98-438: " Monothalamea " Tubothalamea Globothalamea incertae sedis Foraminifera ( / f ə ˌ r æ m ə ˈ n ɪ f ə r ə / fə- RAM -ə- NIH -fə-rə ; Latin for "hole bearers"; informally called " forams ") are single-celled organisms , members of a phylum or class of Rhizarian protists characterized by streaming granular ectoplasm for catching food and other uses; and commonly an external shell (called
196-424: A " test ") of diverse forms and materials. Tests of chitin (found in some simple genera, and Textularia in particular) are believed to be the most primitive type. Most foraminifera are marine, the majority of which live on or within the seafloor sediment (i.e., are benthic , with different sized species playing a role within the macrobenthos , meiobenthos , and microbenthos ), while a smaller number float in
294-427: A "shell vestige" or "gladius". The Incirrina have either a pair of rod-shaped stylets or no vestige of an internal shell, and some squid also lack a gladius. The shelled coleoids do not form a clade or even a paraphyletic group. The Spirula shell begins as an organic structure, and is then very rapidly mineralized. Shells that are "lost" may be lost by resorption of the calcium carbonate component. Females of
392-399: A cloud of dark ink to confuse predators . This sac is a muscular bag which originated as an extension of the hindgut. It lies beneath the gut and opens into the anus, into which its contents – almost pure melanin – can be squirted; its proximity to the base of the funnel means the ink can be distributed by ejected water as the cephalopod uses its jet propulsion. The ejected cloud of melanin
490-451: A diversity of backgrounds. Experiments done in Dwarf chameleons testing these hypotheses showed that chameleon taxa with greater capacity for color change had more visually conspicuous social signals but did not come from more visually diverse habitats, suggesting that color change ability likely evolved to facilitate social signaling, while camouflage is a useful byproduct. Because camouflage
588-529: A flat fan shape with a mucus film between the individual tentacles, while another, Sepioteuthis sepioidea , has been observed putting the tentacles in a circular arrangement. Cephalopods have advanced vision, can detect gravity with statocysts , and have a variety of chemical sense organs. Octopuses use their arms to explore their environment and can use them for depth perception. Most cephalopods rely on vision to detect predators and prey and to communicate with one another. Consequently, cephalopod vision
686-652: A gunshot-like popping noise, thought to function to frighten away potential predators. Cephalopods employ a similar method of propulsion despite their increasing size (as they grow) changing the dynamics of the water in which they find themselves. Thus their paralarvae do not extensively use their fins (which are less efficient at low Reynolds numbers ) and primarily use their jets to propel themselves upwards, whereas large adult cephalopods tend to swim less efficiently and with more reliance on their fins. Early cephalopods are thought to have produced jets by drawing their body into their shells, as Nautilus does today. Nautilus
784-555: A host of larger organisms, including invertebrates, fish, shorebirds, and other foraminifera. It has been suggested, however, that in some cases predators may be more interested in the calcium from foram shells than in the organisms themselves. Several aquatic snail species are known to selectively feed upon foraminifera, often even preferring individual species. Certain benthic foraminifera have been found to be capable of surviving anoxic conditions for over 24 hours, indicating that they are capable of selective anaerobic respiration . This
882-453: A jet as a propulsion mechanism. Squids do not have the longitudinal muscles that octopus do. Instead, they have a tunic. This tunic is made of layers of collagen and it surrounds the top and the bottom of the mantle. Because they are made of collagen and not muscle, the tunics are rigid bodies that are much stronger than the muscle counterparts. This provides the squids some advantages for jet propulsion swimming. The stiffness means that there
980-406: A length of 8 metres. They may terminate in a broadened, sucker-coated club. The shorter four pairs are termed arms , and are involved in holding and manipulating the captured organism. They too have suckers, on the side closest to the mouth; these help to hold onto the prey. Octopods only have four pairs of sucker-coated arms, as the name suggests, though developmental abnormalities can modify
1078-673: A major group within the Protozoa known as the Rhizaria . Prior to the recognition of evolutionary relationships among the members of the Rhizaria, the Foraminifera were generally grouped with other amoeboids as phylum Rhizopodea (or Sarcodina) in the class Granuloreticulosa. The Rhizaria are problematic, as they are often called a "supergroup", rather than using an established taxonomic rank such as phylum . Cavalier-Smith defines
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#17327834008371176-474: A muscle, which is why they can change their skin hue as rapidly as they do. Coloration is typically stronger in near-shore species than those living in the open ocean, whose functions tend to be restricted to disruptive camouflage . These chromatophores are found throughout the body of the octopus, however, they are controlled by the same part of the brain that controls elongation during jet propulsion to reduce drag. As such, jetting octopuses can turn pale because
