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102-504: Siphonophorae (from Greek siphōn 'tube' + pherein 'to bear') is an order within Hydrozoa , which is a class of marine organisms within the phylum Cnidaria . According to the World Register of Marine Species , the order contains 175 species described thus far. Siphonophores are highly polymorphic and complex organisms. Although they may appear to be individual organisms, each specimen

204-518: A metachronal rhythm . This means the deformation of one cilium is in phase with the deformation of its neighbor, causing deformation waves that propagate along the surface of the organism. These propagating waves of cilia are what allow the organism to use the cilia in a coordinated manner to move. A typical example of a ciliated microorganism is the Paramecium , a one-celled, ciliated protozoan covered by thousands of cilia. The cilia beating together allow

306-467: A budding process. Zooids are the multicellular units that build the colonies. A single bud called the pro-bud initiates the growth of a colony by undergoing fission. Each zooid is produced to be genetically identical; however, mutations can alter their functions and increase diversity of the zooids within the colony. Siphonophores are unique in that the pro-bud initiates the production of diverse zooids with specific functions. The functions and organizations of

408-507: A colony can vary among species. Species are characterized as monoecious or dioecious based on their gonophores. Monoecious species contain male and female gonophores in a single zooid colony, whereas dioecious species harbor male and female gonophores separately in different colonies of zooids. Nearly all siphonophores have bioluminescent capabilities. Since these organisms are extremely fragile, they are rarely observed alive. Bioluminescence in siphonophores has been thought to have evolved as

510-420: A colony of zooids forms around the central stalk. In contrast, several species reproduce using polyps . Polyps can hold eggs and/or sperm and can be released into the water from the posterior end of the siphonophore. The polyps may then be fertilized outside of the organism. Siphonophores use gonophores to make the reproductive gametes . Gonophores are either male or female; however, the types of gonophores in

612-450: A counteracting upward force while thrusting the shark forward. The lift generated is assisted by the pectoral fins and upward-angle body positioning. It is supposed that tunas primarily use their pectoral fins for lift. Buoyancy maintenance is metabolically expensive. Growing and sustaining a buoyancy organ, adjusting the composition of biological makeup, and exerting physical strain to stay in motion demands large amounts of energy. It

714-456: A crustacean, swims by beating its antennae instead. There are also a number of forms of swimming molluscs . Many free-swimming sea slugs , such as sea angels , flap fin-like structures. Some shelled molluscs, such as scallops can briefly swim by clapping their two shells open and closed. The molluscs most evolved for swimming are the cephalopods . Violet sea-snails exploit a buoyant foam raft stabilized by amphiphilic mucins to float at

816-412: A defense mechanism. Siphonophores of the deep-sea genus Erenna (found at depths between 1,600–2,300 metres or 5,200–7,500 feet) are thought to use their bioluminescent capability for offense too, as a lure to attract fish. This genus is one of the few to prey on fish rather than crustaceans. The bioluminescent organs, called tentilla , on these non-visual individuals emit red fluorescence along with

918-457: A desired location. In bilateria , there are many methods of swimming. The arrow worms ( chaetognatha ) undulate their finned bodies, not unlike fish. Nematodes swim by undulating their fin-less bodies. Some Arthropod groups can swim – including many crustaceans . Most crustaceans, such as shrimp , will usually swim by paddling with special swimming legs ( pleopods ). Swimming crabs swim with modified walking legs ( pereiopods ). Daphnia ,

1020-478: A different position. There are no hard rules that a taxonomist needs to follow in describing or recognizing an order. Some taxa are accepted almost universally, while others are recognized only rarely. The name of an order is usually written with a capital letter. For some groups of organisms, their orders may follow consistent naming schemes . Orders of plants , fungi , and algae use the suffix -ales (e.g. Dictyotales ). Orders of birds and fishes use

1122-445: A large opening at low velocity. Because of this, the negative pressure created by the vibrating cavity is lower than the positive pressure of the jet, meaning that inertial work of the mantle is small. Thus, jet-propulsion is shown as an inefficient swimming technique. Many fish swim through water by creating undulations with their bodies or oscillating their fins . The undulations create components of forward thrust complemented by

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1224-452: A layer of muscle sandwiched between elastic fibers. The muscle fibers run around the bell circumferentially while the elastic fibers run through the muscle and along the sides of the bell to prevent lengthening. After making a single contraction, the bell vibrates passively at the resonant frequency to refill the bell. However, in contrast with scallops, the inertial work is similar to the hydrodynamic work due to how medusas expel water – through

1326-418: A lessened efficiency in swimming due to resistance which affects their optimum speed. The less drag a fish experiences, the more it will be able to maintain higher speeds. Morphology of the fish can be designed to reduce drag, such as streamlining the body. The cost of transport is much higher for the drag swimmer, and when deviating from its optimum speed, the drag swimmer is energetically strained much more than

