Pyloric Caeca Research Articles

Genome erosion and evidence for an intracellular niche – exploring the biology of mycoplasmas in Atlantic salmon

Mycoplasmas are the smallest autonomously self-replicating life form on the planet. Members of this bacterial genus are known to parasitise a wide array of metazoans including vertebrates. Whilst much research has been significant targeted at parasitic mammalian mycoplasmas, very little is known about their role in other vertebrates. In the current study, we aim to explore the biology of mycoplasmas in Atlantic Salmon, a species of major significance for aquaculture, including cellular niche, genome size structure and gene content. Using fluorescent in-situ hybridisation (FISH), mycoplasmas were targeted in epithelial tissues across the digestive tract (stomach, pyloric caecum and midgut) from different development stages (eggs, parr, subadult) of farmed Atlantic salmon (Salmo salar), and we present evidence for an intracellular niche for some of the microbes visualised. Via shotgun metagenomic sequencing, a nearly complete, albeit small, genome (~0.57 MB) as assembled from a farmed Atlantic salmon subadult. Phylogenetic analysis of the recovered genome revealed taxonomic proximity to other salmon derived mycoplasmas, as well as to the human pathogen Mycoplasma penetrans (~1.36 Mb). We annotated coding sequences and identified riboflavin pathway encoding genes and sugar transporters, the former potentially consistent with micronutrient provisioning in salmonid development. Our study provides insights into mucosal adherence, the cellular niche and gene catalog of Mycoplasma in the gut ecosystem of the Atlantic salmon, suggesting a high dependency of this minimalist bacterium on its host. Further study is required to explore and functional role of Mycoplasma in the nutrition and development of its salmonid host.

Characterization of amylase and protease activity in the digestive tract of two teleosts (Labeo rohita and Anabas testudineus) with different feeding habits

Two teleosts (Rohu, Labeo rohita and Koi, Anabas testudineus), both with contrasting feeding habits (herbivorous versus carnivorous) were studied for amylase and protease activity concerning different regions of their digestive tracts. Significant differences in enzymatic activity across different regions of the digestive tracts were observed. Rohu, with three equal regions of the stomachless gut, showed the highest amylolytic activity at the posterior digestive tract but the highest proteolytic activity is limited to mid region. Contrary to such observation, Koi with three distinct regions of the digestive tract (stomach, pyloric caeca and intestine), the pyloric caeca exhibited the highest specific activity for both amylase and total protease. The optimum pH and temperature conditions were determined concerning the activity for both amylase and protease.

Two new species of snailfishes of the genus emCareproctus/em (Cottoidei: Liparidae) from the western North Pacific Ocean with a range extension of emCareproctus brevipectoralis/em.

Three snailfish species of Careproctus (Cottoidei: Liparidae), including two new species, are described from the deep Pacific Ocean off northern Honshu Island, Japan. Careproctus cyanogladius sp. nov., collected from the depths of 2,698-3,223 m, can be distinguished from congeneric species by having the following combination of characters: vertebrae 63; dorsal-fin rays 57-58; anal-fin rays 50; principal caudal rays 7; pectoral-fin rays 29-31; pectoral fin without a notch; uppermost pectoral-fin base below a horizontal through posterior margin of maxillary; pelvic disk oval; chin pores well separated; teeth simple; pyloric caeca 6-10; body pale blue or gray when fresh. The other new species, Careproctus orri sp. nov., collected from depths of 640-808 m, can be distinguished from congeneric species by having the following combination of characters: vertebrae 58-60; dorsal-fin rays 52-53; anal-fin rays 47-49; pectoral-fin rays 34-35; pectoral fin with a distinct notch; cephalic pores 2-6-7-2, chin pores single, unpaired; gill slit extending ventrally to 5th or 6th pectoral-fin ray; teeth strongly trilobed; peritoneum dark, stomach white. In addition, one specimen of Careproctus brevipectoralis Chernova, Thiel Eidus, 2020 was newly collected from Japan, and is redescribed here in detail with comments on intraspecific variations.