1274-464: A nerve tube. Alcide d'Orbigny , in his 1826 work, considered them to be a group of minute cephalopods and noted their odd morphology, interpreting the pseudopodia as tentacles and noting the highly reduced (in actuality, absent) head. He named the group foraminifères , or "hole-bearers", as members of the group had holes in the divisions between compartments in their shells, in contrast to nautili or ammonites . The protozoan nature of foraminifera
1372-512: A novel mechanism for spectral discrimination in cephalopods was described. This relies on the exploitation of chromatic aberration (wavelength-dependence of focal length). Numerical modeling shows that chromatic aberration can yield useful chromatic information through the dependence of image acuity on accommodation. The unusual off-axis slit and annular pupil shapes in cephalopods enhance this ability by acting as prisms which are scattering white light in all directions. In 2015, molecular evidence
1470-471: A rare form of physiological color change which utilizes neural control of muscles to change the morphology of their chromatophores. This neural control of chromatophores has evolved convergently in both cephalopods and teleosts fishes. With the exception of the Nautilidae and the species of octopus belonging to the suborder Cirrina , all known cephalopods have an ink sac, which can be used to expel
1568-429: A shell-less subclass of cephalopods (squid, cuttlefish, and octopuses), have complex pigment containing cells called chromatophores which are capable of producing rapidly changing color patterns. These cells store pigment within an elastic sac which produces the color seen from these cells. Coleoids can change the shape of this sac, called the cytoelastic sacculus, which then causes changes in the translucency and opacity of
1666-399: A single opening or through many perforations in the test. Individual pseudopods characteristically have small granules streaming in both directions. Foraminifera are unique in having granuloreticulose pseudopodia ; that is, their pseudopodia appear granular under the microscope; these pseudopodia are often elongate and may split and rejoin each other. These can be extended and retracted to suit
1764-620: A startling array of fashions. As well as providing camouflage with their background, some cephalopods bioluminesce, shining light downwards to disguise their shadows from any predators that may lurk below. The bioluminescence is produced by bacterial symbionts; the host cephalopod is able to detect the light produced by these organisms. Bioluminescence may also be used to entice prey, and some species use colorful displays to impress mates, startle predators, or even communicate with one another. Cephalopods can change their colors and patterns in milliseconds, whether for signalling (both within
1862-539: 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
1960-482: Is a grouping of foraminiferans , traditionally consisting of all foraminifera with single-chambered tests . Recent work has shown that the grouping is paraphyletic , and as such does not constitute a natural group; nonetheless, the name "monothalamea" continues to be used by foraminifera workers out of convenience. "Monothalamea" traditionally contains two groups, neither of which is currently considered to be monophyletic : Recent molecular evidence has revealed that
2058-698: 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 . There are over 800 extant species of cephalopod, although new species continue to be described. An estimated 11,000 extinct taxa have been described, although
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#17327834008372156-516: Is acute: training experiments have shown that the common octopus can distinguish the brightness, size, shape, and horizontal or vertical orientation of objects. The morphological construction gives cephalopod eyes the same performance as shark eyes; however, their construction differs, as cephalopods lack a cornea and have an everted retina. Cephalopods' eyes are also sensitive to the plane of polarization of light. Unlike many other cephalopods, nautiluses do not have good vision; their eye structure
2254-463: Is also capable of creating a jet by undulations of its funnel; this slower flow of water is more suited to the extraction of oxygen from the water. When motionless, Nautilus can only extract 20% of oxygen from the water. The jet velocity in Nautilus is much slower than in coleoids , but less musculature and energy is involved in its production. Jet thrust in cephalopods is controlled primarily by
2352-447: Is also common in the group, and at least some species can take advantage of dissolved organic carbon . A few foram species are parasitic , infecting sponges, molluscs, corals, or even other foraminifera. Parasitic strategies vary; some act as ectoparasites, using their pseudopodia to steal food from the host, while others burrow through the shell or body wall of their host to feed on its soft tissue. Foraminifera are themselves eaten by
2450-546: Is any member of the molluscan class Cephalopoda / s ɛ f ə ˈ l ɒ p ə d ə / ( Greek plural κεφαλόποδες , kephalópodes ; "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
2548-570: Is aragonite. As for other mollusc shells or coral skeletons, the smallest visible units are irregular rounded granules. Cephalopods, as the name implies, have muscular appendages extending from their heads and surrounding their mouths. These are used in feeding, mobility, and even reproduction. In coleoids they number eight or ten. Decapods such as cuttlefish and squid have five pairs. The longer two, termed tentacles , are actively involved in capturing prey; they can lengthen rapidly (in as little as 15 milliseconds ). In giant squid they may reach
