Widespread along the east coast, and lining the ocean floor anywhere from rocks to sandy bottom, one can find Atlantic Rock Crabs

Pekkala, Caroline

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Salve Regina University Digital Commons @ Salve Regina Narragansett Bay Species Accounts Student Work 2024 Atlantic Rock Crab, Cancer irroratus Caroline Pekkala Follow this and additional works at: https://digitalcommons.salve.edu/nbsa Atlantic Rock Crab (Cancer irroratus)Caroline PekkelaSalve Regina UniversityApril 22, 2024Widespread along the east coast, and lining the ocean floor anywhere from rocks to sandybottom, one can find Atlantic Rock Crabs.Hodnett, R. (2019, Aug 17). Atlantic rock crab (Cancer irroratus) in Trout River, Newfoundlandand Labrador, Canada [Photograph]. Wikimedia Commons.https://commons.wikimedia.org/w/index.php?curid=89776622Identification:The Atlantic rock crab is known for its broad outer shell, also known as a carapace. They havenine marginal teeth around the front of their oval shaped shell. The shell can be mostly yellow orred with purplish brown spots. They also have black tips on the top of their claws. The width ofthe top of its shell ranges from males to females, females carapace being smaller. The width ofthe top of the shell for a mature male averages between 50mm-140mm (Page, 2002). A fullgrown male can weigh between 49-202g (Page, 2002). It is rare for a female's upper shell to bewider than 100mm (Page, 2002). Although males are larger, the female abdomen is larger due tothe necessity to carry eggs. (Government of Canada, 2022).Similar Species:The rock crab is not to get confused with the Jonah crab, Cancer borealis. They are found in thesame waters and look very similar at first glance because they both have a carapace. Thecarapaces differ as the rock crab has smoother edges. Jonah crabs are bigger than rock crabs,males being up to 175mm, and are generally found in deeper water (Barnegat Shellfish 2019).The shapes of the carapaces differ too, as the Jonah crabs are more rounded. They also differ incolor as the spots on the shell of the Jonah crab are yellow compared to the vibrant brown coloron the rock crab. (Barnegat Shellfish 2019).Classification:Phylum: ArthropodaClass: MalacostracaOrder: DecapodaFamily: CancridaeGenus: CancerOpen Tree of Life. (2023, Sep 18). Cancer.https://tree.opentreeoflife.org/opentree/argus/ottol@706443/CancerGeographic Variation:There is no specific phylogenetic evidence about the Cancer irroratus. But one of the mostclosely related species is the Jonah crab, which can get commonly confused with the atlanticrock crab through its physical features. Two other closely related species are the Red Rock Crab(Cancer productus), and the Brown Rock Crab (Cancer pagurus); The Brown Rock Craboriginating from the Pacific ocean. Both species have similar physical features. This genus ofcrabs are hypothesized to have originated in the Pacific ocean and through the trans-Arcticinterchange they moved to the Atlantic ocean and speciated. This shows that the Atlantic speciesare more closely related to each other than the species present in the Pacific ocean, but they havecommon ancestors relating all of them together (Harrison & Crespi, 1999).There is lots of geographic variation in the genus Cancer. They are found in both coastlines ofthe Pacific Ocean and on the east coastline of the Atlantic Ocean. Blue crabs and spider crabs aresome examples of the other crabs found in Narragansett Bay. These crabs are under the sameinfraorder, brachyura. The blue crab also has a carapace, but it is less ovular than the rock crab,and the color change is much different, blue crabs being a blue shade. Spider crabs look muchdifferent than rock crabs, they have much longer legs and a much smaller carapace that is morecircular.Fossil History:There are a few fossil records available shown near New York, and North Carolina (C.E.Schweitzer, 2010).Systematics Summary:The Atlantic rock crab is closely related to other crab species in the genus Cancer within theAtlantic ocean, and these crabs share common ancestors with species in the pacific ocean whichalso fall into the Cancer genus. The Atlantic rock crab most likely evolved from Red Rock Crab(Cancer productus) and the Brown Rock Crab (Cancer pagurus) (Harrison & Crespi, 1999).Distribution in Rhode Island:From 2020-2023 we have seen an influx of these crabs in Canada. They range all along the EastCoast. In a directory map from The Global Biodiversity Information Facility, it showed mostcrab growth starting at 1935 until present day. We will see these crabs continue to grow as theyhave been for the past 80 or so years (Cancer irroratus say, 1817).Habitat:Rock Crab live on the ocean