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Hyas Distribution the Toad Crab Is

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Hyas Distribution the Toad Crab Is Hyas araneus This is one found on the nearby Hyas araneus shoreline. Class: Malacostraca Order: Decapoda Family: Oregoniidae Genus: Hyas It is widespread in the North-East Atlantic, including Iceland, Distribution Norway, the British Isles and the coasts of central Europe. The toad crab is widespread It is also common along the coasts of Labrador, Newfoundland on both sides of the North and Nova Scotia. It occurs in both the Bay of Fundy and the Atlantic Ocean. Gulf of St. Lawrence. Distribution continues southwards It is known as the spider to Rhode Island, USA. crab in other areas. Habitat It inhabits a wide variety of habitats from vertical rock walls to Globally it ranges from rough ground and is frequently seen climbing up kelp plants. shallow subtidal areas to In Nova Scotia Hyas araneus is found on hard and sandy depths of 1,650 metres. substrates, among rocks and seaweed on the lower shore and They are on all kinds of below low tide level to a depth of about 50 m. Although not substrate and on current particularly selective about habitat they appear to prefer gravel, exposed locations as well as sand or mud substrates in local areas. in calm waters. Food The toad crab feeds on a variety of organisms including They are omnivorous amphipod, bivalve, gastropod, chiton, sea urchin and small crab. feeding on a variety of They prey on surface feeding fish as well as being scavengers of items including seaweed. dying or dead fish. At the larval stage they feed on plankton. They are both predators Young crabs feed on small molluscs and barnacles. and scavengers. Reproduction Males select a female to follow in a form of courtship. He holds Adult crabs attract each on to her and when she finds him acceptable mating takes place. other using pheromones The testes or ovaries are situated dorsally in the thorax. Testes (chemical scents). This open externally in the male near the basal segment of the last brings individuals together pair of legs. The male sperm are inserted using his first pair of for the spring mating abdominal legs into the genital opening of the female during season. Females need to copulation. Sperm is deposited directly into her oviduct. She have a shell width of 20- broods the fertilized eggs until hatching occurs. 25mm for this to occur. Development Larvae are dispersed throughout the upper water column by Larvae hatch during the oceanic currents. The larvae pass through several stages of early, warm summer growth and development (moults) until they become megalopa, months and float to the the final larval stage. Once they reach this stage they are ready to surface. These tiny “zoea” search for an area where they can settle on the bottom and larvae adapt to a planktonic moult into tiny crablets. These very young crabs travel to lifestyle living close to the coastal waters and begin a moulting cycle and life as juvenile surface, free swimming and crabs. They moult many times as they grow. Juveniles usually feeding on plankton. reach sexual maturity at 20 mm carapace length. Characteristics The first pair of legs has well developed pincers or claws. The shell is pear-shaped; it These chelipeds are equal in length to each other. They is almost round at the base. account for about two-thirds the length of the walking legs. The top surface (carapace) They are much shorter and stouter than pairs 2-5, which are is usually a red-brown to long, slender and spider-like. This is why the olive colour, shading to a species is also commonly referred to as the Spider white colour on the lower crab. Adult males weigh up to 0.75 kg with a surface. There are large, carapace length and width up to 10.5 and 7.5 cm. scattered tubercules, Adult females are typically smaller than males, (growths) on the carapace. reaching a maximum carapace width of 6.5 cm. It has a rostrum, a forward Each of the tapered horns of the rostrum has two extension of the carapace rows of hooked dorsal setae (hair like bristles). situated between the eyes. These horn extensions usually touch at the tip giving the front It consists of two tapered of the carapace a somewhat beak shape. horns, close together. This species of crab is slow moving and in its own Adaptations defense utilizes several body parts to place various items This species has superb of disguise around its body. The strong chelipeds cut camouflage which it makes chunks of seaweed for placement around the carapace. for itself. Their carapace is These pieces hook onto the numerous tubercules and often covered with a bristly hairs. This attached seaweed, and other selected growth of barnacles and items, invites small organisms such as caprellids and other invertebrates. These hydroids to colonize the carapace. It becomes a well encrusters remain attached hidden, slow moving “forest”. It frequently sits still to the crab. It also attaches amongst its surrounding seaweed ocean garden. a variety of other objects to itself including seaweed. Commercial harvesting has occurred, however processing has been problematic. Status/Threats Future management of this resource The species is common. requires further research. Larvae are preyed upon by Seawater acidification and global warming various marine species. are ongoing threats to all marine life, Adults are prey of lobster especially with crustaceans. and surface feeding fish. These are a common occurrence on Sightings in Nova Scotia shorelines. Numerous and frequent. .
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