Isolation of a starfish myorelaxant peptide (SMP) isotype from the pyloric caeca of Patiria pectinifera

Peptides are naturally occurring biological molecules that are found in all living organisms. These biologically active peptides play a key role in various biological processes. The aim of this study is the extraction and the purification of bioactive materials that induce relaxation of an apical muscle from the pyloric caeca of Patiria pectinifera. The acidified pyloric caeca extract was partially separated by the solid phase extraction using a stepwise gradient on Sep-Pak C18 cartridge. Among the fractions, materials eluted with 60% methanol/0.1% trifluoroacetic acid was put a thorough of a series of high performance liquid chromatography (HPLC) steps to isolate a neuropeptide with relaxation activity. The purified compound was eluted at 28% acetonitrile in 0.1% trifluoroacetic acid with retention time of 25.8 min on the CAPCELL-PAK C18 reversed-phase column. To determine the molecular weight and the amino acid sequence of the purified peptide, LC-MS and Edman degradation method were used, respectively. The primary structure of the peptide was determined to be FGMGGAYDPLSAGFTD which corresponded to the amino acid sequence of a starfish myorelaxant peptide (SMP) isotype (SMPb) found in the cDNA sequence encoding SMPa and its isotypes. In this study, a muscle relaxant neuropeptide (SMPb) has been isolated from pyloric caeca of starfish P. pectinifera. This is the first report of SMPb isolation on the protein level from P. pectinifera.

Saponin contents in the starfish Echinaster sepositus: Chemical characterization, qualitative and quantitative distribution

In this study, we report the inter-organ, the sexual and the seasonal variability, of saponins contained in the common Mediterranean starfish Echinaster (Echinaster) sepositus. Saponins were extracted from five distinct body components namely the stomach, the pyloric caeca, the gonads, the oral body wall and aboral body wall. Of both sexes (males and females) collected at different seasons, the saponins mixtures were analyzed by Mass spectrometry (HR-ESI-MS and HR-ESI- MS/MS). Semi-quantitative approach was performed to estimate the variability of the saponin amounts. Our results demonstrated that the diversity of saponins in E. sepositus is higher than previously reported. We highlighted 11 different saponins, including 9 new congeners. Presumptive molecular structures are proposed for 6 molecules on the basis of key-fragmentations identified by HR-ESI-MS/MS. The comparison of the saponin contained in the five different body components revealed that minimum 3 saponins are common in all tissues. In addition, qualitative and quantitative variability of saponins compounds were linked to the organ, sex and the collecting season. The relative highest level of saponins was found in the stomach on the period of active feeding (winter). The significant higher levels of saponins were found in the gonads and oral body wall on the spawning period (summer). Generally, a great inter-organ, sexual and seasonal variability was found in both sexes. These results suggest that saponins probably fulfill several biological functions in E. sepositus.

In vitro evaluation of novel (nanoparticle) oral delivery systems allow selection of gut immunomodulatory formulations

Oral delivery is the most convenient way to vaccinate cultured fish, however it is still problematic, primarily due to a lack of a commercially valid vaccine vehicle to protect the antigen against gastric degradation and ensure its uptake from the intestine. With the goal of advancing the potential to vaccinate orally, this study evaluates a novel silicon nanoparticle-based vehicle (VacSaf carrier). Aeromonas salmonicida antigens were formulated with the VacSaf carrier using different preparation methods to generate dry powder and liquid formulations. Twelve formulations were first subjected to an in vitro evaluation where the A. salmonicida bacterin conjugated to VacSaf carriers were found superior at inducing pro-inflammatory cytokine expression in primary leucocyte cultures and the macrophage/monocyte cell line RTS-11 compared with A. salmonicida bacterin alone. This was especially apparent after exposure to acid conditions to mimic stomach processing. One formulation (FD1) was taken forward to oral delivery using two doses and two administration schedules (5 days vs 10 days, the latter 5 days on, 5 days off, 5 days on), and the transcript changes of immune genes in the intestine (pyloric caeca, midgut and hindgut) and spleen were evaluated by qPCR and serum IgM was measured by ELISA. The VacSaf carrier alone was shown to be safe for use in vivo, in that no side-effects were seen, but it did induce expression of some cytokines, and may have value as an oral adjuvant candidate. The FD1 bacterin formulation was effective at inducing a range of cytokines associated with innate and adaptive immunity, mainly in the pyloric caeca, compared to A. salmonicida bacterin alone (which had almost no effect), and confirms the immune competence of this gut region following appropriate oral vaccination. These results reveal that in vitro screening of formulations for oral delivery has value and can be used to assess the most promising formulations to test further.

