It happened again, just when I thought an identification would be easy, it turns out it isn’t. No guarantee as always, I’m only looking at photos here!
But who would have thought, the identification to the level of the genus was as simple as it gets. From approximately 800 species of hermit crabs (superfamily Paguroidea), only 17 species live terrestrial. Hermit crabs share the group, or infraorder Anomura with porcelain crabs, squat lobsters, and some others. True crabs, like ghost crabs, or land crabs, form the infraorder Brachyura with almost 7000 species.
One of the 17 species of hermit crabs can be excluded from my search, and that is the only species of the second genus Birgus, the giant coconut crab B. latro. I must admit, it did not know that juvenile coconut crabs live in shells like other hermits. You wouldn’t see a difference as long as they reach a good size, and start going without shell. For sure I can say that on the island in the Maldives, where the crab from the picture was found, there were no coconut crabs.
From 16 Coenobita species, some were only found in the new world. Even more helpful to me was this article: ‘Hermit crabs (Crustacea Decapoda Anomura) of the Maldives with the description of a new species of Catapagurus A. Milne Edwards 1880’ from 1998. P. Hogarth et al identified three species of land hermit crabs in the Maldives, of course without visiting all 1192 islands. To make my life easier, I assumed that my crab belongs to either of the three: C. brevimanus, perlatus, or rugosus. Here’s a video comparing some species. Still I find it very challenging, especially when you can’t see all the important details.
C. perlatus is bright red as adult, and white with red bands as juvenile. I’m sure this one was around on the island, bigger than the one in the picture, but also more shy. When I compare C. rugosus and brevimanus, the tendency goes towards brevimanus. I guess I will have to look at all my photos with hermits now and see what I’ve seen… The ‘Land Hermit Crab Owners Society’ on Facebook confirmed my guess (Thanks again!), and it seems there were other species in that area as well.
Looking for a story around hermit crabs, we already have the facts that they are not true crabs, they have a famous sister, the world’s largest arthropod, the coconut crab. One reason why I could easily find plenty of information online, is because Coenobita are popular pets. Online I just found two small ‘purple pincher’ (Coenobita clypeatus) on Amazon for 21USD. Another species in the hobby is Coenobita compressus, the ‘Ecuadorian’. In forums they might be referred to as ‘PP’ and ‘E’… In Singapore you can buy Coenobita rugosus, and only in 2016 C. lila was described from Singapore, Indonesia and Malaysia.
A reason for their popularity is the cute behaviour, being shy, but sometimes adventurous (they climb well!), and probably their cute sound. Yes sound! I’ve met dozens of hermit crabs on beaches, but I never heard one squeak. There are some videos on YouTube, like this here. The sound is for sure some kind of communication between the crabs, and it proves one more time that these tiny creatures have a life and social behaviour. The name Coenobita even refers to their communal behaviour. A hermit on the other hand is a person who lives in solitude, so the scientificname, and the common name are in opposition. It’s likely that their lifestyle in a shell made them hermits. Communal hermits. Totally understandable that they need a refuge sometimes!
When I almost finished writing about the hermit crabs, I found my story. A real hermit in the story of communal crabs. Johannes von Nepomuk Franz Xaver Gistel! A German naturalist with a remarkable Wikipedia entry. At least the English version has some uncommon comments. According to Wikipedia, Gistel had a bad reputation, and he must have stepped on some feet, namely Embrik Strand and Walther Horn. Strand was a Norwegian, tarantula enthusiasts know his name. Horn was born in Berlin, and worked on tiger beetles, he establishedthe genus Neocollyris for example. The source for their beef can be found here: Evenhuis, Neal L. (2016). “An enigmatic man with three names: brief biographical notes on Johannes Gistel (1809–1873) and a list of his forgotten Diptera taxa. A biography, bingo!
But first things first, how is Gistel related to hermit crabs? Hardly, but, he described a butterfly in 1848, and called it Coenobita. Same as hermit crabs! It is not possible to have two animals sharing the same genus, the scientificnamemust only belong to one species. Because Pierre André Latreille established Coenobita first, in 1829, for hermit crabs, Gistel’s name was a junior synonym and therefore not valid. There was more confusion around that work, including the Goliath birdeater Theraphosa (Strand was not involved), but that is for another time.
The Wikipedia article mentions that Gistel was the sole member of the Münchener Verein für Naturkunde, a society for naturalists, that existed from 1847 to 1850. There is an article from 1990 online, where several other members of that society are listed. It was written by Fritz Pfaffl, in a journal called ‘Der Bayrische Wald’, in 1990. Gistel was the editor, but there were many founders mentioned. Wikipedia might have a mistake there.
Neal Evenhuis describes a man, a ‘colorful person’, without academical degree, trying to play with the big guys of zoology. He stole their work, put his name under it, changed species’ names against all rules of taxonomy, and even changed his own name because of his bad reputation. I’m sure there is a good explanation for his behaviour, that clearly made him unwillingly a hermit. A person living in solitude.
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