First record and spreading of the invasive mosquito Aedes japonicus japonicus (Theobald, 1901) in Croatia.

Aedes (Hulecoeteomyia) japonicus japonicus (Theobald, 1901) has recently established across North America and Central Europe. A 3-year survey was conducted in northwestern Croatian regions from 2013 to 2015 using mosquito ovitraps at possible points of entry and house yards, occasionally complemented by larval collections from cemetery vases. In the first year, the survey investigated the county bordering Slovenia, where the first detection of Ae. j. japonicus had taken place on 28 August 2013. During the next 2 years, Ae. j. japonicus was detected in this area from early May until late October. In 2015, several counties further to the east were included in the survey, leading to the detection of Ae. j. japonicus approximately 100 km eastward from the initially surveyed region. Given a moderate continental climate and homogeneous climatic conditions in this part of Europe, the eastward spread of Ae. j. japonicus can be expected to continue.

PSA-NCAM expression in the teleost optic tectum is related to ecological niche and use of vision in finding food.

In this study, tangential migration and neuronal connectivity organization were analysed in the optic tectum of seven different teleosts through the expression of polysialylated neural cell adhesion molecule (PSA-NCAM) in response to ecological niche and use of vision. Reduced PSA-NCAM expression in rainbow trout Oncorhynchus mykiss optic tectum occurred in efferent layers, while in pike Esox lucius and zebrafish Danio rerio it occurred in afferent and efferent layers. Zander Sander lucioperca and European eel Anguilla anguilla had very low PSA-NCAM expression in all tectal layers except in the stratum marginale. Common carp Cyprinus carpio and wels catfish Silurus glanis had the same intensity of PSA-NCAM expression in all tectal layers. The optic tectum of all studied fishes was also a site of tangential migration with sustained PSA-NCAM and c-series ganglioside expression. Anti-c-series ganglioside immunoreactivity was observed in all tectal layers of all analysed fishes, even in layers where PSA-NCAM expression was reduced. Since the optic tectum is indispensable for visually guided prey capture, stabilization of synaptic contact and decrease of neurogenesis and tangential migration in the visual map are an expected adjustment to ecological niche. The authors hypothesize that this stabilization would probably be achieved by down-regulation of PSA-NCAM rather than c-series of ganglioside.

The arbovirus vector Culex torrentium is more prevalent than Culex pipiens in northern and central Europe.

Two species of arbovirus vector, Culex torrentium and Culex pipiens (Diptera: Culicidae), occur in several European countries, but difficulties in their accurate identification and discrimination have hampered both detailed and large-scale distribution and abundance studies. Using a molecular identification method, we identified to species 2559 larvae of Cx. pipiens/torrentium collected from 138 sites in 13 European countries ranging from Scandinavia to the Mediterranean coast. In addition, samples of 1712 males of Cx. pipiens/torrentium collected at several sites in the Czech Republic were identified to species based on the morphology of their hypopygia. We found that the two species occur together in large areas of Europe, and that Cx. torrentium dominates in northern Europe and Cx. pipiens dominates south of the Alps. The transition in dominance occurs in central Europe, where both species are roughly equally common. There was a strong correlation between the length of the growing season at different sites and occurrences of the two species. As the growing season increases, the proportion and detection of Cx. torrentium decrease, whereas those of Cx. pipiens increase. The present findings have important consequences for the interpretation of the results of studies on major enzootic and link-vectors of mosquito-borne bird-associated viruses (i.e. Sindbis, West Nile and Usutu viruses), especially in central Europe and Scandinavia.

Influence of molting on efficacy of two functionally different larvicides: Bti and temephos.

The sensitivity of the second, third (L3), and fourth (L4) instars of Culex pipiens L. and Ochlerotatus sticticus (Meigen) to two larvicides, temephos and Bacillus thuringiensis variety israelensis (Bti) was tested with and without molting occurring in the experiments. In the first experiment for both tested mosquito species, LC50 values increased from the second to the fourth instar when tested against temephos, whereas for Bti the opposite trend was observed. The highest LC50 value was found for fourth instars of Cx. pipens (0.00405 mg/liter) against temephos and for second instars of Oc. sticticus (0.267 mg/liter) against Bti. The determined LC50 values for the second and third instars of both species decreased with an increased number of molted larvae in the experiments with temephos. For the experiments with Bti molting did not have any significant influence on LC50 values, except a small increase in toxicity during the L3/L4 molt of Oc. sticticus. These findings could help assess and define larviciding, as well as influence the quantity of larvicides needed for an efficient treatment.

Population dynamic of Aedes vexans and Ochlerotatus sticticus in flooded areas of the River Drava in Osijek, Croatia.

Populations of adult mosquitoes occurring in the Osijek area in eastern Croatia were monitored from May 1995 to September 2000 with Centers for Disease Control-style traps baited with dry ice. A total of 106,663 adults was caught, ranging from 0 (several times) to 21,120 in May 1995. The mosquitoes captured represented 18 species. Aedes vexans was the most abundant, followed by Ochlerotatus sticticus. Both of these species have breeding sites in flooded areas in the areas surrounding Osijek. Furthermore, these 2 species comprised 86% of total adult mosquitoes collected. The life cycles of these species and their abundances were positively correlated with water level. The peak occurrence of these species was in late spring to early summer. During 6 years, adult mosquito populations were significantly correlated with the water level of the Drava River.