RELATIVE ABUNDANCE OF LARGE WHALES AROUND SOUTH GEORGIA (1979–1998)1

To assess large-whale stocks following the cessation of land-based South Georgia whaling in 1965, we report three independent sighting databases: a cruise in 1997, observations from Bird Island (NW of South Georgia) between 1979 and 1998, and mariner sightings between 1992 and 1997. All species were rare, with sightings of southern right whales being the most common event. Two right whales photographed off South Georgia matched animals known from Peninsula Valdés, Argentina, a population known to be growing at 7%per annum. In contrast, blue and fin whales appeared to be less abundant. A single blue whale mother-calf pair was observed off the Shag Rocks in February 1997. Extirpation of animals from this particular feeding ground is the most likely reason for ongoing low numbers of all species. Other factors may include competition for krill by traditional predators such as penguins and seals and more recently by humans, an unusually high rate of natural mortality, habitat change such as alteration in sea ice coverage, and/or the impact of ongoing whaling. The history of this critical area of large-whale habitat and this report demonstrate the need for improved, consistent longterm monitoring of population trends for these depleted stocks.     

cDNA microarray analysis reveals the capacity of the cold-adapted Antarctic fish <Emphasis Type="Italic">Trematomus bernacchii</Emphasis> to alter gene expression in response to heat stress

During their many millions of years of evolution in the extreme and stable cold, Antarctic notothenioid fishes have acquired profoundly cold-adapted physiologies. Gene expression profiling via cDNA microarray was used to determine the extent to which one species of notothenioid, Trematomus bernacchii, has retained the ability to alter gene expression in response to heat stress. While an inability to up-regulate the expression of any size class of heat shock proteins (except for a 1.1-fold induction of the co-chaperone Hsp40) was observed, hundreds of additional genes, associated with a broad range of cellular processes, were responsive to heat. Many of these genes are associated with central aspects of the evolutionarily conserved cellular stress response (CSR), which plays a pivotal role in responding to physical and chemical stresses. The inability of T. bernacchii to mount a heat shock response underscores the potential susceptibility of this species to the effects of global warming.     

Constancy and control of heart rate during an increase in temperature in the Antarctic fish Pagothenia borchgrevinki

The effect of an acute temperature increase on the control of the heart of the Antarctic teleost Pagothenia borchgrevinki was examined. Heart rate was thermally independent over the range −1.2°C to 3°C, although increasing the temperature from −1.2°C to 3°C elicited a decrease in ventral aortic pressure. Administration of the muscarinic receptor antagonist atropine and the β-adrenoreceptor antagonist sotalol abolished the thermal independence of heart rate, with heart rate increasing at Q₁₀=2. As temperature was increased from −1.2°C to 3°C, cholinergic tone on the heart also increased, from 44.6±4.2% to 70.0±8.4%. At the same time the adrenergic tone increased from 35.5±3.3% to 43.0±3.1%, but the effect on the heart was masked by the increase of cholinergic tone, leading to the thermal independence of heart rate.     

Absence of Transitory [Ca2+]I Flux During Early In Vitro Metacyclogenesis of Trypanosoma cruzi1

ABSTRACT. The phorbol ester TPA (phorbol 12-myristate 13-acetate) substitutes for CO₂ as an agonist for transforming Trypanosoma cruzi epimastigotes to the metacyclic trypomastigote stage in a starvation medium consisting of phosphate buffered saline + 10 mM proline, 10 mM sodium acetate and 0.035% NaHCO₃. Since TPA is thought to stimulate protein kinase C by mimicking the activity of the secondary messenger diacylglycerol, the above result suggested that T. cruzi metacyclogenesis could be activated by a Ca^2+-dependent protein kinase C signal induction pathway. Accordingly, cytosolic calcium flux ([Ca²⁺]_i) in epimastigotes, activated with 5% CO₂ or TPA (10^-7 M), was measured with the Ca²⁺ molecular probe, fluo-3AM. In addition, [Ca²⁺]_i was measured in cells incubated with putative metacyclogenic agonists (e.g. proline, glutamate, bioamines, ionophores and catecholamines). None of the compounds studied, except for EGTA, affected cytosolic Ca²⁺ levels. Control assays with 11 μM thapsigargin, which mobilizes noncytoplasmic Ca²⁺ stores by inhibiting endoplasmic reticulum Ca²⁺-ATPase. validated our fluorometric assay procedure. Although thapsigargin significantly increases cytoplasmic Ca²⁺ fluorescence, it has no effect on transformation. The protein kinase C inhibitors staurosporine, H-7 and HA 1004 were tested for their effect on T. cruzi metacyclogenesis. Low concentrations of staurosporine and HA 1004 significantly elevated Pent strain transformation while H-7 had no effect on Peru strain metacyclogenesis. Inhibitor H-7 did significantly depress CL transformation. the results indicate that induction of T. cruzi metacyclic trypomastigote formation by CO₂ and TPA is not accompanied by changes in cytosolic Ca²⁺ and do not provide supporting evidence for participation of a protein kinase C-mediated phosphoinositide cascade in metacyclogenesis.     

