Deciphering taxonomic and functional patterns of microbial communities associated with the tiger tail seahorse (Hippocampus comes).

Gaining insight into the diversity, structure, and metabolic functions of microbial communities is essential for understanding their roles in host health and ecosystem dynamics. However, research on the seahorse-associated microbiome remains limited, despite these threatened fish facing increasing human pressures worldwide. Here, we explored the microbial diversity and metabolic functions of the skin and gut of the tiger tail seahorse (Hippocampus comes) and its surrounding environment using shotgun metagenomics and bioinformatics. Members of the Pseudomonadota phylum were dominant in the skin microbiome, whereas Bacteroidota was dominant in the gut. Bacillota, Actinomycetota, and Planctomycetota were also detected in the seahorse-associated microbiome. Statistical analysis revealed significant differences (P < 0.01) in species diversity between skin and gut microbiomes, with members belonging to the Moraxellaceae family being dominant on the skin and the Bacteroidaceae family in the gut. Moreover, the surrounding environment (water or sediment) did not have a direct effect on the seahorse microbiome composition. The skin microbiome exhibited a higher abundance of functional genes related to energy, lipid, and amino acid metabolism as well as terpenoids and polyketides metabolism, xenobiotics biodegradation, and metabolism compared with the gut. Despite differences among classes, the total abundance of bacteriocins was similar in both gut and skin microbiomes, which is significant in shaping microbial communities due to their antimicrobial properties. A better knowledge of seahorse microbiomes benefits conservation and sustainable aquaculture efforts, offering insights into habitat protection, disease management, and optimizing aquaculture environments, thereby promoting seahorse health and welfare while minimizing environmental impact and enhancing aquaculture sustainability.NEW & NOTEWORTHY To the best of our knowledge, this study represents the first comprehensive examination of the taxonomic and functional patterns of the skin and gut microbiome in the tiger tail seahorse. These findings have the potential to significantly enhance our understanding of the seahorse-associated microbiome, thereby contributing to the prediction and control of bacterial infections in seahorses, which are a leading cause of high mass mortality rates in seahorse aquaculture and other fish species.

Application of oil-in-water nanoemulsions based on grape and cinnamon essential oils for shelf-life extension of chilled flathead mullet fillets.

BACKGROUND: The effect of nanoemulsions prepared with grape seed and cinnamon essential oils on the shelf-life of flathead mullet (Mugil cephalus) fillets was evaluated by determining physicochemical (pH, free fatty acids, peroxide value, total volatile base nitrogen (TVB-N), and thiobarbituric acid reactive substances (TBARs)), sensory and microbiological (mesophilic aerobic bacteria, total psychrophilic bacteria, and Enterobacteriaceae counts) properties during 14 day storage at 2 °C. RESULTS: The nanoemulsions showed good stability and low average droplet size. The results indicated that nanoemulsion treatments significantly prolonged the shelf-life of the fillets. Treatment inhibited increases in pH and TVB-N, and retarded lipid oxidation and hydrolysis. Sensory assessment revealed that treatment induced shelf-life extension from 10 to 14 days, compared with controls. Microbiological analyses showed nanoemulsion treatment caused shelf-life extension from 10 to 12 days with reduction of microbiological contamination by up to 1 log cfu g-1 in mesophilic and 1.5 log cfu g-1 in psychrotrophic bacteria. CONCLUSION: Considering the results, grape seed and cinnamon essential oil nanoemulsions could be considered as novel antimicrobial and antioxidant materials for shelf-life extension of flathead mullet fillets during cold storage. © 2021 Society of Chemical Industry.

Amaurones A-K: Polyketides from the Fish Gut-Derived Fungus Amauroascus sp. CMB-F713.

