Том 58, № 1 (2018)

Eustomias diplomastiga (28° S, 84° W), E. mavka (36° S, 121° W), and E. kukuevi (23° S, 12° E) spp. n. are described from the southern subtropical waters of Atlantic and Pacific oceans. For the species E. diplomastiga sp. n. and E. crucis, a new subgenus Furcostomias subgen. n. is established. It is different from other subgenera based on the following features: stem of the chin barbel bifurcate at the middle, completely deprived of bulbs, with a pigmented shaft but without the external pigmentation of the stem and branches and without the spots associated with the photophores, the presence of a short ventral furrow, P 2, V 7. A review of the diagnostic features of the subgenera of Eustomias is given.

We studied the morphological structure of dorsal scutes in adult individuals of Acipenser ruthenus. We determined the morphometric indices of scutes, the values of which are different in males and females. We created a system for sex identification in sterlets based on indices and criteria indicative of the shape of the first five scutes. The results can be used for developing a method for intravital sex identification in sturgeons at earlier stages of development.

Data on the distribution, size and age structure, and growth of the pike Esox lucius collected in the Rybinsk Reservoir in 1953–2015 were analyzed. The main factors that determine the population size of the pike and dynamics of its structural indices are the intensity of the fishery and changes in the temperature regime of the reservoir. Since the mid-1990s, under the influence of high harvesting load, the population of the pike decreased and its age structure changed toward the predominance of individuals of younger age groups. As a result of climate warming, the water column warming of the Rybinsk Reservoir in the 2000s affected the growth character of large individuals. The ratio of phenotypes with small and high number of vertebrae in the first year depends on the water temperature during embryonic development. Among the large individuals preferring deep-water areas with a lower temperature, approximately 50% have 61–62 vertebrae in the axial skeleton. It is suggested that, with climate warming and the development of pike spawn at a higher temperature, the portion of individuals with a high number of vertebrae may decrease, which will lead to a decrease in the number of recruits of the deep-water part of the population.

The morphology and distribution of taste buds in the outer integument of the body and in the oral cavity of two forms (blind cave and sighted terrestrial ones) of the astyanax Astyanax fasciatus and in intact and blinded individuals of the Buenos Aires tetra Hyphessobrycon anisitsi have been studied using electronic scanning and light microscopy. In sighted individuals of both species, the morphometric parameters of the taste apparatus and the distribution of taste receptors are similar; the taste apparatus in the oral cavity is more developed than in the outer covers. Morphologically different taste zones were found in the oral cavity of characins. In blind fish, the taste apparatus of the maxillary zones is distinguished by smaller taste buds and a greater density of their distribution. The sensory field of taste buds in blind and sighted individuals of astyanax and tetra has a similar ultrastructure; it is formed by taste cells of three types. In blind astyanaxes and blinded individuals of tetra, numerous modified epidermal cells were found for the first time in the epithelium of the taste zones and in contact with taste buds, which are regarded as tactile receptors and a constituent element of polysensory taste-tactile complexes localized in blind fish in mainly ventral sensory zones.

The specificity of the species composition of the ichthyofauna in the Russian and Korean waters in the Sea of Japan/East Sea (northwards from 35°17′N) is considered. The population and the proportion of species from the order of the perch-like fishes (Perciformes) steadily decline from the south towards the north; the proportion of the species from the order of the ray-finned fish (Scorpaeniformes) tends to rise. The northward latitudinal gradient in the family composition variability results in a decrease of their numbers along with a significant increase in the sculpins (Cottidae) and the picklebacks (Stichaeidae) in the species composition. In the southernmost region of the studied water area, the sublittoral species tend to prevail; in all of the others, the elittoral species are predominant. The four northern areas are characterized by a high similarity in the species composition (81.8%); this value is significantly lower (63.1%) in case of their comparison with the more southern areas. The similarity in the ichthyofauna composition between the southernmost area and the other studied water area comprises 44.1%.

New subspecies of Zanclorhynchus spinifer heracleus subsp. nov. from the Ridge of Hercules (Pacific–Antarctic Ridge) is described. The type series of the new subspecies was caught on both large banks of the ridge (Central Bank and the South Bank) at the depths of 170–380 m. The new subspecies differs from the nominative subspecies in the degree of development of the arming, particularly, by the cranial spines and of the dorsal fin. The key to the Zanclorhynchus species and subspecies is developed and presented.

Survival of the progeny obtained from artificial crossing of large parasitic anadromous and small nonparasitic resident European river lampreys Lampetra fluviatilis is analyzed. A high individual survival (~61% on average) up to the stage of prolarvae burrowing into ground confirms the absence of a postzygotic barrier between the lamprey forms. The obtained results are discussed in the framework of two theories: of paired species and of intraspecies diversity.