''Pagurus longicarpus'', the long-wristed hermit crab, is a common hermit crab found along the Atlantic and Gulf coasts of the United States and the Atlantic coast of Canada.Young, A. M. 1978. Desiccation tolerances for three hermit crab species Clibanarius vittatus (Bosc), Pagurus pollicaris Say and P. longicarpus Say (Decapoda, Anomura) in the North Inlet Estuary, South Carolina, U.S.A. Estuar. Coast. Mar. Sci. 6: 117–122.

Description

This species of hermit crab can reach a shell length of up to half an inch in size. ''P. longicarpus'' coloration can vary, but body color is most commonly gray, green or white. The right claw of ''P. longicarpus'' is much larger than the left, and each claw has a tan or gray stripe down the middle. The long-wristed hermit crab inhabits the empty shells of

gastropods The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. Ther ...

such as periwinkles,

snail A snail is, in loose terms, a shelled gastropod. The name is most often applied to land snails, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of the members of the molluscan class Gastro ...

s, and

slug Slug, or land slug, is a common name for any apparently shell-less terrestrial gastropod mollusc. The word ''slug'' is also often used as part of the common name of any gastropod mollusc that has no shell, a very reduced shell, or only a smal ...

s for mobile shelter and protection of their soft abdomens. They anchor themselves into the shells by wrapping their abdomens around the

columella Lucius Junius Moderatus Columella (; Arabic: , 4 – ) was a prominent writer on agriculture in the Roman Empire. His ' in twelve volumes has been completely preserved and forms an important source on Roman agriculture, together with the wo ...

, or axis, inside the vacant shell.Allee, W., & Douglas, M. (1945). A Dominance Order in the Hermit Crab, Pagurus longicarpus Say. Ecology, 26(4), 411-412. Hermit crabs cannot produce their own shells, and therefore must scavenge for abandoned ones.Carlon, D., & Ebersole, J. (1995). Life-History Variation among Three Temperate Hermit Crabs: The Importance of Size in Reproductive Strategies. Biological Bulletin, 188(3), 329-337.Gilliand, S., Pechenik, JA. (2018). Temperature and Salinity Effects on Shell Selection by the Hermit Crab Pagurus longicarpus. Biological Bulletin, 235(3), 178-184.Rotjan, R., Blum, J., & Lewis, S. (2004). Shell Choice in Pagurus longicarpus Hermit Crabs: Does Predation Threat Influence Shell Selection Behavior? Behavioral Ecology and Sociobiology, 56(2), 171-176. Shell selection plays many crucial roles in ''P. longicarpus'', such as providing protection from predators,

desiccation Desiccation () is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic (attracts and holds water) substance that induces or sustains such a state in its local vicinity in a moderately sealed container. ...

and

salinity Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal ...

stress, as well as influencing competition, population size, and reproductive behaviors in the species. Pagurus longicarpus-naked.jpg, A crab out of a shell

Distribution and habitat

''Pagurus longicarpus'' is commonly found along the Atlantic coast of Canada and the United States, from Nova Scotia to Northeastern Florida, as well as along the Gulf coast of the United States to Texas. These hermit crabs can be found in

intertidal The intertidal zone, also known as the foreshore, is the area above water level at low tide and underwater at high tide (in other words, the area within the tidal range). This area can include several types of Marine habitat, habitats with var ...

and

subtidal The neritic zone (or sublittoral zone) is the relatively shallow part of the ocean above the drop-off of the continental shelf, approximately in depth. From the point of view of marine biology it forms a relatively stable and well-illuminated ...

Atlantic environments on a variety of substrates and at depths of up to 200 meters.McDermott, J. J. (1999). Reproduction in the hermit crab Pagurus longicarpus (Decapoda: Anomura) from the coast of New Jersey. J. Crustac. Biol. 19: 612–621. Most commonly, ''P. longicarpus'' is found in shallow tidal pools during the months of April to October, and in deeper and warmer waters during the fall and winter months. ''P. longicarpus'' faces extreme temperature and salinity fluctuations while inhabiting tidal pools due to the rising and falling tides, as well as changing climate. On hot, sunny days, there is often a rapid increase in tidal pool temperature and salinity, whereas on cooler, rainier days, salinity and temperature can rapidly decrease. Rising tides can also alter tidal pool conditions to those of the surrounding ocean. Due to these harsh living conditions, ''P. longicarpus'' depends heavily on its shell to cope with changing conditions. These fluctuating conditions can also impact shell selection in the species and determine species distribution within intertidal and subtidal regions. According to Neumann, Knebelsberger, Barco and Haslob (2022), ''P. longicarpus'' has become established in the North Frisian

Wadden Sea The Wadden Sea ( nl, Waddenzee ; german: Wattenmeer; nds, Wattensee or ; da, Vadehavet; fy, Waadsee, longname=yes; frr, di Heef) is an intertidal zone in the southeastern part of the North Sea. It lies between the coast of northwestern conti ...