1428-564: A number of times in unrelated lineages. Supposed jellyfish fossils occur in the Ediacaran , but the first free-swimming animals appear in the Early to Middle Cambrian . These are mostly related to the arthropods , and include the Anomalocaridids , which swam by means of lateral lobes in a fashion reminiscent of today's cuttlefish . Cephalopods joined the ranks of the active swimmers ( nekton ) in

1530-448: A rearward force, side forces which are wasted portions of energy, and a normal force that is between the forward thrust and side force. Different fish swim by undulating different parts of their bodies. Eel-shaped fish undulate their entire body in rhythmic sequences. Streamlined fish, such as salmon, undulate the caudal portions of their bodies. Some fish, such as sharks, use stiff, strong fins to create dynamic lift and propel themselves. It

1632-441: A rhythmic flicking pattern, which attracts prey as it resembles smaller organisms such as zooplankton and copepods . Thus, it has been concluded that they use luminescence as a lure to attract prey. Some research indicates that deep-sea organisms can not detect long wavelengths, and red light has a long wavelength of 680 nm. If this is the case, then fish are not lured by Erenna , and there must be another explanation. However,

1734-412: A signal to the muscles on one side of the fish. Mauthner cells are activated when something startles the fish and can be activated by visual or sound-based stimuli. Fast-starts are split up into three stages. Stage one, which is called the preparatory stroke, is characterized by the initial bending to a C-shape with small delay caused by hydrodynamic resistance. Stage two, the propulsive stroke, involves

1836-444: A similar design to jellyfish, swim by quickly opening and closing their shells, which draws in water and expels it from all sides. This locomotion is used as a means to escape predators such as starfish . Afterwards, the shell acts as a hydrofoil to counteract the scallop's tendency to sink. The Froude efficiency is low for this type of movement, about 0.3, which is why it's used as an emergency escape mechanism from predators. However,

1938-454: A sit-and-wait tactic for food. The gelatinous body plan allows for flexibility when catching prey, but the gelatinous adaptations are based on habitat. They swim around waiting for their long tentacles to encounter prey. In addition, siphonophores in a group denoted Erenna have the ability to generate bioluminescence and red fluorescence while its tentilla twitches in a way to mimic motions of small crustaceans and copepods. These actions entice

2040-413: A solution to the problem of tetrapod swimming through the development of their forelimbs into flippers of high-aspect-ratio wing shape, with which they imitate a bird's propulsive mode more accurately than do the eagle-rays themselves. Aquatic reptiles such as sea turtles (see also turtles ) and extinct species like Pliosauroids predominantly use their pectoral flippers to propel themselves through

2142-454: A spring to open the shell. The elasticity causes the work done against the water to be low because of the large openings the water has to enter and the small openings the water has to leave. The inertial work of scallop jet-propulsion is also low. Because of the low inertial work, the energy savings created by the elastic tissue is so small that it's negligible. Medusae can also use their elastic mesoglea to enlarge their bell. Their mantle contains

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2244-463: A swim bladder, have few lipids and proteins, deeply ossified bones, and watery tissues that maintain their buoyancy. Some sharks ' livers are composed of low-density lipids, such as hydrocarbon squalene or wax esters (also found in Myctophidae without swim bladders), which provide buoyancy. Swimming animals that are denser than water must generate lift or adapt a benthic lifestyle. Movement of

2346-474: A swimming organism affects the resulting drag. Long, slender bodies reduce pressure drag by streamlining, while short, round bodies reduce frictional drag; therefore, the optimal shape of an organism depends on its niche. Swimming organisms with a fusiform shape are likely to experience the greatest reduction in both pressure and frictional drag. Wing shape also affects the amount of drag experienced by an organism, as with different methods of stroke, recovery of

2448-507: A theory to explain the loss of that instinct. Termed the Saci last common ancestor hypothesis (after Saci , a Brazilian folklore character who cannot cross water barriers), it holds that the loss of instinctive swimming ability in apes is best explained as a consequence of constraints related to the adaptation to an arboreal life in the last common ancestor of apes. Bender hypothesized that the ancestral ape increasingly avoided deep-water bodies when

2550-432: Is a result of the body of the fish pushing against the water. Waves of undulation create rearward momentum against the water providing the forward thrust required to push the fish forward. The Froude propulsion efficiency is defined as the ratio of power output to the power input: nf = 2 U 1 / ( U 1 + U 2 ) where U1 = free stream velocity and U2 = jet velocity. A good efficiency for carangiform propulsion

2652-518: Is also present in these tissues. Organisms in the order of Siphonophorae have been classified into the phylum Cnidaria and the class Hydrozoa. The phylogenetic relationships of siphonophores have been of great interest due to the high variability of the organization of their polyp colonies and medusae. Once believed to be a highly distinct group, larval similarities and morphological features have led researchers to believe that siphonophores had evolved from simpler colonial hydrozoans similar to those in

