Spawn is the eggs and sperm released or deposited into water by aquatic animals . As a verb, to spawn refers to the process of freely releasing eggs and sperm into a body of water (fresh or marine); the physical act is known as spawning . The vast majority of aquatic and amphibious animals reproduce through spawning. These include the following groups:
73-402: Maurolicinae Sternoptychinae (but see text ) The marine hatchetfishes or deep-sea hatchetfishes as well as the related bottlelights , pearlsides and constellationfishes are small deep-sea ray-finned fish of the stomiiform family Sternoptychidae . They are not closely related to and should not be confused with the freshwater hatchetfishes , which are teleosts in
146-464: A breeding site. The females choose large males that are successfully defending prime breeding sites which the females find attractive. For example, sculpin males defend "caves" underneath rocks which are suitable for the incubation of embryos. Another way males get to mate with several females is through the use of leks. Leks are places where many fish come together, and the males display to each other. Based on these displays, each female then selects
219-480: A classification of the spawning behaviours of fish by Balon (1975, 1984) into reproductive guilds . This classification is based on how the eggs are fertilized (internal or external spawners), where the eggs are deposited ( pelagic or benthic spawners), and whether and how the parents look after the eggs after spawning (bearers, guarders and nonguarders). Nonguarders do not protect their eggs and offspring after spawning Open substrate spawners scatter their eggs in
292-406: A drop of nutrient oil to sustain the embryo as it develops inside the egg case. The oil also provides buoyancy, so the eggs float and drift with the current. 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
365-772: A few days and replace the dominant male. This is found amongst coral reef fishes such as groupers , parrotfishes and wrasses . It is less common for a male to switch to a female ( protandry ). As an example, most wrasses are protogynous hermaphrodites within a haremic mating system. Hermaphroditism allows for complex mating systems. Wrasses exhibit three different mating systems: polygynous, lek-like , and promiscuous mating systems. Group spawning and pair spawning occur within mating systems. The type of spawning that occurs depends on male body size. Labroids typically exhibit broadcast spawning, releasing high amounts of planktonic eggs, which are broadcast by tidal currents; adult wrasses have no interaction with offspring. Wrasse of
438-825: A forage fish of the smelt family found in the Atlantic and Arctic oceans. In summer, they graze on dense swarms of plankton at the edge of the ice shelf. Larger capelin also eat krill and other crustaceans . 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 . The migration is affected by ocean currents . Around Iceland maturing capelin make large northward feeding migrations in spring and summer. The return migration takes place in September to November. The spawning migration starts north of Iceland in December or January. The diagram on
511-496: A general rule, aquatic or semiaquatic reptiles , birds , and mammals do not reproduce through spawning, but rather through copulation like their terrestrial counterparts. This is also true of cartilaginous fishes (such as sharks , rays and skates ). Spawn consists of the reproductive cells ( gametes ) of many aquatic animals, some of which will become fertilized and produce offspring. The process of spawning typically involves females releasing ova (unfertilized eggs) into
584-400: A pair of gonads , which release sperm in response to hormones in the female's bloodstream indicating egg release. This ensures that, when the female is ready to spawn, she has a mate immediately available. A single anglerfish female can "mate" with many males in this manner. Polygynandry occurs when multiple males mate indiscriminately with multiple females. This mutual promiscuity is
657-503: A particular subgroup of the family Labridae , Labrini, do not exhibit broadcast spawning. Less commonly hermaphrodites can be synchronous , meaning they simultaneously possess both ovaries and testicles and can function as either sex at any one time. Black hamlets "take turns releasing sperm and eggs during spawning. Because such egg trading is advantageous to both individuals, hamlets are typically monogamous for short periods of time–an unusual situation in fishes." The sex of many fishes
730-457: A peculiar body shape and like their relatives have bioluminescent photophores . The latter allow them to use counter-illumination to escape predators that lurk in the depths: by matching the light intensity with the light penetrating the water from above, the fish does not appear darker if seen from below. They typically occur at a few hundred meters below the surface, but their entire depth range spans from 50 to 1,500 meters deep. The body
