Vol 10, No 1 (2019)

We studied the relative growth rate of seedlings and aboveground and underground organs, as well as functional traits of leaves and absorbing roots in the invasive species Heracleum sosnowskyi and congeneric native species H. sibiricum. The plants were grown in laboratory conditions and the functional plant traits of 21- and 35-day-old seedlings were analyzed. The relative growth rate (RGR) of H. sosnowskyi differed from that of H. sibiricum by 2.5 times, but the growth of plants in height and in area of leaves was similar. Plant biomass and total leaf area were twice as high in 35-day-old seedlings of invasive species. Structural features of the leaves in 35-day-old H. sosnowskyi seedlings were a lower leaf thickness and a higher leaf density. The invasive species had a lower root mass ratio, but the roots were more branched with a greater ratio of absorbing roots and a better development of the root hairs. As a result, H. sosnowskyi had a higher growth rate of absorbing roots (by 2 times) and a larger absorbing surface in relation to the total root surface. We concluded that the structural and functional traits of the leaves and roots provided a 2 times higher net assimilation rate (NAR) and 2.5 times larger RGR in the invasive species H. sosnowskyi.

The trematode fauna of three species of gobies, round goby, bighead goby, and tubenose goby (Pisces, Gobiidae), has been studied in the middle part of the Saratov Reservoir. Twelve species of digenetic flukes are recorded, two of which (metacercariae Holostephanus cobitidis and Apatemon gracilis) are specific to gobies of the family Gobiidae. Most of the registered parasites are widespread species. The larval forms of worms prevailed in all examined samples of fish. The trematode fauna of the gobies under study is characterized by a significant similarity of the species composition.

The duration of embryonic and larval intracapsular development of Rapana venosa, an invasive species of the Black Sea, was studied under experimental conditions (water temperature of 23°C and salinity of 18‰). The development of embryos and larvae in the egg capsules was described day by day. Larvae hatched from the egg capsules on the 19th–20th day after the eggs were laid. The morphology of egg capsule walls and micropores is described, and photomicrographs of them are presented. The studied features of R. venosa reproductive strategy explain the high adaptive capacity and wide distribution of this species.

The harlequin ladybeetle Harmonia axyridis is a rapidly spreading invasive ladybug species. Parasitoids can be considered in view of the possible use of these organisms for the regulation of H. axyridis population size. The species did not experience considerable parasitoid pressure in the invaded territories during the first years after the beginning of the global invasion in 1996, but the share of parasitoid-infected insects in the invasive populations increased considerably on all continents several years after the invasion started. Data on the biology of all H. axyridis ladybeetle parasitoids known to date are summarized in this study, and the role of these organisms in the regulation of invasive H. axyridis population sizes is described.

The results of studies of the reproductive system in sexually mature pumpkinseed Lepomis gibbosus (Linnaeus, 1758) (Centrarchidae) females during spawning in the Kuchurgan Reservoir (liman), the cooling water body of the Moldavian Regional Power Plant, are presented. Asynchronous development of germ cells in the ovary is characteristic of this invasive species. The females spawn three times in May–July, and the relative gonad weight decreases with each generation, so that the gonadоsomatic index before the second and third spawning is sequentially reduced. This is confirmed by the decrease of the weight of eggs and the relative gonad weight during the formation of the second and third egg cell portions within a specific breeding season. Females with severe impairments of gonad development were identified.

The development of environmentally safe and cost-effective methods for controlling invasive species Sosnowsky’s hogweed (Heracleum sosnowskyi Manden.) is an urgent issue for the European part of Russia. The article presents findings of an experiment on the effect of snow cover removal from the areas occupied by H. sosnowskyi in the early spring period (the beginning of March 2018) in the vicinity of the city of Syktyvkar (Komi Republic, Russia). The snow depth reached 100 cm on the intact plots; the sum of below-zero air temperatures measured at 6 a.m. constituted –448°C, with a minimum of –29.0°C during the experiment. The number of H. sosnowskyi plants of all age groups at the experimental plots (with removed snow cover) was shown to be significantly decreased. The median seedling density (pcs. per square meter) was equal to zero. Most of the surviving plants were located along the sides and in the corners of experimental plots. This can be explained by the higher temperature of soil on the borders of plots with an intact snow cover. The results of the experiment may be used for development of invasive plant eradication technology by removal of the snow cover. This technology can be suitable for kindergartens, schools, hospitals, and water protection zones, where the use of chemical methods of plant control is limited or prohibited. The obtained data set with respect to H. sosnowskyi monitoring is available in the repository of Zenodo.

The mottled plane moth Phyllonorycter platani (Staudinger, 1870) was revealed in the Fomin Botanical Garden (Kyiv, Ukraine) for the first time. It is the northernmost limit (51°31′ of northern latitude) of the distribution of this species of moth in Europe and the territory of the former USSR. According to the Global Taxonomic Database of Gracillariidae (Lepidoptera), the history of phytophages distribution is documented throughout Europe, Middle East, Central Asia (Austria, Bulgaria, Greece, Denmark, Spain, Italy, Canary Islands, Macedonia, Poland, Portugal, Slovakia, Croatia, France, Romania, Tajikistan, Turkey, Turkmenistan, United Kingdom) and North America. It is believed that the area of P. platani (Staudinger, 1870) origin is unknown. Colonization of plane trees by this phitophage to the north and northwest of Europe occurs at an average speed of about 10 km per year. In Ukraine the phytophage was discovered in Kherson region—the Faltz-Fein Biosphere Reserve Askania-Nova in 1998, and in 2012—in Tsyurupinsk, a city located 600 km far from Kiev. In the area of the Botanical Garden, the mottled moth feeds on Platanus × acefolia (Ait.) Willd. and Platanus orientalis L. The density of leaf colonization by phytophages on P. × acerifolia increases—from 3.7 pcs/leaf (2010) to 18.4 pcs/leaf (2016). Under favorable conditions, two generations of moth may appear during the season.