Make way for 2013!

Sunflower star: an amalgam of superlatives - part 2

Part 2 of the sea stars of Vancouver Island features one specie: the sunflower star, Pycnopodia helianthoides. With more in information about biology, behaviour and morphology.

It is the most impressive sea star of British Columbia. In my post of October 21, 2008 I described it as massive and it is. This one (top) looks like the beheaded Medusa. 

It can reach a diameter of approximately 100 cm, so it is the largest sea star on earth, albeit not volume-wise.

I saw a lot of sunflower stars, but not in numbers as described and shown on echinoblog.blogspot.com: in 2010 huge numbers of sunflower stars were seen in British Columbia. I can not remember seeing more than 20 at any dive. For more information have a look at this very informative and extensive blog about echinoderms. 

The sunflower lives from the intertidal zone - nearly always subtidal - to 120 meters deep. One specimen was found at 435 meters deep, but that's probably an error (Lambert, 2000).

One of the days at Rock Bay it was extreme low tide. To my surprise this sunflower star didn't bother to move to deeper water, although it can walk quite swiftly. 'It may be the largest and fastest seastar in the world. It can move up to 3 meters per minute, and has been known to travel at least 3 km' (Cowles, 2005). 

But maybe there is no reason for such behavior. Apart from the Alaskan king crab and Solaster dawsoni, the northern sun star, it hasn't any enemies. In the Netherlands gulls frequently swallow starfish like Asterias rubens (NL: gewone zeester) (in WoRMS: Echinaster sepositus, a mistake?), but they are relatively small. A sunflower star this size is too big to swallow.

Where as some sea stars have a typical habitat, the sunflower star is not picky. Sand, gravel and mud bottoms, rocky coasts, among seaweeds, on pontoon bridges.

I once picked up a sunflower star to show it to my wife. It was heavy, I think about 3 to 4 kg. I turned it upside down to prevent the tube feet to stick to my glove. To my surprise it still sticked: with its pedicellaria. These are pincerlike appendages with which it can clean its back against on growing seaweeds and barnacles. And as it turned out to defend itself. In Barnes (1968): 'pedicellaria are used for protection and to capture small animals.'

The sunflower star is a voracious predator: on bivalves, snails, chitons, urchins, other sea stars, sea cucumbers, crabs and it also scavenges on dead animals. So almost anything this carnivore can lay its arms on...

These brittle stars, Ophiura species, were fleeing from the approaching sunflower star. Normally they are not quick enough to escape. But in this instance the sunflower star was not hungry (enough) and let them escape.

This sunflower star excavates bivalves for food by transporting sediment particles. It can evert its stomach, but if the prey is small enough (not to difficult when you are that big) it swallows it whole.

The shell was already cleaned out.

This lined chiton, Tonicella lineata, in the arms of a sunflower star should be terrified.

Colour variations.

Like lava.

The skeleton of sea stars consists of multitudes of small calcareous plates called ossicles that move with one another, forming flexible joints. In the sunflower star they are not connected to each other, hence the flexibility of this sea star. If you take a sunflower star out of the water its weight will easily tear it apart, so you have to support it well.

The fingerlike projections, the papulae, are thin-walled and are extensions of the coelom (the internal body cavity) that protrude between the calcareous plates. They are in short its gills.

The sunflower star has a lot of spines, which are hidden in the rounded cushion like appendages (one in each). I know they appear when you disturb the sea star. But ever so often you can see the spines when there is no visible reason for 'agitation'.

Its numerous (up to 15.000) tube feet.

Young specimen. They start with five arms and gradually grow more arms.

And more.

You don't know how they increase their arms in number? Like this!

Aeolidiella alderi: new species in Dutch waters

Aeolidiella alderi (the first 3 photo's)

While we (KNNV Strandwerkgroep Waterweg-Noord) were beachcombing and turning stones at low tide at Burghsluis (Oosterschelde, the Netherlands), Jurriën van Deijk found a 18 mm small sea-slug. Attached under a stone with hardly any undergrowth. We made some photo's to be able to identify the species. At first I thougt it was a Facelina or Coryphella species. 

