coleoid
Quick Summary
The Coleoidea are a subclass of cephalopods, which are exclusively marine mollusks. This group includes octopuses, squids, and cuttlefishes. Unlike their ancient relatives, the nautiloids and ammonites, coleoids typically have an internal, reduced, or absent shell. They possess eight arms, and in the case of squids and cuttlefishes, two additional tentacles, all equipped with suckers or hooks. Coleoidea have a closed circulatory system with three hearts and blue blood containing the respiratory pigment hemocyanin. They are carnivorous, feeding on other cephalopods, crustaceans, mollusks, and small fish.123
Ask Britannica AI about this topic
Britannica doesn't have a full article on this topic, so we've curated a list of our relevant coverage.
molluskAnnotated classification…recent species); Ammonoida (fossils); and Coleoida (fossils and 4 recent orders). Many aspects of molluscan classification remain unsettled, particularly for gastropods and bivalves. The Amphineura, the former name for a group made up of the Polyplacophora (chitons) and Aplacophora (caudofoveates and solenogasters) within one subphylum, has been replaced…
Read More…recent species); Ammonoida (fossils); and Coleoida (fossils and 4 recent orders). Many aspects of molluscan classification remain unsettled, particularly for gastropods and bivalves. The Amphineura, the former name for a group made up of the Polyplacophora (chitons) and Aplacophora (caudofoveates and solenogasters) within one subphylum, has been replaced…
Read More
cephalopodAnnotated classificationSubclass Coleoidea (octopuses, squids, belemnites, cuttlefishes) Triassic to present; shell internal, reduced, vestigial, or lacking; 2 sets of gills; 8 or 10 arms, having suckers or hooks. †Order Belemnoidea (belemnites) Triassic to early Cenozoic; fossils only; shell consisting of solid rostrum, small chambered
Read MoreSubclass Coleoidea (octopuses, squids, belemnites, cuttlefishes) Triassic to present; shell internal, reduced, vestigial, or lacking; 2 sets of gills; 8 or 10 arms, having suckers or hooks. †Order Belemnoidea (belemnites) Triassic to early Cenozoic; fossils only; shell consisting of solid rostrum, small chambered
Read More
- cephalopodEcology
The Coleoidea are carnivorous and live principally on other cephalopods, crustaceans, mollusks, and small fishes. In the food cycle of the squid Illex, in which the adults feed upon young mackerel and the adult mackerel feed upon young squid. Squids also are cannibalistic. Octopus feeds upon…
Read MoreThe Coleoidea are carnivorous and live principally on other cephalopods, crustaceans, mollusks, and small fishes. In the food cycle of the squid Illex, in which the adults feed upon young mackerel and the adult mackerel feed upon young squid. Squids also are cannibalistic. Octopus feeds upon…
Read More - cephalopodForm and function
All members of the Coleoidea (octopuses, squids, and cuttlefishes) possess a closed circulatory system of blood vessels; in Nautilus it is partly lacunar (i.e., made up of sinuses). The blood contains a blue respiratory pigment, hemocyanin (a copper compound), dissolved in the plasma. There are three hearts, the main…
Read MoreAll members of the Coleoidea (octopuses, squids, and cuttlefishes) possess a closed circulatory system of blood vessels; in Nautilus it is partly lacunar (i.e., made up of sinuses). The blood contains a blue respiratory pigment, hemocyanin (a copper compound), dissolved in the plasma. There are three hearts, the main…
Read More