M. Yu. Pichugin

Development of skeleton elements in juvenile dwarf and small sympatric forms of Salvelinus alpinus complex from Lake Davatchan (Transbaikalia)

The development of skeleton elements was studied in prolarvae, larvae, and fry of two morphologically different forms of the Arctic char Salvelinus alpinus complex—small plankton-eating and dwarf (having a seasonal change of plankton and benthic feeding)—that sympatrically inhabit Lake Davatchan (Transbaikalia). According to genetic data, these forms diverged in this lake from a specialized lacustrine ecotype of char and reached reproductive isolation. Comparative analysis revealed similarity in the shape of anlagen and transitive states of cranial bones. In prolarvae and larvae of the dwarf form, the onset of similar morphological states of skeleton elements occurs at a smaller body length than in fish of the small form. Differences in the development of serial skeleton structures (teeth, gill rakers, fin rays, centra, and scales), heterochronies of timing of appearance and rate of differentiation of skeleton elements were found. It is suggested that these differences resulted from the ecological differentiation of the two forms according to spawning grounds that became local habitats of larvae and fry (sublittoral and hypolimnion). The initial divergence could be caused by the presence in the lake of two (autumn and spring-summer) peaks of numbers of food organisms.

The development of an artificial hybrid and revealing elements of reproductive isolation between sympatric forms of Dryagin’s char and Salvelinus alpinus complex (Salmonidae) from Sobachye Mountain Lake (Taimyr)

The embryonic-larval development (at 3°C) of a hybrid between sympatric lake forms of Arctic char Salvelinus alpinus complex (large females of Dryagin’s char x male goggle-eyed char) from the polar mountain Lake Sobachye (the Norilo-Pyasina water system, Taimyr) was studied. No morphological disturbances were found in the embryonic membrane during development. After hatching, because of yolk sac soaking and blood circulation disturbances along its vessels, about 15% of specimens perished. The most mass disturbances in the development of free embryos and larvae that were manifested in the body curvature, loss of mobility, and subsequent death of a greater proportion of specimens were caused by modifications of differentiation of mesenchymal cells responsible for the axial skeleton formation. It is suggested that anomalies in osteogenesis and a high variation of age when dermal cranial bones (praeoperculum and frontale) appear that bear seismosensory system canal are related to the conflict of genetic programs of the development of parental forms. The rate of embryonic larval development of hybrid specimens exceeds that in the lake small form of Arctic char from Lake Davatchan (Transbaikalia) reared under the same conditions. The reproductive isolation of sympatric Dryagin’s char and goggle-eyed char in Lake Sobachye is provided by both pre- and postcopulation mechanisms. A possible mechanism of formation of reproductive isolation of sympatric forms related to colonization by them of a deep-water biotope is discussed.

Peculiarities of growth and skeletal system development of prelarvae, larvae, and fingerlings of Dolly Varden Trout Salvelinus malma malma inhabiting the rivers of Western Kamchatka in regard to the temperature regime of the spawning grounds

The order of the bone development and the peculiarities of the transitional forms of the skeletal system (cranium and serial structures, i.e., teeth, gill rakers, fin rays, and pterygiophores, spinal bones, predorsalia, and scales) have been studied for prelarvae, larvae, and fingerlings of anadromous Dolly Varden trout Salvelinus malma malma inhabiting the rivers and streams of Western Kamchatka. The fish fry were reared in laboratory conditions (breeders from Bol’shaya River) and sampled in the field (tributaries of Utkholok and Ozernaya rivers). Comparative analysis was performed. Slow growth and osteogenesis have been registered together with high variability of the growth rate of particular bones in regard to the body size increase. Late scale development (second year of life) was the feature of the young fish sampled in Ukhtolok River. We suggest high ratio of the open egg mass of Dolly Varden Trout in the upper stream of the rocky-bottom spring brooks. The intrusion of prelarvae after hatching in the open egg mass into the pebble layer draining by the flow has been found both for the specimens hatched in the laboratory and in the spawning grounds. These individuals tended to stay in this layer during the whole larval period.

Systematics and biology of the East Siberian char Salvelinus leucomaenis

A review that considers in detail for the first time the taxonomic position, phenetic diversity, and principal features of the endemic species East Siberian char Salvelinus leucomaenis in the range from the northeast of Asia to Japan based on own and published data is provided. In comparison with other species of chars, S. leucomaenis is characterized by a smaller morphological and ecological diversity. A migratory form feeding on fish is dominant in the range. At the same time, parallel to large migratory forms, other life forms—resident riverine and lacustrine-riverine forms represented by males and females and riverine and dwarf males were found in S. leucomaenis. Individuals with various color variations occur everywhere. Resident forms are rare in the north of the range; they are dominant in the south of the range, in Japan.

