Early Postembryonic Development Research Articles

Dynamics of ultrastructural changes in the yolk syncytial layer and its microenvironment during gastrulation and early postembryonic development of <i>Hemichromis Bimaculatus</i>

BACKGROUND: In fish embryogenesis, the yolk sac is the critical provisional organ, actively functioning during the embryonic and early postembryonic stages. Its primary role is trophic, facilitated in Teleostei by a specialized structure — the yolk syncytial layer (YSL). Ultrastructural transformations of this layer during gastrulation and early postembryonic development, as well as its interaction with migrating muscle fibers and melanophores, are probably necessary for the efficient use of nutrients by the developing embryo. The yolk sac’s role in the embryogenesis of Hemichromis bimaculatus may extend beyond current conceptions. AIM: To study the structural organization of the Jewel Cichlid (H. bimaculatus) yolk sac during the embryonic and early postembryonic development. MATERIALS AND METHODS: The research was involved 22 embryos and larvae of H. bimaculatus from 1 to 7 days after egg laying. The morphological features of the yolk sac were studied using light and transmission electron microscopy. RESULTS: By day 2, the yolk sac was separated from the embryo by the trunk fold. Its main structure was the YSL, containing numerous nuclei, microvilli, mitochondria and phagolysosomes. The morphological features of the YSL were similar to those of the placental symplastotrophoblast and indicated high functional activity. The yolk sac mesenchyme contained blood vessels, migrating melanophores, and muscle fibers. The periderm, covered with a special shell, fuunctioned as the primary skin of the embryo. The transition to exogenous nutrition in Jewel Cichlid larvae was accompanied by a significant decrease in yolk sac size with its subsequent involution. CONCLUSIONS: The trophic function of the yolk sac in H. bimaculatus is mediated by the YSL, which, during gastrulation and postembryonic development, interacts with a number of structures present in the yolk sac wall. Migrating muscle fibers promote activation of yolk granules; accumulation of toxic metabolic products is associated with melanophores. The special structure of the periderm protects both the yolk sac and the embryo from external influences.

Free long-chain fatty acids trigger early postembryonic development in starved Caenorhabditis elegans by suppressing mTORC1.

Postembryonic development of animals has long been considered an internally predetermined program, while macronutrients were believed to be essential solely for providing biomatters and energy to support this process. However, in this study, by using a nematode Caenorhabditis elegans (abbreviated as C. elegans hereafter) model, we surprisingly discovered that dietary supplementation of palmitic acid alone, rather than other abundant essential nutrients such as glucose or amino acid mixture, was sufficient to initiate early postembryonic development even under complete macronutrient deprivation. Such a development was evidenced by changes in morphology, cellular markers in multiple tissues, behaviors, and the global transcription pattern and it occurred earlier than the well-known early L1 nutrient checkpoint. Mechanistically, palmitic acid did not function as a biomatter/energy provider, but rather as a ligand to activate the nuclear hormone receptor NHR-49/80, leading to the production of an unknown peroxisome-derived secretive hormone in the intestine. This hormonal signal was received by chemosensory neurons in the head, regulating the insulin-like neuropeptide secretion and its downstream nuclear receptor to orchestrate global development. Additionally, the nutrient-sensing hub mTORC1 played a negative role in this process. In conclusion, our data indicate that free fatty acids act as a primary nutrient signal to launch the early development in C. elegans, which suggests that specific nutrients, rather than the internal genetic program, serve as the first impetus for postembryonic development.

DEFECTIVE KERNEL1 regulates cellulose synthesis and affects primary cell wall mechanics.

