| Scorpion are "living fossil" animals, have a long evolution history for more than400million years, belong to Arthropoda, Chelicerata, Arachnoidea, Scorpiones. Scorpions also are famous venomous animals, and their envenomation is a significant threat to public health. Scorpions are famous and precious traditional Chinese materials, being used to treat many kinds of illness. Scorpion venom contains diverse types of bioactive peptides, which are possibly a treasure house of drug resources. Scorpions are an indispensable part of the ecological food chain, helping maintain a balance among various populations in an ecosystem. They primarily feed on insects. There are2069species of197genera of15families within the order Scorpiones reported all over the world. Scorpions distributed in all continents except Antarctica, but they are most abundant and diverse in tropical and subtropical regions. On one hand, the scorpions from China were previously identified and named by foreigners. Recently, Chinese researchers began to study the taxonomy of scorpions. However, scorpion resources survey and fauna don’t been finished in China systemically. The basic information on habitat, distribution and taxonomy of the order Scorpiones from China aren’t completed yet. On the other hand, scorpion is the representative and typical species of arachnids with unique biological features, but its genetic basis is still unknown. So research the taxonomy, distribution, fauna, genome sequencing of scorpions from China, and revealing scorpion genetic basis can help us not only to understand the evolution characters of the representative and typical species of arachnids, but also to find the multifarious polypeptides drug resources.Firstly, this study based on the distribution survey and specimens collection, identified Chinese scorpion specimens, and then revised the checklist and key of the scorpions of China. According to the standards of modern systematic zoology, all of the scorpion specimens collectied by our lab were identified. Three new species(Euscorpiops puerensis Di, Wu, Cao, Xiao&Li,2010; Euscorpiops validus Di, Cao, Wu&Li,2010; Scorpiops jingshanensis sp.n) and one new record(Euscorpiops kubani Kovarik,2004) in China were found and described. At the same time, the features and measurement data of Isometrus (Isometrus) maculatus (DeGeer,1778), Lychas mucronatus (Fabricius,1798), Euscorpiops shidian (Qi, Zhu&Lourenco,2005), Euscorpiops xui (Sun&Zhu,2010), Scorpiops jendeki (Kovarik,1994), Scorpiops tibetanus (Hirst,1911), and Liocheles australasiae (Fabricius,1775) were provided. Four scorpion biodiversity richest genus from China were summarized: Mesobuthus with9species and subspecies, Chaerilus with8species, Euscorpiops with11species, and Scorpiops with12species. After the scientific expedition, identification and documents, the updated checklist and key of5families12genus and54species (and subspecies) were provided. All these results give us a primary view of basic information on the taxonomy of Scorpiones from China.Secondly, this research surveyed and summarized the distribution and the fauna of family, genus, and species of scorpions from China. Through the field survey, collection and references analysis, Xizang, Yunnan, Xijiang, Hainan, and North China reigions were found to be the scorpion species-rich areas. The characters of the distribution of scorpions species from China is "East much less West and South much less North". The survey result revealed that the wild scorpion population in China is declining as the utilization of chemical fertilizers and pesticides, overharvesting, and serious damage to natural ecological environment. Followed the zoogeographic regions, we roundly analyzed the fauna of families, genus, and species levels. Just the family Chaerilidae distributes in Oriental, while the other four families located in two or more regions. The12genus from China mainly are Oriental (10) and Palaearctic (9), except the Chaerilus (Oriental), Heterometrus (Oriental), Razianus (Palaearctic) and Tibetiomachus (Palaearctic), whereas the other genus situated in two or more regions. Among54species from China, just6species distributed in two or more regions.54species from China were mainly oriental (16in Southwest China Regin, and13in South China Region) and palaearctic (9in Mongolia-Xinjiang Region, and15in Qinghai-Xizang Regin) regions. Thus, the feature of the scorpion fauna from China appeared to be "families and genus mainly distributing in two or more regions, but species mainly distributing in one region". There are54species and subspecies of12genera covering five families in China, in which34species (63.0%) and1genus are specific. Therefore, the scorpion fauna of China is characterized by widespread cross-border multi-family and genus, but species more local distribution.Thirdly, we collected the specimens of M. martensii from the Fu-niu Mountains, Henan Province, sequenced its genome and study the genome’s basic features in this study. We determined the genome size of M. martensii by flow cytometry analysis of fluorescently PI stained nuclei using chicken erythrocytes as an