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Waxed out

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Page 1: Waxed out

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.

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For a list of all unanswered questions send an SAE to LWQlist at the above address.

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Do Polar Bears Get Lonely?

THE LAST WORD

Life on UluruSome decades ago I was travelling around Australia and was lucky enough to climb Uluru. Pools on top of the rock had been produced by recent rain and, curiously, in many of them strange aquatic invertebrates were present (see photo). This specimen is sitting in my camera lens cap, which has a diameter of 62 millimetres. It looks like an ancient trilobite. Why and how was it on top of the famous, massive rock, and what is it? What happens to the creatures when the short-lived puddles dry up?

n The animal pictured is a shield shrimp, Triops australiensis. They are crustaceans in the class Branchiopoda – meaning “gill-legged” – and this term reflects the fact that they use their legs for breathing as well as for motility.

Their external morphology appears to have remained unchanged for 220 million years or more, and one species, Triops cancriformis, has been claimed by some to be the oldest extant animal species. They occur in bodies of fresh or slightly salty water that periodically dry out, such as ephemeral lakes, farm dams, ditches and even puddles left after rain.

The eggs of these animals have a very strong shell and are resistant to drying out. In some species, a period of desiccation is actually necessary for the creature’s development. The eggs can tolerate freezing and temperatures up to 80 ̊ C, and

may remain viable for 25 years. In some species, hatching may take up to a year following exposure to suitable conditions, but in T. australiensis it usually takes several weeks at most. Once hatched, development from egg to adult may take only a further few weeks in summer temperatures. The animals have a lifespan of up to three months, and adults reach about 35 millimetres in length.

The shrimps feed on microscopic organisms, aquatic worms, other shrimp species, frogs’ eggs and larvae, decomposing vegetation and other detritus, and sometimes even moulting individuals of their own species. The small size and the robustness of the eggs allow them to be carried on the wind for hundreds of kilometres from

their pools of origin, and it is probably this mode of transport that would have delivered the eggs to the top of Uluru.

It is also possible that the eggs might have been carried up in mud caked on a visitor’s boots. Although in this instance such a method of transport is essentially innocuous, it is nevertheless a salient reminder of the need to ensure that all clothing and equipment is cleaned before moving from one ecosystem to another.Harko WerkmanWoodbridge, Tasmania, Australia

n I bought a packet of desiccated shield shrimp eggs (Triops australiensis) on the internet for my boyfriend’s 30th birthday. As the species name suggests, shield shrimps have three eyes: two compound eyes and one naupliar eye – a simple median eye, first appearing in the larval stage. They closely resemble their Triassic ancestors, which existed around 220 million years ago.

Blown around with the red dust, eggs eventually settle in crevices and grooves – even on the top of the great rock – where they may remain viable for up to 10 years. I guess that means my boyfriend has an excuse for not hatching them yet.Kate HutsonSchool of Earth and Environmental SciencesUniversity of Adelaide, Australia

n Triops species are found on most continents but are rare in the UK, where the tadpole shrimp

(Triops cancriformis) is currently known to exist in only two locations, the New Forest and the Solway Firth. Visitors to the Wildfowl and Wetlands Trust Centre at Caerlaverock, Dumfriesshire, can view this species in the visitor centre.

Triops is typical of ephemeral,

or temporary, wetlands, and can survive drying to persist for up to 30 years as eggs or cysts. The eggs at Caerlaverock were collected to provide a safety net for the population in Scotland, where they persist in one temporary pond which has been created by cattle trampling around a fence post. Emma Hutchins, Head of Reserves Management Sally Cordwell, Head of Public RelationsWildfowl and Wetlands TrustSlimbridge, Gloucestershire

This week’s questionsEAr whAcksWhy does having something pushed into my ear make me cough?Oliver PilkingtonIlkley, West Yorkshire, UK

wAxEd oUTWhat is earwax for?Ady AmblerLondon, UK

“Triops has three eyes and closely resembles its Triassic ancestors from 220 million years ago”

Last words past and present, plus questions, at www.last-word.com

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