2646-427: Is highly developed, but lacks a solid lens . They have a simple " pinhole " eye through which water can pass. Instead of vision, the animal is thought to use olfaction as the primary sense for foraging , as well as locating or identifying potential mates. All octopuses and most cephalopods are considered to be color blind . Coleoid cephalopods (octopus, squid, cuttlefish) have a single photoreceptor type and lack
2744-549: Is interpreted as an adaptation to survive changing oxygenic conditions near the sediment-water interface. Foraminifera are found in the deepest parts of the ocean such as the Mariana Trench , including the Challenger Deep , the deepest part known. At these depths, below the carbonate compensation depth , the calcium carbonate of the tests is soluble in water due to the extreme pressure. The Foraminifera found in
2842-418: Is more efficient, but in environments with little oxygen and in low temperatures, hemocyanin has the upper hand. The hemocyanin molecule is much larger than the hemoglobin molecule, allowing it to bond with 96 O 2 or CO 2 molecules, instead of the hemoglobin's just four. But unlike hemoglobin, which are attached in millions on the surface of a single red blood cell, hemocyanin molecules float freely in
2940-403: Is needed, compensating for their small size. However, organisms which spend most of their time moving slowly along the bottom do not naturally pass much water through their cavity for locomotion; thus they have larger gills, along with complex systems to ensure that water is constantly washing through their gills, even when the organism is stationary. The water flow is controlled by contractions of
3038-439: Is no necessary muscle flexing to keep the mantle the same size. In addition, tunics take up only 1% of the squid mantle's wall thickness, whereas the longitudinal muscle fibers take up to 20% of the mantle wall thickness in octopuses. Also because of the rigidity of the tunic, the radial muscles in squid can contract more forcefully. The mantle is not the only place where squids have collagen. Collagen fibers are located throughout
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3136-413: Is recognizable as being Elphidium . Early workers classified foraminifera within the genus Nautilus , noting their similarity to certain cephalopods . It was recognised by Lorenz Spengler in 1781 that foraminifera had holes in the septa, which would eventually grant the group its name. Spengler also noted that the septa of foraminifera arced the opposite way from those of nautili and that they lacked
3234-457: Is referred to as a pseudomorph ). This strategy often results in the predator attacking the pseudomorph, rather than its rapidly departing prey. For more information, see Inking behaviors . The ink sac of cephalopods has led to a common name of "inkfish", formerly the pen-and-ink fish. Cephalopods are the only molluscs with a closed circulatory system. Coleoids have two gill hearts (also known as branchial hearts ) that move blood through
3332-413: Is supplemented with fin motion; in the squid, the fins flap each time that a jet is released, amplifying the thrust; they are then extended between jets (presumably to avoid sinking). Oxygenated water is taken into the mantle cavity to the gills and through muscular contraction of this cavity, the spent water is expelled through the hyponome , created by a fold in the mantle. The size difference between
3430-553: Is the first evidence that cephalopod dermal tissues may possess the required combination of molecules to respond to light. Some squids have been shown to detect sound using their statocysts , but, in general, cephalopods are deaf. Most cephalopods possess an assemblage of skin components that interact with light. These may include iridophores, leucophores , chromatophores and (in some species) photophores . Chromatophores are colored pigment cells that expand and contract in accordance to produce color and pattern which they can use in
3528-423: Is the most complex of the invertebrates and their brain-to-body-mass ratio falls between that of endothermic and ectothermic vertebrates. Captive cephalopods have also been known to climb out of their aquaria, maneuver a distance of the lab floor, enter another aquarium to feed on captive crabs, and return to their own aquarium. The brain is protected in a cartilaginous cranium. The giant nerve fibers of
3626-426: Is unknown, but chromatophores are under the control of neural pathways, allowing the cephalopod to coordinate elaborate displays. Together, chromatophores and iridophores are able to produce a large range of colors and pattern displays. Cephalopods utilize chromatophores' color changing ability in order to camouflage themselves. Chromatophores allow Coleoids to blend into many different environments, from coral reefs to
3724-400: Is used for multiple adaptive purposes in cephalopods, color change could have evolved for one use and the other developed later, or it evolved to regulate trade offs within both. Color change is widespread in ectotherms including anoles, frogs, mollusks, many fish, insects, and spiders. The mechanism behind this color change can be either morphological or physiological. Morphological change is
3822-417: Is usually mixed, upon expulsion, with mucus , produced elsewhere in the mantle, and therefore forms a thick cloud, resulting in visual (and possibly chemosensory) impairment of the predator, like a smokescreen . However, a more sophisticated behavior has been observed, in which the cephalopod releases a cloud, with a greater mucus content, that approximately resembles the cephalopod that released it (this decoy
