Tag: symbiosis

Five new blanket-hermit crab species described 130 years later from the Pacific

A blanket-hermit crab grasping an anemone.

Since 1888, a lone crab species living in an extraordinary symbiosis has been considered to be one of its kind

At the turn of the twentieth century, two independent marine scientists – JR Henderson in 1888, and A Alcock in 1899, described two unusual blanket-hermit crabs from the Indo-West Pacific.

Unlike other hermit crabs, these extraordinary crustaceans do not search for empty shells to settle in for protection. Instead, they have developed a symbiotic relationship with sea anemones to cover their soft bellies. To do this, the crabs use highly specialized chelipeds to pull back and forth the anemone’s tissue to cover their soft bodies and heads whenever necessary – much like hiding under a blanket.

Among the numerous specimens collected during the famous HMS Challenger Expedition in 1874, there were two hermit crab specimens obtained from the Philippines. They amazed Henderson with their unusual physical characters, including an abdomen bent on itself rather than spirally curved, and the lack of any trace of either a shell or other kind of protective structure for their body.

As a result, in 1888, JR Henderson established a brand new genus and new species for it as Paguropsis typicus. The ending of the species name was subsequently grammatically corrected to Paguropsis typica.

A decade later, unaware of the previous discovery, A Alcock stumbled upon hundreds of hermit crab specimens off southern India, which exhibited quite spectacular behaviour. Having observed their symbiotic relations with sea anemones, the researcher also formally described in 1899 a new species and a new genus for his specimens.

However, shortly thereafter and upon learning of JR Henderson’s earlier work, A Alcock concluded that his hermit crab specimens and those of JR Henderson must be one and the same species, so the two scientific names were officially synonymized in 1901 in a publication with his colleague AF McArdle, with JR Henderson’s name taking precedence as required by the principle of priority set forth in the International Code of Zoological Nomenclature.

Now, 130 years later, an international team of scientists, led by invertebrate zoologist Dr Rafael Lemaitre of the National Museum of Natural History, Smithsonian Institution, USA, not only found that A Alcock’s Indian specimens were indeed a separate species, leading to the resurrection of its name as Paguropsis andersoni, but that blanket-hermit crabs are not as rare as previously thought.

In their recent publication in the open access journal ZooKeys, the biologists described a total of five new species and a new genus of closely related blanket-hermit crabs. Furthermore, they expect that other species are to be discovered, since there are many vast marine shelf areas and deep-sea habitats spread across the Indo-West Pacific yet to be sampled.

To develop their exceptional symbiosis with sea anemones, the blanket-hermit crabs have obviously needed just as extraordinary evolutionary adaptations. Perhaps the most remarkable of these are their specialized chelate fourth legs that allow for the crustaceans to effectively grab and stretch the thin-walled body of the anemones to cover themselves. For five of the species, the scientists report and unusual grasping shape for this cheliped that is reminiscent of bear claws, while in the other two the shape resembles ice-block tongs.

Unfortunately, the identity of the sea anemone species involved in the symbiotic relationship with any of the studied blanket-hermit crabs is currently uncertain, and their biology remains unknown.

A blanket-hermit crab 'wearing' an anemone. — A blanket-hermit crab ‘wearing’ an anemone.

So far, the genus described by JR Henderson as Paguropsis, contains five species distributed in the subtropical and tropical Indo-West Pacific, and living at depths ranging from 30 to 1125 m. These include the two species discovered in the 19th century, and three new species, one of which, Paguropsis gigas, is the largest known blanket-hermit crab that reaches a body size of 15 cm when fully stretched (a large size by hermit crab standards).

For two of the newly discovered hermit crabs, the new genus Paguropsina is erected to reflect the numerous similarities between the two species and their Paguropsis relatives. The Latin suffix -ina refers to the comparatively smaller size of the two species. Both blanket-hermit species of Paguropsina are found in the subtropical and tropical western Pacific at depth between 52 and 849 m.

“Here there is no shell to play the part of ‘Sir Pandarus of Troy,’ but the sea-anemone settles upon the hinder part of the young hermit-crab’s tail, and the two animals grow up together, in such a way that the spreading zoophytes form a blanket which the hermit can either draw completely forwards over its head or throw half-back, as it pleases,” Alcock once eloquently described his marine discovery.

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Original source:

Lemaitre R, Rahayu DL, Komai T (2018) A revision of “blanket-hermit crabs” of the genus Paguropsis Henderson, 1888, with the description of a new genus and five new species (Crustacea, Anomura, Diogenidae). ZooKeys 752: 17-97. https://doi.org/10.3897/zookeys.752.23712

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.

The 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.

The 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

Living together in mud: New bivalve species dwelling on a sea cucumber discovered in Japan

Most bivalves live in sand or mud or attached to rock surface. However, a new bivalve species described from Japan lives on a sea cucumber.

Ryutaro Goto, postdoctoral fellow in Museum of Zoology and Department of Ecology and Evolutionary Biology, University of Michigan, and Hiroshi Ishikawa, amateur malacologist in Japan, have their paper, describing the new species, published in the open access journal ZooKeys.

The new species, named Borniopsis mortoni(Galeommatoidea), was discovered in mudflats at the mouth of the Souzu River, southwestern Shikoku Island, Japan.