2754-451: Is an ancient lineage that dates back to c. 640 million years ago. Ernst Haeckel described numerous siphonophores, and several plates from his Kunstformen der Natur (1904) depict members of the taxon : Order (biology) What does and does not belong to each order is determined by a taxonomist , as is whether a particular order should be recognized at all. Often there is no exact agreement, with different taxonomists each taking

2856-444: Is between 50 and 80%. Pressure differences occur outside the boundary layer of swimming organisms due to disrupted flow around the body. The difference on the up- and down-stream surfaces of the body is pressure drag , which creates a downstream force on the object. Frictional drag, on the other hand, is a result of fluid viscosity in the boundary layer . Higher turbulence causes greater frictional drag. Reynolds number (Re)

2958-416: Is bypassed so the colony as a whole is not negatively affected. The velum, a thin band of tissue surrounding the opening of the jet, also plays a role in swimming patterns, shown specifically through research done on the previous mentioned species N. bijuga. The velum becomes smaller and more circular during times of forward propulsion compared to a large velum that is seen during refill periods. Additionally,

3060-419: Is cell movement through the fluid medium. Furthermore, the direction of movement is determined by chemotaxis . When chemoattraction occurs in a particular area of the cell membrane , actin polymerization can begin and move the cell in that direction. An excellent example of an organism that utilizes pseudopods is Naegleria fowleri . A Simple Animation Among the radiata , jellyfish and their kin,

3162-402: Is common for fish to use more than one form of propulsion, although they will display one dominant mode of swimming Gait changes have even been observed in juvenile reef fish of various sizes. Depending on their needs, fish can rapidly alternate between synchronized fin beats and alternating fin beats. According to Guinness World Records 2009 , Hippocampus zosterae (the dwarf seahorse)

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3264-489: Is due to the amount of water the squid can accelerate out of its mantle cavity. Jellyfish use a one-way water cavity design which generates a phase of continuous cycles of jet-propulsion followed by a rest phase. The Froude efficiency is about 0.09, which indicates a very costly method of locomotion. The metabolic cost of transport for jellyfish is high when compared to a fish of equal mass. Other jet-propelled animals have similar problems in efficiency. Scallops , which use

3366-405: Is in fact a colonial organism composed of medusoid and polypoid zooids that are morphologically and functionally specialized. Zooids are multicellular units that develop from a single fertilized egg and combine to create functional colonies able to reproduce, digest, float, maintain body positioning, and use jet propulsion to move. Most colonies are long, thin, transparent floaters living in

3468-400: Is positioned within the siphonophore, their function differs. Colonial movement is determined by individual nectophores of all developmental stages. The smaller individuals are concentrated towards the top of the siphonophore, and their function is turning and adjusting the orientation of the colony. Individuals will get larger the older they are. The larger individuals are located at the base of

3570-442: Is the measure of the relationships between inertial and viscous forces in flow ((animal's length x animal's velocity)/kinematic viscosity of the fluid). Turbulent flow can be found at higher Re values, where the boundary layer separates and creates a wake, and laminar flow can be found at lower Re values, when the boundary layer separation is delayed, reducing wake and kinetic energy loss to opposing water momentum. The body shape of

3672-552: Is the slowest moving fish, with a top speed of about 5 feet (150 cm) per hour. They swim very poorly, rapidly fluttering a dorsal fin and using pectoral fins (located behind their eyes) to steer. Seahorses have no caudal fin . Hydrofoils , or fins , are used to push against the water to create a normal force to provide thrust, propelling the animal through water. Sea turtles and penguins beat their paired hydrofoils to create lift. Some paired fins, such as pectoral fins on leopard sharks, can be angled at varying degrees to allow

3774-448: Is why many fish are streamlined in shape. Streamlined shapes work to reduce drag by orienting elongated objects parallel to the force of drag, therefore allowing the current to pass over and taper off the end of the fish. This streamlined shape allows for more efficient use of energy locomotion. Some flat-shaped fish can take advantage of pressure drag by having a flat bottom surface and curved top surface. The pressure drag created allows for

3876-628: The Prodromus Systematis Naturalis Regni Vegetabilis of Augustin Pyramus de Candolle and the Genera Plantarum of Bentham & Hooker, it indicated taxa that are now given the rank of family (see ordo naturalis , ' natural order '). In French botanical publications, from Michel Adanson 's Familles naturelles des plantes (1763) and until the end of the 19th century, the word famille (plural: familles )

3978-483: The Paramecium to propel through the water at speeds of 500 micrometers per second. Certain organisms such as bacteria and animal sperm have flagellum which have developed a way to move in liquid environments. A rotary motor model shows that bacteria uses the protons of an electrochemical gradient in order to move their flagella. Torque in the flagella of bacteria is created by particles that conduct protons around

