Field of Science

Adorable apusomonads

Behold, purveyors of tiny soil flagellates: today, Santa brings you not one, but two whole species of Apusomonas. In fact, both described species of this, poor neglected genus. That's right, I've seen 'em all*, and after this post, you will too.

*I'm sure there's plenty more out there who've yet to encounter the microscope. Or be paid any attention to if seen. In fact, these may in fact be new species for all I know. They do fit their respective described ones quite nicely though, I think.

Apusomonas is a member of the Apusomonads, a group that includes Apusomonas, Amastigomonas, then Thecamonas, etc (as of Cavalier-Smith & Chao 2010 Protist) and, according to David Patterson (presumably) at Micro*scope, Etceterix etcetera (noticed by Opisthokont). Apusomonads seem to lean towards branching as sister to opisthokonts. They make their living by nibbling on bacteria, which they crawl over and ingest at their posterior ventral surface. Apusomonads are fascinating from both morphological and evolutionary perspectives, and perhaps if you prod Opisthokont persistently enough, he'll eventually dust off his blog and give these adorable creatures their deserved publicity.

For now, enjoy their strange and amusing mode of motility. By the way, the flagellar basal bodies are located at the kink in the proboscis, not within the cell body proper as in normal eukaryotes. Considering there's a strong tendency for the flagellar basal bodies to be fairly closely associated with nucleus among normal, non ass-tailed (opisthokont) eukaryotes, this is quite odd.

A.proboscidea Type species. First described in 1922.

Differs from A.proboscidea in having a bit of a kink on the left side of its body. (it's crawling on the coverglass here, so it's upside down/ventral side up). Seems to have only been reported in Australia thus far. Now we know it lives in North America too (or some sort of new species, but I doubt it).

A.proboscidea (left) and A.australiensis (right) from their respective Micro*scope pages:

Want to find your own? Grab some soil, put in a dish and fill with some water. Let it stand for a couple of days, and the apusomonads should crawl out of their cysts. I placed coverslips on the surface, which tends to attract benthic-y crawly things. After about 3 days, the coverslips were transferred to the slide, and there was about one apusomonad per cover slip (n=2, heh). Careful though: they're pretty small – around 10µm. A.australiensis is slightly bigger, at least of my two specimens. Good luck!


  1. I guess I remember when you saw those!
    I hope to have good luck at growing my own soil

  2. They are very fun to watch. Videos are working fine for me.

    I love coming over here to get regular updates on the word of your big bugs (comparitively speaking). Even if I do only read the first three letters of some of the longer taxon names :p


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