A case of hyperparasitism on a Canadian woodpecker

A few weeks ago I was cc’d on an email of Meredith Blackwell from Louisiana State University. She had received an inquiry about an ectoparasitic fungus on a feather louse and had identified it as Trenomyces sp., a member of the Laboulbeniales.

Here’s how it all started: Heath Proctor from the University of Alberta had washed a recently killed Yellow-bellied Sapsucker (Sphyrapicus varius), a woodpecker. The wash resulted in many mites and a single feather louse (for those with a fetish for Latin names: the species is Penenirmus auritus, a representative of the order Phthiraptera). She mounted the feather louse on a microscope slide and examined it under a light microscope. What she found is not something you observe every day. As you can see on the photograph below, things are sticking out of the louse’s body. It was soon clear that each of these was a fungal thallus, which some researchers interpret as a “highly reduced hyphal system”  (Santamaría 1998, Tavares 1985).

It must be a member of the Laboulbeniales, Heather thought. So she emailed Meredith Blackwell, who thought of me to identify this fungus to species level. Laboulbeniales are a specialized group of fungi that parasitize invertebrates. There are 2,100 described species (although much more diversity is expected; Weir & Hammond 1997, Haelewaters & Pfister 2015), which have a wide array of hosts—mites, millipedes, cockroaches and termites, beetles, earwigs, flies, true bugs, and others.

Earlier this week I finally remembered that I had the slide somewhere in my loan cabinet, so I decided to spend some time on this. There are only five species in the genus; reading through the descriptions and looking at the only available plates (from 1926!), I am sure this is Trenomyces circinans. The description of this species is as follows:

In the female there are usually from two to four perithecia, sometimes only one. When young there are strongly circinate, the curved or recurved habit often less pronounced at maturity; the stalk relatively long, slender and abruptly distinguished, sometimes even longer than the body of the perithecium, which is broader distally; […] the apex distinguished by four symmetrically places, somewhat spreading lobes, which form a crown about the pore, more highly developed than in other species, and which are subtended by a slight constriction, accentuated by the slightly convex margins of the tip below. (From Thaxter 1926.)

So far, T. circinans has only been found in California, Rhode Island, and Argentina, which means that this find marks a new record of Laboulbeniales for Canada!

References: 
Haelewaters, D., and D.H. Pfister. 2015. Cryptic diversity in the Hesperomyces virescens species complex (Ascomycota, Laboulbeniomycetes, Laboulbeniales). Joint International Conference “Botany 2015” 25 to 29 July 2015, Edmonton, Alberta, Canada.
Santamaría, S. 1998. Laboulbeniales. I. Laboulbenia. Flora Mycologica Iberica 4: 1-186.
Tavares, I.I. 1985. Laboulbeniales (Fungi, Ascomycetes). Mycologia Memoir 9: 1-627.
Thaxter, R. 1926. Contribution towards a monograph of the Laboulbeniaceae. Part IV. Memoirs of the American Academy of Arts and Sciences 15: 427-580, Plates I-XXIV.
Weir, A., and P.M. Hammond. 1997. Laboulbeniales on beetles: Host-utilization patterns and species richness of the parasites. Biodiversity and Conservation 6: 701-719.