At last and unexpected: the Sponge crab, Dromia personata, in the Netherlands

fig. 1  Sponge crab, Dromia personata (NL: Wolkrab). Zeelandbrug, the Netherlands, 6-10-2016.

At last: on 6 October 2016 - after 42 years - I found a Sponge crab, Dromia personata (NL: Wolkrab) and what I never expected: in my home country!

On 11 August 2016 Floris Bennema and Godfried van Moorsel found a Sponge crab while diving at the Zeelandbrug, a dive spot in the Oosterschelde (Eastern Scheldt). They published their discovery at NatureToday on 16 August 2016 and recently (with Reindert Nijland as co-author) in detail in 'First records of the sponge crab Dromia personata (Brachyura) in the Netherlands and its historical findings in the North Sea' (click here for a PDF). A Sponge crab in the Oosterschelde? At first I thought they were joking... 

fig. 2  Sponge crab, Dromia personata (NL: Wolkrab) holding on to the sponge Celtodoryx ciocalyptoides 

(NL: Gele wratspons). Zeelandbrug, the Netherlands, 6-10-2016.

At last

Since 1976 - after I bought a copy of 'The Hamlyn Guide to the Seashore and Shallow Seas of Britain and Europe' by Campbell and Nicholls in 1976 (see my post of 1 October 2009) - I have shortlist of creatures I would like to collect for my aquarium. The Sponge crab is one of them: I liked its looks and it seemed relatively unharmful, which is good when you have a lot of different animals in your aquarium (more about its looks later in this post). So year after year, depending on where I spent my holidays, I looked for the Sponge crab, but I never found one single living specimen. Not in Greece, Croatia, Italy, France, Portugal, Spain, Canary Islands, Great Britain and Ireland; all countries where I should have been able to find one... As you can imagine, I was thrilled to know a Sponge crab was found in my home country and even at one of my favourite dive spots!

Needle in a haystack

I wanted to find that Sponge crab to take photo's. But I had to be patient because the next weeks I spent a holiday diving in Italy and Croatia (as usual I didn't find a Sponge crab there). In the meantime three other specimens had been seen. My first attempt was at 26 September. I had no luck: the swell was too heavy to explore behind the first pillar of the bridge. But my patience paid off: on 6 October after to be precise 8 minutes of diving I found 'my' Dromia!

fig. 3  Celtodoryx ciocalyptoides (NL: Gele wratspons), an invasive species of sponge which forms huge banks up to 

25m2 with a maximum thickness of 50 cm. St. Annaland, the Netherlands, 1-3-2017.

I swam to the first pillar and descended. The first 15 meters behind the first pillar the bottom consists of large boulders and smaller stones. The boulders are covered with the sponge Celtodoryx ciocalyptoides (NL: Gele wratspons)(fig. 2-4), an invasive species which forms huge banks up to 25m2 with a maximum thickness of 50 cm. For more information about Celtodoryx click here.

Hence their name Sponge crabs camouflage themselves by cutting off a usually quite oversized piece of sponge, which they hold on their back with their last two pair of 'walking' legs (fig. 7). So how to find this crab, possibly camouflaged with a piece of sponge on a bank of the same sponge?
I swam past a boulder of about 80 cm high with an almost vertical slope on which a small piece of Celtodoryx was attached. Strange to find this sponge on a vertical slope. It also looked as if there was a space of a few millimeters between the sponge and boulder, but I could be mistaken because the water was - as usual at this dive spot - quite muddy.

I tried to pick it up and however it seemed to move in a way as is usual with cushion forming sponges, I believed it to be fixed to the boulder. So alas, no Sponge crab. But when I released the sponge, it moved by itself. Sponges don't move: bingo!

It was impossible to take photo's the way he (it appeared to be a male specimen) was hiding, so I carefully moved him to a place between some smaller stones surrounded by sand. Otherwise - if he would make a run - I would loose him instantaneously between the large boulders. I made a lot of photo's and in between I moved him a few times. Thereby the sponge he was holding on its back came off. I picked it up and after I made some photo's of the 'naked' crab, I presented it back to him. As I expected, he picked it up immediately (fig. 14) and fixed it with his hind leg pincers (fig. 10).

fig. 4  Sponge crab 'hiding' under its sponge camouflage, Celtodoryx ciocalyptoides (NL: Gele wratspons). 
It is almost impossible to discover a not moving specimen. Zeelandbrug, the Netherlands, 6-10-2016. 