It is a pity I just made some photo's for identification and not in its natural surroundings. On the other hand: they were fortunately good enough for identification.

After studying my photo's and looking at the species found in Dutch waters, I thought: let's put it up for question on the Facebook 'study group NE Atlantic Nudibranchs'. 8 minutes later Joao Pedro Silva from Lisbon, Portugal (it is a small world!), commented: 'I think the aeolid is Aeolidiella alderi. Look at the elongated cnidosacs of the first cluster of cerata'. So, I had been looking in the wrong direction: this would be a new species for the Netherlands. Of course there is always some doubt, because a 100% identification is only possible by extracting the radula or comparing DNA. But after other positive identification comments of several people and studying the characteristics I am sure it is Aeolidiella alderi (Cocks, 1852).


One of the identification features: the eyes are visible just behind the rhinophores.

It has no English or Dutch name. As a Dutchmen it is a bit presumptuous to give it a common English name, but I will give it a go: collared sea-slug. Likewise in Dutch: gekraagde vlokslak. This way I emphasize one of the characteristics of this small nudibranch: 'the numerous cerata have white cnidosacs which are particularly large in the anterior cluster, giving a white collar or ruff to the animal' (www.habitas.org.uk). In layman's words: the outgrowths at the front of the animal (not the large 'horns') have large white containers (for storing the stinging cells of sea-anemones) forming a white collar.

For the Dutch readers: ruff betekent molensteenkraag (de bekende witte kraag die figureert op schilderijen uit de Gouden Eeuw). 

For further reference look here and especially for key identification features and a comparison with related species Aeolidia papillosa and Aeolidiella glauca here. 

Its big nephew: the common grey sea-slug, Aeolidia papillosa (Linnaeus, 1761) (NL: grote vlokslak).

No white collar and the rhinophores and upper side are densely pigmented. It is not difficult to distinguish the two species.

Aeolidiella glauca (Alder & Hancock, 1845) (NL: kleine vlokslak). Again no common name. Glauca means bluish-grey or green. The authors Alder and Hancock must have been colour blind or more plausible, described a preserved and so often discoloured specimen as a then new species. Who will give it a proper common name? Both photo's of A. glauca were staged/not in a natural surrounding.

The body of A. glauca is broader than that of A. alderi and again: it has no white collar.

It has been a wonderful year for 'nudilovers' in the Netherlands, as was 2011. The Oosterschelde was riddled with Geitodoris planata (NL: millennium wratslak) and harlequin, Polycera quadrilineata (NL: harlekijnslak). I have read messages like: 'this dive I have seen more than 200 harlequins'. Rare species like Janolus hyalinus (NL: wrattig tipje) were seen. In 2011 divers discovered 4 new species for the Netherlands at the Doggersbank.

Geitodoris planata (millennium wratslak)

So, has something changed in Dutch waters or is it increased interest for nudibranchs amongst divers? The latter is certainly true. This year a 'Zoekkaart Nederlandse Zeenaaktslakken' (an identification card for Dutch Nudibranchs) is published and I think they will sell a lot of them to the diving community.

The harlequin, Polycera quadrilineata (NL: harlekijnslak)


I want to thank Jurriën van Deijk for finding A. alderi. And Joao Pedro Silva, Marco Faasse, Brendan Oonk, Bernard Picton and Rob Dekker for their comment. 

Janolus hyalinus (NL: wrattig tipje)

Sea stars of Vancouver Island - part 1

I started this blog with some posts about the marine biology of Vancouver Island. I was impressed by the rich underwater life of this part of Canada. That was before I could dive. So last summer we revisited the island. I made 10 dives, 3 snorkeling trips and did some beachcombing.

I hoped for a lot of new species and to do something I dreamed about since 1976: diving in an underwater forest of kelps. To be honest: I already had been diving in kelp forests last year in Ireland and in May in France. But this was different because of the size of the kelp forest. I dived at three spots in the vicinity of Nainamo: Cottam Point, Tyee Beach and Neck Point. The fourth divespot was Rock Bay (40 km north of Campbell River).