This bivalve has tiny brownish shells (up to 4.1 mm in length). The species lives attached by both its foot and byssal threads to the body surface of the earthworm-like sea cucumberPatinapta ooplax (Synaptidae). Individuals of B. mortoni are often found on the same host, yet sometimes there could be more than 10 individuals existing side-by-side.

The new species is dedicated to a famous British malacologist Brian Morton, emeritus professor of University of Hong Kong. He has described many interesting Pseudopythina species from mudflats in Hong Kong, now assigned to the genus Borniopsis.

Host sea cucumbers burrow in mudflats. Most likely, the B. mortoni bivalve uses the host burrows as shelter from predators.

The new species is one of the smallest species in this genus. With the burrow of the host sea cucumber being very narrow, the small body size of B. mortoni is probably a corresponding adaptation.

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Original source:

Goto R, Ishikawa H (2016) Borniopsis mortoni sp. n. (Heterodonta, Galeommatoidea, Galeommatidae sensu lato), a new bivalve commensal with a synaptid sea cucumber from Japan. ZooKeys 615: 33-45. doi: 10.3897/zookeys.615.8125

Tracing the ancestry of dung beetles

One of the largest and most important groups of dung beetles in the world evolved from a single common ancestor and relationships among the various lineages are now known, according to new research by an entomologist from Western Kentucky University.

The study by Dr T. Keith Philips, recently published in the open access journal ZooKeys, provides important insights into the evolution and diversity of these dung beetles, which make up about half of the world’s dung beetle fauna.

The two tribes studied, the onthophagines and oniticellines, evolved from a single common ancestor and are found worldwide, except for Antarctica. These dung beetles make up the vast majority of species and dung beetle biomass in many ecosystems, feeding on mammal dung.

Dung beetles are well known to many people because many species are colorful and active in the daytime. Additionally, many taxa have unusual behaviors, such as making and rolling balls of dung away from a dung pile. Often thought of as nature’s garbage collectors, the important ecosystem service offered by dung beetle helps recycle nutrients, reduces parasites, and can even help seeds germinate.

While the two tribes studied do not have species that create balls, they instead have evolved many other diverse behaviors. This includes species that do not feed on dung but specialize on fungi, carrion, and dead millipedes. Many species that evolved from the same common ancestor even live in close association with termites and ants, where they might be feeding on nest debris.

“This is one of the most important groups of dung beetles that finally has a hypothesis on how they evolved and diversified on earth,” Philips notes. “The evolutionary scenario can now be tested and refined in the future with more data.” Although relatively well known, this group still may have as many as 1,000 undiscovered species left for scientists to document.

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Original source:

Philips TK (2016) Phylogeny of the Oniticellini and Onthophagini dung beetles (Scarabaeidae, Scarabaeinae) from morphological evidence. ZooKeys 579: 9-57. doi: 10.3897/zookeys.579.6183.

Guardian ants: How far does the protection of a plant-ant species to its specific host go?

Seemingly helpless against their much more lively natural enemies, plants have actually come up with a wide range of defences. In the present research, published in the open-access Journal of Hymenoptera Research, Dr. Adriana Sanchez, Universidad del Rosario, Colombia, and Edwin Bellota, Texas A&M University, USA, focus on the mutualistic relationship developed between a specific Neotropical knotweed and an ant species. During a series of ant-exclusion experiments the scientists observed and subsequently reported an aggressive and highly protective behaviour.

In order to assess the extent of protection these plant-ants provide their exclusive host with, the researchers compared the percentage of herbivory between control plants and experimental ones, which had their resident ants removed. The unambiguous results showed a 15-fold increase in the herbivory in the latter group, which kept on growing even further as the time progressed.

Normally, the studied ants patrol their hosts during both day and night at temperatures sometimes as low as 13C. Every time they found a herbivore, they were seen to attack it aggressively by biting and stinging.

“When an ant encountered a caterpillar, a worker approached and detected it with its antennae, and then recruited more workers. Typically more than 10 workers were recruited around the intruder in less than five minutes,” shared their observations the researchers. “Several workers harassed the herbivore by stinging or biting, until it dropped off the plant. The caterpillars usually hung by a silk thread and attempted to move back onto the plant. However, individuals of Pseudomyrmex continued to chase them until they dropped again. This cycle was repeated several times.”

While patrolling, they were noticed to remove any found debris from the top of the leaves. When they failed to find any signs of mosses, fungi or lichens on the sampled saplings, the scientists suggested that the ants not only protect their host from herbivores, but also from various disease-causing agents.

Plant vitality, growth and reproduction are seriously threatened by herbivores such as, in the case of the hereby studied knotweed, Triplaris americana, caterpillars and grasshoppers. Fighting for their life, plants use structural defenses, toxins, digestibility-reducing compounds, or mutualistic relationship with the enemies of their herbivores.

The herein researched Neotropical plant have found its way of survival through becoming the only host to the ant species Pseudomyrmex dendroicus, characterised with remarkable eyes, light brown body and potent venom, injected through a well-developed sting. In its turn, the knotweed shelters their entire colony in its hollow stems while another symbiont, scale insects, feeds them with the sugary sticky liquid it secrets on digesting plant sap.

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Original source:

Sanchez A, Bellota E (2015) Protection against herbivory in the mutualism betweenPseudomyrmex dendroicus (Formicidae) and Triplaris americana(Polygonaceae). Journal of Hymenoptera Research 46: 71-83. doi: 10.3897/JHR.46.5518.