Researchers at the University of Leeds, Queen’s University Belfast and Stellenbosch University in South Africa looked at cannibalism among freshwater shrimp in Northern Ireland.
Dr Alison Dunn, Reader in Evolutionary Biology in the University of Leeds’ Faculty of Biological Sciences, who led the study, said: “Cannibalism is actually fairly common in nature. Our work is the first study to ask if cannibalism is affected by being parasitised.”
The research, published in Royal Society Open Science today, reports that although consumption of juveniles by adults is a normal feature of the shrimp’s feeding patterns, shrimp infected with the parasite ate twice as much of their own kind as uninfected animals.
They attacked juvenile shrimp more often and consumed them more quickly than did uninfected shrimp.
Mandy Bunke, a PhD student at the University of Leeds who was the key researcher on the study, said: “Although the parasite is tiny—similar in size to a human red blood cell—there are millions of them in the host muscle and they all rely on the host for food. This increased demand for food by the parasites may drive the host to be more cannibalistic.”
Dr Dunn added: “The parasite is quite debilitating. It takes over huge areas of the muscle, so instead of a nice transparent shrimp you get quite a chalky appearance because of muscles packed with the parasite. Interestingly, our group has also found previously that infected shrimp may be able to catch and eat less prey of other animal species. Perhaps cannibalism of smaller shrimp is the only way these sick animals can survive.”
The latest study also found that uninfected adult shrimp were less likely to cannibalize infected juvenile shrimp than uninfected juveniles.
Dr Dunn said: “The parasite is passed to its new host either when it dies and is eaten by another shrimp, or when one shrimp cannibalises another. But we observed that uninfected shrimp avoid parasitised food and that is good for the shrimp as it means that they can obtain food through cannibalism but still avoid parasitic infection. Infected shrimp don’t avoid infected juveniles. They consume infected and uninfected juveniles. This may be is because they are more hungry or because they are already infected so there is no incentive to avoid eating infected juveniles.”
Dr Dunn said: “Our research does not suggest any link between parasites and human cannibalism. There is evidence that parasites can affect human behaviour. A study led by Dr Glenn McConkey, also of the University of Leeds Faculty of Biological Sciences, has shown that the parasite Toxoplasma gondii directly affects the chemistry of the human brain. However, cannibalism for the shrimp, unlike in humans, is a significant source of food even in uninfected animals. It seems unlikely that a parasite would be under evolutionary pressure to influence cannibalism in humans.”
However, the study is important to understanding the extent of parasites’ influence on biological systems. The Gammarus duebeni celticus, the subject of the study, is being replaced in Irish waterways by the invasive species Gammarus pulex, which is native to Great Britain. The Open Science study suggests that the parasite Pleistophora mulleri may be playing a role in weakening Gammarus duebeni’s resistance.
Dr Alison Dunn at Leeds and Professor Jaimie Dick at Queen’s University Belfast are available for interview.
Contact: Chris Bunting, Senior Press Officer, University of Leeds; phone: +44 113 343 2049 or email email@example.com.
The full paper: Mandy Bunke et al., ‘Eaten alive: cannibalism enhanced by parasites,’ is published in Royal Society Open Science (2015) and is available at http://dx.doi.org/10.1098/rsos.140369 (DOI: 10.1098/rsos.140369 ).
