Long-claw Hermit Crab

The Long-armed Hermit Crab (Pagurus longicarpus) is a small saltwater hermit crab recorded in miniBIOTA's Seagrass Meadow. A single December 15, 2024 observation documents Long-armed Hermit Crab and McLaughlin's Hermit Crab together in the Seagrass Meadow, engaging in chase and clamp behavior consistent with shell competition. Long-armed Hermit Crab is the primary routing species for that observation. No introduction date or population count is on record. Species-level identification is assessed as Possible; the common name and scientific name reflect existing miniBIOTA records, but no morphological confirmation is documented.

Name note: The common name "Long-armed Hermit Crab" and the scientific name longicarpus (Latin: "long wrist/arm") both refer to the distinctive elongated right cheliped that characterizes this species. The elongated claw is used for blocking the shell entrance when the crab retracts -- a defensive posture -- rather than for feeding or prey capture.

Range and Florida Relevance

Pagurus longicarpus is one of the most abundant and widespread small hermit crabs in the western Atlantic, ranging from Nova Scotia south to Colombia. It is common throughout Florida's coastal waters on both the Atlantic and Gulf coasts, found in shallow marine and estuarine habitats from rocky intertidal zones to sandy and muddy subtidal bottoms. In Florida, it is frequently encountered in seagrass beds, tidal flats, and shallow bays and is often the most numerically dominant hermit crab in nearshore marine habitats. It belongs to family Paguridae (right-handed hermit crabs), where the right cheliped is larger than the left.

Habitat

Long-armed Hermit Crabs occupy shallow coastal marine and estuarine habitats. They are found on sandy and muddy substrate, in seagrass beds, on rocky and shell-covered bottoms, and in the debris zones of tidal flats. They tolerate a broad range of salinity and temperature conditions consistent with their wide range from Nova Scotia to the Caribbean. In miniBIOTA, this species is associated with the Seagrass Meadow.

Diet

Pagurus longicarpus is an omnivorous scavenger. It feeds on algae, biofilm, detritus, carrion, small invertebrates, and organic particles scraped or gathered from substrate surfaces. The elongated right cheliped is not a feeding tool; it functions as a defensive plug blocking the shell entrance when the crab is threatened. Feeding is opportunistic and generalist.

Shell Use

Like all Paguridae, P. longicarpus carries an empty gastropod shell for protection of its soft abdomen. As the crab grows it must acquire progressively larger shells. Shell acquisition can involve competition with other hermit crabs, including chasing, grappling, and attempting to evict the occupant. On December 15, 2024, Long-armed Hermit Crab and McLaughlin's Hermit Crab were both observed in the Seagrass Meadow engaging in chase and clamp behavior in which one grabbed the other's leg and held or carried them briefly. No physical damage was noted and the behavior was interpreted as probable shell competition or mating activity.

Reproduction

Pagurus longicarpus reproduces sexually. Females brood fertilized eggs attached to the pleopods on the soft abdomen, held within the gastropod shell until hatching. Larvae (zoea and megalopa stages) are released into the water column, where they develop before settling and acquiring a first shell. Sex determination requires examination of pleopods, which are concealed within the shell. No reproductive observations have been made in miniBIOTA.

Tolerance Ranges

Pagurus longicarpus is a broadly tolerant species adapted to the wide range of conditions in its geographic range -- from cold-temperate New England to tropical Caribbean waters. It tolerates considerable salinity variation and temperature swings. No miniBIOTA-specific tolerance measurements are on record.

The Long-armed Hermit Crab functions as a saltwater scavenger and algae grazer in the Seagrass Meadow. By consuming algae, biofilm, detritus, and organic particles, it contributes to substrate cleaning and nutrient cycling. Shell competition with McLaughlin's Hermit Crab suggests both species share the Seagrass Meadow and compete for shell resources.

No confirmed predators are documented in miniBIOTA. In natural settings, hermit crabs of this size class are prey for predatory fish, octopus, wading birds, and larger crabs. Empty shells become available to other hermit crabs after P. longicarpus grows out of them or abandons them.

Introduction

No introduction date or source is on record for Long-armed Hermit Crab. The earliest documented appearance in the miniBIOTA archive is December 15, 2024.