60-422: See text Opahs , also commonly known as moonfish , sunfish , cowfish (not to be confused with Molidae ), kingfish , and redfin ocean pan are large, colorful, deep-bodied pelagic lampriform fishes comprising the small family Lampridae (also spelled Lamprididae ). The family comprises two genera: Lampris (from Ancient Greek λαμπρός ( lamprós ) 'brilliant, clear') and
120-444: A Brownian motion model of trait evolution along a phylogeny. More recent methods also quantify the strength of convergence. One drawback to keep in mind is that these methods can confuse long-term stasis with convergence due to phenotypic similarities. Stasis occurs when there is little evolutionary change among taxa. Distance-based measures assess the degree of similarity between lineages over time. Frequency-based measures assess
180-428: A nucleophile . In order to activate that nucleophile, they orient an acidic and a basic residue in a catalytic triad . The chemical and physical constraints on enzyme catalysis have caused identical triad arrangements to evolve independently more than 20 times in different enzyme superfamilies . Threonine proteases use the amino acid threonine as their catalytic nucleophile . Unlike cysteine and serine, threonine
240-425: A taxonomic review in 2018 found that more should be recognized (the result of splitting L. guttatus into several species, each with a more restricted geographic range), bringing the total to six. The six species of Lampris have mostly non-overlapping geographical ranges, and can be recognized based on body shape and coloration pattern. Opahs are deeply keeled, compressed, discoid fish with conspicuous coloration:
300-422: A common origin but can have dissimilar functions. Bird, bat, and pterosaur wings are analogous structures, but their forelimbs are homologous, sharing an ancestral state despite serving different functions. The opposite of convergence is divergent evolution , where related species evolve different traits. Convergent evolution is similar to parallel evolution , which occurs when two independent species evolve in
360-413: A gene has simply been switched off and then re-enabled later. Such a re-emerged trait is called an atavism . From a mathematical standpoint, an unused gene ( selectively neutral ) has a steadily decreasing probability of retaining potential functionality over time. The time scale of this process varies greatly in different phylogenies; in mammals and birds, there is a reasonable probability of remaining in
420-575: A high concentration of cerebrosides in the skin of their wings. This improves skin flexibility, a trait useful for flying animals; other mammals have a far lower concentration. The extinct pterosaurs independently evolved wings from their fore- and hindlimbs, while insects have wings that evolved separately from different organs. Flying squirrels and sugar gliders are much alike in their mammalian body plans, with gliding wings stretched between their limbs, but flying squirrels are placentals while sugar gliders are marsupials, widely separated within
480-468: A long evolutionary history prior to the extinction of the dinosaurs under which to accumulate relevant differences. The enzymology of proteases provides some of the clearest examples of convergent evolution. These examples reflect the intrinsic chemical constraints on enzymes, leading evolution to converge on equivalent solutions independently and repeatedly. Serine and cysteine proteases use different amino acid functional groups (alcohol or thiol) as
540-455: A member of Tetraodontiformes , their teeth are fused into a beak-like structure, making it impossible for them to close their mouths. Despite this, they feed mainly on soft-bodied animals, such as jellyfish and salps , although they also take small fish or crustaceans. Molids have been filmed interacting with other species. Since molids are susceptible to skin parasites , they make use of cleaner fish . A molid in need of cleaning will locate
600-635: A molecular level to toxins. One well-characterized example is the evolution of resistance to cardiotonic steroids (CTSs) via amino acid substitutions at well-defined positions of the α-subunit of Na ,K -ATPase (ATPalpha). Variation in ATPalpha has been surveyed in various CTS-adapted species spanning six insect orders. Among 21 CTS-adapted species, 58 (76%) of 76 amino acid substitutions at sites implicated in CTS resistance occur in parallel in at least two lineages. 30 of these substitutions (40%) occur at just two sites in
