Darwin3: a large-scale neuromorphic chip with a novel ISA and on-chip learning.

Spiking neural networks (SNNs) are gaining increasing attention for their biological plausibility and potential for improved computational efficiency. To match the high spatial-temporal dynamics in SNNs, neuromorphic chips are highly desired to execute SNNs in hardware-based neuron and synapse circuits directly. This paper presents a large-scale neuromorphic chip named Darwin3 with a novel instruction set architecture, which comprises 10 primary instructions and a few extended instructions. It supports flexible neuron model programming and local learning rule designs. The Darwin3 chip architecture is designed in a mesh of computing nodes with an innovative routing algorithm. We used a compression mechanism to represent synaptic connections, significantly reducing memory usage. The Darwin3 chip supports up to 2.35 million neurons, making it the largest of its kind on the neuron scale. The experimental results showed that the code density was improved by up to 28.3× in Darwin3, and that the neuron core fan-in and fan-out were improved by up to 4096× and 3072× by connection compression compared to the physical memory depth. Our Darwin3 chip also provided memory saving between 6.8× and 200.8× when mapping convolutional spiking neural networks onto the chip, demonstrating state-of-the-art performance in accuracy and latency compared to other neuromorphic chips.

Ultrastructural diversity in the shell of Artemia resting eggs.

The shell of Artemia resting egg, which is a delicate multilayered envelope surrounding the inside diapause embryo, plays an important role in the survival strategy of Artemia. To date, the ultrastructure of resting eggshell has been studied for only handful populations, and knowledge about the diversity of shell structure is still limited. In this paper, resting eggs from 13 Artemia populations were studied by transmission electron microscopy. Results show that the basic configuration of resting eggshell is quite conservative, but variations are not uncommon in the fine ultrastructure of each main layer of the shell (e.g., the shape and distribution of the radially oriented pores in the cortical layer; the size, number and arrangement of chambers in the alveolar layer; and the development state of outer cuticular membrane [OCM]). The ultrastructural variation of eggshell seems not to be linked with species and reproductive mode of Artemia. Resting eggs from very high habitats (4300+ m above sea level [a.s.l.]) on Qinghai-Tibet Plateau and certain tropical salterns have a hypoplastic OCM, which may be related to the adaptation to habitat conditions such as low oxygen concentration. RESEARCH HIGHLIGHTS: Comparative study on resting eggs from 13 Artemia populations reveals high diversity in the fine structure of eggshell. Resting eggs from very high (4300+ m a.s.l.) habitats commonly have a hypoplastic OCM.

Temporal genetic variation mediated by climate change-induced salinity decline, a study on Artemia (Crustacea: Anostraca) from Kyêbxang Co, a high altitude salt lake on the Qinghai-Tibet Plateau.

The Qinghai-Tibet Plateau is one of the areas the richest in salt lakes and Artemia sites. As a result of climate warming and wetting, the areas of salt lakes on the plateau have been increasing, and the salinities have decreased considerably since 1990s. However, the impact of salinity change on the genetic diversity of Artemia is still unknown. Kyêbxang Co is the highest (4620 m above sea level) salt lake currently with commercial harvesting of Artemia resting eggs in the world, and harbors the largest Artemia population on the plateau. Its salinity had dropped from âˆ¼67 ppt in 1998 to âˆ¼39 ppt in 2019. Using 13 microsatellite markers and the mitochondrial cytochrome oxidase submit I (COI) gene, we analyzed the temporal changes of genetic diversity, effective population size and genetic structure of this Artemia population based on samples collected in 1998, 2007 and 2019. Our results revealed a steady decline of genetic diversity and significant genetic differentiation among the sampling years, which may be a consequence of genetic drift and the selection of decreased salinity. A decline of effective population size was also detected, which may be relative to the fluctuation in census population size, skewed sex ratio, and selection of the declined salinity. In 2007 and 2019, the Artemia population showed an excess of heterozygosity and significant deviation from Hardy-Weinberg Equilibrium (p < 0.001), which may be associated with the heterozygote advantage under low salinity. To comprehensively understand the impact of climate warming and wetting on Artemia populations on the plateau, further investigation with broad and intensive sampling are needed.