Jessica Kwok and Ronaldo Ichiyama, International Spinal Research Trust (Feb 2018), £94,450
Dave Lewis and Colleagues in South Africa, HEFCE Global Challenge Research (Jan 2018), £48,000
Sarah Calaghan, Ed White, John Colyer, Isuru Jayasinghe, BHF (Jan 2018), £128,308
Christine Foyer and Alison Baker, HEFCE GCRF Grant (Jan 2018), £71,158
Alison Baker, Yun Yung Gong and Lindsay Stringer and ICRISAT India, HEFCE GCRF Grant (Jan 2018), £27,000
Graham Askew, Simon Walker, BBSRC (Jan 2018), £699,781
Jennifer Tomlinson, Royal Society (Jan 2018), £512,801
Alison Dunn, NERC (Dec 2017), £18,000
Jennifer Tomlinson, Royal Society-Research Fellows Enhancement Award (Dec 2017), £94,681
Helen Miller, AB AGri Grant (Dec 2017), £73,600
Simon Walker, Royal Society Enhancement Award (Dec 2017), £10,000
Carrie Ferguson, Bryan Taylor, Harry Rossiter, The Physiological Society (Dec 2017), £7,392
Ralf Richter, Royal Society (Dec 2017), £6,000
Christine Foyer, British Council Newton Fund (Dec 2017), £49,840
Adrian Whitehouse and colleagues in School of Chemistry and University of Liverpool, MRC (Nov 2017), £622,319
Michelle Peckham, Neil Ransom, MRC (Nov 2017), £495,159
Dave Lewis, British Council India (Nov 2017), £22,540
Hannah Dugdale, Royal Society (Nov 2017), £15,000
Elton Zeqiraj, Royal Society (Nov 2017), £15,000
Shaunna Burke, Cancer Research UK Innovation Grant (Nov 2017), £20,000
Alex O'Neill and colleagues in Chemistry, BBSRC (Nov 2017), £431,865
Jessica Kwok, Wings for Life (Nov 2017), £87,365
Tom Bennett, BBSRC (Oct 2017), £523,679
Neil Ranson, Darren Tomlinson, BBSRC (Oct 2017), £494,318
Nikita Gamper, BBSRC (Oct 2017), £490,426
Amanda Bretman and colleagues from UEA, NERC (Oct 2017), £430,886
Juan Fontana, Rosetrees Trust consumables grant (Oct 2017), £22,500
Helen Miller, DSM Nutritional Products AG (Sep 2017), £69,988
Neil Ranson, Juan Fontana, Mark Harris, Michelle Peckham, Ralf Richter, Peter Stockley, Patricija Van Oosten-Hawle and colleagues in Engineering, FMH and MAPS, Wellcome Trust Equipment Call (Sep 2017), £418,000
Jamie Johnston, Physiological Society (Sep 2017), £10,000
Frank Sobott, Adrian Goldman, Mark Harris, Andrew Macdonald, Stephen Muench, Sheena Radford and colleagues in FMH and MAPS, Wellcome Trust Equipment Call (Aug 2017), £415,000
Ralf Richter, David Brockwell, Eric Hewitt, Jessica Kwok, Emanuele Paci and MAPS/FMH, BBSRC (Jun 2017), £600,000
Eric Blair, Adrian Whitehouse, Nicola Stonehouse, Alison Baker, Richard Bayliss, Joan Boyes, Ryan Seipke, Sally Boxall and MAPS/FMH, BBSRC (Jun 2017), £376,000
Stefan Kepinski, Yoselin Benitez-Alfonso, Tom Bennett, Michelle Peckham, BBSRC (Jun 2017), £331,000
Roman Tuma, Lars Jeuken, Paul Millner, Sheena Radford, Peter Stockley and MAPS/FMH, BBSRC (Jun 2017), £222,000
Vas Ponnambalam, Darren Tomlinson, Stephen Wheatcroft, BHF (May 2017), £107,878
Graham Askew in collaboration with Bangor University, BBSRC (Mar 2017), £477,383
Stephen Muench, BBSRC (Mar 2017), £132,945
Nic Stonehouse, MRC (Mar 2017), £906,341
Bill Kunin, Steve Sait, BBSRC (Mar 2017), £602,831
Adrian Goldman, EU (Mar 2017), £546,576
Sheena Radford, Wellcome Trust (Mar 2017), £1,836,482
Tom Bennett, Royal Society (Mar 2017), £15,000
Jamie Johnston, Royal Society (Mar 2017), £15,000
Beatrice Filippi, Royal Society (Mar 2017), £15,000