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Multiple births
THE LAST WORD Thingies While swimming one morning across Coogee Bay in New South Wales, Australia, we came across thousands of these strange creatures (see photo) floating at depths down to about 2 metres. They were hard but also flexible, with water inside and a small hole at one end. Their length varied from about 3 to 30 centimetres and their walls were between 2 and 5 millimetres thick. Their skin was marked with many small protrusions, the size of which varied from one creature to another. Unlike jellyfish they appeared to be completely harmless. No one I’ve spoken to from the area has ever come across anything like this. So what were they and why were they there?
n The tubular object is a pyrosoma. These are colonial tunicates, related to sea squirts, salps and doliolids. Each tube, or tunic, is a leathery gelatinous
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is generally believed to warn matrix that contains a number of poor food supply or of the of individual tunicates, or zooids. presence of predators. One end of the tube is blocked Pyrosomas are entirely and the other open but guarded harmless and occur in swarms by a controllable diaphragm. The inner surface of the tube “Each pyrosoma is made up is very smooth. In contrast, the of numbers of individuals tube’s outer surface is rough buried in a common, because each zooid projects tubular, gelatinous matrix” out of it to feed. Each zooid is a filter feeder, in productive areas of the world’s pumping seawater by ciliary oceans. As with jellyfish, swarms action from outside the tube and sometimes drift into coastal passing it through a pharyngeal shallow water. They have another branchial “basket”, or gill, where planktonic food items and oxygen common feature with jellyfish: are extracted. The seawater is then pyrosomas are 94 per cent water so represent a low-value diet. expelled to the interior of the tube, before leaving via the tube’s However, their best-known predator, the leatherback turtle open end. When all of the zooids (Dermochelys coriacea), still eats in the tube are pumping water enormous quantities, probably into the interior the pyrosoma hunting them at night. moves by jet propulsion. John Davenport Pyrosomas vary a great deal in Professor of Zoology length, from a few millimetres University College Cork, Ireland to 30 metres. They undertake vertical migrations, tending to n I had put this question to the be at the surface at night and at back of my mind until I started depth during the day. The name pyrosoma translates researching gelatinous zooplankton for a lecture I am as “fiery body” and the colonies preparing. This generated a show intense, sustained eureka moment. bioluminescence when I think the creature in the stimulated mechanically or by photo is the thaliacean Pyrosoma light. Each zooid has two light atlanticum. At first glance it organs that contain luminescent looks like a sea cucumber, or bacteria. A lit-up colony can be holothurian, but the fact that seen from up to 100 metres away in clear waters in the middle many specimens were found in the water column, and your hint of the night. that the body is gelatinous (hard Bioluminescent light from one but flexible) gave me doubts. colony will stimulate another to Despite having a similar flash. Light output is always gelatinous constitution, preceded by the cessation of ciliary pumping, so the lightshow thaliaceans are not directly
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related to jellyfish, which explains why they do not contain cnidocytes – the stinging cells that provide the nasty sting experienced from some jellyfish species. P. atlanticum is a colonial species made up of zooids gelled together in a gelatinous tunic, which gives them a “bumpy” appearance. They can be pink, as shown, and have one hole at the end of the tube. They are often found in swarms, as the questioner describes. These swarms sink rapidly when dead and have been found to accumulate in patches on the deep-sea floor creating an important source of fresh organic carbon for deep-sea animals. Tania FitzGeorge-Balfour Queen Mary University, London
This week’s questions Multiple births
How is it that birds which lay a large number of eggs are able to have them all hatch on approximately the same day? Patrick Casement London, UK Cool bugs
We keep foodstuffs in the fridge to reduce bacterial spoilage but are there any bacteria that thrive best at fridge temperatures? Are some foodstuffs more likely to spoil in the fridge rather than out of it because they carry such bacteria? Peter Hunt Teignmouth, Devon, UK
n The tubular object is a pyrosoma. These are colonial tunicates, related to sea squirts, salps and doliolids. Each tube, or tunic, is a leathery gelatinous
Questions and answers should be concise. We reserve the right to edit items for clarity and style. Include a daytime telephone number and email address if you have one. Restrict questions to scientific enquiries about everyday phenomena. The writers of published answers will receive a cheque for £25 (or US$ equivalent). Reed Business Information Ltd reserves all rights to reuse question and answer material submitted by readers in any medium or format.
