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Seaweek 2011: Spotlight on Marine Science

Have you heard about Sea spiders?

By Dr. Claudia Arango
Biodiversity Program, Queensland Museum, South Brisbane

We have more than 200 hundred species of sea spiders in Australia but for most people they simply do not exist, they can’t be true spiders! They are not, they are a very different group of arthropods which might be only distant relatives to terrestrial spiders. Sea spiders or pycnogonids are in the group Pycnogonida that seems to have been present on earth since Cambrian times, which is about 500 million years!

Sea spiders can be found in every marine habitat, we can find them under rocks and in crevices in shallow waters and coral reefs, these are usually tiny so Queenslanders do not get to see possibly any of the 65 species and possibly more that occur in warm Australian waters.

They seem to have diversified more in cold waters, the deeper and more south we sample, the more species we found. There are near 1,500 species in the world, and 20% of them are found in the Southern Ocean, that is Antarctica and surrounding waters, and they also get bigger. At least in some families, species in warm waters are tiny midgets of 5 mm, while their relatives from Antarctica can have 20 cm in leg span!

The good thing is that we do not have to go to the pole to find beautiful sea spiders visible to a naked eye. The coast of New South Wales mostly towards the South, and also diving spots in Victoria and Tasmania are ideal to find amazingly colourful sea spiders that range from 2 to 5 cm. They can be mostly seen on whitish, purple or brown bryozoans (these are sessile, colonial animals that look like plants, this the common name ‘moss-animals’).

Other slender species can be found under rocks or hiding amongst the substrate, in an incredible display of perfect camouflage. They are rare and they hide, but you might be able to spot one in your next dive, and if you have a macro lens, there is chance of great shots!

Sea spiders either walk along the bottom with their stilt-like legs or swim just above it using an umbrella pulsing motion.[Most are carnivores or scavengers and feed on cnidarians, sponges, polychaetes and bryozoans. They will often insert their proboscis, a long appendage used for digestion and sucking food into its gut, into a sea anemone and suck out nourishment. (from Wikipedia) .

Find more on Australian sea spiders at:

and check great photos of sea spiders from New South Wales at :

Seaweek 2011 - What's on the site?
Teaching Ideas

Sea spider (Pseudopallene) on bryozoan

Deep sea Sea spider
This 20 cm long specimen is a deep sea species, capable
of living at depths below 1,000 meters. This image forms
part of the monthly 'Curators Choice' series from Rhagor,
the collections based website from Amgueddfa Cymru
- National Museum Wales.




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