3920-527: The green algae , red algae , golden algae , diatoms , and dinoflagellates . These mixotrophic foraminifers are particularly common in nutrient-poor oceanic waters. Some forams are kleptoplastic , retaining chloroplasts from ingested algae to conduct photosynthesis . Most foraminifera are heterotrophic, consuming smaller organisms and organic matter; some smaller species are specialised feeders on phytodetritus , while others specialise in consuming diatoms. Some benthic forams construct feeding cysts, using
4018-488: The largest species reaching up to 20 cm. In modern scientific English, the term foraminifera is both singular and plural (irrespective of the word's Latin derivation), and is used to describe one or more specimens or taxa: its usage as singular or plural must be determined from context. Foraminifera is frequently used informally to describe the group, and in these cases is generally lowercase. The earliest known reference to foraminifera comes from Herodotus , who in
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4116-583: The sparkling enope squid ( Watasenia scintillans ). It achieves color vision with three photoreceptors , which are based on the same opsin , but use distinct retinal molecules as chromophores: A1 (retinal), A3 (3-dehydroretinal), and A4 (4-hydroxyretinal). The A1-photoreceptor is most sensitive to green-blue (484 nm), the A2-photoreceptor to blue-green (500 nm), and the A4-photoreceptor to blue (470 nm) light. In 2015,
4214-520: The 5th century BCE noted them as making up the rock that forms the Great Pyramid of Giza . These are today recognized as representatives of the genus Nummulites . Strabo , in the 1st Century BCE, noted the same foraminifera, and suggested that they were the remains of lentils left by the workers who built the pyramids. Robert Hooke observed a foraminifera under the microscope, as described and illustrated in his 1665 book Micrographia : I
4312-505: The Challenger Deep thus have no carbonate test, but instead have one of organic material. Nonmarine foraminifera have traditionally been neglected in foram research, but recent studies show them to be substantially more diverse than previously known. They are known to inhabit disparate ecological niches, including mosses , rivers, lakes and ponds, wetlands, soils, peat bogs , and sand dunes. Monothalamea "Monothalamea"
4410-472: The Foraminifera has varied since Schultze in 1854, who referred to as an order, Foraminiferida. Loeblich (1987) and Tappan (1992) reranked Foraminifera as a class as it is now commonly regarded. The Foraminifera have typically been included in the Protozoa , or in the similar Protoctista or Protist kingdom . Compelling evidence, based primarily on molecular phylogenetics , exists for their belonging to
4508-509: The Rhizaria as an infra-kingdom within the kingdom Protozoa. Some taxonomies put the Foraminifera in a phylum of their own, putting them on par with the amoeboid Sarcodina in which they had been placed. Although as yet unsupported by morphological correlates, molecular data strongly suggest the Foraminifera are closely related to the Cercozoa and Radiolaria , both of which also include amoeboids with complex shells; these three groups make up
4606-520: The Rhizaria. However, the exact relationships of the forams to the other groups and to one another are still not entirely clear. Foraminifera are closely related to testate amoebae . The most striking aspect of most foraminifera are their hard shells, or tests. These may consist of one of multiple chambers, and may be composed of protein, sediment particles, calcite, aragonite, or (in one case) silica. Some foraminifera lack tests entirely. Unlike other shell-secreting organisms, such as molluscs or corals ,
4704-556: The ability to determine color by comparing detected photon intensity across multiple spectral channels. When camouflaging themselves, they use their chromatophores to change brightness and pattern according to the background they see, but their ability to match the specific color of a background may come from cells such as iridophores and leucophores that reflect light from the environment. They also produce visual pigments throughout their body and may sense light levels directly from their body. Evidence of color vision has been found in
4802-452: The acidity of the organic shell matrix (see Mollusc shell ); shell-forming cephalopods have an acidic matrix, whereas the gladius of squid has a basic matrix. The basic arrangement of the cephalopod outer wall is: an outer (spherulitic) prismatic layer, a laminar (nacreous) layer and an inner prismatic layer. The thickness of every layer depends on the taxa. In modern cephalopods, the Ca carbonate
4900-434: The air for distances of up to 50 metres (160 ft). While cephalopods are not particularly aerodynamic, they achieve these impressive ranges by jet-propulsion; water continues to be expelled from the funnel while the organism is in the air. The animals spread their fins and tentacles to form wings and actively control lift force with body posture. One species, Todarodes pacificus , has been observed spreading tentacles in
4998-454: The appearance of their surroundings is notable given that cephalopods' vision is monochromatic. Cephalopods also use their fine control of body coloration and patterning to perform complex signaling displays for both conspecific and intraspecific communication. Coloration is used in concert with locomotion and texture to send signals to other organisms. Intraspecifically this can serve as a warning display to potential predators. For example, when