Morphological changes of pyloric caeca and their relevancy to motility in laboratory-reared Kurosoi rockfish (Sebastes schlegelii Hilgendorf), using an in vitro assay method

Artificial diets affect the growth and gut morphology of carnivorous fishes. In this study, we compared a laboratory raised rockfish, Sebastes schlegelii (a carnivore), fed an artificial diet (Lab fish), and the wild-captured rockfish (Wild fish) to confirm the effect of an artificial diet on pyloric caecal morphology and motility. We also established an in vitro method to quantify pyloric caecal sac motility and compared it between Lab and Wild fish. The pyloric caecal length per unit body length, the pyloric caecal weight per unit body weight, and the pyloric caecal weight per length were significantly greater in the Wild fish than in the Lab fish. Additionally, both of the circular and longitudinal muscularis layers were significantly thicker in the Wild fish than in the Lab fish. The pyloric caecal motor frequency of the Wild fish was higher than that in the Lab fish, but the contractile pressure of the pyloric caeca did not change under conventional conditions. These results suggest that the thickness of the tunica muscularis of the pyloric caeca may be involved in its motility, and the pyloric caeca of the Lab fish may not be able to provide functionality in this respect. In conclusion, under artificial rearing conditions, the artificial diet reduced the thickness of the tunica muscularis and reduced the motor frequency of the pyloric caeca in rockfish.

Characterization of digestive physiology in Pacific bluefin tuna Thunnus orientalis juveniles fed a raw fish feed and a commercial diet

This study examined the biochemical characteristics of key digestive enzymes in artificially produced Pacific bluefin tuna juveniles and revealed details of the digestive physiology of juveniles fed a commercial pellet diet and raw fish over long-term (225 days) and short-term (response to feeding) periods. pH and thermal profiles of key digestive enzymes of pepsin, trypsin, chymotrypsin, lipase and amylase were examined in juvenile bluefin tuna and the characteristics differed from those previously reported for larval and adult tuna. Long-term feeding (225 days) of the commercial diet markedly increased stomach and pyloric caeca size as well as storage/synthesis levels of the digestive enzymes. Highly increased gene expression levels of cholecystokinin (cck) and its receptor (cck1r) were also found in juveniles fed the commercial diet, suggesting cck might be involved in the gastrointestinal hypertrophy and digestion enhancement seen in the present study. In the short-term experiment (response to feeding), juveniles fed the commercial diet displayed faster gastric emptying, higher pH in the intestinal content and increased digestive enzymes storage/synthesis whereas the enzymes secretion was similar with those of juveniles fed raw fish. These indicate that juvenile bluefin tuna morphologically and physiologically adapted their digestive system to the artificial diet, however the adaptation was not sufficient to obtain a comparable performance as tuna fed raw fish feed. Biochemical characteristics of the digestive enzymes and the observed effects of artificial diet on digestive physiology could be good indicators to improve feeding strategies such as diet composition, feeding ration and frequency in juvenile tuna.

Dietary Inclusion of Black Soldier Fly (Hermetia Illucens) Larvae Meal and Paste Improved Gut Health but Had Minor Effects on Skin Mucus Proteome and Immune Response in Atlantic Salmon (Salmo Salar).

