Wild Cormorants Research Articles

Great cormorants (Phalacrocorax carbo) as potential vectors for the dispersal of Vibrio cholerae

Vibrio cholerae is the cause of cholera, a devastating epidemic and pandemic disease. Despite its importance, the way of its global dissemination is unknown. V. cholerae is abundant in aquatic habitats and is known to be borne by copepods, chironomids and fishes. Our aim was to determine if fish-eating birds act as vectors in the spread of V. cholerae by consuming infected fish. We determined the existence of V. cholerae in the microbiome of 5/7 wild cormorants’ intestine. In three of these V. cholerae-positive wild cormorants, the presence of a gene for cholera toxin (ctxA) was detected. We subsequently tested eight captive, hand-reared cormorants, divided into two equal groups. Prior to the experiment, the feces of the cormorants were V. cholerae-negative. One group was fed exclusively on tilapias, which are naturally infected with V. cholerae, and the other was fed exclusively on goldfish or on koi that were V. cholerae-negative. We detected V. cholerae in the feces of the tilapia-fed, but not in the goldfish/koi-fed, cormorants. Hence, we demonstrate that fish-eating birds can be infected with V. cholerae from their fish prey. The large-scale movements of many fish-eating birds provide a potential mechanism for the global distribution of V. cholerae.

A microarray data analysis method to evaluate the impact of contaminants on wild animals

Here we propose a novel microarray data analysis method applicable to evaluation of the chemical effects on wild animals. First, we analyzed correlations between log-transformed hepatic 2,3,7,8-tetrachlorodibenzo- p-dioxin toxic equivalent (TEQ) levels and probe signals detected in wild cormorant liver to screen contaminant-responsive genes. Second, principal component analysis (PCA) was conducted using the screened probes. Third, these probes were divided into two groups based on our PCA result. Finally, we calculated Euclidian distance of signals, which is equivalent to variance of gene expressions, in each probe set, and analyzed the relationship between log-transformed hepatic TEQ levels and Euclidian distances. A probe set whereby the calculated Euclidian distance was positively correlated with TEQ levels, could indicate genes that were directly affected by dioxins or other persistent organic pollutants (POPs), hence they can be used as biomarkers. By contrast, there were a number of probes whereby the Euclidian distance was negatively correlated with TEQ levels. In the latter probe group, the smaller Euclidian distances in highly contaminated individuals could point to changes in physiological activities of wild cormorants. Therefore, our microarray data analysis method will provide new insights into POPs-responsive genes in field-collected samples for toxicogenomics studies.

Functional Analysis of Avian Metallothionein Isoforms: An Ecotoxicological Approach for Assessing Potential Tolerability to Element Exposure

To assess the inducibility of avian metallothionein (MT) genes and potential tolerability of their protiens to element exposure, we investigated the transcriptional inducibilities of cormorant (Phalacrocorax carbo) and mallard (Anas platyrhynchos) MT genes in CV-1 cells by elements and detoxification potencies of their in vitro synthesized MT proteins. About 1.3 kb of 5'-upstream regions were sequenced for cormorant MT1 and 2 genes, where two metal-responsive elements were identified. Both cormorant MT promoters were dose dependently activated by Cd, Zn, Cu, and CH3Hg, whereas no transactivation was detected by Pb, TI, Ag, inorganic Hg, Cr(VI), Cr(III), As(V), As(III), Ni, Co, Rb, and Bi, suggesting a shared transactivational mechanism of both MTs for specific elements. These findings support our previous results, where Cu and Zn concentrations were shown to be positively correlated with hepatic MT1/2 mRNA levels in wild cormorants. Comparison of EC50 and LOEL (lowest observed effect level) for each element revealed that Cd was the most potent inducer of MT1/2 promoters, followed by CH3Hg, Zn, and Cu. Since LOELs of CH3Hg for both MT promoters were higher than the hepatic levels in wild cormorants, hepatic CH3Hg concentration may not be high enough to induce MT mRNA in the wild population. Although LOELs of Cd were much lower than the hepatic concentrations detected in wild cormorants, no significant correlation was observed between hepatic Cd levels and MT mRNAs. This may be due to the masking effect of multiple elements, probably by Zn and/or Cu that were highly accumulated in wild cormorants. Cotreatment of Cd with Zn supported a possible suppression of Cd-induced MT expression by Zn in wild cormorants. MT1 and 2 proteins of cormorant and mallard endowed Escherichia coli with significantly higher growth rate than control to Cd exposure (500-1000 microM), implying that avian MTs could be involved in the detoxification of intracellular Cd. This study provides the first evidence on the inducibility of avian MT isoforms by specific elements and functional significance of each avian MT isoform in detoxifying intracellular heavy metals. Our in vitro approaches demonstrate their validity in predicting the response of MTs to element exposure in a wild avian population.

