Cephalopod
Also known as Cephalopoda, Cephalopods
A cephalopod is any member of the molluscan class Cephalopoda (Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles (muscular hydrostats) modified from the primitive molluscan foot. Fishers sometimes call cephalopods "inkfish", referring to their common ability to squirt ink. The study of cephalopods is a branch of malacology known as teuthology.
AI overview
Cephalopods are marine animals that include squids, octopuses, cuttlefish, and nautiluses, and they're distinctive for having a prominent head with arms or tentacles that evolved from the foot of their molluscan ancestors. They're notable for their intelligence, their ability to squirt ink as a defense mechanism, and they're important enough to science that there's an entire branch of study dedicated to them called teuthology.
AI-generated from the Wikipedia summary — may contain errors.
Species
cephalopods
Class
- PhylumMollusca
- ClassCephalopoda
Habitatmarine
Observations31
头足纲（学名：Cephalopoda）是软体动物门的一个纲。化石种在一万种以上，现仅存786种，主要是各类乌贼和章鱼。头足纲动物为全部海生，肉食性，身体两侧对称，分头、足、躯干三部分。头部发达，两侧有一对发达的眼。足着生于头部，特化为腕和漏斗，故称头足类。漏斗位于头部腹面，在头和躯干之间。原始种类具有外壳，现存种类则多是内壳或无壳。鳃为羽状，一对或二对，心耳和肾的数目和鳃一致。口腔具有颚片和齿舌。神经系统集中，感官发达。循环系统为闭管式。直接发育（无需变态）。 頭足綱可分為兩個到四個亞綱，其中現存兩個亞綱。一個是蛸亞綱（Coleoidea）又稱為二鰓亞綱，外殼已經消失或是內化。此亞綱包括章魚、烏賊、鱿鱼等。另一個是鹦鹉螺亚纲（Nautiloidea）又称為四鳃亚纲，外殼依然存在，此綱包括鸚鵡螺等。另有已滅絕的菊石亚纲（Ammonoidea，也可以分类為四鳃亚纲）和箭石亞綱（Belemnoidea）。 頭足綱分布在所有海域的所有深度，目前沒有發現適應淡水的種類，但有些能夠適應不同鹽度的水。
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Research
8,003 papers- Evolution of cephalopod nervous systems.ReviewCurrent biology : CB · 2023Albertin CB, Katz PSDOI: 10.1016/j.cub.2023.08.092
- Cephalopod behaviour.
Article
43 sectionsContents
- Distribution
- Biology
- Nervous system and behavior
- Senses
- Vision
- Photoreception
- Hearing
- Use of light
- Coloration
- Chromatophores
- Adaptive value
- Origin
- Convergent evolution
- Ink
- Circulatory system
- Respiration
- Locomotion and buoyancy
- Octopus vs. squid locomotion
- Shell
- Head appendages
- Feeding
- Radula
- <span id="Renal appendage"></span> Excretory system
- Reproduction and life cycle
- Sexual maturity
- Fertilization
- Male–male competition{{anchor|Male-male_competition}}
- Mate choice
- Sexual dimorphism
- Embryology
- Development
- Evolution
- Genetics
- Phylogeny
- Taxonomy
- Suprafamilial classification of the ''Treatise on Invertebrate Paleontology''
- Shevyrev classification
- Cladistic classification
- In culture
- See also
- References
- Further reading
- External links
A cephalopod is any member of the molluscan class Cephalopoda (Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles (muscular hydrostats) modified from the primitive molluscan foot. Fishers sometimes call cephalopods "inkfish", referring to their common ability to squirt ink. The study of cephalopods is a branch of malacology known as teuthology.
Cephalopods became dominant during the Ordovician period, represented by primitive nautiloids. The class now contains two, only distantly related, extant subclasses: Coleoidea, which includes octopuses, squid, and cuttlefish; and Nautiloidea, represented by Nautilus and Allonautilus. In the Coleoidea, the molluscan shell has been internalized or is absent, whereas in the Nautiloidea, the external shell remains. About 800 living species of cephalopods have been identified. Two important extinct taxa are the Ammonoidea (ammonites) and Belemnoidea (belemnites). Extant cephalopods range in size from the 10 mm (0.3 in) Idiosepius thailandicus to the 700 kilograms (1,500 lb) heavy colossal squid, the largest extant invertebrate.