The present study investigated effects of dietary inclusion of black soldier fly larvae (BSFL) (Hermetia illucens) meal and paste on gut health, plasma biochemical parameters, immune response and skin mucus proteome in pre-smolt Atlantic salmon (Salmo salar). The seven-week experiment consisted of seven experimental diets: a control diet based on fishmeal and plant protein (Control-1); three BSFL meal diets, substituting 6.25% (6.25IM), 12.5% (12.5IM) and 25% (25IM) of protein; two BSFL paste diets, substituting 3.7% (3.7IP) and 6.7% (6.7IP) of protein and an extra control diet with 0.88% of formic acid (Control-2). The 6.25IM diet reduced enterocyte steatosis in pyloric caeca, improved distal intestine histology, and reduced IgM in distal intestine. The fish fed 12.5IM diet reduced enterocyte steatosis in pyloric caeca, improved distal intestine histology, had a higher plasma lysozyme content compared to 6.25IM, and tend to increase phagocytic activity in head-kidney macrophages-like cells. On the other hand, 25IM diet improved distal intestine histology, but showed mild-moderate enterocyte steatosis in pyloric caeca, increased IFNγ and reduced IgM in distal intestine. In the case of BSFL paste diets, 3.7IP diet caused mild inflammatory changes in distal intestine, although it reduced enterocyte steatosis in pyloric caeca. The 6.7IP diet reduced enterocyte steatosis in pyloric caeca and improved distal intestine histology. Increasing level of BSFL meal in the diet linearly decreased plasma C-reactive protein, whereas increasing level of BSFL paste linearly increased plasma antioxidant capacity. Dietary inclusion of BSFL meal and paste had minor effects on the expression profile of proteins in skin mucus and no effects on immune markers in splenocytes. BSFL meal showed no negative effect on liver and muscle health as indicated by plasma alanine aminotranseferase, asparate aminotransferase and creatine kinase. The present study showed that replacing conventional protein sources with low to moderate levels of BSFL meal (6.25% and 12.5%) or paste (3.7% and 6.7%) reduced enterocyte steatosis in pyloric caeca, while replacing up to 25% with BSFL meal or 6.7% with paste improved distal intestine histology. Further, dietary inclusion of BSFL meal and paste had minor effects on skin mucus proteome and immune response in Atlantic salmon.

Black Soldier Fly Full-Fat Larvae Meal is More Profitable than Fish Meal and Fish Oil in Siberian Sturgeon Farming: The Effects on Aquaculture Sustainability, Economy and Fish GIT Development.

Simple SummaryThe practical use of alternative feed materials must be both sustainable and profitable. Therefore, the aim of this study was to assess the impact of black soldier fly full-fat larvae meal (BSFL) on environmental and economic aspects as well as gastrointestinal tract (GIT) development in Siberian sturgeon nutrition. The experimentally obtained data were used for calculations of fish meal (FM) and fish oil (FO) relative usage per kg of fish gain. The economic conversion ratio and profitability per unit of fish gain were assessed also. The samples of intestinal and liver tissues were analysed in terms of villi height, width, and surface, and liver health. The study showed a high potential of BSFL usage up to its highest used incorporation that was 30% of the diet. The environmental sustainability of the diets was increased not only by the reduction in FM and FO use but also by the increase in feed conversion efficiency. Thus, even though the price of BSFL was higher than FM and FO, the profitability of fish production was improved, finding its optimum at the levels of 10% and 15% BSFL incorporation. Moreover, health beneficial effects of BSFL were observed in alterations of GIT development.This study provides data on the environmental sustainability, economic profitability, and gastrointestinal tract development of Siberian sturgeon diets containing black soldier fly full-fat larvae meal (BSFL) for a fish meal (FM) and fish oil (FO) replacement. BSFL was used at 5%, 10%, 15%, 20%, 25%, and 30% of the diet, replacing by up to 61.3% of FM and 95.4% of FO. BSFL positively affected the feed efficiency ratio, and lowered FM and FO usage per kg of fish gain. All the BSFL diets showed a sustainable fish-in fish-out (FIFO) ratio, which was lowered by up to 75% in comparison to the control. Economic assessment per kg of fish gain showed that the most lucrative variants were variants with 10% and 15% BSFL, it finds a mode of action in improvements of the gastrointestinal tract development, including increased pyloric caeca and proximal intestine shares and enhanced villus height and area. Thus, in Siberian sturgeon, BSFL may be used not only as an FM and FO replacer but also as a functional material due to its feed utilization and beneficial health effects, which are reflected in its high sustainability and favourable economics.

