Breeding the Rusty Guard Crab (Trapezia ferruginea)
Trapezia ferruginea is a coral guard crab that lives in obligate symbiosis with Pocillopora, defending its host against predators. It broods eggs and releases planktonic larvae, so home breeding is not achievable.
Overview
Trapezia ferruginea is a coral guard crab of the family Trapeziidae that lives in obligate association with Pocillopora corals. Like other Trapezia, it feeds on coral tissue and mucus and grazes polyp-tip lipids, while defending its host from corallivores such as the crown-of-thorns seastar Acanthaster planci. Field studies show corals are attacked far more often once guard crabs are removed.
Sexing
A single mating pair of a given Trapezia species typically occupies each coral colony, so a resident male-female pair on one coral head is the practical indicator of sexes. Females are recognized by a brooded egg mass carried under the abdomen.
Conditioning
A healthy Pocillopora host providing mucus and lipids is the natural conditioning environment for a resident pair. No documented protocol reliably induces or completes reproduction in a home reef, because the larvae are planktonic and cannot be reared in a closed display.
Breeding Setup
No practical home breeding setup exists. A resident pair may produce broods on the host coral, but the female releases planktonic larvae into the water column that require open-water plankton and stable parameters not available in a closed system.
Spawning & Larvae
Fertilized eggs are brooded by the female and hatch into planktonic zoea larvae that develop through successive molts before settling, after which juveniles must locate a suitable host coral. This planktonic development combined with obligate host dependence makes captive rearing impractical.
Common Challenges
- Planktonic larvae are removed by filtration and skimming.
- Larvae require continuous planktonic food through multiple stages.
- Settling juveniles must find a compatible host coral.
- Only one pair occupies a coral head, limiting stocking.