The cell wall is one of the defining features of plants, controlling cell shape, regulating growth dynamics and hydraulic conductivity, as well as mediating plants interactions with both the external and internal environments. Here we report that a putative mechanosensitive Cys-protease DEFECTIVE KERNEL1 (DEK1) influences the mechanical properties of primary cell walls and regulation of cellulose synthesis. Our results indicate that DEK1 is an important regulator of cellulose synthesis in epidermal tissue of Arabidopsis thaliana cotyledons during early post-embryonic development. DEK1 is involved in regulation of cellulose synthase complexes (CSCs) by modifying their biosynthetic properties, possibly through interactions with various cellulose synthase regulatory proteins. Mechanical properties of the primary cell wall are altered in DEK1 modulated lines with DEK1 affecting both cell wall stiffness and the thickness of the cellulose microfibril bundles in epidermal cell walls of cotyledons.

Morphological Variability of the Smelts (Osmeriformes: Osmeridae) of the Russian Far East

This paper presents the first study comparing the smallmouth smelts – the Japanese smelt Hypomesus nipponensis McAllister, 1963, the pond smelt H. olidus (Pallas, 1814), the marine smelt H. japonicus (Brevoort, 1856) – and the Asiatic smelt Osmerus dentex Steindachner et Kner, 1870 with the use of the variance of fluctuating asymmetry, the coefficient of variation, and the mean values of characters of these species. The comparison showed that the Asiatic smelt was characterized by the largest sum of dispersions of all characters, while the marine smelt had the smallest sum, which was obviously associated with more stable conditions of embryonic and early postembryonic development of the marine smelt. Japanese and pond smelts were similar in coefficients of variation for all traits. The Asiatic smelt displayed the maximum sum of coefficients of variation of all characters; while the marine smelt had the minimal sum of coefficients of variation of the characters, which may indicate relative morphological stability of this species in the range of its occurrence. A greater variability of smelts spawning in fresh water is in good agreement with the conclusion of G.V. Nikolsky et al. that the variability of traits in freshwater fish species is higher than in marine fish species. According to the average values for the characters, the four species of smelts differed only in the number of rays in the pectoral fins, while the minimum value was typical of the pond smelt, and the maximum value – for the marine smelt. The Japanese (24) and pond (26) smelts showed the minimum differences from other species, and the marine and Asiatic smelts – maximum differences (28).

Effect of blue and red monochromatic light during incubation on the early post-embryonic development of immune responses in broiler chicken

ABSTRACT 1. The light regime during incubation can influence embryonic and post-embryonic life and its effects can be mediated by rhythmic melatonin production in the embryonic pineal gland. 2. This study explored whether the incubation of chick embryos under red or blue monochromatic light, which induces maximum and minimum melatonin production, respectively, can influence the development and reactivity of the immune system in chicks. 3. In hatchlings, basal expression of immune genes (AvBD-1, PSEN-1, and IL-6) was evaluated in the duodenum using real-time PCR. The expression of these genes was measured weekly for three weeks after hatching, 3 h after intraperitoneal lipopolysaccharide (LPS) injection. At these times, the heterophil/lymphocyte ratio (He/Ly) was evaluated on blood smears, plasma immunoglobulin Y (IgY) concentrations by ELISA and IL-6 gene expression in the spleen by real-time PCR were determined. 4. During development, the He/Ly ratio and plasma IgY concentration were not significantly influenced by the light quality during incubation. Red light increased gene expression of AvBD-1 in hatchlings and IL-6 in two-week-old chickens compared to birds incubated under blue light. The expression of IL-6 after LPS stimulation increased in an age-dependent manner, both in the duodenum and the spleen, reflecting the maturation of the immune system. 5. The results suggested that red light may increase the local immune response in the gut immediately after hatching, but this effect was not apparent during later development.

A Comparative Study of Lipids and it’s Dynamic during Embryogenesis and Early Post-Embryonic Development of Atlantic Salmon (Salmo salar L.) and Brown Trout (Salmo trutta L.)

A Comparative Study of Lipids and it’s Dynamic during Embryogenesis and Early Post-Embryonic Development of Atlantic Salmon (Salmo salar L.) and Brown Trout (Salmo trutta L.)

