Cryptic kelp crab (Pugettia richii)
Source-cited species reference: taxonomy from WoRMS, biology from SeaLifeBase, occurrence map from GBIF, description from Wikipedia.
Pugettia richii, commonly known as cryptic kelp crab, is a species of small crab in the family Epialtidae. It lives among forests of kelp on the Pacific coast of North America. It can also be considered a decorator crab, often attaching small amounts of algae to its exoskeleton.
- Scientific name
- Pugettia richii
- Authority
- Dana, 1851
- Family
- Epialtidae
- Order
- Decapoda
- Maximum length
- 3 cm
- Depth range
- 0–98 m
- Habitat zone
- benthic
- Gbif occurrence records
- 242,218
Classification (WoRMS)
Full classification as recorded by WoRMS: Kingdom: Animalia · Phylum: Arthropoda · Class: Malacostraca · Order: Decapoda · Family: Epialtidae · Genus: Pugettia.
Accepted name: Pugettia richii · Authority: Dana, 1851 · Taxonomic status: accepted · AphiaID: 441490.
Source: World Register of Marine Species (WoRMS) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=441490 (CC BY 4.0). Accessed 2026-09-23.
Biology and life history (SeaLifeBase)
Measured values published by SeaLifeBase for Pugettia richii. Only fields the database actually holds for this species are shown; these are database values, not aquarium guidance.
Maximum length: 3 cm · Depth range: 0–98 m · Habitat zone: benthic · Vulnerability index: 10 of 100.
SeaLifeBase notes: It is found on rocky substrate from the low intertidal to a depth of 98 meters (Ref. 865).
Source: SeaLifeBase species summary (SpecCode 26940) — https://www.sealifebase.se/summary/Pugettia-richii.html (CC BY-NC 3.0 — non-commercial use only). Accessed 2026-09-23.
Distribution and occurrence records (GBIF)
242,218 georeferenced occurrence records for Pugettia richii are published through GBIF from 3 countries or marine areas. The map above plots 35 distinct locations from a sample of 3,000 records, omitting 25 inland records that carry an institution's coordinates rather than a collection site; it shows where the species has been observed and reported, not a modelled range.
Most records by country or area: United States of America (241,917); Canada (289); Mexico (12).
The full country table, WoRMS marine regions and the sampling notes are on this species' Distribution page.
Source: GBIF Occurrence Search (taxonKey 2226675) — https://www.gbif.org/occurrence/search?taxon_key=2226675&has_coordinate=true (records CC0 / CC BY); WoRMS distribution records (MarineRegions) — https://www.marinespecies.org/aphia.php?p=taxdetails&id=441490 (CC BY 4.0); Natural Earth 110m basemap — https://www.naturalearthdata.com/ (public domain). Accessed 2026-09-23.
Description and natural history (Wikipedia)
Pugettia richii is about 3-4 cm in size, and has one sharp lateral tooth protruding from the front of its exoskeleton. The carapace is typically red and its chelae are bright blue near the end with orange, white or red tips. P. richii was found to be the most abundant of five observed spider crab species in a kelp forest off the coast of California, the species included in the study being Loxorhynchus crispatus, Pugettia producta, Mimulus foliatus, P. richii, and Scyra acutifrons. The crab is tiny and difficult to find, living on kelp and on benthic algal mats.
Pugettia richii is found in the rocky intertidal zone from Alaska to North Mexico. It is abundant in kelp forests and rocky reefs climbing the kelp at night. 300–2,100 crabs can be found on one kelp plant, with the numbers peaking at night. The males are typically higher up on the kelp and the females stay near the base of the plants. P. richii larvae were found to be very abundant off the coast of California. Larvae were present in 88.5% of samples taken. It is typically found on the algae Cystoseira and in coralline algal mats.
Pugettia richii is very good at camouflage, as it is a decorator crab. However, it also has the ability to change its color to match different algal growths nearby. Consistent with other crabs in the genus, P. richii typically only decorates its rostrum. It feeds on muscles, clams, barnacles and other hard shelled prey, as well as detritus and drift kelp.
This kelp crab is often preyed on by sea otters. The slow moving kelp crab is easily picked up by the sea otters. The kelp crab's only real defense is its camouflage.
In recent time it is being shown that marine reserves are actually harming these crabs. The reserves are increasing the population of predators resulting in an increase in P. richii mortality of about seven times greater than outside of the reserves.
Source: Wikipedia: Pugettia richii — https://en.wikipedia.org/wiki/Pugettia_richii (CC BY-SA 4.0). Accessed 2026-09-23.
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