Fish of Admiralty Bay (King George Island,South Shetland Islands,Antarctica)

Summary The species composition of the ichthyofauna of Admiralty Bay, King George Island was determined from results of sampling using bottom trawls, gill-nets and long-lines. Thirty-five species from 24 genera and 10 families (Table 1) were found. The number of species increased with depth (e.g. 7 species at 100 m, 14 species at 255 m and 21 species at 540 m), a tendency characteristic of Antarctic waters. In the bay, the catch rate obtained with a bottom trawl (greater than 30 kg/h) was roughly ten times lower than the catch rate using the same gear on the shelf around the Island. Notothenia gibberifrons was the dominant species in all trawls. The majority of these fish (about 95%) were immature juveniles (Table 4). Younger fish were found to inhabit shallower waters (Fig. 1). The majority of the fish of species Notothenia coriiceps neglecta, Notothenia rossii marmorata, Notothenia nudifrons, Trematomus newnesi and Trematomus bernacchii preferred waters about 255 m deep. Fourteen specimens of a previously undescribed species of the genus Psilodraco (currently being described by H. DeWitt) were caught in the bay within the 146 to 540 m depth range. The rare zoarcid, Lycenchelys aratrirostris, was also caught in Admirality Bay; previously this species had only been reported from the Elephant Island region. In the case of Trematomus newnesi, the occurrence of scales in the interorbital space was noted (Fig. 2), an observation which verifies this feature as a distinct taxonomical criterion for this species.     

Induction of mixed function oxidase (MFO) system in two species of antarctic fish from Terra Nova Bay (Ross Sea)

Summary The aim of this study was to investigate the detoxicant Mixed Function Oxidase system in two species of Antarctic fish, C. hamatus and P. bernacchii, collected during the Antarctic summer of 1989–1990 at the Italian Scientific Station at Terra Nova Bay (Ross Sea). Several specimens were induced by injection of phenobarbital (PB), 3-methylcholanthrene (3-MC) and PCBs in the caudal vein. The results show significant differences between the two species. In C. hamatus, basal activity of benzo(a)pyrene monooxygenase (BPMO) was among the lowest measured even in fish of temperate seas, and in P. bernacchii it was 20 times lower. The values of regenerating activities (NADPH-cytochrome c reductase (NADPH-CYTCRED), NADH-cytochrome c reductase (NADH-CYTCRED) and NADH-ferricyanide reductase (NADH-FERRIRED) suggest that the two species use different electron donor molecules. Injection of chemicals in the caudal vein did not provoke induction of MFO activity in P. bernacchii. In C. hamatus, phenobarbital and PB-type inducers did not cause induction but there was a statistically significant response to 3-MC.     

Regulatory peptides in the urinary bladder of two genera of Antarctic teleosts

Somatostatin 14, prolactin, atrial natriuretic peptide, galanin and urotensin II were found using immunohistochemistry in the urinary bladders of the Antarctic fishes Trematomus bernacchii (Nototheniidae) and Chionodraco hamatus (Channichthyidae) caught in the Ross Sea. The urinary bladders of the two species showed a different histology in the epithelial layer. In T. bernacchii the epithelium comprises a single type of columnar cells, while in C. hamatus the columnar cells are restricted to the ventral portion of the bladder, and the dorso-lateral region is lined by cuboidal cells. No difference in the intensity of the immunostaining was observed in the two cell types; the only variation was a different distribution of the immunoreactions, which were present in the whole cytoplasm in the cuboidal cells and restricted to the apical and/or basal portion of the columnar cells. Accepted: 1 November 1998     

Relationship between metallothionein and metal contents in red-blooded and white-blooded Antarctic teleosts