Variability of Siberian Taimen Hucho taimen (Salmonidae) of The Amur River

The morphological variability of nine characters in six samples of Siberian taimen Hucho taimen from the Amur River was studied. The differences in the level of fluctuating asymmetry of fish from different tributaries are small, which indicates the similarity of the conditions of embryonic and early postembryonic development; significant differences between the samples were noted only in six cases. The maximum fluctuations in the coefficient of variation are characteristic for the number of postorbital bones and channels of the seismosensory system on the 1st postorbital bone; the minimum, for the number of soft rays in the pectoral fins and channels of the seismosensory system on the preopercular bones. The largest sum of the variation coefficients values for individual characteristics differs in the sample from the Bikin River; the smallest, the Limuri River. These difference positively correlates with the length and area of ​​the basin of these tributaries. A regular decline in the mean values in the fish sampled at increasing distance from the mouth of the Amur River concerns only the number of postorbital bones. Clustering according to the mean values ​​of the features, revealed that the samples form three clusters: (1) the rivers Bol’shaya Ussurka and Tyrma (2nd order tributaries, the farthest from the Amur mouth), (2) the Limuri River (the least distant from the Amur mouth), 3) the rivers Anyui, Khor and Bikin (geographically close populations). Revealed features may indicate the similarity of the conditions of early development and the likelihood of gene exchange between the last three groups.

The change of the intestinal microbiocenosis of chickens in the age aspect and the introduction of biologi-cally active substances

The article provides information on the species composition of the microflora of the digestive tract in chickens of the Dekalb cross, its changes during the period of early postembryonic development against the background of the introduction of biologically active substances. The assessment of the degree of influence of the use of monopreparations and their combinations is given. The study was carried out in 2020 at the Department of Obstetrics, Surgery and Non-communicable Animal Diseases of the Ivanovo State Agricultural Academy. The initial analysis of the microflora of the digestive tract was carried out in 5-day-old chickens. Chickens of experimental groups 2, 3 and 4 were injected with biologically active substances, respectively, probiotic Zoonorm at a dose of 0.2 g per head in the morning mixed with feed; a 0.3% suspension of an enterosorbent based on polymethylsiloxane polyhydrate was drunk 2 hours after the last feeding and a combination of two drugs at the appropriate time. The drugs were used for 20 days, the study of the composition of the intestinal microflora was carried out in 15- and 25-day-old chickens and 10 days after drug withdrawal. The results showed that during the critical period of development in the control and experimental groups of chickens there is a decrease in the number of intestinal residents. In control chickens, proliferation of Enterobacter cloacae is noted and the number of clostridia increases. Against the background of the probiotic, the number of lactobacilli, enterococci and E. coli (typical) increases and is restored. With the introduction of enterosorbent, the content of lactobacilli increases, proliferation of Enterobacter cloacae is absent throughout the experiment. The combination of probiotic and enterosorbent prevents the development of pathogens, stimulates the growth of lactobacilli, enterococci and stabilizes the amount of typical E. coli and bacteroids. Scientific novelty lies in the establishment of a regulating and stabilizing effect on the intestinal biome of a combination of probiotic and enterosorbent; elucidation of the metabolic and antagonistic function of bifidobacteria in chickens at an early stage of postembryonic development.

English

Abstract Morphology in general and developmental morphology in particular provide us with an insight into the evolution, phylogeny, ecological features, behavior, and life cycle of organisms. The present study describes the external morphology of the first three postembryonic developmental stages (Stage 1­3) of two prominent European crayfish species, the noble crayfish Astacus astacus (Linnaeus, 1758) and the narrow­clawed crayfish Pontastacus leptodactylus (Eschscholtz, 1823). External morphology and setation of appendages are similar, presence of re­curved tips for cheliped in Stage I and then the tip lost in Stage 2, long plumose setae on the telson in Stage 2 and then the setae disappearance in Stage 3 accompanied with the fully developed tail fan. The number of segments on antennal flagella differs between the species in Stage I and Stage II. Observed findings on early postembryonic development are consistent between European and North American (Pacifastacus sp.) astacid species, but differ in certain aspects from other crayfish families.

