A British species of Shovelhead worm (Magelona johnstoni). Image: Andy Mackie.

A Portuguese species of Shovelhead worm (Magelona lusitanica)

Head end of Magelona montera from the Red Sea, stained with methyl green. Image: James Turner

Magelona obockensis

from the Gulf of Aden

Head end of Magelona sinbadi from the Persian Gulf, stained with methyl green. Image: James Turner

An example of a magelonid pouch

Marine bristle-worms (Polychaetes) are related to earthworms and leeches - well known examples are lugworms and ragworms used by sea fisherman as bait. The Magelonidae is a small family of polychaetes that have a unique flattened head, used for digging, giving them the common name, the shovelhead worms. There are over 70 species of shovelhead worms, 11 of which were first described by marine biologists from Amgueddfa Cymru.

Polychaetes are found in nearly every marine habitat and often make up a large proportion of the animals living in and on the seabed. There may be 9000 species worldwide, although estimates vary widely and new species are being discovered constantly (even in British waters).

Polychaetes can vary hugely in their form and size, how mobile they are, and how they obtain their food.

What are Shovelhead Worms (Polychaeta: Magelonidae)?

The Magelonidae is a small family of polychaetes, found all over the world. They burrow in muds and sands, and are generally found at water depths of less than 100 m. They are slender, beautiful worms, usually less than 10 cm long. They have a unique flattened head, used for digging in sediments, giving the group its common name, the shovelhead worms. The have two long feeding tentacles (palps) that are adorned with small 'bumps' (papillae). Over 70 species are known worldwide, 11 of which were first described by marine biologists from Amgueddfa Cymru, including one British species, Magelona johnstoni Fiege, Licher & Mackie, (2000).

Marine biologists at Amgueddfa Cymru have studied the shovelhead worms in the seas surrounding the Arabian Peninsula and confirmed the presence there of Magelona cornuta, Magelona obockensis, Magelona pulchella, Magelona crenulifrons and an undescribed species from the Red Sea (Mortimer, 2010). This research led to collaboration with scientists from the Spanish Centre d'Estudis Avançats de Blanes (CEAB) who made Magelona specimens available from over 100 locations in the same region.

A worm with horns

The undescribed species highlighted in 2010, was first noticed in the collections of the Muséum National d'Histoire Naturelle in Paris. It is a particularly interesting species as it has uniquely shaped horns on its head, giving it the appearance of wearing a bullfighter's hat! It has now been named Magelona montera, after the Spanish word for a matador's hat (Mortimer et al., 2012).

A further six species of Magelona have now been identified from seas surrounding the Arabian Peninsula, including another new species from Iran named after the fictional sailor, Sinbad (M. sinbadi, M. cf. agoensis, M. conversa, M. cf. falcifera, M. symmetrica, and M. cf. cincta). This raises the total number of species known from the Red Sea/Gulf region to eleven, three of which were originally described from the Seychelles by Museum staff (Mortimer & Mackie, 2003; 2006).

The partnership between Amgueddfa Cymru and CEAB has proven to be successful and also led to a review of the shovelhead worms from Portugal, including the description of a new species, Magelona lusitanica. This work was published in the proceedings of the 10th International Polychaete Conference, held in Italy, June 2010 (Mortimer, Gil & Fiege, 2011). In 2013, Museum staff worked with scientists from the East China Sea Fisheries Research Institute, Shanghai to describe a new species from the Yellow Sea, China (Zhou & Mortimer, 2013).

Amgueddfa Cymru taxonomists have now studied 30% of all known Magelona species. However, it doesn't stop there. Work is now starting on British species as part of the museum's review of the British Polychaete Fauna. We will also investigate the distinctive abdominal pouches present in some magelonid species, whose function remains a mystery.

Part of a rock containing a fossil coral which is only just visible. Most of the fossil is hidden inside the rock.

Small fossils require large machines: the Diamond Light Source synchrotron facility at Didcot, Oxfordshire.

Fossils often need to be carefully prepared before they can be identified by palaeontologists and traditional methods can damage the specimen irreversibly. Scientists at Amgueddfa Cymru are experimenting with new technologies to study ancient fossils in minute detail with no damage to the specimen whatsoever.

The preparation of fossils for identification and study often requires the surrounding rock to be removed. A variety of tools are used for this, including specialist equipment such as pneumatic pens driven by compressed air and air-abrasive machines which work like miniature sandblasters. In some cases the surrounding rock can be dissolved away from the fossil

Destructive techniques

These preparation methods will reveal the surface of a fossil but to identify some specimens we must look inside them. Certain fossil groups are routinely examined using destructive techniques. For example, to study the internal structure of corals, bryozoans and brachiopods, specimens are cut up (sectioned) into slices so thin that we can shine light through them and examine them under a microscope. These slices are known as 'thin sections'.

Sometimes it is not desirable to remove the rock or to cut up the specimen. The fossil may be very delicate and break during preparation. Or, if the fossil is very rare, we would rather not use a destructive technique as it may be difficult or even impossible to replace the fossil.

Non destructive X-Ray tomography

In these instances, it is now possible to use X-rays to build up a virtual three-dimensional image. The technique is called X-ray tomography. As rock is much denser than living tissue, X-ray tomography of fossils requires a more powerful radiation source than a hospital X-ray machine. The Diamond Light Source Synchrotron at Didcot, Oxfordshire is one such facility, the only one in the UK. This machine is in the shape of a giant donut with a diameter of 300 meters. It accelerates charged particles (electrons) through sequences of magnets to almost the speed of light, producing the X-rays.

This method was recently used by Amgueddfa Cymru scientists to investigate a small fossil found in Ordovician rocks 462 million years old in Iran. It was half buried in the rock and appeared to be a solitary rugose coral. The conventional approach to identifying rugose corals – to slice into thin sections – was rejected because of the small size and rarity of the specimen. Instead we took it to Didcot for X-ray tomography.

The new technique worked very well and we managed to obtain spectacular 3D images, and even and virtual thin sections – without any damage to the fossil itself. From these, we determined the internal structure of the fossil and concluded that the specimen was indeed a coral, probably a species of the genus Lambelasma.

It is approximately 5 million years older than the earliest previously described rugose coral, making it a significant addition to our knowledge of early life on our planet.