Parasite Fauna of Baikal Oilfish (Comephorus spp.) (Cottidae, Scorpaeniformes) in Lake Baikal and Changes in the Age Series of the Hosts

The big and little Baikal oilfish are endemic to the Baikal Lake, being the most numerous fish species there. Only these two species make up the group of pelagic fish of Lake Baikal. The Baikal oilfish are characterized by a dispersed vertical distribution, from the surface to a depth of 1000 m or deeper. This study provides a description of the current situation regarding parasite infestation in the big and little Baikal oilfish and, for the first time, provides an analysis of changes in the fauna and numbers of parasites in the age series of these endemics of Lake Baikal. There are 14 and 15 species in the parasite fauna of the big and little Baikal oilfish, respectively. In total, the parasite fauna of both host species is represented by 17 species, of which 12 species are common to both fish species. There is a high degree of similarity in the species composition of parasites in the Baikal oilfish, however, trematodes were found in the little Baikal oilfish only, which indicates differences in ecology between the two host species. A discrepancy was revealed in changes in the species richness of parasites in the age series of the little and big Baikal oilfish, namely: it increases in the first host, while in the second host, the species richness of parasites first increases, then decreases in older age groups. This discrepancy between the Baikal oilfish is associated with differences in the composition of the food bolus in the middle and older age groups of these fish.

Lipid Accumulation and Fatty Acid Composition During Maturation of Three Pelagic Fish Species in Lake Baikal

Molecular divergence and speciation of Baikal oilfish (Comephoridae): Facts and hypotheses

Toxaphene contamination in Lake Baikal's water and food web

Mutagenic substances are amongst the most dangerous compounds of the antropogenic pollution. Their action may be delayed and later manifested in the subsequent generations of animals (including fish) and people. Recent sharp increases in the number of tumours in fish in most cases can be attributed to the pollution of aquatic ecosystems with mutagenic and carcinogenic xenobiotics (MCX), with a smaller number of malformations caused by viral diseases. Chemical methods of detection are not sensitive enough to monitor MCX which can cause biological effects at extremely low concentrations in tissues of animals. The advantages of biological testing are high sensitivity and possibility to identify compounds which acquire mutagenic and carcinogenic properties after metabolic activation, for instance with cytochrome P-450. We assayed tissue extracts of aquatic organisms (aquatic plants, decapoda, molluscs, fish, Baikal seals, fish-eating birds and their eggs) from Lake Baikal and the Selenga River estuary as well as fresh and waste water samples usingSalmonella/microsomeAmes test. Presence of MCX was followed in the main food chain in Lake Baikal which consists of a primary zooplankton producerEpishura baikalensis(90%) and amphipods, endemic sculpins (the main species of Baikal oilfish) and Baikal seal. We did not find mutagenic activity in the fish tissues. However some extracts from seal fat and muscles demonstrated genotoxic activity. Frame shift mutations were caused by mutagenic samples from seal fat (Salmonella typhimurumstrain TA 98).

Fauna of parasites of burbot from the Baikal Rift Zone (Lake Baikal, Lake Khuvsgul, and Tsipo- Tsipikan and Kuanda-Chara lakes) includes 46 species of 11 classes. The species composition of fauna of parasites of burbot decreases in the following sequence: Lake Baikal (37 species) > lakes Tsipo-Tsipikan (18 species) > Lake Khuvsgul (15 species) > Kuanda-Chara lakes (11 species). The burbot populations of the studied lakes form two large groups according to the results of cluster analysis of species composition of the parasite fauna. The first group includes the host populations of Tsipo-Tsipikan and Kuanda-Chara lakes; the second combines the burbot populations of the gilfs and estuaries of tributaries of Lake Baikal and Lake Khuvsgul. The use of parasitological data in addition to molecular genetic information and paleontological information brings new arguments to the discussion about the evolutionary history of burbot.

There are almost three hundred years of ichthyologic studies in Lake Baikal and in its catchment area.During this time, they moved away from brief faunal reviews and taxonomic descriptions towards integrated and interdisciplinary studies oriented to fish biodiversity, systematics, phylogeny, evolution, ecology, morphology and physiology.Results of these studies are published in many papers.They constitute a basis of the current knowledge about fish of Lake Baikal, and they will be still in demand in the future.The importance of the ichthyologic research in Lake Baikal is due to necessity to resolve several problems in the following areas: fish abundance dynamics, reproduction of fish stock, creation of a biological basis for fisheries and study of fish ailments.Hence, a very promising is to develop methods of a complex monitoring of fish in Lake Baikal.Baikal omul Coregonus migratorius (Georgi, 1775) is the main commercial species of Lake Baikal, thus the census of its population size and biomass is a goal of the rational nature resource management.The urgency of

A revision of the composition of parasites of two widely distributed in Baikal species of cottoid fish - the sand ( Leocottus kesslerii Dybowski, 1874) and the stone ( Paracottus knerii Dybowskii, 1874) sculpins was performed. This composition includes 60 species and subspecies of parasites belonging to 10 types, 12 classes, 14 orders, 24 families and 32 genera. It is represented by 21 endemic taxa of species and subspecies rank: these are blood parasites - trypanosomes and cryptobia (2), myxosporidia (5), infusoria (7), monogeneans (1), nematodes (2), acanthocephales (1), leeches (2) and crustaceans (1). Comparison of the parasite fauna of sand and stone sculpins with that of the families Abyssocottidae and Comephoridae showed that most of all this fauna is closely related to the parasite fauna of the family Abyssocottidae. Revision of the parasite composition of two widely distributed fish in Baikal in the light of modern data has identified a number of important problems in the study of fish parasites of this reservoir. Since there has been a transformation of views on the taxonomy of individual groups, new information has been obtained on morphology, molecular biology, biochemistry, life cycles and distribution in the plant and animal world, it is necessary to continue the study of Baikal parasites by modern methods.