The Sponge crab was exactly as I thought it to be: a bit clumsy, furry 'teddy bear'. It is very funny to see him crawling, because he walks like a Gorilla: he is making use of its claws for walking. This is probably due to the absence of use of the last two pair of walking legs and its rounded shape. The oversized sponge on its back is not making it any better.
You can find lovely video footage of a Sponge crab striding like a 'Silverback' by Paul and Maria Engels (click here) and Hans Vulink (click here). Both specimens were discovered at the Zeelandburg in 2016. Hans took his crab to Lake Grevelingen to film it and then returned it to its original spot. Paul and Maria Engels shot their video on site.

As he walked away two Velvet swimming crabs, Necora puber (NL: Fluwelen zwemkrab) crossed its path. Blue velvet crabs are aggressive crabs and one of them was quite large. But he wasn't impressed and used the oversized sponge as a battering ram to make way. That was the last I saw of 'my' Sponge crab. It was worth the wait of 42 years!

Observations

A list of observations of Sponge crabs in 2016 and 2017 in the Oosterschelde is added by Van Moorsel e.a. (2017). I received photo's and further information after a request on the Facebook-page of the ANEMOON-foundation to complement the list (fig. 5). I also wanted to find out if the same specimen could have been photographed by different divers. Subsequently I had to do some research; I turned out to be no Sherlock Holmes...

fig. 5

Specimens can be distinguished if they show some kind of damage. For example: the Sponge crab I found had abrasions on its left claw: hairs were torn away leaving a bald patch (fig. 2). Astrid Vis' specimen has a more or less identical damage, but on its right claw. A photo of a specimen Marco Vinke found at Goese Sas, shows a crab with many abrasions on its left claw. But comparison is only possible within a certain time frame. If you find an undamaged specimen at the specific locations of the quoted examples, it could be another specimen, but also the same specimen after moulting: with its new shell the hairs are back! And to make it even harder: most of the photographed and filmed Sponge crabs did not show any kind of damage. 

I did my best to find as many specimens as possible, but I can only subscribe to Van Moorsel e.a. (2017): at least 5 specimens are found in 2016 and 2 in 2017. In the list (fig. 5) you can find the specimens of which I am 100% sure they are unique. 

Unexpected and an even earlier record!

Because of climate change, in some cases the relative mild winters of the last years and increasingly favourable conditions in especially the Oosterschelde (Van Moorsel e.a, 2017), a lot of species originating from the coasts of France (Boulonnais, Normandy, Brittany) and further south have populated our coast and are becoming more and more common. So why did I not consider the Sponge crab as a potential newcomer?

The major population of this species is centered at southern Europe in warmer waters. In the literature I consulted, most authors describe Sponge crabs in the Mediterranean as common (Riedl, 1983, Falciai & Minervini, 1992, Nikiforos, 2002 and Weinberg, 2015). Sauer (1977) notes they are frequently found as by-catch in the Mediterranean.
Zariquiey Álvarez (1968) reports the species in the Iberian peninsula as quite common (between 10 and 30 m), Bourdon (1965) in Brittany, France as rare.
Van Moorsel e.a. (2017): 'Almost 200 years after the first record of Dromia personata in the North Sea, about 10 records are known from this continental sea.' 'Because Dromia personata is a Lusitanian species that reaches the limit of its northern distribution in the southern North Sea, its presence may be expected in years with high water temperatures.' Check their article for more information about their distribution, including a map with records. So, indeed unexpected.

But just before finalising this post, I received some additional and important information from Steven Campbell (Het Natuurhistorisch - Natural History Museum Rotterdam). He wrote that the museum has two specimens of Dromia personata in its collection originating from the North Sea (of which the second one is not yet catalogued on line):

1. Specimen catalog number NMR993700000426, North Sea (53° 4' 59.9988") (2° 0' 0"). This is in UK-waters, the Wash region according to Ingle (1996) and not unknown for Dromia records.
2. This one is much more interesting: a female specimen bought from J. Engelse (who had a souvenirshop in Meliskerke where he sold shells, crustaceans, fossils and minerals), that was catched in 1995 (probably between March and June) about 50 km north of Texel by a trawler from Scheveningen. So this is the very first record of a Sponge crab in the Netherlands!

