Seastars (or starfish) are a distinctive group of invertebrate animals, often encountered intertidally and by divers. They are readily recognized by their stellate (star) shaped profiles with five or more tapering arms radiating from the central body, although some species have a more cushion-like pentagonal shape with arms reduced.
Seastars are also ecologically and commercially significant, as shown by the examples of the impact of the Crown-of-Thorns Starfish (Acanthaster planci) on the Great Barrier Reef, and the introduction of the Northern Pacific Seastar (Asterias amurensis) to parts of Australia.
They are classified with sea cucumbers, sea urchins, feather stars, brittle stars, basket stars and sea daisies in the phylum Echinodermata (from the Greek words for spiny skin). Characteristics these animals share include their basic body symmetry, an internal calcareous skeleton and a water vascular system composed of fluid filled canals that are often evident as external tube feet which are used for locomotion. However, body shape and other features separate seastars into the class Asteroidea. Brittle stars and basket stars (class Ophiuroidea) are similar but typically have a circular central body from which the arms are more strongly demarcated.
General information regarding seastars can be found at many internet websites, including the Californian Academy of Sciences Echinoderm Webpage, the University of California at Berkeley Introduction to Echinodermata site and the World Asteroidea database.
Specialist information on Australian seastars is available at the Australian Biological Resources Study Faunal Directory and there a number of regional guides providing information on southern Australian species and Indo-Pacific species. However, up-to-date information on the seastars occurring in the Sydney area, the most populated and one of the most highly visited parts of Australia, is scattered. Therefore, enquiries which are often received at the Australian Museum are sometimes difficult to answer easily.
This project aims to improve this situation by providing tools to aid in the identification of seastar species likely to be encountered in the Sydney region (defined here as between Gosford to the north and Bundeena to the south) in depths to 30 metres. The Australian Museum collection registration database was used to generate the initial list of species, specimens from the collection were also used to provide images and these were supplemented with field collections to obtain photographs of living animals. These web pages are still under development. It is hoped in the future a more comprehensive guide will be provided with identification keys, images of live specimens of all species and other information.
To see an image gallery of most Sydney seastar species click here. Information about each of these species can be obtained by clicking on the individual images and then selecting the related items. Alternatively, a list of species is provided below which links to additional information and images for each species.
Echinaster colemani Nardoa novaecaledoniae
These pages should be cited as: Keable, S.J., Springthorpe, R.T., Attwood, K.B., Murray, A. Stoddart, H. E. and Hegedus, A.D. 2015 onwards. Seastars/starfish (Echinodermata: Asteroidea) of the Sydney region. australianmuseum.net.au/sydney-seastars.
For further details contact Dr Stephen Keable firstname.lastname@example.org