Using a molecular networking guided strategy, chemical analysis of the Australian mullet fish gastrointestinal tract-derived fungus Amauroascus sp. CMB-F713 yielded a family of polyketide pyrones, amaurones A-I (1-9), featuring an unprecedented carbon skeleton. Structures were assigned to 1-9 by detailed spectroscopic analysis (including X-ray analysis of 1), biosynthetic considerations, and chemical interconversions. For example, the orthoacetate 5 was unstable when stored dry at room temperature, transforming to the monoacetates 2 and 3, while mild heating (40 °C) prompted quantitative conversion of 3 to 2, via an intramolecular trans-acetylation. Likewise, during handling, the monoacetate 1 was prone to intramolecular trans-acetylation, leading to an equilibrium mixture with the isomeric monoacetate amaurone J (10), confirmed when partial hydrolysis of the diacetate 2 yielded the monoacetates 1 and 10 and the triol amaurone K (11).

Precursor-Directed Biosynthesis Mediated Amplification of Minor Aza Phenylpropanoid Piperazines in an Australian Marine Fish-Gut-Derived Fungus, Chrysosporium sp. CMB-F214.

Chemical analysis of an M1 agar plate cultivation of a marine fish-gut-derived fungus, Chrysosporium sp. CMB-F214, revealed the known chrysosporazines A-D (11-14) in addition to a suite of very minor aza analogues 1-6. A microbioreactor (MATRIX) cultivation profiling analysis failed to deliver cultivation conditions that significantly improved the yields of 1-6; however, it did reveal that M2 agar cultivation produced the new natural product 15. A precursor-directed biosynthesis strategy adopting supplementation of a CMB-F214 M1 solid agar culture with sodium nicotinate enhanced production of otherwise inaccessible azachrysposorazines A1 (1), A2 (2), B1 (3), C1 (4), C2 (5) and D1 (6), in addition to four new chrysosporazines; chrysosporazines N-P (7-9) and spirochrysosporazine A (10). Structures inclusive of absolute configurations were assigned to 1-15 based on detailed spectroscopic and chemical analyses, and biosynthetic considerations. Non-cytotoxic to human carcinoma cells, azachrysosporazies 1-5 were capable of reversing doxorubicin resistance in P-glycoprotein (P-gp)-overexpressing human colon carcinoma cells (SW620 Ad300), with optimum activity exhibited by the C-2' substituted analogues 3-5.

Altered Intestinal Microbiota Composition Associated with Enteritis in Yellow Seahorses Hippocampus kuda (Bleeker, 1852).

Enteritis comprises one of the most common diseases affecting the survival of farmed yellow seahorse (Hippocampus kuda), an important economic fish species cultured worldwide. Although there are several studies describing bacteria associated with seahorse, the microbial alternations associated with enteritis in seahorse has not been extensively investigated. In the present study, high-throughput 16S rRNA gene sequencing was used to explore the changes in the intestinal microbiota of seahorse suffering from enteritis. The results showed that the diversity, structure, and function of intestinal microbiota were significantly different between healthy and diseased seahorse. Particularly, significant increase was observed in Brevinema, Mycobacterium, and Vibrio, as well as significant decrease in Psychrobacter, Bacillus, and Shewanella in diseased seahorse (P < 0.05). In addition, PICRUSt predictions revealed that the intestinal microbiota significantly changed the specific metabolic pathways (related to metabolic diseases, replication and repair, transport and catabolism, infectious diseases and immune system) in diseased seahorse (P < 0.05). Altogether, our findings point out the association between changes of the intestinal microbiota and enteritis in seahorse, which provide basic information useful for optimization of breeding regimes and improvements in the health of this endangered species in captivity.

Parallel changes in gut microbiome composition and function during colonization, local adaptation and ecological speciation.

The processes of local adaptation and ecological speciation are often strongly shaped by biotic interactions such as competition and predation. One of the strongest lines of evidence that biotic interactions drive evolution comes from the repeated divergence of lineages in association with repeated changes in the community of interacting species. Yet relatively little is known about the repeatability of changes in gut microbial communities and their role in adaptation and divergence of host populations in nature. Here we use three cases of rapid, parallel adaptation and speciation in freshwater threespine stickleback to test for parallel changes in associated gut microbiomes. We find that features of the gut microbial communities have shifted repeatedly in the same direction in association with parallel divergence and speciation of stickleback hosts. These results suggest that changes to gut microbiomes can occur rapidly and predictably in conjunction with host evolution, and that host-microbe interactions might play an important role in host adaptation and diversification.