Steven also wrote finding a lot of Sponge crabs as by-catch by fishermen in the north of Normandy. From 1998 to 2009 he collected >30 specimens at Veules-les-Roses,  >10 at Quiberville and at Saint-Valerie-en-Caux, Le Tréport and Dieppe 2 to 5 each. They were catched at a depth beneath 20 m. with a tangle net. Conclusion: they are more common and closer to 'home' than I expected!

Migration and mobility

How did the Sponge crabs arrive in te Oosterschelde? Van Moorsel e.a. (2017): 'The distribution of Dromia personata suggests migration into the North Sea from the English Channel, either as larvae or as adults. As the last two pairs of the crab’s pereiopods are used for sponge-attachment, only two pairs of legs are used for locomotion. Although D. personata is able to walk at considerable speed over short distances if necessary (pers. obs.), its capacity to walk over long distances, for example from the English Channel to the Eastern Scheldt, is probably limited.'

fig. 6  Locations in the Oosterschelde where Sponge crabs were observed (Schelphoek, Zeelandbrug, Goese Sas 

and Strijenham) and location of mussel and oyster farmers (Yerseke) in 2016 and 2017.

As I mentioned: they also use their claws for walking - so three pair of 'walking legs' - but I subscribe to their view: I can not imagine Sponge crabs walking long distances. They just don not have the build and agility to travel long distances, like for instance the Velvet swimming crab, Necora puber (NL: Fluwelen zwemkrab) or are as light as the Long legged spider crab, Macropodia rostrata (NL: Gewone hooiwagenkrab), which I have seen several times floating by in the current with spreaded legs.

fig. 7  Sponge crab, Dromia personata (NL: Wolkrab) for a few minutes without its sponge cover, showing its slightly displaced last two pair of legs equipped with pincers. Zeelandbrug, the Netherlands, 6-10-2016.

Again Van Moorsel e.a. (2017): 'The importance of larval transport should therefore not be underestimated. In recent years, several wind farms have been built in the Belgian part of the North Sea. The seabed around the wind turbines has been covered with stones. Perhaps these areas are used for settlement of sponge crab larvae. As such, they may function as stepping stones between the English Channel and the Eastern Scheldt. However, underwater observations and catches, preferably of juveniles, have not yet been made to confirm this.'

Another dilemma, but there are a lot of Decapod species of which we usually do not find juveniles, even of bigger and common species like the Common lobster, Homarus gammarus (NL: Europese zeekreeft). As adult Sponge crabs are difficult to spot, how about juveniles...

The final statement in this discussion by Van Moorsel e.a. (2017): '.. the appearance of the sponge crab may also be related to accidental introduction via mariculture, but this scenario is considered unlikely, due to absence or rarity in donor areas, and probably low survival during transport.'

I have no idea how and from where Pacific cupped oysters, Magallana gigas (NL: Japanse oester) and Common mussels, Mytilus edulis (NL: Mossel) are transported to Yerseke. Yerseke is the center of oyster and mussel farming located in the south-east Oosterschelde (fig. 6). Are they imported in water? From where? How sturdy are Dromia larvae? If I take the records in account: in 2016 two of the four locations are quite close to Yerseke: Goese Sas and Strijenham. And a lot of non-native, sometimes southern species have been unintentionally introduced by these farmers. Sometimes very 'successful'.

Conclusion: they could have been imported - grown specimens as well as larvae - by farmers, but the notification of Sponge crabs in the north of Normandy as common finds, the first record in Dutch waters in 1995 (albeit the only one until 2016), the mentioned records in Van Moorsel e.a. (2017) in the North Sea and last but not least the several wind farms creating a more favourable habitat in the Belgian part of the North Sea (Van Moorsel e.a., 2017) - functioning as 'stepping stones' - make a gradual influx in Dutch waters more probable. For me it is still a mystery that out of the blue at least 7 specimens are discovered in the Oosterschelde in a period of 13 months at 4 different locations!

