Phylum: Echinodermata (Echin-o-derm-ata) spiny skins
The term echinoderm means “spiny skin” and in this phylum there are five major classes: Sea stars, Brittle stars, Feather stars, Sea urchins and Sea cucumbers.
Rarely would a dive pass without a diver encountering some form of echinoderm on the bottom. Many species are brightly coloured, moderately sized, simple to recognise and some have sharp spines (sea urchins).
Neville Coleman at Christmas Island looking at a brightly coloured
Crown of Thorns Acanthaster planci. This Indian Ocean form is considered by some to be another species.
( photo: Jorina van der Westhuizen)
Although this group is extremely varied in their structure, there is one feature by which they are all united. This character is called penta-radial symmetry.
The adult body is divided into separate but similar sections located around a central process. Most have five sections and so being are called pentamorus (meaning five) a design unique in the animal kingdom.
Class: Asteroidea (As-ter-oid-ea) sea stars
As these animals are not fish, it seems rather ridiculous to continue using the outmoded name “starfish” from the annals of ancient history.
Sea stars are very common, from the intertidal zone down to and beyond 100 metres, they inhabit almost every major habitat from coral reef to muddy bottom.
While most species have the typical five arm design, others may have up to 13 arms (crown of thorns). Even normal five-sided sea stars can be found as three-armed, four-armed or six-armed on occasions.
Dimpled Sea Star Tamaria sp. First discovered during the initial fauna survey of Julian Rocks, Byron Bay in 3/1976 it was (at the time) unable to be determined to species by the curator of the Australian Museum when it was donated. It still remains undescribed BUT is now known to be common in Moreton Bay and on the reefs off Mooloolaba, Qld. in depths of around 20 metres. (AST:251)
Australian Museum- Western Australian Museum
Dimpled Sea Star
First discovered during the initial fauna survey of Julian Rocks, Byron Bay in 3/1976 it was (at the time) unable to be determined to species by the curator of the Australian Museum when it was donated. It still remains undescribed BUT is now known to be common in Moreton Bay and on the reefs off Mooloolaba, Qld. in depths of around 20 metres. (AST:251)
All echinoderms have tube feet modified to their way of life. Reef and sand surface-dwelling sea stars have tube feet tipped with suckers which enable them to hold onto reefs during rough seas, transverse over any terrain (even upside down) at a fair pace and catch and hang onto prey. In the case of bivalve prey the suckered arms are used to bring pressure to bear on each side of the bivalve causing it to open enough to allow the sea star’s extruded stomach to dissolve and digest the bivalve animal.
Sub-sand dwelling sea stars (Astropecten) have tube feet that are pointed, especially modified for digging. When disturbed or threatened on the surface of the sand, these sea stars can virtually ‘melt’ below the surface right before the diver’s eyes.
Sub-sand dwelling sea stars swallow small prey whole and may have as many as five bivalves in their mouth at once.
Sea stars as a group are carnivorous, herbivorous, omnivorous and also scavenge; some are cannibalistic. Most species can be identified from a good colour reproduction.
Coleman's Nippled Sea Star
Discovered on a Swain's Reefs Great Barrier Reef Diving expedition in 1983 this unique species was donated to the Australian Museum. Since then it has been studied by Loisette Marsh (now retired) Curator of Marine Invertebrates at the Western Australian Museum
and found to be an undescribed species.
More recent expeditions have found this species present on the reefs off Mooloolaba, Queensland and in Moreton Bay at around 20 to 30 metres. (Australian Museum)
Neville Coleman's Biscuit Star
This species is only known from a single specimen discovered and photographed at Milne Bay, Papua New Guinea in 4/1982. (AST: 338) It grows to 55 mm and was found in 15 metres of water. (Australian Museum)
Dark Sea Star
Originally found at Heron Island, Great Barrier Reef in 11/1974 (AST: 247) it is also known to be present on the ofshore reefs off Mooloolaba, Queensland(1/1997)
The species remains undescribed. ( Western Australian Museum)
Neville's Sea Star
The only specimen ever found in over 30 years of searching at its type locality at Loloata Island, Papua New Guinea, this unique little sea star (AST: 387) was discovered and photographed in only
2 metres of water. (Western Australian Museum)
Class: Holothuroidea (Holo-thur-oid-ea) sea cucumbers
The majority of holothurians are shaped like cucumbers or sausages and, although some (when alive) feel firm to the touch, their bodies are comprised of soft tissue which is somewhat supported by the presence of minute spicules of calcium carbonate embedded in the body walls. These spicules are used by taxonomists to separate one species from another, as each species has a suite of characteristic patterns. Defensive Cuvierian organs are ejected from the anus of some species.
Sea cucumbers may have tube feet either covering their entire bodies, or in rows along their underneath side to aid in locomotion or attachment, or have entirely naked or smooth bodies. While other echinoderms have a radial symmetry, holothurians have bilateral symmetry with a distinct dorsal and ventral side.
Traditional identification is by microscopic study of the various shaped spicules in each sea cucumber’s body walls. However, once a good colour photograph (or series) showing the animal in its habitat is available for comparison, field identification for many species is achievable to an experienced eye.
Loloata Sea Cumber
Discovered at Loloata Island, PNG in April 2003 in 20 metres of water this undescribed species of Sea Cucumber Thelenota sp. is also now known from the Philippines.
( photo: Neville Coleman) (Victorian Museum)
Coleman's Sea Cucumber
First noticed, photographed and collected from 22 metres of water at Malabar, Lord Howe Island in 12/1979 this was deposited at the Australian Museum but at the time was not recognised as new by the then curator. (HOLO: 185)
Since then, juvenile specimens have been found and photographed (HOLO: 225) and have since been recognised as a New species of Sea Cucumber ( Stichopus sp.) by Holothurian taxonomists at the Victorian Museum. However, as none of the resident divers on Lord Howe Island
could find another adult specimen, it has not been described.
This species grows to 250 mm is now known to be found in other regions.
( Australian Museum)
MORE SPECIES BEING ADDED AT REGULAR INTERVALS
Last updated July 2009