660-469: A patch of floating algae or flotsam that is home to halfmoons . The molid signals a readiness for cleaning by swimming almost vertically with its head near the surface of the water, and waits for the smaller cleaner fish to feed on the parasite worms. Similarly, the molid may break the surface of the water with its dorsal fin and beak to attract the attention of a gull or similar seabird . The seabird will then dig worms and other stubborn parasites out of
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#1733094371478720-799: A phenomenon called cranial endothermy and one they share with sharks in the family Lamnidae , billfishes , and some tunas. This may allow their eyes and brains to continue functioning during deep dives into water below 4 °C. Squid and euphausiids ( krill ) make up the bulk of the opah diet; small fish are also taken. Pop-up archival transmitting tagging operations have indicated that, aside from humans, large pelagic sharks , such as great white sharks and mako sharks , are primary predators of opah. The tetraphyllidean tapeworm , Pelichnibothrium speciosum , has been found in L. guttatus , which may be an intermediate or paratenic host. The planktonic opah larvae initially resemble those of certain ribbonfishes (Trachipteridae), but are distinguished by
780-568: A phylogenetic reconstruction, and are sometimes explicitly sought by investigators. The methods applied to infer convergent evolution depend on whether pattern-based or process-based convergence is expected. Pattern-based convergence is the broader term, for when two or more lineages independently evolve patterns of similar traits. Process-based convergence is when the convergence is due to similar forces of natural selection . Earlier methods for measuring convergence incorporate ratios of phenotypic and phylogenetic distance by simulating evolution with
840-445: A similar environment, and so face the same environmental factors. When occupying similar ecological niches (that is, a distinctive way of life) similar problems can lead to similar solutions. The British anatomist Richard Owen was the first to identify the fundamental difference between analogies and homologies . In biochemistry, physical and chemical constraints on mechanisms have caused some active site arrangements such as
900-433: A strong jet of water out of their mouths or gills. They can also make minor adjustments in the orientation of the anal fin or the dorsal fin so as to control the amount of force it produces and the angle at which the force is produced. In this respect, they use their fins much like a bird uses its wings. Molids are said to be able to produce sound by grinding their pharyngeal teeth , which are long and claw-like. Typical of
960-427: Is a secondary alcohol (i.e. has a methyl group). The methyl group of threonine greatly restricts the possible orientations of triad and substrate, as the methyl clashes with either the enzyme backbone or the histidine base. Consequently, most threonine proteases use an N-terminal threonine in order to avoid such steric clashes . Several evolutionarily independent enzyme superfamilies with different protein folds use
1020-463: Is a membrane stretched across four extremely elongated fingers and the legs. The airfoil of the bird wing is made of feathers , strongly attached to the forearm (the ulna) and the highly fused bones of the wrist and hand (the carpometacarpus ), with only tiny remnants of two fingers remaining, each anchoring a single feather. So, while the wings of bats and birds are functionally convergent, they are not anatomically convergent. Birds and bats also share
1080-415: Is greatly elongated, also in a falcated profile similar to the pelvic fins. The anal fin (around 34 to 41 rays) is about as high and as long as the shorter portion of the dorsal fin, and both fins have corresponding grooves into which they can be depressed. The snout is pointed and the mouth small, toothless , and terminal. The lateral line forms a high arch over the pectoral fins before sweeping down to
1140-639: Is known of opah biology and ecology . They are presumed to live out their entire lives in the open ocean, at mesopelagic depths of 50 to 500 m, with possible forays into the bathypelagic zone. They are apparently solitary, but are known to school with tuna and other scombrids . The fish propel themselves by a lift-based labriform mode of swimming, that is, by flapping their pectoral fins. This, together with their forked caudal fins and depressible median fins, indicates they swim at constantly high speeds like tuna. Lampris guttatus are able to maintain their eyes and brain at 2 °C warmer than their bodies,