Potential effects of perfluorinated compounds in common cormorants from Lake Biwa, Japan: An implication from the hepatic gene expression profiles by microarray

Contamination levels of perfluorinated compounds (PFCs), including perfluorooctanesulfonate (PFOS), perfluorononanoic acid (PFNA), perfluorooctane sulfonamide (PFOSA), perfluorohexanesulfonate (PFHS), and perfluorooctanoic acid (PFOA), were determined in the livers of wild common cormorants (Phalacrocorax carbo) from Lake Biwa, Japan. Potential effects of PFCs alone and combined effects by complex mixture of PFCs and dioxins and related compounds (DRCs) were also assessed by gene expression profiling using a cormorant oligo array. Perfluorooctanesulfonate, PFNA, and PFOSA were detected in almost all liver samples analyzed, while concentrations of PFHS and PFOA were below the limit of quantification. The microarray data analyses revealed that hepatic PFC levels were correlated with the expression of 74 genes. Real-time reverse-transcript polymerase chain reaction data demonstrated that PFOS concentration was positively correlated with mRNA levels of glutathione peroxidase 1 and glutathione S-transferase alpha 3 and negatively correlated with levels of heat shock 70-kDa protein 8 and tumor rejection antigen 1 mRNAs. These results suggest the induction of antioxidant enzymes in response to oxidative stress caused by PFCs and the suppression of molecular chaperones, leading to reduction in protein stability. Moreover, multiple regression analyses identified seven significant models in which certain genes showed expression levels altered by accumulation of PFCs and DRCs. The regression models explained associations with cytochrome P450 1A mRNA and protein expression levels, and its catalytic activity, ethoxyresorufin-O-deethylase of both PFNA and the 2,3,7,8-tetrachlorodibenzo-p-dioxin toxic equivalent levels. Thus, the regression models suggested the potential of PFCs to enhance toxicities of DRCs. Since mixture toxicity is an urgent issue, further study is required to understand the effects of mixtures of PFCs and DRCs in wild cormorants.

Cytochrome P450 1A4 and 1A5 in Common Cormorant (Phalacrocorax carbo): Evolutionary Relationships and Functional Implications Associated with Dioxin and Related Compounds

The present study characterized cytochrome P4501A (CYP1A) isoforms from common cormorant (Phalacrocorax carbo) with regard to their evolutionary relationships and their roles in disposition of dioxin and related compounds (DRCs). Two clones isolated from a cormorant liver cDNA library were named CYP1A4 and CYP1A5 on the basis of greatest overall amino acid identity shared with chicken (Gallus gallus) CYP1A4 (78%) and CYP1A5 (78%), respectively. Spatial heterogeneity in phylogenetic signal along the sequences strongly indicated that cormorant CYP1A4 and CYP1A5 have undergone partial interparalog gene conversion, similar to chicken and mammalian CYP1As. Phylogenetic analysis of a putatively unconverted region produced a tree topology consistent with the orthology of avian CYP1A5s with mammalian CYP1A2s and avian CYP1A4s with mammalian CYP1A1s. Hepatic CYP1A4 and CYP1A5 mRNA levels in wild cormorants from Lake Biwa, Japan, were quantified to examine the effects of DRCs on isoform-specific expression and to evaluate the toxicokinetics of DRCs in which CYP1A expression is involved. Both CYP1A4 and CYP1A5 mRNA levels were positively correlated with total tetrachlorodibenzo-p-dioxin toxic equivalents and concentrations of each congener in most cases in the liver, suggesting the induction of both enzymes through a shared transcriptional mechanism. The lack of correlation of 2,3,7,8-tetrachlorodibenzofuran and 3,3',4,4'-tetrachlorobiphenyl (PCB77) to CYP1A gene expression is likely due to the rapid metabolism of these two congeners. Liver-to-muscle concentration ratios for most DRC congeners except PCB77 and mono-ortho coplanar polychlorinated biphenyls significantly increased with an elevation of CYP1A4 and CYP1A5 mRNA levels. The present data suggest that hepatic sequestration of some DRCs occurs in cormorant via binding to either CYP1A5 or both CYP1A4 and CYP1A5.