Are they here to stay?

After the first observations of the Sponge crab in 2016 I wondered if they would survive our next winter. How do southern species cope in the Netherlands in general? I made a comparison of the quantity of some Decapods in Dutch waters, originating from southern waters, between the '80s and today from my own (diving, snorkeling and turning stones at ebb tide) experience and based on 'De Nederlandse Decapoda' (Holthuis e.a., 1986):

• Athanas nitescens (NL: Kreeftgarnaal): very rare, now quite common.
• Broad-clawed porcelain crab, Porcellana platycheles (NL: Harige porseleinkrab)(fig. 15): uncommon, now abundant.
• Black squat lobster, Galathea squamifera (NL: Zwarte oprolkreeft): very rare, now common.
• Velvet swimming crab, Necora puber (NL: Fluwelen zwemkrab): rare (albeit in waves; once more common but depleted after a strong winter), common since a few years.
• Arch-fronted swimming crab, Liocarcinus navigator (NL: Gewimperde zwemkrab): very rare, now common. 
• Leach's spider crab, Inachus phalangium (NL: Gladde sponspootkrab)(fig. 8): very rare, now less common.

fig. 8  Leach's spider crab, Inachus phalangium (NL: Gladde sponspootkrab). Katshoek, the Netherlands, 1-11-2011.

Summarised: southern Decapods are doing well and you should expect Sponge crabs to have a fair chance of at least surviving our mild winter of 2016-2017. As you can imagine I wanted to know if 'my' Sponge crab had outlived the last winter and I have tried to retrieve this specimen or any other Sponge crab, but I did not succeed. 

Four Sponge crabs are recorded in 2017 at two (maybe three) locations (fig. 5). The first was a nearly dead specimen at the Zeelandbrug on 9 April by Maurits van Kosteren (pers. comm.): 'It was lying on its back and it had no sponge on its back. Because I thought it was dead, I picked it up. Then I saw its mouthparts moving, so it was still alive. I gently put it back on a stone and made some photo's.' There are two records of a Sponge crab at the Schelphoek (a dive spot 9 km west of the Zeelandbrug)(fig. 6). The first one on 27 July was holding Dead man's fingers, Alcyonium digitatum (NL: Dodemansduim) on its back and was found by Astrid Vis. On 2 August Kiki Vleeschouwers and René van Zweeden found another specimen with Celtodoryx ciocalyptoides. Finally one specimen was found on 28 August at a 'dive spot west of the Zeelandbrug' (possibly the Schelphoek?) carrying probably Celtodoryx ciocalyptoides.  

As to the answer to my question 'are they here to stay', I am at least in doubt. We had a mild winter, but I think still rather cold for Sponge crabs: in January and February 2017 the temperature was 4ºC. The water temperature at the discovery of the nearly dead specimen on 9 April was already 9ºC, but according to the description of Maurits van Kosteren I do not think it survived. And there are only four observations this year. But on the other hand: as you know by now Sponge crabs are difficult to find and - what I have not told yet - they are nocturnal, so the chance of finding one gets even slimmer.

Habitat

Sponge crab frequent all kind of habitats: stone, sand and gravel sea bed, eelgrass habitat, rocky shores and vertical rocky slopes with caves (Riedl, 1983, Noël, 1992 & Falciai & Minervini, 1992).

Sponge crabs are - depending on the region - generally found between 10 and 30 m. The account in Weinberg (2015) about the Mediterranean - from lower shore to 150 m deep - is surpassed by Pérez (1995) in case of the Canary Islands: from 2 tot 201 m! Pérez also describes juvenile Sponge crabs in tidal pools. Riedl (1983), Pérez (1995) and Steven Campbell (pers. comm.) note that they can be found in quite shallow water - even near the watermark - where there are vertical rocky slopes with a lot of caves.

Some parts of the Oosterschelde are suitable for Sponge crabs, especially at a diving spot like the Zeelandbrug with a mix of rocks and large boulders. And the Oosterschelde holds another pleasant surprise for this crab: 'Also, sponges and tunicates (especially non-native species), used as camouflage by the Sponge crab, are now omnipresent' (Van Moorsel e.a., 2017). I already mentioned the abundance of the non-native sponge Celtodoryx ciocalyptoides (NL: Gele wratspons), which species appears to be its favourite camouflage in the Oosterschelde.

fig. 9  Pinking shear claw with conspicuous pink-red fingers of the Sponge crab, Dromia personata (NL: Wolkrab). 

