Eremite: a gathering of the anti-social

Paguristes sp.

Hermit crabs are the original eremites, inhabiting borrowed shells and living seemingly solitary lives. The genus Paguristes is one such group of hermit crabs that is found globally in mostly shallow water. Only a few species from this group are known from deeper waters. The discovery during the SJADES 2018 Expedition of a three centimetre-long Paguristes from 165 metres was therefore noteworthy. Furthermore, the species has bright green eyes and distinct orange banded pincers. It is a new and undescribed species. The expedition’s Indonesian chief scientist (who is also the world authority on this group of hermit crabs) was thrilled by the discovery. This species is only known from ASEAN in deep water off Java, Indonesia.

Sia ferox Giebel, 1861

This species belongs to a group called the Old World Jerusalem crickets which are also related to the giant wetas of New Zealand. Only two species are known from ASEAN. During a collaborative project between scientists from Malaysia and Singapore, Sia ferox was rediscovered in Borneo after an absence of almost a century! Its species name “ferox” means fierce and probably refers to its defensive posture when provoked—having its jaws wide open and hissing menacingly. Very little is known about the natural history of this species except that it is a good digger and that it has solitary habits. This species is only found in ASEAN in Indonesia and Malaysia (Sarawak).

Xylopagurus philippinensis Forest, 1997

Another hermit crab found during the SJADES 2018 Expedition has been tentatively identified as Xylopagurus philippinensis. It was collected from 370 metres of water.

Unlike most hermit crabs, this species uses a hollowed-out twig in place of a shell as a protective covering. An enormous amount of wood is washed into the oceans each year and much of it sinks to the depths.

This wood therefore becomes a major resource for many deep-water animals.

The genus name Xylopagurus includes the ancient Greek word for “wood”, from which the word “xylem” (the water-transporting tissue in plants) also comes from.

If the specimens from the SJADES 2018 Expedition are definitively identified as Xylopagurus philippinensis, they will confirm the presence of this species outside of the Philippines. This species is only known from ASEAN, and only known with certainty from the Philippines.

Venus’s Flower Basket
Euplectella aspergillum Owen, 1841

This species of sponge creates a skeleton made of glass. Scientists have found that the glass fibres made by the sponge have light-transmitting properties that may help to make fibre optic cables more efficient. Pairs of shrimp larvae are able to enter through the fine holes in the sponge’s body. They soon grow too big to leave the sponge, however, and remain inside for the rest of their lives. The shrimps are therefore not quite eremites but coenobites! This rich symbolism of till-death-do-us-part means that this species (and other closely-related species) are sometimes given as wedding gifts. The Venus’s Flower Basket is found only in the ASEAN region in the Philippines.

Sympagurus villosus Lemaitre, 1996

Besides using shells and hollowed-out pieces of wood, hermit crabs sometimes use other protective coverings. Members of the deep-water genus Sympagurus live in association with soft corals and anemones. These associates form pseudoshells around the hermit crab.

During the SJADES 2018 Expedition, a specimen of Sympagurus villosus was collected. In place of a shell, it has a pseudoshell formed by a soft coral (or “zoanthid”) in which to hide. This species is found at depths between 490 and 800 metres.

This species of hermit crab was previously only known from Australia and New Caledonia. Within ASEAN, it is now known from off Java, Indonesia.