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#17327834008375096-403: The bloodstream. Cephalopods exchange gases with the seawater by forcing water through their gills, which are attached to the roof of the organism. Water enters the mantle cavity on the outside of the gills, and the entrance of the mantle cavity closes. When the mantle contracts, water is forced through the gills, which lie between the mantle cavity and the funnel. The water's expulsion through
5194-517: The body cavity; others, like some fish, accumulate oils in the liver; and some octopuses have a gelatinous body with lighter chloride ions replacing sulfate in the body chemistry. Squids are the primary sufferers of negative buoyancy in cephalopods. The negative buoyancy means that some squids, especially those whose habitat depths are rather shallow, have to actively regulate their vertical positions. This means that they must expend energy, often through jetting or undulations, in order to maintain
5292-582: The brain is unable to achieve both controlling elongation and controlling the chromatophores. Most octopuses mimic select structures in their field of view rather than becoming a composite color of their full background. Evidence of original coloration has been detected in cephalopod fossils dating as far back as the Silurian ; these orthoconic individuals bore concentric stripes, which are thought to have served as camouflage. Devonian cephalopods bear more complex color patterns, of unknown function. Coleoids,
5390-401: The capillaries of the gills . A single systemic heart then pumps the oxygenated blood through the rest of the body. Like most molluscs, cephalopods use hemocyanin , a copper-containing protein, rather than hemoglobin , to transport oxygen. As a result, their blood is colorless when deoxygenated and turns blue when bonded to oxygen. In oxygen-rich environments and in acidic water, hemoglobin
5488-436: The cavity by entering not only through the orifices, but also through the funnel. Squid can expel up to 94% of the fluid within their cavity in a single jet thrust. To accommodate the rapid changes in water intake and expulsion, the orifices are highly flexible and can change their size by a factor of twenty; the funnel radius, conversely, changes only by a factor of around 1.5. Some octopus species are also able to walk along
5586-561: The cell. By rapidly changing multiple chromatophores of different colors, cephalopods are able to change the color of their skin at astonishing speeds, an adaptation that is especially notable in an organism that sees in black and white. Chromatophores are known to only contain three pigments, red, yellow, and brown, which cannot create the full color spectrum. However, cephalopods also have cells called iridophores, thin, layered protein cells that reflect light in ways that can produce colors chromatophores cannot. The mechanism of iridophore control
5684-399: The cephalopod mantle have been widely used for many years as experimental material in neurophysiology ; their large diameter (due to lack of myelination ) makes them relatively easy to study compared with other animals. Many cephalopods are social creatures; when isolated from their own kind, some species have been observed shoaling with fish. Some cephalopods are able to fly through
5782-587: The deep-sea xenophyophores are in fact agglutinated, single-chambered foraminifera. Molecular evidence has also revealed that the freshwater protist Reticulomyxa is in fact a naked, testless foraminifera, and as such it has been included with "monothalameans" in scientific discussion. A 2013 molecular study using small subunit rDNA concluded that known "monothalameans" made up at least 22 distinct living clades from marine environments with an additional four clades from freshwater eDNA . Cephalopod A cephalopod / ˈ s ɛ f ə l ə p ɒ d /
5880-491: The depth of the ocean, from the abyssal plains to the sea surface, and have also been found in the hadal zone . Their diversity is greatest near the equator (~40 species retrieved in nets at 11°N by a diversity study) and decreases towards the poles (~5 species captured at 60°N). Cephalopods are widely regarded as the most intelligent of the invertebrates and have well developed senses and large brains (larger than those of gastropods ). The nervous system of cephalopods
5978-791: The dominant scheme of classification until Tappan and Loeblich's 1964 classification, which placed foraminifera into the general groupings still used today, based on microstructure of the test wall. These groups have been variously moved around according to different schemes of higher-level classification. Pawlowski's (2013) use of molecular systematics has generally confirmed Tappan and Loeblich's groupings, with some being found as polyphyletic or paraphyletic; this work has also helped to identify higher-level relationships among major foraminiferal groups. "Monothalamids" (paraphyletic) Lagenida "Monothalamids" Miliolida Spirillinida "Monothalamids" Xenophyophorea " Textulariida " (paraphyletic) Robertinida Rotaliida The taxonomic position of
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#17327834008376076-488: The exact purpose of these is unclear, but they have been suggested to function as a reservoir of nitrate. Mitochondria are distributed evenly throughout the cell, though in some species they are concentrated under the pores and around the external margin of the cell. This has been hypothesised to be an adaptation to low-oxygen environments. Several species of xenophyophore have been found to have unusually high concentrations of radioactive isotopes within their cells, among
