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The distinguishing characteristic of all annelids is the fact that they are made up of multiple segmented rings. In fact, their name comes from the Greek word for little rings, annelus. 

Candidate: Spirobranchus giganteus

The Annelids, despite only consisting of about 22,000 extant species, show a truly remarkable variation in shape and size. S.giganteus belongs to the class polychaeta, meaning it has several appendages called chaetae on each of its segments. This species is affectionately known as the “Christmas-tree worm” due to the fact that it has two large appendages coming out of its side which spiral up to a point and therefore resemble a christmas tree. The worm is able to build specialised tubes on the surface of corals which they are permanently retreated into. Not only does this Annelid have a beautiful shape, it also can display a variety of different colours depending on the colours of the coral reef in which it is located. I’ve seen bright blues, deep purples, oranges, yellows, reds and even some multi-coloured variants. You might think this makes it significantly more visible to predators, but to combat this they are able to close off their tubes using a modified radiole/chaetum known as the operculum which acts like a door which can be opened and closed

Due to being a sedentary organism, Spirobranchus giganteus  gets its nutrients by filter-feeding. Its upper radioles/chaetae are highly ciliated, meaning that any microorganisms which venture too close to these mouthparts will become trapped and eventually be deposited straight into the Annelid’s digestive tract

Talking about the digestive tract, S.giganteus has a very complex digestive system as well as a fully closed circulatory system. Despite being only around 3.8 centimetres in length on average, Spirobranchus has a very well developed internal organ structure, housing a central brain with several supporting ganglia and a nephridium which performs the same function as the kidney in vertebrates, removing waste products from the body

What is your favourite Annelid? It can be in terms of physical or functional beauty...

This is my first in a series of articles I will be writing on beautiful animals in each animal phylum. Please write down what your favourite animal is in each phylum below!

The word comes from Greek akanthos and kephale (thorn and head respectively). So all Acanthocephalans are characterised by the synapomorphic trait of a spiky proboscis which has been turned inside out and looks somewhat like a thorny head

This phylum should not be confused with the genus of the same name, which belongs to a group of new world insect species which we are not interested in

Candidate: Pomphorhynchus laevis

It was a bit difficult to choose a species for this phylum due to the lack of physical variation within Acanthocephalae, so I went for the species which I thought had the most striking colouration. Pomphorhynchus laevis certainly stands out in this respect, showing off its bright orange hue whilst stuck to the gut walls of various species of fish and crustaceans. Indeed, all individuals of this phylum are parasitic and have a particularly complex life cycle, infecting multiple different aquatic organisms as it progresses through its own life stages. The sharp spikes on its eversible proboscis is used to stick to its host. In fact its proboscis has such a strong adhesive force that it has inspired a new type of skin graft with similar thorns on it to stick very well to the patient receiving the graft whilst causing minimal damage to the patient during application and removal. This is an example of biomimetics

The P.laevis are deceptively clever as well. By altering the serotonergic activity of their host’s brain (in G.pulex), they are able to make the host exhibit photophilia as opposed to the photophobia commonly found in uninfected G.pulex. This makes the host more likely to be detected by predators as they are more visible under the light. If the predator ingests the host, it makes transmission of P.laevis much more likely

This beautiful spiky head worm causes all sorts of lasting damage to its various hosts. For example, it reduces the concentration of phenoloxidase enzyme in the host, inhibiting its immune system and making it more susceptible to infection by bacteria. It also inhibits the host’s digestive system by releasing various neurochemicals into the alimentary tract

Honestly this one was difficult to choose as all Acanthocephalans look kinda similar and not the most appealing to the eye...