Population genetics of Artemia urmiana species complex (Crustacea, Anostraca): A group with asymmetrical dispersal and gene flow mediated by migratory waterfowl.

Bird-mediated dispersal of resting eggs is the main mechanism for Artemia dispersal among catchments. The bisexual populations of Artemia urmiana species complex, which is here considered to be a collection of Artemia genetically close to the so-called "Western Asian Lineage", are mostly distributed in central and western Asia (i.e., in regions falling into the Central Asian Flyway of migratory birds) and live in diversified habitats. Little is known about the genetic relationships among these populations. Aiming to understand the population genetic characteristics and the roles of migratory birds on the dispersal and gene flow of this Artemia group, we evaluated the genetic diversity, genetic differentiation, and gene flow among 14 populations, with their altitudes ranging from 540 to 4870 m above sea level, using 13 microsatellite markers. Almost all populations exhibited high genetic diversity and heterozygote excess, which may be a consequence of combined effects of dispersal and hybridization. The global genetic differentiation (FST) value was 0.092, the pairwise FST values were 0.003-0.246. Discriminant analysis of principal components identified three genetic clusters, consisting of Urmia Lake (Iran), Zhundong (Xinjiang, China), and 12 Qinghai-Tibet Plateau populations, respectively. The among-population genetic differentiation seems to be a consequence of isolation by distance and adaptation to diversified habitats induced by altitudinal gradient. Historical gene flows are asymmetrical, and show an evolutionary source-sink dynamics, with Jingyu Lake (Xinjiang, China) population being the major source. These results support our hypothesis that in Qinghai-Tibet Plateau and surrounding areas the bird-mediated dispersal of Artemia may be biased towards from north to south and/or from higher altitude to lower altitude.

Combined effects of temperature, photoperiod, and salinity on reproduction of the brine shrimp Artemia sinica (Crustacea: Anostraca).

Background: Artemia sinica is a brine shrimp species distributed in hypersaline salt lakes in northern China and Siberia and a successful invasive species in some coastal salterns. Although it is a commercially harvested and cultured species, knowledge of its reproductive characteristics is limited, and existing studies are often contradictory. The combined effects of temperature, salinity, and photoperiod on reproduction characteristics are experimentally studied to better understand its reproductive features. Methods: There were 36 combinations of three environmental factors (3 × 3 × 4), each with three or four levels, namely temperature (16, 25, 30 °C), photoperiod (6 L:18 D, 12 L:12D, 18 L:6D), and salinity (50, 100, 150, 200 PSU). In each treatment, 48 to 80 pairs of A. sinica from Yuncheng Salt Lake (Shanxi, China) were cultured. Females were observed daily for reproductive mode and the number of offspring produced. Results: Temperature, photoperiod, salinity, and their interactions significantly affected the lifespan and reproduction of A. sinica. The reproductive period was the longest and accounted for the largest proportion of life span at moderate temperature (25 °C). Total offspring, offspring per brood, and offspring per day increased as salinity decreased, and the number of broods per female was highest at 25 °C. Temperature, photoperiod, and salinity significantly influenced reproductive modes, and interactions among these factors were identified. Artemia sinica primarily reproduces oviparously under low temperature and short daylight conditions, and ovoviviparously under high temperature and long daylight conditions, with the maximum oviparity ratio recorded in treatments of 16 °C, 6L:18D, and 50 or 100 PSU. The maximum ovoviviparity ratio was recorded under 30 °C, 12L:12D, and 100 PSU. Unlike that documented for other Artemia species or populations, the brood size of A. sinica kept increasing throughout the reproductive period. It did not decline even in the last two broods. For the same brood number, the sizes of oviparous and ovoviviparous broods were similar. The length of the oviparous interval was often greater than that of the ovoviviparous interval, suggesting that oviparous offspring might require additional energy and time to construct the multi-layered eggshell. Compared to other species and populations, the A. sinica from Yuncheng Salt Lake has a relatively shorter pre-reproductive development time, a preference for ovoviviparity, and relatively higher fecundity and population growth capacity, making it a suitable culture species for obtaining fresh biomass.

Sources and transformations of nitrate in Qixiangcuo Lake and its inflow rivers in the northern Tibetan Plateau.