Stable isotopes indicate the extent of freshwater feeding by cormorants Phalacrocorax carbo shot at inland fisheries in England

1. The numbers of cormorants Phalacrocorax carbo feeding at English freshwater fisheries during winter have increased rapidly over the last 20 years, causing concern among fishery managers and anglers. 2. In order to assess the extent of freshwater feeding, stable isotope ratios of carbon and nitrogen (δ13C and δ15N) in feathers of wild cormorants from inland freshwater fisheries were compared with those in the feathers of piscivorous birds with marine diets (captive ‘marine‐fed’ cormorants, free‐ranging shags Phalacrocorax aristotelis) and freshwater diets (juvenile goosanders Mergus merganser). 3. Isotope signatures of feathers represent the diet at the time of growth. Feathers grown at different times of the year were taken from wild cormorants; each feather type therefore represented the diet over a different temporal scale. 4. Isotopic analyses of feathers indicated that, when shot, nearly all of the cormorants had been feeding entirely on freshwater prey. The mean δ13C value of primary feathers growing when birds were shot was –22·2‰, indicative of an entirely freshwater diet. 5. The move to freshwater habitats from coastal breeding grounds occurred over several months, but once established cormorants appear to have fed at freshwater sites throughout the autumn and winter. 6. The suitability of using a two‐source isotopic mixing model in order to quantify the extent of freshwater feeding in piscivorous birds is discussed. 7. Although the results indicate long‐term residency and feeding in freshwater systems, they do not indicate whether birds were feeding regularly at the sites at which they were shot, or the composition of the diet. It is recommended that further studies using telemetry and multiple isotope analyses be carried out in order to address these issues.

Distribution and biochemical effects of DDT, DDD and DDE in penned double-crested cormorants

Concentrations, distribution and chronic effects of DDT, DDD and DDE were determined in penned cormorants ( Phalacrocorax a. auritus) treated with 2, 5 and 10 mg of a combination of these compounds daily in their diet. Birds stressed by a one-half decrease in food after the cessation of 9 weeks of treatment and birds that died of DDT toxicity showed a marked increase in brain and liver residues and a decrease in carcass residues. Higher brain residue levels were significantly correlated with decreased body weight ( p < 0.01) and carcass lipid content ( p < 0.05). DDD concentrations in the brain were found to be the best indicator of DDT toxicity. Brain concentrations ranged from 24 to 85 ppm in birds that died of toxic effects and from 0.4 to 29 ppm in survivors, indicating that 30 ppm was diagnostic of toxicity. Brain concentrations of DDT and metabolites in wild cormorants indicated no immediate danger of toxicity. Average residue levels in the carcass of wild adult cormorants was 1.00 ppm for DDD and 10.6 ppm for the total of DDT, DDD and DDE. This represents a total body burden of 2.2 mg of DDD and 23.3 mg of the DDT complex as adult cormorants averaged 2200 g in body weight. Analysis of total liver vitamin A indicated a significant decrease of vitamin A due to treatment. An analysis of variance showed a significant decrease in liver ( p < 0.05) and heart weights ( p < 0.05) due to treatment but not brain or spleen weights when analyzed as percentage of body weight. A significant negative correlation was found between liver weight and brain concentrations of DDE + DDD + DDT ( p < 0.05). No significant effects due to treatment were found on blood chemistry values.

Insecticides, polychlorinated biphenyls and mercury in wild cormorants, pelicans, their eggs, food and environment.

Insecticides, polychlorinated biphenyls and mercury in wild cormorants, pelicans, their eggs, food and environment.

Diagnosis and treatment of aspergillosis in captive cormorants.

Aspergillosis was diagnosed in 8 of 50 wild nestling double-crested cormorants (Phalacrocorax auritus). Typical granulomatous nodules were observed in the lungs and on the air sacs. Aspergillus fumigatus was isolated from the infected tissues of the birds and their nesting material. Amphotericin B was administered as inhalant therapy, in addition to the removal of nesting material and disinfection of holding cages.It was concluded that aspergillosis is an endemic disease among wild cormorants in South Dakota and that during the course of this study, stress did not appear to be an important factor in the development of this disease.