Metal bioaccumulation and metallothionein were investigated in different organs of the red-blooded teleost, Trematomus bernacchii and the haemoglobinless Chionodraco hamatus. Specimens of the two Antarctic fish were sampled from Terra Nova Bay (Ross Sea), and their levels of Cd, Cu and Zn in homogenates and in soluble fractions of liver, muscle, gills, heart and plasma were determined. Dosages of metallothioneins (MTs) or MT-like proteins were assayed by the silver saturation method in soluble fractions of the same organs. In both T. bernacchii and C. hamatus the highest MT contents were found in liver. Hepatic MT and Cd, Cu and Zn concentrations correlated positively in T. bernacchii, whereas in C. hamatus hepatic MT showed a positive correlation only with Cd. Positive correlations were also found between Cd and MT in gills of the two species. A metal-binding protein containing a high percentage of cysteine from C. hamatus was purified and compared with the MT from T. bernacchii and mammals. Accepted: 27 November 1999     

Comparison of angiotensin converting enzyme-like activity in the Antarctic teleosts <Emphasis Type="Italic">Trematomus bernacchii</Emphasis> and <Emphasis Type="Italic">Chionodraco hamatus</Emphasis>

Biochemical parameters of the angiotensin converting enzyme-like activity (ACELA) in the gills of two Antarctic teleosts, Chionodraco hamatus and Trematomus bernacchii were characterized. Enzymatic activity was revealed following hydrolysis of a specific substrate of angiotensin-converting enzyme N-[3-(2-furyl)acryloyl]l-phenylalanyl-glycyl-glycine (FAPGG) and metabolites were separated by reverse phase HPLC analysis. The results showed similar Km values for the substrate FAPGG at 5°C for the two species with an increase of Km value for T. bernacchii at 25°C. The optimum pH value was 8.5 at 25°C and optimum chloride concentrations were about 300 mM. In T. bernacchii the optimum temperature for maximum enzyme activity was 50°C, while maximum activity in C. hamatus occurred at 35°C. Lisinopril was more efficient in inhibiting ACELA in C. hamatus with an I ₅₀ value of 16.83 ± 5.11 nM, compared to an I ₅₀ value of 30.66 ± 5.19 nM in T. bernacchii. In conclusion, it appears that some biochemical parameters of ACELA in C. hamatus differ from those in T. bernacchii, probably due to different ways that the enzyme adapts to the constantly cold temperatures of the animal’s environment.     

Blood Lipids in Antarctic and in Temperate-Water Fish Species

Antarctic fish live in very cold water and have adapted to this exceptional environment. Hemoglobin is absent or very low; yet these fish still have erythrocytes, and from these we prepared ghost-like membranes. We studied for the first time the lipid composition of ghost membranes and of plasma in Antarctic fish (C. hamatus and T. bernacchii) and compared our results with those obtained for temperate-water fish (C. auratus and A. anguilla taken from Lake Trasimeno, Perugia, Italy). The membranes of Antarctic fish were richer in glycerophospholipid (especially phosphatidylethanolamine), whereas the membranes of temperate-water fish were richer in sphingomyelin. Unsaturated fatty acids were particularly abundant in Antarctic fish: C. hamatus had long-chain unsaturated fatty acid (especially C22:6 ω-3), whereas T. bernacchii had shorter unsaturated fatty acyl chains (c16:1, ω-7). On the other hand, C. auratus and A. anguilla were particularly rich in C16:0, which constituted more than one-half of the total fatty acid. Plasma lipids (both phospholipid and cholesterol) were much more abundant in temperate-water fish. The differences in phospholipid content were mainly due to choline glycerolipids. Measures of membrane fluidity inferred from the fluorescence anisotropy of DPH indicated that the membranes from Antarctic fish were more fluid at any measured temperature than those obtained from fish living in temperate waters. The ability to live in a very cold environment has therefore been achieved by the two Antarctic species tested in this paper by different strategies, but with the same results on fluidity.     

