ON DISTRTBUTION PATTERN OF AMORPHA FRUTICOSA L. IN THE REGION OF KANEVSKAYA HYDROPOWER STATION (UKRAINE) IN CONNECTION WITH HYDROCHORY

Amorpha fruticosa L. is a kenophyte of North American origin, ergaziophyte. Currently, this species naturalized over large areas and became the background on the coast waters of the Dnieper reservoirs of hydropower stations. It is necessary to clarify the reasons for the distribution of A. fruticosa populations in different parts of the Middle Dnieper coast under conditions of artificial regulation of its water yield. It has been proven that the high buoyancy of A. fruticosa fruits provides the possibility of its active dispersal along river beds in a natural way under conditions of fluctuations in the level of surface water yield right in spring floods. The main and determining factor in the active dissemination of the species on the coast of the Kanev and Kremenchug reservoirs is the frequent variability of the maximum water surface level. The narrow altitudinal range of distribution of this species on the coast in the lower parts, and accordingly, wider in the upper parts of the reservoirs is determined by the corresponding indicators of water level differences. The possibility of artificial regulation of the water surface level with knowledge of the characteristics of hydrochory of this invasive species makes it possible to influence its distribution in the territory near the reservoirs.

FEATURES OF THE SPATIAL DISTRIBUTION OF INVASIVE SPECIES OF AMPHIPODS IN THE LITTORAL OF LAKE LADOGA

The modern distribution of invasive amphipods of Baikal ( Gmelinoides fasciatus (Stebbing, 1899) , Micruropus possolskii Sowinsky, 1915) and Ponto-Caspian origin ( Pontogammarus robustoides Sars, 1894 , Chelicorophium curvispinum (Sars, 1895)) in Lake Ladoga was shown. The heterogeneity of the distribution of quantitative indicators of amphipods in different parts of the lake was established. The most widespread species in the littoral zone was G. fasciatus . A decrease in the contribution of G. fasciatus in the bottom communities of macrozoobenthos was noted. The dominant role of G. fasciatus was observed only in those parts of the lake where other species of invasive amphipods did not penetrated yet. The habitat of Ponto-Caspian amphipods is limited by the boundaries of the Volkhov Bay. A significant increase in the quantitative development of P. robustoides and active dispersal of M. possolskii to the South along the west coast of the lake indicate the ongoing structural restructuring of littoral biocenoses.

Self-propelling and rolling of a sessile-motile aggregate of the bacterium Caulobacter crescentus

Active dispersal of microorganisms is often attributed to the cells’ motile organelles. However, much less is known about whether sessile cells can access such motility through aggregation with motile counterparts. Here, we show that the rosette aggregates of the bacterium Caulobacter crescentus, although predominantly sessile, can actively disperse through the flagellar motors of motile members. Comparisons in kinematics between the motile rosettes and solitary swimming cells indicate that the rosettes can be powered by as few as a single motor. We further reconstructed the 3D movements of the rosettes to reveal that their proximity to a solid-liquid interface promotes a wheel-like rolling, as powered by the flagellar torque. This rolling movement also features a sequence of sharp turns, a reorientation mechanism distinct from that of swimming cells. Overall, our study elucidates an unexplored regime of aggregation-based motility that can be widely applied to sessile-motile composites.

Movement Behavior of the Pine Needle Gall Midge (Diptera: Cecidomyiidae)

The movement behavior of the pine needle gall midge (Thecodiplosis japonensis Uchida Et Inouye (Diptera: Cecidomyiidae)), an invasive species in China, was determined by using a tethered flight technique and digital videography in the laboratory. The flight distance, duration, and speed of females were compared at different ages (2–10 h) and ambient temperatures (17, 21, 26, and 30°C). Female flight distance and duration at 26°C were significantly greater than those at 17°C and 21°C. The age of T. japonensis did not significantly affect the three flight characteristics. For females at 2–10 h of age at 26°C and 70% RH, the maximum flight distance was 667.59 m; the longest flight time was 6,222.34 s; and the fastest flight speed was 0.44 m·s−1. For larvae wetted with water, the highest jump was 5.7 cm; the longest jump was 9.6 cm; and the greatest distance moved in 5 min was 27.13 cm, which showed that the active dispersal potential of larvae was very low.