1200-542: Is responsible, say with brown dominant to blue eye colour . However, a single locus is responsible for about 80% of the variation. In lemurs, the differences between blue and brown eyes are not completely known, but the same gene locus is not involved. While most plant species are perennial , about 6% follow an annual life cycle, living for only one growing season. The annual life cycle independently emerged in over 120 plant families of angiosperms. The prevalence of annual species increases under hot-dry summer conditions in
1260-409: Is the camera eye of cephalopods (such as squid and octopus), vertebrates (including mammals) and cnidarians (such as jellyfish). Their last common ancestor had at most a simple photoreceptive spot, but a range of processes led to the progressive refinement of camera eyes —with one sharp difference: the cephalopod eye is "wired" in the opposite direction, with blood and nerve vessels entering from
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#17330943714781320-522: The Chenopodiaceae and the Amaranthaceae . Fruits with a wide variety of structural origins have converged to become edible. Apples are pomes with five carpels ; their accessory tissues form the apple's core, surrounded by structures from outside the botanical fruit, the receptacle or hypanthium . Other edible fruits include other plant tissues; the fleshy part of a tomato is the walls of
1380-411: The catalytic triad to evolve independently in separate enzyme superfamilies . In his 1989 book Wonderful Life , Stephen Jay Gould argued that if one could "rewind the tape of life [and] the same conditions were encountered again, evolution could take a very different course." Simon Conway Morris disputes this conclusion, arguing that convergence is a dominant force in evolution, and given that
1440-402: The caudal peduncle . The larger species, Lampris guttatus , may reach a total length of 2 m (6.6 ft) and a weight of 270 kg (600 lb). The lesser-known Lampris immaculatus reaches a recorded total length of just 1.1 m (3.6 ft). The opah is the only fish known to exhibit whole body endothermy where all the internal organs are kept at a higher temperature than
1500-520: The dorsal and anal fins , giving them a "half-fish" appearance. They are also the largest of the ray-finned bony fish, with the southern sunfish , Mola alexandrini , recorded at 4.6 m (15 ft) in length and 2,744 kg (6,049 lb) in weight. The family name comes from the ocean sunfish 's scientific name Mola mola , both its genus name and epithet come from the Latin word mola for " millstone " because of its circular shape. Molidae have
1560-417: The last common ancestor of those groups. The cladistic term for the same phenomenon is homoplasy . The recurrent evolution of flight is a classic example, as flying insects , birds , pterosaurs , and bats have independently evolved the useful capacity of flight. Functionally similar features that have arisen through convergent evolution are analogous , whereas homologous structures or traits have
1620-600: The monotypic Megalampris (known only from fossil remains). The extinct family, Turkmenidae , from the Paleogene of Central Asia , is closely related, though much smaller. In 2015, Lampris guttatus was discovered to have near-whole-body endothermy in which the entire core of the body is maintained at around 5 °C above the surrounding water. This is unique among fish as most fish are entirely cold blooded or are capable of warming only some parts of their bodies. Two living species were traditionally recognized, but
1680-619: The pericarp . This implies convergent evolution under selective pressure, in this case the competition for seed dispersal by animals through consumption of fleshy fruits. Seed dispersal by ants ( myrmecochory ) has evolved independently more than 100 times, and is present in more than 11,000 plant species. It is one of the most dramatic examples of convergent evolution in biology. Carnivory has evolved multiple times independently in plants in widely separated groups. In three species studied, Cephalotus follicularis , Nepenthes alata and Sarracenia purpurea , there has been convergence at
1740-446: The proboscis of flower-visiting insects such as bees and flower beetles , or the biting-sucking mouthparts of blood-sucking insects such as fleas and mosquitos . Opposable thumbs allowing the grasping of objects are most often associated with primates , like humans and other apes, monkeys, and lemurs. Opposable thumbs also evolved in giant pandas , but these are completely different in structure, having six fingers including
1800-570: The Mesozoic ) all converged on the same streamlined shape. A similar shape and swimming adaptations are even present in molluscs, such as Phylliroe . The fusiform bodyshape (a tube tapered at both ends) adopted by many aquatic animals is an adaptation to enable them to travel at high speed in a high drag environment. Similar body shapes are found in the earless seals and the eared seals : they still have four legs, but these are strongly modified for swimming. The marsupial fauna of Australia and
