Glandulocaudinae | |
---|---|
Argopleura magdalenensis | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Actinopterygii |
Order: | Characiformes |
Family: | Characidae |
Subfamily: | Glandulocaudinae |
Genera | |
Acrobrycon Contents |
Glandulocaudinae are a subfamily of tropical freshwater characin fish from Central and South America. In all species of this subfamily, a gland on their caudal fin is found almost exclusively in the males, which allows the release and pumping of pheromones; also, members of this subfamily have complex courtship behaviors which lead to insemination. The ecology and life history of these fish is complex yet little studied. [1] Glandulocaudines are important as food fish for larger fish important for commercial and subsistence reasons. [1]
Glandulocaudinae consists of twenty genera divided among seven monophyletic, morphologically differing tribes. The monophyly of the subfamily itself needs much further investigation. [1] There are about 60 species. [2] [3] However, there remain many undescribed species. [4]
Glandulocaudines occur in practically all major South American drainages. [2] Along Pacific drainages, they are distributed from Costa Rica to Ecuador, and along Atlantic drainages, their range extends to northern Argentina. [3] [5] These fishes are found in every South American country, including Trinidad and excluding Chile; they inhabit streams that are tributaries to larger rivers such as the Amazon, Orinoco, and Paraguay Rivers in tropical species, or coastal streams tributary to the Atlantic and Pacific Oceans and the Caribbean Sea in the few subtropical species. [1]
The habitats of these fish vary. A few species are known from elevations as high as 500–600 metres (1,600–2,000 ft), and Lophiobrycon weitzmani is known as high as 900 m (3,000 ft). [1] [2] Some species are confined to acidic black rainforest waters, and others are found in clearer, neutral to somewhat alkaline waters; a few species are even adapted to both kinds of waters. However, there are no brackish water species. [1]
Glandulocaudines are small, less than 13 centimetres (5 in). [2] Most are between about 5–6 cm SL (about 2 in), but some species can be even smaller, between 11 and 30 millimetres (0.43 and 1.18 inches). [1] The reproductive adaptations of glandulocaudines is what sets this group apart from the other Characins. Males have a caudal organ associated with gland tissues. Synapomorphies of this subfamily include insemination, a posterior sperm storage area in the testes, and an elongate sperm nucleus. [5]
All males have some form of modified caudal gland used to release pheromones as part of courtship. [3] The structure of this gland depends on the specific tribe; the organ may consist of modified caudal fin rays; modified caudal fin scales, a derived hypural fan, or modified caudal fin musculature, or combinations of the above. [1] Modified scales may act as bellows in releasing chemicals into the water. [3] A caudal fin ray pheromone pump, unique to tribe Glandulocaudini, consists of glandular tissue associated with modified scales and fin rays. [2] The tribe Diapomini is the only tribe in which the caudal gland is equally developed in both the males and females. [5]
Females of all glandulocaudine species are inseminated. [2] The females produce fewer eggs per unit body weight than externally fertilizing species; this is possibly because insemination increases the efficiency of fertilization, so fewer eggs are necessary. [5] This insemination is preceded by courtship in all species. [3] After insemination, the female may retain the live sperm for many months in her ovaries. [1] [2] This allows the eggs to be laid when environmental conditions are favorable. [5] However, there is no evidence of an intromittent organ, and the exact mechanism of insemination is unknown. [5] [6] Hooks on the anal fin of males may play a role, although these are also found in characins that exhibit external fertilization. [3] [5] It was originally believed that internal fertilization occurs in glandulocaudines. [7] [8] However, the exact time of fertilization is unknown and no fertilized eggs are found internally; this suggests fertilization occurs when the eggs are being laid or even outside of the body. [5]
Due to insemination, the sperm of glandulocaudines has adapted. [6] In many species, an elongate cytoplasmic collar binds the flagellum to the elongate nucleus at some stage of spermiogenesis. [6] In almost all species, the sperm cell bodies are elongate. In the tribe Diapomini, the genus Planaltina expresses only round sperm (like that of externally fertilizing characins) and the genera Diapoma and Acrobrycon only express slightly elongated sperm; this may indicate a possible plesiomorphy. [5] Some sperm have enlarged regions containing mitochondria, which may help in prolonging the life of the sperm while stored in the ovary. [6] In some genera, sperm clumping and patterns of arrangement are observed in the sperm ducts and storage regions. [5] In the tribes Xenobryconini (in the genera Tyttocharax, Scopaeocharax, and Xenurobrycon) and Glandulocaudini, there is a form of sperm packaging which would allow for a higher sperm density during transfer from the male to the female. These packets are called spermatozeugmata, and the sperm are packaged parallel to each other; this packaging is further increased by the elongation of the sperm cells. In Xenobryconini, each spermatozeugma is produced and is released fully formed in the spermatocysts, but in Glandulocaudini, the sperm is released from the spermatocysts and packaged elsewhere. The spermatozeugmata are situated in the posterior end of the testes, which serves as a storage area for sperm. [6]