A manganese superoxide dismutase (MnSOD) from red lip mullet, Liza haematocheila: Evaluation of molecular structure, immune response, and antioxidant function.

Manganese superoxide dismutase (MnSOD) is a nuclear-encoded antioxidant metalloenzyme. The main function of this enzyme is to dismutase the toxic superoxide anion (O2-) into less toxic hydrogen peroxide (H2O2) and oxygen (O2). Structural analysis of mullet MnSOD (MuMnSOD) was performed using different bioinformatics tools. Pairwise alignment revealed that the protein sequence matched to that derived from Larimichthys crocea with a 95.2% sequence identity. Phylogenetic tree analysis showed that the MuMnSOD was included in the category of teleosts. Multiple sequence alignment showed that a SOD Fe-N domain, SOD Fe-C domain, and Mn/Fe SOD signature were highly conserved among the other examined MnSOD orthologs. Quantitative real-time PCR showed that the highest MuMnSOD mRNA expression level was in blood cells. The highest expression level of MuMnSOD was observed in response to treatment with both Lactococcus garvieae and lipopolysaccharide (LPS) at 6 h post treatment in the head kidney and blood. Potential ROS-scavenging ability of the purified recombinant protein (rMuMnSOD) was examined by the xanthine oxidase assay (XOD assay). The optimum temperature and pH for XOD activity were found to be 25 °C and pH 7, respectively. Relative XOD activity was significantly increased with the dose of rMuMnSOD, revealing its dose dependency. Activity of rMuMnSOD was inhibited by potassium cyanide (KCN) and N-N'-diethyl-dithiocarbamate (DDC). Moreover, expression of MuMnSOD resulted in considerable growth retardation of both gram-positive and gram-negative bacteria. Results of the current study suggest that MuMnSOD acts as an antioxidant enzyme and participates in the immune response in mullet.

Characterization of four C1q/TNF-related proteins (CTRPs) from red-lip mullet (Liza haematocheila) and their transcriptional modulation in response to bacterial and pathogen-associated molecular pattern stimuli.

The structural and evolutionary linkage between tumor necrosis factor (TNF) and the globular C1q (gC1q) domain defines the C1q and TNF-related proteins (CTRPs), which are involved in diverse functions such as immune defense, inflammation, apoptosis, autoimmunity, and cell differentiation. In this study, red-lip mullet (Liza haematocheila) CTRP4-like (MuCTRP4-like), CTRP5 (MuCTRP5), CTRP6 (MuCTRP6), and CTRP7 (MuCTRP7) were identified from the red-lip mullet transcriptome database and molecularly characterized. According to in silico analysis, coding sequences of MuCTRP4-like, MuCTRP5, MuCTRP6, and MuCTRP7 consisted of 1128, 753, 729, and 888 bp open reading frames (ORF), respectively and encoded 375, 250, 242, and 295 amino acids, respectively. All CTRPs possessed a putative C1q domain. Additionally, MuCTRP5, MuCTRP6, and MuCTRP7 consisted of a collagen region. Phylogenetic analysis exemplified that MuCTRPs were distinctly clustered with the respective CTRP orthologs. Tissue-specific expression analysis demonstrated that MuCTRP4-like was mostly expressed in the blood and intestine. Moreover, MuCTRP6 was highly expressed in the blood, whereas MuCTRP5 and MuCTRP7 were predominantly expressed in the muscle and stomach, respectively. According to the temporal expression in blood, all MuCTRPs exhibited significant modulations in response to polyinosinic:polycytidylic acid (poly I:C) and Lactococcus garvieae (L. garvieae). MuCTRP4-like, MuCTRP5, and MuCTRP6 showed significant upregulation in response to lipopolysaccharides (LPS). The results of this study suggest the potential involvement of Mullet CTRPs in post-immune responses.

Effects of dietary poly-ß-hydroxybutyrate supplementation on the growth, immune response and intestinal microbiota of soiny mullet (Liza haematocheila).

