Squid and Octopuses Squid cuttlefish and octopuses are specialized mollusks known as cephalopods They are the only invertebrates to have filled the same niche as fish Unlike most other mollusks octopuses and squid have no external shell Squid have an internal shell and have 10 suckered legs Octopuses have no shell at all and have 8 legs or tentacles Both have a beak-like mouth and highly developed senses with sophisticated eyes that are similar to those belonging to mammals How do reef squid move Like all cephalopods the reef squid moves using jet propulsion It sucks water in and jets it out again propelling itself in the opposite direction The Caribbean reef squid is often found in shallow reefs and is not scared of divers Their bodies are broad and less streamlined than many other squids so they aren’t quite as nimble They are a mottled green-brown on one side with lighter coloring on the other as camouflage Blue-ringed octopuses have two separate poison glands one to attack prey and the other for defense Are blue-ringed octopuses dangerous They are very dangerous They are the most deadly of all cephalopods to humans The greater blue-ringed octopus carries enough venom to kill 26 adult humans in minutes and it is only about the size of a golf ball This venom is more potent than any venom found in land animals Luckily they are not aggressive and will only sting in self-defense Large shining blue rings cover its surface and they light up when it is alarmed How brainy is an octopus Cephalopods have the largest brains of all the invertebrates and the common octopus has one of the largest brain-to-body size ratios making it the cleverest known invertebrate Scientists have conducted tests that prove its ability to learn complex signs to get food Its brainy behavior in the wild includes using its tentacles to search crevices and rocks to find crabs and other small animals It feeds by drawing food close with its suckered arms and biting its prey with its beak-like mouth Reef squid can communicate through changing the color of their skin
Does anything eat giant squid Giant squid and other deep sea squid are a significant part of a sperm whale’s diet Dramatic underwater battles take place and sperm whales may be permanently scarred by these encounters as the squid fights back and tries to escape The giant squid can reach lengths of up to 59 ft 18 m and can weigh up to 1 ton 900 kg They For how long does a blue-ringed octopus live don’t live long averaging just two years No one has seen a giant squid in its natural habitat as it lives at such great depths Common octopuses are usually solitary and defend their territories from others
Crabs Crabs are decapods meaning they have 10 legs As with lobsters four pairs are for walking and one pair is for fighting mating displays and feeding Like all arthropods crab bodies are usually covered with a hard coating called an exo or outside skeleton A crab’s abdomen is tucked away giving them a rounder body shape The abdomen is also narrower in males than in females Crabs are omnivorous and eat algae worms mollusks bacteria fungi and carrion Where do hermit crabs get their shells Despite their name hermit crabs aren’t true crabs but are instead close relatives They do not grow their own hard casings like other crabs so they must use other empty shells often mollusk or snail shells and structures for protection moving into larger shells as they grow They move by dragging their shell along the ground with their legs and retreat into it when threatened Are pea crabs really the size of peas They certainly are but they can grow as large as a fava bean Pea crabs live in the shells of oysters cockles and mussels moving in uninvited for protection For this reason they are also called oyster crabs although they are found mainly in mussels They can cause damage to the breathing apparatus of their hosts by occasionally taking a hungry nibble at their gills and they also steal their host’s food to survive The pea crab is found from southern Scandinavia to western Africa and throughout the Mediterranean Fully-grown female pea crabs can sometimes grow too large to escape the shells in which they live and are imprisoned for the rest of their lives Hermit crabs live in a variety of habitats Some live on land while others live in the sea
The common shore crab is a very aggressive species often fighting with its own kind Which crab lives in a rock pool Common shore crabs live in waters up to about 197 ft 60 m deep but are often found in salt marshes estuaries and rock pools Common shore crabs eat worms small snails other smaller crabs algae carrion or dead animals mollusks and whatever else they can find It is more often young or immature common shore crabs that inhabit rock pools How much crab do humans eat over 1.5 million tons a year The Japanese spider crab is a very old species of crab and it is often referred to as a living fossil How big is a Japanese spider crab Fully grown the Japanese spider’s leg span can be as large as 12 ft 4 m which is as long as a car but it only weighs 42 lb 29 kg It is the largest of all the crabs These spider crabs live at depths of up to 1000 ft 350 m at the bottom of the Pacific Ocean Japanese spider crabs have orange bodies and their legs are thin with white spots Despite its huge and fearsome appearance it is fairly docile This makes them easy to catch and eat and they are under threat from humans
