Repellency of deet and SS220 applied to skin involves olfactory sensing by two species of ticks

Responses of host-seeking nymphs of the blacklegged tick, Ixodes scapularis Say and lone star tick, Amblyomma americanum (Linnaeus) (Acari: Ixodidae) to the repellents N,N-diethyl-3-methylbenzamide (deet) and (1S, 2'S)-2-methylpiperidinyl-3-cyclohexene-1-carboxamide (SS220) were studied using fingertip laboratory bioassays. Ethanol solutions of both compounds applied to the skin strongly repelled both species of ticks at 0.8 and 1.6 micromole of compound/cm2 skin. The ticks were also repelled when two layers of organdie cloth covered the portion of a finger treated with either deet or SS220. Gas chromatographic analyses of the outer layer of cloth that had covered skin treated with 1.6 micromole compound/cm2 skin revealed only 0.1 nmole SS220/cm2 cloth and 2.8 nmole deet/cm2 cloth. However, in bioassays in which a single layer of cloth was treated with a dose of deet or SS220 equivalent to the amount found in the outer layer of cloth, ticks were not repelled. Results unequivocally demonstrated that these ticks responded to the repellents in the vapour phase when repellent treated skin was covered with cloth to obviate tactile contact with them, and made it clear that the ticks detect the repellents by olfactory sensing. Heretofore, the mode of action of deet and SS220 was unclear.     

Autotomy reduces feeding, energy storage and growth of the sea star Stichaster striatus

We evaluated the effect of autotomy on feeding, energy storage and growth of juvenile Stichaster striatus kept in the laboratory for five months with a limited supply of the mussel Semimytilus algosus. Autotomy strongly decreased feeding, energy storage and growth. Intact juveniles showed a ∼ 3 fold higher feeding rate than autotomized individuals throughout the experiment. Intact juveniles also had a higher (∼ 5 fold) energy content per pyloric caeca in each arm. This was mainly due to higher lipid content, the main proximate constituent of pyloric caeca. Intact juveniles showed a greater growth rate and reached a greater size than autotomized individuals, more evident for underwater mass than radius length. The reduced capacity to feed reduced energy intake in autotomized individuals. However, low energy reserves along with low growth in autotomized sea stars, support the hypothesis that juveniles of this species allocate energy to regeneration to the detriment of growth. This was also supported by the ∼ 25% of arm length regeneration after 5 mo. Remaining small could increase risk of lethal predation, however, S. striatus may reduce predation risk by using crevices and kelp holdfasts as refuges from predators. Given the strong impact of autotomy on feeding, regeneration of arms to recover full capacity to forage and grow seems a better strategy for juvenile S. striatus, than merely growing.     

Multilocus genetic analyses differentiate between widespread and spatially restricted cryptic species in a model ascidian

Elucidating the factors that shape species distributions has long been a fundamental goal in ecology and evolutionary biology. In spite of significant theoretical advancements, empirical studies of range limits have lagged behind. Specifically, little is known about how the attributes that allow species to expand their ranges and become widespread vary across phylogenies. Here, we studied the ascidian Botryllus schlosseri, a worldwide invasive species that is also characterized by marked genetic subdivision. Our study includes phylogenetic and population genetic data based on mitochondrial and nuclear genes, as well as polymorphic microsatellites for B. schlosseri colonies sampled from the southern and northern coasts of Europe and the eastern and western coasts of North America. We demonstrate that this well-known model organism comprises three highly divergent and probably reproductively isolated cryptic species (A, D and E), with two more (B and C) being suggested by data retrieved from GenBank. Among these, species A, recovered in all of the surveyed regions, is by far the most common and widespread. By contrast, species B-E, occurring mostly in sites from northern Europe, are considerably more geographically restricted. These findings, along with inferences made on transport opportunity, suggest that divergent evolutionary histories promoted differences in invasive potential between B. schlosseri sibling species, indicating that attributes that facilitate dramatic shifts in range limits can evolve more easily and frequently than previously thought. We propose environmental disturbance as a selective force that could have shaped the evolution of invasiveness in the B. schlosseri complex.     

Astronomical Sources of Circularly Polarized Light and the Origin of Homochirality

Possible astronomical sources of ultraviolet circularly polarized light(UVCPL) which might be responsible for enantiomeric selection in interstellarorganic molecules are considered, Synchrotron radiation from magnetic neutronstars has been suggested as a possible source of UVCPL. However, synchrotronradiation in these situations is not predicted to be strongly circularlypolarized. Very few such sources show optical synchrotron radiation and in thefew that do circular polarization has not been observed. Magnetic white dwarfsand white dwarf binaries (Polars) can be highly circularly polarized but anyeffect on molecular clouds and star formation regions must rely on rare chance encounters. Recent observations show that substantial levels of circularpolarization are present in reflection nebulae in star formation regions. Thismechanism produces polarized light exactly when and where it is needed inregions where star formation is occurring and organic molecules are known to be present.     

Maximum Number of Habitable Planets at the Time of Earth's Origin: New Hints for Panspermia?

New discoveries have fuelled the ongoing discussion of panspermia, i.e. the transport of life from one planet to another within the solar system (interplanetary panspermia) or even between different planetary systems (interstellar panspermia). The main factor for the probability of interstellar panspermia is the average density of stellar systems containing habitable planets. The combination of recent results for the formation rate of Earth-like planets with our estimations of extrasolar habitable zones allows us to determine the number of habitable planets in the Milky Way over cosmological time scales. We find that there was a maximum number of habitable planets around the time of Earth's origin. If at all, interstellar panspermia was most probable at that time and may have kick-started life on our planet.     

