Anaspides tasmaniae

Anaspides tasmaniae is a species of freshwater crustacean found in Tasmania.^[2] Members of the genus Anaspides are commonly known as Tasmanian mountain shrimp.^[3] Mountain shrimp are often referred to as “living fossils”^[3][4][5][6] since they have remained morphologically largely unchanged for over 200 million years.^[3][5][4]

Anaspides tasmaniae was described by George Malcolm Thomson in 1894^[2] on the basis of specimens collected from the summit of Mount Wellington, Tasmania. Thomson suggested a new genus (Anaspides) and a new family (Anaspidea) due to the animal’s unique characteristics. The name Anaspides refers to the total absence of a carapace and is derived from the Ancient Greek ἀν (“an” - lacking) and ἀσπίς (“aspis” - shield).

Anaspides tasmaniae is the type species for the genus,^[3] which now includes eight species of mountain shrimp.^[4][7]

Despite the common name, mountain shrimp are not true shrimp as they are not members of the order Decapoda. Recent molecular data place them as a sister group to the Euphausiacea (krill).^[8][9]

Anaspides tasmaniae can reach up to 35mm in length from the tip of the rostrum to the end of the telson.^[3] Its colour varies from light to medium brown.^[5] This species can be distinguished from similar species in the genus by the combination of the following features: eyes with a well-developed cornea,^[3] an elongated telson with an evenly rounded posterior margin, the form of the antennular inner flagellum and, in males, the presence of two antennular clasping spines.^[5]

Anaspides tasmaniae was previously thought to occur across Tasmania^[5][10] but recent studies indicate that its distribution is limited to creeks, runnels and pools in just two areas: on the east and south-east sides of kunanyi/Mount Wellington up to 970m above sea level^[5] as well as in and near Mount Field National Park.^[11] It is mainly known from surface habitats; unlike some other members of Anaspides, the species is rarely found to live in underground cave environments.^[10] The species has not been recorded on Mount Wellington Plateau (above 970m) in recent decades, likely due to changes in the habitat following major bushfires in the 1930s.^[5]

Like all members of Anaspides, Anaspides tasmaniae is restricted to a narrow range of temperatures.^[11] Its current known altitude range is 320m to 970m above sea level.^[5] Its distribution is strongly influenced by Pleistocene glaciations which formed the alpine habitats where it occurs today.^[11] The two regions where the species persists are post glacial relicts, indicating that the species inhabited a wider range during glacial periods.^[11]

Anaspides tasmaniae is not currently included on state or federal lists of threatened fauna.^[12][13] The species is considered to be vulnerable in light of new data on its limited geographic range.^[5] Scientists have noted the need for reassessment of its conservation status.^[3][5]

In 1907 zoologist Geoffrey Watkins Smith arrived in Tasmania to study the island’s freshwater crustaceans.^[14] In his 1909 book “A Naturalist in Tasmania”^[15] he describes his first encounter with Anaspides tasmaniae:

Goethe somewhere remarks that the most insignificant natural object is, as it were, a window through which we can look into infinity. And certainly when I first saw the Mountain Shrimp walking quietly about in its crystal-clear habitations, as if nothing of any great consequence had happened since its ancestors walked in a sea peopled with strange reptiles, by a shore on which none but cold-blooded creatures plashed among the rank forests of fern-like trees, before ever bird flew or youngling was suckled with milk, time for me was annihilated and the imposing kingdom of man shrunk indeed to a little measure.