ДВА ЭКСПРЕСС-МЕТОДА ОЦЕНКИ УРОВНЯ ЗАГРЯЗНЕНОСТИ ПРЕСНОВОДНЫХ ВОДОЕМОВ

The experiment is based on the assess-ment of water quality, based on the state of the organism of fish and crustaceans. Fish were surveyed in 1970-2016 years. The work was carried out in various regions of the USSR and Russia on reservoirs of vari-ous types, on fish farms. Various species and age groups of fish were studied. They were caught with a trawl, nets, a lift and sports fishing gear, and fish larvae were caught with a plankton net. A patho-anatomic meth-od was used to assess the condition of fish. Branched crustaceans were examined in 1989-2016. Samples were collected by plankton grid in reservoirs of the Volga, in lakes of the Karelian isthmus, in mountain lakes of the Western Sayan (East. Siberia), in lakes Ilmen and Sevan (Republic of Ar-menia) and in lake Ladoga, in the Nyvchim reservoir (Vychegda river basin), in pools of the Bolshezemelskaya tundra, in the Cu-ronian and Finnish bays of the Baltic sea. Samples were stabilized with 4% formalin and viewed under the MBS-9 binocular mi-croscope. Two methods for assessing the level of contamination of freshwater reservoirs were suggested. First: assessment of the level of pollution by the state of the fish organism. Toxicological studies of reservoirs and in experimental conditions have shown that fish were the most informative indicators of pollution of fishery reservoirs. The ecologi-cal approach to bioindication of the environ-ment using fish as the individual level is associated with changes in various indicators that characterize certain aspects of fish biol-ogy (weight and linear growth rate, fatness, fertility, reproduction process, embryonic and early post-embryonic development, pa-thologies, etc.). And the second method is to assess the level of contamination based on the state of the organism of pelagic branched crustaceans.

Morphological Variability of Big-Scaled Redfin Tribolodon hakonensis (Cyprinidae)

Morphological variability of seven characteristics of two forms of the big-scaled redfin Tribolodon hakonensis from ten reservoirs of the Far East is studied. Three indicators are analyzed—fluctuating asymmetry, geographical variability, and variability of characteristic values. Differences in the level of fluctuating asymmetry of T. hakonensis from different samples are due to different conditions of embryonic and early postembryonic development. The northern form differs from the southern one by a large average value of the sum of dispersions in all characteristics; this indicates a reduced stability of development. The geographical variability of T. hakonensis is manifested in six characteristics. Forms reliably differ from each other by average values of features, except for the number of infraorbital bones. The average values ​​of the coefficient of variation of characteristics vary considerably; the forms do not differ among themselves, and this indicator is noticeably higher only by the number of postorbital bones in the southern form. The largest number of significant differences in the dispersion of fluctuating asymmetry, average values ​​of characteristics, and coefficients of variation is most often observed when comparing between samples of the northern form, while that for the southern one is always minimal or absent altogether; this may be a result of sampling of the northern form from a much larger part of the area and a higher level of nucleotide variability in the northern form compared with the southern one.

Ultrastructural differentiation of plasma membrane and cell junctions in the hindgut cells is synchronized with key developmental transitions in Porcellio scaber

Differentiation of transporting epithelial cells during development of animal organisms includes remodelling of apical and basal plasma membranes to increase the available surface for transport and formation of occluding junctions, which maintain a paracellular diffusion barrier. This study provides a detailed ultrastructural analysis of apical and basal plasma membrane remodelling and cell junction formation in hindgut cells during late embryonic and early postembryonic development of the crustacean Porcellio scaber. Hindgut cells in late-stage embryos are columnar with flat apical and basal plasma membranes. In early-stage marsupial mancae the hindgut cells begin to acquire their characteristic dome shape, the first apical membrane folding is evident and the septate junctions expand considerably, all changes being probably associated with the onset of active feeding. In postmarsupial mancae the apical labyrinth is further elaborated and the septate junctions are expanded. This coincides with the transition to an external environment and food sources. First basal infoldings appear in the anterior chamber of early-stage marsupial mancae, but in the papillate region they are mostly formed in postmarsupial mancae. In molting late-stage marsupial mancae, the plasma membrane acquires a topology characteristic of cuticle-producing arthropod epithelia and the septate junctions are considerably reduced.