803-488: A relatively small number of embryos and retain them for a few weeks to 16 months or longer. The shorter times spans are characteristic of species that eventually deposit their embryos in the environment, surrounded by a horny capsule; whereas the longer periods are characteristic of sharks that retain the embryos until they are ready to emerge as actively swimming young." However, some fish do not fit these categories. The livebearing largespring gambusia ( Gambusia geiseri )
SECTION 10
#1733106998313876-563: A short lifespan are presumably semelparous The fry – even of Sternoptychinae – look like tiny pearlsides ( Maurolicus ). Marine hatchetfishes are not the only animals that seek out prey by watching for silhouettes from below. Indeed, many fishes that consider Sternoptychidae prey do so, and to foil their predaceous attempts, the Sternoptychidae have evolved an astounding ability: bioluminescent counter-illumination . Counterillumination (or counter-lighting) involves
949-400: A significant temperature change, often in spring. Males chase females, prompting them to release their eggs by bumping and nudging them. As the female goldfish spawns her eggs, the male goldfish stays close behind fertilizing them. Their eggs are adhesive and attach to aquatic vegetation. The eggs hatch within 48 to 72 hours. Within a week or so, the fry begins to assume its final shape, although
1022-600: A species is all-male or all-female. Unisexuality occurs in some fish species, and can take complex forms. Squalius alburnoides , a minnow found in several river basins in Portugal and Spain, appears to be an all-male species. The existence of this species illustrates the potential complexity of mating systems in fish. The species originated as a hybrid between two species, and is diploid , but not hermaphroditic. It can have triploid and tetraploid forms, including all-female forms that reproduce mainly through hybridogenesis . It
1095-423: A species is either male or female, and remains that way throughout their lives. Most fish are gonochorists, but hermaphroditism is known to occur in 14 families of teleost fishes. Usually hermaphrodites are sequential , meaning they can switch sex, usually from female to male ( protogyny ). This can happen if a dominant male is removed from a group of females. The largest female in the harem can switch sex over
1168-438: A substrate and guard them until the eggs hatch. After hatching, the female picks up the fry and keeps them in her mouth. When the fry can fend for themselves, they are released. Some eartheaters are larvophile mouthbrooders. The beginning of the evolutionary process of livebearing starts with facultative (optional) internal bearing. The process occurs in several species of oviparous (egg-laying) killifishes which spawn in
1241-437: A year may pass before they develop a mature goldfish colour; until then they are a metallic brown like their wild ancestors. In their first weeks of life, the fry grow quickly—an adaptation born of the high risk of getting devoured by the adult goldfish. Carp typically spawn in the spring and summer, depending on the climate and conditions. Oxygen levels of the water, availability of food, size of each fish, age, number of times
1314-444: Is an "investment by parents in offspring that increases the offspring's chances of surviving (and hence reproducing). In fish, parental care can take a variety of forms including guarding, nest building, fanning, splashing, removal of dead eggs, retrieval of straying fry, external egg carrying, egg burying, moving eggs or young, ectodermal feeding, oral brooding, internal gestation, brood-pouch egg carrying, etc." Territorial behaviour
1387-615: Is called coral because it turns bright red when cooked. Roe (reproductive organs) are usually eaten either raw or briefly cooked. "The reproductive behaviour of fishes is remarkably diversified: they may be oviparous (lay eggs), ovoviviparous (retain the eggs in the body until they hatch), or viviparous (have a direct tissue connection with the developing embryos and give birth to live young). 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. The most characteristic features of
1460-543: Is correct. It may even be that the Maurolicinae are just an indiscriminate assemblage of unrelated basal Sternoptychidae and are altogether invalid. The Sternoptychinae – the "true" marine hatchetfishes – on the other hand are monophyletic . The provisional arrangement of subfamilies and genera of Sternoptychidae is as follows: Sternoptychinae Marine hatchetfishes or deep-sea hatchetfishes are small deep-sea mesopelagic ray-finned fish of
1533-509: Is deep and laterally extremely compressed, somewhat resembling a hatchet (with the thorax being the "blade" and the caudal peduncle being the "handle"). The genus Polyipnus is rounded, the other two – in particular Sternoptyx – decidedly angular if seen from the side. Their pelvis is rotated to a vertical position. The mouth is located at the tip of the snout and directed almost straight downwards. Their scales are silvery, delicate and easily abraded. In some species, such as
