Mount Glorious spiny crayfish  (Euastacus setosus)

The Mount Glorious spiny crayfish is classified as Critically Endangered (CR) on the IUCN Red List (1).

The Mount Glorious spiny crayfish (Euastacus setosus) is a highly threatened crayfish, of the Euastacus genus, which is the largest of the ten Australian crayfish genera and includes some of the largest and rarest species of crayfish in the world (2).

Often broadly referred to as the ‘spiny crayfish’, many species in the genus Euastacus are armed with prominent and well-developed spines. However, the Mount Glorious spiny crayfish has greatly reduced spines and, along with other less spiny species in the genus, it has been grouped into a distinctive complex from south-east Queensland, known as the setosus complex (3).

Like other crayfish, this large, freshwater species has a carapace that protects the head and internal organs. The six segments of the abdomen are individually encased, with a flexible membrane between them to allow movement. Crayfish also have a pair of large fore-claws, followed by four pairs of walking legs and then four pairs of small swimming legs, called ‘swimmerets’. These swimmerets are covered with fine hairs, to which the female attaches her eggs. A central tail flap is surrounded by four other flaps that are used to move the crayfish rapidly through the water, as well as curling up to form a brood chamber. The eyes are each borne on an eyestalk, while a pair of large feelers (or antennae) and a pair of small, fine, centrally-located feelers (or antennules) make the crayfish’s sense of touch and taste particularly sensitive.

The Mount Glorious spiny crayfish is endemic to Australia. It is known only from the headwater tributaries of the Pine River, near Mount Glorious, Brisbane, where it occurs in a small number of sites at elevations above 500 metres (1) (2).

It is possible that the Mount Glorious spiny crayfish occurs elsewhere in the surrounding D'Aguilar Range, although extensive clearing of rainforest in the area means that suitable remaining habitat for this species is limited (1) (2).

A freshwater crayfish, the Mount Glorious spiny crayfish inhabits the cool waters close to the source of creeks and streams in areas of rainforest. Like other species of Euastacus, this species prefers heavily shaded, well-oxygenated waters, where it can burrow under logs and rocks (1) (2).

Very little specific information is available about the biology of the Mount Glorious spiny crayfish.

In general, freshwater crayfish have strong jaws and two pairs of secondary jaws, called maxillae, which allow them to consume a wide variety of both plant and animal matter (4) (5). Most crayfish are nocturnal, remaining in burrows during the day, or under stones and logs (5).

Breeding typically occurs in the autumn in most Euastacus species, when the male transfers sperm to the female to fertilise the eggs. In some species the first pair of appendages on the abdomen has grooves, along which the sperm flows, although the sperm may also be transferred to the female as a spermatophore (4). The female typically lays a large clutch of eggs which are attached to the bristles on the swimmerets, where they remain for the whole incubation period. Unusually among crustaceans, crayfish do not have a larval stage (4) (5).

Chemical signals are thought to play an important role in the crayfish life cycle, and may have a role in courtship, brood care and aggressive interactions between individuals. Aggression is a common crayfish social behaviour which establishes a dominance hierarchy, with more dominant individuals gaining better access to shelter, food and mating partners (6).

The Mount Glorious spiny crayfish is a particularly vulnerable species due to its extremely restricted range. Localised threats, such as bush fires, poor forest management practices, habitat destruction and over-exploitation by collectors are all known to negatively impact this species’ population. Additionally, introduced species such as the cane toad (Bufo marinus), as well as cats, foxes, pigs and goats, have all been found to affect crayfish populations (1) (2).

Climate change is also likely to pose a major threat to the Mount Glorious spiny crayfish (1) (2) (7), with increasing temperatures, decreased rainfall, which will alter hydrological regimes, severe weather events and loss of suitable highland habitat all likely to impact heavily on this threatened freshwater crayfish. This species has a limited thermal tolerance and, consequently, it is restricted to cool headwater streams in forested catchment areas. Therefore, increasing temperatures are likely to result in further range contraction of this species (1) (2).

The Mount Glorious spiny crayfish may also be confused with several other crayfish in the genus Cherax, and may therefore be accidentally taken by recreational fishers (1) (2).

The range of the Mount Glorious spiny crayfish coincides with Maiala National Park, which may afford this species some level of protection. However, there are currently no specific conservation measures targeted at the Mount Glorious spiny crayfish (1). All species in the Euastacus genus are designated as ‘no take’ species in Queensland under the Fisheries Act 1994, and must be released if captured (1) (2).

There is an urgent requirement to carry out further research on the Mount Glorious spiny crayfish, which will greatly aid any future conservation or management initiatives for the species. Information on its biology, life history, population size, habitat requirements, thermal tolerances and resilience to exotic species are particularly required (2).

Find out more about Australian crayfish:

• The Australian Crayfish Project:
  http://www.aabio.com.au/crayfish.html