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 How molecules teeter in a laser field
18.01.2019 | Forschungsverbund Berlin

nachricht Discovery of enhanced bone growth could lead to new treatments for osteoporosis
18.01.2019 | University of California - Los Angeles

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Ten-year anniversary of the Neumayer Station III

The scientific and political community alike stress the importance of German Antarctic research

Joint Press Release from the BMBF and AWI

The Antarctic is a frigid continent south of the Antarctic Circle, where researchers are the only inhabitants. Despite the hostile conditions, here the Alfred...

Im Focus: Ultra ultrasound to transform new tech

World first experiments on sensor that may revolutionise everything from medical devices to unmanned vehicles

The new sensor - capable of detecting vibrations of living cells - may revolutionise everything from medical devices to unmanned vehicles.

Im Focus: Flying Optical Cats for Quantum Communication

Dead and alive at the same time? Researchers at the Max Planck Institute of Quantum Optics have implemented Erwin Schrödinger’s paradoxical gedanken experiment employing an entangled atom-light state.

In 1935 Erwin Schrödinger formulated a thought experiment designed to capture the paradoxical nature of quantum physics. The crucial element of this gedanken...

Im Focus: Nanocellulose for novel implants: Ears from the 3D-printer

Cellulose obtained from wood has amazing material properties. Empa researchers are now equipping the biodegradable material with additional functionalities to produce implants for cartilage diseases using 3D printing.

It all starts with an ear. Empa researcher Michael Hausmann removes the object shaped like a human ear from the 3D printer and explains:

Im Focus: Elucidating the Atomic Mechanism of Superlubricity

The phenomenon of so-called superlubricity is known, but so far the explanation at the atomic level has been missing: for example, how does extremely low friction occur in bearings? Researchers from the Fraunhofer Institutes IWM and IWS jointly deciphered a universal mechanism of superlubricity for certain diamond-like carbon layers in combination with organic lubricants. Based on this knowledge, it is now possible to formulate design rules for supra lubricating layer-lubricant combinations. The results are presented in an article in Nature Communications, volume 10.

One of the most important prerequisites for sustainable and environmentally friendly mobility is minimizing friction. Research and industry have been dedicated...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Our digital society in 2040

16.01.2019 | Event News

11th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Aachen, 3-4 April 2019

14.01.2019 | Event News

ICTM Conference 2019: Digitization emerges as an engineering trend for turbomachinery construction

12.12.2018 | Event News

 
Latest News

Additive manufacturing reflects fundamental metallurgical principles to create materials

18.01.2019 | Materials Sciences

How molecules teeter in a laser field

18.01.2019 | Life Sciences

The cytoskeleton of neurons has been found to be involved in Alzheimer's disease

18.01.2019 | Health and Medicine

VideoLinks
Science & Research
Overview of more VideoLinks >>>