4080-474: The pelagic zone . Like other hydrozoans , some siphonophores emit light to attract and attack prey. While many sea animals produce blue and green bioluminescence , a siphonophore in the genus Erenna was only the second life form found to produce a red light (the first one being the scaleless dragonfish Chirostomias pliopterus ). Siphonophores are colonial hydrozoans that do not exhibit alternation of generations but instead reproduce asexually through

4182-515: The 19th century, 56 new species were observed due to research voyages conducted by European powers. The majority of new species found during this time period were collected in coastal, surface waters. During the HMS Challenger expedition , various species of siphonophores were collected. Ernst Haeckel attempted to conduct a write up of all of the species of siphonophores collected on this expedition. He introduced 46 "new species"; however, his work

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4284-684: The Latin suffix -iformes meaning 'having the form of' (e.g. Passeriformes ), but orders of mammals and invertebrates are not so consistent (e.g. Artiodactyla , Actiniaria , Primates ). For some clades covered by the International Code of Zoological Nomenclature , several additional classifications are sometimes used, although not all of these are officially recognized. In their 1997 classification of mammals , McKenna and Bell used two extra levels between superorder and order: grandorder and mirorder . Michael Novacek (1986) inserted them at

4386-455: The amount of work the scallop has to do is mitigated by the elastic hinge that connects the two shells of the bivalve. Squids swim by drawing water into their mantle cavity and expelling it through their siphon. The Froude efficiency of their jet-propulsion system is around 0.29, which is much lower than a fish of the same mass. Much of the work done by scallop muscles to close its shell is stored as elastic energy in abductin tissue, which acts as

4488-497: The amount of zooid types has increased. 2. The last common ancestor had many types of zooids and the diversity seen today is due to loss of zooid types. Research shows no evidence supporting the first hypothesis, and has seen some evidence in support of the second. Currently, the World Register of Marine Species (WoRMS) identifies 175 species of siphonophores. They can differ greatly in terms of size and shape, which largely reflects

4590-537: The animal to rise, fall, or maintain its level in the water column. The reduction of fin surface area helps to minimize drag, and therefore increase efficiency. Regardless of size of the animal, at any particular speed, maximum possible lift is proportional to (wing area) x (speed) . Dolphins and whales have large, horizontal caudal hydrofoils, while many fish and sharks have vertical caudal hydrofoils. Porpoising (seen in cetaceans, penguins, and pinnipeds) may save energy if they are moving fast. Since drag increases with speed,

4692-448: The animal's velocity fluctuates as it moves through the water, accelerating while expelling water and decelerating while vacuuming water. Even though these fluctuations in drag and mass can be ignored if the frequency of the jet-propulsion cycles is high enough, jet-propulsion is a relatively inefficient method of aquatic locomotion. All cephalopods can move by jet propulsion , but this is a very energy-consuming way to travel compared to

4794-434: The aqueous environment. Movement using a pseudopod is accomplished through increases in pressure at one point on the cell membrane . This pressure increase is the result of actin polymerization between the cortex and the membrane. As the pressure increases the cell membrane is pushed outward creating the pseudopod. When the pseudopod moves outward, the rest of the body is pulled forward by cortical tension. The result

4896-425: The base of the flagellum. The direction of rotation of the flagella in bacteria comes from the occupancy of the proton channels along the perimeter of the flagellar motor. Movement of sperm is called sperm motility . The middle of the mammalian spermatozoon contains mitochondria that power the movement of the flagellum of the sperm. The motor around the base produces torque, just like in bacteria for movement through

4998-470: The body bending rapidly to the other side, which may occur multiple times. Stage three, the rest phase, cause the fish to return to normal steady-state swimming and the body undulations begin to cease. Large muscles located closer to the central portion of the fish are stronger and generate more force than the muscles in the tail. This asymmetry in muscle composition causes body undulations that occur in Stage 3. Once

5100-420: The body is heading. This opposing force is called drag . The return-stroke drag causes drag swimmers to employ different strategies than lift swimmers. Reducing drag on the return stroke is essential for optimizing efficiency. For example, ducks paddle through the water spreading the webs of their feet as they move water back, and then when they return their feet to the front they pull their webs together to reduce

5202-424: The center of the siphonophore. Haplonemes have open-tipped tubules with spines, but no distinct shaft. This is the most common nematocyst among siphonophores. Desmonemes do not have spines but instead there are adhesive properties on the tubules to hold onto prey. Rhopalonemes are nematocysts with wide tubules for prey. Due to the lack of food in the deep sea environment, a majority of siphonophore species function in

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5304-637: The colony, and their main function is thrust propulsion. These larger individuals are important in attaining the maximum speed of the colony. Every individual is key to the movement of the aggregate colony, and understanding their organization may allow us to make advances in our own multi-jet propulsion vehicles. The colonial organization of siphonophores, particularly in Nanomia bijuga confers evolutionary advantages. A large number of concentrated individuals allows for redundancy. This means that even if some individual nectophores become functionally compromised, their role

