Month: October 2015

Is That a Wombat on Your Belly, Or Are You Just Happy to See Me?

I attended a Ph.D. defense a few weeks ago on the effects of salmon lice (which are copepods, not insects) on their juvenile hosts. The student showed some gory photos and pointed out that for such a little fish, carrying a louse was like a human lugging around a raccoon on his back. Some mites can be just as burdensome, such as this Macrocheles muscaedomesticae (Scopoli) attached to the abdomen of an unfortunate Drosophila hydei Sturtevant.

Scanning electron micrograph of a Drosophila hydei carrying a female Macrocheles muscaedomesticae (image by HP)

Scanning electron micrograph of a Drosophila hydei carrying a female Macrocheles muscaedomesticae (image by HP)

Females of many species of Macrocheles (Mesostigmata: Macrochelidae) hitch rides on winged insects to move from a place to place, a phenomenon called phoresy. Strictly phoretic organisms do not feed on the host while attached. A great many mite taxa fall into this ‘purely phoretic’ category. Others may facultatively snack on the host while in transit. My colleague Lien Luong has investigated one such mite species, Macrocheles subbadius (Berlese), and its cactus-associated host Drosophila nigrospiracula Patterson & Wheeler. When Lien moved to the University of Alberta it proved difficult to replicate the system, in part because cacti are not common in this part of Alberta.  Compost bins are abundant, however, and Lien and her students are investigating the ecological relationship between two compost-associated species, Macrocheles muscaedomesticae and Drosophila hydei. Does M. muscaedomesticae feed on its host while attached, or is it just holding on? One way to test this is to determine whether the mite’s mouthparts pierce the fly’s integument. In this N = 1 sample, the mite just seems to be holding on firmly, probably uncomfortably so from the fly’s point of view.

mite biting medium close

Piercing or just pinching?

 

mite biting close

Looks like pinching, probably painfully.

But by definition, facultative parasites aren’t always parasitic. More mites must be examined, and other lines of evidence followed, such as presence of melanized wounds on hosts after the mites have dropped off, or presence of Drosophila DNA in the guts of the Macrocheles.

 

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Brazilian Beauties

A couple of weeks ago my colleague Fabio Akashi Hernandes* from the Universidade Estadual Paulista sent me the file for a poster that I immediately printed on high-gloss paper and proudly affixed to the door of my office. The poster depicts some of the feather mites that Fabio has found on birds from Brazil and a few other tropical countries. Eye candy for acarologists! They are all scaled to the mm mark at bottom right, where you can see the gigantic Laminalloptes phaetontis (Fabricius) from tropicbirds. Among the selected mites are the hoatzin-dwelling Opisthocomacarus umbellifer (Trouessart) (mite #40) in which both sexes are adorned with feather-like setae of unknown function. Typically, though, male feather mites are more elaborate than females. The poster includes species whose males have vicious-looking hind legs (e.g., 1, 28), or are asymmetrical (e.g., 31, 32, 58), or are very well-endowed (20).

Fabio is doing some marvelous work on taxonomy and ecology of these mites, including the very recent discovery of a host-switch from wild cuckoos to domestic poultry. But even though he and his colleague Michel Valim have been working hard to describe new species, at least 80% of bird species in Brazil have yet to be investigated for their acarofauna. Many more wonders await.

Click on the poster image then mouse over and click to magnify.

Fabio's Feather mite poster 6 Oct 2015 sml

*abakashi@gmail.com