"So, naturalists observe, a flea has smaller fleas that on him prey; and these have smaller still to bite ’em; and so proceed ad infinitum."
- Jonathan Swift

November 13, 2012

Amblyomma nodosum

The parasite being featured today is Amblyomma nodosum (image on the right - male top, female bottom) - a species of specialised tick that happens to be one of only three species of parasite that were found while examining three roadkilled giant anteaters from Minas Gerais, Brazil. There are 100 species of Amblyomma from around the world (33 of which are from Brazil) and they have been described from a variety of hosts from amphibians and reptiles to birds and mammals, but A. nodosum is a specialist that lives exclusively on the giant anteater (Mymercophaga tridactyla) and the collared anteater (Tamandua tetradactyla). It was also the most abundant of all the parasites found on the anteaters in the study we are featuring today, occurring in moderately high numbers (average of 58 ticks per anteater).

The second parasite that was found is the chigoe flea Tunga penetrans. Unlike A. nodosum, this ectoparasite infects a wide range of hosts, and while most fleas simply hop onto a host, drink up some blood and jump away, T. penetrans females burrow into the skin and *stay* there, feeding on blood and laying eggs. They only occurred in low numbers on giant anteaters and were found burrowing into the footpad and nowhere else on the body (see image below).

The third parasite found was also the sole internal parasite in the anteaters, the tapeworm Oochoristica tetragonocephala. Tapeworms from this genus are known to infect a range of hosts including lizards, snakes, and a variety of mammals. The larva needs to infect an invertebrate host, specifically an arthropod, before reaching the gut of a reptilian or mammalian host (by the said reptile or mammal eating the infected arthropod) and maturing into an adult worm. In the case of this species infecting the anteater, ants and termites are the most likely candidates for where the larval stages reside, given the host's specialised diet.

Relatively speaking, the giant anteater has very a sparse parasite fauna. Usually, a mammal of its size would be infected with a dozen or more different species of parasites. But because of its specialised diet and solitary life style, there are very few opportunity for most parasites (except specialists or very abundant generalists) to infect the giant anteater (as reflected by its paltry parasite fauna). Such an example shows how the ecology of the host organism can often shape what parasites it is infected with.

Photos from figures in the paper.

Frank R, Melaun C, Martins MM, Santos AL, Heukelbach J, Klimpel S. (2012) Tunga penetrans and further parasites in the giant anteater (Myrmecophaga tridactyla) from Minas Gerais, Brazil. Parasitology Research 111:1907-1912

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