Human activities and climate change input more reactive nitrogen into alpine lakes. Alpine saline lakes are usually located in endorheic watersheds at high-altitude areas, with no other drainage methods than evaporation, and are prone to accumulate nutrients. Meanwhile, alpine saline lakes are usually oligotrophic and sensitive to reactive nitrogen inputs, and even modest reactive nitrogen inputs may have significant effects on them, such as eutrophication. Nitrate is the main form of reactive nitrogen in lakes; therefore, clarifying the sources and transformations of nitrate in alpine saline lakes is important to prevent or mitigate eutrophication in alpine saline lakes. In this study, the sources and transformations of nitrate in Qixiangcuo Lake and its inflow rivers in the northern Tibetan Plateau were identified using dual nitrate isotopes and hydrochemistry. The results show that (1) the ranges of NO3- concentrations, δ15N - NO3-, and δ18O - NO3- values were 3.6 ~ 26.1 µg/L, - 10.5 to + 6.0‰, and - 10.4 to + 9.2‰ in Qixiangcuo Lake and 194.4 ~ 728.1 µg/L, + 5.8 ~ + 8.8‰, and - 1.9 to + 2.4‰ in its inflow rivers, respectively. The NO3- concentrations and δ15N - NO3- values were significantly lower in Qixiangcuo Lake than in its inflow rivers (P < 0.05). (2) The main sources of nitrate in both surface water and bottom water of Qixiangcuo Lake were ammonium in atmospheric deposition (mean probability estimate (MPE) 41.0% and 32.2%, respectively) and livestock manure (MPE 28.9% and 21.7%, respectively). The main sources of nitrate in the inflow rivers of Qixiangcuo Lake were domestic sewage (MPE 35.7%) and livestock manure (MPE 29.6%). (3) The main nitrogen transformation process in Qixiangcuo Lake was nitrification. The conservative mixing of multiple sources controlled the nitrate concentration and isotopic composition of Qixiangcuo Lake. Improvement in grazing area planning and the installation of sewage treatment facilities are effective measures to prevent eutrophication in Qixiangcuo Lake and its inflow rivers.

Phylogenetic Relationships and Taxonomic Position of the Ribbon Worms of the Genus Parahubrechtia (Nemertea, Palaeonemertea) with Descriptions of Two New Species.

The genus Parahubrechtia Gibson and Sundberg, 1999 was first described within the family Hubrechtiidae (class Pilidiophora) and subsequently transferred to the family Callineridae (class Palaeonemertea). Here we describe two new species, Parahubrechtia rayi sp. nov. from the Sea of Japan (Russia) and P. peri sp. nov. from the South China Sea (China). A phylogenetic analysis based on partial sequences of five nuclear and mitochondrial gene regions, 18S rRNA, 28S rRNA, histone H3, 16S rRNA, and COI, has confirmed the monophyly of the genus Parahubrechtia, and indicated a close relationship to Callinera Bergendal, 1900, whose monophyly is not confirmed. Both genera belong to the family Tubulanidae, with its junior synonym being Callineridae. Three major subclades are distinguished within the Tubulanidae: subclade Tubulanus s. str., subclade Tubulanus punctatus, and subclade Parahubrechtia + Callinera. The further status of Parahubrechtia depends on whether the paraphyly of Callinera is confirmed or not and how the problem of paraphyly of the genus Tubulanus Renier, 1804 is resolved.

Distribution and potential sources of microplastics in sediments in remote lakes of Tibet, China.

The prevalence of microplastics in water bodies such as oceans and rivers has received considerable attention in recent years. The present study contributes to this research effort by assessing microplastics in 12 remote lakes on the Tibetan Plateau, China. Despite the limited extent of human activities, at least 17 items and up to 2644 items of microplastics were found per kg of dried sediments collected from the lakes in Tibet. These values were considered high compared to the levels of microplastics reported in other lake areas worldwide. Our results showed that the most prevailing types of microplastics in the sediments were black or transparent fibers in the size range of 0.05-0.5 mm, which were mainly identified to be polyamide and polyethylene terephthalate using Fourier-transform infrared microspectroscopy. The number of microplastics found appeared to be higher in sediments with a higher silt and clay content. Atmospheric long-range transport, glacial meltwater and surface runoff represent potential pathways to carry microplastics from elsewhere to the remote lakes in Tibet. This study shall be of great significance in understanding the transport and distribution of microplastics in the environment at regional or global scale.

