Basic data:
Scientific name: Heterandria formosa (GIRARD, 1859)
Interpretation of words: Heterandria (heteros = other, andros = male), (formosa = beautiful - shape)
Group: Livebirds
Source: USA, Charleston, South Carolina and Palatka, Florida
Size: females up to 3.2 cm, males up to 2 cm
Biotope / Habitat: Shallow standing and slow flowing overgrown waters
Social behavior: Peaceful, fish flocks (10+)
Diet: Omnivore (worms, insects, insect larvae, crustaceans, flakes, algae, dry food, ...)
Cultivation: Easy
Aquarium: Minimum 15 liters per pair
Population: 10 fish per 50 liters of water
Decoration: Plants, stones, roots
Temperature: 20-26 ° C
pH: 7-8
Hardness: from 9 ° dGh to 20 ° dGh
Salinity max. 36.3 1,0 (1,027)
Lifespan: more than 3 years
Heterandria formosa
Kingdom: Animalia / animals
Trunk: Chordata / string players
Class: Actinopterygii / arthropods
Order: Cyprinodontiformes / Toothpicks
Family: Poeciliidae / live-bearing toothed carp
Genus: Heterandria
Species: Heterandria formosa (Girard, 1859)
Cultivation
Growing this very lively fish is extremely easy, tap water suits them perfectly, hard water with a neutral pH and a temperature of around 24 ° C.
Fish love fresh water, so change the water regularly, mild or nil water flow, vegetation and waving should be enough. We live with small livebirds (gupi), tetras or razbora, shrimp work great as roommates.
In nature it inhabits shallow, vegetation-rich water. These environments are often low oxygenated but rich in microorganisms.
Food
Omnivores, they like to eat various cereals, micro-worms, fleas, artemia, algae ..., emphasis on live food.
Reproduction
Heterandria is the smallest representative of live-bearing animals (one of the smallest species of fish / vertebrates in the world). Due to its small size, the species has developed superfetation, which means that it has the ability to develop several litters of different stages of development at the same time. As a result, in healthy and fertile females, the young are constantly "born", so every few days two or three fish are born that are only about 4 mm in size, the young immediately eat small live food (artemia, cyclops). Parents, in principle, do not eat the offspring so that we can have them together with the parents.
The species is viviparous, as the female provides food for the young - see here .
There is very little egg yolk, which is soon taken over by organs that act similarly to the placenta in mammals.
The development of the pups itself takes 4 to 8 weeks.
Description
Males are slender, the elongated body is moderately flattened laterally and about half smaller than the female, with a large gonopod. They are silver-gold in color, with a dark spot on the dorsal fin and a dark thick horizontal stripe from head to tail. The species tolerates short-term cooling to 15 ° C without damage.
Learn about natural habitats and wild fish
The species is distributed over a large coastal area in the southeastern United States, namely on the Atlantic coast and in the Gulf of Mexico, the states of North Carolina, Georgia, South Carolina, Florida, Alabama, Mississippi, Louisiana and Texas.
It is the only species of its kind in North America, the closest relative being found only on the Mexican Yucatan Peninsula, 1,500 kilometers to the south.
With the exception of Florida, where this species can be found in almost all of its territory, in other countries its geographical distribution is limited to coastal regions that do not penetrate more than 160 kilometers inland.
Wild populations refer to the Cape Fear River Basin in North Carolina to the Orange River Basin in the state of Texas.
This species is found mainly in regions with subtropical climates.
Climatologically, we analyze two different areas of its origin, so we will consider only the far north in the state of North Carolina and the far south in the state of Florida as reference areas.
In general, atmospheric conditions in North Carolina are typical of a humid subtropical climate.
Winters are short and moderate, and summers are generally hot, although air temperatures rarely exceed 38 ° C.
The average annual temperature is around 16.9 ° C.
In January, the average temperature in the coastal area is around 9 ° C, with the lowest values ranging from -2 ° C to 21 ° C.
In July, average temperatures are around 27 ° C, with the lowest 19 ° C and the highest 37 ° C.
Annual precipitation on the coast is between 1,120 and 1,420 mm.
