Amazon molly | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Actinopterygii |
Order: | Cyprinodontiformes |
Family: | Poeciliidae |
Genus: | Poecilia |
Species: | P. formosa |
Binomial name | |
Poecilia formosa (Girard, 1859) | |
Synonyms [2] | |
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The Amazon molly (Poecilia formosa) is a freshwater fish native to the warm waters of northeastern Mexico and the southern parts of the U.S. state of Texas. [1] [3] It reproduces through gynogenesis, and essentially all individuals are females. The common name of "Amazon molly," acknowledges this trait as a reference to the Amazon warriors, a female-run society in Greek mythology. [4] The Amazon molly is a hybrid species, and its parent species are the sailfin molly (Poecilia latipinna) and the Atlantic molly (Poecilia mexicana). [5] In 1932, this species was the first vertebrate confirmed to be capable of asexual reproduction. [6]
Poecilia formosa gets its name from the Greek poikilos meaning "variegated" or "speckled," and the Latin formosa meaning "beautiful." [7]
The Amazon molly shares many of the same general characteristics of its parent species. Some of these characteristics include a rounded caudal fin, a small anal fin, small pelvic fins, pectoral fins located just behind the operculum, a small terminal mouth, and a compressed body shape. They are silver in color and are usually observed to have rows of reddish-brown spots along their sides. They are a small fish with an average length of 5.5cm. The maximum documented length for this species was recorded at 9.6cm. [8]
Amazon mollies have a small dorsal fin consisting of 10-12 soft rays. [9] The position of the dorsal fin on the back of the fish is anterior, closer towards the head, than the position of the anal fin on the underside of the fish. They do not have any spiny rays on their fins. [10]
The Amazon molly is native only to North America. Its habitat range extends from the Tuxapan River in northeastern Mexico to the Rio Grande and the Nueces River in southern Texas. [11] The hybridization event that resulted in the formation of the species Poecilia formosa is believed to have occurred near Tampico, Mexico. Distribution of the species would then have occurred outward from that region. [12]
In the 1930s, P. latipinna was introduced to the San Marcos River in central Texas. [13] A couple of decades later, in the 1950s, a few individuals of P. formosa were also introduced into the river. P. formosa was able to reproduce by using male P. latipinna as sperm donors, which allowed their population in the San Marcos to grow. [14]
Ecological Niche Modeling
The geographical range of the Amazon molly has been the primary research question of multiple scientific studies. Each of its parent species have a geographical range that extends beyond that of P. formosa. [15] P. mexicana's range extends from the Rio San Fernando drainage in northeastern Mexico southward into Costa Rica and Honduras. P. latipinna's range is more northern beginning around Veracruz, Mexico up to the U.S. state of North Carolina. The Amazon Molly only occupies a fraction of its parent species' habitats. [16]
In a study completed in 2010, researchers were able to identify two probable causes for the truncation of the habitat of the Amazon molly using a method called Ecological Niche Modeling (ENM). [17] At the northern limit of their native range, it was found that, even though sperm donor species were available, the environmental conditions were not suitable enough for the Amazon molly to thrive. At the southern limit of their native habitat, there was found to be both sperm donor species availability and suitable environmental conditions, indicating that dispersal availability was the limiting factor. Additionally, ENM found that the only suitable habitat not already occupied by the Amazon molly is in south Florida. [18]
The range of the Amazon molly overlaps somewhat with that of its parent species, but as a hybrid of two species with different ecological niches, it occupies its own distinct niche that lies somewhere between that of its parent species. [19]
P. formosa is an omnivore and feeds on both plant and animal matter. [20] Potential food items for the Amazon molly would include algae and small invertebrates like insects. Like other molly species, P. formosa prefers to live in sluggish, slow-moving bodies of water. [21] They have a lifespan of three to five years in captivity, but they are believed to live closer to five years in the wild. [22]
Reproduction is through gynogenesis, which is sperm-dependent parthenogenesis. This means that females must mate with a male of a closely related species, but the sperm only triggers reproduction and is not incorporated into the already diploid egg cells the mother is carrying (except in extraordinary circumstances). This results in clones of the mother being produced en masse. [23] This characteristic has led to the Amazon molly becoming an all-female species. [24] Other all-female species include the New Mexico whiptail, desert grassland whiptail lizard, and blue-spotted salamander.
