Fieldwork in Japan (part 4)

The last day of collecting, we hopped on a ferry and crossed the Ariake Sea to Mount Unzen in Nagasaki Prefecture. Mount Unzen, known for its violent eruptions, had its last activity between 1991 to 1994 when numerous pyroclastic flows buried houses and spewed toxic gas. When driving on Unzen, I could see steam and smell sulfur in certain areas. Some well-known hot springs, including the aptly named Unzen Hell, sit atop these vents.

Japanese feather millipedes, Brachycybe nodulosa (Verhoeff, 1935)

We collected millipedes at a couple of sites on Mount Unzen. We were looking for the andrognathid millipede Brachycybe nodulosa (Verhoeff, 1935) at the first site, and the xystodesmid Riukiaria marinae (Golovatch, 1978) at the second site. Notably, B. nodulosa is the closest relative of the Appalachian species, Brachycybe lecontii Wood, 1864 (Brewer et al., 2012). It’s even more closely related to B. lecontii than is Brachycybe petasata Loomis, 1936, which is sympatric with B. lecontii in the Southern Appalachian Mountains.

The city of Shimabura with Mount Unzen way in the background

We searched in several Cryptomeria forests without finding B. nodulosa, then eventually found them in the fourth spot. Their rarity is similar to B. lecontii, and often ideal-looking habitats are searched without finding a single individual. Tsutomu is familiar with collecting B. nodulosa and knew to spend less than about 15 minutes at a site then move onto the next one. Tsutomu found the first B. nodulosa on a Cryptomeria log. The microhabitat of B. nodulosa is similar to B. lecontii in that they occur on dead logs that are still intact and firm but with loose bark. In contrast to B. nodulosa, the species B. lecontii seems to like Tulip poplar. I was struck by the orange hue of B. nodulosa that differs from the pink color of B. lecontii.

The cryptodesmid millipede Kiusiunum

Co-occuring with B. nodulosa on the same cedar log, we found the millipedes Kiusiunum Verhoeff, 1942 (Cryptodesmidae) and Kiusiozonium Verhoeff, 1941 (Hirudisomatidae). These three millipedes are dorsoventrally flattened and chemically defended with either alkaloids or alcohols. The odor of Kiusiozonium is similar to the Appalachian millipede Petaserpes that has a camphor (Vicks VapoRub-like) odor.

The hirudisomatid millipede Kiusiozonium

Cryptomeria japonica forest from afar (C. japonica trees in foreground)

Cryptomeria japonica forest closeup

With a couple hours before the ferry departed, we visited the type locality of R. marinae on the south slope of Mount Unzen. The site consisted of a nice dark cedar forest with a thick layer of spongy decaying cedar duff. In a small gully, I found individuals of B. nodulosa, Kiusiunum, and a Hyleoglomeris with a white stripe near its head. In our 30 minutes of collecting, we didn’t find R. marinae. That’s not surprising and if we would have found an individual it would have been lucky given that Japanese xystodesmids are decidedly nocturnal and patchy in distribution.

The pill millipede Hyleoglomeris

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3 Responses to Fieldwork in Japan (part 4)

  1. Lim se-hyeon says:

    Dear Mr. Marek
    Hello! I’m highschool student in korea.
    I’m interested in millipede, especially in Xystodesmus or Pachydesmus. First of all, My english isn’t good, so maybe some expressions are inappropriate. I’m sorry about that. The thing is, i get some uncertain specimen that is presumed genus pachydesmus(or xystodesmus). But i can’t find any data about the genus’s morphological key point.
    You are specialized in this part.
    So If you don’t mind, l’d like to get reply about genus pachydesmus or xystodesmus.

    I lookfoward to hearing from you

    • pmarek says:

      Hi Lim,
      That sounds like a fascinating discovery! It’s probably Xystodesmus or Levizonus (even perhaps Koreoaria). It is likely not Pachydesmus because that genus only occurs in the eastern United States. Pachydesmus bazaensis from Changwon City is very likely a Xystodesmus; however, that has not been recollected since the 1940s so it remains “Pachydesmus”. I would be happy to look at any specimens that you find. It would be helpful to see color images of the top of the millipede. If you could take a picture of the underside of the millipede such as in Figure 2 of this article——then that would be helpful too.
      All the best,
      Paul Marek

  2. Deren Ross says:

    Oops!…missed part 4. Great work!

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