The fish swimming trace Undichna unisulca from the Silurian of Sweden: probably the oldest vertebrate locomotion trace fossil

The fish swimming trace Undichna unisulca is reported from a sandstone block collected from the Upper Silurian (Ludlow) Burgsvik Formation of Gotland, Sweden. It represents the oldest record of a vertebrate trace (apart from coprolites), predating previous finds from the Lower Devonian by at least 10 Ma. A thelodont or acanthodian fish may have produced the sinusoidal trails with the aid of their caudal or anal fins while browsing slowly over the sediment whilst searching for food.     

Wolbachia enhances insect‐specific flavivirus infection in Aedes aegypti mosquitoes

Mosquitoes transmit a diverse group of human flaviviruses including West Nile, dengue, yellow fever, and Zika viruses. Mosquitoes are also naturally infected with insect‐specific flaviviruses (ISFs), a subgroup of the family not capable of infecting vertebrates. Although ISFs are not medically important, they are capable of altering the mosquito's susceptibility to flaviviruses and may alter host fitness. Wolbachia is an endosymbiotic bacterium of insects that when present in mosquitoes limits the replication of co‐infecting pathogens, including flaviviruses. Artificially created Wolbachia‐infected Aedes aegypti mosquitoes are being released into the wild in a series of trials around the globe with the hope of interrupting dengue and Zika virus transmission from mosquitoes to humans. Our work investigated the effect of Wolbachia on ISF infection in wild‐caught Ae. aegypti mosquitoes from field release zones. All field mosquitoes were screened for the presence of ISFs using general degenerate flavivirus primers and their PCR amplicons sequenced. ISFs were found to be common and widely distributed in Ae. aegypti populations. Field mosquitoes consistently had higher ISF infection rates and viral loads compared to laboratory colony material indicating that environmental conditions may modulate ISF infection in Ae. aegypti. Surprisingly, higher ISF infection rates and loads were found in Wolbachia‐infected mosquitoes compared to the Wolbachia‐free mosquitoes. Our findings demonstrate that the symbiont is capable of manipulating the mosquito virome and that Wolbachia‐mediated viral inhibition is not universal for flaviviruses. This may have implications for the Wolbachia‐based DENV control strategy if ISFs confer fitness effects or alter mosquito susceptibility to other flaviviruses.     

Pot casts in the Upper Muschelkalk (Middle Triassic) of Weimar/Thuringia—Composition,microfabrics and diagnesis

Summary A horizon with pot casts (potholes) is described from shallow-marine limestones of thespinosus-zone (‘Discitesschichten’, Upper Muschelkalk) near Weimar/Thuringia. The erosional structures are not developed as sole marks but occur as isolated structures. They differe distinctly in size and composition from pot casts described from the Muschelkalk of Southern Germany. Vertical sedimentary zonation and varying sediment infill in the structures suggest continuous erosion and deposition contemporaneous with the background sedimentation. Deposition may have been caused by oscillatory and unidirectional flows as well as a long period of micrite deposition. Early diagenetic deformations (e.g. dewatering, brecciation, pressure solution) have controlled by a higher continuous water flux inside the pot casts and higher intergranular dispersal pressure.     

Coral-rudist bioconstructions in the Upper Cretaceous Haidach section (Gosau Group; Northern Calcareous Alps, Austria)

Summary In the area of Haidach (Northern Calcareous Alps, Austria), coral-rudist mounds, rudist biostromes, and bioclastic limestones and marls constitute an Upper Cretaceous shelf succession approximately 100 meters thick. The succession is part of the mixed siliciclasticcarbonate Gosau Group that was deposited at the northern margin of the Austroalpine microplate. In its lower part, the carbonate succession at Haidach comprises two stratal packages that each consists, from bottom to top, of a coral-rudist mound capped by a rudist biostrome which, in turn, is overlain by bioclastic limestones and, locally, marls. The coral-rudist mounds consist mainly of floatstones. The coral assemblage is dominated by Fungiina, Astreoina, Heterocoeniina andAgathelia asperella (stylinina). From the rudists, elevators (Vaccinites spp., radiolitids) and recumbents (Plagioptychus) are present. Calcareous sponges, sclerosponges, and octocorals are subordinate. The elevator rudists commonly are small; they settled on branched corals, coral heads, on rudists, and on biolastic debris. The rudists, in turn, provided settlement sites for corals. Predominantly plocoid and thamnasteroid coral growth forms indicate soft substrata and high sedimentation rates. The mounds were episodically smothered by carbonate mud. Many corals and rudists are coated by thick and diverse encrustations that indicate high nutrient level and/or turbid waters. The coral-rudist mounds are capped byVaccinites biostromes up to 5 m thick. The establishment of these biostromes may result from unfavourable environmental conditions for corals, coupled with the potential of the elevator rudists for effective substrate colonization. TheVaccinites biostromes are locally topped by a thin radiolitid biostrome. The biostromes, in turn, are overlain by bioclastic limestones; these are arranged in stratal packages that were deposited from carbonate sand bodies. Approximately midsection, an interval of marls with abundantPhelopteria is present. These marls were deposited in a quiet lagoonal area where meadows of sea grass or algae, coupled with an elevated nutrient level, triggered the mass occurrence ofPhelopteria. The upper part of the Haidach section consists of stratal packages that each is composed of a rudist biostrome overlain by bioclastic wackestones to packstones with diverse smaller benthic foraminifera and calcareous green algae. The biostromes are either built by radiolitids,Vaccinites, andPleurocora, or consist exclusively of radiolitids (mainlyRadiolites). Both the biostromes and the bioclastic limestones were deposited in a low-energy lagoonal environment that was punctuated by high-energy events.In situ-rudist fabrics typically have a matrix of mudstone to rudistclastic wackestone; other biogens (incl. smaller benthic foraminifera) are absent or very rare. The matrix of rudist fabrics that indicate episodic destruction by high-energy events contain a fossil assemblage similar to the vertically associated bioclastic limestones. Substrata colonized by rudists thus were unfavourable at least for smaller benthic foraminifera. The described succession was deposited on a gently inclined shelf segment, where coral-rudist mounds and hippuritid biostromes were separated by a belt of bioclastic sand bodies from a lagoon with radiolitid biostromes. The mounds document that corals and Late Cretaceous elevator rudists may co-occur in close association. On the scale of the entire succession, however, mainly as a result of the wide ecologic range of the rudists relative to corals, the coral-dominated mounds and the rudist biostromes are vertically separated.     

