The role of the rock cod Notothenia coriiceps Richardson, 1844 in the life-cycle of Antarctic parasites

Fifty specimens of Notothenia coriiceps caught in Potter Cove, King George Island, were examined for ecto- and endoparasites. Of the 22 parasite species found, 18 were helminths, 2 were hirudineans and 2 were crustaceans. The isopod Aega antarctica and an unidentified hirudinean are reported for the first time from this fish host. Dominant parasites were the adults of Aspersentis megarhynchus, the invasive stage of Corynosoma spp. (cystacanth) and the adults of Macvicaria pennelli, with respective prevalences of infestation of 94, 76 and 74%. The preferred sites of infestation were the pylorus and intestine, where five different larval (nematodes and cestodes) and eight adult (digeneans and acanthocephalans) parasite species were found. No adult nematodes and cestodes were found and no parasites could be isolated from the musculature. The results of the present study are related to previous findings on the parasite fauna of N. coriiceps. The comparison implies a high parasite diversity in this benthic Antarctic fish species. Most parasites found appear to have a wide range of distribution within Antarctic waters together with a low host specificity. Besides its role as final host for several species of trematodes and acanthocephalans, N. coriiceps serves as transmitter of parasite larvae to piscivorous birds and seals. It is concluded that the parasite fauna in Antarctic fish species provides important insights into the different habitat use and trophic relationship of their fish hosts. Received: 11 September 1997 / Accepted: 12 January 1998     

Experimental studies on the response of the fish (Notothenia coriiceps Richardson, 1844) to parasite (Pseudoterranova decipiens Krabbe, 1878) and other irritant stimuli at Antarctic temperatures

In order to better understand the immune response of Notothenia coriiceps to Pseudoterranova decipiens larvae and other irritant stimuli, we implanted a catgut suture thread, killed P. decipiens larvae and macerated P. decipiens larvae in the hepatic and muscle tissues of the fish. The response varied according to the tissue concerned and the extent of the lesion. The most noticeable immune response occurred with the implant of parasite larvae macerate in the liver, which indicates immunological memory, since all the captured fish were found infected with P. decipiens. An intense response also occurred after macrophages had infiltrated the cuticle of the implanted dead parasite in the liver, which confirms that the cuticle acts as a physical barrier to the immune system. Nevertheless, the immune response of N. coriiceps does not appear able to eliminate the infection and the fish in nature appear to suffer no adverse clinical effects. Accepted: 19 June 1999     

Metal (Fe, Zn, Mn and Cu) levels in the Antarctic fish Notothenia coriiceps

During the 1994/1995 Antarctic summer 20 Antarctic cod (Notothenia coriiceps) of both sexes were collected at King George Island, South Shetland Islands, Antarctica, to determine the levels of Fe, Zn, Mn and Cu in muscle, liver, gonad and kidney. Metal levels were assessed using the inductively coupled plasma-atomic emission spectrometry (ICP-AES) technique. The levels of Fe, Zn, Mn and Cu observed in both sexes of N. coriiceps were significantly lower in muscle tissue than in liver, kidney and gonad; the livers of males and gonads of females had the highest levels. The differences between the sexes were significant for Zn and Mn in gonads and for Cu in liver. Despite the modest size-range of the specimens, the Cu levels in liver, muscle and kidney were significantly inversely correlated with female mass (P < 0.05) as was gonad Cu level and male body length. Fe mainly presented the highest concentrations and Cu and Mn the lowest ones. Mean muscle metal levels are similar to those of hake, cod, herring and mackerel; however, the level of Fe was slightly higher. Accumulation may occur for Fe, Zn and Mn in liver, kidney and gonad, which have higher levels than those of most prey. Received: 21 October 1997 / Accepted: 1 February 1998     

Solution structure of MT_nc,a novel metallothionein from the Antarctic fish Notothenia coriiceps

The structure of [113Cd(7)]-metallothionein (MT_nc) of the Antarctic fish Notothenia coriiceps, the first three-dimensional structure of a fish metallothionein, was determined by homonuclear 1H NMR experiments and heteronuclear [1H, 113Cd]-correlation spectroscopy. MT_nc is composed of an N-terminal beta domain with 9 cysteines and 3 metal ions and a carboxy-terminal alpha-domain with 11 cysteines and 4 metal ions. The position of the ninth Cys of the alpha domain of MT_nc is different from the corresponding Cys of mammalian MTs. As a result, the last CXCC motif in the mammalian MT sequence becomes CXXXCC in the fish MT. This difference leads to a structural change of the alpha domain and, in turn, to a different charge distribution with respect to that observed in mammalian metallothioneins.     