Influence of Triiodothyronine (T3) on the Reproduction and Development of the Green Terror Andinoacara rivulatus (Cichlidae)

It has been shown experimentally that hyperthyroidism, caused by prolonged treatment of triiodothyronine, influences on the development of secondary sexual characteristics, fertility and spawning behavior of the green terror Andinoacara rivulatus. In hyperthyroid fish with pronounced morphological consequences due to heterochronies, decreases the number of eggs in clutches and increases the time interval between spawnings. At the same time, hyperthyroidism in the parental pairs does not have any influence on the embryonic and early postembryonic development of offspring (hatching time, survival and frequency of developmental abnormalities). The obtained results give prospect for further studying the role of the thyroid signaling pathway in the regulation of ontogenesis in teleost fish.

Embryonic and larval development of bering founder Hippoglossoides robus¬tus (Pleuronectidae) in the northern Okhotsk Sea

The main stages of embryonic and early post-embryonic development of bering flounder in the northern shelf areas of the Okhotsk Sea are described for the first time, their timing is determined and the heat amounts necessary to achieve the stages are evaluated on the base of experimental data. The developing eggs had an average diameter of 2.33 ± 0.01 mm and volume — 5.66 ± 0.05 mm3. The yolk occupied 19.36–31.15 % (on average 24.40 %) of the egg volume that corresponded with the polyplasmatic type of eggs. Time of the eggs incuba­tion from the beginning of epiboly to hatching of prelarvae was 238 hours in the experiment under temperature 8.1 oC. The total time of embryogenesis was estimated as 276 h, and the heat amount required for the total embryogenesis — as 2236 degree-hours. At the stage of the blastula cells gastrulation, the process of axial convergence of the blastoderm directed to forming of an axial bud in the embryo. The Kupfer vesicle was developed and the body pigmentation appeared before closing of the blastopore, but segmentation of the body started after the closing. The muscle activity was detected only with start of the heart working, in opposite to other studied flounders which muscles became active earlier. The newly hatched prelarvae had the body length 4.85–6.00 mm, on average 5.44 ± 0.06 mm. Their transition to mixed and exogenous nutrition occurred at the age of 2 and 3 days, respectively, when their average size was 5.75 ± 0.17 and 5.83 ± 0.17 mm. Following to the experimental and cited data, morphology of prelarvae and larvae of bering flounder is distinguished by weak development of black melanophore on the dorsal side and its absence on the fin fold, as well as relatively early pigmentation of eyes with guanophore.

Experimentally increased nest temperature affects body temperature, growth and apparent survival in blue tit nestlings

The thermal environment experienced by birds during early postembryonic development may be an important factor shaping growth and survival. However, few studies have directly manipulated nest temperature (Tn) during the nestling phase, and none have measured the consequences of experimental heat stress on nestlings’ body temperature (Tb). It is therefore not known to what extent any fitness consequences of development in a thermally challenging environment arise as a direct, or indirect, effect of heat stress. We, therefore, studied how experimentally increasedTnaffectedTbin 8–12 d old blue titCyanistes caeruleusnestlings, to investigate if increased thermoregulatory demands to maintain normothermicTbinfluenced nestling growth and apparent long‐term survival. Nestlings in heated nest‐boxes had significantly higherTbcompared to unheated nestlings during most of the experimental period. Yet, despite facingTn 50°C (as measured in the bottom of the nest cup below the nestlings), the highest nestlingTbrecorded was 43.8°C with nestlings showing evidence of controlled facultative hyperthermia without any increased nestling mortality in heated nests. However, body mass gain was lower in these nestlings compared to nestlings from control nest‐boxes. Contrary to our prediction, a larger proportion of nestlings from heated nest‐boxes were recaptured during their first winter, or subsequently recruited into the breeding population as first‐ or second‐year breeders. This result should, however, be treated with caution because of low recapture rates. This study highlights the importance of the thermal environment during nestling development, and its role in shaping both growth patterns and possibly also apparent survival.

