Breeding the Halloween Hermit Crab (Calcinus elegans)

Calcinus elegans is an Indo-Pacific hermit crab that lives in gastropod shells. Females carry eggs that hatch into planktonic zoea larvae, so the species is not bred in home reef tanks.

Overview

Calcinus elegans (H. Milne-Edwards, 1836) is a hermit crab of the Indo-West Pacific, ranging from eastern Africa to islands south of Hawaii in shallow tidal and subtidal zones at 0-20 m. It is a nocturnal omnivorous detritivore that scavenges detritus and decaying plant and animal matter. Like all hermit crabs it occupies empty gastropod shells, preferring dog whelk shells and swapping shells as it grows.

Sexing

Hermit crab sex is determined by gonopores on the leg bases, which is difficult to check inside an occupied shell. During courtship males of Calcinus elegans rotate the female's shell and rub their claws around the shell opening; notably, this species does not perform a shell exchange during mating.

Spawning & Larvae

After mating the female carries fertilized eggs attached to her abdomen inside the shell until they hatch. The larvae emerge as planktonic zoeae that drift and feed in the water column, passing through several zoeal stages and a glaucothoe (post-larval) stage before finding a first shell and settling as juveniles.

Common Challenges

• Planktonic zoeae are drawn into skimmers, filters and pumps in a closed system.
• Larvae require live planktonic food and stable rearing conditions not available in a display.
• Newly settled juveniles need a supply of tiny empty shells, which a tank rarely provides.
• The multi-stage larval cycle through zoeae and a glaucothoe is impractical to support at home.