How many species of knife fish are there?


What kind of body does a knifefish have?

Like the other gymnotiforms, gymnotids have classic knifefish bodies. The body is long and eel-like, the dorsal fin and pelvic fins are absent, and the anal fin is extremely long and used for movement.

What are the names of the three types of eels?

They are placed in three families: Gymnotidae (often called gymnotid “eels”); Apteronotidae; and Rhamphichthyidae. Some authorities, however, group all, together with the related electric eel, in a single family, Gymnotidae, while others recognize more than three families.

What is the difference between male and female knife fish?

This fish also has a pelvic fin which is relatively short and does not cover the urogenital part. The male Knife Fish has a longer pelvic fin and closes the urogenital part, tube-shaped genitals, smaller in size than the female. So, here are some of the most popular types of ornamental Knife fish in the world.

How can you tell the difference between a male and female knife?

During spawning is the easiest time to tell the difference between the male and female. the female Knife will be rounder in shape and more colorful around this time. She will the lay around 200 eggs and guard them until they hatch.

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Is there dimorphism between male and female BBK fish?

There is no dimorphism between the sexes. They only way to tell is during spawning and yes, they have been successful spawned in home aquariums, but it is extremely difficult. Almost all BGK will reach a minimum of 30cm or 12″ with 60cm or 24″ being the largest. I would say 90g (340liters) minimum.

What is the difference between male and female mahsser fish?

The Pectoral, pelvic and anal fins Mahsser (Tor tor) are also black in colour in males. Females are silvery white with a deep pink lateral band, dorsal and caudal fins with Male fish is smaller and its body narrower as compared to black edges, and pectoral, pelvic and anal fins with light female fish of the same age group.

Is sexual dimorphism determined by genetics or the environment?

Sexual dimorphism is a product of both genetics and environmental factors. An example of sexual polymorphism determined by environmental conditions exists in the red-backed fairywren.

What causes sexual dimorphism in lizards?

The sexual dimorphism in lizards is generally attributed to the effects of sexual selection, but other mechanisms including ecological divergence and fecundity selection provide alternative explanations. The development of color dimorphism in lizards is induced by hormonal changes at the onset of sexual maturity,…

What is dimorphism in animals?

The condition occurs in many animals and some plants. Differences may include secondary sex characteristics, size, weight, color, markings, and may also include behavioral and cognitive differences. These differences may be subtle or exaggerated, and may be subjected to sexual selection. The opposite of dimorphism is monomorphism.

Do fish have hermaphrodites?

Only in Perciforms (fish) does hermaphroditism occur naturally and in high frequency. Hermaphrodites are divided into two main categories: synchronous hermaphrodites, and sequential hermaphrodites. In the synchronous hermaphrodites, organisms possess both active male and active female reproductive organs at the same time.

What is Mahseer fish called in English?

It is also found in Nepal, where it is called sahar. (British anglers in India called them the Indian salmon.) In Indonesia/Malaysia, it is often called ikan (fish) kelah. Sen and Jayaram restrict the term mahseer to members of the genus Tor.

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What is the average size of a ripe female fish?

The minimal length and weight at first maturity of female fishes were 17.8 cm and 70 g respectively whereas males attained maturity at an average length of 17.3 cm and weight of 50 g. The Gonado-somatic Index in ripe female was 16.19 and the average fecundity factor was 70.18. The fish was bred successfully in captive condition through stripping.

What is an example of a hermaphrodite fish?

Another example is the dragonet, in which males are considerably larger than females and possess longer fins. Sexual dimorphism also occurs in hermaphroditic fish. These species are known as sequential hermaphrodites.

What is meant by gender dimorphism?

Ans. Gender dimorphism can be generally measured as a ratio of male to female body mass, which can also be termed as sexual body size dimorphism. The male of most hominoids is larger than the female.

How does the male phenotype affect sexual dimorphism?

The male phenotype sends signals to females who then choose the ‘fittest’ available male. Sexual dimorphism is a product of both genetics and environmental factors. An example of sexual polymorphism determined by environmental conditions exists in the red-backed fairywren.

Does natural selection explain sexually dimorphic traits?

While the causal role of sexual selection in driving sexual dimorphism is undisputed with abundant examples (Fairbairn et al., 2007; Székely et al., 2000 ), natural selection is less often evoked to explain sexually dimorphic traits.

Does sexual dimorphism evolve at equilibrium?

Our unidimensional world allows us to conveniently adjust how much the resource types are different from each other (e.g. in size), and we find that sexual dimorphism is more likely to evolve and reach a high magnitude at equilibrium, when the distributions of different resource types become more different from each other (Figure 3a ).

What are the sex determination mechanisms across various classes of organisms?

Sex determination mechanisms across various classes of organisms. XO, XY, ZO and ZW indicate chromosomal sex determination. GSD stands for genetic sex determination. ESD is environmental sex determination.

Which fish species are involved in the process of sex differentiation?

Guiguen Y., Baroiller J.F., Ricordel M.J., Iseki K., McMeel O., Martin S.A.M., Fostier A. Involvement of estrogens in the process of sex differentiation in two fish species: The rainbow trout (Oncorhynchus mykiss) and a tilapia (Oreochromis niloticus) Mol. Reprod. Dev. Inc.

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What is the difference between dimorphism and monomorphism?

Sexual dimorphism meaning tells that these distinctions can be subtle or extreme, and they can be influenced by sexual and natural selection. Monomorphism is the exact opposite of dimorphism. The word dimorphic meaning in sexual dimorphism stands for occurring in two distinct forms or describing two distinct forms.

Why do lizards have sexual dimorphism?

Although sexual selection for large size in males as a means of obtaining large territories and the females they contain is commonly invoked as an explanation for lizard sexual dimorphism (reviewed in ref. 13 ), it is difficult to attribute the patterns observed here to that cause.

How do sympatric congeners affect sexual size dimorphism in Anolis?

Previous work 22 indicates that the degree of sexual size dimorphism in Anolis decreases with the number of sympatric congeners.

Are anoles sexually dimorphic?

In addition, anoles vary considerably in the extent of sexual dimorphism in body size 8, 13, 14, ranging from species in which the sexes are the same size to others in which adult males are more than three times the mass of adult females, and in ecomorphologically relevant body proportions 9, 15.

What causes sexual dimorphism in animals?

Sexual dimorphism is the physiological and anatomical differences between males and females of a species. Sexual dimorphism is common across the animal kingdom and may be caused by three main reasons. First, sexual selection may cause mates with brighter colors or larger horns to be selected, which may otherwise be maladaptive.

What causes sexual dimorphism in elephant seals?

In elephant seals, sexual dimorphism is linked to a male’s ability to protect territories and dominate large numbers of females, that is linked to polygynic activity. The broad sexual size disparity is due in part to sexual selection, it is however related to the fact that females enter reproductive age far sooner than males.

When did mahseer first appear in India?

Many of the most detailed descriptions of mahseer begin to appear during the British colonisation of India, in particular, during the British Raj of 1857 to 1947. Many of those stationed in India enjoyed angling for mahseer, which they compared to the thrill of catching a salmon ‘back home’.