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Cephalopods are thought to be unable to live in fresh water due to multiple biochemical constraints, and in their >400 million year existence have never ventured into fully freshwater habitats. [10] Cephalopods occupy most of the depth of the ocean, from the abyssal plains to the sea surface, and have also been found in the hadal zone. [11]
Diagram of a cephalopod's photophore, in vertical section. A photophore is a glandular organ that appears as luminous spots on marine animals, including fish and cephalopods. The organ can be simple, or as complex as the human eye, equipped with lenses, shutters, color filters, and reflectors; unlike an eye, however, it is optimized to produce ...
Structure of a plant cell. Plant cells are the cells present in green plants, photosynthetic eukaryotes of the kingdom Plantae.Their distinctive features include primary cell walls containing cellulose, hemicelluloses and pectin, the presence of plastids with the capability to perform photosynthesis and store starch, a large vacuole that regulates turgor pressure, the absence of flagella or ...
Diagram of ammonite soft tissue anatomy based on other cephalopods along with a cross section (right). Note that shape and length of tentacles are speculative. Although ammonites do occur in exceptional lagerstatten such as the Solnhofen Limestone, their soft-part record is surprisingly sparse. Beyond a tentative ink sac and possible digestive ...
Chromatophores are cells that produce color, of which many types are pigment-containing cells, or groups of cells, found in a wide range of animals including amphibians, fish, reptiles, crustaceans and cephalopods. Mammals and birds, in contrast, have a class of cells called melanocytes for coloration.
Drawing of the statocyst system Statocysts (ss) and statolith (sl) inside the head of sea snail Gigantopelta chessoia. The statocyst is a balance sensory receptor present in some aquatic invertebrates, including bivalves, [1] cnidarians, [2] ctenophorans, [3] echinoderms, [4] cephalopods, [5] [6] crustaceans, [7] and gastropods, [8] A similar structure is also found in Xenoturbella. [9]
A siphon is an anatomical structure which is part of the body of aquatic molluscs in three classes: Gastropoda, Bivalvia and Cephalopoda (members of these classes include saltwater and freshwater snails, clams, octopus, squid and relatives). Siphons in molluscs are tube-like structures in which water (or, more rarely, air) flows.
The cephalopods were once thought to have evolved from a monoplacophoran-like ancestor [8] with a curved, tapering shell, [9] and to be closely related to the gastropods (snails). [10] The similarity of the early shelled cephalopod Plectronoceras to some gastropods was used to support this view.