Characterization of the cytoplasmic chaperonin containing TCP-1 from the Antarctic fish Notothenia coriiceps

The cytoplasmic chaperonin containing TCP-1 (CCT) plays a critically important role in the folding and biogenesis of many cytoskeletal proteins, including tubulin and actin. For marine ectotherms, the chronically cold Southern Ocean (−2 to +2°C) poses energetic challenges to protein folding, both at the level of substrate proteins and with respect to the chaperonin/chaperone folding system. Here we report the partial functional and structural characterization of CCT from an Antarctic notothenioid fish, Notothenia coriiceps. We find that the mechanism of folding by the Antarctic fish CCT differed from that of mammalian CCT: (1) the former complex was able to bind denatured β-tubulin but (2) when reconstituted with rabbit Cofactor A, failed to release the protein to yield the tubulin/cofactor intermediate. Moreover, the amino acid sequences of the N. coriiceps CCT β and θ chains contained residue substitutions in the equatorial, apical, and intermediate domains that would be expected to increase the flexibility of the subunits, thus facilitating function of the chaperonin in an energy poor environment. Our work contributes to the growing realization that protein function in cold-adapted organisms reflects a delicate balance between the necessity of structural flexibility for catalytic activity and the concomitant hazard of cold-induced denaturation.     

Hemoglobin from the Antarctic fish Notothenia coriiceps neglecta. 1. Purification and characterisation

Antarctic fishes live at a constant temperature of -1.8 degrees C, in an oxygen-rich environment. In comparison with fishes that live in temperate or tropical waters, their blood contains less erythrocytes and hemoglobin. A study was initiated on the structure and function of Antarctic fish hemoglobin. The erythrocytes of the Antarctic benthic teleost Notothenia coriiceps neglecta, of the family Nototheniidae, have been shown to contain two hemoglobins, accounting for about 90% and 5% of the total content. These hemoglobins have been isolated, and obtained in crystalline form. They are tetramers and contain two pairs of globin chains. The globin chains of each hemoglobin have been purified and characterised. The two hemoglobins appear to have one of the two globin chains in common. The Root and Bohr effects have been investigated in erythrocytes, 'stripped' hemolysates and pure hemoglobins, indicating that the functional properties are finely regulated by pH and allosteric effectors.     

Comparison of fatty acid composition in nine organs of the sympatric Antarctic teleost fish species Notothenia coriiceps and Notothenia rossii (Perciformes: Nototheniidae)

Fatty acid (FA) composition of nine organs from two closely related Antarctic fish species, Notothenia coriiceps and Notothenia rossii, was determined through gas chromatography with flame ionization detection. A data set for each species was obtained using major FA profiles from specimens caught in the sea waters of Admiralty Bay during the summer season. The FA profiles for both species are overall similar, but organ peculiarities have been found, which could reflect metabolic specificities and feeding habits between species. With the exception of liver, the most abundant FA in organs was the n?3 polyunsaturated FA. The total n?6 polyunsaturated FAs were minor components in all evaluated organs. Palmitic acid was identified as the major saturated FA, whereas oleic acid was the most represented of the monounsaturated FA in almost all assessed organs of both species. The n? 3/n? 6 ratios of all organs were higher than 3.5. Differences in individual FA and FA metabolic profiles of some organs observed between N. coriiceps and N. rossii suggest specific requirements in the mobilization, transport, incorporation, and/or catabolism of lipids that were reinforced by differences on some FA ratios expressing the activity coefficient of enzymes implicated on the FA pathway flux.     

Karyotypes of two Antarctic fishes,Notothenia gibberifrons andNotothenia coriiceps neglecta

The chromosomes of two species of Antarctic fishes,Notothenia (Gobionotothen) gibberifrons andNotothenia (Notothenia) coriiceps neglecta, were prepared by the air-drying method at the Polish Antarctic Station “Henryk Arctowski” during the austral summer 1984–1985. ForN. (G.) gibberifrons the diploid number is2n = 46 consisting of 2 metacentric (m) pairs, 1 submetacentric (sm) pair and 20 telocentric (t) or subtelocentric (st) pairs. ForN. (N.) coriiceps neglecta the diploid number is 2n = 22 consisting of 9 m pairs, 1 sm pair and 1st pair. Some aspects of karyological evolution of these fishes are discussed.     

