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They have no intermediate hosts and are ectoparasitic on fish (seldom in the urinary bladder and rectum of cold-blooded vertebrates). Although they are hermaphrodites, the male reproductive system becomes functional before the female part. The eggs hatch releasing a heavily ciliated larval stage known as an oncomiracidium. The oncomiracidium ...
The ZW sex-determination system is a chromosomal system that determines the sex of offspring in birds, some fish and crustaceans such as the giant river prawn, some insects (including butterflies and moths), the schistosome family of flatworms, and some reptiles, e.g. majority of snakes, lacertid lizards and monitors, including Komodo dragons.
A certain type of fish that is a mouthbrooder is called cichlids and many of them are maternal mouthbrooders. The process for this is the female would lay the egg and pick it up in her mouth. Then the males will encourage the female to open her mouth so they can fertilize the eggs while it is in the female's mouth. [27]
When a female dies a juvenile (male) anemone fish moves in, and "the resident male then turns into a female and reproductive advantages of the large female–small male combination continue". [22] In other fishes sex changes are reversible. For example, if some gobies are grouped by sex (male or female), some will switch sex. [14]: 164 [21]
The female blue-footed booby lays two or three eggs, about four to five days apart. Both male and female take turns incubating the eggs, while the nonsitting bird keeps watch. Since the blue-footed booby does not have a brooding patch, it uses its feet to keep the eggs warm. The incubation period is 41–45 days. Usually, one or two chicks are ...
The most common reproductive strategy for fish is known as oviparity, in which the female lays undeveloped eggs that are externally fertilized by a male. Typically large numbers of eggs are laid at one time (an adult female cod can produce 4–6 million eggs in one spawning) and the eggs are then left to develop without parental care.
Oviparity: internal fertilisation, where the female lays zygotes as eggs with important vitellus (typically birds) Ovoviviparity can be thought of as a form of oviparity where the zygotes are retained in the female's body or in the male's body, but there are no trophic interactions between zygote and parents. This is found in Anguis fragilis.
The cuttlebone of a cuttlefish. This is the largest hard part of a cuttlefish, maintaining the rigidity of its body.. The common cuttlefish is one of the largest species of cuttlefish with a mantle length reaching up to 45 cm and a mass of 4 kg on a presumed male, although this is for an exceptional specimen in temperate waters; specimens in subtropical waters rarely surpass a mantle length of ...