Soiny mullet (Liza haematocheila) is an important economic fish species in China, but stress and diseases have seriously restricted its culture. There are no effective methods including vaccines to prevent or control these diseases. Alternative methods should be employed, such as using novel immunostimulant poly-ß-hydroxybutyrate (PHB). The present study aimed to evaluate effects of dietary PHB supplementation on the growth, antioxidant enzymes activity, immune-related genes expression and intestinal microbiota in soiny mullet. The fish was fed for 30 or 60 days with six diets at different PHB supplementation of 0, 0.5, 1, 2, 4 and 8%, named as groups P0, P0.5, P1, P2, P4 and P8. The results showed that the weight gain and specific growth rate of fish in P2 and P0.5 groups were significantly higher than those in control P0 group at 30 and 60 days, respectively (P < 0.05). The antioxidant enzymes activity of catalase and superoxide dismutase in serum were significantly increased in P0.5/P1/P2 groups after 30 days. The transcriptional levels of penicillin-binding protein A and interleukin-8 analyzed by qRT-PCR were significantly upregulated in P2 and P4 groups compared to those in P0/P0.5/P1/P8 groups at 30 days. The transcriptional level of major histocompatibility complex class II in P2 group was significantly upregulated, and aldehyde oxidase downregulated compared to P0 group. Intestinal microbiota analysis by Illumina high-throughput sequencing showed that the microbiota diversity was not changed significantly, but the microbiota structure shifted significantly post PHB treatment. At the phyla level, Firmicutes and Proteobacteria were predominant in both P0 and P2 groups. At the genus level, the relative abundance of Bacillus spp. in P2 group increased significantly, and abundance of Achromobacter spp. decreased significantly. KEGG pathway analysis by PICRUSt showed that oral administration PHB significantly upregulated abundances of genes responsible for 10 pathways and downregulated genes involved in 17 pathways. In conclusion, soiny mullet fed with 2% PHB supplemental diets for 30 days showed better growth performance, higher antioxidant enzymes activity and immune-related genes expression. Their regulation of growth and immunity might be related with the intestinal microbiota change post PHB supplementation. It will provide very useful basic information to study the regulation mechanism of PHB in aquatic animals, and provide good green method to prevent disease in soiny mullet.

Characterization of Anti-Listeria monocytogenes Properties of two Bacteriocin-Producing Enterococcus mundtii Isolated from Fresh Fish and Seafood.

This study addressed the bacteriocin production in 116 lactic acid bacteria isolated from 143 fish and seafood samples. The screening for the production of antibacterial substances allowed for the selection of 16 LAB isolates endowed with inhibitory capability. Bacteriocins (bacLP17 and bacLP18) of two strains, Enterococcus mundtii LP17 and Enterococcus mundtii LP18, respectively, isolated from red mullet and sardine samples, determined large inhibition zones against all the Listeria species. Virulence traits and antibiotic resistances of all producers were verified, and no isolates presented dangerous characteristics, including the two best bacteriocin producers E. mundtii LP17 and E. mundtii LP18, which were subsequently investigated for their potential use in fish and seafood products biopreservation. For both strains, the highest level of bacteriocin production (1280 AU/ml) was recorded when cells were grown at 30 °C in MRS broth at pH ranging from 6.0 to 9.0, and high levels of adsorption of bacteriocins, bacLP17 and bacLP18, to the target cells Listeria monocytogenes were also observed. The results obtained in this study revealed that two strains of E. mundtii originating from seafood exhibited a strong inhibitory activity against L. monocytogenes and may be useful in controlling the growth of this pathogen in the same food products.

Mycobacterium syngnathidarum sp. nov., a rapidly growing mycobacterium identified in syngnathid fish.

Two closely related isolates, 27335T and 24999, of rapidly growing, non-pigmented mycobacteria, were cultured from two clinically ill fish of the family Syngnathidae. Whole genome sequencing of the two isolates revealed low sequence homology to documented mycobacteria within public databases such as the NCBI. Evaluation of targeted housekeeping genes, including 16S rRNA, ITS, rpoB and hsp65, related the two bacteria distantly to Mycobacterium senegalense CK2 M4421 and Mycobacterium farcinogenes DSM 43637. Phenotypic, biochemical and dDNA-DNA hybridization tests demonstrated that Mycobacterium syngnathidarum is a new species distinct from other recognized rapidly growing mycobacterial species. Phenotypic, chemotaxonomic and phylogenetic data evaluation provided evidence that the two strains represent one novel species. We propose the formal recognition of Mycobacterium syngnathidarum sp. nov., with isolate 27335T as the type strain (=ATCC TSD-89T,=DSM 105112T).

