Flamingolepis liguloides

The parasite that features prominently in the study we are looking at today is a tapeworm that lives in flamingoes - something that you might have already guessed by the parasite's genus name. The larval stage of the tapeworm Flamingolepis liguloides lives inside brine shrimps, which happen to be a major part of the flamingo's diet. Previous research has found that this parasite is capable of altering the behaviour of the shrimp as well as their colour and fat content.

Photo of F. liguloides larvae from the paper

In this new study, a team of scientists looked at the frequency of larval F. liguloides (and other tapeworms) in two brine shrimp species found in Mediterranean wetlands - Artemia parthenogenetica and Artemia salina - and how they related to the abundance of birds, the final hosts for those tapeworms. As the name indicates, A. parthenogenetica reproduces asexually (without mating), while A. salina is a more conventional sexually reproducing species.

Flamingolepis liguloides is not the only species of tapeworm infecting those shrimps, in fact each Artemia species harbours nine different tapeworm species each for a total of ten different tapeworms (both species of shrimps share a number of tapeworms in common). But F. liguloides is by far the most dominant, probably because flamingoes also happen to be the most numerous and long-lived birds in the area - the researchers estimated that flamingoes represented almost ninety percent of the bird biomass at those wetlands. Despite its dominance, F. liguloides does not seem to push aside the other tapeworms; the brine shrimps often harbour multiple species of tapeworms and the different parasites don't seem to get in each other's way. The fact that they have so many different species of parasites is also an indicator of the wide variety of birds that frequently visited the area. The Odiel marshes, where the scientists collected the asexual brine shrimps, is home for up to twenty thousand shorebirds during migration periods.

Photo of brine shrimps by Hans Hillewaert via Wikipedia

There were some seasonal patterns in infection prevalence. For the asexual brine shrimp, it ranged from a low of four percent to almost half the population being infected, whereas the parasite prevalence in sexual brine shrimps was consistently high, with tapeworms being found in over a quarter to almost three quarters of the shrimp throughout the year. The researchers found that such seasonal changes in the prevalence of some (but not all) of the tapeworms were associated with changes in abundance of the bird hosts. However, the scientists suggested that the consistently high tapeworm abundance in A. salinawas due to the areas they studied being protected areas that harbour thousands of birds, especially flamingoes, which flock there in huge numbers as their wetland habitats are destroyed elsewhere.

The high abundance of tapeworm infections simply reflects a high abundance in the bird hosts that harbour the adult worm that produces eggs that infect the brine shrimps. Therefore, bird watchers should perhaps be thankful for the presence of shrimps heavily infected by a wide variety of parasitic worms!

Reference:
Sánchez, Marta I., et al. (2013) "High prevalence of cestodes in Artemia spp. throughout the annual cycle: relationship with abundance of avian final hosts." Parasitology Research 112: 1913-1923.