5406-517: The cost of locomotion, but limits them to drag-based modes. Although they are less efficient, drag swimmers are able to produce more thrust at low speeds than lift swimmers. They are also thought to be better for maneuverability due to the large thrust produced. Most of the Amphibia have a larval state, which has inherited anguilliform motion, and a laterally compressed tail to go with it, from fish ancestors. The corresponding tetrapod adult forms, even in

5508-479: The deep sea and can be found in all of the oceans. Siphonophore species rarely only inhabit one location. Some species, however, can be confined to a specific range of depths and/or an area of the ocean. Siphonophores use a method of locomotion similar to jet propulsion. A siphonophore is a complex aggregate colony made up of many nectophores, which are clonal individuals that form by budding and are genetically identical. Depending on where each individual nectophore

5610-523: The deep sea. Physonects have a pneumatophore and nectosome, which harbors the nectophores used for jet propulsion. The nectophores pump water backwards in order to move forward. Calycophorans differ from cystonects and physonects in that they have two nectophores and no pneumatophore. Instead they often possess oil-filled glands which likely help with buoyancy. Siphonophores possess multiple types of zooid. Scientists have determined two possible evolutionary hypothesis for this observation: 1. As time has gone on,

5712-715: The deep-sea remains largely unexplored and red light sensitivity in fish such as Cyclothone and the deep myctophid fish should not be discarded. Bioluminescent lures are found in many different species of siphonophores, and are used for a variety of reasons. Species such as Agalma okeni , Athorybia rosacea , Athorybia lucida , and Lychnafalma utricularia use their lures as a mimicry device to attract prey. A. rosacea mimic fish larvae, A. lucida are thought to mimic larvacean houses, and L. utricularia mimic hydromedusa. The species Resomia ornicephala uses their green and blue fluorescing tentilla to attract krill, helping them to outcompete other organisms that are hunting for

5814-457: The diets of strong swimming siphonophores consist of smaller prey, and the diets of weak swimming siphonophores consist of larger prey. A majority of siphonophores have gastrozooids that have a characteristic tentacle attached to the base of the zooid. This structural feature functions in assisting the organisms in catching prey. Species with large gastrozooids are capable of consuming a broad range of prey sizes. Similar to many other organisms in

5916-468: The ending -anae that was initiated by Armen Takhtajan 's publications from 1966 onwards. The order as a distinct rank of biological classification having its own distinctive name (and not just called a higher genus ( genus summum )) was first introduced by the German botanist Augustus Quirinus Rivinus in his classification of plants that appeared in a series of treatises in the 1690s. Carl Linnaeus

6018-447: The environment that they inhabit. Siphonophores are most often pelagic organisms, yet level species are benthic . Smaller, warm-water siphonophores typically live in the epipelagic zone and use their tentacles to capture zooplankton and copepods . Larger siphonophores live in deeper waters, as they are generally longer and more fragile and must avoid strong currents. They mostly feed on larger prey. The majority of siphonophores live in

6120-466: The fast-start is completed, the position of the fish has been shown to have a certain level of unpredictability, which helps fish survive against predators. The rate at which the body can bend is limited by resistance contained in the inertia of each body part. However, this inertia assists the fish in creating propulsion as a result of the momentum created against the water. The forward propulsion created from C-starts, and steady-state swimming in general,

6222-659: The fastest marine invertebrates, and they can out accelerate most fish. 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. 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. Most cephalopods float (i.e. are neutrally buoyant ), so do not need to swim to remain afloat. Squid swim more slowly than fish, but use more power to generate their speed. The loss in efficiency

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6324-888: The field of zoology , the Linnaean orders were used more consistently. That is, the orders in the zoology part of the Systema Naturae refer to natural groups. Some of his ordinal names are still in use, e.g. Lepidoptera (moths and butterflies) and Diptera (flies, mosquitoes, midges, and gnats). In virology , the International Committee on Taxonomy of Viruses 's virus classification includes fifteen taxomomic ranks to be applied for viruses , viroids and satellite nucleic acids : realm , subrealm , kingdom , subkingdom, phylum , subphylum , class, subclass, order, suborder, family, subfamily , genus, subgenus , and species. There are currently fourteen viral orders, each ending in

6426-408: The fish into a C-shape. Afterwards, muscle contraction occurs on the opposite side to allow the fish to enter into a steady swimming state with waves of undulation traveling alongside the body. The power of the bending motion comes from fast-twitch muscle fibers located in the central region of the fish. The signal to perform this contraction comes from a set of Mauthner cells which simultaneously send

6528-423: The fish to generate hydrodynamic lift is necessary to prevent sinking. Often, their bodies act as hydrofoils , a task that is more effective in flat-bodied fish. At a small tilt angle, the lift is greater for flat fish than it is for fish with narrow bodies. Narrow-bodied fish use their fins as hydrofoils while their bodies remain horizontal. In sharks, the heterocercal tail shape drives water downward, creating

