"Huh?" How did my peacock fish keep it for so long without giving birth to a small fish..."?"
Have you ever been troubled by not being able to identify the sex of the fish you raise in your home? Hopefully, this article will provide you with some tips on gender discrimination in ornamental fish...
In some cases, the sex and male/female ratio of ornamental fish is crucial for aquarium lovers. In particular, the owners who want to enable the fish in the aquarium to breed the next generation, or who want to carry out intra- or interspecific polyculture. Therefore, this article will list the criteria for gender discrimination of various common representative fish species on the market in an illustrated manner, so that aquarium enthusiasts can use it as a basis for identification.
△ Wild-type peacock fish, the male fish has colorful colors and patches, the female fish do not; the male fish often chase the female fish for mating, so it is recommended to limit its proportions so as not to exhaust the female
▋ Sexual dichotomy
Differences between the sexes in the same species are called sex diformism (aka hermaphroditic or hermaphroditism; sexual dimorphism). Possible causes of sexual dimorphism include natural selection, sexual selection, and reproductive selection. Most of the hermaphroditic aliens are caused by sexual selection, such as female preference for males with specific characteristics, which will cause males to evolve exaggerated morphological characteristics, but females will maintain their original appearance due to environmental choices, such as the body color and fin performance of bream or fighting fish.
The most basic sexual heterogeneity is the reproductive structure, that is, the first sexual characteristics, but except for a few large ornamental fish such as the river stingray in the cartilaginous fish or the peacock fish (Guppy) in the oviparous fish, which have clearly visible genitalia, most ornamental fish (especially small fish) are usually not significant, or only show the first sexual characteristics (such as reproductive mastoids) during the reproductive period, so it is generally necessary to identify the sex of ornamental fish, usually based on their secondary sexual characteristics, including body size. Body color, fin length or fin size are judged by characteristics such as body color, fin length, or fin size.
However, not all species have high degrees of gender variation, and some species of adult fish differ only slightly in width and width at best, especially medium to large fish such as angelfish and colorful angelfish. In addition , in the juvenile period of most ornamental fish , because the sexual characteristics have not yet been highlighted , it is difficult to determine their sex from appearance , and the accuracy rate is not high , and they must wait until they have grown to the subadult stage to have a higher identification accuracy.
△ Red swordfish This type of fetal mackerel, like peacock fish, specializes in the fin of the male fish as an external reproductive organ - the reproductive limb (gonopod; also known as the adapter), which can be fertilized in vivo with the female
△ A small number of lipid carp species (about 5 %) can undergo in vivo fertilization, such as the S-hook in the center of the tail fin of the male (*Brittanichthys axelrodi*) with seminal vesicles in the center of the tail fin, which can also be used as a feature to identify sex
△ The bulbophyllum of the glandulocaudinae subfamily Mimagoniates, distributed in southeastern Brazil to Uruguay and other countries, has a tubular gland structure composed of deformed scales and fins in the center of the male tail fin, which can be fertilized in vivo like the blood fin lamp. Pictured here is a rainbow tricolor king lamp for males (side long hip carp; *M. lateralis*)
▋ Body color
The difference in body color between the sexes is also known as the sexual dichrogue. In general, 99% of fish males are more colorful than females (with the exception of small gillfish such as freshwater sea dragons or Veranti spacecraft), and this feature is particularly pronounced in cichlids or some small species such as fighting fish, oviparous mackerel or oviparous mackerel. However, for most other catfish such as large fish, catfish or ratfish, body color is usually not the main point of identification.