Aeromonas hydrophila from marketed mullet (Mugil cephalus) in Egypt: PCR characterization of ß-lactam resistance and virulence genes.

AIMS: Aeromonas hydrophila has been isolated from various fish species in Egypt and is known to carry virulence and antimicrobial resistance genes, which pose a risk for public health. The aim of the present study is to report, for the first time, the infection of mullet (Mugil cephalus) with A. hydrophila and to clarify the potential association between antimicrobial resistance and virulence traits encoded in A. hydrophila. METHODS AND RESULTS: In this study, the occurrence of A. hydrophila in marketed mullet and the antimicrobial resistance phenotypes of these isolates were determined. Aeromonas hydrophila isolates were screened for the presence of virulence and ß-lactam resistance genes; the correlation between both gene groups was also investigated. The infection rate of examined mullet with A. hydrophila was 37% (50/135). The highest antimicrobial resistance was detected to cefoxitin (100%), followed by ampicillin (84%), ceftazidime (56%) and cefotaxime (40%). Only 4% of the isolates were resistant to erythromycin; 6% were resistant to both gentamicin and kanamycin with no resistance to ciprofloxacin. Variable frequencies of virulence and ß-lactam resistance genes were evident from PCR, where aerA and blaTEM predominated. The study also indicated a general weak positive correlation (R = 0·3) between both virulence and ß-lactam resistance genes. Some of the studied virulence genes (e.g. aerA:hlyA and hlyA:ast) were found to correlate positively. CONCLUSIONS: The presence of virulence and resistance genes in A. hydrophila from food sources poses a serious threat to public health. To our knowledge, this is the first report describing the occurrence of A. hydrophila in mullet and highlighting the coexistence of virulence and ß-lactam resistance genes encoded by these bacteria. SIGNIFICANCE AND IMPACT OF THE STUDY: These data provide insights into the potential association of antimicrobial resistance and virulence genes in A. hydrophila from marketed mullet in Egypt, which could pose threats to humans even if a weak positive correlation exists between both genes.

Grandparental immune priming in the pipefish Syngnathus typhle.

BACKGROUND: Phenotypic changes in response to environmental influences can persist from one generation into the next. In many systems parental parasite experience influences offspring immune responses, known as transgenerational immune priming (TGIP). TGIP in vertebrates is mainly maternal and short-term, supporting the adaptive immune system of the offspring during its maturation. However, if fathers and offspring have a close physical connection, evolution of additional paternal immune priming can be adaptive. Biparental TGIP may result in maximized immunological protection. Here, we investigate multigenerational biparental TGIP in the sex-role reversed pipefish Syngnathus typhle by exposing grandparents to an immune challenge with heat-killed bacteria and assessing gene expression (44 target genes) of the F2-generation. RESULTS: Grandparental immune challenge induced gene expression of immune genes in one-week-old grandoffspring. Similarly, genes mediating epigenetic regulation including DNA-methylation and histone modifications were involved in grandparental immune priming. While grand-maternal impact was strong on genes of the complement component system, grand-paternal exposure changed expression patterns of genes mediating innate immune defense. CONCLUSION: In a system with male pregnancy, grandparents influenced the immune system of their grandoffspring in a sex-specific manner, demonstrating multigenerational biparental TGIP. The involvement of epigenetic effects suggests that TGIP via the paternal line may not be limited to the pipefish system that displays male pregnancy. While the benefits and costs of grandparental TGIP depend on the temporal heterogeneity of environmental conditions, multigenerational TGIP may affect host-parasite coevolution by dampening the amplitude of Red Queen Dynamics.

Exogenous enzyme complex prevents intestinal soybean meal-induced enteritis in Mugil liza (Valenciennes, 1836) juvenile.