1860-796: The Middle Miocene Calvert Formation of Virginia , USA; R. zappai Carnevale, 2007 from the Middle Miocene of Italy; R. ogaii Uyeno & Sakamoto, 1994 from the Middle Miocene of Japan; and an as yet unnamed species from the Upper Miocene of Algeria . Only five extant species in three extant genera are described: Convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in
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1920-517: The N-terminal residue as a nucleophile. This commonality of active site but difference of protein fold indicates that the active site evolved convergently in those families. Conus geographus produces a distinct form of insulin that is more similar to fish insulin protein sequences than to insulin from more closely related molluscs, suggesting convergent evolution, though with the possibility of horizontal gene transfer . Distant homologues of
1980-471: The back of the retina, rather than the front as in vertebrates. As a result, vertebrates have a blind spot . Birds and bats have homologous limbs because they are both ultimately derived from terrestrial tetrapods , but their flight mechanisms are only analogous, so their wings are examples of functional convergence. The two groups have independently evolved their own means of powered flight. Their wings differ substantially in construction. The bat wing
2040-421: The blood returning to the internal organs is warmed up to body temperature. Within the rete, the warm and cold blood flow past each other in opposite directions through thin vessels to maximise the heat transferred. This mechanism is called a counter-current heat exchanger . In addition to the rete mirabile in its gills, the opah also has a rete in the blood supply to its brain and eyes. This helps to trap heat in
2100-928: The body is a deep red-orange grading to rosy on the belly, with white spots covering the flanks. Both the median and paired fins are a bright vermilion . The large eyes stand out, as well, ringed with golden yellow. The body is covered in minute cycloid scales and its silvery, iridescent guanine coating is easily abraded. Opahs closely resemble in shape the unrelated butterfish (family Stromateidae). Both have falcated (curved) pectoral fins and forked, emarginated (notched) caudal fins . Aside from being significantly larger than butterfish, opahs have enlarged, falcated pelvic fins with about 14 to 17 rays , which distinguish them from superficially similar carangids —positioned thoracically; adult butterfish lack pelvic fins. The pectorals of opahs are also inserted (more or less) horizontally rather than vertically. The anterior portion of an opah's single dorsal fin (with about 50–55 rays)
2160-399: The cranium and further raise its temperature above the rest of the body. While the rete mirabile in the gills is unique to the opah, the cranial rete mirabile has also evolved independently in other fishes. Unlike in billfish which have a specialised noncontractile tissue that functions as a brain heater, the opah cranium is heated by the contractions of the large eye muscles. Almost nothing
2220-437: The dolphin; among marine mammals; between giant and red pandas; and between the thylacine and canids. Convergence has also been detected in a type of non-coding DNA , cis-regulatory elements , such as in their rates of evolution; this could indicate either positive selection or relaxed purifying selection . Swimming animals including fish such as herrings , marine mammals such as dolphins , and ichthyosaurs ( of
2280-617: The exposed surfaces of the proteins, where they might interact with other components of the cell or the digestive fluid. The authors also found that homologous genes in the non-carnivorous plant Arabidopsis thaliana tend to have their expression increased when the plant is stressed, leading the authors to suggest that stress-responsive proteins have often been co-opted in the repeated evolution of carnivory. Phylogenetic reconstruction and ancestral state reconstruction proceed by assuming that evolution has occurred without convergence. Convergent patterns may, however, appear at higher levels in
2340-475: The fewest vertebrae of any fish, with only 16 in Mola mola . They also completely lack all caudal bones, and most of their skeleton is made of cartilage . No bony plates occur in the skin, which is, however, thick and dense like cartilage and is fairly rough. They also lack swim bladders . Molids mostly swim by using their anal and dorsal fins; the pectoral fins are probably just stabilizers. To steer, they squirt