Spermatogenesis in some Antarctic teleosts from the Ross Sea: histological organisation of the testis and localisation of bFGF

Testis structure and spermatogenetic activity were studied in two Antarctic teleostean species, Chionodraco hamatus and Trematomus bernacchii, captured during the austral summer in the Ross Sea. The specimens of C. hamatus showed full reproductive activity but, the spermatogenetic cycle being over, only spermatogonia and Sertoli cells were present in the seminiferous tubules whereas the lumina were full of sperm. By contrast, the specimens of T. bernacchii were in the stage of spermatogenetical recrudescence, having not yet entered the reproductive period. In this species, the seminiferous tubules were devoid of lumen and full of spermatogonial cysts, showing some mitoses. Many tubules contained cysts of meiotic spermatocytes I and, in one case only, small cysts of spermatocytes II. The final stages of spermatogenesis were lacking, presumably occurring later, in autumn/winter. The immunocytochemical tests aimed at identifying bFGF and FGFR1 revealed a positive reaction both in Sertoli cells and spermatogonia in the C. hamatus specimens, indicating that this species was ready to start a new spermatogenetic cycle. The weak reaction in the specimens of T. bernacchii suggests that, in this species, the stage of cell division was over and that of meiosis and differentiation was starting. These data indicate that Antarctic fish have an opportunistic spermatogenetic cycle. Accepted: 24 October 1999     

Influence of latitude, water depth, day v. night and wet v. dry periods on the species composition of reef fish communities in tropical Western Australia

Trap sampling over reefs in deep (mean = 20 m) and shallow (mean = 10 m) waters along c. 1500 km of coastline in tropical north‐western Australia during both day and night and in wet and dry periods yielded 23 377 fishes, representing 32 families, 58 genera and 119 species. Individuals of the Serranidae, Lutjanidae, Lethrinidae and Carangidae contributed 88·9% to the total catch. The ichthyofaunal compositions of the Kimberley, Canning and Pilbara bioregions were relatively discrete. Species composition was influenced far more by location (latitude) than by water depth, period and time of day, and underwent a gradational change southwards. The latter change reflected differences in the trends exhibited by the relative abundances of certain species with increasing latitude and the confinement of other species largely to particular regions. The three most abundant species, i.e. Lethrinus sp. 3, Lutjanus carponotatus and Lethrinus laticaudis contributed 34·8, 20·8 and 11·6% to the total catch, respectively. The first species was rarely recorded in the two most northern locations and was abundant in the four most southern locations, whereas the last two species were relatively more abundant in northern than in southern locations. Lutjanus bitaeniatus and Lutjanus johnii were found exclusively at the two locations in the Kimberley region, whereas Abalistes stellatus, Pentapodus emeryii and Lethrinus nebulosus were not caught in this region but were found in both locations of the Canning and Pilbara regions. The species composition in deep and shallow waters at each location almost invariably differed significantly between day and night and between dry and wet periods, with species such as L. bitaeniatus, L. johnii, Lutjanus sebae and A. stellatus being more abundant over deep reefs, whereas L. carponotatus, L. laticaudis, Siganus fuscescens and Lethrinus lentjan were more numerous over shallow reefs. Species such as L. johnii and Lethrinus atkinsoni were relatively more important in night‐time than daytime catches, whereas the reverse applied to Lethrinus lentjan, L. laticaudis and Choerodon cyanodus. Lethrinus sp. 3 and L. laticaudis were relatively more important in catches during the dry than wet period.     

Renin-angiotensin system in antarctic fishes

• 1.1. The presence of a renin-angiotensin-like system has been investigated in the Antarctic fishes Chionodraco hamatus (Fam. Channichthydae) and Pagothenia (Trematomus) bernacchii (Fam. Notothenidae).
• 2.2. A renin-like activity is present in plasma and kidney of both the white blooded (Chionodraco) and the red blooded (Pagothenia) species.
• 3.3. An angiotensin converting enzyme-like activity has been demonstrated in plasma, gills and kidneys of both species. The activity is inhibited by high temperature.
• 4.4. From our data a renin-angiotensin-like system is present in the Antarctic fishes studied but the cascade of enzymes is active only at low temperatures.

