Nature Field Guide
Mexican Long-spined Sea Urchin
- Spanish name
- Erizo de espinas largas
- Scientific name
- Diadema mexicanum
What Do Pico & Tati Think?
Long spines make a striking silhouette. Pico draws the shape from a distance while Tati notices the shelter around it.
Species overview
About the Mexican Long-spined Sea Urchin
Diadema mexicanum is an eastern Pacific urchin associated with rocky lower shores and underwater rocky habitat. Its long spines are easy to notice, but they are a reason to give the animal space. Record what is visible without reaching into crevices or moving rocks.
Identification
Key Features of the Mexican Long-spined Sea Urchin
Long thin spines extending beyond the body
A shelter or opening among rocks may be nearby
A silhouette is a clue, not a complete species identification
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
Draw the spines as lines around a circle. Leave a wide blank border to represent the space you give the living animal.