As far as most laypeople know, all amoebas are soft-bodied creatures – sort of like microscopic versions of The Blob. In fact, though, amoebas of the Thecamoeba genus have a hard outer carapace. In the case of a recently-described new species of Thecamoeba, that shell resembles the wizard's hat worn by Gandalf in The Lord of the Rings. It's only fitting, therefore, that the microorganism has been named Arcella gandalfi.
Over the past several years, there had been reports of wizard-hat-shaped freshwater amoebas from various parts of Brazil. Until recently, however, too few of the creatures had been collected to verify that they indeed constituted a new species. That changed when biologist Jordana de Carvalho e Féres found high numbers of them in water samples she collected from the states of Amapá and Rio de Janeiro.
Working with a University of São Paulo team led by Prof. Daniel J. G. Lahr, she was able to obtain the measurements and images necessary to declare A. gandalfi a distinct species that's unique to South America. With a carapace measuring 81 micrometers wide by 71 micrometers tall, it's actually fairly big for a single-celled organism.
Judging by the number of Thecamoeba shells that have been found in the guts of predator microorganisms, however, it's unlikely that the carapace is a form of defence against enemies. Instead, Lahr believes that it's likely a means of storing moisture, when fluctuating water levels leave the amoeba high and dry. During those times, the shell could also serve as a means of protection against the sun's ultraviolet rays.
Scientists from the University of Maringá also took part in the research, which is described in a paper that was recently published in the journal Acta Protozoologica.