The case of the Chevroned Butterflyfish is a stark example of how human pressure on the world’s coral reefs is confronting certain species with ‘blind alleys’ from which they may be unable to escape, says Dr Morgan Pratchett of the ARC Centre of Excellence for Coral Reef Studies and James Cook University.
In a study published in the journal Behavioural Ecology and Sociobiology Dr Pratchett and Dr Michael Berumen of Woods Hole Oceanographic Institution (USA) warn that the highly specialized nature of the feeding habits of this particular butterflyfish – the distinctively patterned Chaetodon trifascialis - make it an extinction risk as the world’s coral reefs continue to degrade due to human over-exploitation, pollution and climate change.
“The irony is that these butterflyfish are widespread around the world, and you’d have thought their chances of survival were pretty good,” Dr Pratchett said today.
“But they only eat one sort of coral – Acropora hyacinthus – and when that runs out, the fish just disappear from the reef.”
The team found it hard to believe a fish would starve rather than eat a mixed diet, so they tested C. trifascialis in tank trials on a range of different corals. The fish grew well when its favourite coral was available – but when this was removed and other sorts of corals offered, it grew thin, failed to thrive and some died.
“We call these kinds of fish obligate specialists. It means they have a very strong dietary preference for one sort of food, and when that is no longer available, they go into decline. We still don’t have a satisfactory scientific explanation for this, as it seems like rather a risky tactic in evolutionary terms – but it must confer some advantage provided enough of its preferred food is available,” Dr Pratchett says.
The A. hyacinthus coral, which the butterfly fish feeds on, is itself highly vulnerable – to attacks by plagues of crown-of-thorns starfish (thought to be triggered by humans releasing excess nutrients onto the reef as sediment, fertilizer or sewage), to storms and to the coral bleaching caused by the heating of ocean surface waters to 32 degrees or more, which is thought to be linked to global warming.
“Although extremely widespread, the Chevroned butterflyfish may be at considerable risk of extinction following ongoing degradation of coral reefs around the world, because the coral itself is exceptionally vulnerable, Dr Pratchett explains.
“It is estimated that up to 70 per cent of the world’s coral reefs are now badly degraded, which usually involves the loss of this particular coral – and, when it goes, the C. trifascialis also disappear from the reef.
“To make matters worse, butterflyfishes are one of the main families of coral reef fishes being targeted by aquarium collectors. However, the specialized coral-eaters are clearly not suitable for keeping in aquaria - and often die because they cannot obtain their main food source.”
A previous case in which a coral-dependent fish vanished occurred in the case of Gobiodon a specialized coral-dweller known only from one site, Kimbe Bay in Papua New Guinea, which was thought by scientists to have possibly become extinct after its habitat was destroyed.
Researchers consider that such extinctions are likely to occur as part of the global mass extinction of species now taking place, and that marine ecosystems may be particularly vulnerable in that small changes in habitat or water quality can have a big impact on their species.
Dr Pratchett and Dr Berumen say theirs is one of the few studies so far to consider the evolutionary and ecological basis of dietary versatility, and has implications for the fate of specialised feeders throughout the animal kingdom.More information:
Dr. Morgan Pratchett | EurekAlert!
How does the loss of species alter ecosystems?
18.05.2017 | Deutsches Zentrum für integrative Biodiversitätsforschung (iDiv) Halle-Jena-Leipzig
Excess diesel emissions bring global health & environmental impacts
16.05.2017 | International Institute for Applied Systems Analysis (IIASA)
An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.
We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...
Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.
Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...
An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...
In the race to produce a quantum computer, a number of projects are seeking a way to create quantum bits -- or qubits -- that are stable, meaning they are not much affected by changes in their environment. This normally needs highly nonlinear non-dissipative elements capable of functioning at very low temperatures.
In pursuit of this goal, researchers at EPFL's Laboratory of Photonics and Quantum Measurements LPQM (STI/SB), have investigated a nonlinear graphene-based...
Dental plaque and the viscous brown slime in drainpipes are two familiar examples of bacterial biofilms. Removing such bacterial depositions from surfaces is...
23.05.2017 | Event News
22.05.2017 | Event News
17.05.2017 | Event News
23.05.2017 | Physics and Astronomy
23.05.2017 | Life Sciences
23.05.2017 | Medical Engineering