Many of the genera also have a gland situated in the gill cavity called a "gill gland", a secondary sex characteristic found in sexually mature male glandulocaudines that is apparently suited to release chemical signals. No genus contains species that have glands and other species without glands. This gill gland is derived from anterior gill filaments of the first gill arch. Gland size and degree of gill modification varies with species. Though the true function of the gill glands has yet to be determined, they are probably used to release chemical signals into the gill current. [3]
There are many examples of sexual dimorphism (differences in appearance between the genders). In Corynopoma riisei , the males have extended finnage (giving it the common name "swordtailed characin") as well as paddle-like extensions of the operculum. [7] [8] Many other species also have other secondary sex characteristics believed to be involved in courtship. [5]
Many of these characteristics are also shared with the tribe Compsurini in Cheirodontinae. Though unrelated, this group contains inseminating species with caudal organs. However, the caudal organs and other similar characteristics are structured differently. [1] They also share the elongate cytoplasmic collar binding the flagellum to the elongate nucleus at some stage of spermiogenesis, which was previously assumed to be exclusive to glandulocaudines. [6] These fish also occasionally have gill glands. [3]
Like other ostariophysans, glandulocaudines show a reaction to chemical signals in the water. Many ostariophysans have a fright reaction in response to an alarm substance. [4] In Corynopoma riisei , it has been shown that a sexually mature male's presence actually inhibits the maturation of immature males. In C. riisei, the female is often situated parallel to and somewhat behind the male, which allows for chemical signals released from the male's gill glands to be carried directly to the female. [3]
Glandulocaudines have complex courtship behavior. In C. riisei, the male has paddle-shaped extensions of the operculum which can be extended perpendicular to its body and twitches and flutters due to movements of his body; the female follows and nips at these projections during courtship. [7]
A croaking behavior is recorded in some species of Mimagoniates . [8] This behavior has a part in courtship as well. Courtship involves the male chasing and hovering near the female. As the male hovers, he will quickly swim to the surface and take a gulp of air and return, expelling the gas and making continuous, rhythmic pulses of croaking sounds, interrupted only by the male returning to the surface for more air. The fish also zigzags while hovering by swimming up and down, when the fish intends to resurface but does not. [9] Croaking behavior may have evolved from a behavior called "nipping surface", a feeding behavior that occurs when the fish is searching for food; the fish often will gulp air when doing this. This gulping of air has no respiratory significance. [9]
Some species of Glandulocaudinae are important in the aquarium trade. [1] Herbert R. Axelrod has discussed the care of a number of species, including Corynopoma riisei, Gephyrocharax caucanus, Mimagoniates microlepis , M. lateralis , M. inequalis , Pseudocorynopoma doriae, and Tyttocharax madeirae. [8] These species reach about 5–6 cm (about 2 in). However, T. madeirae reaches 2 cm (less than 1 in), while P. doriae reaches 8 cm (3 in). Like most tetras, they prefer to swim in schools; some species may be nippy, and should be kept in groups to divide aggression. Many species are very active and will almost constantly swim, which translates to a larger aquarium. They have been bred in captivity. [8]
These fish may not be as easily weaned onto dry foods as other fish, and will appreciate live foods. Some species appreciate cooler water than the average tropical fish, so this should be kept in mind when maintaining some of these species. Also, many imported specimens, even if they seem healthy, may mysteriously waste away. Some species are delicate and are not easily collected or transported, or are rarely seen available. [8]
Species list is according to FishBase. ITIS does not list Characin subfamilies as they believe subfamilies are likely to change. [10]
Tribe Landonini
Tribe Glandulocaudini
Tribe Diapomini
Tribe Phenacobryconini
Tribe Hysteronotini
Tribe Corynopomini
Tribe Xenurobryconini
Characidae, the characids or characins, is a family of freshwater subtropical and tropical fish belonging to the order Characiformes. The name "characins" is an historical one, but scientists today tend to prefer "characids" to reflect their status as a, by and large, monophyletic group. To arrive there, this family has undergone much systematic and taxonomic change. Among those fishes remaining in the Characidae currently are the tetras, comprising the very similar genera Hemigrammus and Hyphessobrycon, as well as a few related forms, such as the cave and neon tetras. Fish of this family are important as food in several regions, and also constitute a large percentage of captive freshwater aquarium fish species.
In biology, mating is the pairing of either opposite-sex or hermaphroditic organisms for the purposes of sexual reproduction. Fertilization is the fusion of two gametes. Copulation is the union of the sex organs of two sexually reproducing animals for insemination and subsequent internal fertilization. Mating may also lead to external fertilization, as seen in amphibians, fishes and plants. For most species, mating is between two individuals of opposite sexes. However, for some hermaphroditic species, copulation is not required because the parent organism is capable of self-fertilization (autogamy); for example, banana slugs.
Tetra is the common name of many small freshwater characiform fishes. Tetras come from Africa, Central America, and South America, belonging to the biological family Characidae and to its former subfamilies Alestidae and Lebiasinidae. The Characidae are distinguished from other fish by the presence of a small adipose fin between the dorsal and caudal fins. Many of these, such as the neon tetra, are brightly colored and easy to keep in captivity. Consequently, they are extremely popular for home aquaria.