6174-469: The expansion of the mantle at the end of the jet. In some tests, the collagen has been shown to be able to begin raising mantle pressure up to 50ms before muscle activity is initiated. These anatomical differences between squid and octopuses can help explain why squid can be found swimming comparably to fish while octopuses usually rely on other forms of locomotion on the sea floor such as bipedal walking, crawling, and non-jetting swimming. Nautiluses are
6272-413: The form of jetting. The composition of these mantles differs between the two families, however. In octopuses, the mantle is made up of three muscle types: longitudinal, radial, and circular. The longitudinal muscles run parallel to the length of the octopus and they are used in order to keep the mantle the same length throughout the jetting process. Given that they are muscles, it can be noted that this means
6370-456: The funnel can be used to power jet propulsion. If respiration is used concurrently with jet propulsion, large losses in speed or oxygen generation can be expected. The gills, which are much more efficient than those of other mollusks, are attached to the ventral surface of the mantle cavity. There is a trade-off with gill size regarding lifestyle. To achieve fast speeds, gills need to be small – water will be passed through them quickly when energy
6468-661: The highest of any eukaryote. The purpose of this is unknown. Modern Foraminifera are primarily marine organisms, but living individuals have been found in brackish, freshwater and even terrestrial habitats. The majority of the species are benthic , and a further 50 morphospecies are planktonic . This count may, however, represent only a fraction of actual diversity, since many genetically distinct species may be morphologically indistinguishable. Benthic foraminifera are typically found in fine-grained sediments, where they actively move between layers; however, many species are found on hard rock substrates, attached to seaweeds, or sitting atop
6566-728: The idea that multiple different characters must separate taxonomic groups, and as such placed agglutinated and calcareous genera in close relation. This overall scheme of classification would remain until Cushman 's work in the late 1920s. Cushman viewed wall composition as the single most important trait in classification of foraminifera; his classification became widely accepted but also drew criticism from colleagues for being "not biologically sound". Geologist Irene Crespin undertook extensive research in this field, publishing some ninety papers—including notable work on foraminifera—as sole author as well as more than twenty in collaboration with other scientists. Cushman's scheme nevertheless remained
6664-472: The maximum diameter of the funnel orifice (or, perhaps, the average diameter of the funnel) and the diameter of the mantle cavity. Changes in the size of the orifice are used most at intermediate velocities. The absolute velocity achieved is limited by the cephalopod's requirement to inhale water for expulsion; this intake limits the maximum velocity to eight body-lengths per second, a speed which most cephalopods can attain after two funnel-blows. Water refills
6762-468: The needs of the cell. The pseudopods are used for locomotion, anchoring, excretion, test construction and in capturing food, which consists of small organisms such as diatoms or bacteria. Aside from the tests, foraminiferal cells are supported by a cytoskeleton of microtubules, which are loosely arranged without the structure seen in other amoeboids. Forams have evolved special cellular mechanisms to quickly assemble and disassemble microtubules, allowing for
6860-404: The non threatening herbivorous parrotfish to approach unaware prey. The octopus Thaumoctopus mimicus is known to mimic a number of different venomous organisms it cohabitates with to deter predators. While background matching, a cephalopod changes its appearance to resemble its surroundings, hiding from its predators or concealing itself from prey. The ability to both mimic other organisms and match
6958-413: The octopus Callistoctopus macropus is threatened, it will turn a bright red brown color speckled with white dots as a high contrast display to startle predators. Conspecifically, color change is used for both mating displays and social communication. Cuttlefish have intricate mating displays from males to females. There is also male to male signaling that occurs during competition over mates, all of which are
7056-443: The octopus genus Argonauta secrete a specialized paper-thin egg case in which they reside, and this is popularly regarded as a "shell", although it is not attached to the body of the animal and has a separate evolutionary origin. The largest group of shelled cephalopods, the ammonites , are extinct, but their shells are very common as fossils . The deposition of carbonate, leading to a mineralized shell, appears to be related to
7154-444: The octopus must actively flex the longitudinal muscles during jetting in order to keep the mantle at a constant length. The radial muscles run perpendicular to the longitudinal muscles and are used to thicken and thin the wall of the mantle. Finally, the circular muscles are used as the main activators in jetting. They are muscle bands that surround the mantle and expand/contract the cavity. All three muscle types work in unison to produce
7252-497: The only extant cephalopods with a true external shell. However, all molluscan shells are formed from the ectoderm (outer layer of the embryo); in cuttlefish ( Sepia spp.), for example, an invagination of the ectoderm forms during the embryonic period, resulting in a shell ( cuttlebone ) that is internal in the adult. The same is true of the chitinous gladius of squid and octopuses. Cirrate octopods have arch-shaped cartilaginous fin supports , which are sometimes referred to as
