Two new species of Leodamas Kinberg, 1866 (Annelida, Orbiniidae) from China seas

Two species of Leodamas(Annelida,Orbiniidae)from China seas are described based on both material of the Marine Biological Museum(Chinese Academy of Sciences,Qingdao),and newly collected specimens.Leodamas robustus sp.n.is characterized by having uncini arranged in two short rows,anterior row with 3-5 uncini,increasing in size,with uncini on posterior chaetigers thicker,heavier and more curved than those on precedent chaetigers;posterior row with 2-5 uncini,thin and delicate,nearly the same size on all chaetigers,with 2-3 thin capillaries dorsally to two rows of uncini.Leodamas weizhouensis sp.n.is characterized by having delicate pocket-like membrane below and posterior to neuropodia,neuropodia of thoracic chaetigers with fi ve dense rows of uncini.A key to all species of Leodamas from China seas is also provided.

Changes in soil carbon sequestration and soil respiration following afforestation on paddy fields in north subtropical China

Aims Although many studies have reported net gains of soil organic carbon(SOC)after afforestation on croplands,this is uncertain for Chinese paddy rice croplands.Here,we aimed to evaluate the effects of affores-tation of paddy rice croplands on SOC sequestration and soil respiration(R).Such knowledge would improve our understanding of the efctive-ness of various land use options on greenhouse gas mitigation in China.Methods The investigation was conducted on the Chongming Island,north subtropical China.Field sites were reclaimed from coastal salt marshes in the 1960s,and soils were homogeneous with simple land use:histories.SOC stocks and R,levels were monitored over one year in a paddy rice cropland,an evergreen and a deciduous broad-leaved plantation established on previous paddy fields and a reference fal-low land site never cultivated.Laboratory incubation of soil under fast-changing temperatures was used to compare the temperature sensitivity(Q10)of SOC decomposition across land uses.Important Findings After 15-20 years of afforestation on paddy fields,SOC concentra-tion only slightly increased at the depth of 0--5 cm but decreased in deeper layers,which resulted in a net loss of SOC stock in the top 40cm.Seasonal increase of sOC was observed during the rice-growing period in croplands but not in afforested soils,suggest-ing a stronger SOC sequestration by paddy rice cropping.However,SOC sequestered under cropping was more labile,as indicated by its higher contents of dissolved organic carbon and microbial bio-mass.Also,paddy soils had higher annual R,than afforested soils;R,abruptly increased after paddy fields were drained and plowed and remained distinctively high throughout the dry farming period.Laboratory incubation revealed that paddy soils had a much higher Q10 of SOC decomposition than afforested soils.Given that tem-perature was the primary controller of R,in this region,it was con-cluded that despite the stronger SOC sequestration by paddy rice cropping,its SOC was less stable than in afforested systems and might be more easily released into the atmosphere under global warming.

Loss of the accessory chromosome converts a pathogenic tree-root fungus into a mutualistic endophyte

Some fungal accessory chromosomes(ACs)may contribute to virulence in plants.However,the mecha-nisms by which ACs determine specific traits associated with lifestyle transitions along a symbiotic contin-uum are not clear.Here we delineated the genetic divergence in two sympatric but considerably variable isolates(16B and 16W)of the poplar-associated fungus Stagonosporopsis rhizophilae.We identified a-0.6-Mb horizontally acquired AC in 16W that resulted in a mildly parasitic lifestyle in plants.Complete deletion of the AC(D16W)significantly altered the fungal phenotype.Specifically,D16W was morphologically more similar to 16B,showed enhanced melanization,and established beneficial interactions with poplar plants,thereby acting as a dark septate endophyte.RNA sequencing(RNA-seq)analysis showed that AC loss induced the upregulation of genes related to root colonization and biosynthesis of indole acetic acid and melanin.We observed that the AC maintained a more open status of chromatin across the genome,indicating an impressive remodeling of cis-regulatory elements upon AC loss,which potentially enhanced symbiotic effectiveness.We demonstrated that the symbiotic capacities were non-host-specific through comparable experiments on Triticum–and Arabidopsis–fungus associations.Furthermore,the three isolates generated symbiotic interactions with a nonvascular liverwort.In summary,our study suggests that the AC is a suppressor of symbiosis and provides insights into the underlying mechanisms of mutualism with vascular plants in the absence of traits encoded by the AC.We speculate that AC-situ-ated effectors and other potential secreted molecules may have evolved to specifically target vascular plants and promote mild virulence.