| Pagurus acadianus | |
|---|---|
 | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Malacostraca |
| Order: | Decapoda |
| Suborder: | Pleocyemata |
| Infraorder: | Anomura |
| Family: | Paguridae |
| Genus: | Pagurus |
| Species: | P. acadianus |
| Binomial name | |
| Pagurus acadianus J. E. Benedict, 1901 | |
Pagurus acadianus, the Acadian hermit crab, is a species of hermit crab in the family Paguridae. [1] [2] [3] [4] It is found in Western Atlantic Ocean. [1]
The Acadian hermit crab, also known as Pagurus acadianus, can be found in the Western Atlantic Ocean, including areas such as the Vineyard Sound. [5] In addition, the Acadian hermit crab has been cited as the most abundant species of crab in Salisbury Cove, Maine by William C. Grant, Jr, during his extensive study of hermit crabs populating this area in 1961. [6]
Pagurus acadianus was first identified in scientific literature by scientist J.E. Benedict in 1901. As examined by Morris H. Roberts, Jr.’s, Benedict was able to differentiate this organism from that of a very similar taxa, Pagurus benhardus, due to physical variations. Benedict observed that Pagurus acadianus had larger eyestalks, shorter fingers of the chelae and sharper chelipeds, all of which are necessary identifiers of the Acadian hermit crab. [7] Taxonomically, the Acadian hermit crab belongs to the Arthropoda phyla. Arthropods belong to the most populous animal phylum, with a recorded million (and counting) species. Arthropods include crustaceans and insects, and are characterized by the breadth of their variation in morphology, or their relationship among similar organisms based on comparisons between physical, chemical and taxonomic similarities. This can often be seen through the use of phylogenetic trees and cladograms. The Acadian hermit crab belongs to the Pagurus genera, along with the hairy hermit crab, or Pagurus pubescens, and the aforementioned Pagurus bernhardus . The abundance of their populations is seasonally dependent, with a peak in richness in the month of June, and a staggering decrease from the months of November to March. [5] In addition, they are most plentiful in seawater temperatures ranging from 32 degrees Fahrenheit to 41 degrees Fahrenheit. [8] The Acadian hermit crab has most often been observed in its fossilized state, with 95.4% of occurrences being recorded as preserved specimen. With only 4.4% of occurrences being living organisms, there is much to know about this creature, and whether its ecological niche is similar to that of its common ancestors. [9]
Though very little is known on the specific reproductive behavior of Pagurus acadianus, information on their adolescence was attained by Roberts during his laboratory studies of this species. Roberts found that the incubation period of the larva is approximately 30 days, and the optimal temperature during gestation is 55.4 degrees Fahrenheit. Once they hatch, the size of the eggs is about 0.58 by 0.64 millimeters, and can be distinguished by varying hues of red and yellow coloration, in addition to distinctive eyespots. Both larval and adult Acadian hermit crabs are often confused with the closely related Pagurus berhnardus , or the common marine hermit crab of western Europe, and this comparison has been the focal point of many scientific evaluations, as demonstrated by Benedict's work. [7]
As examined by Jennifer E. Angel in her paper, hermit crabs are known to inhabit different shells throughout their lifetimes, switching from shell to shell as a result of growth. Increased growth means increased shell size, because inhabiting a shell that is too small for the crab's body results in an increase in predation and desiccation. [10] Pagurus acadianus are often found inhabiting the shells of Littorina littorea, Thais lapillus, Buccium undatum, and Polinices heros , as concluded by William C Grant, Jr. Larger individuals are often located on elevated areas within the rocky intertidal, which is defined as the area between the highest high tides and the lowest low tides. [6] This area is one of much scientific exploration, due to its accessibility and the adaptations of the organisms that live there. These organisms have to face daily variation in salinity, exposure to sunlight and lack of food. Small individuals can be found on wharf piling and vertical faces of rock. This area can also be defined as the midway region of the rocky intertidal zone. This species of hermit crab has been observed to be quite aggressive, therefore yielding staggering amounts of both intraspecific and interspecific competition. Smaller individuals have been recorded to be more aggressive and dominant, which may be the result of an adaptation to accommodate for smaller size. [11]