Four soybean meal-based diets containing increasing levels of an enzyme complex (E50, E100, E150 and E200 at 50, 100, 150 and 200 g ton-1, respectively) and one soybean meal-based diet without the enzyme complex (E0) were fed in triplicate to M. liza juveniles in a semi-static flow system with 20 fish per tank for 75 days. There were no differences between the treatments for animal performance parameters, but fish fed the enzyme complex treatment exhibited significantly (P<0.05) higher values of calcium bone retention compared with control fish. Although there was no relationship between bacterial counts in different sections of the gastrointestinal tract or enzyme levels, filamentous bacteria were increased in E50 compared with E150. All of the treatments resulted in higher bacterial counts in the stomach than in intestinal segments. Histological screening showed serious to moderate infiltration of inflammatory cells, modification in villus morphology and necrosis in some cases in fish fed the E0 diet. In addition, fish from the E0 treatment exhibited significantly (P<0.05) lower lipid deposition in the peritoneal cavity. Therefore, the use of low levels of exogenous enzyme is recommended in diets for M. liza when soybean meal is used as the main source of protein.

Transcriptome analysis of soiny mullet (Liza haematocheila) spleen in response to Streptococcus dysgalactiae.

Soiny mullet (Liza haematocheila) is becoming an economically important aquaculture mugilid species in China and other Asian countries. However, increasing incidences of bacterial pathogenic diseases has greatly hampered the production of the soiny mullet. Deeper understanding of the soiny mullet immune system and its related genes in response to bacterial infections are necessary for disease control in this species. In this study, the transcriptomic profile of spleen from soiny mullet challenged with Streptococcus dysgalactiae was analyzed by Illumina-based paired-end sequencing method. After assembly, 86,884 unique transcript fragments (unigenes) were assembled, with an average length of 991 bp. Approximately 41,795 (48.1%) unigenes were annotated in the nr NCBI database and 57.9% of the unigenes were similar to that of the Nile tilapia. A total of 24,299 unigenes were categorized into three Gene Ontology (GO) categories (molecular function, cellular component and biological process), 13,570 unigenes into 25 functional Clusters of Orthologous Groups of proteins (COG) categories, and 30,547 unigenes were grouped into 258 known pathways in the Kyoto Encyclopedia of Genes and Genomes (KEGG) database. Following S. dysgalactiae infection, 11,461 differentially expressed unigenes were identified including 4658 up-regulated unigenes and 6803 down-regulated unigenes. Significant enrichment analysis of these differentially expressed unigenes identified major immune related pathways, including the Toll-like receptor, complement and coagulation cascades, T cell receptor signaling pathway and B cell receptor signaling pathway. In addition, 24,813 simple sequence repeats (SSRs) and 127,503 candidate single nucleotide polymorphisms (SNPs) were identified from the mullet spleen transcriptome. To this date, this study has globally analyzed the transcriptome profile from the spleen of L. haematocheila after S. dysgalactiae infection. Therefore, the results of our study contributes to better on the immune system and defense mechanisms of soiny mullet in response to bacterial infection, and provides valuable references for related studies in mugilidae species which currently lack genomic reference.

Mesonia hippocampi sp. nov., isolated from the brood pouch of a diseased Barbour's Seahorse (Hippocampus barbouri).

An orange-pigmented, Gram-staining-negative, rod-shaped bacterium, designated 96_Hippo_TS_3/13(T) was isolated from the brood pouch of a diseased seahorse male of the species Hippocampus barbouri from the animal facility of the University of Giessen, Germany. Phylogenetic analyses based on the nearly full-length 16S rRNA gene sequence placed strain 96_Hippo_TS_3/13(T) into the monophyletic cluster of the genus Mesonia within the family Flavobacteriaceae. However, the strain shared only 92.2-93.8% sequence similarity to type strains of species of the genus Mesonia, with highest sequence similarity to the type strain of Mesonia aquimarina. Cellular fatty acid analysis showed a Mesonia-typical fatty acid profile including several branched and hydroxyl fatty acids with highest amounts of iso-C15 : 0 (40.9%) followed by iso-C17 : 0 3-OH (14.8%). In the polyamine pattern, sym-homospermidine was predominant. The diagnostic diamino acid of the peptidoglycan was meso-diaminopimelic acid. The quinone system contained exclusively menaquinone MK-6. The only identified compound in the polar lipid profile was phosphatidylethanolamine present in major amounts. Additionally, major amounts of an unidentified aminolipid and two unidentified lipids not containing a phosphate group, an amino group or a sugar residue were detected. The genomic G+C content of strain 96_Hippo_TS_3/13(T) was 30 mol%. Based on genotypic, chemotaxonomic and physiological characterizations we propose a novel species of the genus Mesonia, Mesonia hippocampi sp. nov., with strain 96_Hippo_TS_3/13(T) ( = CIP 110839T = LMG 28572(T) = CCM 8557(T)) as the type strain. An emended description of the genus Mesonia is also provided.

