Squat lobster
Squat lobster | |
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Munidopsis serricornis (Galatheidae) | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Arthropoda |
Class: | Malacostraca |
Order: | Decapoda |
Suborder: | Pleocyemata |
(unranked): | Reptantia |
Infraorder: | Anomura |
Groups included | |
Cladistically included but traditionally excluded taxa | |
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Squat lobsters are dorsoventrally flattened
Description
The two main groups of squat lobsters share most features of their morphology. They resemble true
The cephalothorax is made of 19 body segments (somites), although the divisions are not obvious and are most easily inferred from the paired appendages. From front to back, these are the two pairs of
The mouthparts consist of six pairs of appendages— three posterior cephalic appendages and the first three pairs of thoracic appendages.[2] While their function was traditionally believed to be limited to food handling, the mouthparts have a more complex movement pattern that allows them to perform a variety of functions such as prey- and sediment-gathering, sediment transfer, and sediment sorting/particle rejection.[4] In Munida Sarsi, the farther the mouthparts are located from the mouth, the more complex in movement and functional scheme they are.[4]
The most conspicuous appendages are the pereiopods, and the largest of these is the first pair. These each end in a chela (claw), and are therefore known as the "chelipeds"; they can be more than six times the body length, although some groups show sexual dimorphism, with females having proportionally shorter chelipeds.[2] The following three pairs of pereiopods are somewhat smaller than the chelipeds and are without claws, but are otherwise similar; they are used for walking. The fifth pair of pereiopods are much smaller than the preceding pairs, and are held inconspicuously under the carapace. They each end in a tiny chela, and are generally believed to be used for cleaning the body, especially the gills, which are in a cavity protected by the carapace.[2]
The pleon is made up of six somites, each bearing a pair of
Carcinisation has previously been explored in regards to outer morphology; however, the external change in body shaped has influence on the internal anatomical features as well. The use of micro-computer tomography and 3D reconstruction have brought to light anatomical disparity within Galatheoidea.[3] Differences have been found in the ventral vessel system between porcelain crabs and squat lobsters. Carcinisation is also responsible for the loss of the caridoid escape reaction which caused a shift in gonads and the pleonal neuromeres for squat lobsters.[3]
Development
Fecundity or number of eggs increases with smaller sized eggs and increasing body size of the parent. This results in increasing incubation time and consequently, increased egg volume.[5] The trend of larger numbers of eggs and smaller sized eggs is mostly found in lower latitudes and cooler temperatures in order to accommodate for the longer incubation time.[6]
The development period of the embryo consists of five distinct stages in which the lasts several months. Throughout the five stages, both the diameter and volume of the egg increases. In the first stage of
Ecology and behavior
Aggregation and migration
Benthic aggregation
Squat lobster aggregation is theorized to be proportional to the amount of available organic particulate carbon reaching the seafloor.
