Petrolisthes armatus

(Gibbes, 1850)

Green Porcelain Crab

Petrolisthes armatus, commonly known as the green porcelain crab, is a small porcellanid crab to the southwestern Atlantic, particularly Brazil. The has established along the southeastern United States coast, where can exceed 30,000 individuals per square meter. Genetic studies confirm it as a single species with exceptional geographic range spanning the Atlantic and eastern Pacific. It is frequently parasitized by the bopyrid isopod Aporobopyrus curtatus, which causes .

Petrolisthes armatus by (c) Pam Kleinsasser, some rights reserved (CC BY), uploaded by Pam Kleinsasser. Used under a CC-BY license.

Petrolisthes armatus Texas PWD by Texas PWD (Brenda Bowler). Used under a CC BY-SA 4.0 license.

Pronunciation

How to pronounce Petrolisthes armatus: //ˌpɛt.rəˈlɪs.θiːz ɑːrˈmɑː.təs//

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Identification

Small crab with oval, granulated bearing shallow narrow ridges and bluntly pointed . Two long chelipeds with distinctive orange spot on visible when parted. Chelipeds composed of four rather than five. Three pairs of legs plus fourth pair. with on first segment, positioned outside stalked (diagnostic for porcelain crabs, contrasting with true crabs where antennae are between eyes). Body length 6–8 mm, weight approximately 0.5 g. Color generally or dark olive-green; paler and mottled. Mouthparts sometimes bright ; entire animal occasionally bright blue.

Images

Habitat

Lower intertidal zone to shallow subtidal zone. Found on rock rubble, oyster , soft sediments, and mangrove . in southeastern United States particularly abundant on oyster reefs and intertidal hard substrates.

Distribution

range: southwestern Atlantic, believed to be Brazil. Established : southeastern United States (Florida, Georgia, South Carolina), tropical west Africa, Ascension Island, Bermuda, Bahamas, Caribbean Sea, Gulf of Mexico, West Indies, tropical Atlantic coast of South America. Eastern Pacific: Baja California to Peru, including Panama (present since 1859, pre-dating Panama Canal).

Diet

Primarily a , using large feathery mouthparts to capture zooplankton. Also scavenges on animal remains on the seabed. Has been observed forming symbiotic relationships with sponges, positioning itself to intercept food particles from the sponge's water current.

Host Associations

Aporobopyrus curtatus - Bopyrid isopod parasitizing branchial chamber; causes ; up to 17% with up to six isopods per ; negative correlation between size and host size suggests impaired host growth

Life Cycle

Females store until mature, then retain fertilized eggs under tail flap aerated by pleopods until hatching. are planktonic with two zoeal stages and one megalopal stage. Larval settlement possibly cued by from other . Females may reach sexual maturity at 3 mm body length. Vertical larval movement plays significant role in estuarine transport and retention.

Behavior

Uses achromatic visual cues for gaze stabilization; does not use angle of linearly polarized light for this purpose. When symbiotic with sponges, positions body to exploit 's water current for feeding.

Ecological Role

and scavenger in intertidal and shallow subtidal . in southeastern United States compete with and may impact shellfish production on oyster . High alter local community structure. - dynamics with Aporobopyrus curtatus affect population structure through .

Human Relevance

Considered in southeastern United States due to dramatic increases and competition with fauna. Concern regarding impacts on oyster shellfish production. Likely spread via ballast water transport of and aquaculture seeding of shellfish beds.