Mitogenome selection shaped the terrestrial adaptation of Grapsidae (Decapoda: Brachyura).

The colonization of aquatic to terrestrial habitats by brachyuran crabs requires genetic innovations as well as morphological adaptations to adapt to terrestrial environments. The genetic basis of such adaptive evolution, however, is largely unknown. This study focuses on terrestrialization in Geograpsus (Grapsidae) the only highly terrestrial genus in this family, which represents a notable example of terrestrial adaptive radiation. Here, we sequenced the mitogenomes of two Geograpsus species and used the mitogenomes of 215 representative crabs to construct phylogenetic and time frameworks that we used to infer terrestrial origins and evolution. Using mitochondrial genomic data, we demonstrated that marine crab ancestors began to settle on land during the early Eocene. Ocean acidification, the Paleocene-Eocene Thermal Maximum (PETM), and mangrove expansion at that time may have driven the diversification and ecological expansion of these terrestrial crabs. Evolutionary analyses reveal strong positive selection signals on monophyletic lineages of Grapsidae, especially the terrestrial species of Geograpsus. Positively selected sites in functionally important regions of ND5 and ND4 may imply enhanced energy metabolism in Grapsidae compared to other crabs, and may have played an important role in their terrestrial adaptation. Overall, our work provides valuable resources and opportunities to reveal the adaptation of crabs to complex terrestrial environments.

Analysis of the Overlength Main Noncoding Region in Metacarcinus magister (Decapoda: Brachyura) and a Phylogenetic Study of the Cancroidea Species.

Complete mitochondrial genomes (mitogenomes) can provide important information regarding the molecular evolution and phylogenetic relationships of marine invertebrates, especially in Brachyura. Only one Cancroidea species of mitogenomes has been sequenced before; in this research, the mitogenomic characteristics of Metacarcinus magister (Cancridae: Cancroidea) are newly studied. The length of the M. magister mitogenome was 48,820 bp, and it contained the typical 13 protein-coding genes, 2 ribosomal RNA genes, and 22 transfer RNA genes. We performed a series of analyses on the characteristics of the mNCR of M. magister. The phylogenetics, life circumstances, and selective pressures were all analyzed to explain the formation of this length, which revealed the length of the M. magister mitogenome to be approximately three times greater than the normal length of Brachyuran mitogenomes. Phylogenetic analyses based on a dataset of 215 Decapodan mitogenomes indicated that all Eriphioidea crabs were clustered together as a group. Moreover, the rearrangement mechanism of the Cancroidea species was predicted to provide stronger evidence for the phylogenetic analysis. In general, the results obtained in this study will contribute to a better understanding of the cause of the unusual length of the M. magister mitogenome and provide new insights into the phylogeny of Brachyura.

Enhanced H2S Gas-Sensing Performance of Ni-Doped ZnO Nanowire Arrays.

Ni-doped ZnO nanowire arrays (Ni-ZnO NRs) with different Ni concentrations are grown on etched fluorine-doped tin oxide electrodes by the hydrothermal method. The Ni-ZnO NRs with a nickel precursor concentration of 0-12 at. % are adjusted to improve the selectivity and response of the devices. The NRs' morphology and microstructure are investigated by scanning electron microscopy and high-resolution transmission electron microscopy. The sensitive property of the Ni-ZnO NRs is measured. It is found that the Ni-ZnO NRs with an 8 at. % Ni precursor concentration have high selectivity for H2S and a large response of 68.9 at 250 °C compared to other gases including ethanol, acetone, toluene, and nitrogen dioxide. Their response/recovery time is 75/54 s. The sensing mechanism is discussed in terms of doping concentration, optimum operating temperature, gas type, and gas concentration. The enhanced performance is related to the regularity degree of the array and the doped Ni3+ and Ni2+ ions, which increases the active sites for oxygen and target gas adsorption on the surface.

High Sensing Performance Toward Acetone Vapor Using TiO2 Flower-Like Nanomaterials.

For real-application gas sensors, high performances (response, selectivity, response/recovery time and stability) are demanded. An effective strategy is applying nanomaterials in gas sensors. In this study, the anatase TiO2 flower-like nanomaterials (FLNMs) are prepared through a one-step hydrothermal method which exhibit high-performance toward acetone vapor. TiO2 FLNMs sensors property are characterized at optimal working temperature of 330 °C with selectivity (acetone), response (S = 33.72 toward 250 ppm acetone), linear dependence (R2 = 0.9913), response/recovery time (46/24 s toward 250 ppm acetone) and long-term stability (30 days). These demonstrate that TiO2 FLNMs get a high performance for acetone sensor. Moreover, the limit of detection of acetone is 0.65 ppm which is lower than that of exhaled air for diabetes (0.8 ppm), indicating that TiO2 FLNMs gas sensor gets potential application in medical diagnosis.