The diet of these organisms, like many other species of hermit crab, includes macroscopic animals and detritus, due to the fact that hermit crabs are classified as omnivorous detritivores. In addition, the bulk of their nutrient intake comes from detritus, classified by many marine scientists as “marine snow”. They consume their food sources through proteolytic enzymes that split carbohydrates and lipids. [12]
Some of the threats to this species include a microbial infection, which is the result of the fungus Fusarium solani . This fungus causes lesions, attack of the dermis, and mixed inflammatory response, therefore reducing the organism's ability to fight off infection. [13] In addition, larval parasitic nematodes, such as Hysterothylacium aduncum, have been reported to infect this species of hermit crab and hosts itself as a parasite within the individual. One to three of these parasitic nematodes were observed per hermit crab by David J. Marcogliese during his study of nematodes of the past of Eastern Canada, and defined Hysterothylacium aduncum as intestinal parasites. [14] Though not much is known on their affect to the organisms with which they inhabit, their position within the gut of their host may be in order to consume the food that the organism has ingested, causing possible starvation to the host. A common invasive species affecting Pagurus acadianus is the Asian shore crab, Hermigraspus sanguineus , which outcompetes many different species of crab as a result of being aggressive interspecific competitors. [15] The introduction of this invasive species was first observed in New Jersey in 1988. In their work, Christopher P. Bloch, Kevin D. Curry, and John C. Jahoda attribute their occurrence to international commerce and global travel. [16]
Acadian hermit crabs have been cited to have two major defense mechanisms: fleeing when approached in the face of predation, or curling up and hiding in their shells. They decide which tactic to use depending on cost–benefit analysis. Like many terrestrial and marine organisms alike, Pagurus acadianus will choose either method depending on the exhaustion of energy or the depleted availability of food during a threat. [17]
Ectosymbiosis is a form of symbiotic behavior in which an organism lives on the body surface of another organism, including internal surfaces such as the lining of the digestive tube and the ducts of glands. The ectosymbiotic species, or ectosymbiont, is generally an immobile organism existing off of biotic substrate through mutualism, commensalism, or parasitism. Ectosymbiosis is found throughout a diverse array of environments and in many different species.
Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (abdomen), usually hidden entirely under the thorax. They live in all the world's oceans, in freshwater, and on land, are generally covered with a thick exoskeleton, and have a single pair of pincers. They first appeared during the Jurassic Period.
Hermit crabs are anomuran decapod crustaceans of the superfamily Paguroidea that have adapted to occupy empty scavenged mollusc shells to protect their fragile exoskeletons. There are over 800 species of hermit crab, most of which possess an asymmetric abdomen concealed by a snug-fitting shell. Hermit crabs' soft (non-calcified) abdominal exoskeleton means they must occupy shelter produced by other organisms or risk being defenseless.
A tide pool or rock pool is a shallow pool of seawater that forms on the rocky intertidal shore. These pools typically range from a few inches to a few feet deep and a few feet across. Many of these pools exist as separate bodies of water only at low tide, as seawater gets trapped when the tide recedes. Tides are caused by the gravitational pull of the sun and moon. A tidal cycle is usually about 25 hours and consists of one or two high tides and two low tides.
Pagurus bernhardus is the common marine hermit crab of Europe's Atlantic coasts. It is sometimes referred to as the common hermit crab or soldier crab. Its carapace reaches 3.5 centimetres (1.4 in) long, and is found in both rocky and sandy areas, from the Arctic waters of Iceland, Svalbard and Russia as far south as southern Portugal, but its range does not extend as far as the Mediterranean Sea. It can be found in pools on the upper shore and at the mean tide level down to a depth of approximately 140 metres (460 ft), with smaller specimens generally found in rock pools around the middle shore and lower shore regions, with larger individuals at depth. P. bernhardus is an omnivorous detritivore that opportunistically scavenges for carrion, and which can also filter feed when necessary.