6630-599: The late Cambrian, and chordates were probably swimming from the Early Cambrian. Many terrestrial animals retain some capacity to swim, however some have returned to the water and developed the capacities for aquatic locomotion. Most apes (including humans), however, lost the swimming instinct . In 2013 Pedro Renato Bender, a research fellow at the University of the Witwatersrand 's Institute for Human Evolution, proposed

6732-749: The leg movements of a human 'breast stroke,' rather more efficiently because the legs are better streamlined. From the point of view of aquatic propulsion, the descent of modern members of the class Reptilia from archaic tailed Amphibia is most obvious in the case of the order Crocodilia ( crocodiles and alligators ), which use their deep, laterally compressed tails in an essentially carangiform mode of propulsion (see Fish locomotion#Carangiform ). Terrestrial snakes , in spite of their 'bad' hydromechanical shape with roughly circular cross-section and gradual posterior taper, swim fairly readily when required, by an anguilliform propulsion (see Fish locomotion#Anguilliform ). Cheloniidae (sea turtles ) have found

6834-411: The lift swimmer. There are natural processes in place to optimize energy use, and it is thought that adjustments of metabolic rates can compensate in part for mechanical disadvantages. Semi-aquatic animals compared to fully aquatic animals exhibit exacerbation of drag. Design that allows them to function out of the water limits the efficiency possible to be reached when in the water. In water swimming at

6936-403: The main form of swimming is to flex their cup shaped bodies. All jellyfish are free-swimming, although many of these spend most of their time swimming passively. Passive swimming is akin to gliding; the organism floats, using currents where it can, and does not exert any energy into controlling its position or motion. Active swimming, in contrast, involves the expenditure of energy to travel to

7038-550: The mid-20th century. On April 6, 2020, the Schmidt Ocean Institute announced the discovery of a giant Apolemia siphonophore in submarine canyons near Ningaloo Coast , measuring 15 m (49 ft) diameter with a ring approximately 47 m (154 ft) long, possibly the largest siphonophore, and longest animal, ever recorded. There is no fossil record of siphonophores, though they have evolved and adapted for an extensive time period. Their phylum, Cnidaria ,

7140-536: The natural world as biological microorganisms , such as bacteria , archaea , protists , sperm and microanimals . Ciliates use small flagella called cilia to move through the water. One ciliate will generally have hundreds to thousands of cilia that are densely packed together in arrays. During movement, an individual cilium deforms using a high-friction power stroke followed by a low-friction recovery stroke. Since there are multiple cilia packed together on an individual organism, they display collective behavior in

7242-399: The opposite direction of the squirting water. Most organisms are equipped with one of two designs for jet propulsion; they can draw water from the rear and expel it from the rear, such as jellyfish, or draw water from front and expel it from the rear, such as salps. Filling up the cavity causes an increase in both the mass and drag of the animal. Because of the expanse of the contracting cavity,

7344-627: The orders Anthoathecata and Leptothecata . Consequently, they are now united with these in the subclass Hydroidolina . Early analysis divided siphonophores into three main subgroups based on the presence or the absence of two different traits: swimming bells (nectophores) and floats (pneumatophores). The subgroups consisted of Cystonectae, Physonectae, and Calycorphores. Cystonectae had pneumatophores, Calycophores had nectophores, and Physonectae had both. Eukaryotic nuclear small subunit ribosomal gene 18S, eukaryotic mitochondrial large subunit ribosomal gene 16S, and transcriptome analyses further support

7446-407: The parasagittal plane. Drag swimmers use a cyclic motion in which they push water back in a power stroke, and return their limb forward in the return or recovery stroke. When they push water directly backwards, this moves their body forward, but as they return their limbs to the starting position, they push water forward, which will thus pull them back to some degree, and so opposes the direction that

7548-553: The phylogenetic division of Siphonophorae into two main clades: Cystonectae and Codonophora. Suborders within Codonophora include Physonectae (consisting of the clades Calycophorae and Euphysonectae), Pyrostephidae, and Apolemiidae. Carl Linnaeus described the first siphonophore, the Portuguese man o' war , in 1758. The discovery rate of siphonophore species was slow in the 18th century, as only four additional species were found. During

7650-490: The phylum of Cnidaria , many siphonophore species exhibit nematocyst stinging capsules on branches of their tentacles called tentilla. The nematocysts are arranged in dense batteries on the side of the tentilla. When the siphonophore encounters potential prey, their tentillum react to where the 30–50 cm (12–20 in) tentacles create a net by transforming their shape around the prey. The nematocysts then shoot millions of paralyzing, and sometimes fatal, toxin molecules at

