Urchin Shrimp

Geographical Origin and Habitat: Circumtropical distribution, found in tropical waters of the Western Atlantic, Caribbean, Indian Ocean, and Western Pacific. Settles in lagoons and reefs, associated with shallow urchins.

Taxonomy: Member of the family Gnathophyllidae. Features a robust, compressed body with short legs ending in modified claw-like dactyli to grip calcite spines. Reaches only 1-1.5 cm.

Social Behavior: Obligate commensal. spends its entire life walking along the spines of sea urchins (particularly Tripneustes ventricosus or Diadema antillarum), blending in perfectly.

Coloration and Sexual Dimorphism: Body decorated with longitudinal stripes of black, dark brown, or yellow mimicking the pattern of the host urchin. Females are slightly larger than males.

Tank Setup: Requires an established, mature reef aquarium. The presence of suitable host sea urchins (Tripneustes or Diadema) is absolutely essential to sustain this tiny shrimp in captivity.

Diet and Feeding: Specialized commensal. Feeds mainly on host epithelial tissue, mucus, and organic detritus on the spines. Very difficult to target feed artificially without a host.

Water Quality: Stable reef parameters. Salinity SG 1.023-1.025, pH 8.1-8.4, temperature 22-28°C. Strictly zero copper levels. Highly sensitive to physical or chemical shocks.

Compatibility and Tankmates: Completely peaceful. Keep only with peaceful fish and corals. Avoid predatory or curious fish (e.g. wrasses, hawkfish, puffers) that might pick at the urchin spines.

Aquarium Breeding: Females carry eggs under their abdomen. Planktonic larval stages are highly delicate and do not survive standard home aquarium filtration systems.

Risks and Diseases: Fast decline and death if the host sea urchin dies or suffers from spine loss. Highly sensitive to copper treatments and salinity shock.