Asked by harrison123 to Daniela, Hannah, Ian, Jono, Mark on 19 Jun 2013.
    • Photo: Jono Bone

      Jono Bone answered on 19 Jun 2013:

      Hi harrison123,

      The smallest animal is one of my favourites!

      Although a lot of people will say its an amoeba this is not true because even though amoebas are “animal like” they are only single cells. Animals have to be mulicellular.

      The smallest animals are Tardigrades, also known as water bears.
      Here is a picture of one:

      They range in size from 0.5 mm to less than 0.1 mm in length. Newly hatched larvae may be 0.05 mm in size. Tardigrades are really cool because they can survive extremes of temperature and pressure that would kill almost any other animal, ranging from the vacuum of space near absolute zero, to 151 degrees Celcius and pressures of the deepest sea trench. They can survive about 1000 times more radiation than other animals, and due to their extreme hardiness are encountered from the tops of the Himalayas to the depths of the oceans and from the Arctic to the jungle.

    • Photo: Mark Hodson

      Mark Hodson answered on 19 Jun 2013:

      Hi Harrison,

      apparently there is also a small parasitic wasp living in Guadelope that clocks in at 0.1 mm


      Then there are some things called myozoans 10 – 20 microns in size (there are a thousand microns in a millimetre) which I think beats Jono’s water bears. Apparently even though they are so small they contain several cells.

      There’s a picture here under the family tree of these things. They aren’t as cute as water bears!




    • Photo: Ian Wilson

      Ian Wilson answered on 19 Jun 2013:

      Hi harrison123,

      I agree with Mark on this one – myxozoa are technically animals but they’re so small that they were once thought to be microbes!

      There’s a section of DNA in a lot of organisms called “ribosomal rDNA” and different groups of organisms tend to have very similar copies of these sequences. This means that newly-discovered creatures can be categorised by matching them with others with similar sequences. That’s how scientists knew that the myxozoa were animals, not bacteria.

      Myxozoa are parasites and infect fish and types of worms. So they’re not quite a cute and cuddly as tardigrades either!



    • Photo: Hannah Brotherton

      Hannah Brotherton answered on 20 Jun 2013:

      Hi harrison123,
      So you can small animals which are microscopic like jono has shown, but the smallest animal that you and me think of as animals (like a dog or a cat) is the pygmy marmoset monkey, its called a pocket money……….I want one!


    • Photo: Daniela Plana

      Daniela Plana answered on 20 Jun 2013:

      Hi harrison123!

      I’m loving all your questions… and learning loads from everyone elseĀ“s answers! Love the tiny marmoset from Hannah! Was reminded that a few years ago, the smallest frog was found in South America, thought you might like to see it…