Especially in summer, the atmosphere reacts with the high-pressure system in Bermuda, located in the Atlantic Ocean, causing the movement of humid and warm air to the North Carolina region.
The water temperature in the Cape Fear River ranges between 5.3 ° C to 31.9 ° C and the annual average is between 16.9 ° C and 19.8 ° C.
The pH of the water in this hydrographic basin ranges between 3.1 (in floodplain forest swamps) and 8.3, and the average is between 7.0 and 7.9, namely in the river and its tributaries.
The very low pH values recorded in wetlands are natural and are due to the abundance of organic acids.
In the far south, Florida has a very mild climate every year.
The average annual temperature ranges between 18 ° C and 21 ° C in the north and between 23 ° C and 25 ° C in the south.
The average annual temperature in Miami is 24 ° C.
The combined effect of latitude with the proximity of the Gulf of Mexico on the one hand and the Atlantic on the other makes this area variable between a humid subtropical climate and a humid semi-tropical climate.
Although precipitation is generally very high (1,200 mm to 1,450 mm, especially between June and September), there is also a lot of drought.
Water temperatures in the lakes and rivers of the state of Florida range from absolute extremes between 7 ° C and 39 ° C, and average annual averages range between 19.6 ° C and 23.3 ° C.
Water temperatures in the north of Florida are expected to be between 11 ° C and 28.5 ° C (annual average 19.6 ° C) and in the south between 17 ° C and 32.4 ° C (annual average 23.3 ° C). ).
The states of Mississippi, Louisiana, Texas and South Carolina are located between these two extremes (North Carolina and Florida), namely in the territory where Heterandria formosa is located in the natural environment.
In late summer and early autumn, this region is subject to hurricanes and tropical storms.
Heterandria lives mainly in lakes, ponds, forest swamps, canals, streams and slow streams. However, populations can be found in almost every freshwater and brackish aquatic environment.
Usually, this species is more associated with biotopes that are rich in underwater or aquatic vegetation (wetlands).
In nature, fish are closely related to the dense vegetation of some plant species, such as: Utricularia, Myriophyllum laxum, Myriophyllum heterophyllum, Myriophyllum pinnatum, Websteria, Utricularia foliosa, Utricularia juncea, Utricularia olivacea, Utricularia simulais, Sagitar , Sagittaria isoetigormis, Sagittaria subulata in Hydrilla verticillata.
Adult fish do not inhabit an environment with a water depth greater than 1 meter. As a result, this species mostly forms flocks at the edge of water bodies during dense vegetation.
Her favorite environment is characterized by clear or slightly turbid waters.
Source: http://www.viviparos.com/
Species biology
Heterandria is one of the more suitable species for life in captivity.
In a relatively small space, it is possible to maintain an entire population that is genetically viable and whose basic physico-chemical needs fully correspond to the home environment without the need for control.
Because it does not have such a pronounced exotic and dazzling color, it fascinates us with its facial expressions and lively and friendly behavior.
The chemical requirements of water are based only on a certain hardness, and at the same time have a high tolerance to pH.
The reproductive process stands out from their biology mainly due to the peculiarity that it is ovoviviparous and at the same time the most advanced and complete example of superfetation between live-bearing and ovoviviparous cyprinodontiforms.
Unlike many other species that give birth to living offspring, Heterandria formosa will give birth to its offspring for several days, one after the other, for a maximum of two at a time.
The fact that the female can retain sperm for a long time and that she has embryos at different stages of development together with mature and immature eggs, creates an unusual tendency in this species to multiple paternity.
Females maintained at constant temperatures or with small changes (very common in captivity) maintain a stable rhythm of pregnancy and childbirth at regular intervals.
Due to the physical dimensions of the species, it is very common for each litter (reached in several days) to reach a total of less than 10 offspring.
Reproduction of this species is disturbed mainly by lack of food or lack of dissolved oxygen in the water.
In the 20th century, lovers of developed countries located in colder climates tended to limit themselves to conserving species from temperate and cold climates or indigenous species.
Later, with the advent of efficient and affordable temperature control techniques for aquariums, more attractive tropical fish have become increasingly popular and replaced traditional species.