Coenobita cavipes is a species of land hermit crab native to the eastern parts of Africa, the Indonesia, Philippines, China, Japan, Malaysia, Taiwan, Polynesia, and Micronesia. While these hermit crabs are terrestrial, they prefer to reside near the shores for access of both water and land.
The Jonah crab is a marine brachyuran crab that inhabits waters along the east coast of North America from Newfoundland to Florida. Jonah crabs possess a rounded, rough-edged carapace with small light spots, and robust claws with dark brown-black tips. The maximum reported carapace width for males is 222 mm, while females rarely exceed 150 mm. It is the closest relative to the European brown crab in the Western Atlantic.
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.
Pagurus novizealandiae, or the New Zealand hermit crab is a hermit crab of the family Paguridae, endemic to New Zealand. Its body is up to 16 millimetres (0.63 in) wide.
An epibiont is an organism that lives on the surface of another living organism, called the basibiont. The interaction between the two organisms is called epibiosis. An epibiont is, by definition, harmless to its host. In this sense, the interaction between the two organisms can be considered neutralistic or commensalistic; as opposed to being, for example, parasitic, in which case one organism benefits at the expense of the other, or mutualistic, in which both organisms obtain some explicit benefit from their coexistence. Examples of common epibionts are bacteria, barnacles, remoras, and algae, many of which live on the surfaces of larger marine organisms such as whales, sharks, sea turtles, and mangrove trees.
Pagurus hirsutiusculus is a species of hermit crab, commonly called the hairy hermit crab. It lives from the Bering Strait south to California and Japan, from the intertidal zone to a depth of 110 m (360 ft).
Calcinus elegans, also known as the blue line hermit crab, is a small, tropical hermit crab.
Hematodinium is a genus of dinoflagellates. Species in this genus, such as Hematodinium perezi, the type species, are internal parasites of the hemolymph of crustaceans such as the Atlantic blue crab and Norway lobster. Species in the genus are economically damaging to commercial crab fisheries, including causing bitter crab disease in the large Tanner or snow crab fisheries of the Bering Sea.
Crustaceans may pass through a number of larval and immature stages between hatching from their eggs and reaching their adult form. Each of the stages is separated by a moult, in which the hard exoskeleton is shed to allow the animal to grow. The larvae of crustaceans often bear little resemblance to the adult, and there are still cases where it is not known what larvae will grow into what adults. This is especially true of crustaceans which live as benthic adults, more-so than where the larvae are planktonic, and thereby easily caught.
Calcinus tubularis is a species of hermit crab. It is found in the Mediterranean Sea and around islands in the Atlantic Ocean, where it lives below the intertidal zone. Its carapace, eyestalks and claws are marked with numerous red spots. C. tubularis and its sister species, C. verrilli, are the only hermit crabs known to show sexual dimorphism in shell choice, with males using normal marine gastropod shells, while females use shells of gastropods in the family Vermetidae, which are attached to rocks or other hard substrates.
Pagurus prideaux is a species of hermit crab in the family Paguridae. It is found in shallow waters off the northwest coast of Europe and usually lives symbiotically with the sea anemone Adamsia palliata.
Neanthes fucata is a species of marine polychaete worm in the family Nereididae. It lives in association with a hermit crab such as Pagurus bernhardus. It occurs in the northeastern Atlantic Ocean, the North Sea and the Mediterranean Sea.
Pagurus dalli, commonly known as the whiteknee hermit, is a species of hermit crab in the family Paguridae. It is found in the northeastern Pacific Ocean at depths down to about 276 m (900 ft). It usually lives in a mutualistic symbiosis with a sponge, or sometimes a hydroid.
Hysterothylacium is a genus of parasitic roundworms in the family Raphidascarididae. As of 2020 it consists of over 70 species and is considered one of the largest of the ascaridoid genera parasitising fish.
Nectonema is a genus of marine horsehair worms first described by Addison E. Verrill in 1879. It is the only genus in the family Nectonematidae described by Henry B. Ward in 1892, in the order Nectonematoidea, and in the class Nectonematoida. The genus contains five species; all species have a parasitic larval stage inhabiting crustacean hosts and a free-living adult stage that swims in open water.
Media related to Pagurus acadianus at Wikimedia Commons