My first dive was special. I expected clear water, as I could remember of my trip in 2008. It was not.  A bit of a disappointment, but the number of species of sea stars made my day: 12 species in total! That's why I start with a post about sea stars.

The 16 species of sea star - I found in total - in this and the next post are presented in taxonomical order.

This is the vermilion star, Mediaster aequalis. Up to 20 cm across. It is an omnivore: it feeds on sponges, bryozoans, loose algae, detritus and dead animals.

This specimen has lost one of its arms, which is regenerating. A little spider crab is hitchhiking.

The beautiful upside (called aboral) with table-like tops (called tabulate plates). Like little flowers.

The leather star, Dermasterias imbricata. A common species in British Columbia.

Lambert (2000; see further ahead) about the diet: 'On exposed coasts it eats primarily sea anemones and compound sea squirts. In sheltered waters mostly sea cucumbers, encrusting sponges and sea pens. ... All those observed in Gabriola Passage were feeding on bottom detritus.' He does not mention bryozoans like the kelp-encrusting bryozoan, Membranipora serrilamella, on which I have seen a lot of them feeding. In this case growing on five-ribbed kelp, Costaria costata. The leather star seems to be a rather opportunistic feeder: it likes whatever is around.

Membranipora serrilamella in detail, showing the honeycomb like structure and individual polyps. 

It is a thick and leathery sea star, up to 30 cm across.

The stomach inside out. At lectures and nature trips I often tell about the feeding habits of sea stars in relation to human table manners. What if you were in a restaurant and you pulled your stomach out of your mouth and put it on the artistically arranged food on your plate? 'Sir, would you like to leave this restaurant at once!'
I took this leather star of five-ribbed kelp, where it was feeding on the before mentioned bryozoan.

This is the common sun star (English/European name) or rose star (North American name), Crossaster papposus (NL: zonnester).

The colour is variable, usually with a concentric pattern, as is not the case with this specimen. Up to 34 cm across. It eats sea slugs, bivalves, bryozoans, sea squirts and other sea stars.

This is the same species but from Ireland. It is one of the few species of sea stars you can find in the Pacific and the Atlantic ocean. This colour pattern is rather typical for European specimens.

The typical polyp-like structures are called pseudopaxillae. These are skeletal plates consisting of a broad base and an erect column bearing small spinelets.


Solaster dawsoni, the morning sun star. It can grow up to 40 cm in radius. This is a juvenile.

It is a 'top predator': it feeds on a lot of sea star species, including other morning sun stars. A cannibal, but that is not so unusual in marine species. Lambert (2000) on attacking its own species: 'but its success rate is low because of a well developed escape response. S. dawsoni bends its arm back and pushes the attacker off while rapidly moving away (10 cm/min.).'


He does not mention the morning sun star preying on the California sea cucumber, Parastichopus californicus (left on the photo above), but mentions that it swims away when contacted. Sea cucumbers are related to sea stars, the primal food of this sea star. And as other sea stars are preying on sea cucumbers, I am in no doubt he is also preying on them.

Solaster endeca, the northern sun star. Looks like a bloated version of Solaster dawsoni. Another species you can find in the Atlantic and Pacific Ocean. Although their diets are very different. Lambert (2000): 'In the Atlantic it is reported to be a voracious feeder on sea stars and molluscs. On the Pacific coast it neither attacks nor evokes escape responses in other sea stars.' There it feeds on sea cucumbers, bryozoans and sea squirts. Up to 40 cm across.

Solaster paxillatus, the orange sunstar. It is said to be rare in British Columbia.

Lambert (2000): 'is probably carnivorous, like other species of Solaster. Stomach contents recorded are a sea cucumber and the blood star, Henricia leviuscula leviuscula.' Up to 37 cm across.

Another beautiful sea star of BC-waters: Solaster stimpsoni, the striped sun star. I saw a lot of these sea stars: they are easily observed and identified with their striking colour pattern. Up to 50 cm across.

This is the excellent identification guide by Philip Lambert I am referring to. With a description, photo's, drawings and information about biology, diet, distribution, propagation etc., including an explanation of the scientific name.
A whole lot of information in this post comes from this book, as well as their identification. For sale at a very reasonable price of $26. Highly recommended.