Revision of the resurrected deepwater scorpionfish genus Lythrichthys Jordan and Starks 1904 (Setarchidae), with descriptions of two new species

Lythrichthys Jordan and Starks 1904 (Setarchidae), previously regarded as a junior synonym of Setarches Johnson 1862, is recognized as valid, despite sharing some diagnostic characters with the latter, both genera differing from others in the family in having III, 4–6 (usually 5) anal-fin rays, the body depth at the pelvic-fin origin and interorbital width at the vertical midline of the eye 29.1–42.9% and 7.4–12.9% of standard length, respectively, snout, dorsal and ventral surface of the head naked, first lacrimal spine well developed and of similar length to the second and third spines, intestine and pyloric caeca black or grey, and swimbladder well developed. Lythrichthys differs from Setarches in having the second preopercular spine short or rudimentary (vs. well developed, of similar length to the first and third spines in Setarches), the thoracic and abdominal scales embedded (vs. exposed), the tip of the first lacrimal spine reaching the upper lip (vs. not reaching, except in juveniles), and 9 abdominal vertebrae (vs. 10). In addition, examination of all nominal species included in Setarchidae showed that five were best placed in Lythrichthys, viz. Lythrichthys longimanus (Alcock 1894), Lythrichthys eulabes Jordan and Starks 1904, Lythrichthys cypho (Fowler 1938), Lythrichthys dentatus sp. nov. and Lythrichthys grahami sp. nov., with Setarches including only Setarches guentheri Johnson 1862.

Cortisol affects feed utilization, digestion and performance in juvenile rainbow trout (Oncorhynchus mykiss)

To quantify bioenergetic consequences of chronically or acutely elevated plasma cortisol levels, growth rates, feed conversion ratios and digestive performance was investigated in juvenile rainbow trout (Oncorhynchus mykiss) reared at 15 °C. Plasma cortisol levels were elevated using coconut oil based implants. A sham group received coconut oil without cortisol, (S), while a low (LC) and high (HC) cortisol group received implants containing 30 or 60 μg cortisol g−1 fish. An additional group of fish was reared under moderate thermal stress (22 °C, TS), while acute increases in plasma cortisol were achieved by subjecting fish to a daily stressor by chasing (DS). An undisturbed treatment group, reared at 15 °C served as control (C). Although feed intake was not affected by treatments, cortisol treated fish showed reduced growth rate and feed conversion efficiency compared to all other treatments. This was caused, in part, by impaired digestibility of protein, lipids and nitrogen free extract in the HC treatment, leading to a decrease in available metabolizable energy. The observed decrease in lipid digestibility did not appear to be caused by a reduced digestive lipase activity in the pyloric caeca and anterior intestine as this was not significantly different between treatments 90 min after feeding. Chronically elevated cortisol levels led to atrophy of the digestive system revealed by a loss in tissue mass of the intestine and pyloric caeca in the high cortisol treatment, as well as an overall decrease in viscerosomatic index. In addition, the energetic cost of growth was higher in both cortisol treated groups compared to all other treatments. The chronic temperature elevation resulted in improved lipid digestion compared to the control treatment, while growth performance was impaired, however apparently not correlated with elevated plasma cortisol levels. A moderate random daily stress event did not result in any changes of the studied parameters. The results obtained suggest both an atrophic effect of chronically elevated plasma cortisol levels on digestive tissues resulting in impaired nutrient assimilation, less available metabolizable energy, and an increased routine energy expenditure, leading to a higher cost of growth.

Histological variations and adaptability in some digestive organs of the thinlip grey mullet, Chelon ramada (Risso, 1827)

The objective of the present study was to explain the histological variations in the pyloric caeca and anterior intestine of Chelonramada.For this purpose, small pieces of the target organs were attained from specimens ofC.ramada: for histological and histochemical procedures. The final sections were examined under a microscope, photographed and described. Histologically, serosa, muscularis, submucosa, and mucosae are the main layers of the wall of pyloric caeca and anterior intestine in C.ramada indicating there are no remarkable differences in the basic structure. The mucosal folds of pyloric caeca are thin and deeply folded in a narrow lumen; in contrast, the mucosal folds of the anterior intestine are long protruding at a wide lumen. The mucosal layer of the anterior intestine is consisted of columnar and mucus cells as in the pyloric caeca, but mucous cells are numerous in number at the anterior intestine while it observed in fewer numbers at the mucosal layer of the pyloric caeca. In submucosal and mucosal layers, wandering cells and lymphocytes are plentiful especially among the columnar cells of the anterior intestine. These cells are more abundant in the anterior intestine than that observed in pyloric caeca; in contrast with the number of blood vessels. The present study concluded that the distribution and secretions of the mucosa are very clear with histochemical stains. This study is helpful for understanding the digestive physiology and the related functional mechanisms of fish digestion.