7752-463: The position of the velum changes with swimming behaviors; the velum is curved downward in times of jetting, but during refill, the velum is moved back into the nectophore. The siphonophore Namonia bijuga also practices diel vertical migration , as it remains in the deep-sea during the day but rises during the night. Siphonophores are predatory carnivores . Their diets consist of a variety of copepods, other small crustaceans, and small fish. Generally,

7854-465: The pre-stroke position results in the accumulation of drag. High-speed ram ventilation creates laminar flow of water from the gills along the body of an organism. The secretion of mucus along the organism's body surface, or the addition of long-chained polymers to the velocity gradient, can reduce frictional drag experienced by the organism. Many aquatic/marine organisms have developed organs to compensate for their weight and control their buoyancy in

7956-417: The prey to move closer to the siphonophore, allowing it to trap and digest it. The modes of reproduction for siphonophores vary among the different species, and to this day, several modes remain unknown. Generally, a single zygote begins the formation of a colony of zooids. The fertilized egg matures into a protozooid, which initiates the budding process and creation of a new zooid. This process repeats until

8058-413: The rear flippers laterally, pushing the animal through the water. Some arthropods, such as lobsters and shrimps , can propel themselves backwards quickly by flicking their tail, known as lobstering or the caridoid escape reaction . Varieties of fish, such as teleosts, also use fast-starts to escape from predators. Fast-starts are characterized by the muscle contraction on one side of the fish twisting

8160-402: The risks of being exposed to water were clearly higher than the advantages of crossing them. A decreasing contact with water bodies then could have led to the disappearance of the doggy paddle instinct. Microbial swimmers, sometimes called microswimmers , are microscopic entities that have the ability to move in fluid or aquatic environment. Natural microswimmers are found everywhere in

8262-420: The same position. Michael Benton (2005) inserted them between superorder and magnorder instead. This position was adopted by Systema Naturae 2000 and others. In botany , the ranks of subclass and suborder are secondary ranks pre-defined as respectively above and below the rank of order. Any number of further ranks can be used as long as they are clearly defined. The superorder rank is commonly used, with

8364-515: The same prey. Siphonophores from the genus Erenna use bioluminescent lures surrounded by red fluorescence to attract prey and possibly mimic a fish from the Cyclothone genus. Their prey is lured in through a unique flicking behavior associated with the tentilla. When young, the tentilla of organisms in the Erenna genus contain only bioluminescent tissue, but, as the organism ages, red fluorescent material

8466-490: The sea surface. Among the Deuterostomia , there are a number of swimmers as well. Feather stars can swim by undulating their many arms. Salps move by pumping waters through their gelatinous bodies. The deuterostomes most evolved for swimming are found among the vertebrates , notably the fish . Jet propulsion is a method of aquatic locomotion where animals fill a muscular cavity and squirt out water to propel them in

8568-425: The suborders: Cystonectae , Physonectae , and Calycophorae . Cystonects have a long stem with the attached zooids. Each group of zooids has a gastrozooid. The gastrozooid has a tentacle used for capturing and digesting food. The groups also have gonophores, which are specialized for reproduction. They use a pneumatophore, a gas-filled float, on their anterior end and drift at the surface of the water or stay afloat in

8670-458: The subsequent pull of water forward. The legs of water beetles have little hairs which spread out to catch and move water back in the power stroke, but lay flat as the appendage moves forward in the return stroke. Also, one side of a water beetle leg is wider than the others and is held perpendicular to the motion when pushing backward, but the leg rotates when the limb returns forward, so the thinner side catches less water. Drag swimmers experience

8772-420: The suffix -virales . Aquatic locomotion#Jet propulsion Aquatic locomotion or swimming is biologically propelled motion through a liquid medium. The simplest propulsive systems are composed of cilia and flagella . Swimming has evolved a number of times in a range of organisms including arthropods , fish , molluscs , amphibians , reptiles , birds , and mammals . Swimming evolved

8874-487: The surface exposes them to resistive wave drag and is associated with a higher cost than submerged swimming. Swimming below the surface exposes them to resistance due to return strokes and pressure, but primarily friction. Frictional drag is due to fluid viscosity and morphology characteristics. Pressure drag is due to the difference of water flow around the body and is also affected by body morphology. Semi-aquatic organisms encounter increased resistive forces when in or out of

8976-586: The tail propulsion used by fish. The relative efficiency of jet propulsion decreases further as animal size increases. Since the Paleozoic, as competition with fish produced an environment where efficient motion was crucial to survival, jet propulsion has taken a back role, with fins and tentacles used to maintain a steady velocity. The stop-start motion provided by the jets, however, continues to be useful for providing bursts of high speed – not least when capturing prey or avoiding predators. Indeed, it makes cephalopods

9078-403: The tail-retaining sub-class Urodeles , are sometimes aquatic to only a negligible extent (as in the genus Salamandra , whose tail has lost its suitability for aquatic propulsion), but the majority of Urodeles , from the newts to the giant salamander Megalobatrachus, retain a laterally compressed tail for a life that is aquatic to a considerable degree, which can use in a carangiform motion. Of