Expression of Piwi Genes during the Regeneration of Lineus sanguineus (Nemertea, Pilidiophora, Heteronemertea).

The transposon silencer piwi genes play important roles in germline determination and maintenance, gametogenesis, and stem-cell self-renewal, and the expression of certain piwi genes is indispensable for regeneration. Knowledge about piwi genes is needed for phylum Nemertea, which contains members (e.g., Lineus sanguineus) with formidable regeneration capacity. By searching the L. sanguineus genome, we identified six Argonaute genes including three ago (Ls-Ago2, Ls-Ago2a, and Ls-Ago2b) and three piwi (Ls-piwi1, Ls-piwi2, and Ls-piwi3) genes. In situ hybridization revealed that, in intact females, Ls-piwi2 and Ls-piwi3 were not expressed, while Ls-piwi1 was expressed in ovaries. During regeneration, Ls-piwi1 and Ls-pcna (proliferating cell nuclear antigen) had strong and similar expressions. The expression of Ls-piwi1 became indetectable while Ls-pcna continued to be expressed when the differentiation of new organs was finished. During anterior regeneration, expression signals of Ls-piwi2 and Ls-piwi3 were weak and only detected in the blastema stage. During posterior regeneration, no expression was observed for Ls-piwi2. To date, no direct evidence has been found for the existence of congenital stem cells in adult L. sanguineus. The "pluripotent cells" in regenerating tissues are likely to be dedifferentiated from other type(s) of cells.

An overview on the nomenclatural and phylogenetic problems of native Asian brine shrimps of the genus Artemia Leach, 1819 (Crustacea, Anostraca).

The genus Artemia Leach, 1819 is a cosmopolitan halophilic crustacean, consisting of bisexual species and obligate parthenogenetic populations. Asia is rich in Artemia biodiversity. More than 530 Artemia sites have been recorded from this area and more than 20 species/subspecies/variety names have been used for them. There exist various problems in the nomenclature, identification, and phylogenetic status of Artemia native to Asia, which are discussed in this paper.

The impact of one-decade ecological disturbance on genetic changes: a study on the brine shrimp Artemia urmiana from Urmia Lake, Iran.

Urmia Lake, the largest natural habitat of the brine shrimp Artemia urmiana, has progressively desiccated over the last two decades, resulting in a loss of 80% of its surface area and producing thousands of hectares of arid salty land. This ecological crisis has seriously affected the lake's native biodiversity. Artemia urmiana has lost more than 90% of its population during the decade from 1994 (rainy period) to 2004 (drought period) due to salinity increasing to saturation levels (∼300 g/l). We studied the influence of this ecological crisis on the genetic diversity of A. urmiana in Urmia Lake, based on one cyst collections in 1994 and 2004. AMOVA analysis on ISSR data demonstrated a 21% genetic variation and there was a 5.5% reduction of polymorphic loci between samples. PCoA showed that 77.42% and 68.75% of specimens clustered separately in 1994 and 2004, respectively. Our analyses of four marker genes revealed different genetic diversity patterns with a decrease of diversity at ITS1 and an increase for Na+/K+ ATPase. There was no notable difference in genetic variation detected for COI and 16S genes between the two periods. However, they represented distinctly different haplotypes. ITS1 and COI followed a population expansion model, whereas Na+/K+ ATPase and 16S were under demographic equilibrium without selective pressure in the 1994 samples. Neutrality tests confirmed the excess of rare historical and recent mutations present in COI and ITS1 in both samples. It is evident that a short-term ecological disturbance has impacted the genetic diversity and structure of A. urmiana.

Morphological and molecular study on Yininemertespratensis (Nemertea, Pilidiophora, Heteronemertea) from the Han River Estuary, South Korea, and its phylogenetic position within the family Lineidae.

