Jim wrote, back in May 2008

> I'm gonna go out on a limb here. Gotta do it, as out on limbs is where the ripe fruit hangs.  What we have been calling "Nosema ceranae" may or may not be actual Nosema ceranae.  What we have been calling "Nosema apis" may not be Nosema apis, either.  One or both of what we are seeing may be a variant of "Nosema bombi" that jumped hosts from Bumblebee to Honey bee.

Me:

This question has kept me thinking for the past 9 months, and has
given birth to this collection of obscure facts:

> Nosema bombi infects multiple bumble bee (Bombus) species, and Nosema apis and Nosema ceranae are known from western (Apis mellifera) and Asian honey bees (Apis cerana), respectively.  Although the phylogenetic relationship of Bombus spp., A. cerana, and A. mellifera is unambiguous, the phylogeny of their respective Nosema parasites is less clear. Different analyses using almost identical GenBank submissions have yielded conflicting results, placing N. apis closer to N. ceranae, N. apis closer to N. bombi, or N. bombi closer to N. ceranae.

> Nosema bombi infects a number of different host tissues, which may explain why infection in multiple bumble bee species is observed. This low host specificity could have facilitated host-switching by ancestral N. bombi stock to Asian honey bees. In addition, virtually ubiquitous bumble bee species (300 in total) have undoubtedly had historical contact with Asian honey bees, which could have aided host-switching. A second hypothesis involves an ancestral N. ceranae host switching to an ancestral lineage of bumble bee. Similar distribution patterns support this argument, because home ranges of ancestral Asian honey bees and some bumble bee species likely overlapped.

> Recent work suggests N. ceranae may be the main contributing factor to the bee die-offs in Europe. Preliminary data suggest fumagillin, an antibiotic used to control N. apis, is effective against N. ceranae. However, because fumagillin was ineffective against N. bombi in the bumble bee Bombus occidentalis and, given the above noted similarities shared with N. ceranae, i.e., infection of multiple tissue types, further work is needed.

* * *

> Bombus terrestris was first used as a managed commercial pollinator about a decade ago. The industry is now flourishing worldwide. The natural area of distribution of B. terrestris covers all of continental Europe, the south of England, and the south of Scandinavia. Companies in Europe specialize in providing colonies at various stages of development. The main exporting countries worldwide are the Netherlands, Belgium, and Israel; the main importing countries are Mexico, Japan, China, Korea, Jordan, Spain, and Italy. In Japan, this species has been used for pollination of tomato plants in glasshouses since 1991. More than 40,000 colonies of B. terrestris are imported into Japan from Europe each year.

> Japanese companies have started commercializing native species of bumblebees. B. ignitus colonies have been developed and sold in Japan since 1998; this practice is expected to reduce the ecological risks posed by introduced species. However, queens of B. ignitus collected in Japan have been exported to the Netherlands, where the colonies are mass-produced. Those colonies are then reimported into Japan for commercial sale.

-- 
Peter L Borst
Danby, NY  USA
www.people.cornell.edu/pages/plb6

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