Immunohistopathological response against anisakid nematode larvae and a coccidian in Micromesistius poutassou from NE Atlantic waters.

A survey on Anisakis simplex (sensu stricto (s.s.)) from blue whiting, Micromesistius poutassou, in the north-eastern Atlantic Ocean revealed the occurrence of high infection levels of third larval stages in visceral organs and flesh. Larvae were genetically identified with a multilocus approach as A. simplex (s.s.). Histochemical, immunohistochemical and ultrastructural observations were conducted on 30 M. poutassou specimens. Gonads, pyloric caeca and flesh harboured encapsulated larvae of A. simplex (s.s.) but no intense host reaction was encountered around the parasite in the above organs. In the liver, the most infected organ, the larvae co-occurred with the coccidian Goussia sp. Within the granuloma around the A. simplex (s.s.) larvae, two concentric layers were recognized, an inner mostly comprising electron-dense epithelioid cells and an outer layer made of less electron-dense epithelioid cells. Macrophages and macrophage aggregates (MAs) were abundant out of the granulomas, scattered in parenchyma, and inside the MAs, the presence of engulfed Goussia sp. was frequent. In liver tissue co-infected with Goussia sp. and A. simplex (s.s.), hepatocytes showed cytoplasmic rarefaction and acute cell swelling. Results suggest that the host-induced encapsulation of A. simplex (s.s.) larvae is a strategic compromise to minimize collateral tissue damage around the larval infection sites, to facilitate the survival of both parasite and host.

Effect of raw and artificial feed on morphology of pyloric caeca in cultured Pacific bluefin tuna Thunnus orientalis

Effect of raw and artificial feed on morphology of pyloric caeca in cultured Pacific bluefin tuna <I>Thunnus orientalis</I>

Does ecological release from distantly related species affect phenotypic divergence in brook charr?

Ecological opportunity occurs when a resource becomes available through a decrease of interspecific competition and another species colonizes the vacant niche through phenotypic plasticity and intraspecific competition. Brook charr exhibit a resource polymorphism in some Canadian Shield lakes, where a littoral ecotype feeds mainly on zoobenthos and a pelagic ecotype feeds mostly on zooplankton. The objectives of this study were to test that (i) resource polymorphism is common in these brook charr populations, (ii) the presence creek chub and white sucker, two introduced species competing with brook charr for littoral resources, will decrease the phenotypic divergence between the two brook charr ecotypes, and (iii) the ecological release from introduced species will increase population and/or individual niche widths in brook charr. The study was based on 27 lakes and five indicators of resource use (stomach content, liver δ13C, muscle astaxanthin concentration, pyloric caecum length, and gill raker length). Our results indicate that within-lake differences in resource use by both ecotypes are common and stable through time. When facing interspecific competition, both littoral and pelagic brook charr incorporated more pelagic prey into their diet but maintained the amplitude of their differences in resource use, which contradicts our second prediction. Finally, we did not find any significant effect of introduced species on population and individual niche widths of brook charr. We suggest that the difference in feeding mode among distantly related competitors could prevent the complete exclusion of a species from a given niche and explain the lack of response to the ecological release.

Comparative study on the histochemical structures of stomach, pyloric caeca and anterior intestine in the grey mullet, Mugil cephalus (Linnaeus, 1758)

The purpose of this study was to compare the histological features of pyloric caeca with that of the stomach and anterior intestine in Mugil cephalus. Specimens of M. cephalus were dissected and small pieces of each part were cut, fixed for routine histological procedures. The transverse sections were also stained by some stains for histochemical purposes. These sections were examined under a microscope, photographed, and described. Histologically, the wall of the stomach, pyloric caeca, and anterior intestine in Mugil cephalus mainly consists of serosa, muscular, submucosa, and mucosa. While the stomach and pyloric caeca have deeply mucosal folds in a narrow lumen, the anterior intestine has a long mucosal fold protruding towards the wide lumen. The mucosa of the three organs consists of columnar cells and mucus cells; in addition to gastric glands in the proventriculus stomach only. The columnar cells at the gizzard stomach are lined toward the lumen with a continuous koillin layer. The mucus cells are medium in size and numbers at the anterior intestine and less at pyloric caeca, but it absent from the stomach. Lymphocytes and wandering cells are abundant in between columnar cells and in the submucosal layer. Histochemical differences between these three digestive organs were also studied and described.