Zeelandbrug, the Netherlands, 6-10-2016.

What's in a name? Felt coat and other features

Apart from the name Sponge crab, Ingle (1980) mentions Sleepy crab and Weinberg (2015) Teddy bear crab. In French (Falciai & Minervini, 1992 and Noel, 1992) it is called dormeur, dormeuse, dormeur i.e. the sleeper (not to be confused with Cancer pagurus, the Edible crab (NL: Noordzeekrab) which is also called dormeur). In Dutch it is Wolkrab (translated Wool crab) and Sponskrab (as in English Sponge crab). The scientific name of this species, personata, means masked in the sense of camouflaged.

So the names are referring to its camouflage (masked, sponge), its behaviour (sleepy i.e. slow moving), its coat of tiny brown hairs (wool) and its general looks (teddy bear; more about that later in this post). Sponge crab as name is a bit unlucky: the crab uses a range of animals and seaweeds to camouflage itself (see further on). Apart from its camouflage, the most conspicuous feature if you have a proper look at this crab, is its felt coat. Except from the conspicuous pink-red fingers of its claws (fig. 9), the eyes and the antennae, the crab is totally covered in minute brown hairs. So Felt, Velvet, Furry or Wool crab would do better.

Whenever I give a lecture about marine life, I get questions like: why that shape? why that colour? Most of the times my reply is: I do not know. But if you might ask: why do Sponge crabs have a felt coat, maybe I know one reason. I glanced through an appendix in Ingle (1996) with 'Symbionts and parasites' on shallow-water crabs. A lot of species of crab are encrusted with seaweeds, sponges, shells, barnacles, tunicates, bryozoans and calcareous worms. Especially older specimens because they mould less frequent and are less active. The overgrow of barnacles can be disastrous for crabs, because they also settle on eyes and mouthparts. But I could not find photo's of Sponge crabs overgrown by any kind of species. Then I realised that the felt coat of the Sponge crab protects it against the deposition of unwanted species! Fortunate, because the Sponge crab is quite slow and therefore could easily overgrow.

I mentioned the colour of the fingers (like nail-varnish as a few authors note), but they are not the only conspicuous thing: the claws are like pinking shears (fig. 9). Very handy for cutting a piece of sponge, seaweed or a colony of tunicates in the desired size.

fig. 10  Sponge crab, Dromia personata (NL: Wolkrab) trying to get a grip on its sponge cover.

Zeelandbrug, the Netherlands, 6-10-2016.

Another prominent feature I already mentioned are the two pairs of last legs (fig. 7), which are slightly displaced on the back. With these legs, equipped with tiny pincers (fig. 10) at the end, they hold onto the acquired camouflage.

As for size: a carapace width of 10 cm is already quite big, but Luther & Fiedler (1975) and Noël (1992) mention 13 cm. For a further description of the species I refer to Ingle (1980) and Adema (1990).

Camouflage and behaviour

So Sponge crabs do not attach organisms on their carapace, but carry them around. Quite different from decorator crabs like Leach's spider crab, Inachus phalangium (NL: Gladde sponspootkrab)(fig. 8), Long legged spider crab, Macropodia rostrata (NL: Gewone hooiwagenkrab) and the Spiny spider crab, Maja brachydactyla (NL: Grote spinkrab)(fig. 11 &12). They have crooked hairs on their back and legs to which they fix all kind of organisms with their claws, in some cases after first chewing the lower end of the organism to enable it to be more securely hooked to the hairs. They can reach almost any part of their body with their claws to attach sponges, seaweed etc. I expect the Sponge crab is not even able to cover the front part of its back with its claws.

fig. 11  Spiny spider crab, Maja brachydactyla (NL: Grote spinkrab), Porthkerris, United Kingdom, 12-9-2013.   

fig. 12  Detail of the carapace of fig. 11 with the tiny hooks onto which the crab sticks all kind of things for camouflage.

