Three starfish types
By now you will have come across a starfish or two and there are many types out there. However, those found commonly in the intertidal region and which can be identified can be reduced to a few species.
We introduce a few here and more when discussing similar species in the text and links. You will see what they look like in different situations and learn of their ecology to help with ID.
The species in focus are:
common star/seren fôr (Asterias rubens)
common brittlestar/seren frau (Ophiothrix fragilis)
cushion star/clustog fair (Asterina gibbosa)
You will then be tested.
These are the most common starfish found on shore, but there are plenty of species of starfish and paying attention to shape, arm number, colour and rigidity of the arms can help to ID any less common ones found.
The “thick-armed starfish” have been found stranded on-shore commonly and so are described as part of our Beached! project to see the variety and how to decipher. Note many of these would not be found in the intertidal area when alive, but it’s good to know in case.
Some of the possible brittlestar comparisons between those most commonly found in the same area if not habitat are listed below.
1. the common brittlestar has long bristles called spines along the entire length of the arms in comparison the sand brittle star has only a few and are shorter.
2. the black brittlestar can be very similar to the common, so look for a lack of banding on the legs to ID the black brittlestar
3. the small brittlestar is found under stones, has relatively longer arms than the common and lacks the long bristles
The Cushion star found under rocks at low tide is most likely the most common species, but in the North Wales area there is another species to consider.
1. the most common cushion star is un-patterned whereas the rarer cushion star (Asterina phylactica) has a clear, red central star-shaped patterning of dots
2. it also has white dots on the arm tips.
A few starfish
common star/seren fôr (Asterias rubens)
©North Wales Wildlife Trust
- a large starfish, it can grow to over 50cm across (including arms), but is usually 10-30cm
- it has 5 arms (NB some could be missing and occasionally they have extra)
- most commonly orange in colour, this can also be beigey in colour and often has purple parts on closer inspection
- it is covered in white spines, making its surface look studded, stubbly.
Cushion star/clustog fair (Asterina gibbosa) 
©North Wales Wildlife Trust
- a starfish with very stubby arms
has an indistinct central disc - beige, orange, orange-grey in uniform colour (sometimes looks like it’s collected silt over surface)
- likes living under rocks
- found a low shore and very common in sheltered locations.
common brittlestar/seren frau (Ophiothrix fragilis)
©Matilda Pears
- a large brittle star this animal can have a central disc of up to 2cm across
- has arms covered in long spines
found at low shore - arms often have distinct patterning of coloured bands
- can be a variety of different colours.
small brittlestar (Amphipholis squamata)
©North Wales Wildlife Trust
- a very small brittlestar, animal including arms up to 2cm across
- arms with spines, but not long ones
- found under rocks intertidally at low shore, often in groups, but not always
- grey-yellow-ish in colour
- uniform colour
Alternative factoids
Starfish come in all sorts of shapes and sizes, there’s plenty more to learn. You will not be tested on this extra, interesting facts.
Common stars can make up the majority species in storm-caused invertebrate wrecks on North Coast shores in North Wales.
Brittlestars are suspension feeders, collecting plankton from the water body with their arms or sometimes deposit feeders collecting food from the sediment.
Starfish can survive losing an arm or two and will re-grow them.
The common star feeds by opening a small gap in its prey’s attachment (either between two shells of the bivalve or between the shell and rock for limpets etc), everting its stomach out of its own body and placing it into the gaps to ingest its meal
The next section is the quiz. Click to begin the quiz, the questions will appear below. If you get any one question wrong within each quiz page, the you will be marked as wrong for the whole page. Answers will appear one you’ve finished each question.
You will be tested on what you’ve learnt so far using the reading and video info. Don’t worry too much, as once you’ve been out on the shore, the ID features you’ve learnt about will make more sense and after a couple of visits you should feel more confident about your ID.
Good luck!