What Is the Impact of Microplastics and Lipid Regulators on Marine Meiofauna? Case Study of Polyvinyl Chloride, Atorvastatin, and Simvastatin

A microcosm experiment was carried out to provide a deeper insight into the toxic mechanisms exerted by two lipid regulator agents, as well as their interactions with the polyvinyl chloride microplastic on marine meiofauna. Two concentrations of Atorvastatin “A” and of Simvastatin “S”, (i.e., 0.6 mg.kg−1 and 6 mg.kg−1), as well as a single dosage of polyvinyl chloride microplastics “P” at 20 mg.kg−1, separately and their combined mixtures (“AP” and “SP”) were used on coastline dwelling marine meiofauna, with a main focus on nematodes. The results showed a significant reduction in meiofauna abundance in treatments compared to control. SIMPER analysis highlighted a significant decrease in the abundance of epigrowth feeders (2A), which possess conical (co) tails, and indistinct (id) amphideal foveas compared to control microcosms, reflected mainly in the decrease in abundance of the species Prochromadorella longicaudata. Furthermore, the contamination with microplastic affected only the omnivores-carnivores guild. Another finding of the current experiment is that the mixtures of microplastic with drugs lead to synergic interactions that increased their toxic effects on marine nematode communities.

Transcriptomic and proteomic analysis of marine nematode Litoditis marina acclimated to different salinities

Salinity is a critical abiotic factor for all living organisms. The ability to adapt to different salinity environments determines an organism′s survival and ecological niches. Litoditis marina is a euryhaline marine nematode widely distributed in coastal ecosystems all over the world, although numerous genes involved in its salinity response have been reported, the adaptive mechanisms underlying its euryhalinity remain unexplored. Here, we utilized worms which have been acclimated to either low salinity or high salinity conditions and evaluated their basal gene expression at both transcriptomic and proteomic levels. We found that several conserved regulators, including osmolytes biosynthesis genes, transthyretin-like family genes, V-type H+-transporting ATPase and potassium channel genes, were involved in both short-term salinity stress response and long-term acclimation processes. In addition, we identified genes related to cell volume regulation, such as actin regulatory genes, Rho family small GTPases and diverse ion transporters, might contribute to hyposaline acclimation, while the glycerol biosynthesis genes gpdh-1 and gpdh-2 accompanied hypersaline acclimation in L. marina. Furthermore, gpdh-2 might play an essential role in transgenerational inheritance of osmotic stress protection in L. marina as in its relative nematode Caenorhabditis elegans. Hereby, this study paves the way for further in-depth exploration on adaptive mechanisms underlying euryhalinity, and may also contribute to the studies of healthy ecosystems in the context of global climate change.

A new species of free-living marine nematode, Diplolaimella ariakensis n. sp. (Nematoda: Monhysteridae) from the Ariake Sea, Japan

Summary A new species of free-living marine nematode, Diplolaimella ariakensis n. sp., is described from a muddy tidal flat of the Ariake Sea, southern Japan. Diplolaimella ariakensis n. sp. differs from its congeners by the following: presence of ocelli, absence of denticles in the buccal cavity, a long tail (11-14 cloacal body diam., c = 3.2-4.0 in male, 17-21 anal body diam., c = 2.9-3.4 in female), spicules as long as 1.4-1.8 cloacal body diam., gubernaculum 0.4-0.5 cloacal body diam. long with a dorsocaudal apophysis 0.5-0.7 cloacal body diam. long, presence of a precloacal supplement, absence of postcloacal papillae, presence of seven pairs of body pores in male, and the anterior position of the vulva (V = 43-46). A dichotomous key to Diplolaimella species is provided. Almost full-length 18S rRNA and partial cytochrome c oxidase subunit I gene sequences were determined for D. ariakensis n. sp. A maximum likelihood tree of 18S sequences supported a close relationship between D. ariakensis n. sp. and D. dievengatensis.

