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.

Mesoscopic analysis of drag reduction performance of bionic furrow opener based on the discrete element method.

In order to study the dynamic interface mechanical behavior between soil and agricultural machinery and reveal the causes of tillage resistance, three kinds of bionic furrow opener were designed according to the characteristics of earthworm head surface curve, using the discrete element method to simulate and analyze the process of the furrow openers. The results showed that the order of ditching resistance from large to small is traditional opener, bionic corrugated opener, bionic ridgeline opener, bionic composite opener. With the same ditching speed, the drag reduction effect of the three bionic openers increases with the increase of the ditching depth. During the process of increasing the depth from 30 mm to 60 mm and 90 mm, the ditching resistance of the traditional opener increased from 11.56 N to 28.32 N and 48.61 N as well as the maximum drag reduction ratio increased from 5.58% to 7.20% and 8.93% for the bionic composite opener. With the same ditching depth, the bionic composite opener reached the highest drag reduction rate of all bionic openers when the speed is 100 mm/s, the value is 9.08%. The width of the ditch of the three bionic openers is smaller than that of the traditional opener. Bionic corrugated opener can improve the ditch height and reduce the ditch width,the corrugated structure creates a gap between the surface of the core and the particles, reducing the number of contact and contact area of the particles. The number of contact particles of the three bionic openers is smaller than that of the traditional opener. The bionic composite opener has the smallest force field and the soil disturbance caused by the core share surface is small, the soil is evenly distributed along the core surface. The discrete element simulation shows that the bionic opener can effectively reduce the ditching resistance and improve the quality of ditching, which provides a theoretical basis for subsequent research and optimization.

The complete mitochondrial genome of Artemia persimilis Piccinelli and Prosdocimi, 1968 (Crustacea: Anostraca).

In the study, we report the complete mitochondrial genome of Artemia persimilis Piccinelli and Prosdocimi, 1968 for the first time. The mitochondrial genome of A. persimilis is 15,436 bp in length, with the typical structure of 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs) and 2 ribosomal RNA genes, and a non-coding control region (CR). Phylogenetic analysis showed that A. persimilis was at the basal position among the bisexual Artemia species, which revealed that A. persimilis is likely to be an ancestral clade. The present study could provide effective resources for population genetics study, as well as germplasm conservation in Artemia.

DNA barcoding of Schizothoracinae fishes from the Yarlung Zangbo River in Tibet.

The nine endemic species of the genus Schizothorax from the Yarlung Zangbo River, Tibet comprise a putative cyprinid species flock. In this study, the effectiveness of the COI DNA barcode for Schizothoracinae species identification was verified by using 45 COI sequences covering nine species in four genera of Schizothoracinae fishes. The average Kimura two parameter (K2P) genetic distances within and among species were 0.13% and 8.57%, respectively. The results revealed that most of the species were clearly discriminated by their estimated genetic distances and monophyletic clustering in a maximum likelihood tree. However, insignificant genetic distances were noticed in two reportedly valid species: Schizothorax molesworthi and S. integrilabiatus (0.1%), and the monophyly of S. macropogon could not be recovered in the schizothoracine group. The fishes of S.curilabiatus living in the lower course of Yalung Zangbo River were clustered together with three species from the upper course, which is inconsistent with the geographical distribution of the populations.

The complete mitochondrial genome of Artemia salina Leach, 1819 (Crustacea: Anostraca).

In the study, the complete mitochondrial genome of Artemia salina was reported for the first time. The mitochondrial genome of A. salina is 15,762 bp in length, with the typical structure of 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), and two ribosomal RNA genes, and a major non-coding region (CR). Phylogenetic analysis showed that A. salina has a much closer relationship with A. persimilis compared to other Artemia species. The complete cp genome sequence of A. salina reported here provided an essential resource for further population genetics research and germplasm conservation on Artemia.

Construction of a high-density genetic map and QTL mapping for pearl quality-related traits in Hyriopsis cumingii.

A high-density genetic map is essential for quantitative trait locus (QTL) fine mapping. In this study, 4,508 effective single nucleotide polymorphism markers (detected using specific-locus amplified fragment sequencing) and 475 microsatellites were mapped to 19 linkage groups (LGs) using a family with 157 individuals. The map spanned 2,713 cM, with an average of 259 markers and 79 loci per LG and an average inter-marker distance of 1.81 cM. To identify QTLs for pearl quality traits, 26 putatively significant QTLs were detected for 10 traits, including, three for shell width, seven for body weight, two for shell weight, two for margin mantle weight, five for inner mantle weight, and seven for shell nacre colour. Among them, five QTLs associated with shell nacre colour were mapped to LG17 and explained 19.7% to 22.8% of the trait variation; this suggests that some important genes or loci determine shell nacre colour in LG17. The linkage map and mapped QTLs for shell nacre colour would be useful for improving the quality of Hyriopsis cumingii via marker-assisted selection.