bones_development

The skeletal elements measured were ranked by developmental rate to perform a comparative analysis of osteogenesis. A score-scale ranking was used for bones, which were classified according to Jollie (1986

linear_morphometrics

The juveniles with a fork length of 61–124 mm (parrs with 2-3 annual rings on otoliths, age 2+ to 3+) were used to analysis of body shape. The extraction of truss distances from the digital images of seven Lake Kronotskoe morphs and Dolly Varden was conducted using tpsUtil and tpsDig2 v2.16 software platforms (Rohlf, 2010)

The riverine dwelling groups of endemic Dolly Varden (Salvelinus malma, Salmonidae) morphs from lake Kronotskoe (Kamchatka, Russia)

Dwarf males and fluvial groups were found in the population structure of endemic Dolly Varden (Salvelinus malma) morphs dwelling the Lake Kronotskoe basin. Apart from the lacustrine-riverine charrs, dwarf males and fluvial groups stay in the vicinity of their own spawning grounds for their whole life at the upper reaches of the lake tributaries. Fluvial males and females were found only for white charr morph which can be defined as the biggest generalist among the endemic Lake Kronotskoe charrs. It was found that propensity for dwarf males' formation for different morphs of nosed charrs corresponds to the complexity of the river habitats i.e. amount of the covers and lateral branches. No fluvial individuals were registered for longhead charr regarded as one of deep-specialised predatory morph. It was revealed that all riverine dwelling groups are defined by a similar lifestyle; however they are distant from each other by body shape and closer to the corresponding morph representatives rather than to each other or to the ancestral Dolly Varden. The morphology data underlines that riverine dwelling groups are an inherent part of each morph and should be considered as a life strategy variance, but not as distant morphs. The unidirectional patterns of the morphological development for riverine-lacustrine and fluvial groups point to the heritability bases for those traits. The conserving of specific morphology within the fluvial groups lets us suggest an approach for allowing a reconstruction of the populations heavily damaged by anthropogenic activity

Data from: Juvenile divergence in adaptive traits among seven sympatric fish eco-morphs arises before moving to different lacustrine habitats

Identifying the mechanisms initiating sympatric diversification in vertebrates has remained a conceptual challenge. Here we analyze an assemblage of sympatric charr (Salvelinus malma) morphs from landlocked Lake Kronotskoe basin as a model to uncover the divergence pathways in freshwater fishes during the early life history stages. All morphs have distinct developmental biology, but a similar developmental rate retardation compared to the ancestor. Our study reveals that adult morphological differences, which acquire functionality at maturation, originate in the early juvenile stages due to heterochrony in skeletogenesis and allometric changes triggered by variation in metabolic activity. The craniofacial differences among the morphs result from asynchronous development of several skeletal modules. The accelerated ossification of teeth-armed bones occurs in predatory feeding morphs, while cranial cover ossification is promoted in benthivorous morphs. These contrasting growth patterns have led to seven phenotypes that span a range far beyond the ancestral variability. The most distinct morphs are a riverine-spawning, epilimnetic predator and a lacustrine-spawning, profundal benthic feeder. Taken together, we argue that the adaptive morphological differentiation in these sympatric freshwater fishes is driven by diverging patterns in ossification rate and metabolic activity against a background of uneven somatic growth. This divergence is primarily associated with basic environmental differences on the nursery grounds that might be unrelated to resource use. This non-heritable phenotype divergence is then exposed to natural selection that could result in further adaptive genetic changes

Trophic segregation in multispecies community of salmonids in the Penzhina River lower course (Kamchatsky Krai, Russia)

Trophic relationships are presented for the juveniles of Coregonus sardinella, C. subautumnalis, C. pidschian, Prosopium cylindraceum, and Thymallus arcticus mertensii jointly inhabiting the Penzhina River lower reaches in summer. This community has no analogues in the North-Okhotsk region in terms of freshwater salmonid diversity. We analysed the stomachs content, indicative parasites infestation and stable isotopes ratio in the muscles. We demonstrated the similarity of food niches for the following pairs of species P. cylindraceum – T. а. mertensii and C. sardinella – C. subautumnalis. The summer diet of the species pair P. cylindraceum – T. а. mertensii mainly consisted of chironomid larvae. At the same time, mysids dominated in the diet of the species pair C. sardinella – C. subautumnalis. Coregonus pidschian mainly fed on gammarids. The following parasites have been found in juvenile fishes: Chloromyxum tuberculatum, Myxobolus spр., Proteocephalus longicollis, Triaenophorus nodulosus, Diplostomum sp., Metecercaria spp., Pronoprymna petrowi, Cystidicola farionis, Salmonema ephemeridarum, Raphidascaris acus, Pseudocapillaria salvelini, Echinorhynchus cotti, and Salmincola extensus; herewith, the intensity of invasion was low for all parasites. Only T. а. mertensii has been infested by C. tuberculatum, T. nodulosus, and C. farionis. Only C. pidschian was infested by P. longicollis. Only C. sardinella and C. subautumnalis have been infested by P. petrowi, while Salmincola extensus has infested only P. cylindraceum in the studied ecosystem. Thymallus arcticus mertensii and C. pidschian are significantly different from other fish species in term of infestation by the helminths E. сotti and P. salvelini. In the δ 13С–15N isotopes space, the fish juveniles formed three groups: 1) with high 15N level (C. sardinella – C. subautumnalis), 2) with low 13С level (C. pidschian), and 3) with low 15N – high 13С level (P. cylindraceum – T. а. mertensii). The complexity of trophic relationships of juvenile salmonids in the River Penzhina and an increased feeding competition in the species pairs threaten the functioning of the unique River Penzhina salmonid community under the conditions of extreme fishing pressure in the Northern Far East

Phylogeny, Distribution, and Biology of Pygmy Whitefish (<i>Prosopium coulterii</i>) in the Beringia Region (Chukotka)

The pygmy whitefish Prosopium coulterii (C. H. Eigenmann & R. S. Eigenmann, 1892) is a freshwater fish with a highly disjunct distribution ranging from the middle part of North America to Chukotka. There is still no consensus regarding its phylogeny and dispersal history due to limited information from the Chukotkan part of the range. We investigated 22 lakes over Chukotka and found a much broader distribution than it was previously thought. Pygmy whitefish was found to be a common species in the lakes that belong to rivers draining into the Arctic. Cytochrome B, cytochrome oxidase subunit 1, and ATP synthase F0 subunit 6 mitochondrial sites were analyzed from 25 samples to reconstruct the phylogenetic history of pygmy whitefish. Two haplogroups belonging to the east and west Chukotkan ranges were identified; both groups are closely related to Alaskan pigmy whitefish and distant from the Cascadia-Mackenzie (Peace) populations. Combining the distribution patterns, phylogenetic network topology, and the contemporary knowledge on the glaciation history of the region, we suggest a possible colonization pathway over Beringia region and beyond it. The basic biological characteristics (fork length, number of gill rakers, and pyloric caeca, age structure, and feeding) are also presented to characterize the populations over the investigated range

Trout and Char of Northern Europe

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