△ Dwarf cichlids from South America are taxa with obvious differences in sexual dichroir, with males with colorful bodies; females with a plain yellow-brown body color that turns more distinct goose yellow during the breeding season. Pictured represents the species - Akasi snapper (*Apistogramma agassizii*)
△ Cichlid from Lake Malawi in East Africa - Cynotilapia afra Jalo Reef also has a pronounced sexual dimorphism
△ Puntius snyderi dichotomy in cyprinids is also quite pronounced
△ The representative species of the genus Betta - the hemp fish (*B. imbellis*). The difference in body color between the sexes is obvious, and the males are gorgeous and aggressive, so it should be avoided to keep multiple males in the same tank at the same time
△ The difference in body color between the two sexes of the rat fish is usually not large, but there are a few fish species, with the exception of the blue moon rat (Pantanal mouse; Corydoras pantanalensis) and the gentleman mouse family fish species
△ Pelvicachromis kribensis Moliwe in the West African bream has different body color performance, the male is long and flat, the fins have rich colors and spots, and the females are short and round, and the abdomen is often purple-red
△ Some species of males even have specially extended, prominent fin decorations, such as the Mature male of the Apistogramma bitaeniata Tefe in the picture has extended dorsal fins, and the upper and lower ends of the tail fins are extended to form a harp-like tail; the females have flat and short fins without ornate decoration
△ The checkerboard seabream (Dicrossus filamentosus) in the South American bream, the male is full of bright blue metallic luster and red body color, and the tail is dragged with two long filamentary fins, as if wearing a tuxedo; the female is simple in color, usually only the ventral fin is orange
△ Among the small lipid carps, commonly known as flag-pulling, the species of Hyphessobrycon spp. varies greatly between the sexes, with males having exaggerated sail-like dorsal and fins; females are fat and shorter fins
△ The Pearl Gilet (Trichopodus leerii) is one of the representative species of gills in the Family Osphronemidae. Mature males have comb-like fins at the ends and are reddish in color
△ The red horsetail bucket fish, which is most commonly raised by beginners, has become more pronounced in the case of artificial selection and improvement of successive generations, and the difference in fins between the sexes has become more significant, and the males have wider and more beautiful fins
△ Rhabdalestes septentrionalis (also known as Golden Thread Green Congo) has different fin shapes in both sexes
△ Some of the catfish in the Callichthyidae family Are shown in the picture of corydoras semiaquilus, and the adult chariot rats of the Callichthyinae subfamily, whose sex can be distinguished from the thickness of their first pectoral fin bone, the male is usually particularly large, and the female is generally of normal size
△ Oreichthys crenuchoides in small carps are also obvious examples of sexual aliens, with the male's sail-like exaggerated dorsal fin contrasting with the female
△ Africa's most well-known medium-sized fat carp - Phenacogrammus interruptus , the male fish has more gorgeous, extended fins than the female fish, and the body color is also more beautiful
△ The dorsal, ventral and fins of the famous rock-dwelling cichlid of Lake Malawi - The Prince of Africa (Prince of Africa) (Prince of Africa) has black trims, but the male is distinctly thicker and darker
▋ Other features
In addition to body color, body size, and fin type, some fish have other sexual characteristics, such as some male carps that chase stars (or pearl organs) at the tip of the nose or snout; and the space flying squirrel (Scleromystax barbatus*) family of fish that have short hairy tentacles on the sides of the cheeks, which are symbols of individual maturity. In addition, some species of male small fat carp will appear on the fin, commonly known as Characin hooks, which are said to help fix the female during mating and can also be used to identify their sex.
△ The body color of males is far more colorful than that of females, but the Veranti spacecraft (*Sphaerichthys vaillanti*) in the mackerel is one of the special cases, and the females are far more vivid and beautiful than the males
△ Common species in the rainbow fish - Golden Beauty (*Melanotaenia herbertaxelrodi*) adults have a pronounced sexual dichromaticity
△ Like fighting fish or bream, killifish males are usually larger than females and have a more colorful body color. After the breeding season , they constantly show the female or her companions. Pictured here is the pentagram native to West Africa (*Aphyosemion striatum*)
▋ Body size and length
Body shape is also one of the factors that distinguish gender. Females are usually more plump than males, especially mature females tend to have a particularly swollen and plump abdomen, and fish such as fat carp, carp, ratfish, heterotypics, loaches and other fish can be judged by body shape. However, in juvenile or sub-adult stages, the difference in body size between the sexes is often not obvious, and other features must be relied upon to assist in identification. As for body length, most species of fish will be one size larger than the female, but there are several types of fish with exceptions, such as ratfish in catfish, the female is usually larger than the male, generally believed to be reproductive selection;
△ Ratfish can usually be distinguished by the size of the adult fish: the male is more streamlined, and the female is rounded. In addition, the shape of the abdominal fin of the male is usually sharper, and the female is more rounded (except for the wear of the abdominal fin, of course).
▋ Fins
Most males have a wider fin style than females, and some species of males may even have a particularly extended, prominent fin decoration, but some species have identical fins. In addition, some species have slightly different fin shapes, such as the fins of some lipid carp or paddy fish and the shape of the belly fins of ratfish, and the male and female of some fish are also very different in the color of the fins, such as the Lake Malawi cichlid, the Prince of Africa.
△ Some of the males of the red-nosed scissors (Hemigrammus rhodostomus) or dragonfly lamp (Iguanodectes spp.) have a row of distinct Characin hooks on the fin fins, and when fishing them with the net, the fish often only hang on the net because of these hooks
△ Small fat carp with a fiery red body - Nannostomus mortenthaleri (Flame Pencil) There is little difference in body color between the sexes, but the male is slightly larger than the female, and the front of the dorsal fin is usually white, which can be used as a key point for identification
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▋ Personality aspect
In fact, there are differences in personality between the sexes of fish, but it is difficult to quantify specifically. Males usually show significant territoriality and aggression in order to court with females or occupy breeding grounds, but this does not mean that females are necessarily very mild. In order to protect future generations, they will also fight to the death when they encounter other fish attacks!
Text & Photography @ Wang Zhongjing ( Taiwan)