floor. The crabs in the north are typically found in more shallowwaters (0 - 20 meters), compared to rock crab in more southern areas (750 meters) (Governmentof Canada, 2022). They adapt to many depths of the ocean being above and below the low tideline, up to 2600 feet. Typically, smaller crabs prefer more soft, muddy or sandy bottoms, whereaslarger crabs prefer more dense, rocky-bottomed habitats (Page 2002).Breeding Biology:The mating time is normally autumn, after both males and females have mounted their shells.Males want a completely hard shell to mate which is why they will mount their shell earlier inthe winter. This differs from the females mounting their shells around August, to make sure it issoft enough to mate. Males and females differ in when they become sexually mature, womenbeing when they reach 60mm and men when they reach 70mm (Page 2002). Females store eggsfor around a year after they are fertilized, and because the offspring are so susceptible to threatswhen they are born, they are kept deep on the ocean floor or in shallow water for protection. “Forthe first part of their life these young crabs are extremely vulnerable to predators and waterturbulence. To increase their chance for survival they remain in shallow water and at the bottomof the ocean floor for protection” (Page 2002).Feeding Behavior:The Atlantic Rock Crab feed in deep parts of the ocean and therefore only eat species that arealso in the deep parts of the ocean. They are “opportunistic feeders” and look for smallercreatures (Government of Canada, 2022). Some of these organisms are polychaetes, mussels,gastropods, and crustaceans. These crab have a sense of smell and can sense certain odors inregards to their food (Page 2002).Behavior Summary:Rock Crabs live on the ocean floor and their specific habitat and diet depends on their size alongwith what surrounds them. They are most abundant in the northern parts of the East Coast but arefound all the way down to Florida. Mounting of their shells is how they reproduce and theiroffspring are quite vulnerable right at birth.Population Status in Narragansett Bay:There is not a large amount of rock crabs specifically in Narragansett Bay, but they are spreadout along the east coast and are most abundant in Canada. As we look farther out into the oceaninto deeper spots we see more abundance in these rock crabs. As of now, there has been threenoted rock crabs in the waters of Narragansett Bay (EOL).Impacts of Human Activity:Male Rock Crabs are harvested and consumed by humans frequently in the waters of Quebec. Toconserve the reproduction of these crabs, females are released back into the ocean when caught.Rock Crabs are also greatly used by fisheries as lobster bait (Government of Canada, 2022).Management:The rock crab is on the list of Rhode Islands Species of Greatest Conservation Need 2015Wildlife Action Plan (SGCN 2015).Priorities for Future Research:Future research should focus on more specific distinctions on potential travels of the Rock Crab.It would be beneficial to discover why they are more abundant in northern areas such as Canadaversus Rhode Island.ReferencesAtlantic rock crab. EOL. (n.d.).https://eol.org/pages/46505909/mapsBarnegat Shellfish, L. (n.d.). Rock Crab / Jonah Crab - similarities and differences. Barnegat BayShellfish. https://barnegatshellfish.org/jonah_rock_01.htmC. E. Schweitzer, R. M. Feldmann, and A. Garassino, H. Karasawa, and G. Schweigert. 2010.Systematic list of fossil decapod crustacean species. Crustaceana Monographs 10:1-222Government of Canada, F. and O. C. (2022, October 7). Government of Canada. (Cancerirroratus).https://www.dfo-mpo.gc.ca/species-especes/profiles-profils/atl-rock-crab-crabe-commun-eng.htmlHarrison, M. K., & Crespi, B. J. (1999). (rep.). Phylogenetics of Cancer Crabs (Crustacea:Decapoda: Brachyura). Elsevier. Retrieved October 19, 2023, fromhttps://www.sciencedirect.com/science/article/abs/pii/S105579039890608X.Hodnett, R. (2019, Aug 17). Atlantic rock crab (Cancer irroratus) in Trout River, Newfoundlandand Labrador, Canada [Photograph]. Wikimedia Commons.https://commons.wikimedia.org/w/index.php?curid=89776622Open Tree of Life. (2023, Sep 18). Cancer.https://tree.opentreeoflife.org/opentree/argus/ottol@706443/CancerPage, K. (n.d.). Cancer irroratus (Atlantic rock crab). Animal Diversity Web.https://animaldiversity.org/site/accounts/information/Cancer_irroratus.htmlRi SGCN 2015 (454) Contents - Rhode Island. (n.d.-b).https://dem.ri.gov/sites/g/files/xkgbur861/files/programs/bnatres/fishwild/swap/sgcnsci.pdf

Atlantic Rock Crab, Cancer irroratus

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Atlantic Rock Crab, Cancer irroratus

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