Petrolisthes armatus
A small filter-feeding crab that wedged flat beneath rubble and shells in the Marine Shore and Seagrass Meadow, fanning suspended particles from the water with feathery mouthparts; molting and mating were observed in the system, though larvae never survived past the zoea stage, and the species was confirmed extirpated following a gradual decline.
The Green Porcelain Crab was a small, extremely flat-bodied porcelain crab that wedged beneath rubble, shells, and hard structure in the Marine Shore and Seagrass Meadow, filter feeding from crevice edges by sweeping suspended particles from the water with modified feathery mouthparts. A population of approximately twelve individuals was present following introduction in July 2024, and mating was directly observed in December 2024 immediately following a molt, but larvae never survived past the zoea stage. Following a gradual decline over several weeks, the species is confirmed extirpated from miniBIOTA as of July 2, 2026.
Petrolisthes armatus is a small porcellanid crab native to the Indo-Pacific that is now widely established in the Gulf of Mexico, Caribbean, and Atlantic coast of Florida, where it arrived via ballast water or the marine aquarium trade. It occupies the shallow intertidal and subtidal zones among rubble, shells, coral fragments, dead coral heads, and other hard structure, using its flattened body to wedge tightly into crevices that exclude larger predators. Adults typically reach 1.5 to 2 centimeters in body length.
The species is a suspension feeder, using highly modified third maxillipeds that fan out into feathery paddles to sweep fine suspended particles from the water column. These feeding fans are extended from the crevice edge and retracted when disturbed. The diet includes phytoplankton, zooplankton, fine detritus, and suspended organic particles. Petrolisthes armatus can also capture small items with its chelae. When threatened, it autotomizes (willingly drops) its claws, which regenerate over successive molts.
Reproduction is sexual. Females brood eggs attached beneath the abdomen until hatching. Released larvae are free-swimming planktotrophic zoea that require suitable suspended food and eventually a hard settlement substrate to complete metamorphosis. In closed systems, the zoea stage is a persistent bottleneck: larvae are released but typically cannot find appropriate food resources or settlement cues at the scale available to them in a self-contained habitat.
While present, the Green Porcelain Crab occupied the suspension-feeder guild in the Marine Shore and Seagrass Meadow, removing phytoplankton, fine detritus, and organic particles from the water column and channeling that production into the animal food web. Its flat body form and crevice-dependent lifestyle also made it a structural specialist, relying on available hard substrate and rubble for shelter and feeding access.
The Green Porcelain Crab had been flagged in the Daggerblade Grass Shrimp dossier as a possible predator of mysis larvae, which have not survived past early larval stages in that species. This predation was never directly observed, and with the Green Porcelain Crab now extirpated, it is no longer a viable explanation for the grass shrimp's failed larval recruitment.
With no observed juvenile recruitment across the population's history, the species never resolved the same closed-system bottleneck documented elsewhere in miniBIOTA: adults persisted, reproduced, and released larvae, but the system did not support larval survival past the zoea stage. The population then declined gradually over several weeks and was confirmed extirpated July 2, 2026.
Green Porcelain Crabs were introduced on July 28, 2024. No dedicated observation record exists for the introduction event.
December 17, 2024: A molt was observed and captured on video at the final moment of exoskeleton shedding. Immediately upon completing the molt, a second crab copulated with the freshly molted individual for approximately 10 to 15 seconds. A third crab also attempted to reach the freshly molted crab. The freshly molted individual appeared vulnerable and attempted to move away. This is the only archived observation for the species.
Early records: Egg-carrying, zoea release, and night observations are referenced in the species record, likely originating from before the current observation format was established. Larvae are noted to have reached the zoea stage but not survived past it.
July 2, 2026: Following several weeks of repeated observation with no individuals located, the Green Porcelain Crab is confirmed extirpated from the Seagrass Meadow and from miniBIOTA. The decline was gradual and began before the June 2026 wave system strengthening, weakening water movement as a candidate cause. Individuals were introduced as adults or near-adults in July 2024; natural senescence, food limitation, and other unmeasured environmental factors are candidate explanations, none confirmed.
The population of approximately 12 individuals, present since July 2024, declined gradually over several weeks and was confirmed extirpated from the Seagrass Meadow and from miniBIOTA on July 2, 2026. The decline began before the June 2026 wave system strengthening, making that change an unlikely cause. Candidate explanations include natural senescence (individuals were introduced as adults or near-adults and had persisted nearly two years), food limitation, or other unmeasured environmental factors; none confirmed. The species never achieved successful larval recruitment past the zoea stage in miniBIOTA.
While present, the Green Porcelain Crab filtered suspended phytoplankton, zooplankton, fine detritus, and organic particles from the water column using highly modified third maxillipeds that function as feathery sweeping fans. No direct feeding events were archived in miniBIOTA; filter feeding was inferred from the species' known biology and was consistent with the extended fan mouthparts visible in December 2024 video. The species had also been flagged as a possible predator of Daggerblade Grass Shrimp mysis larvae; this predation was never directly observed, and the hypothesis is now moot following the species' extirpation.
Broadly tolerant of intertidal fluctuations in temperature, salinity, and dissolved oxygen. In miniBIOTA, adults have persisted since July 2024, indicating tolerance of the system's conditions. Salinity stability is the primary requirement; the species cannot tolerate freshwater dilution.
Adults reproduced in miniBIOTA; egg-carrying and zoea release were referenced in early species records. Molting with immediate copulation was directly observed December 17, 2024. Larvae reached the zoea stage but never survived to settlement; the cause was unresolved, with insufficient larval food or settlement cues in a closed system as the likely constraint.
Was a suspension filter feeder in the marine saltwater habitats of miniBIOTA. The population held at approximately 12 adults from introduction in July 2024 until a gradual decline beginning sometime before June 2026; larvae reached the zoea stage but never survived to settlement, limiting long-term population recovery. Confirmed extirpated July 2, 2026.
Follow this species across the habitats where it currently appears in the miniBIOTA biosphere.
