Behind Green Eyes: New species of deep-water hermit crab finds itself unusual shelters

‘Green-eyed hermit crab’ is the common name for a new species recently discovered off the West Coast of South Africa. Apart from its magnetic stare, however, there is a number of characteristic morphological traits and an unusual home preference that all make the crustacean unique.

Lara Atkinson_SAEON_offshore benthic ecologistFormally named after the University of Cape Town (UCT) alumnus Dr Lara Atkinson, the new hermit crab Paragiopagurus atkinsonaeis described by PhD candidate Jannes Landschoff, UCT, and Dr Rafael Lemaitre, Smithsonian Institution, USA, in the open access journal ZooKeys.

The Green-eyed hermit crab measures merely 70 mm in length and sports a coloration of mottled orange nuanced with cream to white. Among its distinct traits is the significant sexual dimorphism, where the males grow much larger right chelipeds in comparison to females.

Much like other hermit crabs in its family (Parapaguridae), the little crustacean does not use the shells of other molluscs to shelter its vulnerable body, but rather finds a home in the soft, polypy masses built from sand and material created by sea anemones which go on to live on the backs of these crabs in an amazing symbiosis.

“So, when you hold it [the hermit crab], it’s just organic material glued together with some sand,” explains Jannes in the UCT’s announcement about their discovery.

“Even more curiously, parapagurids start off in the usual way, occupying a tiny gastropod shell. But these eventually become deposited within this non-calcified ‘amalgam’ created by the anemones. As the hermit crab grows, its live ‘shell’, or carcinoecia, grows with it.”

2017-07-11-Sympagurus_dimorphus

The new species was discovered during a three-week survey back in 2013, conducted by the Department of Forestry and Fisheries and the South African Environmental Observation Network in the shallower deep waters (199 m to 277 m) off the West Coast of South Africa. Lara was on board one of the vessels when an unusual green-eyed crab turned up among the numerous specimens collected in one of the trawls. It was at that moment that she noticed that there was something peculiar about it and sent it for identification.

Restricted to a surprisingly small area for no obvious reason, the new species might be just bringing up some very important conservation messages.

“The area isn’t noticeably biologically or oceanographically distinct, but more detailed sampling from the area will tell us more about the habitat conditions. Future studies need to take this into account and give the area more research attention. If there’s something unusual about the site, you’d want to be careful, especially with mining operations along the West Coast,” says Jannes.

“Incidents like these are flags for future protection. The bottom line is we know so little about these offshore habitats from an ecological point of view. And if you’re planning for a marine protected area, you have to know what it is you’re protecting in that area.”

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Original source:

Landschoff J, Lemaitre R (2017) Differentiation of three common deep-water hermit crabs (Crustacea, Decapoda, Anomura, Parapaguridae) from the South African demersal abundance surveys, including the description of a new species of Paragiopagurus Lemaitre, 1996. ZooKeys676: 21-45. https://doi.org/10.3897/zookeys.676.12987

Caught red-handed: The ‘Candy striped hermit crab’ is a new species from the Caribbean

Recent underwater photographs and video obtained using scuba equipment by underwater photographer Ellen Muller at dive sites in the National Marine Park of the southern Caribbean island of Bonaire revealed the presence of a small, secretive and brightly colored red-striped hermit crab that proved to represent a species new to science. The new few-millimeter species is described in the open access journal ZooKeys.

Extra ImageThe color pattern reminded author Dr. Rafael Lemaitre, Smithsonian Institution, USA, of traditional candy cane, and thus he assigned the common name “Candy striped hermit crab”. Meanwhile, the scientific name of the new species is Pylopaguropsis mollymullerae after Ellen Muller’s young granddaughter Molly Muller. The underwater photographer believes that the honor would “inspire her to continue the tradition of protecting the amazing and fragile diversity of marine life in Bonaire”.

The unusual hermit crab was first photographed inadvertently alongside a “flaming reef lobster”, while observing invertebrates that aggregate in crevices under a large coral ledge. Subsequently, more hermit crabs were photographed in various crevices shared with moray eels such as the “broad banded moray”, “spotted moray”, and “green moray”. When permits were obtained from the Government of the Island Territory of Bonaire, a few specimens were collected and brought for study to the Smithsonian Institution. The formal description was then prepared for publication and specimens were deposited in the collections of the National Museum of Natural History, as required by scientific rules when naming new species.

The shape of the right, or major, pincer of this new hermit crab species is remarkable and unique with its shape and massive size when compared to the body. The underside of the claw of this pincer is deeply excavated, scoop-like. The function of the pincer and claw, however, is at present unknown, although a video shows that it is used by the hermit crab to push itself while crawling along the bottom.

Image 1The behavior of this new hermit crab is intriguing. Is there an ecological association of this new species with moray eels? Could this new hermit crab species function as a “cleaner” or a “den commensal”? At least in one instance, an individual was observed crawling on the body of a “broad banded moray”, perhaps feeding on mucus or materials present on it. These observations could be interpreted as evidence of some kind of symbiotic association, or den commensalism, between the two animals. The brightly colored pattern of the hermit crab with red stripes and very long, hairy antennae are also typical for most crustaceans considered fish “cleaners”.

“Cleaning” parasites or fouling organisms from the body of many cooperating fish, or removal of undesired food particles by certain small and colorful shrimps has been known for nearly 60 years, but never has a hermit crab been documented to engage in such type of ecological association. Further studies are needed in order to confirm the true ecological role of this fascinating hermit crab.

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Original source:

Lemaitre R (2017) Discovery of a new species of hermit crab of the genus Pylopaguropsis Alcock, 1905 from the Caribbean: “den commensal” or “cleaner”? (Crustacea, Anomura, Paguridae). ZooKeys 646: 139-158, https://doi.org/10.3897/zookeys.646.11132