9180-448: The tailless amphibians (the frogs and toads of the sub-class Anura ) the majority are aquatic to an insignificant extent in adult life, but in that considerable minority that are mainly aquatic we encounter for the first time the problem of adapting the tailless-tetrapod structure for aquatic propulsion. The mode that they use is unrelated to any used by fish. With their flexible back legs and webbed feet they execute something close to

9282-420: The transition from sand to water. If rotated in the pitch, yaw or roll direction, the hatchlings are capable of counteracting the forces acting upon them by correcting with either their pectoral or pelvic flippers and redirecting themselves towards the open ocean. Among mammals otariids ( fur seals ) swim primarily with their front flippers, using the rear flippers for steering, and phocids ( true seals ) move

9384-428: The trapped prey which is then transferred to the proper location for digestion. Some species of siphonophores use aggressive mimicry by using bioluminescent light so the prey cannot properly identify the predator. There are four types of nematocysts in siphonophore tentilla: heteronemes, haplonemes, desmonemes, and rhopalonemes. Heteronemes are the largest nematocysts and are spines on a shaft close to tubules attached to

9486-417: The upward lift of the fish. Appendages of aquatic organisms propel them in two main and biomechanically extreme mechanisms. Some use lift powered swimming, which can be compared to flying as appendages flap like wings, and reduce drag on the surface of the appendage. Others use drag powered swimming, which can be compared to oars rowing a boat, with movement in a horizontal plane, or paddling, with movement in

9588-404: The water and their pelvic flippers for maneuvering. During swimming they move their pectoral flippers in a dorso-ventral motion , causing forward motion. During swimming, they rotate their front flippers to decrease drag through the water column and increase efficiency. Newly hatched sea turtles exhibit several behavioral skills that help orientate themselves towards the ocean as well as identifying

9690-509: The water, as they are not specialized for either habitat. The morphology of otters and beavers, for example, must meet needs for both environments. Their fur decreases streamlining and creates additional drag. The platypus may be a good example of an intermediate between drag and lift swimmers because it has been shown to have a rowing mechanism which is similar to lift-based pectoral oscillation. The limbs of semi-aquatic organisms are reserved for use on land and using them in water not only increases

9792-532: The water. These structures, make the density of their bodies very close to that of the surrounding water. Some hydrozoans, such as siphonophores, has gas-filled floats; the Nautilus, Sepia, and Spirula ( Cephalopods ) have chambers of gas within their shells; and most teleost fish and many lantern fish (Myctophidae) are equipped with swim bladders . Many aquatic and marine organisms may also be composed of low-density materials. Deep-water teleosts, which do not have

9894-574: The word family ( familia ) was assigned to the rank indicated by the French famille , while order ( ordo ) was reserved for a higher rank, for what in the 19th century had often been named a cohors (plural cohortes ). Some of the plant families still retain the names of Linnaean "natural orders" or even the names of pre-Linnaean natural groups recognized by Linnaeus as orders in his natural classification (e.g. Palmae or Labiatae ). Such names are known as descriptive family names. In

9996-429: The work required to swim unit distance is greater at higher speeds, but the work needed to jump unit distance is independent of speed. Seals propel themselves through the water with their caudal tail, while sea lions create thrust solely with their pectoral flippers. As with moving through any fluid, friction is created when molecules of the fluid collide with organism. The collision causes drag against moving fish, which

10098-433: The zooids in colonies widely vary among the different species; however, the majority of colonies are bilaterally arranged with dorsal and ventral sides to the stem. The stem is the vertical branch in the center of the colony to which the zooids attach. Zooids typically have special functions, and thus assume specific spatial patterns along the stem. Siphonophores typically exhibit one of three standard body plans matching

10200-445: Was heavily critiqued because some of the species that he identified were eventually found not to be siphonophores. Nonetheless, some of his descriptions and figures (pictured below) are considered useful by modern biologists. A rate of about 10 new species discoveries per decade was observed during the 20th century. Considered the most important researcher of siphonophores, A. K. Totton introduced 23 new species of siphonophores during

10302-543: Was the first to apply it consistently to the division of all three kingdoms of nature (then minerals , plants , and animals ) in his Systema Naturae (1735, 1st. Ed.). For plants, Linnaeus' orders in the Systema Naturae and the Species Plantarum were strictly artificial, introduced to subdivide the artificial classes into more comprehensible smaller groups. When the word ordo was first consistently used for natural units of plants, in 19th-century works such as

10404-540: Was used as a French equivalent for this Latin ordo . This equivalence was explicitly stated in the Alphonse Pyramus de Candolle 's Lois de la nomenclature botanique (1868), the precursor of the currently used International Code of Nomenclature for algae, fungi, and plants . In the first international Rules of botanical nomenclature from the International Botanical Congress of 1905,

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