On morphological diversity of southern Dolly Varden trout Salvelinus malma krascheninnikovi from water bodies of Sakhalin

Morphological and some biological specific features of nine samples of the southern form of Dolly Varden trout Salvelinus malma krascheninnikovi from water bodies of Sakhalin were studied. Comparative analysis was performed of our own estimates and estimates made by other authors of meristic characters of Sakhalin populations of Dolly Varden trout, as well as of samples from water bodies of the Kuril Islands and Western Kamchatka. Sakhalin populations of S. malma krascheninnikovi are characterized by a low level of morphological differentiation and the absence of geographic structure. No clinal latitudinal variation in sample averages was revealed in either of the nine studied meristic characters, including the number of vertebrae for populations of S. malma krascheninnikovi in the range from Bol’shoi Shantar Island to the south of Sakhalin. The cline in vertebral number from Kamchatka, along the Kuril Islands to Hokkaido, is most likely explained by specific features of distribution and introgressive hybridization at the secondary contact of populations of the northern and southern forms of Dolly Varden trout that originated from different glacial refugia and had a different vertebral number rather than by the temperature gradient.

On brook chars of the southern Kuril Islands and a possible mechanism of formation of dwarf forms of Dolly Varden trout Salvelinus malma curilus

The specific morphological and biological features of dwarf chars Salvelinus malma curilus from three isolated populations of the southern Kuril Islands Kunashir and Iturup were studied. It was shown that brook dwarfs, in comparison with the migratory form of Salvelinus malma curilus, are characterized by a smaller diameter of spawned eggs (which corresponds to smaller yolk reserves and shorter embryos at hatching), retarded growth and morphogenesis of early juveniles, a mosaic pattern of paedomorphic and peramorphic morphological transformations, and a short lifespan. The population and age variability of the relative sizes and shape of otoliths was revealed. Dwarf populations are typically characterized by considerable morphological differences between males and females corresponding to those in migratory fish. The strategy of dwarfism is assumed to be built into the genome of the migratory ecotype of S. malma curilus.

New data on the trout Salvelinus leucomaenis and its relationships with Dolly Varden trout S. malma curilis in fresh waters of the southern Kuril Islands

The biology, structure of populations, and morphology of diadromous East Siberian char Salvelinus leucomaenis from two rivers of the Kuril Islands—the Kunashir and the Iturup—are studied and the resident lacustrine form from Lake Peschanoe is described for the first time. It is shown that the specific features of the anadromous migration of diadromous individuals, the relative numbers of juveniles of the trout Salvelinus leucomaenis, and the rate of their growth are determined by the temperature dynamics and the sizes of the freshwater water bodies used for spawning.

Patterns of development of the coldwater lacustrine-riverine form of the Drjagin charr (genus Salvelinus) from Lake Lama (the Taimyr Peninsula) during the larval period

Reproduction of the lacustrine-riverine form of the Drjagin charr (genus Salvelinus) from Lake Lama (the Noril’sk-Pyasina aquatic system on the Taimyr Peninsula) in a mountain tributary, the Bunisyak River, as well as the formation and development of skeletal elements in embryos and larvae reared under different experimental conditions are described. Patterns of the development and the heterochrony between the rates of somatic growth and osteogenesis are an adaptation to the extremely low water temperature and oligotrophic spawning habitat of the mountain stream. Still, the formation of vertebral centrae is retarded even at rather high rearing temperatures. As compared to larvae of the small normal (nondwarf) planktivorous lacustrine form of Arctic charr from Lake Davatchan (Transbaikalia) reared at 3°C, larvae of Drjagin charr from Lake Lama reared at 1°C are characterized by accelerated growth and heterochronies of osteogenesis. The divergence of the lacustrine-riverine form of Drjagin charr from the generalized form of Salvelinus alpinus in morphology begins during the larval period of the ontogeny.

Life cycle and structure of populations of three-spined stickleback Gasterosteus aculeatus (Fam. Gasterosteidae) in rivers of northwestern Kamchatka (with reference to the Utkholok River)

From the end of May to mid-August 2005 and 2006, the dynamics of migrations and spawning, as well as specific features of development, growth, and feeding migration of the three-spined stickleback Gasterosteus aculeatus in the salmon river Utkholok of the mountain-tundra type were studied. Morphological characteristics, age, fecundity, dates of reproduction and spawning biotopes, structure of spawning groups, and specific features of feeding were investigated. On the basis of the obtained data, it was concluded that the riverine and migratory forms of three-spined sticklebacks from the Utkholok River belong to a single population. Biological specific features of spawners with high (2005) and low (2006) numbers of the migratory form were compared. For comparison, we also used our own data on the morphology and biological analysis of the migratory three-spined stickleback from the Kol River salmon of the mountain type.

On nine-spined sticklebacks of the genus Pungitius (Gasterosteiformes) of Lake Bol'shoe (Bol'shoi Shantar Island, Shantar Islands)

Specific features of morphology and biology of two species of nine-spined sticklebacks—Pungitius sinensis and P. pungitius—dwelling in brackish Lake Bol’shoe (Bol’shoi Shantar Island) have been studied. Differences in the number of dorsal spines, vertebrae, and coloration, as well as the absence of specimens with an intermediate phenotype indicate the reproductive isolation of two species supported by the temporal separation of spawning periods. Species P. pungitius was found in Lake Bol’shoe for the first time.