. This may have occurred due to trans-Atlantic transport of larvae in ballast water.

Diet and predation

Long-wristed hermit crabs are scavenger feeders with a broad diet consisting of

detritus In biology, detritus () is dead particulate organic material, as distinguished from dissolved organic material. Detritus typically includes the bodies or fragments of bodies of dead organisms, and fecal material. Detritus typically hosts commun ...

, organic material found in ocean surface foam, microcrustaceans and

algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...

. Feeding is performed by scooping sand or other substrate with the chelipeds, ripping and tearing food, and then passing it to the mouth for consumption. The major predators of ''P. longicarpus'' include birds, fish, snails, octopuses and other crabs, including the

green crab ''Carcinus maenas'' is a common littoral crab. It is known by different names around the world. In the British Isles, it is generally referred to as the shore crab, or green shore crab. In North America and South Africa, it bears the name europ ...

. Hermit crab shells are crucial for protection and minimizing predation, and therefore proper shell selection is vital. ''P. longicarpus'' will avoid selecting shells with extensive damage because they are more vulnerable to predation. The most common type of damage to hermit crab shells is the presence of small holes. These holes are caused by the drilling of nacticid gastropods in order to prey on the original gastropod hosts of the shell.

Behavior

Intraspecific competition within this species is very common and is most often triggered by lack of resources.Gherardi, F. (2006). Fighting Behavior in Hermit Crabs: The Combined Effect of Resource-Holding Potential and Resource Value in Pagurus longicarpus. Behavioral Ecology and Sociobiology, 59(4), 500-510. One of the most important limited resources to hermit crabs is their shell, which is key to their survival and reproductive success. Finding an appropriately sized shell is valuable for ''P. longicarpus''. From an energetic standpoint, if a shell is too large, crabs will extend unnecessary energy carrying and maneuvering it. Alternatively, if the shell is too small, they could suffer from increased predation and desiccation. Shell selection also plays a role in reproductive success in ''P. longicarpus.'' Reproductive success is positively correlated with a larger shell size, and the rate of growth of the crabs can be stimulated by inhabiting larger shells. ''P. longicarpus'' also will not feed unless housed in the proper sized shell, ultimately leading to starvation and death. Each of the consequences of incorrect shell size places a strong selective pressure on obtaining the perfect shell, which often results in aggressive and competitive interactions within the species. In addition to fighting over mates and food, ''P. longicarpus'' will fight over shells. Larger crabs or crabs with less suitable shells will often forcibly remove other crabs with more desirable shells by clasping the

chelae A chela ()also called a claw, nipper, or pinceris a pincer (biology), pincer-like organ at the end of certain limbs of some arthropods. The name comes from Ancient Greek , through New Latin '. The plural form is chelae. Legs bearing a chela are ...

, or legs, of the occupant with its pincers, which allows them to takeover the desired shell. Along with predation, shell availability is a major factor in determining ''P. longicarpus'' population size.

Reproduction

''P. longicarpus'' breeding season occurs from late March until October with the peak breeding in April. The main period of reproduction in the species occurs during the spring. Male hermit crabs will compete with other males for available females during breeding season. ''P. longicarpus'', like many crustaceans, performs precopulatory mate-guarding behaviors, where males will grasp ahold of the female’s shell once the female releases a

pheromone A pheromone () is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavio ...

signaling sexual maturity. Male and female crabs can be differentiated based on their

pleopod The decapod ( crustaceans such as a crab, lobster, shrimp or prawn) is made up of 20 body segments grouped into two main body parts: the cephalothorax and the pleon (abdomen). Each segment may possess one pair of appendages, although in various ...

morphology. Males have two pleopods, while females have three branching pleopods where her eggs are attached.Johnson, R., & Ebersole, J. (1989). Seasonality in the Reproduction of the Hermit Crab Pagurus longicarpus Say, 1817 (Decapoda, Paguridea). Crustaceana, 57(3), 311-313. ''P. longicarpus'' have sexual internal fertilization and must exit their shells in order to mate. After fertilization, the female houses the eggs inside her shell where they grow and develop. Larvae are later released into the surrounding ocean where they undergo several

plankton Plankton are the diverse collection of organisms found in Hydrosphere, water (or atmosphere, air) that are unable to propel themselves against a Ocean current, current (or wind). The individual organisms constituting plankton are called plankt ...

ic growth stages before developing into adult hermit crabs.

References

External links

MBL Marine Organisms Database page
{{Taxonbar, from=Q3933227 Hermit crabs Crustaceans of the Atlantic Ocean Crustaceans described in 1817