One new species of free-living marine nematode from the Yellow Sea, China

A new species of Setostephanolaimus Tchesunov, 1994, S. longiseta sp. nov. was discovered in an intertidal sand beach along the Rizhao coast of the Yellow Sea. It is characterized by its long and slender body, long cephalic setae (longer than 20 µm and 16 µm in males and females, respectively) and subcephalic setae, long spicules (longer than 90 µm), gubernaculum with dorsal hooked apophyses, along with presence of 10–12 tubular precloacal supplements in males. Updated dichotomous key for species of the genus Setostephanolaimus is also given.

Genome-wide transcriptional responses of marine nematode Litoditis marina to hyposaline and hypersaline stresses

Maintenance of osmotic homeostasis is essential for all organisms, especially for marine animals in the ocean with 30‰ salinity or higher. However, the underlying molecular mechanisms that how marine animals adapt to high salinity environment compared to their terrestrial relatives, remain elusive. Here, we investigated marine animal’s genome-wide transcriptional responses to salinity stresses using an emerging marine nematode model Litoditis marina. We found that the transthyretin-like family genes were significantly increased in both hyposaline and hypersaline conditions, while multiple neurotransmitter receptor and ion transporter genes were down-regulated in both conditions, suggesting the existence of conserved strategies for response to stressful salinity environments in L. marina. Unsaturated fatty acids biosynthesis related genes, neuronal related tubulins and intraflagellar transport genes were specifically up-regulated in hyposaline treated worms, while exhibited the opposite regulation in hypersaline condition. By contrast, cuticle related collagen genes were enriched and up-regulated for hypersaline response, interestingly, the expression of these collagen genes was significantly decreased in hyposaline condition. Given a wide range of salinity tolerance of the marine nematodes, this study and further genetic analysis of key gene(s) of osmoregulation in L. marina will likely provide important insights into biological evolution and environmental adaptation mechanisms in nematodes and other invertebrate animals in general.

Free-living marine nematodes diversity at Ponta Delgada-São Miguel (Azores archipelago, North-East Atlantic Ocean): first results from shallow soft-bottom habitats

Contrasting (sand, algae, rocky-dominated, mixed) benthic habitats were sampled to characterize marine nematode diversity inhabiting surface sediments in São Miguel (Azores, North-East Atlantic Ocean) in July 2019. Nematodes were extracted from the surface layer of sediments and morphologically identified using light microscopy. Nematode taxonomy was based on living/fresh specimens) to ensure a suitable recognition of morphological traits. Our results provide a preliminary checklist of free-living marine nematode genera from 21 intertidal and sublittoral sandy beach sites along the coast of São Miguel island, Azores archipelago, Portugal. The nematode fauna was represented by 4 orders, 21 families, and 43 genera. Cyatholaimus, Desmodora and Daptonema had two morphospecies each. Enoplida was represented by 8 families and 13 genera, while Chromadorida by 7 families and 18 genera, the latter corresponding to the most diverse nematode group. Monhysterida had 5 families and 10 genera and Araeolaimida was represented by a single 1 family and 2 genera. The most common genera (i.e., accounting for 75% of all organisms) included Adoncholaimus (most abundant genus, 32 specimens), Axonolaimus (18), Cyatholaimus (17), Enoploides (13), Rhabdocoma, and Acanthopharynx (11). Viscosia and Enoplolaimus were represented by 7 specimens, whilst Halalaimus, Desmoscolex, Monophostia, Daptonema, and Theristus obtained only 6 each. The dominant nematode taxa of São Miguel island have been commonly previously reported in other coastal habitats including sandy beaches. They can be considered typical meiofaunal components of intertidal sandy beaches. Many of the nematode morphotypes found in São Miguel island could represent new species to science. As far as we know, this is the first report on free-living nematodes for São Miguel Island and for marine shallow water in the Azores. Our findings will serve as an import baseline for future research aiming to improve our understating of nematode communities in volcanic islands such as São Miguel in the Azores archipelago.