Parasite Fauna of Sand and Stone Sculpins (Scorpaeniformes, Cottidae) from Lake Baikal (Review of Results and Prospects of Investigations)

According to modern data, 260 species of parasites have been observed in Baikal fish, most of them have a simple life cycle (63.1%). The parasite fauna of introduced fish includes 48 species, including 15 specific ones that were imported from the mother reservoirs. The most ancient are the endemic simple parasitic systems of Cottoidea, which were formed as a result of prolonged isolation of their hosts in Lake Baikal (in the Pliocene, 2.5 million years ago).

Intraspecific genetic polymorphism of a Baikal Lake endemic, big Baikal oilfish (Comephorus baicalensis Pallas, 1776), was evaluated based on microsatellite analysis. The obtained results have compared to the results received earlier for a little Baikal oilfish (C. dybowski Korotneff, 1905). Six microsatellite loci designed for the European sculpin, Cottus gobio, were used. Big Baikal oilfish samples were tested from the three Baikal trenches (southern, middle, northern). Average values of FsubST/sub and RsubST/subindexes between the samples did not exceed 0,02 that point to weak intraspecific genetic differentiation. Big Baikal oilfish had the smaller allele variety, the greater deficit of heterozygotes and presence of low-molecular alleles in comparison with little Baikal oilfish. The values of genetic differentiation were equaled FsubST/sub = 0,138 and RsubST/sub = 0,244 for all loci between cumulative samples of little and big Baikal oilfish. Analysis of microsatellite polymorphism has showed that both a big and little Baikal oilfishes are represented by single populations. The factor promoting panmixia within the Baikal oilfish species is apparently a passive transfer of juvenile and adult fishes by water currents.

Sculpins are predominantly benthic sit-and-wait predators that inhabit marine and freshwaters of the Northern Hemisphere. In striking contrast to riverine relatives, sculpins endemic to Lake Baikal have diversified in both form and function, with multiple taxa having adaptations for pelagic and bathyal niches within the world’s deepest lake. Baikal Oilfishes (Comephorus spp.) represent a highly apomorphic taxon with unique skeletal morphology, soft anatomy, and reproductive ecology. Selection for novel behavior and life history may be evident in genes responsible for organismal energy balance, including those encoding subunits of the electron transport chain. Complete mitochondrial genomes were sequenced for the Big Baikal Oilfish (Comephorus baicalensis) and Little Baikal Oilfish (Comephorus dybowskii). Mitochondrial genomes encode genes essential for electron transport, and data provided here will complement ongoing investigations of genome-to-phenome maps for teleost respiration and metabolism. Phylogenetic analyses including oilfish mitogenomes and all publicly available cottoid representative sequences are largely concordant with previous studies.

Morphometric investigations of the gill apparatus in the small golomyanka, Comephorus dybowskii, revealed a unique structure and a very small gill respiratory area (GRSA) compared with other endemic Cottoidei of Lake Baikal: from 5.5 to about 7 times smaller than in the pelagic waterside sculpins. Cottocomephorus grewingki and C. inermis, and about 3 times smaller than in groundling deep‐water Cotinella boulengeri. This is an extremely small GRSA considering no accessory respiratory organs are present. Scanning electron microscopic observations revealed numerous chloride cells in the epithelium of golomyanka gill lamellae but not in the sculpin lamellae. Chloride cells probably restrict gas exchange in the lamellae considerably. The results suggest that golomyankas have a small oxygen requirement.

Planktonic sculpins (Comephorus baicalensis and Comephorus dybowskii) are endemic to Lake Baikal, and their migration behavior is characterized by their strange movements, which occur only vertically. We investigated their detailed food sources at each growth stage by stable isotope analyses in combination with stomach content analysis. At all growth stages, both fishes and amphipods were the main diet for C. baicalensis, whereas amphipods alone were the main diet for C. dybowskii. Our results indicate that the relationship between the two species shifts from a competitive interaction to a predator–prey interaction with the growth stages of C. baicalensis.

Fragments of mtDNA genes Cyt B, ATPase 6, and ATPase 8 of six cottoid fishes species of Lake Baikal (East Siberia) were amplified and sequenced. In addition mtDNAs of the same fish were subjected to restriction analysis. The data obtained were used to construct phylogenetic trees. The topology of the ATPase tree differs from those of the Res (restriction) and Cyt B trees. Clustering of species within the trees confirms the viewpoint of Taliev (1955, Baicalian Sculpins (Cottoidei)) according to which Baikalian cottoids originate from two ancestral forms. The times of branching obtained do not confirm the existing viewpoint according to which the two golomyankas (Comephorus baicalensis and Comephorus dybowskii) are pre-Baikal (Myocene) relicts: these two species may have originated 1.2-1.8 million years ago in Baikal, and they seem to represent an example of rapid morphological evolution which resulted in the formation of a new family.