase(RdRp)showed that brine shrimp viruses were often grouped with viruses isolated from other invertebrates and fungi.Remarkably,most brine shrimp viruses were related to those from different hosts that might feed on brine shrimp or share the same ecological niche.A notable case was the novel brine shrimp noda-like virus 3,which shared 79.25%(RdRp)and 63.88%(capsid proteins)amino acid identity with covert mortality nodavirus(CMNV)that may cause losses in aquaculture.In addition,both virome composition and phylogenetic analyses revealed global connectedness in certain brine shrimp viruses,particularly among Asia and Northern America.This highlights the incredible species diversity of viruses in these ancient species and provides essential data for the prevalence of RNA viruses in the global aquaculture industry.More broadly,these findings provide novel insights into the previously unrecognized RNA virosphere in hypersaline ecosystems worldwide and demonstrate that human activity might have driven the global connectedness of brine shrimp viruses.