     

Mitochondria-rich cells in Antarctic fish gills

We used transmission and scanning electron microscopy and an antibody to the inner mitochondrial membrane to study the presence and localisation of mitochondria-rich cells in the gills of two Antarctic fishes, Chionodraco hamatus (Channichthyidae) and Trematomus bernacchii (Nototheniidae). The general morphology of the gills in the two species was slightly different: in T. bernacchii the filament and secondary lamellae were short and thicker, and mitochondria-rich cells were less numerous than in C. hamatus. In the two species the mitochondria-rich cells, distributed in the secondary and primary epithelium, were of the same morphological type, similar to the α-chloride cells of temperate seawater teleosts. The study was carried out to compare the mitochondria-rich cells of Antarctic fishes to the chloride cells of temperate marine teleosts. Immunolocalisation, using a specific antibody to the α-subunit of Na⁺/K⁺-ATPase, was observed in numerous epithelial cells in the interlamellar epithelium and on the secondary lamellae, suggesting an active sodium chloride secretion. Accepted: 16 October 1999     

Key enzymes of the kallikrein-kinin system in Antarctic teleosts

In this study, some of the mammalian kallikrein-kinin system (KKS)-like components were identified in two species of Antarctic notothenioid [Chionodraco hamatus (Channichthydae) and Trematomus bernacchii (Nothothenidae)]. The kidney and heart were assayed for kallikrein-like activity using the synthetic substrate d-Val-Leu-Arg-paranitroanilide. Values expressed as nmol p-nitroanilide/mg proteins, were in C. hamatus 15.5±1.5 and 15.2±1.4 in kidney and heart, respectively, and 15.8±2.2 and 15.9±1 in kidney and heart of T. bernacchii. Kallikrein-like activity was inhibited bvy aprotinin and phenylmethylsulfonyl fluoride (PMSF). The assay was stable at 20°C. Kininase II-like activity was performed on kidney, gills and heart using the substrate hippuryl-lhistidyl-l-leucine. The activity was inhibited by captopril, and in kidney and gills by high temperatures (20°C and 37°C); in the heart the enzymatic activity was measurable also at 20°C. Bradykinin-like immunoreactive cells were localized by immunohistochemistry in the nephron, in the gills, and in the arterial walls of the heart. These results show that Antarctic teleosts possess elements comparable to those of the KKS, including kallikrein-like, and kininase II-like activities, and the end product of the enzymatic cascade, bradykinin. The enzymatic cascade appears to be fully active only at low temperatures. Received: 19 April 1996/Accepted: 30 June 1996     

Heterotrophic flagellates, centrohelid heliozoa and filose amoebae from marine and freshwater sites in the Antarctic

Heterotrophic flagellates, centrohelid heliozoa and filose amoebae were recorded from cultures derived from water collected at marine and freshwater sites in the Antarctic. Marine samples were collected in the vicinity of Prydz Bay, southeast Antarctica and freshwater samples from Sombre Lake on Signy Island and Crooked and Druzhby Lakes in the Vestfold Hills. Thirty-five species were identified. One new species, Kiitoksia kaloista (Protista incertae sedis), is described. The other species have been previously reported from other geographic locations, providing no evidence for endemism in protozoan species found in Antarctica. Received: 23 September 1996 / Accepted: 28 December 1996     

Qualitative and quantitative analysis of serum immunoglobulins of four Antarctic fish species

Immunoglobulins from the Antarctic fish species Trematomus bernacchii, Trematomus hansoni, Trematomus newnesi, and Chionodraco hamatus were analysed in whole serum and after purification by affinity chromatography on protein A-sepharose. Using SDS-PAGE, the apparent masses of the heavy and light chains were, respectively, 83.5 kDa and 27.5 kDa for T. bernacchii, 83.5 kDa and 27 kDa for T. hansoni, 81 kDa and 27.5 kDa for T. newnesi, and 74.5 kDa and 30 kDa for C. hamatus. It was not possible to purify immunoglobulins from T. newnesi due to their low concentration in serum. Heterogeneity in mass of both heavy and light chains was observed in all species. By using a polyclonal antibody raised against sea bass immunoglobulins, cross-reactivity was observed with heavy and light chains of all species. With this antibody, an indirect enzyme-linked immunosorbent assay (ELISA) was developed and results showed the relative immunoglobulin concentration in sera of the Antarctic fish species considered, using as standard sea bass immunoglobulins. Received: 25 November 1996 / Accepted: 3 February 1997     