Liver response of the Antarctic fish (<Emphasis Type="Italic">Notothenia coriiceps</Emphasis> Richardson, 1844) to hepatotrophic factors

The Notothenia coriiceps liver is commonly infected with parasites, reducing the hepatic mass and inducing the regeneration. In order to better understand the effect of nutrient influx on hepatic regeneration at 0°C, a usual mammal hepatotrophic factor (HF) solution was injected into ten fish (HF group), while ten fish were injected with saline solution (control), twice a day, for 15 days. The liver and carcass weight were measured, and samples were obtained for histological studies. The HF group presented a higher liver/carcass weight (62.5%) than control group. This increase in liver mass was due mainly to hepatocytes hypertrophy, including nuclear size increase and cytoplasmic inclusions of glycogen. Hyperplasia is also observed, although to a lesser extent. The hepatic reaction to HF in Antarctic fish was here demonstrated for the first time, helping to understand the liver response to seasonal nutrient.     

Specific immunity proteomic profile of the skin mucus of Antarctic fish Chionodraco hamatus and Notothenia coriiceps

The white-blooded Antarctic icefish is the only known vertebrate lacking oxygen-transporting haemoglobins. Fish skin mucus, as the first line of defence against pathogens, can reflect fish welfare. In this study, we analysed the skin mucus proteome profiles of the two Antarctic fish species, the white-blooded Antarctic icefish, Chionodraco hamatus, and the red-blooded Antarctic fish, Notothenia coriiceps, unfolding the different proteins by liquid chromatography coupled with tandem mass spectrometry isobaric tags for relative and absolute quantitation (iTRAQ) technology. Of the 4444 totally identified proteins, 227 differentially expressed proteins (DEPs) were found in the comparison between C. hamatus and N. coriiceps, of which 121 were upregulated and 106 were downregulated in the icefish. In the Kyoto Encyclopedia of Genes and Genomes pathway annotation, we found two pathways “Legionellosis” and “Complement and coagulation cascades” were significantly enriched, among of which innate immune candidate proteins such as C3, CASP1, ASC, F3 and C9 were significantly upregulated, suggesting their important roles in C. hamatus immune system. Additionally, the DEP protein–protein interaction network analysis and “Response to stress” GO category provided candidate biomarkers for deep understanding of the distinct immune response of the two Antarctic fish underlying the cold adaptation.     

Stress response in the Antarctic teleosts (Notothenia neglecta Nybelin and N. rossii Richardson)

Blood chemistry and haematological parameters have been determined in the Antarctic teleosts, Notothenia neglecta Nybelin and Notothenia rossii Richardson at 2° C. Samples were taken using chronically implanted dorsal aortic cannulae following a minimum of 24–36 h recovery. Broadly similar results were obtained for the two species. In N. neglecta , routinely active specimens had high values of arterial pH (7.81) and PO ₂ (9.26 kPa), and modest haemoglobin levels (5.6 g dl⁻¹) relative to temperate species. Following 3 min strenuous activity there was a decrease in arterial pH (7.63) and a small rise in lactate from 0.41 to 0.68 mm, but no significant change in the calculated net metabolic acid load (δH_m+). PaO₂ and PaCO₂ varied inversely during exercise, and oxygen content declined by 22%. pHa and most other haematological parameters returned to routine values between 1–3 h post-exercise. The results suggest that the major effect of strenuous activity in Notothenia spp. is a respiratory, rather than a metabolic acidosis.     

Hemoglobin from the Antarctic fish Notothenia coriiceps neglecta. 2. Amino acid sequence of the alpha chain of Hb1

The complete amino acid sequence of the alpha chain of the main hemoglobin of the Antarctic fish Notothenia coriiceps neglecta (family Nototheniidae) has been determined. It consists of 142 residues; an acetylated seryl residue is at the amino terminal. The molecular mass is 15,519 Da. In comparison with alpha-chain sequences of non-Antarctic poikilothermic fish hemoglobins, the homology appears to be significantly lower than that existing among the latter species. A higher homology has been found with the alpha-chain sequence of the non-poikilothermic bluefin tuna.     

Induced inflammatory process in the Antarctic fish Notothenia neglecta

We studied the ability of the Antarctic fish Notothenia neglecta to conduct an induced inflammatory process at 0°C. Indian ink was injected and a cotton suture thread was implanted into muscle of different groups of fish. After 1–2 days of Indian ink injection, the ink was diffused in the perimysium and there was hemorrhage and cellular infiltrate composed mainly of macrophages A (with few and small lysosomes) and neutrophils; after 7–15 days, there were macrophages A and some macrophages B (cytoplasm clear, lamellar cytoplasmic system forming interdigitations); after 30 days, there was Indian ink in the interior of macrophages A. The suture thread process takes place in two phases: the first (up to 7 days) with predominance of macrophages A and few neutrophils, and the second (15–30 days) with predominance of macrophages B. It can be concluded that N. neglecta is responsive to irritant stimulus with inflammatory process indicating adaptation to the antarctic environment. Received: 22 July 1997 / Accepted: 27 April 1998     

