Tube structure and original composition of Sinotubulites: shelly fossils from the late Neoproterozoic in southern Shaanxi, China

Abundant well-preserved shelly fossils of Sinotubulites occur in the upper part of the late Neoproterozoic Dengying Formation in Ningqiang County, Shaanxi Province, China. Unlike 'funnel-in-funnel' structures of co-occurring Cloudina shells, the tube of Sinotubulites is nearly cylindrical, composed of several thin layers and characterized by 'tube-in-tube' structure. The tube bears prominent longitudinal sculptures and/or irregular annulations, which were formed by the wrinkles of tube layers, and weaken gradually towards the inner layers. The irregular wrinkle ornament of the outer layer shows plastic feature of the Sinotubulites tubes, which may further imply that the organisms secrete the elastic and flexible organic-dominated walls with mineralization, possibly aragonitic. Detailed thin section and SEM studies indicate that the silicification occurred earlier than phosphatation. Specimens preserved in situ from Hubei and surface ornamentation and polygonal shape of the cross-section suggest that Sinotubulites probably lived as an epibenthos lying on the sea floor.     Aragonitic tube, Ediacaran, Shaanxi. China, Sinotubulites , tube structure.     

Trap‐jaws revisited: the mandible mechanism of the ant Acanthognathus

Abstract.Ants of the genus Acanthognathus stalk small insects and catch their prey by a strike with their long, thin mandibles. The mandibles close in less than 2.5 ms and this movement is controlled by a specialized closer muscle. In Acanthognathus , unlike other insects, the mandible closer muscle is subdivided into two distinct parts: as in a catapult, a large slow closer muscle contracts in advance and provides the power for the strike while the mandibles are locked open. When the prey touches specialized trigger hairs, a small fast closer muscle rapidly unlocks the mandibles and thus releases the strike. The fast movement is steadied by large specialized surfaces in the mandible joint and the sensory‐motor reflex is controlled by neurones with particularly large, and thus fast‐conducting, axons.     

No relationship between canalization and developmental stability of the skull in a natural population of Mastomys natalensis (Rodentia: Muridae)

The aim of the present work was to investigate the relationship between canalization and developmental stability under varying environmental conditions. Three different cohorts of Mastomys natalensis (Rodentia, Muridae), displaying different growth trajectories, were analysed by means of geometric morphometrics. A set of 23 landmarks was digitalized on the dorsal skull of 292 specimens from Morogoro (Tanzania). Patterns of among‐ and within‐individual (measured as fluctuating asymmetry, FA) variation were assessed and compared among and within the three groups to test for the presence of a common mechanism between canalization and developmental stability. Results showed that there was no congruence between canalization and developmental stability: (1) levels of FA and among‐individual variation varied in a discordant fashion, (2) no correspondence between the variance–covariance matrix of among‐ and within individual variation was found, and (3) environmental effects were able to alter the covariance structure of among‐individual variation leaving patterns associated with fluctuating asymmetry unaffected. These findings support the view of multiple mechanisms underlying developmental buffering of shape variation. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 207–216.     

Jasmonic acid signalling mediates resistance of the wild tobacco Nicotiana attenuata to its native Fusarium,but not Alternaria,fungal pathogens

We recently characterized a highly dynamic fungal disease outbreak in native populations of Nicotiana attenuata in the southwestern United States. Here, we explore how phytohormone signalling contributes to the observed disease dynamics. Single inoculation with three native Fusarium and Alternaria fungal pathogens, isolated from diseased plants growing in native populations, resulted in disease symptoms characteristic for each pathogen species. While Alternaria sp.‐infected plants displayed fewer symptoms and recovered, Fusarium spp.‐infected plants became chlorotic and frequently spontaneously wilted. Jasmonic acid (JA) and salicylic acid (SA) levels were differentially induced after Fusarium or Alternaria infection. Transgenic N. attenuata lines silenced in JA production or JA conjugation to isoleucine (JA‐Ile), but not in JA perception, were highly susceptible to infection by F. brachygibbosum Utah 4, indicating that products derived from the JA‐Ile biosynthetic pathway, but not their perception, is associated with increased Fusarium resistance. Infection assays using ov‐nahG plants which were silenced in pathogen‐induced SA accumulations revealed that SA may increase N. attenuata's resistance to Fusarium infection but not to Alternaria. Taken together, we propose that the dynamics of fungal disease symptoms among plants in native populations may be explained by a complex interplay of phytohormone responses to attack by multiple pathogens.     

Occurrence of Beta-Lactamases in Colistin-Resistant Enterobacterales Strains in Poland – a Pilot Study

Sixty-five colistin-resistant Enterobacterales isolates recovered from different clinical specimens were analyzed. The strains were collected in 12 hospitals all over Poland within a period of nine months. Strains were analyzed for eight genes from the mcr family. The presence of mcr-1 gene was detected in three Escherichia coli strains. The 45/65 isolates were identified as ESBL producers. CTX-M-1-like enzymes were the most common ESBLs (n = 40). One E. coli and seven Klebsiella pneumoniae strains produced carbapenemases, with the NDM being produced by five isolates. Among all the strains tested, four and five were resistant to new drugs meropenem/vaborbactam and ceftazidime/avibactam, respectively.