Lecithaster (Lecithasteridae, Digenea) in the White Sea: an unnoticed guest from the Pacific?

Morphological discrimination of species is problematic in many digenean taxa. Parasites of marine fish from the genus Lecithaster Lühe, 1901 are a good example of this. Our goal was to understand which species of Lecithaster infect fish in the White Sea, and reveal their life cycles. We collected specimens of maritae from nine fish species, analysed their morphology and sequenced 28S ribosomal DNA and internal transcribed spacer 2 (ITS2). Contrary to previous accounts, all of them belong to a single species, Lecithaster salmonis Yamaguti, 1934, which was previously only recorded from the Pacific. Morphologically, our maritae specimens were highly variable, sharing characters of L. salmonis, Lecithaster confusus Odhner, 1905 and Lecithaster gibbosus (Rudolphi, 1802) Lühe, 1901. This variability did not correlate with the moderate differences in ITS2 among the specimens, and neither did the fish host species. Members of the subfamily Salmoninae appear to be the best suited definitive hosts, judging from the intensity rates. The intermediate hosts were also discovered: the first is Cryptonatica affinis (Gmelin, 1791) and the second are planktonic copepods. These lifecycle data from the White Sea are consistent with L. salmonis species identification and with the distribution of this species in the North Pacific. The geographical range of L. salmonis seems to be interrupted, and we discuss possible ways of L. salmonis expansion.

Specialized structures on the border between rhizocephalan parasites and their host's nervous system reveal potential sites for host-parasite interactions.

Rhizocephalan barnacles are a unique group of endoparasitic crustaceans. In their extreme adaptation to endoparasitism, rhizocephalan adults have lost almost all features of their free-living relatives but acquired an outstanding degree of control over the body of their hosts (mostly decapods). The subtle influence exercised by rhizocephalans on the physiology, morphology and behaviour of their hosts is a vivid example of the most intimate host-parasite interactions but their mechanisms are very poorly known. In this study we examined the morphology and the adaptive ultrastructure of the organs invading the nervous system of the host in two rhizocephalan species from the families Peltogastridae, (Peltogaster paguri) and Peltogasterellidae (Peltogasterella gracilis). We found two essentially different types of structures involved in interactions of these two rhizocephalans with the nervous system of their hosts: modified rhizocephalan rootlets lying inside the ganglia and the neural fibres of the host enlacing the trophic rootlets of the parasites. We suggest that both these structures may be highly specialized tools allowing the parasite to interact with the host on the humoral level via neuromediators, hormones, attractants and trophic factors.

[Role of various risk factors in the development and diagnosis of recurrent pain in adolescents--students of cadet corps].

Randomized single-blind case--control study is performed. In total, the cadet corp students with recurrent functional abdominal pain and headaches are examined. The paper shows the role of various risk factors in the occurrence of these states. Diagnostic validity is evaluated. Multifactorial genesis of the studied pathology is proved. The essential role in the formation of the psychological characteristics of personality, neurotic states and autonomic dysfunction is shown. Several constitutional characteristics of the organism were not diagnostically significant.

[Modern concepts and methodology of means, methods of protection, and safety measures for servicemen affected by nonionizing radiation]. / Sovremennye konseptsiia i metodologiia razrabotki sredstv, metodov zashchity i obespecheniia bezopasnosti voennosluzhashchikh pri deistvii neioniziruiushchikh izluchenii.

The given information classifies the protection means and methods containing the known for today and prospective decisions, as well as process elements of development, creation and testing of these means Presented as whole, these protection group comprise all the possible aspects of the service-men safety problem in operation of military equipment objects, being the source of non-ionizing radiation.