As I already mentioned, Sponge crabs do not only carry a piece of sponge on their back for camouflage, but also seaweeds and animals like tunicates, corals, sea anemones and bryozoans. For a nice collection of photo's of Sponge crabs with all kind of camouflage, have a look at the page on DORIS. In Poore (2004) I saw a photo of a an Australian species of Sponge crab carrying a tunicate at least eight times as large as the crab. Sauer (1977) notes that if you place a Sponge crab in an aquarium and remove its sponge, the crab will search for any kind of camouflage and once was seen holding a congener on its back!

Schmitt (1965) gives a lengthy but very interesting account of Sponge crabs and their cover or housing as he calls it: '... in need of housing very methodically goes about cutting out the necessary material from a convenient sheet of incrusting sponge, using its chelae (red. = claws) as a cutter. As the piece is freed somewhat and as soon as its edge can be raised, the crab gradually works himself under, cutting away till the whole piece is dislodged. ... Very often the case is too flat, and it never fits exactly to the surface of the crab's back. The crab corrects this by pressing the sponge tightly to its back and bending it out. ... Dromia gets so used to its own sponge case that it can usually pick it out from many other sponges.' Some authors mention that the sponge or tunicates will grow on and will adapt to the shape of the crab.

As you can read and see (fig. 13) in Schmitt (1965) attiring its sponge cover is not as easy as it looks. In the earlier mentioned video footage of a Sponge crab by Hans Vulink you can see one in action after its sponge cover was temporarily removed.

fig. 13  The manner in which Dromia puts on its sponge coat (Schmitt (1965) figure after Dembowska).

Sauer (1977) and other authors note: 'The sponge serves as protection, however: no one has recorded an attack on the crab in its natural surroundings. Probably it is not an optical camouflage but a protection against tasting and probing predators like starfish or Octopus.'

I think starfish and Octopus are bad examples. I have never seen or read about starfish hunting for crabs (at least not in European waters) and Octopus - noted as their main predators - have perfect eyesight. I think it is a bit of both worlds. Optical it will work against big fish and Octopus' in daylight. At night the shape and taste of sponge or other collected organisms will delude Octopus' probing tentacles and big alien Decapods.

fig. 14  Sponge crab, Dromia personata (NL: Wolkrab) trying to get a grip on its sponge cover.

Zeelandbrug, the Netherlands, 6-10-2016.

Aquarium and more behaviour

Riedl (1983) describes it as robust animal for an aquarium. Luther & Fiedler (1975) note that a Sponge crab can be a nuisance in an aquarium, because in its search for camouflage it rips sea anemones and starfish apart. On the web I found some information regarding Dromia and its camouflage behaviour at AquariumDomain.com: 'While Sponge crabs typically have sponges affixed to their backs, they will sometimes harvest tunicates or even coral polyps for camouflage. By doing this they may cause harm to some soft or polyp corals, but this usually helps propagate these corals throughout the aquarium, more than it does harm to them.'

Luther & Fiedler (1975) tell its main diet is seaweeds. As I have observed a lot of crabs in nature and at home in an aquarium, I doubt they are mainly vegetarian. However only based on aquarium practice, the same (unknown) author of AquariumDomain.com corroborates my point of view: 'As with most all crabs, the Sponge crab is a scavenger that will eat most any meaty food. The diet of the Sponge crab should include meaty foods such as frozen brine or mysis shrimp, mussels or pieces of fish. This species will also eat any foods that get by the fish in the aquarium, making them good for keeping the aquarium free of excess and decaying food stuffs.'

On the website of DORIS and AquariumDomain.com Sponge crabs are described as (mostly) nocturnal. Rollin Verlinde in a (translated) reaction on the first discovery of the Sponge crab in the Netherlands on Facebook:  'In Croatia I found several specimens during a night dive; in daytime not one!' Steven Campbell (pers. comm.) has the same experience while snorkeling in Croatia.

As you may have gathered: I did not collect a Sponge crab for my aquarium. Because they are rare and I want every diver the joy to find, observe and photograph this extraordinary crab.

fig. 15  Broad-clawed porcelain crab, Porcellana platycheles (NL: Harige porseleinkrab). Goese Sas, 30-10-2013.