Parasitism of Leptasterias spp. (Echinodermata: Asteroidea) by the ciliated protozoan Orchitophrya stellarum (Scuticociliata)

Abstract. The parasitic ciliate Orchitophrya stellarum was found in the testes of brooding, winter-spawning Leptasterias spp. from San Juan Island, Washington, but not in the testes of Leptasterias spp. from the Lynn Canal, Alaska. Dense populations of the ciliate were localized within the fuller areas of testes, where sperm counts were significantly reduced. The ciliates were loaded with phagosomes, some of which contained sperms in various stages of digestion. Leptasterias spp. are not as severely impacted by this ciliated protozoan parasite as Pisaster ochraceus. Leptasterias spp. may serve as seasonal hosts for O. stellarum ; this ciliate lives in seawater and in ripe males of winter-brooding and spring-summer broadcasting sea stars. The wet weight of parasitized and non-parasitized males did not differ. The sex ratio did not deviate from the expected (1:1) in any population except at Point Louisa, Alaska, where males outnumbered females. Testis indexes of parasitized males from 2 of the 4 locations on San Juan Island, Washington were significantly reduced relative to non-parasitized males, indicating a loss of sperm output during spawning.     

Altered lower extremity joint mechanics occur during the star excursion balance test and single leg hop after ACL-reconstruction in a collegiate athlete

The effects of ACL-reconstruction on lower extremity joint mechanics during performance of the Star Excursion Balance Test (SEBT) and Single Leg Hop (SLH) are limited. The purpose of this study was to determine if altered lower extremity mechanics occur during the SEBT and SLH after ACL-reconstruction. One female Division I collegiate athlete performed the SEBT and SLH tasks, bilaterally, both before ACL injury and 27 months after ACL-reconstruction. Maximal reach, hop distances, lower extremity joint kinematics and moments were compared between both time points. Musculoskeletal simulations were used to assess muscle force production during the SEBT and SLH at both time points. Compared to the pre-injury time point, SEBT reach distances were similar in both limbs after ACL-reconstruction except for the max anterior reach distance in the ipsilateral limb. The athlete demonstrated similar hop distances, bilaterally, after ACL-reconstruction compared to the pre-injury time point. Despite normal functional performance during the SEBT and SLH, the athlete exhibited altered lower extremity joint mechanics during both of these tasks. These results suggest that measuring the maximal reach and hop distances for these tasks, in combination with an analysis of the lower extremity joint mechanics that occur after ACL-reconstruction, may help clinicians and researchers to better understand the effects of ACL-reconstruction on the neuromuscular system during the SEBT and SLH.     

National standards: Reasserting the ecological restoration framework in uncertain times

National ecological restoration standards – produced in 2016 through the collaboration of 13 of Australia's leading ecological restoration organisations – are increasingly influencing practitioners. This paper elucidates two of the Key Principles that underpin standards to encourage highest and best efforts across all sectors and help resolve uncertainty about the role of restoration in a changing world.     

Seasonality and 3D‐visualization of brooding in the hermaphroditic ophiuroid Amphiura capensis

This article describes the reproductive biology and developing young of Amphiura capensis, a small brooding brittle star found in the intertidal zones of Namibia and South Africa. Each month from October 2014 to September 2015, 20 specimens were collected from Mouille Point, Cape Town, South Africa, and dissected for internal examination of brooding characteristics. Disc diameters of 238 analyzed adults ranged 2.5–8.7 mm, with a mean of 6.15 mm (SD = 1.10 mm). Brooding was exhibited in 60.5% of all sampled individuals, of which 30.6% contained young of only one of six subjectively chosen size classes, 31.9% contained two size classes, and the rest (37.5%) contained more than two size classes at the same time. Young within the same bursa were commonly of the same size class, which suggests sequential brooding. However, multiple size classes of young were often present within different bursae of the same parent, which thus exhibited characteristics of both sequential and simultaneous brooding. Of 584 brooded young retrieved from dissections, an average of 2.5 (SD = 3.2) and a maximum of 14 young were recorded within a single parent. As no larval stages were observed, development was assumed to be direct. Three‐dimensional visualizations of μCT scans revealed the positions of the brooded young to be quite different from those in other species, facing with their mouths downwards instead of upwards, and not all pressed against the adult's bursal wall. Brooding occurred throughout the year, but numbers of young peaked in austral winter, coinciding with warmer water temperatures at this site. The duration of brooded development was estimated to be ~6 months, comparable with other species with similar reproductive biology.     

Heat shock-induced relaxation of restriction enzyme specificity inEscherichia coli

Methylated and hydroxymethylated cytosine containing DNA was restricted by proteins encoded by themcrBC (rglB) loci ofE. coli. In vivo, RglB proteins recognize and cleave hmCT2 and hmCT4 DNAs at 30°C and 42°C but hmCT6 DNA was unaffected at both temperatures, However, cells carrying therglB genes cloned on pBR322 (pDSS17) did not restrict hmCT6 at 30°C, but hmCT6 DNA was cleaved efficiently at 42°C. Heat shock treatment for five minutes was enough to induce this promiscuity in recognition specificity. We call this activity RglB star. A single copy ofrglB located on the chromosome or cloned on a low copy vector pMU575 failed to show RglB star activity.De novo protein synthesis was not required for the manifestation of RglB star activity.