The effect of temperature and light on embryogenesis and post-embryogenesis of the spider Eratigena atrica (Araneae, Agelenidae)

Embryogenesis and post-embryogenesis of spiders depend on several environmental factors including light and temperature. This study was aimed at evaluating the impact of different thermal and lighting conditions on embryonic and early post-embryonic development of Eratigena atrica. Embryos, larvae, nymphs I and II were incubated at constant temperatures of 12, 22, 25 and 32°C under three different light regimes: light, dark, light/dark. Extreme temperatures (12 and 32°C) significantly increased mortality of embryos (to 100%) and nymphs II, whereas larvae and nymphs I suffered reduced survival only at the lowest temperature. Moreover, the lowest temperature reduced the development rate of all stages. The impact of light conditions was less pronounced and more variable: constant light reduced the survival of nymphs I at lower temperatures, but increased that of larvae. Moreover, light increased the time of embryonic development and duration of nymphal stages, particularly at lower temperatures (12–22°C). Thus, the most optimal locations for spiders seem to be dark (though except larval stage) and warm (25°C) sites, where their development is fastest and mortality lowest.

Reproduction, embryonic and early post-embryonic development of saffron cod <i>Eleginus gracilis</i> (Gadidae) from the Tauyskaya Guba Bay (northern Okhotsk Sea)

New information on reproductive biology, embryonic and early post-embryonic development of saffron cod Eleginus gracilis Tilesius is presented on the base of long-term observations in the Tauyskaya Guba Bay, northern Okhotsk Sea. The species begins to spawn in this area at the age of 2 years, with the body length of 14 cm, and reaches mass maturity (when at least 50 % of fish in the age group are matured) at the age of 3 years. All fish are matured at the age of 5 year and elder. Males prevail in the first three age groups, but females dominate in elder groups. The mature fish enter to the spawning grounds in the Tauyskaya Guba Bay in December. The spawning occurs in January-March under the water temperature of -1.5 о C. The saffron cod females spawn 7.2-172.0 thousand eggs, depending on their size, weight, and age (on average 56,600 eggs or 334 eggs per 1 g of body weight). Relative fecundity of the females increases until the age of 7 years, elder females have slightly lower but stable fecundity. The eggs at the beginning of the second stage of development have the diameter of 1.00-1.58 mm, on average 1.410 ± 0.005 mm, and are distinguished by almost transparent shell and colorless yolk, with the ochre colored plasmodisc. The animal pole (were plasmodisc is formed) is in the upper position. A micropyle on the outer shell is clearly visible as a small bulge with diameter slit surrounded by two concentric beads (this structure remains during entire embryogenesis and can be considered as a taxonomic sign of the species rank). Under the incubation temperature of 2.8 о C, the eggs reach the stage of two blastomeres in 11-12 h. At the first stages of partition, numerous small fat-like inclusions are visible in the blastomeres. The second and third cycles of the zygote division with forming of 4 and 8 blastomers pass in the age interval 14-18 h. The interphase between divisions increases from 3 h between the first and second divisions to 5 h between further divisions. The eggs reach the early stage III (large cell blastula) and late stage III (small cell blastula) after 30 and 41 h of their development, respectively. By the end of the stage III, the dome of blastula is maximally developed. At the age of 75 h, the stage of gastrulation and epiboly begins. The blastoderm covers 50-60 % of the yolk surface after 123 h. Bead-shaped embryo is formed after 177 h of development. In the next 309, 417, 459 h of incubation, the embryos undergo successively the stages of tail separation from the yolk sac, mobility beginning, and heart functioning. In experiments, prelarvae of saffron cod hatched after 849 h of incubation. Their size in the Tauyskaya Guba population is the largest known in scientific literature: the total body length varies from 5.30 to 6.25 mm (on average 5.82 ± 0.05 mm); besides, they are distinguished by greater number of pigment cells on the yolk sac and nearby. Intensive pigmentation of prelarvae is known for other fish species in the northern Okhotsk Sea, as well, that presumably is their adaptation for better accumulation of solar heat in conditions of late spring warming in this area.

