November 2018

Neptune’s sword

Neptune’s Sword (photo: Elsa Chang and Leo Lee)

What is this beautiful gelatinous tube? Creature or colony?

Answer

Neptune’s Sword (photo: Elsa Chang and Leo Lee)

This amazing creature is actually a colony of animals. It is called a Pyrosome, and is made up of individuals known as tunicates. Pyrosomes, or  purse salps, are found in open seas in both temperate and tropical waters. This pyrosome, called Neptune’s Sword (Pyrostremma spinosum) has been recorded to reach a colossal 30 metres in length. Many of the common Salps are much smaller, some less than a centimetre, and vary greatly in shape. Salps are an unusual group of marine animals that float freely in the currents, filtering as they move through the water to feed on plankton. The Salps are fast growing and live initially as solitary asexual forms. They then aggregate to form long chains of sexually active well organised clusters that can reach impressive lengths, appearing as semi-transparent hollow tubes that are sealed at one end. They were described by one diver as being ‘as delicate as a feather boa’. And adding to their mystery and allure, they can even glow in the dark. Though the salps look like jellyfish they are part of the Phylum Chordata, that group of animals that share a dorsal nerve chord. They do not have a backbone, but the group include all of the vertebrates or backboned animals such as mammals and birds. Salps belong in the same subphylum, Tunicata, as do the sea squirts. Fish, turtles and birds find the salps to be a tasty bite. What would you do if you came across Neptune’s Sword?  

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