Phoresis has been well studied interaction in biology, and it has been reported in both vertebrates and invertebrates. An example of vertebrate phoresis is the remora (Perciformes: Echeneidae), whose first dorsal fin is modified into an oval sucker that allows it to attach itself to larger marine animals, and one example I’ve seen often in invertebrates is pseudoscorpions on beetles, particularly longhorns (Cerambycidae). But I recently learned that phoresis in invertebrates is a world about which I know nothing.
We collected some beetles in the Andes a few weeks ago. Nothing too eye-catching, just some scarabaeids that landed on the light trap. We collected a few and didn’t think much about them after that, so they stayed in a jar at the lab. I reviewed the contents of the jar earlier this week and saw something interesting: about 30-40 mites were floating around in the alcohol, and two beetles had this:
Beetle is roughly 3 cm long
I didn’t recognize these structures, at least not on a beetle we captured alive. We had seen molds on dead beetles that had a similar overall shape, but there was one catch: molds don’t have legs!
Definitely not a mold!
I did what I usually do when I’m stumped and have no immediate access to my books/computer: I turned to Twitter for help. Sure enough, I soon received replies regarding these animals. Christopher Taylor (@CatOfOrg) identified them as phoretic Uropodina mite deutonymphs, and gave some insight as to what that stalk-like structure was. After that, Wayne Knee (@whknee) added that these mites use liquid glue, and form the pedicel by moving ahead, and that the mite later detaches, leaving the pedicel behind.
Sure enough, I found that different mites have different types of pedicels: they can be long, short, irregularly shaped, straight or helically coiled, and they can be homogenous or formed by packed bundles of fibers [1]. These are to assure successful phoresis on their hosts. I also found that host selection can be either very specific (one single species of centipede [2]) or non-specific (25 different species of beetles from several families [3]), but in both studies there appears to be a tendency for selecting specific body parts from which to attach the pedicel.
For the second time this week, I was stumped by arthropods (the first time was by some odd little things), which I really enjoy, for it means I’m always learning something new! And, again, it proves that Twitter can be an excellent tool for learning and sharing information.
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1.- Bajerlein, D., et al., Morphological diversity of pedicels in phoretic deutonymphs of Uropodina mites (Acari: Mesostigmata), Arthropod Structure & Development (2013), http://dx.doi.org/10.1016/j.asd.2013.02.002
2.- Bloszyk, J., Klimczak, J. & Lesniewska, M., Phoretic relationships between Uropodina (Acari: Mesostigmata) and centipedes (Chilopoda) as an example of evolutionary adaptation of mites to temporary microhabitats, Eur. J. Entomol. 103: 699–707, 2006
3.- Bajerlein, D. & Bloszyk, J., Phoresy of Uropoda orbicularis (Acari: Mesostigmata) by beetles (Coleoptera) associated with cattle dung in Poland, Eur. J. Entomol. 101: 185-188, 2004
They go "Crunch" 