The current state of molecular genetic research on the taxonomic diversity of the enteric microbiota of Siberian fish

This paper presents the current state of research on the intestinal microbiota of fish of different ecological groups from water bodies of West and East Siberia. The present study focused on the gut bacterial diversity of 16 species/forms of fish (due to intricate taxonomical position of whitefish from Teletskoye Lake) inhabiting Chany Lake (Novosibirsk oblast), Teletskoye Lake (Altai Republic), Baikal Lake and other water bodies of East Siberia using molecular genetic methods. The analysis of the conducted studies shows the main features of gut bacterial communities in the digestive tract of fish and to better understand the features of the functioning of aquatic ecosystems in Siberia. In all studied fish (except for Lena grayling and Baikal omul), regardless of their habitat, taxonomy, digestive system structure (presence or absence of stomach and pyloric caeca) and feeding habits, bacteria of all four phyla (Proteobacteria, Bacteroidetes, Firmicutes, and Actinobacteria) were found among the dominants. Such differences can also be explained by sample preparation techniques before sequencing that researchers may apply. Also, the uncultivated microbiota such as Pseudoalteromonadaceae (Lake Chany), Comamonadaceae and Bacillaceae (whitefish from Lake Teletskoye) and Rhodobacteraceae (Baikal omul and whitefish) were often found among the dominant bacterial taxa in the digestive tract of the most studied fish. Moreover, the data focused on the structure of gut bacterial community of fish will be useful for the development of aquaculture industry in the region, since the information makes it possible to identify pathogenic, opportunistic, and probiotic bacteria in aquatic ecosystems.

Walleye pollock Gadus chalcogrammus Pallas, 1814 found north of Spitsbergen indicates a Pacific-Atlantic connection in the species

A small (36.5 cm) female walleye pollock Gadus chalcogrammus Pallas, 1814 was caught north of Spitsbergen in2011. The specimen had a high number of pyloric caeca (n=109), indicating a Pacific origin. The record is the firstevidence of a possible input to the small Atlantic population of walleye pollock from the large populations on thePacific side.

Does the thermal component of warm water treatment inflict acute lesions on Atlantic salmon (Salmo salar)?

Warm water treatment, i.e. exposure to sea water at a temperature of 28–34 °C for 20–30 s, has in recent years been widely used for delousing of Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss) in Norwegian aquaculture. High mortality and various lesions (e.g. injuries and/or bleedings in skin, fins, eyes, brain, and gills) have, however, been reported after industrial warm water treatments. The objective of this study was to reveal whether the thermal component of warm water treatment inflicts acute lesions on Atlantic salmon. The study was conducted by exposing individual, sedated Atlantic salmon post-smolts (w¯ = 1117 ± 250 g) to sea water at a temperature of 34 °C (warm water treatment, n = 40) or 9 °C (control treatment, n = 20) for 30 s, and subsequently conducting welfare indicator scoring and histopathological examination of their skin, fins, eyes, snout, nasal pits/mucosa, palate, gills, thymus, pseudobranch, brain, heart, liver, kidney, pyloric caeca, pancreas, and spleen. The results showed that the prevalence and severity of acute lesions were not significantly different between the two treatment groups, except for higher prevalence of injuries on the caudal (p = 0.002), dorsal (p = 0.002), and right pelvic fins (p = 0.014) in the warm water treatment group. The main cause of these fin injuries may have been a strong behavioural reaction displayed by the fish when exposed to warm water. Possible consequences of fin injuries, the use of anaesthetic, and statistical limitations were discussed. It was concluded that exposure of Atlantic salmon to sea water at a temperature of 34 °C for 30 s did not lead to any statistically significant change in the prevalence of acute lesions except an increase in minor, possibly behaviour-related, fin injuries. Detection of a lower lesion prevalence than was possible in this study, but which may concern many individuals in an industrial setting, requires examination of a larger number of fish.