Currently, most aquarists find that maintaining and breeding fish from temperate regions is much more difficult and less beneficial than conventional ones selected for a tropical aquarium.
Although relatively low heat regimes are more demanding in winter, the good news is that all of these ovovivipar cyprinodontiforms and most live-bearing carp tolerate the summer heat that is common in captivity.
The first difference between tropical and temperate species is that the former generally do not have a defined breeding season, which means that their reproduction is continuous and is interrupted only by exceptional environmental factors.
As far as species from temperate regions are concerned, the "colder" periods of the year and the reduction in the number of light hours per day for fish very important, if not essential.
Heterandria does not need annual heat and light exchange, both intense and other species prevalent in colder regions, not least because populations in South Florida are already considered tropical fish. Nevertheless, it is advisable to follow slight and gradual environmental changes throughout the year in order to ensure, above all, healthy maintenance and reproduction of fish.
Even in the warmest area of geographical distribution, reproduction takes place only between March and October, which may correspond to 2, 3 or even 4 generations per year.
When females are constantly at high temperatures, reproductive exertion poses a great burden that can endanger the lives of the female and her offspring. Animals that have a rest period due to seasonal interruption of reproduction may recover more easily from this effort. In addition, all pregnancies in less favorable periods are usually smaller in terms of embryos, which is reflected in faster recovery after childbirth.
A constant temperature of 25 ° C allows well-fed females to give birth every four consecutive days in multiple births until all her embryos have been exhausted.
An increase of 2 ° C or 3 ° C may be enough to cause changes and, in particular, delay later birth. A sudden difference of a further 4 ° C or more almost always results in the loss of a few embryos.
The warmer the water, the higher the oxygen consumption of both females and their offspring.
The increase in births under the influence of artificial light is known, so the period of illumination should be taken into account in this species.
Unlike other live-bearing animals, this species has concrete evidence of some degree of viviparousness. At the very least, it is recognized that the mother does not only protect the development of offspring in the early stages of development. Through a very primitive type of placenta there is even a certain relationship and metabolic exchange between the mother and her offspring during pregnancy.
Otherwise, oxygen supply and diet would not affect the length of pregnancy and the size of the offspring at birth.
At the top of the heat scale of suitable values for reproduction, oxygen plays a very important role in embryo development, while on the other hand, nutrition and the amount of food available play this role.
Interestingly, offspring bred at 20 ° C are more tolerant of high temperatures than those bred at 26 ° C, but the overall resistance of those bred at 26 ° C is higher than those bred at 20 ° C. at 21 ° C.
It has been scientifically proven that larger offspring find it easier to survive periods of famine soon after birth and grow faster than smaller offspring.
Sexual maturity in this species is reached between 45 and 65 days of life, and the average lifespan of wild animals is between 130 and 170 days, while in an aquarium it can easily exceed one year of life.
The average time of the entire pregnancy is about 5 weeks.
Given that generations inherit from each other in such a short time, there is great genetic variability between populations (sometimes even in the same hydrographic system).
This speculation may lead us to worry that this species is much more vulnerable to inbreeding than most of its closest relatives, so it is advisable to maintain as many individuals as possible and frequent specimen exchanges between isolated groups.
This fact, coupled with the high multiplicity described in some scientific papers, may explain the gender imbalance that occurs in some aquarium strains.
As these are tropical invertebrate animals, their diet in nature consists mainly of invertebrates of a size suitable for their small mouths (micro invertebrates), and sometimes of plant substances.
In captivity, the main concern for proper nutrition is undoubtedly the size of the food. Puppies can especially suffer from high mortality rates due to lack of adequate food for their tiny mouths.
Adults take very well the usual purchased food in flakes, as long as we take care to grind it into small enough particles (or grind it into powder).
Since they are hidden among the plants for the first few days, the only way to get food is to drop their food directly on the places where the young people have taken refuge.
Small aquatic invertebrates (daphnia, cyclops, infusoria, etc.), newly hatched aquatic snails and zooplankton are best suited for feeding this species. Occasionally it is good not to forget about any plant ingredient in the diet of animals in aquariums.
