28 August 2013

12 new solitary ascidians records for Singapore

Thanks to Serina Siew-Chen Lee, we can learn more about 16 species of solitary ascidians found in Singapore, with 12 new records!
The pretty striped 'Thumbs up' sea squirt is common in Singapore.
Ascidians are intriguing creatures. They are actually closely related to vertebrates like us. We belong to same Phylum Chordata as they do!

As ascidians are closely related to vertebrates, studying them helps us humans! This recent article in ABC News reports ascidians are believed to have been among "the first invertebrates to have a vasculature heart system, similar to that in humans, with blood cells traveling through blood vessels. But astonishingly, it can regrow everything just with its blood vessels. Scientists have just sequenced the genome of an ascidian: Botryllus schlosseri. Once scientists understand how these genes operate, they will be able to come up with new treatments for a wide range of human diseases."
There are about 3,000 known species of ascidians. These range from tiny ones 1mm long, to those more than 10cm. Most are found in shallow waters but some species are found in very deep waters.
Unidentified sea squirt
Although it looks like a blob, an ascidian is a complex animal. It usually has a circulatory system, a digestive system, a heart and other organs. The entire animal is encased in a little bag. 'Askidion' comes from the Greek word for 'bladder' or 'little bag'. Some ascidians have a sturdy outer coat called the tunic. Thus, they are sometimes called tunicates.
Unidentified sea squirt embedded in hard coral
This solitary ascidian is growing inside a hard coral,
with only its siphons showing.
Some solitary ascidians have bands of muscles along their body. When these muscles contract, water squirts out of the animal. So they are sometimes also called sea squirts.
Unidentified sea squirt
Ascidians are awesome and it's wonderful to learn more about Singapore's ascidians. Thank you Serina!

Abstract
Sixteen species of solitary ascidians were identified from subtidal marine fouling communities present on navigational buoys, jetty pilings, floating pontoons and nettings around the coastal waters of Singapore. Of these, twelve are new records: Ascidia gemmata, Phallusia arabica, Phallusia nigra, Rhodosoma turcicum, Rhopalaea crassa, Polycarpa argentata, Polycarpa aurita, Polycarpa captiosa, Polycarpa olitoria?, Styela canopus, Pyura curvigona and Herdmania pallida. The other four species include Ascidia sydneiensis, Phallusia philippinensis, Polycarpa papillata and Microcosmus exasperatus. A detailed morphological comparison of Phallusia nigra and P. philippinensis is included because these two species have been frequently confused, resulting in a significant under-reporting of the latter in the literature.

Read more in Serina Siew-Chen Lee, Serena Lay-Ming Teo and Gretchen Lamberta, New records of solitary ascidians on artificial structures in Singapore waters, Marine Biodiversity Records, Volume 6, 2013, e93 (18 pages) DOI: http://dx.doi.org/10.1017/S1755267213000638 Published online: 06 August 2013

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