Insemination is the introduction of sperm into a female's reproductive system in order to fertilize the female for sexual reproduction. The sperm is introduced into the uterus of a mammal or the oviduct of an oviparous (egg-laying) animal. Female mammals are inseminated during sexual intercourse/copulation, but can also be inseminated by artificial insemination.
The bronze corydoras, also known as the green corydoras, bronze catfish, lightspot corydoras or wavy catfish, is a species of freshwater fish in the armored catfish family, Callichthyidae, often kept as an aquarium fish. It is widely distributed in South America on the eastern side of the Andes, from Colombia and Trinidad to the Río de la Plata basin; however, as presently defined it is a species complex and a taxonomic review is necessary. It was originally described as Hoplosoma aeneum by Theodore Gill in 1858 and has historically also been referred to as Callichthys aeneus.
Nannostomus is a genus of fish belonging to the characin family Lebiasinidae. All of the species in this genus are known as pencil fish, a popular name that was initially only applied to two species in the 1920s, Nannostomus unifasciatus and Nannostomus eques, by the late 1950s however, the term would be applied to all members of the genus. Several species have become popular aquarium fish due to their attractive coloration, unique shape, and interesting demeanor.
Mimagoniates microlepis, also known as the blue tetra, the croaking tetra, the small-scaled tetra, is a species of tetra in the genus Mimagoniates. First identified by Franz Steindachner in 1876 and named Coelurichthys microlepis, it has also been identified as Coelurichthys iporangae, Coelurichthys lateralis, and Mimagoniates iporangae besides its current taxonomic classification. There is evidence of a variety called M. microlepis 'Joinville' which might be synonymous with Paragoniates microlepis.
Mimagoniates is a genus of characid fish from rivers and streams in southeastern, southern and central-western Brazil, northeastern Argentina, and Paraguay. The individual species generally have relatively small ranges and two, M. lateralis and M. sylvicola, are considered threatened by Brazil's Ministry of the Environment.
Corynopoma riisei, also known as the sword-tail characin, is a species of characin found in Colombia, Trinidad and Tobago and Venezuela. It is also kept as an aquarium fish. This species is the only member of the genus Corynopoma.
Diapoma is a genus of characins from tropical South America.
Glandulocauda is a genus of small characin freshwater fish that are endemic to Brazil, where restricted to the upper Paraná basin and coastal river basins in São Paulo state. The genus it is closely related to Lophiobrycon and Mimagoniates, and they form the tribe Glandulocaudini.
Iguanodectes is a genus of freshwater fish found in tropical South America, with eight currently described species. They are all small tetras, none longer than 5 inches, and often have attractive silvery or striped scales, which makes them a target for the ornamental fish industry. Alongside the genus Piabucus, it is in the subfamily Iguanodectinae, which in turn is in the family Iguanodectidae. The genus Bryconops, which is also in Iguanodectidae, makes up a sister clade to Iguanodectinae.
Monotocheirodon is a genus of characins native to tropical South America. The currently recognized species in this genus are:
Planaltina is a genus of characins endemic to Brazil.
Tyttocharax is a genus of characins found in tropical South America.
Ectrepopterus uruguayensis is a small species of characin originally recorded only from streams in Uruguay, with occasional sightings in Brazil and Argentina. It is the only known member of the genus Ectrepopterus, which was formerly a subgenus of Megalamphodus. Given its restricted range, it is considered a rare fish, and is of note for conservation researchers interested in preserving the biodiversity of the region.
Carlastyanax aurocaudatus is a small species of freshwater fish in the family Characidae native to the Río Cauca in Colombia. It is the only member of the monotypic genus Carlastyanax, which was named in 1972 specifically for the species by Jacques Géry. Upon description, it was named Astyanax aurocaudatus by Carl H. Eigenmann. There has been debate concerning whether or not the genus should be recognized, but C. aurocaudatus is currently considered a valid species.
Iguanodectinae is a subfamily of small freshwater fish in the family Iguanodectidae. They are most prominently found in the Amazon river basin and its major tributaries, but they are also known from the Tocantins, Orinoco, and Paraguay rivers. It has two genera, Piabucus and Iguanodectes. Some species in the subfamily are taken from the wild for aquariums, like the red- and green-line lizard tetras. There is minor, but ongoing, debate regarding its taxonomy.
Bryconops alburnoides is a small freshwater fish, approximately 6 inches long at its largest, that lives in the rivers of South America. It has a slender body, with a yellowish dorsal fin and yellow-tinged back scales that fade into silver on its belly. It is largely an insectivore that picks land-dwelling insects from the riverbanks, though it eats much more whenever rain washes prey into the water.
Deuterodon heterostomus is a small species of characin endemic to a large river system in southeast Brazil. It was originally the only member of the genus Probolodus, but Probolodus is now considered obsolete, synonymized with Deuterodon. Much like other members of Deuterodon, and like some fish in related genera, D. heterostomus is a small, silvery fish with fins in some combination of red and clear. It has a defined humeral spot that can be used for identification.
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