Uptake and tissue distributions of cadmium, selenium and zinc in striped marsh frog tadpoles exposed during early post-embryonic development

Metals and metalloids released through anthropogenic activities can accumulate in aquatic organisms, resulting in adverse effects in sensitive species. We investigated the influence of feeding regime and exposure complexity (i.e., mixture) on bioaccumulation kinetics and body distribution of common metal(loid) pollutants in Limnodynastes peronii during early post-embryonic development. Tadpoles were exposed to radiolabelled 109Cd, 75Se and 65Zn alone and in a mixture for 4 days, followed by 3 days depuration in clean water. One group was fed directly in exposure aquaria, whereas a second group was transferred to clean water for feeding, to investigate the potential influence of sorption to food on uptake. Bioconcentration factor and retention was observed to be greatest for Se. Results demonstrate that tadpoles accumulated and retained half the amount of Cd when exposed in mixture, suggesting that Se and/or Zn may have antagonistic effects against Cd uptake. Additionally, tadpoles fed directly in exposure water accumulated 2–3–times more Cd and Zn compared to tadpoles fed in clean water, indicating that the presence of food particles is an important factor that may influence uptake. Interestingly, this had a negligible impact on Se uptake. The study reveals how exposure conditions can influence the bioaccumulation of metal(loid)s, highlighting experimental factors as important considerations for both controlled toxicity experiments and for understanding exposure risks for amphibian populations.

Ecological role of lipids and fatty acids in the early postembryonic development of the daubed shanny, Leptoclinus maculatus (Fries, 1838) from Kongsfjorden, West Spitsbergen in winter

The dynamics of lipid and fatty acid composition of the muscles (flesh) and lipid sac in L. maculatus early life stages of different age collected in Kongsfjorden (Svalbard, Norway), in winter, during the polar night was studied. We showed that the total lipid content in the muscles increases on account of energetic triacylglycerols derived from the lipid sac, which is resorbed in juveniles as they switch to a demersal mode of life. The fatty acid spectrum directly reflects age-dependent and seasonal features of L. maculatus early life stages. The results of the study elucidate the specific role of lipids and fatty acids in the ecological and biochemical mechanisms related to ontogenic development of fish from the family Stichaeidae, particularly arctic-boreal L. maculatus, which assumed to become increasingly frequent in the Spitsbergen water area. They are important for understanding the ability of organisms to maintain and preserve the functional stability of ecosystems as a whole, especially under conditions of climate change in the Arctic.

Morphological variability of pond smelt Hypomesus olidus (Osmeridae) from some water bodies of the Far East

Morphological variability of four characters in 13 samples of pond smelt Hypomesus olidus is investigated using three parameters: fluctuating asymmetry, geographic variability, and variability of characters. The differences in the level of fluctuating asymmetry in H. olidus from various water bodies of the Far East and, thus, in the stability of development depend on the differences in conditions of embryonic and early postembryonic development. Only one character of four (mean number of soft rays in pectoral fins) shows presence of geographic variability in smelt: the mean value of this character increase from north to south. Estimation of variability of characters demonstrates that the maximum fluctuations of the variation coefficient are characteristic of the number of infraorbital bones and the minimal fluctuations are characteristic of the number of soft rays in pectoral fins.