7350-440: The other muscle fibers in the mantle. These collagen fibers act as elastics and are sometimes named "collagen springs". As the name implies, these fibers act as springs. When the radial and circular muscles in the mantle contract, they reach a point where the contraction is no longer efficient to the forward motion of the creature. In such cases, the excess contraction is stored in the collagen which then efficiently begins or aids in
7448-442: The posterior and anterior ends of this organ control the speed of the jet the organism can produce. The velocity of the organism can be accurately predicted for a given mass and morphology of animal. Motion of the cephalopods is usually backward as water is forced out anteriorly through the hyponome, but direction can be controlled somewhat by pointing it in different directions. Some cephalopods accompany this expulsion of water with
7546-407: The product of chromatophore coloration displays. There are two hypotheses about the evolution of color change in cephalopods. One hypothesis is that the ability to change color may have evolved for social, sexual, and signaling functions. Another explanation is that it first evolved because of selective pressures encouraging predator avoidance and stealth hunting. For color change to have evolved as
7644-421: The pseuodopodia to encyst themselves inside of sediment and organic particles. Certain foraminifera prey upon small animals such as copepods or cumaceans ; some forams even predate upon other forams, drilling holes into the tests of their prey. One group, the xenophyophores, has been suggested to farm bacteria within their tests, although studies have failed to find support for this hypothesis. Suspension feeding
7742-431: The radial and circular mantle cavity muscles. The gills of cephalopods are supported by a skeleton of robust fibrous proteins; the lack of mucopolysaccharides distinguishes this matrix from cartilage. The gills are also thought to be involved in excretion, with NH 4 being swapped with K from the seawater. While most cephalopods can move by jet propulsion, this is a very energy-consuming way to travel compared to
7840-662: The rapid formation and retraction of elongated pseudopodia. In the gamont (sexual form), foraminifera generally have only a single nucleus, while the agamont (asexual form) tends to have multiple nuclei. In at least some species the nuclei are dimorphic, with the somatic nuclei containing three times as much protein and RNA than the generative nuclei. However, nuclear anatomy seems to be highly diverse. The nuclei are not necessarily confined to one chamber in multi-chambered species. Nuclei can be spherical or have many lobes. Nuclei are typically 30-50 μm in diameter. Some species of foraminifera have large, empty vacuoles within their cells;
7938-441: The result of a change in the density of pigment containing cells and tends to change over longer periods of time. Physiological change, the kind observed in cephalopod lineages, is typically the result of the movement of pigment within the chromatophore, changing where different pigments are localized within the cell. This physiological change typically occurs on much shorter timescales compared to morphological change. Cephalopods have
8036-439: The result of natural selection different parameters would have to be met. For one, you would need some phenotypic diversity in body patterning among the population. The species would also need to cohabitate with predators which rely on vision for prey identification. These predators should have a high range of visual sensitivity, detecting not just motion or contrast but also colors. The habitats they occupy would also need to display
8134-424: The result of social selection the environment of cephalopods' ancestors would have to fit a number of criteria. One, there would need to be some kind of mating ritual that involved signaling. Two, they would have to experience demonstrably high levels of sexual selection. And three, the ancestor would need to communicate using sexual signals that are visible to a conspecific receiver. For color change to have evolved as
8232-549: The same class. Octopuses are generally not seen as active swimmers; they are often found scavenging the sea floor instead of swimming long distances through the water. Squids, on the other hand, can be found to travel vast distances, with some moving as much as 2000 km in 2.5 months at an average pace of 0.9 body lengths per second. There is a major reason for the difference in movement type and efficiency: anatomy. Both octopuses and squids have mantles (referenced above) which function towards respiration and locomotion in
8330-399: The same depth. As such, the cost of transport of many squids are quite high. That being said, squid and other cephalopod that dwell in deep waters tend to be more neutrally buoyant which removes the need to regulate depth and increases their locomotory efficiency. The Macrotritopus defilippi , or the sand-dwelling octopus, was seen mimicking both the coloration and the swimming movements of
8428-452: The sand-dwelling flounder Bothus lunatus to avoid predators. The octopuses were able to flatten their bodies and put their arms back to appear the same as the flounders as well as move with the same speed and movements. Females of two species, Ocythoe tuberculata and Haliphron atlanticus , have evolved a true swim bladder . Two of the categories of cephalopods, octopus and squid, are vastly different in their movements despite being of