Quantification of Filamentous Actin (F-actin) Puncta in Rat Cortical Neurons

Filamentous actin protein (F-actin) plays a major role in spinogenesis, synaptic plasticity, and synaptic stability. Changes in dendritic F-actin rich structures suggest alterations in synaptic integrity and connectivity. Here we provide a detailed protocol for culturing primary rat cortical neurons, Phalloidin staining for F-actin puncta, and subsequent quantification techniques. First, the frontal cortex of E18 rat embryos are dissociated into low-density cell culture, then the neurons grown in vitro for at least 12-14 days. Following experimental treatment, the cortical neurons are stained with AlexaFluor 488 Phalloidin (to label the dendritic F-actin puncta) and microtubule-associated protein 2 (MAP2; to validate the neuronal cells and dendritic integrity). Finally, specialized software is used to analyze and quantify randomly selected neuronal dendrites. F-actin rich structures are identified on second order dendritic branches (length range 25-75 µm) with continuous MAP2 immunofluorescence. The protocol presented here will be a useful method for investigating changes in dendritic synapse structures subsequent to experimental treatments.     

Deoxyribonucleic Acid Repair in Bacillus subtilis: Development of Competent Cells into a Tester for Carcinogens

The development of competent transformed Bacillus subtilis into a tester system for carcinogens is described. Precocious or noninduced activation of SOS functions occur in competent cells. Thus, lower doses or concentrations of SOS inducing agents are needed to cause cell death due to indigenous prophage activation and lysis of bacteria. The two known defective prophages in B. subtilis enhance the sensitivity of competent cells to the carcinogens ultraviolet light, mitomycin C, and methyl methanesulfonate. However, these same cells have no enhanced sensitivity for the non-carcinogenic ethyl methanesulfonate or for nalidixic acid. Therefore, competent B. subtilis appear to be a sensitive tester for carcinogens.     

A vector representation for amino acid sequences

A scheme for representing amino acids as vectors in the plane is presented and justified. The two dimensions of the plane are size and hydrophobicity. The vector representation is then applied to generate a consensus sequence for some sets of homologous proteins. A figure of merit for the degree of homology of a set of sequences results from the analysis. Some other applications of the scheme are considered also. This work grew from ideaseeds planted by Margaret Dayhoff's work in theAtlas of Protein Structure and Sequence. It is with gratitude that I dedicate this paper to her memory.     

Requirement of chelating compounds for the growth of Corynebacterium glutamicum in synthetic media

Summary The effects of various iron-complexing substances on the growth of Corynebacterium glutamicum in synthetic medium were investigated. The data obtained indicate that C. glutamicum has an absolute requirement for the presence of an iron-complexing compound as a growth factor for rapid and abundabnt growth in synthetic media. This requirement can be met by adding low concentrations (10^–5 M) of certain dihydroxyphenols (catechol, protocatechuate) or relatively high concentratuions (0.1%) of citrate to the medium or by autoclaving a small amount of glucose together with other media components. The addition of catechol or protocatechuate to synthetic media has advantages over media preparation with citrate or autoclaved glucose. In the described synthetic broth supplemented with catechol or protocatechuate growth is largely independent of the iron content of the medium in a range between 0.037 and 0.37 mM.Offprint requests to: W. Liebl     

Age‐dependent dispersal and habitat choice in black‐tailed godwits Limosa limosa limosa across a mosaic of traditional and modern grassland habitats

Whether to disperse, and where to, are two of the most prominent decisions in an individual's life, with major consequences for reproductive success. We studied natal and breeding dispersal in the monogamous black‐tailed godwit Limosa limosa limosa in the Netherlands, where they breed in agricultural grasslands. The majority of these grasslands recently changed from wet herb‐rich meadows into well‐drained grassland monocultures, on which godwits have a lower reproductive success. Here we examine habitat selection with a multistate mark–recapture analysis. Habitat transition probabilities between meadows and monocultures were estimated on the basis of 1810 marked chicks and 531 adults during seven years in a 8500 ha study area. Young and adult godwits may differ in habitat selection because: 1) adults may have gained experience from previous nest success where to settle, 2) younger individuals may find it harder to compete for the best territories. Both young and adults moved at a higher rate from the predominant monocultures to meadows than the other way around, thus actively selecting the habitat with better quality. However, dispersal distance of adults was not affected by previous nest success. The average dispersal distance from place of birth of godwits breeding for the first time was ten times larger than that of adult godwits. That godwits breeding in their second calendar year arrived and laid at similar dates and were equally able to select territories in areas with high breeding densities, suggests that young birds were not competitively inferior to adults. Although on monocultures reproduction is insufficient to maintain constant populations, birds sometimes moved from meadows to monocultures. This explains why even after 30 years of land‐use intensification, godwits still breed in low‐quality habitat. The adjustment to changing habitat conditions at the population level appears to be a slow process.