Teddy bear

As you know by now, I like Sponge crabs a lot. I like its globose shape, its cuddly felt coat, its clumsy and Gorilla-like way of walking, its camouflaging behaviour  and its grotesque appearance with the sponge on its back. What is not to like? It looks like a teddy bear.

Before I met the Sponge crab I called Hairy crabs, Pilumnus hirtellus (NL: Ruig krabbetje) teddy bear-like, also because they are hairy and have a globular shape. And in the category 'wooly/cuddly' there is another contestant: have a look at the Broad-clawed porcelain crab, Porcellana platycheles (NL: Harige porseleinkrab)(fig. 15).

But for me the Sponge crab really fits the bill and more people are like-minded. Weinberg (2015) mentions - as said - the name of Teddy bear crab. Reindert Nijland (co-author in Van Moorsel e.a., 2017) is cited online (Kleis, 2017) about the 'teddy bear like' animal (translated). He also mentions a Dutch word in connection with the Sponge crab: 'aaibaarheidsgehalte', meaning it is highly suitable for petting!

fig. 16  Sponge crab, Dromia personata (NL: Wolkrab). Zeelandbrug, the Netherlands, 6-10-2016.

Acknowledgements

I want to thank Floris Bennema and Godfried van Moorsel for publishing their initial find and accompanied by Reindert Nijland for their article in Marine Biodiversity Records. Furthermore I thank Steven Campbell for providing the records of Sponge crabs in the collection of the Natuur Historisch Museum Rotterdam and other information about its distribution.
I thank Glen Biscop, Rob Bol, Martin Gruson, Paul & Maria Engels, Maurits van Kosteren, Marianne Ligthart, Ronald de Meijer, Lilian Schoonderwoerd, Lennard Vercouteren, Stefan Verheyen, Carl Verlinde, Marco Vinke, Astrid Vis, Kiki Vleeshouwers, Hans Vulink, Kris'na Wouters and René van Zweeden for sharing their records and in some cases photographs and video's. Finally I thank Steven Wouters for providing water temperatures of the Oosterschelde for the period 2001-2017.

Literature & weblinks

• Adema, J.P.H.M., 1990. De krabben van Nederland en België. ISBN 9073239028.
• AquariumDomain.com (Anonymous). Aquarium Hobby Online Resource and Social Networking Community for both Freshwater and Marine Aquarium Hobbyists. Click here.
• Bennema, F., 16-8-2016. Facebook post ANEMOON of the first discovery of the Sponge crab in the Netherlands. Click here.
• Bourdon, R., 1965. Inventaire de la Faune Marine de Roscoff. Décapodes - Stomatopodes. éditions de la Station Biologique de Roscoff.
• DORIS, Données d'Observations pour la Reconnaissance et l'Identification de la faune et la flore Subaquatiques. Click here.
• Falciai, L. & R. Minervini, 1992. Guide des homards, crabes, langoustes, crevettes et autres crustacés décapodes d'Europe ('Guida dei Crostacei Decapodi d'Europa'). ISBN 260300994X.
• Henkel, D. & D. Janussen, 2014. Redescription and new records of Celtodoryx ciocalyptoides (Demospongiae: Poecilosclerida) - A sponge invader in the north east Atlantic Ocean of Asian origin? Click here for a PDF.
• Holthuis, L.B., G.R. Heerebout & J.P.H.M. Adema, 1986. De Nederlandse Decapoda. Wetenschappelijke Mededelingen KNNV, nr. 179. ISBN 9050110037.
• Ingle, R.W., 1980. British Crabs. ISBN 100198585039.
• Ingle, R.W., 1996. Shallow-water crabs. ISBN 1851532587.
• Kleis, R., 2017. Sponskrab mogelijk een blijvertje. Resource, WUR magazine. Click here.
• Luther, W. & Fiedler, K., 1975. Handboek voor de Onderwaterfauna in het Middellandse Zeegebied. ISBN 9060103580.
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• Vis, A. 30-7-2017. Facebook post ANEMOON of the discovery of the Sponge crab with Dead Man's Fingers on its back. Click here.
• Vulink, H., 2016. Video of Sponge crab (walking and putting on its sponge). Click here.
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