The Burrowing Crayfish Engaeus lyelli
Engaeus crayfish are known as the burrowing or terrestrial crayfish which are generally all very small species usually under 70 mm head to tail. Engaeus lyelli has a widespread distribution and is considered the largest of all the Engaeus species. The large size and taxonomy of the species has led to much consternation and various authors have disagreed with its designation and affinities. Gan et al 2014 ran he complete mitogenome of the Australian land crayfish Engaeus lyelli to help clarify the situation.
Thirty five described Engaeus species are found in Australia with twenty three of those found in Victoria. The Australian Crayfish Project (ACP) is researching all these species and E. lyelli has been under research for the last 8 years.
Horwitz 1990 redescribed the species and stated: The largest male found was 28.7 mm carapace length. Mature females ranged from 18.8 to 32.4 mm carapace length. The largest non-reproductive female was 27.7 mm carapace length. Horwitz 1990 did not record any berried females so the discovery by the ACP of females with eggs greatly increases the knowledge base on this species. This female from the Seymour area in November 2015 has 114 eggs, weighs 16.66 grams with an OCL 30.45 mm has eggs 2.5 mm long and 1.9 mm wide.
Engaeus lyelli has been assessed as Least Concern by the International Union for the Conservation of Nature and Natural Resources (IUCN). Although this species has a relatively restricted range, with an estimated extent of occurrence 11,200 km2, it is not impacted upon by any major threat processes. Monitoring of the population is suggested as habitat loss and degradation occurs within parts of its range, and climate change may pose a significant future threat to this specie. (IUCN 2015)
The IUCN states under distribution: This species is endemic to Victoria, Australia. It is most commonly found north of the Great Dividing Range from the Grampian Ranges in the west to near Myrtleford in the east, and it does not appear to extend far from the foothills of the Great Dividing Range in Victoria (although its northwards range has not been thoroughly investigated). The distribution is characterized by distinct gaps in its range, with gaps occurring between Moyston and Beaufort, in the Lerderderg River drainage region, between Ballarat and Daylesford, and in the Seymour-Yea region (although this gap may be due to insufficient sampling) (Horwitz 1990).
Engaeus lyelli is a riparian zone species found along the sides of creeks, billabongs and dams. It is also found in close proximity to other Genera like Cherax, Geocharax and juvenile Euastacus freshwater crayfish. Specimens are typically collected from their burrows by digging, however when no other crayfish species are present they can be collected by scoop net from ponds and dams in relatively high numbers. Burrows have an open entrance, usually 2-3 surface entrances along the sides of the water body, entrances are typically above the water line but these are in high water level fluctuation areas, have several subsurface burrows that travel down into the water table and all burrows contained water at the bottom. Most burrows sampled were relatively new burrows with fresh material at the surface, however most animals were captured 350-500 mm deep so not exceptionally deep on the scheme of things.
References & Further Reading
Doran, N. and Horwitz, P. 2010. Engaeus lyelli. The IUCN Red List of Threatened Species 2010: e.T153693A4532851. http://dx.doi.org/10.2305/IUCN.UK.2010-3.RLTS.T153693A4532851.en. Downloaded on 22 November 2015.
Horwitz, P. (1990). A taxonomic revision of species in the freshwater crayfish genus Engaeus Erichson (Decapoda: Parastacidae). Invertebrate Taxonomy 4: 427‐614.
DOI:10.3109/19401736.2014.908361Han Ming Gana*, Mun Hua Tana, Yin Peng Leea, Mark B. Schultzb & Christopher M. Austin. The complete mitogenome of the Australian land crayfish Engaeus lyelli (Clark 1936) (Crustacea: Decapoda: Parastacidae)
ACP DATA BASE
Collection GPS Coordinates and specimem information is only available to ACP Members to
view the collection data base for E. lyelli “CLICK HERE”
Excel database spreadsheet
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