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Most fish species spawn eggs that are fertilized externally, typically with the male inseminating the eggs after the female lays them. These eggs do not have a shell and would dry out in the air. Even air-breathing amphibians lay their eggs in water, or in protective foam as with the Coast foam-nest treefrog, Chiromantis xerampelina.
Parthenogenesis (/ ˌ p ɑːr θ ɪ n oʊ ˈ dʒ ɛ n ɪ s ɪ s,-θ ɪ n ə-/; [1] [2] from the Greek παρθένος, parthénos, 'virgin' + γένεσις, génesis, 'creation' [3]) is a natural form of asexual reproduction in which the embryo develops directly from an egg without need for fertilization.
Some fish have evolved to exploit the mouthbrooding behaviour of other species. Synodontis multipunctatus, also known as the cuckoo catfish, combines mouthbrooding with the behavior of a brood parasite: it eats the host mouthbrooder's eggs, while spawning and simultaneously laying and fertilizing its own eggs. The mouthbrooder (typically a ...
One study considered the ways in which male Siamese fighting fish alter their behaviours during courtship when another male is present. During this experiment, a dummy female was placed in the tank. The researchers expected that males would conceal their courtship from intruders; instead, when another male fish was present, the male was more ...
Within iteroparous fish, they usually give no parental care with external fertilization. [22] The sperm present in male fish are immotile while in testes and in seminal fluid, and the fertilization environment determines when the sperm become motile. In salmon, a decrease of potassium in fresh water will initiate the motility of the sperm.
The best known Betta species is B. splendens, commonly known as the Siamese fighting fish and often kept as an aquarium pet. Characteristics All Betta species are small fishes, but they vary considerably in size, ranging from under 2.5 cm (1 in) total length in B. chanoides to 14 cm (5.5 in) in the Akar betta ( B. akarensis ).
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The paternal chromosomes are therefore excluded from nascent eggs, without recombination having typically occurred. [8] In some cases, such as Pelophylax esculentus , there is also endomeiosis prior to cell division, which means that the maternal chromosomes are duplicated and each egg contains identical pairs of chromosomes. [ 8 ]