#coenobitidae

[snototter]

A Caribbean hermit crab (Coenobita clypeatus) in Indian Key State Park, Florida

by Alan Cressler

[herpsandbirds]

Coconut Crab (Birgus latro), family Coenobitidae, Palmayra Atoll (int he South Pacific)

This “crab” is in the terrestrial hermit crab family.

This is the largest terrestrial arthropod in the world, growing to a weight of up to 4.1 kg (9 lb) and a leg spread of up to 1 m (3 ft 3 in).

photograph by Laura Beauregard

[uncharismatic-fauna]

Uncharismatic Fact of the Day

Although they may not look it, coconut crabs and hermit crabs are closely related! The resemblance is strongest when coconut crabs are young; in their early juvenile stages, their shells are thin and soft, and they use seashells to protect themselves just like a hermit crab.

(Image: A young coconut crab (Birgus latro) with a borrowed shell by Drew Avery)

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[captious-solarian]

Coconut crab on Aldabra, Seychelles. Photo by Joey Latsha-Gamboa, 2024.

[drhoz]

#2813 - Birgus latro - Coconut Crab

AKA robber crab and palm thief. Originally described as Cancer crumenatus in 1705 by Georg Eberhard Rumphius working in what is now Eastern Indonesia, but that was before Linnaeus popularised the binomial naming system. Linnaeus called it Cancer latro.

An enormous hermit crab, with a legspan of up to a meter, and weighing up to 4.1 kg (9 lb). It's range once broadly shadowed that of the coconut palm, from Zanzibar to the Pitcairns, but it is now extinct in most areas with a significant human population, and considered vulnerable elsewhere. Some efforts are being made to protect them.

Juvenile coconut crabs use empty gastropod shells for protection like other hermit crabs, but the adults develop a tough exoskeleton over their previously delicate abdomens. Coconut crabs have evolved branchiostegal lungs, which they use instead of their vestigial gills, and will drown if immersed in water for too long. They also have an acute sense of smell which they use to find fleshy fruits, nuts, seeds, fallen trees, carrion, possibly Amelia Earhart, and other organic matter opportunistically. Anything left unattended will be investigated and may be carried away. Funnily enough, coconuts are not a significant part of its diet, but they can certainly climb up the tree to look for anything easier to eat.

Nov. 1956 Man's Conquest magazine cover art by George Gross. The guy certainly had a theme. Alas the protagonist survived.

The spend most of their time in moist burrows, unless it's very humid or raining, as this helps their lungs to function. Mating occurs on dry land, but the crabs release their fertilized eggs into the sea. The larvae are planktonic for about a month, before settling to the sea floor, entering a gastropod shell and returning to land. Sexual maturity is reached after about 5 years, and they may live another 55. Or even well over a century.

Otago Museum, Dunedin, Aotearoa New Zealand.

[wonder-rooms]

Coconut Crab (Birgus latro), Dictionnaire Universel D'histoire Naturelle (1892) - Charles Dessalines D’Orbigny

[dendroica]

Hermit crabs at Baker Island (via USFWS - Pacific Region)

Photo by USFWS / Dana Schot

Baker Island National Wildlife Refuge, part of the Pacific Remote Islands Marine National Monument, is a tiny ancient atoll that supports a diverse community of marine organisms including seabirds, marine mammals, turtles, fish, plants, corals, and other invertebrates.

Nesting and foraging seabirds dominate the landscape and seascape while sheer isolation and solitude help us see our place in the natural world.

The Pacific Remote Islands National Marine Monument is one of the largest marine conservation areas in the world and protects over 400,000 square miles and seven national wildlife refuges on coral islands, reefs, and atolls.

[natural-reflection]

A very shy Caribbean Hermit Crab, Soldier Crab, West Atlantic Crab, Tree Crab, or Purple Pincher Coenobita clypeatus

Magens Bay, St. Thomas, United States, 2014 Magens Bay