Antarctic teleost immunoglobulins: more extreme, more interesting

We have investigated the immunoglobulin molecule and the genes encoding it in teleosts living in the Antarctic seas at the constant temperature of −1.86 °C. The majority of Antarctic teleosts belong to the suborder Notothenioidei (Perciformes), which includes only a few non-Antarctic species. Twenty-one Antarctic and two non-Antarctic Notothenioid species were included in our studies. We sequenced immunoglobulin light chains in two species and μ heavy chains, partially or totally, in twenty species. In the case of heavy chain, genomic DNA and the cDNA encoding the secreted and the membrane form were analyzed. From one species, Trematomus bernacchii, a spleen cDNA library was constructed to evaluate the diversity of VH gene segments. T. bernacchii IgM, purified from the serum and bile, was characterized. Homology Modelling and Molecular Dynamics were used to determine the molecular structure of T. bernacchii and Chionodraco hamatus immunoglobulin domains. This paper sums up the previous results and broadens them with the addition of unpublished data.     

Species identification in the trematomid family using nuclear genetic markers

The Trematominae, a subfamily of the Nototheniidae, are typical of the high-Antarctic shelf waters. Within the Trematominae examples of phenotypic plasticity and possible cryptic speciation have been observed. Morphological identification of adult stages can be problematic in cases of high phenotypic plasticity or cryptic speciation. Additionally, postlarval and juvenile stages often have traits still under development and which lack distinction. A microsatellite DNA multiplex of six markers has been developed for Trematomus newnesi (Van Houdt et al. 2006). This multiplex was tested on five additional trematomid taxa: Pagothenia borchgrevinki, Trematomus bernacchii, Trematomus eulepidotus, Trematomus hansoni and Trematomus scotti. We used these six microsatellite loci to assess the genetic differentiation among species and the resolution power of these loci for individual-based assignment methods. The six species could be well discriminated by conventional methods such as principal component analysis and distance-based methods, and individual Bayesian assignment methods. This marker set can be used for a number of purposes, including the identification of eggs and larval and adult stages. It is also useful for the investigation of recent phylogenetic patterns, as well as the detection of cryptic speciation, which has been suggested for T. bernacchii and T. newnesi but never confirmed with high polymorphic genetic markers.     

Response of deep-sea benthic foraminifera to Miocene paleoclimatic events, DSDP Site 289

Changes in the Miocene deep-sea benthic foraminifera at DSDP Site 289 closely correlate to the climatically induced variations in deep and bottom waters in the Pacific Ocean. In early Miocene time, oxygen and carbon isotopes indicate that bottom waters were relatively warm and poorly oxygenated. Benthic foraminiferal assemblages are characterized by various species inherited from the Oligocene. Expansion of the Antarctic icecap in the early middle Miocene, 14–16 m.y. ago, increased oxygen isotope values, produced cold, more oxygenated bottom waters and lead to a turnover in the benthic foraminifera. An Oligocene—early Miocene assemblage was replaced by a cibicidoid-dominated assemblage. Some species became extinct and benthic faunas became more bathymetrically restricted with the increased stratification of deep waters in the ocean. In mid-Miocene time, Epistominella exigua and E. umbonifera, indicative of young, oxygenated bottom waters, are relatively common at DSDP Site 289. Further glacial expansion 5–9 m.y. ago lowered sealevel, increased oceanic upwelling and associated biological productivity and intensified the oxygen minima. Abundant hispid and costate uvigerines become a dominant faunal element at shallow depths above 2500 m as E. umbonifera becomes common to abundant below 2500 m. By late Miocene time, benthic faunas similar in species composition and proportion to modern faunas on the Ontong-Java plateau, had become established.     

