Light and temperature — interaction of factors determining the intensity of emergence of cercariae of Himasthla elongata (Digenea, Himasthlidae). P. 457-465.
Joint impact of fractional temperature range and three values of light intensity on the emergence of cercariae of Himasthla elongata from intertidal molluscs Littorina littorea from the White Sea was studied experimentally. Temperature optimum of cercarial emergence was found to be in the range of 18—20 °C (18 °C < topt < 20 °C), which overlaps the average range of water temperatures at the intertidal in the study area. If the water temperature was higher than 14°C, light stimulated cercarial emergence, but at 20°C and at 22°C (the extreme temperature value tested) the intensity of cercarial emergence was lower when light intensity was higher. The obtained data are discussed in light of a possible influence of climate warming on the digenean transmission. We hypothesise that an increase in summer water temperature in northern seas and the transition of its values into the range supraoptimal for cercarial emergence from infected snails would not result in any noticeable intensification of trematode transmission.
Diagnostics of the stages of post-embryonic development in Bursaphelenchus ulmophilus (Nematoda: Aphelenchoididae). P. 466-480.
The research was aimed to study diagnostic characters distinguishing individual development stages of Bursaphelenchus ulmophilus (Hofmanni group), which propagative generation worms were multiplied in sterile laboratory cultures of the fungus Botrytis cinerea. J2 hatched after the first molt in the egg shell. Postembryonic stages of individual development include 4 stages (J2—J4 and adults) separated by molts. Juvenile stages differ in structure and size of the genital primordium. The genital primordium of J2 consists of 2 large germinal cells and two apical somatic cells; the presence of 2 germinal cells indicates the didelphic female genital tube of the Bursaphelenchus ancestor. During the following development, both germinal cells shift into the anterior genital tube, because Bursaphelenchus spp. females possess an unpaired genital system with a single anterior branch and anterior ovary. A sex in juveniles may be identified from the J3 stage. In J4, sections of the forming genital system are recognizable. A key to developmental stages of B. ulmophilus is given. The body length growth exceeds pharynx growth. The juvenile body increases during molts and within each stage. Comparing to the earlier development, the growth accelerates between stages J3 and J4; in the same development phase, the most active cellular differentiation and elongation of the genital primordium take place. The B. ulmophilus dauers taken from the Scolytus spp. beetle under-elytra spaces are identical to the third juvenile stage of the propagative generation, whereas in B. mucronatus dauers (the species of Xylophilus group) are the fourth juvenile stage (J4D). Differences between species are also visible in the absence of the mucro on the tail tip in adults and juveniles of B. ulmophilus, whereas a mucro is present in B. mucronatus in juveniles of J3 and J4 stages and in females.
Finding of the metacercariae Stephanoprora polycestis (Trematoda: Echinostomatidae) on gills of the big-scale sans smelt Atherina boyeri in the Black Sea. P. 481-489.
Metacercariae of the trematode Stephanoprora polycestus (Dietz, 1909) were found on gills of еру big-scale sand smelt Atherina boyeri caught in the Black Sea, near Sevastopol, Crimea. Maritae were experimentally obtained as the result of the artificial infection of chickens with found metacercariae. Descriptions of metacercariae and maritae are presented. A differential diagnosis of the found trematodes is provided. Atherina boyeri is recorded for the first time as the second intermediate host of S. polycestus.
Investigation of the copper content in tissues of the mollusk Planorbarius corneus and influence of the trematode infection on the phenoloxidase activity of the haemolymph. P. 490-498.
