At night, they migrate vertically to the surface in the safety of dark to hunt for prey. Here in Southern California, you can identify squid boats by their bright lights during the spring and early summer season. Giant Squid grow incredibly quickly and reach their adult size of feet after just a few years. Scientists believe their lifespan is up to 5 years. Humboldt Squid see a specimen in Oddities travel in packs based on size.
Younger smaller squid need to avoid the larger 6-foot adults or else they risk becoming a meal. There is also a dwarf population of Chambered Nautilus that may be even smaller. At Birch Aquarium: Chambered Nautilus.
Modern day nautilus are sometimes called living fossils, this is sort of true. Ammonites were common shelled cephalopods from about million years ago until they were practically wiped out during the K-PG extinction event — the same one that killed off the dinosaurs. Ancient ammonites, though they look like modern day nautilus, were actually more closely related to octopus, squid, and cuttlefish.
One of the largest differences between ancient ammonites and modern nautilus, is that paleontologists believe ammonites could retract into their shells, where as nautilus cannot. There are six different types of nautilus and all have external shells that they cannot retract into.
They have unusual arms compared to the rest of the cephalopods. Their arms are numerous often more than 90 and they do not have any suction cups.
Instead, they have thin structures called cirri that retract in and out of sheaths at the end of each arm. Most nautilus are found in warm waters but spend most of their time in the deep, dark, depths. They are actually quite powerful. An average octopus has suckers, and the larger ones can hold up to 35 pounds.
The sea creatures can operate them individually and use them to move around and catch prey. One alarming behavior involving captive octopuses occurs when they get bored. This is known as autophagy. Instead, an arm is shorter and stronger than a tentacle and has suckers all over. In addition, tentacles generally come in pairs. So in this sense, octopus only have arms and no tentacles. According to this study octopuses have two legs and six arms.
The Haliphron Atlanticus is a sizeable octopus species widely known as the seven-arm octopus. One might assume from the name of this octopus, which is to be found in the Pacific and Atlantic Oceans that it only has seven arms. The truth is that the male seven-arm octopus only appears to have seven arms. The eighth arm of the males is used for reproduction and is coiled in a sac beneath its right eye. This is the reason why the species have acquired this misleading name but in fact, even the seven-arm octopus is characterized by the existence of eight limbs.
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