Major Group: Insecta
Order: Ephemeroptera
Family: Coloburiscidae
Genus: Colobruscoides
This family is represented in Australia by a single genus, Colobruscoides.
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Descriptive Features: head hypognathous
length of antennae approximately equal to width of head
mouthparts prominent and modified for filter feeding, mandible, maxillary palp and labial palp all with brush of long setae, both maxillary palp and labial palp 2-segmented
oral gills present
legs strongly spinose, fore femur, fore tibia and mid femur each with dense fringe of long setae on anterior margin
tarsal claws smooth
gills on abdominal segments 1-7, upper lamella bifid and strongly spinose, lower lamella fibrilliform
inner margins of caudal filaments with dense fringe of medium length setae, scattered short setae on outer margins
Total length: up to 20 mm
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Coloburiscoides giganteus |
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Taxonomic Checklist: Species
Coloburiscoides giganteus Tillyard
Coloburiscoides haleuticus Eaton (nymph unknown)
Coloburiscoides munionga Tillyard
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Distribution: NSW, Vic
Sensitivity Rating: SIGNAL grade 8
Functional Feeding Group: filtering collectors
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Pipers Creek, Kosciusko National Park NSW |
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Ecology: Instream habitat: Coloburiscid nymphs are restricted to fast currents in cool waters, and can live in torrential flows. While these nymphs are generally found where the substratum is stony, they can also occur on submerged logs if the current is fast.
Feeding ecology: Although the large spiny coloburiscid nymphs appear predacious, they are filter feeders and collectors of fine organic particles from the stream current using mouthparts equipped with brushes and the first two pairs of legs fringed with long hairs.
Habit: The rigid spinose gills and spines on their legs are used to anchor themselves between rocks against fast currents. Nymphs swim with a quick nodding swimming motion which has given rise to the common name ‘stream horses’. The caudal filaments are used to propel the animal through the water.
Life history: Females of Coloburiscoides haleuticus are known to lay 2000 to 12 000 eggs. Eggs of all Coloburiscidae species have adhesive structures to anchor them to the substrata. Nymphal development ranges from six months to two years, with emergence of most species being directly from the water, i.e. final moult occurs underwater, at dusk. The emergence period varies, generally occurring from spring to early autumn.
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Information Sources: Dean & Suter 1996, Peters & Campbell 1991, Gooderham & Tsyrlin 2002
Key to Species: Suter et al. 2009
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