September 12, 2012
Red Swamp Crayfish Plays Host To Diminutive Crustaceans
April Flowers for redOrbit.com - Your Universe Online
The small ostracod, or seed shrimp, Ankylocythere sinuosa, lives on other crayfish and measures just half a millimeter in length. For the first time, Spanish scientists have found the ostracod in Europe.
It is possible Ankylocythere arrived 30 years ago with the invader crayfish Procambarus clarkii, but it is unknown whether it can infest other crustacean species or whether it benefits or damages the expansion of the already established red swamp crayfish.
Originally from the USA and Mexico, the red swamp crayfish has been present on Spain's Iberian Peninsula since the 1970's and its population is growing. The ostracod is also from North America, and because it totally relies on the crayfish for survival, it could have come to Europe at the same time, escaping discovery for decades.
The study, published in Hydrobiologia, aims to verify how the ostracod arrived on the European Continent, although the researchers feel "it is certain that it arrived with Procambarus clarkii".
"Ankylocythere sinuosa is common and abundant wherever there is the red swamp crayfish in Europe", explained Francesc Mesquita Joanes, lead author of the study and researcher at the Department of Microbiology and Ecology of the University of Valencia.
The ostracod is an epibiont, meaning it lives on the surface of another living organism. Epibionts are generally harmless to their hosts, making the relationship neutralistic, rather than parasitic. The ostracod, while causing no harm to the crayfish, cannot live without it. Ankylocythere lays its eggs on the crayfish and clings on while they develop. The majority of crayfish are infected and "adult specimens can have up to many hundreds of ostracods on them," reveals Joanes.
The research team took 203 red swamp crayfish from 12 different regions of the Iberian Peninsula, from Donana in the southwest to Catalonia in the northeast, between 2003 and 2009. In total, 147 of them had ostracods. The ostracods were present in practically all sampled regions.
"We have to remember that these epibionts can spread to other native species," noted Joanes.
The Spanish crayfish were compared to specimens living in the USA and scientists were able to discover that only the Ankylocythere traveled to Europe with the crayfish. The study outlines that "the crayfish did not transport all the possible epibionts present in its place of origin. Although P. clarkii could be infected with other epibiont ostracods in North America, it only brought with it one species to Europe."
The scarce diversity of these crustaceans could help its greater expansion in invaded areas. "We have to remember that these epibionts could spread to other native species," warns Joanes, outlining that it is necessary to study if the ostracod have any sort of effect on Aphanomyces, the plague of crayfish that is causing the extinction of native species.
Does the presence of Ankylocythere have any significance other than a scientific oddity? The researchers aren't sure, yet. For now, they say the ostracods just seem to be guests who do neither good nor bad to the crayfish. They caution that this is debatable until further studies can be made.
The ostracod would be considered to be "doing good" if they cleaned parasites or organic materials in contaminated areas. They would be considered to be "doing harm" if they feed off any part of the crayfish or the eggs of the female.
Awaiting new studies that confirm the effects of this relationship, the authors suggest that the ostracod could also spread to other invading or native crayfish, but the results are not very specific and there could still be unknown effects.