Pagurus novizealandiae

Hermit crabs are usually easy to identify because of the colouration of their antenna and their antennules (a small structure resembling antennae which sits in front of the actual antennae). The hermit crab is approximately about the size of a coin and on average about 56mm in length, but this is slightly limited by the size of the shells available. Its body is up to wide. The crab abdomen is spiral shaped, The crab protects and shields itself from predators and potential danger by contracting rapidly back into its shell out of reach. It uses its large chela as a door which protects it once it has retreated back into the safety of its shell. Throughout their lifetime hermit crabs use and adopt empty mollusk and gastropod shells, such as cats eyes, snails and periwinkles to protect their soft and vulnerable abdomens. The crabs carry their shells around on their backs with small legs which are modified so that their back end can grip into the shell; they use their abdominal muscles to hold themselves securely in place. Over time, as hermit crabs grow they must switch shells to accommodate their expanding bodies as they need to find larger shells for protection. ==Distribution==

Natural global range The Pagurus novizealandiae has not been identified to naturally occur anywhere else in the world as the species is endemic to New Zealand. Pagurus novizealandiae is mainly found in the intertidal zones right throughout both the North and South Island, however this species is mostly found in the South Island, or on the Auckland Islands 465 km south-east of New Zealand. Habitat preferences The Pagurus novizealandiae is found only in marine environments, around rocky intertidal shorelines or rocky sub tidal reefs. This species of hermit crab cannot tolerate high dilution of seawater at all, therefore cannot survive in freshwater habitats. They are generally restricted to areas, usually the estuary where strong tidal activity takes place and the salinity of the water remains continuously high enough to support the crab's requirements. The crab's tidal habitat means that it can be found at depths ranging from low tide to approximately 15m. ==Life cycle/phenology==

Moulting is a vital part of the Pagurus novizealandiae life cycle in order to grow and develop, During the searching process there is very high demand for shells as the crabs want to find a new home as quickly as they can so that they are safe from predators. Timing and location is a very important part in determining where to go to undergo the moulting procedure. Both the male and female hermit crab produce inviting sex pheromones. The males are very aggressive during breeding and are known do be quite dominant over the females. The Pagurus novizealandiaes behaviours around the transfer of sperm will be unique to the species but the process will still involve lining up gonopores on the crab's legs and transferring the sperm from the male to female. In terms of egg laying, the female New Zealand hermit crab has two to three pleopods. These carry the fertilised eggs, which are covered in a glue like substance that helps them to stick onto her abdomen. The hermit crab protects the eggs inside of its shell out of dangers reach until the embryo development is fully complete. When the time has come for the eggs to be hatched and released the eggs let off a pheromone that stimulates the female, her movements help to hatch the eggs and they are delivered to the plankton. The larvae take weeks to months to grow, going through several different larval processes until they reach the final stages where they can occupy a small part of a broken snail shell. Eventually they become a juvenile hermit crab and start their hunt for a suitable shell. ==Diet and foraging==

Hermit crabs are scavengers, they will forage during the night for dead or injured animals and feed off their remains. They can also be found moving about in rock pools during the day. Its large pincer tends to remove the food then the smaller chela acts as a scoop which collects up the organic or animal material, which is then transported to the mouth with the crabs third maxillipeds (the outermost mouth parts, they hold the food until its ready to be pushed into the mouth). This is because often the larger pincer is too big to complete this process. Hermit crabs sometimes brace themselves over their prey using their walking legs to make it easier to rip pieces of flesh away from the animal. They are real scavengers in the sense that they will try and consume as much as they can in a short period of time before larger scavengers come along and steal their food from them. ==Predators, parasites and diseases==

Because the hermit crab lives in the bottom of rock pools and ocean floors, and due to its size, its predator list is long. It is easy prey for the likes of fish, and octopus. Other crabs are also known to eat the smaller and more unprotected species, like the hermit crab, hence the need for shells to protect the soft body. Because the hermit crab "sifts" through the sediment at the bottom of the ocean, smaller invertebrates are known to utilize this as an opportunity for themselves. ==Shell trading==

Hermit crabs display quite interesting behaviours during the shell trading process. The trade usually involves two crabs, they engage in a sort of physical fight probing, rocking and knocking each other's shells around. This type of behaviour gives the crabs the chance to check out the quality and size of one another's shells and actually usually results in both crabs benefitting from the trade. Large numbers of crabs can trade shells at once and it can take place in a very short period of time. Once they have traded it will not take the crab long to decide whether or not the shell is suitable. ==References==