Polydesmida: Tasmaniosoma
Image of Tasmaniosoma armatum by Hans Hendrickx.
Tasmaniosoma is currently the largest genus of Tasmanian Polydesmida, with 19 named, endemic, H+19 species. Several Tasmaniosoma species have handsome colour patterns when alive (see below), but very little colour after long preservation in alcohol. Others, like T. armatum (see above), are uniformly reddish with persistent colour. A number of Tasmaniosoma species have three transverse rows of dome-like bumps on their tergites (see below).
Tasmaniosoma clarksonorum, freshly preserved.
Tasmaniosoma hickmanorum, freshly preserved.
SEM views of midbody tergites of Tasmaniosoma warra (A, with smooth surface) and T. barbatulum (B, with three transverse rows of bumps). Scale bars = 0.5 mm
The largest Tasmaniosoma species are ca 18 mm long as adults. They are found in loose litter and under tree bark, and almost never in the soil or in rotting logs. They have a distinct preference for eucalypt forest, woodland and scrub. As with other Tasmanian dalodesmids, Tasmaniosoma species can only be positively identified by closely examining the gonopods of mature males. However, as shown in the maps below, some species have small ranges. Use the maps to help you eliminate possibilities.
Bonham et al. (2002), Mesibov (1999, 2010a), Verhoeff (1936)
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The armatum group: tergites smooth, body a uniform reddish-brown.
T. alces Mesibov, 2010
Males up to ca 15 mm long
Note the remarkable fishtail-shaped 'wings' on the gonopods
Only known from a small area on the southern East Coast
T. armatum Verhoeff, 1936
Males up to ca 15 mm long (see image at top of page)
Look for two Y-shaped processes on each gonopod
Very common in eastern Tasmania, and apparently introduced in a few places outside its natural range
T. maria Mesibov, 2010
Males ca 15 mm long
Left gonopod from centre-line of body (left) and from head (right)
Known only from Maria Island
T. orientale Mesibov, 2010
Males ca 16 mm long
The long lateral 'arm' of the gonopod is sometimes forked at the tip, sometimes not
Common in the northern part of the East Coast and Eastern Tiers
T. warra Mesibov, 2010
Males ca 16 mm long
Common in wet forest in the Huon district; also found on South Bruny Island
The clarksonorum group: tergites with three rows of low bumps (see SEM at top of page), gonopod with 2 or more clumps of stout bristles (setae), body colorfully patterned but colour fades in alcohol.
T. barbatulum Mesibov, 2010
Males ca 10 mm long, live colour not yet known
Known from Scamander to St Marys on the northern East Coast, and inland in the Fingal Valley
T. clarksonorum Mesibov, 2010
Males ca 11 mm long (see image at top of page)
Common in wet forest in the Northeast
T. compitale Mesibov, 2010
Males to ca 15 mm long
Note tall, thin 'arm' on outer side of gonopod tip
Common in the far Northwest
T. fasciculum Mesibov, 2010
Males ca 11 mm long
Limited area in north central Tasmania
T. fragile Mesibov, 2010
Males ca 12 mm long, medium brown with yellow on underside
Known from the central East Coast and the Eastern Tiers
T. hickmanorum Mesibov, 2010
Males to ca 16 mm long (see image at top of page)
(A) Gonopods in situ, a bit foreshortened; (B) tip of left gonopod from head, showing branch crossing behind; (C) left gonopod from head
Common in western Tasmania but replaced by T. compitale in part of the Northwest
australe and bruniense: tergites smooth; the solenomere (gonopod branch carrying the sperm channel) is broad, flattened and on the outside of the gonopod apex; mature females have a swelling on the far end of the leg 2 prefemur.
T. australe Mesibov, 2010
Males ca 18 mm long, uniformly medium brown
Inland south central Tasmania from Maydena to Southport
T. bruniense Mesibov, 2010
Males ca 14 mm long, dark brown with small pale patches on paranota
Left gonopod from outside (A), head (B), centre-line of body (C) and rear (D)
Only found on South Bruny Island
hesperium and laccobium: tergites smooth, live colour not yet known; gonopods with a particular arrangement of 4 branches at the tip
T. hesperium Mesibov, 2010
Males ca 12 mm long
Left gonopod from centre-line of body (left) and from rear (right)
So far known only from two sites in the Southwest
T. laccobium Mesibov, 2010
Males ca 12 mm long
Left gonopod from centre-line of body (A), rear (B) and side (C)
So far known only from Lake Sydney in the far southern mountains
decussatum and gerdiorivum: tergites with 3 rows of very low bumps; the solenomere (gonopod branch carrying the sperm channel) is broad, flattened and on the inside of the gonopod apex; gonopods with peculiar 'shelf' at base (hard to see)
T. decussatum Mesibov, 2010
Males ca 11 mm long, live colour not known, but long-preserved animals pale with reddish speckling
Common in wet forest in the eastern part of the Northeast
T. gerdiorivum Mesibov, 2010
Males ca 10 mm long, pale yellow-brown with reddish mottling
Common in wet forest in the western part of the Northeast, with one record from north central Tasmania
Miscellany: 2 species not obviously related to other Tasmaniosoma
T. aureorivum Mesibov, 2010
Males ca 13 mm long, live colour not yet known, tergites smooth
Left gonopod from rear (A), side (B) and head (C)
Apparently rare in south central Tasmania, near Maydena
T. cacofonix Mesibov, 2010
Males ca 14 mm long, pale greenish yellow with red speckling towards rear on each tergite, tergites smooth
Common in dry forest, woodland and heath in the eastern part of the Northeast