Dr. Paddy Ryan, USA
Info
Notomithrax ursus (J. C. Fabricius, 1787)
Notomithrax ursus, the hairy kelp crab, truly deserves its name because of a multitude of golden-brown hairs.
The carapace is usually covered by a dense growth of algae, sponges or hydroids attached to hooked hairs and tubercles.
The claws of the crab are reddish-orange with bright white tip , and along the segment in front of the claw there are two granular ridges.
The carapace is rounded at the back and has a pair of spines at the front, it grows up to 4 cm long.
Bear crabs camouflage their bodies on the reef by attaching pieces of seaweed to the curved hairs that cover their bodies.
Their hairy bodies may have inspired Dr. Herbst in 1788 to name them after Ursus, the bear.
Crabs are generally scavengers, meaning they eat whatever they can find, and as omnivores, this includes both plants and other animals.
In a study conducted on algal crabs on the coast of New Zealand's South Island, the foregut of a sample of crabs was opened to determine what food they had consumed.
Algae, including calcareous red algae and branching brown algae, were identified as the most commonly consumed substance, as they were found in almost all of the crabs studied. Other common foods included isopods, psyllids, and decapods (e.g., small fish, crayfish, other crustaceans). Clams, sponges, bryozoans, and more were also consumed, but not frequently.
The meat consumed was usually from dead animals, as kelp crabs move slowly and are not very strong.
The guts of the female crabs contained more brown, unbranched algae and unknown substances than those of the male crabs, although there was no obvious difference in the amount or variation of food consumed.
The type of food consumed also depended on the size of the crab.
Smaller male crabs consumed more snails, isopods, and amphipods, while larger males ate more algae and decapods. Similarly, smaller female crabs ate more isopods and larger females ate more algae.
These differences are likely due to the effect of size on the crab's ability to process food.
Both soft-bodied and hard-bodied animals were consumed, as was a wide range of algae. Algal crabs use their claws to tear their food, and predation techniques depend on the mobility of the prey. Larger, adult crabs are better able to process food because they have stronger claws and larger mouths.
There is also evidence that the algae species that the kelp crab attaches to its body are also preferentially consumed, so the masking behavior of these crabs serves as a food store. The crab can eat up to 4.1% of the algae masking it when food is not available.
Algal species for masking can also be selected for "caloric value or content of vitamins, nitrogen, or specific nutrients such as sugars and amino acids."
Notomithrax ursus uses its claws to perform a variety of feeding techniques that it employs on different prey.
They can be used to pull chitons and limpets off rocks or to open shells and snails. Small arthropods, young crustaceans, and polychetes were captured by poking around with open chelipeds, which were quickly closed upon contact with the prey. The chelipeds are also used to tear prey into smaller pieces.
For example,small starfish are twisted with the chelipeds to tear off an arm. "Digging" gravel is also used to feed on detritus and microorganisms. In this feeding technique, Notomithrax ursus picks up pieces of gravel with the chelipeds and moves them along the inner part of the mouth to take particles from the gravel[.
Algae crabs must camouflage themselves because they cannot protect themselves from other marine animals such as sea otters, sea turtles, lobsters, stone crabs, and octopuses.
Other fish can also eat smaller crabs if they have a strong enough mouth. Studies have shown that decorated seaweed crabs are eaten significantly less often than cleaned crabs.
These crabs are also better able to avoid predators because they are nocturnal.
Sometimes algae crabs hide under sponges, which can serve as protection because of their neurotoxins.
Many spider crabs attach various types of living material to camouflage themselves to avoid detection by predators. This strategy utilizes a number of commonly evolved features, including a pear-shaped carapace, long, agile paws, hook sets, and a stereotyped behavioral pattern of collecting parts of other organisms and attaching them to their bodies between hook sets.
Notomithrax ursus (Herbst, 1788) is a New Zealand majid crab that lives among algae and masks itself primarily with them.
In doing so, it uses all the skills we expect from a dressmaker.
Without her mask, the crab selects algae that she can manipulate, measures and cuts each piece, guides it to her mouth, and then plants it on her body in roughly regular order so that the severed ends are inserted into the hooked setae and only the intact end is visible.
Longer pieces are planted on the body and smaller pieces on the legs, creating a profile resembling a clump of seaweed.
The distribution of the algae follows the distribution of the hooked setae on the crab. The number of attached pieces is independent of the size of the crab, and as the carapace width increases, the crabs compensate by cutting off longer pieces of algae. The allometry of the chelipeds explains the scaling of the mask.
The total length of algae used can range from 0.6 to 2.6 mm (mean 1.36 mm).
Increasing load on the mask is accompanied by an increase in the number and size of hook sets, which increases attachment.
The behavior of Notomithrax ursus should be referred to as "dressing" rather than "decorating".
It uses a stereotyped pattern of behavior to follow a pattern dictated by the distribution of hooked setae, producing a tailored garment that hides it from predators.
A hypothesis is made about the evolution of masking from passive to active.
Commonly used algae: Halopteris spicigera and Corallina ffi c inalis.
Color of the crab: brown, yellow, green.