2400-446: The former's lack of dorsal and pelvic fin ornamentation. The slender hatchlings later undergo a marked and rapid transformation from a slender to deep-bodied form; this transformation is complete by 10.6 mm standard length in L. guttatus . Opahs are believed to have a low population resilience. Molidae The Molidae comprise the family of the molas or ocean sunfishes , unusual fish whose bodies come to an end just behind
2460-480: The four species-rich families of annuals ( Asteraceae , Brassicaceae , Fabaceae , and Poaceae ), indicating that the annual life cycle is adaptive. C 4 photosynthesis , one of the three major carbon-fixing biochemical processes, has arisen independently up to 40 times . About 7,600 plant species of angiosperms use C 4 carbon fixation, with many monocots including 46% of grasses such as maize and sugar cane , and dicots including several species in
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2520-431: The genome in a potentially functional state for around 6 million years. When two species are similar in a particular character, evolution is defined as parallel if the ancestors were also similar, and convergent if they were not. Some scientists have argued that there is a continuum between parallel and convergent evolution, while others maintain that despite some overlap, there are still important distinctions between
2580-456: The heat they generate while moving, these muscles have special regions that can generate additional heat without contracting. The opah has a thick layer of fat that insulates its internal organs and cranium from the surrounding water. However, fat alone is insufficient to retain heat within a fish's body. The gills are the main point of heat loss in fishes as this is where blood from the entire body must continuously be brought in close contact with
2640-407: The lineages diverged and became genetically isolated, the skin of both groups lightened more, and that additional lightening was due to different genetic changes. Lemurs and humans are both primates. Ancestral primates had brown eyes, as most primates do today. The genetic basis of blue eyes in humans has been studied in detail and much is known about it. It is not the case that one gene locus
2700-516: The mammal lineage from the placentals. Hummingbird hawk-moths and hummingbirds have evolved similar flight and feeding patterns. Insect mouthparts show many examples of convergent evolution. The mouthparts of different insect groups consist of a set of homologous organs, specialised for the dietary intake of that insect group. Convergent evolution of many groups of insects led from original biting-chewing mouthparts to different, more specialised, derived function types. These include, for example,
2760-454: The metal ion transporters ZIP in land plants and chlorophytes have converged in structure, likely to take up Fe efficiently. The IRT1 proteins from Arabidopsis thaliana and rice have extremely different amino acid sequences from Chlamydomonas ' s IRT1, but their three-dimensional structures are similar, suggesting convergent evolution. Many examples of convergent evolution exist in insects in terms of developing resistance at
2820-405: The molecular level. Carnivorous plants secrete enzymes into the digestive fluid they produce. By studying phosphatase , glycoside hydrolase , glucanase , RNAse and chitinase enzymes as well as a pathogenesis-related protein and a thaumatin -related protein, the authors found many convergent amino acid substitutions. These changes were not at the enzymes' catalytic sites, but rather on
2880-669: The molid's skin. The known fossil history of Molidae extends back to the Eocene , with the genus Eomola containing the species E. bimaxillaria , known from the Upper Eocene of the North Caucasus . The fossil genus Austromola containing one species, A. angerhoferi Gregorova, Schultz, Harzhauser & Kroh, 2009 , is known from the Lower Miocene Ebelsberg Formation near Pucking , Austria. This species
2940-474: The placental mammals of the Old World have several strikingly similar forms, developed in two clades, isolated from each other. The body, and especially the skull shape, of the thylacine (Tasmanian tiger or Tasmanian wolf) converged with those of Canidae such as the red fox, Vulpes vulpes . As a sensory adaptation, echolocation has evolved separately in cetaceans (dolphins and whales) and bats, but from
3000-404: The protein (positions 111 and 122). CTS-adapted species have also recurrently evolved neo-functionalized duplications of ATPalpha, with convergent tissue-specific expression patterns. Convergence occurs at the level of DNA and the amino acid sequences produced by translating structural genes into proteins . Studies have found convergence in amino acid sequences in echolocating bats and
