Nature Field Guide
Pencil Sea Urchin
- Spanish name
- Erizo lapicero
- Scientific name
- Eucidaris thouarsii
What Do Pico & Tati Think?
Why do some spines look more like pencils than needles? Pico and Tati compare photographs before trying to name an urchin.
Species overview
About the Pencil Sea Urchin
Eucidaris thouarsii is an eastern Pacific pencil urchin. Its stout primary spines contrast with the fine needle-like spines of some other urchins. Related pencil urchins have similar appearances, making a correctly labeled reference image especially important.
Identification
Key Features of the Pencil Sea Urchin
Thick pencil-like primary spines
A compact body among the spines
Compare with Eucidaris thouarsii, not an unlabeled aquarium photograph
Habitat & range
Suitable underwater coastal habitat. Use a permitted guided snorkeling or viewing activity appropriate to your family; do not enter the sea just to find this animal.
Local observations
Documented in Guanacaste. Also recorded at Isla del Coco (Oceanic Pacific); the museum checklist uses Ophiocoma alexandri for Ophiocomella alexandri. Also documented in surveyed Osa Conservation Area reefs. Region tags represent documented locations, not an exhaustive range or a promise of occurrence at every beach. Additional regional assignments require locality evidence.
When to observe
Visibility depends on the site, conditions and the animal. Ask a local guide about an appropriate visit; no fixed encounter season is promised.
Conservation & care
Watch without touching, lifting, feeding or collecting. Keep fingers and equipment away from spines and other surface structures. Leave the animal submerged and its habitat undisturbed.
Observation activity
Make two paper drawings: thick spines and thin spines. Which visible features would you record during a real observation?