Any idea what a pyrosome is?

If you caught this blog from National Geographic or this Instagram post from CSIRO, you would have learnt that during a voyage in March 2019, scientists on CSIRO's research ship RV Investigator encountered a large swarm of bioluminescent pyrosomes, and sampled some to study. You would also have learnt that pyrosomes are weird. You probably would not, however, have learnt what pyrosomes actually are.


This is where Taxonomy Australia can help. We go behind the news to give background and context on biodiversity news stories and the creatures in them.


One of the pyrosomes collected by scientists on board the RV Investigator in March 2019. Source: https://www.instagram.com/p/Bx6_Nv2FKZ5/

Pyrosomes are colonial, free-floating tunicates in the genus Pyrosoma. Tunicates may be more familiar to people who live around the coast of Australia in the form of sea-squirts, rather odd, blob-like animals that live attached to rocks and at low tide will contract and squirt water all over you if poked.


Tunicates are remarkable because they belong in the phylum Chordata, along with fish, mammals, and of course us. Tunicates, whether pyrosomes or sea-squirts, don't look much like us when they're adults, but their larvae are tadpole-like and have a primitive notochord (in vertebrates the notochord is the spinal column; in larval tunicates it's a cartilaginous rod running along the back that supports the body and protects the large nerve that's equivalent to our spinal cord). In fact, vertebrates may be simply neotenous tunicates - sea squirts that became sexually mature as larvae and eventually conquered the world.


You can read more about tunicates, including pyrosomes, on the Taxonomy Australia website.

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