Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Parasitic flatworms flout global biodiversity patterns

27.07.2015

The odds of being attacked and castrated by a variety of parasitic flatworms increases for marine horn snails the farther they are found from the tropics. A Smithsonian-led research team discovered this exception to an otherwise globally observed pattern--usually biodiversity is greatest in the tropics and decreases toward the poles.

The study, published in Ecology, makes a case for using host-parasite relationships as a tool to understand why there are typically more species--and more interactions between species--in the tropics than anywhere else in the world.


A trematode worm bites and sucks out the insides of an enemy species, with the eyespots of the victim's offspring still visible inside the attacker's gut. At least 20 species of trematode compete to parasitize and castrate marine horn snails (Cerithideopsis species), and such predatory interactions are more frequent in the temperate zone than the tropics.

Credit: Ryan Hechinger

"Unlike free-living species, parasites must use hosts as their habitats," said co-author Osamu Miura, former postdoc at the Smithsonian Tropical Research Institute in Panama and associate professor at Kochi University in Japan. "Wide-ranging hosts provide a nearly constant habitat for the parasites, regardless of latitude."

Such host-parasite systems are thus particularly useful for testing hypotheses about global biodiversity trends. Generations of scientists have tried to explain why biodiversity decreases from the tropics to the poles--a pattern known as the latitudinal diversity gradient. Suggested hypotheses include greater seasonal stability, more complex food webs, faster speciation rates and lower extinction rates in the tropics relative to higher latitudes. Because many of these variables influence each other, it is hard to test the effects of one factor independent of the rest.

"The cool thing about horn snails and their parasites is that we can actually test hypotheses about biodiversity," said lead researcher Mark Torchin, a staff scientist at the Smithsonian Tropical Research Institute. He explains that even across a widely variable geographic range--along the Pacific and Atlantic coasts from Central America to the subtropical United States--the horn snails serve as natural, standardized habitats for measuring parasite diversity. "It lets us do a real, apples-to-apples comparison when the habitat--the snails--is the same across this broad geographic region."

The Pacific horn snail (Cerithideopsis californica) and Atlantic horn snail (C. pliculosa) are two closely related species widespread in estuaries along the coasts from the tropics to the temperate zone. At least 20 species of trematode--a kind of flatworm--compete to parasitize and castrate the snails. The trematodes produce offspring that leave the snails and eventually infect migratory sea birds. So although the snails are restricted to their local habitat, the trematodes themselves are spread across vast distances by the birds.

Co-author Ryan Hechinger, professor at the University of California, San Diego's Scripps Institution of Oceanography, explains that the parasites' unusual life history allows the research team to simplify the question of how the latitudinal diversity gradient arose. Because the trematodes spread so quickly up and down the coast, they could rule out speciation rates as a factor affecting their pattern of distribution.

"So, if greater speciation rates cause the normal diversity gradient--decreasing from the temperate zone to the tropics--and if we preclude that from being a factor, we shouldn't see the usual pattern for these trematodes," Hechinger said. "That's exactly what we see in our study, suggesting that speciation does play a role in creating the normal latitudinal diversity gradient."

The research team collected snails and parasites from 43 field sites spread across five countries and 27 degrees of latitude in the Pacific and Atlantic Ocean, and found that parasite prevalence, diversity and competition rates all increased with higher latitude in a reversed diversity gradient. The reversed pattern suggests that local ecological factors also have a part to play in shaping biodiversity. In the tropics, environmental instability--such as from hurricanes or storm runoff--and greater snail death rates might decrease the available pool of snails for trematodes to parasitize. Conversely, greater stability and larger snail populations in the temperate zone sustain higher trematode species diversity over time.

The co-authors note that there are advantages to paying attention to parasites, which are generally overlooked despite being found everywhere. Apart from some research on humans, for example, there are few comprehensive studies looking at how parasite diversity changes in a single, wide-ranging species across latitude. Since the latitudinal diversity gradient generally holds true across the world, it remains important to understand how and why this pattern exists. "We now have a plan to conduct similar research in Asia to test the robustness of our findings on the other side of the world," said Miura.

The Smithsonian Tropical Research Institute, headquartered in Panama City, Panama, is a unit of the Smithsonian Institution. The Institute furthers the understanding of tropical nature and its importance to human welfare, trains students to conduct research in the tropics and promotes conservation by increasing public awareness of the beauty and importance of tropical ecosystems. Website: http://www.stri.si.edu.

Reference: Torchin, M.E., Miura O., and Hechinger, R.F. Parasite species richness and intensity of interspecific interactions increase with latitude in two wide-ranging hosts. Ecology. DOI:10.1890/15-0518.1

Media Contact

Beth King
kingb@si.edu
202-633-4700 x28216

 @stri_panama

http://www.stri.org 

Beth King | EurekAlert!

More articles from Life Sciences:

nachricht Bolstering fat cells offers potential new leukemia treatment
17.10.2017 | McMaster University

nachricht Ocean atmosphere rife with microbes
17.10.2017 | King Abdullah University of Science & Technology (KAUST)

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Ocean atmosphere rife with microbes

17.10.2017 | Life Sciences

Neutrons observe vitamin B6-dependent enzyme activity useful for drug development

17.10.2017 | Life Sciences

NASA finds newly formed tropical storm lan over open waters

17.10.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>