Synonyms:
Cancer ursus Herbst, 1788
Cancer ursus J. C. Fabricius, 1787
Paramithrax cristatus Filhol, 1886
Paramithrax Latreillei Miers, 1876
Notomithrax ursus, the hairy kelp crab, truly deserves its name because of a multitude of golden-brown hairs.
The carapace is usually covered by a dense growth of algae, sponges or hydroids attached to hooked hairs and tubercles.
The claws of the crab are reddish-orange with bright white tip , and along the segment in front of the claw there are two granular ridges.
The carapace is rounded at the back and has a pair of spines at the front, it grows up to 4 cm long.
Bear crabs camouflage their bodies on the reef by attaching pieces of seaweed to the curved hairs that cover their bodies.
Their hairy bodies may have inspired Dr. Herbst in 1788 to name them after Ursus, the bear.
Crabs are generally scavengers, meaning they eat whatever they can find, and as omnivores, this includes both plants and other animals.
In a study conducted on algal crabs on the coast of New Zealand's South Island, the foregut of a sample of crabs was opened to determine what food they had consumed.
Algae, including calcareous red algae and branching brown algae, were identified as the most commonly consumed substance, as they were found in almost all of the crabs studied. Other common foods included isopods, psyllids, and decapods (e.g., small fish, crayfish, other crustaceans). Clams, sponges, bryozoans, and more were also consumed, but not frequently.
The meat consumed was usually from dead animals, as kelp crabs move slowly and are not very strong.
The guts of the female crabs contained more brown, unbranched algae and unknown substances than those of the male crabs, although there was no obvious difference in the amount or variation of food consumed.
The type of food consumed also depended on the size of the crab.
Smaller male crabs consumed more snails, isopods, and amphipods, while larger males ate more algae and decapods. Similarly, smaller female crabs ate more isopods and larger females ate more algae.
These differences are likely due to the effect of size on the crab's ability to process food.
Both soft-bodied and hard-bodied animals were consumed, as was a wide range of algae. Algal crabs use their claws to tear their food, and predation techniques depend on the mobility of the prey. Larger, adult crabs are better able to process food because they have stronger claws and larger mouths.
There is also evidence that the algae species that the kelp crab attaches to its body are also preferentially consumed, so the masking behavior of these crabs serves as a food store. The crab can eat up to 4.1% of the algae masking it when food is not available.
Algal species for masking can also be selected for "caloric value or content of vitamins, nitrogen, or specific nutrients such as sugars and amino acids."
Notomithrax ursus uses its claws to perform a variety of feeding techniques that it employs on different prey.
They can be used to pull chitons and limpets off rocks or to open shells and snails. Small arthropods, young crustaceans, and polychetes were captured by poking around with open chelipeds, which were quickly closed upon contact with the prey. The chelipeds are also used to tear prey into smaller pieces.
For example,small starfish are twisted with the chelipeds to tear off an arm. "Digging" gravel is also used to feed on detritus and microorganisms. In this feeding technique, Notomithrax ursus picks up pieces of gravel with the chelipeds and moves them along the inner part of the mouth to take particles from the gravel[.
Algae crabs must camouflage themselves because they cannot protect themselves from other marine animals such as sea otters, sea turtles, lobsters, stone crabs, and octopuses.
Other fish can also eat smaller crabs if they have a strong enough mouth. Studies have shown that decorated seaweed crabs are eaten significantly less often than cleaned crabs.
These crabs are also better able to avoid predators because they are nocturnal.
Sometimes algae crabs hide under sponges, which can serve as protection because of their neurotoxins.
Many spider crabs attach various types of living material to camouflage themselves to avoid detection by predators. This strategy utilizes a number of commonly evolved features, including a pear-shaped carapace, long, agile paws, hook sets, and a stereotyped behavioral pattern of collecting parts of other organisms and attaching them to their bodies between hook sets.
Notomithrax ursus (Herbst, 1788) is a New Zealand majid crab that lives among algae and masks itself primarily with them.
In doing so, it uses all the skills we expect from a dressmaker.
Without her mask, the crab selects algae that she can manipulate, measures and cuts each piece, guides it to her mouth, and then plants it on her body in roughly regular order so that the severed ends are inserted into the hooked setae and only the intact end is visible.
Longer pieces are planted on the body and smaller pieces on the legs, creating a profile resembling a clump of seaweed.
The distribution of the algae follows the distribution of the hooked setae on the crab. The number of attached pieces is independent of the size of the crab, and as the carapace width increases, the crabs compensate by cutting off longer pieces of algae. The allometry of the chelipeds explains the scaling of the mask.
The total length of algae used can range from 0.6 to 2.6 mm (mean 1.36 mm).
Increasing load on the mask is accompanied by an increase in the number and size of hook sets, which increases attachment.
The behavior of Notomithrax ursus should be referred to as "dressing" rather than "decorating".
It uses a stereotyped pattern of behavior to follow a pattern dictated by the distribution of hooked setae, producing a tailored garment that hides it from predators.
A hypothesis is made about the evolution of masking from passive to active.
Commonly used algae: Halopteris spicigera and Corallina ffi c inalis.
Color of the crab: brown, yellow, green.
Synonyms:
Cancer ursus Herbst, 1788
Cancer ursus J. C. Fabricius, 1787
Paramithrax cristatus Filhol, 1886
Paramithrax Latreillei Miers, 1876