Outbreaks of ribbon worms observed in 2013, 2015, and 2017-2019 in the Han River Estuary, South Korea, have caused damage to local glass-eel fisheries. The Han River ribbon worms have been identified as Yininemertespratensis (Sun & Lu, 1998) based on not only morphological characteristics compared with the holotype and paratype specimens, but also DNA sequence comparison with topotypes freshly collected near the Yangtze River mouth, China. Using sequences of six gene markers (18S rRNA, 28S rRNA, histone H3, histone H4, 16S rRNA, and COI), the phylogenetic position of Y.pratensis was inferred among other heteronemerteans based on their sequences obtained from public databases. This analysis firmly placed Y.pratensis as a close relative to Apatronemertesalbimaculosa Wilfert & Gibson, 1974, which has been reported from aquarium tanks containing tropical freshwater plants in various parts of the world as well as a wild environment in Panama.

Octopicola huanghaiensis n. sp. (Copepoda: Cyclopoida: Octopicolidae), a new parasitic copepod of the octopuses Amphioctopus fangsiao (d'Orbigny) and Octopus minor (Sasaki) (Octopoda: Octopodidae) in the Yellow Sea.

A new species of parasitic copepod, Octopicola huanghaiensis n. sp., collected from the octopuses Amphioctopus fangsiao (d'Orbigny) and Octopus minor (Sasaki) (Octopoda: Octopodidae) in the Yellow Sea (off Qingdao, Shandong Province, China), is described. The new species is most similar to O. superba Humes, 1957, but can be distinguished from the latter by: (i) the third antennal segment having a different ornamentation; (ii) the fourth antennal segment of females much shorter than that in O. superba (49 vs 94 µm); (iii) males much smaller than females (mean body length 1.3 vs 2.0 mm, respectively) (vs similar male and female body size in O. superba, 1.9 mm and 1.8 mm respectively); and (iv) the presence of a spike at the posterior tip of each labrum flap. Octopicola huanghaiensis n. sp. is the first species of Octopicola Humes, 1957 reported from A. fangsiao and O. minor and is the only species of the family Octopicolidae Humes & Boxshall, 1996 known in North Pacific waters.

Three new species of Marphysa Quatrefages, 1865 (Polychaeta: Eunicida: Eunicidae) from the south coast of China and redescription of Marphysa sinensis Monro, 1934.

Three new species of Marphysa Quatrefages, 1865 (Polychaeta: Eunicida: Eunicidae) are described from the south coast of China, M. tripectinata n. sp., M. multipectinata n. sp. and M. tribranchiata n. sp. with comments on the usefulness of pectinate chaetae to separate species. Marphysa sinensis Monro, 1934 is redescribed with a lectotype designated. The genus Marphysa is widely collected for bait and export for recreational fishermen and anglers in China and yet the number of species involved and their native distribution is currently unknown. Such information is critical for aquaculture programs which are rearing these species.

Morphological differentiation of seven parthenogenetic Artemia (Crustacea: Branchiopoda) populations from China, with special emphasis on ploidy degrees.

Parthenogenetic Artemia from seven Chinese locations with different elevations and various ploidies are characterized by phenotypic and morphometric analyses. Our findings show that the studied populations exhibit dissimilar patterns of ovisac. Four phenotypic patterns of furca are qualified and one of them is shared among di-, tetra- and pentaploid Artemia. Results of discriminant analysis based on morphometric data reveal that tetra- and pentaploid populations are grouped together, but the Aqqikkol Lake population is clearly differentiated. Previous hypothesis/conclusion that polyploid Artemia are larger than diploids is only partly supported by the present results, which show that pentaploid and tetraploid populations are larger than the mostly diploid populations in terms of the total length, but the body size of the Aibi Lake triploids has not significant difference with the sympatric diploids and the mostly diploid Aqqikkol population that inhabit in very high altitude has the largest body size among all parthenogenetic populations. The founding confirms that body size of Artemia is following with Bergmann's rule.

The complete mitochondrial genome of Tetrastemma olgarum (Nemertea: Hoplonemertea).

The complete mitochondrial genome (mitogenome) of Tetrastemma olgarum is sequenced. It is 14,580 bp in length and contains 37 genes typical for metazoan mitogenomes. The gene order is identical to that of the previously published Hoplonemertea mitogenomes. All genes are encoded on the heavy strand except for trnT and trnP. The coding strand is AT-rich, accounting for 69.2% of overall nucleotide composition.

Species Diversity of Ramphogordius sanguineus/Lineus ruber-Like Nemerteans (Nemertea: Heteronemertea) and Geographic Distribution of R. sanguineus.

