Although diet affects growth and behaviour, the adaptive mechanisms that coordinate these processes in non-optimal food sources are unclear. Here we show that the C. elegans tmc-1 channel, which is homologous to the mammalian tmc deafness genes, attenuates development and inhibits sexual behaviour in non-optimal food, the synthetic CeMM medium. In CeMM medium, signalling from the pharyngeal MC neurons and body wall muscles slows larval development. However, in the non-standard diet, mutation in tmc-1 accelerates development, by impairing the excitability of these cells. The tmc-1 larva can immediately generate ATP when fed CeMM, and their fast development requires insulin signalling. Our findings suggest that the tmc-1 channel indirectly affects metabolism in wild-type animals. In addition to regulating the development, we show that mutating tmc-1 can relax diet-induced inhibition of male sexual behaviour, thus indicating that a single regulator can be genetically modified to promote growth rate and reproductive success in new environments.

Ocean acidification and acid rain, caused by modern industries’ fossil fuel burning, lead to a decrease in the living environmental pH, which results in a series of negative effects on many organisms. However, the underlying mechanisms of animals’ response to acidic pH stress are largely unknown. In this study, we used the nematode Caenorhabditis elegans as an animal model to explore the regulatory mechanisms of organisms’ response to pH decline. Two major stress-responsive pathways were found through transcriptome analysis in acidic stress environments. First, when the pH dropped from 6.33 to 4.33, the worms responded to the pH stress by upregulation of the col, nas, and dpy genes, which are required for cuticle synthesis and structure integrity. Second, when the pH continued to decrease from 4.33, the metabolism of xenobiotics by cytochrome P450 pathway genes (cyp, gst, ugt, and ABC transporters) played a major role in protecting the nematodes from the toxic substances probably produced by the more acidic environment. At the same time, the slowing down of cuticle synthesis might be due to its insufficient protective ability. Moreover, the systematic regulation pattern we found in nematodes might also be applied to other invertebrate and vertebrate animals to survive in the changing pH environments. Thus, our data might lay the foundation to identify the master gene(s) responding and adapting to acidic pH stress in further studies, and might also provide new solutions to improve assessment and monitoring of ecological restoration outcomes, or generate novel genotypes via genome editing for restoring in challenging environments especially in the context of acidic stress through global climate change.

Nematodes play key roles in marine ecosystem. Although oceans cover 71% of the Earth’s surface, none of marine model nematode has been reported. Here, we constructed the first inbred line of free-living marine nematode Litoditis marina , sequenced and assembled its genome. Furthermore, we successfully applied CRISPR/Cas9 genome editing in L. marina . Comparative genomics revealed that immunity and oxygen regulation genes are expanded, which is probably central to its sediment adaptation. While L. marina exhibits massive gene contractions in NHRs, chemoreceptors, xenobiotics detoxification and core histones, which could explain the more defined marine environment. Our experiments showed that dozens of H4 genes in Caenorhabditis elegans might contribute to its adaptation to the complex terrestrial environments, while two H4 genes in L. marina are involved in salinity stress adaptation. Additionally, ninety-two conserved genes appear to be positively selected in L. marina , which may underpin its osmotic, neuronal and epigenetic changes in the sea. With short generation time, highly inbred lines, and genomic resources, our report brings L. marina a promising marine animal model, and a unique satellite marine model to the well-known biomedical model nematode C. elegans . This study will underpin ongoing work on animal functional genomics, environmental adaptation and developmental evolution.

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, which might contribute to hyposaline acclimation, while the glycerol biosynthesis genes gpdh-1 and gpdh-2 accompanied hypersaline acclimation in L. marina. This study paves the way for further in-depth exploration of the adaptive mechanisms underlying euryhalinity and may also contribute to the study of healthy ecosystems in the context of global climate change.

Maintenance of osmotic homeostasis is essential for all organisms, especially for marine animals in the ocean with 3% 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. By contrast, cuticle related collagen genes were enriched and up-regulated for hypersaline response. 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.