Phylum Arthropoda
Subphylum Crustacea
Class Malacostraca
Order Spelaeogriphacea
Common names: spelaeogriphaceans, cave shrimps
Overview
Spelaeogriphacea, or cave shrimps, are a very small, rare group of crustaceans found only in subterranean waters. Spelaeogriphaceans have long, cylinder-shaped bodies and most closely resemble decapod prawns, however their short, shield-like carapace only covers the back of the head and first two thoracic segments. The head has a distinct, beaklike projection (rostrum). The antennules are flagelliform (long), biramous (branched) and possess three segmented peduncles. Antennae are also flagelliform with three segmented peduncles but are uniramous (unbranched). An optic lobe (eyestalk) is present, but due to their troglobitic lifestyle their eyes are non-functional or absent, i.e. they are blind. They have one pair of uniramous maxillipeds (thoracic limbs that work with the mouthparts). The thoracic legs (pereopods) are used for walking and to move oxygen-carrying water past the body are biramous, with the exopods on pereopods 1-3 elongate and setose (hairy); pereopods 4�7 gill-like. The first four pairs of abdominal limbs (pleopods) are biramous and leaf-like, while the fifth pair is greatly reduced in size. The posterior pair of appendages (uropods) are long and setose, and in between is a slender tail (telson) (not fused to pleon). The telson and uropods do not join together to form a fan-like tail. Like the similarly subterranean, blind thermosbaenaceans, spelaeogriphaceans are unpigmented (colourless and typically transparent and range from around 3�10 mm in length.
Distribution and diversity
Spelaeogriphaceans are among the rarest crustaceans. There are currently only four known species (all endemics) in three genera: Spelaeogriphus lepidops recorded from a cave stream on Table Mountain in South Africa; Potiicoara brasiliensis from a cave pool in Brazil; and Mangkurtu mityula and M. kutjarra from individual aquifers in the Pilbara region of north-western Australia.
Life cycle
Males and females are known. The females carry ten to twelve eggs in the brood pouch located under the thorax between the thoracic legs and surrounded by the carapace, similar to that found in isopods. Observations of animals in captivity suggest that they hatch with the full number of thoracic segments and development into the adult stage is via several moults.
Feeding
Spelaeogriphaceans are considered to be detritivorous, however detailed knowledge of their feeding is not known. Similar to thermosbaenaceans, they are thought to use their mouthparts to sweep up small bits of plants and other materials off rocks that are washed into the caves and underground springs.
Ecology
Little is known about the ecology of spelaeogriphaceans with most of the knowledge coming from the South African species, S. lepidops. Spelaeogriphaceans occur only in continental fresh or slightly brackish water in streams or pools (running or still water) in limestone or sandstone caves, or in calcrete aquifers. They do not burrow or swim but walk around on the bottom their habitats. Because of their distribution, rarity and geological age, spelaeogriphaceans (like thermosbaenaceans) are of particular interest to scientists studying endemic species and evolution of crustaceans.
Mangkurtu mityula
Image credit: Photographer: D. Elford
� Western Australian Museum