Heteronemerteans, such as Lineus ruber, L. viridis, Ramphogordius sanguineus, R. lacteus, Riseriellus occultus, and Micrura varicolor, share many similar external characters. Although several internal characters useful for distinguishing these nemertean species have been documented, their identification is based mostly on coloration, the shape of the head, and how they contract, which may not be always reliable. We sequenced the mitochondrial COI gene for 160 specimens recently collected from 27 locations around the world (provisionally identified as the above species, according to external characters and contraction patterns, with most of them as R. sanguineus). Based on these specimens, together with sequences of 16 specimens from GenBank, we conducted a DNA-based species delimitation/identification by means of statistical parsimony and phylogenetic analyses. Our results show that the analyzed specimens may contain nine species, which can be separated by large genetic gaps; heteronemerteans with an external appearance similar to R. sanguineus/Lineus ruber/L. viridis have high species diversity in European waters from where eight species can be discriminated. Our 42 individuals from Vancouver Island (Canada) are revealed to be R. sanguineus, which supports an earlier argument that nemerteans reported as L. ruber or L. viridis from the Pacific Northwest may refer to this species. We report R. sanguineus from Chile, southern China, and the species is also distributed on the Atlantic coast of South America (Argentina). In addition, present analyses reveal the occurrence of L. viridis in Qingdao, which is the first record of the species from Chinese waters.

DNA Taxonomy of Paranemertes (Nemertea: Hoplonemertea) with Spirally Fluted Stylets.

Of the 14 nominal species that are now or have ever been assigned to the genus Paranemertes Coe, 1901 , four have been reported to have stylets with a spirally fluted or braided appearance. Although differentiation in color patterns has been documented among species/populations, these nemerteans share similar external characters. Using the sequence datasets of mitochondrial cytochrome c oxidase subunit I (COI), 16S rRNA, and nuclear 28S rRNA genes of specimens from 14 localities of Canada, USA, Russia, Japan, and China, we analyzed the genetic differentiation and reconstructed the phylogenetic trees for these nemerteans. In conjunction with the external characters, we discuss their taxonomy and species delimitation. An analysis based on COI dataset showed high genetic variations among populations and even among worms from the same geographic area. The analyzed 111 individuals were assigned into seven networks by statistical parsimony analysis. The inter-network uncorrected p-distances ranged from 0.044 to 0.172 and the mean intra-network uncorrected p-distances varied from 0.001 to 0.005. With the exception of two networks that contain specimens from the East China Sea, all networks were well-supported by the results of Bayesian and neighbor-joining analyses on the COI data. Phylogenetic trees based on 16S rRNA and 28S rRNA datasets were basically similar to the COI trees, but specimens in some networks were merged into larger clades. Present molecular analyses support the validity of P. sanjuanensis and the synonymization of P. cylindracea with P. peregrina. Nemerteans previously recorded as P. peregrina may contain several species and sympatric speciation might have been occurred in this nemertean group.

Phycoerythrins in phycobilisomes from the marine red alga Polysiphonia urceolata.

Phycoerythrins (PE) in phycobilisomes from Polysiphonia urceolata were studied in this research. Dissociative products of phycobilisomes were analyzed by sucrose density gradient centrifugation and native-PAGE. At least three types of PEs were found in the dissociative products of phycobilisomes. According to their molecular weights, absorption spectra and subunit components, they should be PE hexamer containing γ1 subunit, PE hexamer containing γ2 subunit and PE monomer containing no γ subunit. PEs bigger than hexmer were also found in the dissociative products of phycobilisomes in 200mM phosphate buffer when dissociated phycobilisomes were analyzed by sucrose density gradient centrifugation. PE trimers containing no γ subunits were also found in products of dissociated phycobilisomes in deionized water when dissociated phycobilisomes were analyzed by native-PAGE. This is the first time that pure PE hexamers containing γ2 subunits were isolated from P. urceolata. The PE monomers containing no γ subunits should come from PE trimers or hexamers containing no γ subunits in the "rod" of phycobilisomes. It can be concluded that there are three types of PEs in "rod" of phycobilisomes from P. urceolata: PE containing γ1 subunit, PE containing γ2 subunit and PE containing no γ subunit.