Genomic insights into mite phylogeny, fitness, development, and reproduction.

BACKGROUND: Predatory mites (Acari: Phytoseiidae) are the most important beneficial arthropods used in augmentative biological pest control of protected crops around the world. However, the genomes of mites are far less well understood than those of insects and the evolutionary relationships among mite and other chelicerate orders are contested, with the enigmatic origin of mites at one of the centres in discussion of the evolution of Arachnida. RESULTS: We here report the 173 Mb nuclear genome (from 51.75 Gb pairs of Illumina reads) of the predatory mite, Neoseiulus cucumeris, a biocontrol agent against pests such as mites and thrips worldwide. We identified nearly 20.6 Mb (~ 11.93% of this genome) of repetitive sequences and annotated 18,735 protein-coding genes (a typical gene 2888 bp in size); the total length of protein-coding genes was about 50.55 Mb (29.2% of this assembly). About 37% (6981) of the genes are unique to N. cucumeris based on comparison with other arachnid genomes. Our phylogenomic analysis supported the monophyly of Acari, therefore rejecting the biphyletic origin of mites advocated by other studies based on limited gene fragments or few taxa in recent years. Our transcriptomic analyses of different life stages of N. cucumeris provide new insights into genes involved in its development. Putative genes involved in vitellogenesis, regulation of oviposition, sex determination, development of legs, signal perception, detoxification and stress-resistance, and innate immune systems are identified. CONCLUSIONS: Our genomics and developmental transcriptomics analyses of N. cucumeris provide invaluable resources for further research on the development, reproduction, and fitness of this economically important mite in particular and Arachnida in general.

Phylogeography of lethal male fighting in a social spider mite.

When males fight for access to females, such conflict rarely escalates into lethal fight because the risks and costs involved, that is, severe injury or death, are too high. The social spider mite, Stigmaeopsis miscanthi, does exhibit lethal male fights, and this male-male aggressiveness varies among populations. To understand the evolution of lethal fighting, we investigated aggressiveness in 42 populations and phylogenetic relationships in 47 populations along the Japanese archipelago. By analysis of the male weapon morph, a proxy for aggressiveness, we confirmed the existence of a mildly aggressive (ML) form, besides the low aggression (LW) and high aggression (HG) forms reported earlier. To evaluate demographic history of these three forms, we employed the approximate Bayesian computation approach using mtCOI sequences and taking into consideration the postlast glacial expansion history of the host plant, Miscanthus sinensis. As results, hierarchical split models are more likely to explain the observed genetic pattern than admixture models, and the ML form in the subtropical region was considered the ancestral group. The inferred demographic history was consistent with the one reconstructed for the host plant in a previous study. The LW form was split from the ML form during the last glacial period (20,000-40,000 years BP), and subsequently, the HG form was split from the ML form at the end of or after the last glacial period (5,494-10,988 years BP). The results also suggest that the mite invaded Japan more than once, resulting in the present parapatric distribution of LW and HG forms in eastern Japan.

Variation in nesting behavior of eight species of spider mites, Stigmaeopsis having sociality.

Nesting behavior is considered to be an important element of social living in animals. The spider mites belonging to the genus Stigmaeopsis spend their lives within nests produced from silk threads. Several of these species show cooperative sociality, while the others are subsocial. In order to identify the origins of this social behavior, comparisons of nest sizes, nesting behaviors (making nests continuously or separately), and their associated traits (fecal deposition patterns) were made for eight cogeneric Stigmaeopsis species showing various levels of social development. All of these species inhabit bamboo plants (Poaceae). We initially addressed the proximate factor of nest size variation. The variation in nest size of the eight species corresponded well with the variation in dorsal seta sc1 length, suggesting that nest size variation among species may have a genetic basis. The time spent within a nest (nest duration) increased with nest size on the respective host plants. Nest arrangement patterns varied among species showing different sized nests: Large nest builders continuously extended their nests, while middle and small nest-building species built new separate nests, which resulted in different social interaction times among species, and is thought to be closely related to social development. Fecal deposition behaviors also varied among Stigmaeopsis species, suggesting diversity in anti-predatory adaptations. Finally, we discuss how the variation in sociality observed within this genus is likely the result of nest size variation that initially evolved as anti-predator strategies.