The dynamics of the accumulation of copper ions by the tissues of the pulmonary mollusk Planorbarius corneus has been studied. The dependence of the copper concentration in tissues of non-infected and trematode-infected mollusks on its concentration in the environment has been analyzed. Regardless of the copper concentration in water, trematode-infected mollusks have an increased level of phenoloxidase activity in hemolymph. In the experiment it was shown that silver — an isoelectronic double of copper — is capable to enter and accumulate by different ways in various tissues and organs of P. corneus. The highest concentration of silver is found in the hepatopancreas. At the same time, the concentration of copper in tissues, with the exception of the hemolymph, decreases. After the abolition of the Ag-medium, the excretion of silver begins, and the concentration of copper in tissues is restored to control values. As the result of research, done on mollusks of natural populations, the following patterns have been found. Regardless of the copper concentration in the environment, its concentration in the hemolymph is maintained at a constantly low level. There is also a correlation between the copper content in the hemolymph and the trematode infection of mollusks. The activity of the hemolymph tyrosinase does not depend on the copper concentration in water, but is significantly higher in infected mollusks. The observed strict control of copper entering to the hemolymph indicates the existence of specialized transport routes for the copper transfer and control of the production of copper-containing enzymes, in the hemolymph phenoloxidase particularly. A direct correlation between the copper concentration in the environment and its concentration in the hepatopancreas of P. corneus has been found.
The ways of origin of the northern palaearctic bloodsucking insects' fauna on the example of fleas (Siphonaptera), mosquitoes (Diptera: Culicidae) and black flies (Diptera: Simuliidae). P. 499-516.
The territory of Fennoscandia and northwestern European Russia were released from glacier cover in the upper Pleistocene and had been again settled by bloodsucking insects during the last 11 thousand years. The sources of the formation of the North Palaearctic fauna of such groups of bloodsucking insects as fleas (Siphonaptera), mosquitoes (Culicidae) and black flies (Simuliidae) were different in the post-glacial period. One of them was the fauna of the ancient Mediterranean and southern Europe, others were the faunas of northeastern China and Primorye. The latter two, in their turn, are closely related with palaeo-faunistic centers of Eastern Asiatic subregion of the Palaearctic and Indomalayan realms. Besides, some species and genera of fleas, mosquitoes, and black flies were spreading from the western American subregion of the Nearctic through Beringia.
Patterns of the formation of the flea fauna (Siphonaptera) — parsites of mammals in the Stavropol Plateau and adjacent territories. P. 517-527.
Stavropol Plateau is situated in the central part of Ciscsaucasia. In this area, 56 species of 27 flea genera parasitizing 65 mammals of 33 genera were found. They are represented by species having wide distribution in the Caucasian Isthmus and also in eastern Mediterranean. Three periods in flea fauna formation in the Stavropol Plateau can be distinguished. The first occurred in Pliocene, when southern European forest species appeared. Besides, species with ranges covering Middle East, Asia Minor, and Turan Lowland appeared in this regional fauna. Later, in the Pleistocene and Holocene, other mesophilic species from Southern Europe, together with European-Asiatic steppe and Turanian semi-desert species penetrated into the Caucasian Isthmus. By peculiarities of the distribution in the examined territory, several groups of flea species can be distinguished: widespread flea species; species spread mainly in the forest-steppe zone; fleas species spread in the forest-steppe and steppe zones; fleas of steppe and semi-desert landscapes; and fleas of semi-desert landscapes.
The tick Ixodes kaiseri (Acari, Ixodidae) in the North Caucasus and Transcaucasia according to the material of the collection of the Stavropol anti-plague institute. P. 528-533.
To date, the North Caucasus, particularly the territory of the Stavropol Territory is traditionally indicated as the habitat of the tick Ixodes crenulatus Koch, 1844. I. kaiseri Arthur, 1957 was previously known only from a single site in the Eastern Ciscaucasia. Re-examination of collections from the North Caucasus and Transcaucasia showed that the overwhelming majority of specimens from these regions belong to the species I. kaiseri, allowing the revision of common views on the range boundaries of both species.
The first record of a chigger mite of the genus Neotrombicula (Acariformes: Trombiculidae) in the northwest of European Russia. P. 534-539.
A chigger mite species, Neotrombicula absoluta Schluger, 1966, which was previously known only from its type locality in Transcarpathian Region of Ukraine, has been found in the vicinities of Kurgolovo Village (Kingisepp District, Leningrad Province, Russia). A single specimen of this species has been collected from the common shrew Sorex araneus L. It is the first record of the genus Neotrombicula (which includes the most usual causative agents of trombiculiasis of humans and domestic animals in Europe) in the northwestern part of European Russia.
Index. P. 540-543.