These include the following groups: As a general rule, aquatic or semiaquatic reptiles, birds, and mammals do not reproduce through spawning, but rather through copulation like their terrestrial counterparts.
The strategy for survival of broadcast spawning is to disperse the fertilised eggs, preferably away from the coast into the relative safety of the open ocean.
There the larvae develop as they consume their fat stores, and eventually hatch from the egg capsule into miniature versions of their parents.
[5] The classic example of a semelparous animal is the Pacific salmon, which lives for many years in the ocean before swimming to the freshwater stream of its birth, spawning, and then dying.
Roe from certain species, such as shrimp, scallop, crab and sea urchins, are sought as human delicacies in many parts of the world.
All cartilaginous fishes—the elasmobranches (e.g., sharks, rays, and skates)—employ internal fertilization and usually lay large, heavy-shelled eggs or give birth to live young.
Monogamy can occur when feeding and breeding grounds are small, when it is difficult for fish to find partners, or when both sexes look after the young.
[10] "In some pipefishes and seahorses, development of eggs takes a long time before the female can place them in the brood pouch of a male, where they are fertilized.
For example, among the cichlid Cyrtocara eucinostomus in Lake Malawi, up to 50,000 large and colourful males display together on a lek four kilometres long.
[15] Cuckoldry occurs in many fish species, including dragonets, parrotfishes and wrasses on tropical reefs and the bluegill sunfish in fresh water.
The male then ejects his sperm into the mussel's inhalant water current and fertilization takes place within the gills of the host.
By contrast, sharks and rays using this strategy produce a relatively small number of embryos and retain them for a few weeks to 16 months or longer.
The capelin move inshore in large schools to spawn and migrate in spring and summer to feed in plankton rich areas between Iceland, Greenland, and Jan Mayen.
Within a week or so, the fry begins to assume its final shape, although a year may pass before they develop a mature goldfish colour; until then they are a metallic brown like their wild ancestors.
[45] Prior to spawning, male Siamese fighting fish build bubble nests of varying sizes at the surface of the water.
Incubation lasts for 24–36 hours, and the newly hatched larvae remain in the nest for the next 2–3 days, until their yolk sacs are fully absorbed.
[54] Egg-bearing female lobsters migrate inshore from deeper waters to hatch their eggs, though they do not have specific spawning grounds.
This species is very fecund, with females releasing about 50–200 million eggs in regular intervals (at a rate of 5–10 times a minute) in a single spawning.
[59] Cephalopods, such as squid and octopuses, have prominent heads and a set of arms (tentacles) modified from the primitive foot of molluscs.
[61] The "penis" in most male cephalopods is a long and muscular end of the gonoduct used to transfer spermatophores to a modified sperm-carrying arm called a hectocotylus.
In species where the hectocotylus is missing, the "penis" is long and able to extend beyond the mantle cavity and transfers the spermatophores directly to the female.
[62][63] Some species brood their fertilized eggs: female paper nautilus construct shelters for the young, while Gonatiid squid carry a larva-laden membrane from the hooks on their arms.
The gonads are lined with muscles underneath the peritoneum, and these allow the animal to squeeze its gametes through the duct and into the surrounding sea water, where fertilization takes place.
[68] Their roe (male and female gonads) is soft and melting, with a colour ranging from orange to pale yellow, and is sought after as a human delicacy in many parts of the world.
The eggs of some species laid out of water can detect vibrations of nearby predatory wasps or snakes, and will hatch early to avoid being eaten.
The hatched eggs continue life as tadpoles, which typically have oval bodies and long, vertically flattened tails.
Some species which go through the metamorphosis inside the egg and hatch to small frogs never develop gills; instead there are specialised areas of skin that take care of respiration.
Unlike frogs, sea turtle eggs have tough, leathery shells which allow them to survive on land without drying out.
[77] After mating in the water, the female moves above the beach's high tide line where she digs a hole with her hind flippers and deposits her eggs.
The gametes fuse during fertilization to form a microscopic larva called a planula, typically pink and elliptical in shape.
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