Breeding the Polka Dot Hermit Crab (Calcinus tibicen)
Calcinus tibicen is a western-Atlantic hermit crab whose females brood many eggs that hatch into planktonic zoea larvae. Dependent on empty shells and plankton, it is not bred in home reef tanks.
Overview
Calcinus tibicen is a hermit crab widely distributed in the western Atlantic, from the United States and Gulf of Mexico through Bermuda, Florida, the Caribbean, Colombia, Panama and Venezuela to southern Brazil. It is an intertidal-to-shelf species occurring from the lower intertidal down to about 200 m. Semi-gregarious, it occupies empty gastropod shells and works the reef as a cleanup grazer.
Sexing
Sex is determined by gonopores at the leg bases, awkward to view inside an occupied shell. Females become obvious when ovigerous, brooding eggs on the abdomen; the egg count per female is large and varies widely with body size, attributed to multiple or fragmented spawnings across the reproductive cycle.
Spawning & Larvae
The female broods fertilized eggs on her abdomen inside the shell until hatching. As in hermit crabs generally, the nauplius and protozoea stages pass within the egg, and the larvae hatch at the zoea stage; the planktonic zoeae then feed and develop in the water column before a post-larval stage settles and takes a first shell.
Common Challenges
- Planktonic zoeae are captured by skimmers, filters and pump intakes in a closed system.
- Larvae need live planktonic food and steady water parameters a display cannot offer.
- Newly settled crabs depend on a supply of small empty shells.
- Variable, fragmented spawnings make timed larval collection unreliable in captivity.