In nature, the Amazon molly typically mates with a male from one of four different species, either P. latipinna , P. mexicana , P. latipunctata , or occasionally P. sphenops . [26] One other male that could possibly exist in the Amazon molly's natural range that could induce parthenogenesis in Amazon molly females is the triploid Amazon molly male.[ citation needed ] These triploid males are very rare in nature and are not necessary in the reproduction of the species, which is why the species is considered to be all female.[ citation needed ]
Since the male's sperm is not contributing to the genetic makeup of the offspring, it may seem non-beneficial for males of closely related species to participate in mating with the Amazon molly, though research shows that females of other species, such as the Atlantic molly, are trend conscious and are more likely to mate with a male of their species if they see that male mate with an Amazon molly. [27] Therefore, the Amazon molly can only live in habitats that are also occupied by a species of male that will reproduce with them. [24]
The Amazon molly reaches sexual maturity one to six months after birth, and typically has a brood between 60 and 100 fry (young) being delivered every 30–40 days. This lends itself to a large potential for population growth as long as host males are present. The wide variability in maturity dates and brood sizes is a result of genetic heritage, varying temperatures, and food availability. They become sexually mature faster and produce larger broods in warm (approximately 27 °C or 80 °F) water that provides an overabundance of food. [28]
The Amazon molly has been reproducing asexually for about 100,000-200,000 years. [29] This is about 500,000 generations of Amazon molly. Asexual lineages typically go extinct after 10,000-100,000 generations. [23] There is research being done to determine how the Amazon molly has not gone extinct or developed a Muller's ratchet of mutations. Researchers believe the answer is in the genome of the Amazon molly, [30] yet more research must be done to determine this.
P. formosa is a hybrid species and P. mexicana is one of the parental species. [31] Its other progenitor is most likely an extant, as yet undescribed, subspecies of P. latipinna or an extinct ancestor of P. latipinna.
The Amazon molly is regularly used in scientific research, particularly in the fields of biology, genetics, and evolutionary science. [32] This is largely due to the all-female, unisexual nature of the species as well as its unique means of asexual reproduction. It is also an easy fish to maintain in captivity, making it an ideal subject to keep in a laboratory setting. [33]
While the Amazon molly is not used in the pet trade, other molly species such as the sailfin molly, short-fin molly, and other selectively bred molly hybrids are commonly found in pet stores. [34]
The conservation statures of Poecilia formosa by the International Union for the Conservation of nature (IUCN) was last assessed on 26 February 2019. Presently, the species is listed as Least Concern meaning there is not a high risk of extinction. However, the population trend in unknown. There is no data about whether the population might be growing or declining. [35]
Though localized threats such as pollution and other human disturbances to natural habitat could exist, there are currently no known threats to the Amazon molly. [36]
Asexual reproduction is a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes. The offspring that arise by asexual reproduction from either unicellular or multicellular organisms inherit the full set of genes of their single parent and thus the newly created individual is genetically and physically similar to the parent or an exact clone of the parent. Asexual reproduction is the primary form of reproduction for single-celled organisms such as archaea and bacteria. Many eukaryotic organisms including plants, animals, and fungi can also reproduce asexually. In vertebrates, the most common form of asexual reproduction is parthenogenesis, which is typically used as an alternative to sexual reproduction in times when reproductive opportunities are limited. Some monitor lizards, including Komodo dragons, can reproduce asexually.
The western mosquitofish is a North American freshwater poeciliid fish, also known commonly, if ambiguously, as simply mosquitofish or by its generic name, Gambusia, or by the common name gambezi. Its sister species, the eastern mosquitofish is also referred to by these names.
Poecilia is a genus of fishes in the family Poeciliidae of the order Cyprinodontiformes. These livebearers are native to fresh, brackish and salt water in the Americas, and some species in the genus are euryhaline. A few have adapted to living in waters that contain high levels of toxic hydrogen sulfide and a population of P. mexicana lives in caves.
The sailfin molly is a livebearer fish typically found in both freshwater and brackish waterways along the East Coast of the United States, from North Carolina south to Florida, and around the Gulf of Mexico to Texas, and south to the Yucatán Peninsula of México. Given their preference for more brackish water conditions, mollies are often found within just a few yards or miles of the ocean, inhabiting coastal estuaries, lagoons, river deltas and swamps, as well as tidal areas with a regular inflow of oceanic minerals and nutrients mixing with inland freshwater sources.
Fish reproductive organs include testes and ovaries. In most species, gonads are paired organs of similar size, which can be partially or totally fused. There may also be a range of secondary organs that increase reproductive fitness. The genital papilla is a small, fleshy tube behind the anus in some fishes, from which the sperm or eggs are released; the sex of a fish can often be determined by the shape of its papilla.
Limia is a genus of livebearing fishes belonging to the Cyprinodontiform family Poeciliidae. It comprises 22 described species found in fresh, brackish, saltwater, and hypersaline habitats of the Greater Antilles islands in the Caribbean Sea. A vast majority are endemic to Hispaniola. There has been a long-running debate on whether Limia should be considered a subgenus of Poecilia rather than a full genus. Most Limia species are detrivores and herbivores. Due to their small size and coloring, they are sometimes kept in home aquaria.
Parthenogenesis is a natural form of asexual reproduction in which the embryo develops directly from an egg without need for fertilization. In animals, parthenogenesis means development of an embryo from an unfertilized egg cell. In plants, parthenogenesis is a component process of apomixis. In algae, parthenogenesis can mean the development of an embryo from either an individual sperm or an individual egg.