Squat lobster species found on seamounts typically have smaller bodies with shorter larval stages, as opposed to rise and ridge habitats. It has been suggested that this is due to the difference in substrates at these habitats.[8]
In March 2022 it was reported that a squat lobster, possibly from the genus Munidopsis, had been filmed on the wreck of the Endurance, which sank in 1915 in the Antarctic. This was the first record of a living squat lobster in the Weddell Sea.[10]
Ontogenetic migrations and pelagic aggregation
Munida gregaria form aggregations in warm summer waters of the Pacific Ocean associated with river plume fronts, headland fronts, and shallow internal waves. Density of these aggregations are, on average, 2700 individuals per cubic meter. M. gregaria are able to aggregate in the pelagic region due to a number of unique features as compared to benthic squat lobsters, including fast swimming speeds, reduced density, reduced sinking rates as a result of greater morphological surface area, and optimized aerobic metabolism. M. gregaria also exhibit ontogenetic migration through larvae accumulation in highly productive nearshore waters, which then move toward the mid-continental shelf as they mature, and move completely offshore around full maturation.[6]
In 2020, a study of squat lobsters determined that these crustaceans are far more diverse than previously thought. Through this study, 16 new species within the Leiogalathea genera were described. It was also revealed that diversity of squat lobsters in the Atlantic Ocean is relatively poor in comparison with the Pacific Ocean.[11]
Claw position behavior
In a resting posture, squat lobsters rest their claws on the substrate in front of them. E. picta were observed most frequently in all conditions with their claws extended into the water column, perpendicular to the substrate. In the case of this study, the behavior was thought to be an avoidance response to the surveillance submersible, hence why this behavior was so often observed. In general, it is thought that this behavior may be a mechanism to increase the perceived size of the squat lobster as an aggressive or perhaps illusory display to ward off predators, as well as an active "fishing" strategy to catch prey.[9]
Aggression and agonistic behavior
While squat lobsters look like true lobsters, they are more closely related to hermit crabs. Instead of carrying shells on their backs, they squeeze their bodies into crevices and leave their claws exposed to defend themselves from predators or other squat lobsters.[1]
Squat lobsters are generally unaggressive toward each other, but instances can occur in particular scenarios. Individuals among dense populations will make decisions about whether to hunt for food or engage in deposit feeding on the basis of minimizing aggressive interactions.
Feeding
Squat lobsters feed on a variety of foods, with some species
Breeding
Squat lobsters, in particular
Fisheries
Flesh from these animals is often commercially sold in restaurants as "
Despite their worldwide distribution and great abundance, there are few functioning
In Central America, the primary species of squat lobster targeted by fisheries is a species of
Classification
Broadly, squat lobsters are classified into two superfamilies: Chirostyloidea and Galatheoidea.
Evolutionary history
Squat lobsters contain a total of around 60 genera,
Distribution
Generally, species richness of deep-sea squat lobsters increases with proximity to the equator and the Western Pacific.
References
- ^ a b "Squat lobster". www.montereybayaquarium.org. Retrieved 2023-03-27.
- ^ ISBN 978-0-643-10172-2.
- ^ S2CID 26260996.
- ^ ISSN 0025-3162.
- ^ ISBN 978-0-643-10172-2.
- ^ a b c d Lovrich, Gustavo A; Thiel, Martin (2011). Ecology, Physiology, Feeding and Trophic Role of Squat Lobsters. CLAYTON: CSIRO PUBLISHING.
- S2CID 213011895.
- ^ a b Rowden, A. A., Schnabel, K. E., Schlacher, T. A., Macpherson, E., Ahyong, S. T., & Richer de Forges, B. (2010). Squat lobster assemblages on seamounts differ from some, but not all, deep‐sea habitats of comparable depth. Marine Ecology, 31, 63-83.
- ^ ISSN 0967-0637.
- ^ Amos, Jonathan (11 March 2022). "'Squat lobster' photobombs Shackleton's Endurance ship". bbc.co.uk. BBC News. Retrieved 11 March 2022.
- S2CID 213494922.
- ^ ISSN 0340-7594.
- ^ ISSN 0278-0372.
- ^ David Sharp (October 3, 2006). "Maine senator attempts to blow whistle on 'impostor lobster'". Associated Press.
- ^ ISBN 978-0-643-10172-2.
- ^ ISSN 0024-4082.
- ^ S2CID 7933932.
- ^ S2CID 247772934.
- ^ PMID 21095236.
- Raffles Bulletin of Zoology. Suppl. 21: 1–109.
- hdl:10261/42217.
- ^ ISBN 978-0-643-10172-2.
- ^ Schweitzer, Carrie E. & Feldmann, Rodney M. (2000). "First notice of the Chirostylidae (Decapoda) in the fossil record and new Tertiary Galatheidae (Decapoda) from the Americas" (PDF). Bulletin of the Mizunami Fossil Museum. 27: 147–165.
- ^ PMID 15336662.
External links
- Data related to Chirostyloidea at Wikispecies
- Data related to Galatheoidea at Wikispecies
- Media related to Chirostylidae at Wikimedia Commons
- Media related to Galatheidae at Wikimedia Commons