Diseases of captive yellow seahorse Hippocampus kuda Bleeker, pot-bellied seahorse Hippocampus abdominalis Lesson and weedy seadragon Phyllopteryx taeniolatus (Lacépède).

Seahorses, pipefish and seadragons are fish of the Family Syngnathidae. From 1998 to 2010, 172 syngnathid cases from the Toronto Zoo were submitted for post-mortem diagnostics and retrospectively examined. Among the submitted species were yellow seahorses Hippocampus kuda Bleeker (n=133), pot-bellied seahorses Hippocampus abdominalis Lesson (n=35) and weedy seadragons Phyllopteryx taeniolatus (Lacépède; n=4). The three most common causes of morbidity and mortality in this population were bacterial dermatitis, bilaterally symmetrical myopathy and mycobacteriosis, accounting for 24%, 17% and 15% of cases, respectively. Inflammatory processes were the most common diagnoses, present in 117 cases. Seven neoplasms were diagnosed, environmental aetiologies were identified in 46 cases, and two congenital defects were identified.

[THE MICROSPORIDIUM GLUGEA GASTEROSTEI VORONIN 1974 (MICROSPORIDIA: MARINOSPORIDIA) FROM THE THREE-SPINED STICKLEBACK GASTEROSTEUS ACULEATUS (ACTINOPTERYGII: GASTEROSTEIFORMES) AS AN INDEPENDENT SPECIES].

The microsporidium Glugea gasterostei from the three-spined stickleback Gasterosteus aculeatus was described as an independent species basing upon morphological and ecological traits of the parasite (Voronin, 1974), further supported by ultrastructural characters of its spores (Voronin, 1983). During the revision of microsporidia of the genus Glugea (Canning, Lom, 1986; Lom, 2002), the validity of this species was doubted and it was synonymized with G. anomala. Nevertheless, the molecular phylogenetic analysis performed in the present study showed the unique molecular haplotype of small subunit rRNA gene of G. gasterostei (Genbank accession number KM977990) and its close relatedness to G. anomala, G. atherinae and G. hertwigi (sequence similarity of 99.7 %). One of typical characters of G. gasterostei, as opposed to G. anomala, is the formation of xenomas on inner tissues and not on the surface of infected fishes. This feature is retained even after the infection of different host species. Taken together, these data confirm the validity of G. gasterostei as a separate species among closely related taxa that had diverged comparatively recently.

Individuals' diet diversity influences gut microbial diversity in two freshwater fish (threespine stickleback and Eurasian perch).

Vertebrates' diets profoundly influence the composition of symbiotic gut microbial communities. Studies documenting diet-microbiota associations typically focus on univariate or categorical diet variables. However, in nature individuals often consume diverse combinations of foods. If diet components act independently, each providing distinct microbial colonists or nutrients, we expect a positive relationship between diet diversity and microbial diversity. We tested this prediction within each of two fish species (stickleback and perch), in which individuals vary in their propensity to eat littoral or pelagic invertebrates or mixtures of both prey. Unexpectedly, in most cases individuals with more generalised diets had less diverse microbiota than dietary specialists, in both natural and laboratory populations. This negative association between diet diversity and microbial diversity was small but significant, and most apparent after accounting for complex interactions between sex, size and diet. Our results suggest that multiple diet components can interact non-additively to influence gut microbial diversity.