8526-446: The sandy sea floor. The color change of chromatophores works in concert with papillae, epithelial tissue which grows and deforms through hydrostatic motion to change skin texture. Chromatophores are able to perform two types of camouflage, mimicry and color matching. Mimicry is when an organism changes its appearance to appear like a different organism. The squid Sepioteuthis sepioide has been documented changing its appearance to appear as
8624-489: The seabed. Squids and cuttlefish can move short distances in any direction by rippling of a flap of muscle around the mantle. While most cephalopods float (i.e. are neutrally buoyant or nearly so; in fact most cephalopods are about 2–3% denser than seawater ), they achieve this in different ways. Some, such as Nautilus , allow gas to diffuse into the gap between the mantle and the shell; others allow purer water to ooze from their kidneys, forcing out denser salt water from
8722-555: The sediment surface. The majority of planktonic foraminifera are found in the globigerinina , a lineage within the rotaliida . However, at least one other extant rotaliid lineage, Neogallitellia , seems to have independently evolved a planktonic lifestyle. Further, it has been suggested that some Jurassic fossil foraminifera may have also independently evolved a planktonic lifestyle, and may be members of Robertinida. A number of forams, both benthic and planktonic, have unicellular algae as endosymbionts , from diverse lineages such as
8820-608: The soft-bodied nature of cephalopods means they are not easily fossilised. Cephalopods are found in all the oceans of Earth. None of them can tolerate fresh water , but the brief squid, Lolliguncula brevis , found in Chesapeake Bay , is a notable partial exception in that it tolerates brackish water . 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. Cephalopods occupy most of
8918-440: The species and for warning ) or active camouflage , as their chromatophores are expanded or contracted. Although color changes appear to rely primarily on vision input, there is evidence that skin cells, specifically chromatophores , can detect light and adjust to light conditions independently of the eyes. The octopus changes skin color and texture during quiet and active sleep cycles. Cephalopods can use chromatophores like
9016-459: The tail propulsion used by fish. The efficiency of a propeller -driven waterjet (i.e. Froude efficiency ) is greater than a rocket . The relative efficiency of jet propulsion decreases further as animal size increases; paralarvae are far more efficient than juvenile and adult individuals. Since the Paleozoic era , as competition with fish produced an environment where efficient motion
9114-416: The tests of foraminifera are located inside the cell membrane , within the protoplasm . The organelles of the cell are located within the compartment(s) of the test, and the hole(s) of the test allow the transfer of material from the pseudopodia to the internal cell and back. The foraminiferal cell is divided into granular endoplasm and transparent ectoplasm from which a pseudopodial net may emerge through
9212-701: The water column at various depths (i.e., are planktonic ), which belong to the suborder Globigerinina . Fewer are known from freshwater or brackish conditions, and some very few (nonaquatic) soil species have been identified through molecular analysis of small subunit ribosomal DNA . Foraminifera typically produce a test , or shell, which can have either one or multiple chambers, some becoming quite elaborate in structure. These shells are commonly made of calcium carbonate ( CaCO 3 ) or agglutinated sediment particles. Over 50,000 species are recognized, both living (6,700–10,000) and fossil (40,000). They are usually less than 1 mm in size, but some are much larger,
9310-463: Was crucial to survival, jet propulsion has taken a back role, with fins and tentacles used to maintain a steady velocity. Whilst jet propulsion is never the sole mode of locomotion, the stop-start motion provided by the jets continues to be useful for providing bursts of high speed – not least when capturing prey or avoiding predators . Indeed, it makes cephalopods the fastest marine invertebrates, and they can out-accelerate most fish. The jet
9408-517: Was first recognized by Dujardin in 1835. Shortly after, in 1852, d'Orbigny produced a classification scheme, recognising 72 genera of foraminifera, which he classified based on test shape—a scheme that drew severe criticism from colleagues. H.B. Brady 's 1884 monograph described the foraminiferal finds of the Challenger expedition . Brady recognized 10 families with 29 subfamilies, with little regard to stratigraphic range; his taxonomy emphasized
9506-401: Was published indicating that cephalopod chromatophores are photosensitive; reverse transcription polymerase chain reactions (RT-PCR) revealed transcripts encoding rhodopsin and retinochrome within the retinas and skin of the longfin inshore squid ( Doryteuthis pealeii ), and the common cuttlefish ( Sepia officinalis ) and broadclub cuttlefish ( Sepia latimanus ). The authors claim this
9604-532: Was trying several small and single Magnifying Glasses, and casually viewing a parcel of white Sand, when I perceiv'd one of the grains exactly shap'd and wreath'd like a Shell[...] I view'd it every way with a better Microscope and found it on both sides, and edge-ways, to resemble the Shell of a small Water-Snail with a flat spiral Shell[...] Antonie van Leeuwenhoek described and illustrated foraminiferal tests in 1700, describing them as minute cockles; his illustration
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