The Wise Old Crab or the Old Hermit Crab is a hermit crab who appears in Nicktoons: Battle for Volcano Island and Nicktoons: Globs of Doom. He is also a friend of the Nicktoons Heroes.
In Battle for Volcano Island, The Crab befriends the Nicktoons and explains that their enemy, The Mawgu, has escaped from his prison and created a terrible ooze which corrupts everything it touches. But the prophecies say that The Chosen Ones will save them. The Crab trains them and tells the heroes to follow him so that he can direct them to camp.
In Globs of Doom, the Crab returns and shows the Heroes (and their enemies) a new weapon to defeat the morphoids.
Hermit crabs are decapod crustaceans of the superfamily Paguroidea . They are not closely related to true crabs. Hermit crabs are quite commonly seen in the intertidal zone, for example in tide pools.
Most species of hermit crabs have long soft abdomens which are protected from predators by the adaptation of carrying around a salvaged empty seashell into which the whole crab's body can retract. Most frequently hermit crabs utilize the shells of sea snails, marine gastropod mollusks. The tip of the hermit crab's abdomen is adapted to clasp strongly onto the columella of the snail shell. As the hermit crab grows in size, it has to find a larger shell and abandon the previous one.
This habit of living in a second hand shell is what gave rise to the popular name "hermit crab", which is a reference to the idea of a hermit living alone in a small cave.
There are about five hundred known species of hermit crabs in the world, most of which are aquatic and live in saltwater at depths ranging from shallow coral reefs and shorelines to deep sea bottoms. However in the tropics, a number of species are terrestrial, and some of these are quite large, for example, Petrochirus diogenes. The Caribbean hermit crab (Coenobita clypeatus) is known to climb trees.
A number of other species, most notably king crabs, have abandoned seashells for a free-living life; these species have forms which are more similar to true crabs, and are known as carcinised hermit crabs.
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As hermit crabs grow they require larger shells. Since suitable intact gastropod shells are a limited resource, there is frequently strong competition among hermit crabs for the best available shells. The availability of empty snail shells at any given place depends primarily on the relative abundance of gastropods in the right range of sizes, compared to the demographics of the population of hermit crabs.
An equally important issue is the frequency of organisms which prey upon gastropods but leave the shells intact . A hermit crab with a shell that is too small cannot grow as fast as hermit crabs with well fitting shells, and is more likely to be eaten as it cannot withdraw completely into the shell .
For some larger marine hermit crab species, having one or more sea anemones growing on the shell can be very useful, because the anemones tend to scare away fish and other marine predators that might otherwise attack the crab. The sea anemone also benefits because it is well positioned to consume loose fragments of the hermit crab's meals. Furthering this mutualism, sea anemones can be transferred to a new shell when the hermit crab changes shells.
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The various types range in size from species with a carapace only a few millimetres long, to Coenobita brevimanus which can approach the size of a coconut. The shell-less hermit crab Birgus latro is the world's largest terrestrial invertebrate.
Terrestrial hermit crabs begin their lives in the sea, but through a process of moulting develop the ability to breathe air. After the last developmental moult, the young hermit crab will drown if left in water for an indefinite period of time. Their link with the sea is never entirely broken however, as hermit crabs carry a small amount of water in their shells at all times to keep their abdomen moist and their modified gills hydrated. It is believed that C. brevimanus is the species of Coenobita best adapted to life on water and land.
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The fossil record of in situ hermit crabs using gastropod shells stretches back to the Late Cretaceous. Before that time, at least some hermit crabs used ammonites' shells instead, as shown by a specimen of Palaeopagurus vandenengeli from the Speeton Clay, Yorkshire, UK from the Lower Cretaceous .
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The reproductive organs of hermit crabs are located near and just below the animal's heart and open to the outside at the base of the last pair of walking legs in the male. In the female, they are located at the base of the middle pair of walking legs. Female hermit crabs usually lay their eggs shortly after copulating, but they can also store sperm for many months. The eggs are fertilised as they are laid by passing through the chamber holding the sperm. The eggs are carried and hatched in a mass attached to the abdomen inside the shell. The number of eggs is usually large, but depends on the animal's size.
The developing hermit crabs go through four stages, two of which (the nauplius and protozoea) occur while still in the egg. Most crabs hatch at the third stage, the zoea. This is a larva stage wherein the crab has several long spines, a long narrow abdomen, and large fringed antennae. The fourth stage of development is the megalopa.
Land hermit crabs will move inland away from the water, where they search for abandoned shells to inhabit. Hermit crabs then begin growing and developing through a process called moulting. In this process, the crabs shed their exoskeleton. During this, the crabs are extremely vulnerable and inactive, and usually find protection by burrowing in the ground. It takes around 10 days for their new exoskeleton to harden, and during this period the crab is able to regenerate any lost or broken claws or legs. A hermit crab can moult as often as every other month when young, or every 18 months when they are older.
Hermit crabs release their eggs in the ocean, near the shore. Because of this, hermit crabs cannot reproduce in captivity without special equipment to simulate a shoreline .
Little is known about reproducing hermit crabs in captivity. It is not yet understood whether seasonal changes contribute to the animals' mating patterns. Some studies, however, suggest that males in captivity become more sexually interested when they are provided with brightly colored shells that increase self-confidence.
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Several marine species of hermit crabs are common in the marine aquarium trade. Of the approximately 15 terrestrial species in the world, the following are commonly kept as pets: Caribbean hermit crab, Coenobita clypeatus, and the Ecuadorian hermit crab, Coenobita compressus. Other species such as Coenobita brevamanus, Coenobita rugosus, Coenobita perlatus or Coenobita cavipes are less common but growing in availability and popularity as pets. Hermit crabs also require certain specifications to be able to thrive well as pets. The list is as follows:
- Humidity gauges (humidity: 75-85% relative)
- Temperature gauges (temperature: 70-75° F)
- Substrate: sand, coconut fiber (must be deep and diggable for moulting)
- 1/2 gallon tank for one crab; up to ten gallon tank for about 20 crabs
- Shells (shells are changed during growth)
- Separate moulting tank
- Fresh water dish
- Salt water pool for submerging (aquarium salt)
These omnivorous or herbivorous species can be seen as useful in the household aquarium as scavengers, because they eat algae and debris.Hermit crabs were once thought to be "throwaway pet" that would only live a few months, but with proper care can thrive for many years. For example, Coenobita clypeatus is commonly listed as having a 23 year lifespan if properly cared for , and some have lived longer than 32 years . Golf ball sized crabs are most probably younger than ten years old, mandarin sized crabs are likely to be at least in their twenties, and jumbo sized crabs are between twenty and thirty years old .
In general, and despite their moniker, hermit crabs are social animals that do best when kept in groups . They also require a temperature and humidity controlled environment, and an adequate depth of substrate to allow them to dig while moulting.