Reproductive isolation between Stigmaeopsis celarius and its sibling species sympatrically inhabiting bamboo (Pleioblastus spp.) plants.

Stigmaeopsis celarius Banks (hereafter Sc) is a spider mite living and feeding on the leaves of various bamboo species such as Moso bamboo [Phyllostachys edulis (=P. pubescens)] and Pleioblastus spp. (Poaceae). A previous phylogenetic study revealed a cryptic, phylogenetic sister species to Sc (hereafter Ss). Although its life type appears to be similar to that of Sc, individuals of Ss make much smaller nests compared with Sc, and the nests have been found mostly on Nezasa bamboo (Pleioblastus argenteostriatus). To investigate whether Sc and Ss are reproductively isolated, we explored their populations in southwestern Japan, and crossed them to examine mating behaviors and fertilization success. Field surveys revealed that the nests of these two species occur on the same leaves and, thus, the individuals of these species may make frequent contact. Reciprocal crosses suggested that the two species are reproductively isolated. Though Sc males have tried to mate with Ss females, copulation seldom occurred because of their long opisthosoma (hind body), which prevented the insertion of the aedeagus into the genitalia of Ss females. In contrast, most Ss males ignored Sc females, and eggs were not fertilized even in the few cases where copulation appeared to occur. These results suggest that strong selection pressure is imposed on body length to prevent interspecific hybridization in the contact area of these species.

[Clinical study of pulmonary infection in kidney transplantation recipients taking new immunosuppressant].

OBJECTIVE: To explore the etiopathogenesis, therapy and incidence of pulmonary infection in kidney transplantation recipients taking new immunosuppressant. METHODS: The clinical data from 752 kidney transplant recipients were retrospectively analyzed, who were divided into 3 groups according to the immunosuppressants administered, namely group A (CsA+MMF+Pred, n=226), group B (FK506+MMF+Pred, n=386) and group C (FK506+Rap+Pred, n=140). The incidence and mortality of pulmonary infection were recorded and the analysis of etiopathogenesis, diagnosis and therapy of pulmonary infection were carried out in the 3 groups. RESULTS: Fifty-three patients acquired post-transplant pulmonary infection. The incidence of pulmonary infection was 7.08% (16/226) in group A, 7.25% (28/386) in group B and 6.43% (9/140) in group C. One patient died in group A and 2 in group B. Among the 53 patients, 24 had simple bacterial infection, 9 had cytomegalovirus infection, 1 had mycotic infection, 17 had combined infection, and 2 had unidentified pathogen infection. Of the pathogenic bacteria detected, 68.35% were Gram-negative. CONCLUSION: Gram-negative bacteria are most likely responsible for pulmonary infection after kidney transplantation, which most possibly occurs within 6 months after kidney transplantation. Early diagnosis and early treatment are critical for decreasing the mortality of severe pneumonia and for improving the survival rate of the patients and grafts.

[Application of tacrolimus and cyclosporine A in HBV-carrying renal transplant recipients].

OBJECTIVE: To compare the long-term effect and safety of tacrolimus (FK506) and cyclosporine (CsA) in kidney transplant (KT) recipients carrying hepatitis B Virus(HBV). METHODS: A total of 109 patients with HBV were randomized into FK506 group (52 cases) and CsA group (57 cases) after KT, and a 2-year-long follow-up of the patients was conducted to record the patient and graft survival, incidence of acute graft rejection and postoperative liver function. RESULTS: The 2-year patient/graft survival was 86.0%/73.7% and 94.2%/90.3% in CsA and FK506 groups, respectively (P<0.05), with incidence of acute rejection of 10.5% and 9.6% (P>0.05), and rate of abnormal liver function of 26.3% and 15.4% (P<0.05), respectively. Eight patients (14.4%) in CsA group required a drug conversion but none in FK506 group. The drug conversion resulted in significant reduction of ALT/AST level from 255.13+/-31.38/201.88+/-21.25 U/L to 31.25+/-11.50/25.13+/-9.68 U/L (P<0.01). CONCLUSION: For HBV-carrying renal transplant recipients, FK506 as the primary choice of immunosuppressant can be more effective and safer than CsA.