3060-399: The same clade ; cladistics seeks to arrange them according to their degree of relatedness to describe their phylogeny . Homoplastic traits caused by convergence are therefore, from the point of view of cladistics, confounding factors which could lead to an incorrect analysis. In some cases, it is difficult to tell whether a trait has been lost and then re-evolved convergently, or whether
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#17330943714783120-468: The same direction and thus independently acquire similar characteristics; for instance, gliding frogs have evolved in parallel from multiple types of tree frog . Many instances of convergent evolution are known in plants , including the repeated development of C 4 photosynthesis , seed dispersal by fleshy fruits adapted to be eaten by animals, and carnivory . In morphology, analogous traits arise when different species live in similar ways and/or
3180-442: The same environmental and physical constraints are at work, life will inevitably evolve toward an "optimum" body plan, and at some point, evolution is bound to stumble upon intelligence, a trait presently identified with at least primates , corvids , and cetaceans . In cladistics, a homoplasy is a trait shared by two or more taxa for any reason other than that they share a common ancestry. Taxa which do share ancestry are part of
3240-467: The same genetic mutations. The Gymnotiformes of South America and the Mormyridae of Africa independently evolved passive electroreception (around 119 and 110 million years ago, respectively). Around 20 million years after acquiring that ability, both groups evolved active electrogenesis , producing weak electric fields to help them detect prey. One of the best-known examples of convergent evolution
3300-453: The surrounding water. Opahs prevent heat loss through their gills using a special structure in the gill blood vessels called the rete mirabile . The rete mirabile is a dense network of blood vessels where the warm blood flowing from the heart to the gills transfers its heat to the cold blood returning from the gills. Hence, the rete mirabile prevents warm blood from coming in contact with the cold water (and losing its heat) and also ensures that
3360-442: The surrounding water. This feature allows opahs to maintain an active lifestyle in the cold waters they inhabit. Unlike birds and mammals, the opah is not a homeotherm despite being an endotherm: while its body temperature is raised above the surrounding water temperature, it still varies with the external temperature and is not held constant. In addition to whole body endothermy, the opah also exhibits regional endothermy by raising
3420-400: The temperature of its brain and eyes above that of the rest of the body. Regional endothermy also arose by convergent evolution in tuna , lamnid sharks and billfishes where the swimming muscles and cranial organs are maintained at an elevated temperature compared to the surrounding water. The large muscles powering the pectoral fins generate most of the heat in the opah. In addition to
3480-554: The thumb, which develops from a wrist bone entirely separately from other fingers. Convergent evolution in humans includes blue eye colour and light skin colour. When humans migrated out of Africa , they moved to more northern latitudes with less intense sunlight. It was beneficial to them to reduce their skin pigmentation . It appears certain that there was some lightening of skin colour before European and East Asian lineages diverged, as there are some skin-lightening genetic differences that are common to both groups. However, after
3540-481: The two. When the ancestral forms are unspecified or unknown, or the range of traits considered is not clearly specified, the distinction between parallel and convergent evolution becomes more subjective. For instance, the striking example of similar placental and marsupial forms is described by Richard Dawkins in The Blind Watchmaker as a case of convergent evolution, because mammals on each continent had
3600-638: Was a resident of the Paratethys Sea and is estimated to have reached a length around 320 cm (130 in). At least one fossil species of Mola , M. pileata (van Beneden, 1881) , is known from the Upper and Middle Miocene of Europe with a possible second species known from the Lower Miocene of North Carolina , United States. The genus Ranzania has five known fossil species: R. grahami Weems, 1985 and R. tenneyorum Weems, 1985 , both from
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