Poecilia velifera, known as the Yucatan molly and also as the giant sailfin molly amongst aquarists, is a large livebearer that lives in coastal waters of the Yucatan Peninsula. These live-bearer (Poeciliidae) fish are particularly well known for both the extreme size variation among males, and the sexual dimorphism between males and females in both body shape and behavior.
Hypoplectrus gummigutta, commonly called the golden hamlet, is a species of marine ray-finned fish. They are sea bass from the subfamily Serraninae and the greater family Serranidae, which also includes the groupers and anthias. The golden hamlet was first described in 1852 by zoologist Felipe Poey (1799-1891) as Plectropoma gummigutta before being given its accepted name: Hypoplectrus gummigutta. It is found in the western Atlantic Ocean and occasionally makes its way into the aquarium trade.
The shy hamlet is a small Western Atlantic serranid fish, which belongs to the subclass perciformes in the class Actinopterygii. To this date, seventeen species of the genus Hypoplectrus have been recognized, a third of which have been discovered in the past few years.
Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete with a single set of chromosomes combines with another gamete to produce a zygote that develops into an organism composed of cells with two sets of chromosomes (diploid). This is typical in animals, though the number of chromosome sets and how that number changes in sexual reproduction varies, especially among plants, fungi, and other eukaryotes.
The guppy, also known as millionfish or the rainbow fish, is one of the world's most widely distributed tropical fish and one of the most popular freshwater aquarium fish species. It is a member of the family Poeciliidae and, like almost all American members of the family, is live-bearing. Guppies originate from northeast South America, but have been introduced to many environments and are now found all over the world. They are highly adaptable and thrive in many different environmental and ecological conditions. Male guppies, which are smaller than females, have ornamental caudal and dorsal fins. Wild guppies generally feed on a variety of food sources, including benthic algae and aquatic insect larvae. Guppies are used as a model organism in the fields of ecology, evolution, and behavioural studies.
Mate-choice copying, or non-independent mate choice, occurs when an individual of an animal species copies another individual's mate choice. In other words, non-independent mate-choice is when an individual's sexual preferences get socially inclined toward the mate choices of other individuals. This behavior is speculated to be one of the driving forces of sexual selection and the evolution of male traits. It is also hypothesized that mate-choice copying can induce speciation due to the selective pressure for certain, preferred male qualities. Moreover, mate-choice copying is one form of social learning in which animals behave differently depending on what they observe in their surrounding environment. In other words, the animals tend to process the social stimuli they receive by observing the behavior of their conspecifics and execute a similar behavior to what they observed. Mate choice copying has been found in a wide variety of different species, including : invertebrates, like the common fruit fly ; fish, such as guppies and ocellated wrasse; birds, like the black grouse; and mammals, such as the Norway rat and humans. Most studies have focused on females, but male mate copying has been also found in sailfin mollies and humans.
In biology, a klepton and synklepton is a species that requires input from another biological taxon to complete its reproductive cycle. Specific types of kleptons are zygokleptons, which reproduce by zygogenesis; gynokleptons which reproduce by gynogenesis, and tychokleptons, which reproduce by a combination of both systems.
Gynogenesis, a form of parthenogenesis, is a system of asexual reproduction that requires the presence of sperm without the actual contribution of its DNA for completion. The paternal DNA dissolves or is destroyed before it can fuse with the egg. The egg cell of the organism is able to develop, unfertilized, into an adult using only maternal genetic material. Gynogenesis is often termed "sperm parasitism" in reference to the somewhat pointless role of male gametes. Gynogenetic species, "gynogens" for short, are unisexual, meaning they must mate with males from a closely related bisexual species that normally reproduces sexually.
Limia melanogaster, the black-bellied or blue limia, is a poeciliid fish from Jamaica. It inhabits fast-flowing streams. It is a rare livebearer in modern fishkeeping.
Poecilia kykesis, also known as the Usumacinta molly, Petén molly, spiketail molly, or swordtail molly, is a poeciliid fish species native to the fresh and brackish waters of Mexico, Guatemala, and Belize. It belongs to the sailfin molly clade, with males exhibiting an enlarged dorsal fin. The species has a notably controversial naming history, with the former name, Poecilia petenensis, now referring to a short-finned molly species. It is a livebearer sometimes kept in aquaria.
Poecilia gillii, Gill's molly, is a herbivorous livebearer fish distributed throughout Central America. It is found in both moving and still water as well as in both freshwater and brackish habitats. Populations of this species differ in color, size, and morphology.
Poecilia orri, the mangrove molly, is a brackish-water livebearer fish from Central America. Two morphs exist, differing in size, body shape, and coloring.
Poecilia vandepolli, or Van de Poll's molly, is a poeciliid fish native to the ABC islands of the Lesser Antilles, namely Aruba, Bonaire, and Curaçao. It is a euryhaline species and one of the most common fish in its range, inhabiting fresh, brackish, salt, and hypersaline waters. The fish vary significantly in size and color depending mostly on the salinity of their environment. The saltwater specimens grow faster and become more robust and more colorful, but the species is drawn to the freshwater habitats which disappear in each dry season and must be recolonized when the rains return.