Loricifera Meiofaunal Marine Animals
Brush-heads Inhabit Seaside Sand and Gravel
Only twenty or so species of ‘Brush-head’ have been named so far, although many more have been collected and await description. Reinhart Kristensen first found these small animals in 1983 while studying marine sand in Roscoff, France. They are one of the most recently discovered animal phyla.
Biology of the Loricifera
All members of this phylum Loricifera live in the marine sediments of shallow coastal waters. They are less than one millimeter long, and spend their lives attached to grains of sand or gravel. The scientific name of this phylum means ‘corset wearers’, as their small body is enclosed in a tough casing made of six tiny plates.
- At the head end they have nine rings of spines, giving them the common name of ‘Brush-heads’ – look at the image of Pliciloricus enigmatus below.
- Although very small they have complex internal anatomy, including quite a well-developed brain and a digestive system – they are ‘proper’ little animals.
Many animals can be found living in sand, large ones and smaller ones, but those which can pass through a 0.5 mm sieve (but not a 0.05 mm one) are known as ‘meiofauna’ (or read: 'Higgins, R.P., Thiel, H. (1988). Introduction to the study of meiofauna. Smithsonian Institution Press.'). Most animal phyla have representatives here, 20 out of more than 30.
- Five animal phyla are exclusively meiofaunal; the Jaw Worms (Gnathostomulida), the Mud Dragons (Kinorhyncha), the Water Bears (Tardigrada), the Gastrotricha (which have no common name), and of course the Brush-heads (Loricifera).
- These meiofaunal animals all creep around in the spaces between grains (which to them would seem like boulders!) and either graze micro-organisms that live on the rock surface or hunt one-another.
- Anyone with a low-powered microscope or good hand lens can find them, and many will be new to science – there seem to be thousands of creatures here, many undescribed. This is a good hunting-ground for amateur zoologists.
Meiofauna as Pollution Monitors
It has been suggested that these animals (abundant between grains of sand in any aquatic environment) might be very useful in assessing levels of pollution, in much the same way as small invertebrates can be used to give an measure of the ‘health’ of fresh water.
Evolution of the Loricera
As with the Placozoa it is difficult to decide what the closest relatives of the brush-heads might be. In this case there is much more bodily structure to go on, and their anatomy suggests that they might be related to the Mud Dragons (Kinorhyncha).
Unfortunately only one study has so far been carried out on the molecular biology of the brush-heads (by Park, Rho, Kristensen, Kim, and Giribet - Zoological Sciience - November 2006), and this concludes that ‘a relationship of loriciferans to any particular … phylum was not found in the data’. So we are still waiting for clarification.
Pliciloricus enigmatus
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