internal standard. The haploid size of M. martensii was estimated to be1,323.73±39.12Mb. We selected an adult M. martensii male for the extraction of DNA sample for genomic sequencing, and prepared total RNA from another single male scorpion for whole transcriptome sequencing. Meanwhile, total RNA from the venom gland (males and females) of the scorpion M. martensii was isolated for transcriptome study. Genome and transcriptomes were sequenced, assembled, and annotated by Shanghai center for Bioinformation technology successfully. The draft genome (v1.0) about1128.5Mb was having a scaffold N50length of223.6Kb, and a contig N50length of43.1Kb. Used bioinformation technology and the deep transcriptome analyses on the samples of mixed tissues (5.53Gb) and samples of venom tissues (4.52Gb), there are a minimum of32,016protein-coding genes predicted for the M. martensii genome. The GC contents in M. martensii is42.7%for the coding regions and29.6%for the whole genome. M. martensii has a median gene size of-6.7Kb (ORF plus introns) with a mean exon number at3.9per gene. Comparing to T. urticae, we also observed a dramatic increase in total gene number but a reduced gene density in M. martensii. All these results enriched the genomic study of arachnids.Fourthly, based on the the genome and telson transcriptome, identified the genes involving in light signal transduction in scorpion telson and revealed the molecular basis on photoreception function of scorpion telson. Sequence similarity searches against predicted proteins of the M. martensii genome and telson transcriptome were performed by blastp using25(from18families) Drosophila genes described to be involved in visual signal transduction (http://www.flybase.org) as "bait." The result showed that20(17families) visual signal transduction genes were found in scorpion telson. Furthermore, the qPCR also confirmed all of the validated genes expressed in scorpion telson, illustrating the formation of the complete molecular pathway for light sensitivity. The transcriptome information and qPCR result revealed M. martensii eyes utilize all three opsins in visual formation, but the telson is only capable of working with Mmopsin3. A phylogenetic analysis indicated that Mmopsin3forms a clade with the opsins from Hydra magnipapillata, whereas Mmopsinl and Mmopsin2are close to eye-related rhabdopsins from insects and vertebrates. Mmopsin3also appears to be a member of the short-wave-sensitive (UV to blue) opsin family, whereas both Mmopsinl and Mmopsin2belong to the long-wave-sensitive family. The spectrum bias of Mmopsin3agrees with the previously documented scorpion behavior under different wave-lengths. The photosensor function of scorpion telson may play an important role in support of their habitant behaviors. The non-visual photosensor mechanism, first revealed in an animal, raises the questions about the broad use of such function by other arthropods and invertebrates.Finally, this research identified the homeobox genes from the genome of M. martensii, discussed the differences of homeobox genes between animals and revealed the particular molecular characteristics of scorpions. The BLASTP searches was performed in the predicted protein database of the scorpion M. martensii genome. All of the retrieved candidate homeobox genes were further validated using a program in the SMART database to identify whether the protein sequences encoded by the candidate genes contain homeodomains. In all,149homeobox genes were categorized into eight classes including at least81families:67ANTP class genes,33PRD genes, 11LIM genes, five POU genes, six SINE genes,14TLAE genes, five CUT genes, two ZF genes and six unclassified genes maybe the specific genes of scorpion. Overall, the homeobox gene diversities of eight classes are similar with the analyzed Mandibulata arthropods. To determine the cDNA/ESTs available for each identified homeobox gene, a local TBLASTN search was performed on transcriptome data from the scorpion M. martensii using the149putative scorpion hox genes as queries. Transcriptome data suggested that121genes of them were expressed in adults, more than80%(121/149). Based on the assemble result of M. martensii genome, the members and its distribution of Hox clusters were identified. M. martensii has Hox clusters of ten Hox genes, like as the other arthropods and vertebrates, but each member of Hox clusters has two copies. Each pair of copies is highly homologous but not tandem. Furthermore, the scaffold Contig352199of the M. martensii genome had five Hox cluster genes ordered Pb2(MMa55590), Zen2(MMa55591), Lab2(MMa55584), Dfd2(MMa55595), Scr2(MMa55596) and Ftz2(MMa55597). These data indicates that there is not simple gene duplication, but a duplication of the complete Hox cluster in the scorpion M. martensii. Therefore, it can be deduced that M. martensii has a unique pattern of two Hox clusters (Hox A and Hox B), which appears to be a specific expansion in Chelicerata. This observation expands the organizational structures of Hox gene clusters reported in arthropods from the single Hox cluster previously reported. |
PDF Full Text Request