Inducible heat tolerance in Antarctic notothenioid fishes

Significant increases in heat tolerance (time of survival at 14°C) were observed for some, but not all, species of notothenioid fishes collected from McMurdo Sound, Antarctica (77°51′S) following acclimation to 4°C. The increase in thermal tolerance was rapid in Trematomus bernacchii, developing within 1–2 days of acclimation to 4°C. Long-term (6–8 weeks) acclimation to 4°C led to greater heat tolerance in Trematomus pennellii than in T. bernacchii. Unlike its demersal congeners, the cryopelagic notothenioid Pagothenia borchgrevinki did not increase heat tolerance during warm acclimation. A deep-living zoarcid fish, Lycodichthys dearborni, also failed to increase heat tolerance, but survived significantly (> threefold) longer at 14°C than the notothenioids.     

Haematological changes in an Antarctic teleost,Trematomus bernacchii,following stress

The effect of an acute increase in temperature, exhaustive exercise and hypoxia on the haematology of the benthic Antarctic teleost, Trematomus bernacchii was investigated. High temperature and hypoxia caused the biggest changes to the blood, with increases in haematocrit, haemoglobin concentrations and plasma chloride levels. The spleen decreased in mass. Exercise produced the smallest changes. Changes were substantially less than reported for the more active cryopelagic species Pagothenia borchgrevinki. The magnitude of the haematocrit increase is discussed in relation to life-style of fish living in the Antarctic.     

Exercise challenge in Antarctic fishes: do haematology and muscle metabolite levels limit swimming performance?

 Burst swimming increased haematocrit (partly from erythrocyte swelling) in the cryopelagic nototheniid Pagothenia borchgrevinki, but not in the benthic species Trematomus bernacchii. Erythrocyte nucleotides, which regulate haemoglobin-oxygen affinity, remained constant. Plasma cortisol was high in all captive fish and raised questions about the effects of chronic stress on metabolic measurements from Antarctic fish held in captivity. Glycogen was reduced in white trunk muscle, but not in the red pectoral muscle of exercised P. borchgrevinki. Red pectoral muscle glycogen was nearly 3 times higher in T. bernacchii than in P. borchgrevinki but post-exercise lactate rises were modest. Lactate values were, however, higher in exercised P. borchgrevinki white muscle than in T. bernacchii, and correlated with muscle-buffering capacity. Resting adenylate energy charge (AEC) was unexpectedly low in both species and reduced with exercise only for white muscle in P. borchgrevinki. While it appears that the capacity for burst swimming is limited by endogenous metabolic fuels, confirmation of low resting values of ATP and AEC in Antarctic fishes requires the development of methods that maintain high phosphocreatine levels in the muscle. Received: 12 February 1996/Accepted:1 May 1996     

Widespread occurrence of populations of the unique autotrophic ciliate Metodinium rubrum (Ciliophora: Haptorida) in brackish and saline lakes of the Vestfold Hills (eastern Antarctica)

The occurrence of the unique autotrophic ciliate Mesodinium rubrum was investigated in a suite of lakes of various salinities situated in the Vestfold Hills oasis, Princess Elizabeth Land (eastern Antarctica). M. rubrum was found to occur in all but the most hypersaline lakes in the survey but was most numerous in the more brackish lakes. Salinity and water column temperature appeared to be the most important factors controlling the occurrence and abundance of this species. Nutrient levels (phosphate and nitrate) did not appear to be important controlling factors, although their influence may have been distorted by the fact that nutrient concentrations were generally higher in the more saline lakes. The widespread occurrence of this species in brackish and saline lakes of the Vestfold Hills provides opportunities to study the ecology and possible physiological and ultrastructural adaptations to living in a high-latitude environment of this ubiquitous and important species in marine microbial food webs.