Lagrangian modeling of the active dispersal of juvenile leatherback turtles in the North Atlantic Ocean

<p>It has long been assumed that young sea turtles drift passively with ocean currents. As a consequence, simple Lagrangian models have often been used to investigate the dispersal of various sea turtle populations during their juvenile stage. However, evidence is growing that juvenile sea turtles do not drift purely passively with ocean currents but also display some swimming activity, generally directed towards favorable habitats.</p><p>We have thus developed a new Sea Turtle Active Movement Model (STAMM) in which simulated individuals disperse under the combined influence of oceanic currents and swimming movements triggered by the need to find suitable habitats, that is areas with suitable water temperatures and sufficient food.  Preferred temperatures and food requirements are modeled to vary with the age (or size) of the simulated individuals.</p><p>STAMM is used here to investigate the active dispersal of juvenile leatherback turtles (Dermochelys coriacea) born in French Guiana, a major rookery for the Northwest Atlantic population. Our simulations reveal that:</p><ol><li> While currents broadly shape the dispersal area, habitat-driven movements profoundly structure the spatio-temporal distribution of juveniles within this area. Passive turtles can drift far North in deadly cold waters or concentrate in oligotrophic waters found at the center of the North Atlantic subtropical gyre. On the contrary, actively swimming juveniles tend to concentrate in favorable habitats along the northern boundary of the subtropical gyre and undertake seasonal north-south migrations allowing them to remain in suitable water temperatures.</li> <li>Active juveniles ultimately target rich areas of the Eastern Atlantic basin, in particular in the Bay of Biscay, off Galicia, Portugal and Mauritania, and in the western Mediterranean Sea where juvenile leatherbacks are actually observed. These zones are inaccessible to passive turtles.</li> <li>Arrival times of the active juveniles in these favorable zones are consistent with the observed sizes of individuals bycaught or stranded in these areas;</li> </ol><p>All together these results suggest that active habitat-driven swimming movements shall be systematically taken into account to produce realistic simulations of the spatial distribution of sea turtles during their pelagic juvenile stage. This is much needed to help develop effective conservation measures targeting this critical life stage.</p>

Active dispersal of Aedes albopictus: a mark-release-recapture study using self-marking units

Background Understanding the dispersal dynamics of invasive mosquito species is fundamental to improve vector surveillance and to target control efforts. Aedes albopictus has been deemed a poor flyer as its range of active dispersal is generally assumed to be limited to a few hundred metres, while laboratory studies suggest this mosquito could actually fly several kilometres. The discrepancy may be due to differences in the local environment or to the methodological approach. In Switzerland, Ae. albopictus has been present since 2003 and has since then expanded its range. While passive dispersal is a key driver, it remains unclear how far this mosquito spreads through active flight and what the age structure and size of the local population are, all important parameters for vector surveillance and control. Method We investigated the active dispersal, daily survival rate and population size of Ae. albopictus in mark-release-recapture studies in Coldrerio and Lugano, two areas of intensive control in Switzerland. To mark mosquitoes emerging from breeding sites, we used self-marking units with fluorescent pigment that have minimal impact on mosquito survival and behaviour. We recaptured the adult mosquitoes with BG-Sentinel traps within a radius of 1 km from the marking units over 22 consecutive days. Results We found that 77.5% of the recaptured Ae. albopictus individuals flew further than 250 m, the limit that is usually deemed sufficient for vector containment. The average age of females and males was 8.6 days and 7.8 days in Coldrerio and Lugano, respectively, while the estimated mosquito population densities were 134 mosquitoes/ha in Coldrerio and 767 mosquitoes/ha in Lugano. Conclusions Self-marking units are an effective tool to mark wild mosquitoes. Using this approach, we found that mosquitoes survive long enough to potentially transmit arboviral disease in our study area and that host-seeking Ae. albopictus females may travel further than previously assumed for European mosquito populations. This finding has direct implications for vector control as emergency treatments around positive cases, as well as surveillance and control around detections of new infestations, might need to be extended beyond the usual recommended range of just a few hundred metres.