FISH 133 Spring 2019

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A Living Fossil, the Lungfish When rain comes and the soil becomes soft, the lungfish comes out of its hibernating state and re-emerges. Threats to lungfish Like most species of fish, suitable habitat is key for their survival. In Australia there are concerns that dams have drowned out the shallow slow flowing plant-rich water that they depend on, to spawn and feed in. Non-native species such as tilapia are known to predate on its eggs and young. Climate change is also likely to cause increased stress to already stressed water environments. How fish evolved to breathe air Charlie Talks looks at how fish evolved to breathe air. One miracle that seems to baffle even the competent scientist, is how did complex organs, such as lungs, evolve from simple life forms. In reality, the answer is all around us. Just by looking at modern primitive species, it is possible to see the development of gills to lungs from when the first amphibians evolved 370 million years ago in the Devonian period, to the present day. In many ways, the evolution of tetrapods is one of the most monumental evolutionary events in the history of life, in fact lungfish are considered homologous to all lungs of higher vertebrates. But why did these aquatic organisms need to evolve in the first place, surely there was enough oxygen present in the water of oceans and rivers? At the time however, the growth of terrestrial plants meant that dead organic matter washed into rivers and into the sea, promoting algae and therefore allowing bacteria to thrive, using up much of the dissolved oxygen. This is similar to the effect of eutrophication of a small pond, but to a much larger scale, ultimately resulting in a lower concentration of dissolved oxygen. The air, however, has a much higher partial pressure of oxygen than in water, allowing for organisms with higher metabolic rates to develop. This allowed the eventual evolution of endotherms, such as mammals. Being able to breathe air also provided a selective advantage to early lungfish and tetrapods as they could swim in shallower water, evading predators and obtaining nutrients of their own. As with many organs, the lungs seen in early dipnoans (lungfish) and later in amphibians evolved from another organ with a different original role, the swim bladder in fish is primarily a hydrostatic organ, allowing a change in density of the fish as air enters or exits the cavity. This allows fish to move up and down in the water whilst maintaining equilibrium, much like a submarine letting in or pumping out water to move vertically. In some species of fish, the swim bladder has folds in its membrane, which is thin and is highly vascular, to allow transfer of oxygen to a dense network of capillaries. This was originally to allow the release of oxygen from oxyhaemoglobin into the swim bladder to increase its volume, and the subsequent absorption of oxygen back into the bloodstream, decreasing its volume. The capillary network and folded membrane paved the way for the development of the lungs, with the evolution of alveoli and other characteristics found in modern terrestrial organisms. Now dipnoans had the ability to breathe in air and in water, hence the meaning of dipnoan in Greek is ‘double-breathing’. As ideal as breathing air sounds, it does have its drawbacks. At 20ºC the water solubility of carbon dioxide is 28 times greater than that of oxygen, therefore in water, carbon dioxide removal doesn’t prevent a problem, but this would lead to severe respiratory acidosis in normal ventilation. As a result a new exchange surface, skin, would be used to remove CO 2 in amphibians. Since amphibians have no ribs or diaphragm, ventilation was achieved by swallowing air, carried out by rising the buccal cavity floor. Increases in efficiency in ventilation and gas exchange in more advanced organisms have since dealt with these problems, allowing a plentiful supply of oxygen. This allows birds to fly higher, terrestrial mammals to run longer, and more complex brains to develop; this adaptation truly changed the course of life forever. 20
Neptune Rake started development in 2014. Calum Gordon, director of Splash Gordon ltd realised there was a real need for such a tool to clear ponds and lochans of emergent weed and detritus. The rake is used at Shell Oil’s St Fergus gas terminal to keep their 1-acre fire pond clear of weed, it is also used at Dumfries House plus many other large estates. It takes just 10 minutes to set up the system, bolt the rake together, lay out gather rope to far shore, attach the winch to a suitable tree or ground anchor. The rake is sat on the float and the float is pulled to any area of any sized water body, it is easily deployed by pulling on both gather rope and winch rope, the rake slides off the float and lands on the lake floor. The winch is then used to haul the rake across the lake floor. The off-set tines of the rake force weed to zig zag up through the rake and jam, weeds are up rooted and cropped at their base, the rake also gathers detritus and sludge. The winch hauls the loaded rake right up onto dry land, two men then simply tip it forwards to dump the weed then set it back on the float for the next haul. Mobile pond life has to opportunity to return to the pond un harmed. Catching lungfish
Page 1 and 2: Edition 133 / Spring 2019 The Quart
Page 3 and 4: Front cover: Fishing for Patagonian
Page 5 and 6: Tory Leadership contest has started
Page 7 and 8: Aquatic Control Engineering HDPE La
Page 9 and 10: The white gold rush Patagonian toot
Page 11 and 12: the surface as the line sank. Previ
Page 13 and 14: The Plight of Patagonian Toothfish
Page 15 and 16: A Living Fossil, the Lungfish Austr
Page 17 and 18: A Living Fossil, the Lungfish Afric
Page 19: Surviving droughts During serious d
Page 23 and 24: This combination of pressure and co
Page 25 and 26: More Plastic than Fish in the Ocean
Page 27 and 28: polystyrene. But, what really worri
Page 29 and 30: it is an unfair battle, and all the
Page 32 and 33: Climate Change and Freshwater Ecosy
Page 34 and 35: Remembering Simon McKelvey Remember
Page 36 and 37: The Paul Coulson BLOG The Paul Coul
Page 38 and 39: The Paul Coulson BLOG a threat when
Page 40 and 41: “Learning from the Past to Inform
Page 42 and 43: IFM News IFM News Event Date Locati
Page 44 and 45: IFM News 44 If you haven’t renewe
Page 46 and 47: IFM News News from the London and S
Page 48 and 49: Breaking News Breaking News... How
Page 50 and 51: Book Review Book Review Understandi
Page 52: Members and their FISH Frank Partin

FISH 133 Spring 2019

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