Functionally distinct haemoglobins of the cryopelagic Antarctic teleost Pagothenia borchgrevinki

Pagothenia borchgrevinki , has a higher haemoglobin concentration than other Antarctic notothenioids and the high oxygen capacity may correlate with the relatively active mode of life of this fish. The fish has five haemoglobins (Hb C, Hb 0, Hb 1, Hb 2 and Hb 3) with Hb 1 accounting for 70–80% of the total, and Hb C being present in trace amounts. Hb 1 and Hb 2 are functionally similar in terms of Bohr and Root effects. Hb 3 has a weaker Bohr effect than Hb 1 and Hb 2, and the Root effect is similar to that of Hb 1. Hb 0 has a strong Bohr effect and the Root effect is enhanced to a larger extent by the physiological effectors chlorides and phosphates than that of the other components with the exception of Hb C. The heats of oxygenation are lower than those of temperate fish haemoglobins. Temperature variations may have a different effect on the functional properties of each haemoglobin, and chloride and phosphates may play an important role in the conformational change between the oxy and deoxy structures. The complete amino acid sequences of Hb 1 and Hb 0, as well as partial N-terminal or internal sequences of the other haemoglobins, have been established. The high multiplicity of functionally distinct haemoglobins indicates that P. borchgrevinki , has a specialized haemoglobin system.     

Establishment and characterization of Pinus pinaster suspension cell cultures

We report the establishment of a Pinus pinaster (Ait.) cell suspension culture in a modified MS medium supplemented with 2 mg ml⁻¹ 2,4-D and 1 mg ml⁻¹ BA. Calli were obtained from seedling root segments and established a friable isodiametric cell suspension, suitable for in vitro studies of maritime pine at the cellular level. Growth (dry weight), cell viability, pH, and nutrient consumption: carbon source (sucrose, fructose and glucose), nitrogen source (ammonia and nitrate) and phosphate were monitored over 24 h. Suspension cells exhibited a 15-day exponential growth stage, during which a biphasic consumption profile was observed for all nutrients. Phosphate was the first limiting nutrient and preferable consumption was observed for glucose over fructose and nitrate over ammonium.     

Predicting the impact of climatic warming on the carbon balance of the moss <Emphasis Type="Italic">Sanionia uncinata</Emphasis> on a maritime Antarctic island

The effects of climatic factors, especially those of temperature, on the carbon balance of the moss Sanionia uncinata were examined on King George Island in the maritime Antarctic. Net photosynthesis (P _n ) and dark respiration rates of two colonies (A and B) were measured with a portable infrared gas analyzer. Colony A showed small P _n compared with its dark respiration rates throughout the growing season. Colony B showed much higher net photosynthetic rates, but the dark respiration rates of the two colonies did not differ significantly. Net photosynthetic rate determined at light saturation was almost constant over a wide temperature range, from 5° to 15°C, while the dark respiration was strongly affected by temperature. To assess the impact of warming on the carbon balance of the moss, cumulative carbon gain of the moss was calculated using a simulation model for the main part of the growing season. The results suggest that climatic warming may cause a reduction of carbon gain in some relatively photosynthetically inactive moss colonies. Received: April 13, 2001 / Accepted: November 5, 2001