Last words past and present, plus questions, at www.last-word.com
is generally believed to warn matrix that contains a number of poor food supply or of the of individual tunicates, or zooids. presence of predators. One end of the tube is blocked Pyrosomas are entirely and the other open but guarded harmless and occur in swarms by a controllable diaphragm. The inner surface of the tube “Each pyrosoma is made up is very smooth. In contrast, the of numbers of individuals tube’s outer surface is rough buried in a common, because each zooid projects tubular, gelatinous matrix” out of it to feed. Each zooid is a filter feeder, in productive areas of the world’s pumping seawater by ciliary oceans. As with jellyfish, swarms action from outside the tube and sometimes drift into coastal passing it through a pharyngeal shallow water. They have another branchial “basket”, or gill, where planktonic food items and oxygen common feature with jellyfish: are extracted. The seawater is then pyrosomas are 94 per cent water so represent a low-value diet. expelled to the interior of the tube, before leaving via the tube’s However, their best-known predator, the leatherback turtle open end. When all of the zooids (Dermochelys coriacea), still eats in the tube are pumping water enormous quantities, probably into the interior the pyrosoma hunting them at night. moves by jet propulsion. John Davenport Pyrosomas vary a great deal in Professor of Zoology length, from a few millimetres University College Cork, Ireland to 30 metres. They undertake vertical migrations, tending to n I had put this question to the be at the surface at night and at back of my mind until I started depth during the day. The name pyrosoma translates researching gelatinous zooplankton for a lecture I am as “fiery body” and the colonies preparing. This generated a show intense, sustained eureka moment. bioluminescence when I think the creature in the stimulated mechanically or by photo is the thaliacean Pyrosoma light. Each zooid has two light atlanticum. At first glance it organs that contain luminescent looks like a sea cucumber, or bacteria. A lit-up colony can be holothurian, but the fact that seen from up to 100 metres away in clear waters in the middle many specimens were found in the water column, and your hint of the night. that the body is gelatinous (hard Bioluminescent light from one but flexible) gave me doubts. colony will stimulate another to Despite having a similar flash. Light output is always gelatinous constitution, preceded by the cessation of ciliary pumping, so the lightshow thaliaceans are not directly
New Scientist retains total editorial control over the content of The Last Word. Send questions and answers to The Last Word, New Scientist, Lacon House, 84 Theobald’s Road, London WC1X 8NS, UK, by email to [email protected] or visit www.last-word.com (please include a postal address in order to receive payment for answers). For a list of all unanswered questions send an SAE to LWQlist at the above address.
Do Polar Bears Get Lonely? Our latest collection serious enquiry, brilliant insight and the hilariously unexpected Available from booksellers and at www.newscientist.com/ polarbears
related to jellyfish, which explains why they do not contain cnidocytes – the stinging cells that provide the nasty sting experienced from some jellyfish species. P. atlanticum is a colonial species made up of zooids gelled together in a gelatinous tunic, which gives them a “bumpy” appearance. They can be pink, as shown, and have one hole at the end of the tube. They are often found in swarms, as the questioner describes. These swarms sink rapidly when dead and have been found to accumulate in patches on the deep-sea floor creating an important source of fresh organic carbon for deep-sea animals. Tania FitzGeorge-Balfour Queen Mary University, London
This week’s questions Multiple births
How is it that birds which lay a large number of eggs are able to have them all hatch on approximately the same day? Patrick Casement London, UK Cool bugs
We keep foodstuffs in the fridge to reduce bacterial spoilage but are there any bacteria that thrive best at fridge temperatures? Are some foodstuffs more likely to spoil in the fridge rather than out of it because they carry such bacteria? Peter Hunt Teignmouth, Devon, UK