Molecular and comparative analyses of type IV antifreeze proteins (AFPIVs) from two Antarctic fishes, Pleuragramma antarcticum and Notothenia coriiceps

Antifreeze protein type IV (AFPIV) cDNAs and genomic DNAs from the Antarctic fishes Pleuragramma antarcticum (Pa) and Notothenia coriiceps (Nc) were cloned and sequenced, respectively. Each cDNA encoded 128 amino acids, with 94% similarity between the two and 83% similarity with AFPIV of the longhorn sculpin, Myoxocephalus octodecemspinosus. The genome structures of both genes consisted of four exons and three introns, and were highly conserved in terms of sequences and positions. In contrast, the third intron of PaAFPIV had additional nucleotides with inverted repeats at each end, which appeared to be a MITE-like transposable element. Comparative analysis revealed that fish AFPIVs were widely distributed across teleost fishes, well conserved in their intron positions, but more variable in intron sequences and sizes. However, the intron sequences of two Antarctic fishes were highly conserved, indicating recent radiation of notothenioids in the evolutionary lineage. The recombinant PaAFPIV and NcAFPIV were expressed in E. coli, and examined antifreeze activity. PaAFPIV and NcAFPIV gave ice crystals with star-shaped morphology, and thermal hysteresis (TH) values were 0.08°C at the concentration of 0.5mg/ml.     

Stability and conformational dynamics of metallothioneins from the antarctic fish Notothenia coriiceps and mouse

The structural properties and the conformational dynamics of antarctic fish Notothenia coriiceps and mouse metallothioneins were studied by Fourier-transform infrared and fluorescence spectroscopy. Infrared data revealed that the secondary structure of the two metallothioneins is similar to that of other metallothioneins, most of which lack periodical secondary structure elements such as alpha-helices and beta-sheets. However, the infrared spectra of the N. coriiceps metallothionein indicated the presence of a band, which for its typical position in the spectrum and for its sensitivity to temperature was assigned to alpha-helices whose content resulted in 5% of the total secondary structure of the protein. The short alpha-helix found in N. coriiceps metallothionein showed an onset of denaturation at 30 degrees C and a T(m) at 48 degrees C. The data suggest that in N. coriiceps metallothionein a particular cysteine is involved in the alpha-helix and in the metal-thiolate complex. Moreover, infrared spectra revealed that both proteins investigated possess a structure largely accessible to the solvent. The time-resolved fluorescence data show that N. coriiceps metallothionein possesses a more flexible structure than mouse metallothionein. The spectroscopic data are discussed in terms of the biological function of the metallothioneins.     

Distribution of immunoreactive multiple forms of gonadotropin-releasing hormone in the brain of the antarctic fish, Notothenia coriiceps

Previous studies have shown that different gonadotropin-releasing hormone (GnRH) molecular forms are present in different groups of bony fish. In the present study, we have investigated the possible influence of the antarctic environmental contributions upon the distribution and biochemical patterns of GnRH- related molecules. The immunocytochemical distribution of GnRH-like peptides has been studied in the brain of the antarctic fish, Notothenia coriiceps, using antisera raised against three variants of GnRH: mammalian (m-GnRH), chicken (cII-GnRH) and salmon (s-GnRH). cII-GnRH immunoreactivity appears confined to cell bodies located in the lateral hypothalamus, the ventral thalamus and the midbrain rostral tegmentum; immunoreactive nerve fibers densely innervated the hypothalamic periventricular region. By contrast, m-GnRH-like immunoreactive neurons are present exclusively in the torus semicircularis of the mesencephalon and in the outer plexiphorm layers of the optic tectum. These findings suggest that cII-GnRH-like peptides appear to function as hypophysiotropic factors, as demonstrated in other species of bony fish, whereas m-GnRH-like peptides could be involved in modulatory pathways of vestibular and visual functions of  N. coriiceps. Incubation with s-GnRH antiserum failed to prove the occurrence of immunoreactive elements; consequently, at least two molecular forms related to cII-GnRH and m-GnRH seem to act as hypophysiotropic and neuromodulatory factors in the brain of Notothenia coriiceps. Moreover, m-GnRH immunoreactivity in ependymal tanycytes suggests the involvement of such specialized glial cells in neuroendocrine function by linking the cerebrospinal fluid and the median eminence, as demonstrated in mammals. Received: 17 December 1997 / Accepted: 15 May 1998