SECTION 20
#17331069983131606-408: Is difficult for fish to find partners, or when both sexes look after the young. Many tropical cichlids , which rear their young together in locations where they must fiercely defend against competitors and predators are monogamous. "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. While
1679-610: Is dominated by large and aggressive males. Cuckoldry is a variant of polyandry, and can occur with sneak spawners (sometimes called streak spawners ). A sneak spawner is a male that rushes in to join the spawning rush of a spawning pair. A spawning rush occurs when a fish makes a burst of speed, usually on a near vertical incline, releasing gametes at the apex, followed by a rapid return to the lake or sea floor or fish aggregation. Sneaking males do not take part in courtship. In salmon and trout, for example, jack males are common. These are small silvery males that migrate upstream along with
1752-489: Is generally necessary for guarders, and the embryos are almost always guarded by males (apart from cichlids). There is a need to be territorial because looking after embryos usually includes defending the site where they are being looked after. It also often means there is competition for the best egg-laying sites. Elaborate courtship behaviour is usual among guarders. Guarding males keep the embryos safe from predators, keep oxygen levels high by fanning water currents, and keep
1825-450: Is not fixed, but can change with physical and social changes to the environment where the fish lives. Particularly among fishes, hermaphroditism can pay off in situations where one sex is more likely to survive and reproduce, perhaps because it is larger. Anemone fishes are sequential hermaphrodites which are born as males, and become females only when they are mature. Anemone fishes live together monogamously in an anemone , protected by
1898-517: Is often associated with r-strategists . However, most fish and other spawning animals are iteroparous. When the internal ovaries or egg masses of fish and certain marine animals are ripe for spawning they are called roe . Roe from certain species, such as shrimp , scallop , crab and sea urchins , are sought as human delicacies in many parts of the world. Caviar is a name for the processed, salted roe of non-fertilized sturgeon . The term soft roe or white roe denotes fish milt . Lobster roe
1971-494: Is often necessary to construct fish ladders and other bypass systems so salmon can navigate their way past hydroelectric dams or other obstructions such as weirs on their way to spawning grounds. Coastal fish often use mangroves and estuaries as spawning grounds, while reef fish can find adjacent seagrass meadows that make good spawning grounds. Short-finned eels can travel anything up to three or four thousand kilometres to their spawning ground in deep water somewhere in
2044-501: Is rare to find true parthenogenesis in fishes, where females produce female offspring with no input from males. All-female species include the Texas silverside , Menidia clarkhubbsi as well as the Amazon molly . Parthenogenesis has been recently observed in hammerhead sharks and blacktip sharks . It is also known to occur in crayfish and amphibians. This section is patterned after
2117-497: Is the closest living relative of the Sternoptychidae, and these two form the suborder Gonostomatoidei . Indeed, some Sternoptychidae are called "bristlemouths", like the bulk of the Gonostomatidae. Compared to their relatives, the marine hatchetfishes are a more apomorphic group, but they have evolved in an entirely different direction from the other "advanced" lineage of Stomiiformes, the huge family Stomiidae . Typically,
2190-497: Is the egg yolk, as in externally spawned eggs. This situation, also referred to as ovoviviparity , is characteristic of marine rock fishes and the Lake Baikal sculpins . This strategy allows these fish to have fecundities approaching those of pelagic fish with external fertilization, but it also enables them to protect the young during their most vulnerable stage of development. By contrast, sharks and rays using this strategy produce
2263-608: The Coral Sea . Forage fish often make great migrations between their spawning, feeding and nursery grounds. Schools of a particular stock usually travel in a triangle between these grounds. For example, one stock of herrings have their spawning ground in southern Norway , their feeding ground in Iceland , and their nursery ground in northern Norway. Wide triangular journeys such as these may be important because forage fish, when feeding, cannot distinguish their own offspring. Capelin are
Sternoptychidae - Misplaced Pages Continue
2336-478: The Highlight Hatchetfish ( Sternoptyx pseudobscura ), large sections of the body at the base of the anal fin and/or caudal fin are transparent. The anal fin has 11–38 rays and may be divided in two parts. An adipose fin is usually present. The Sternoptychinae have preopercular spines and blade-like pterygiophores in front of the dorsal fin . Their large, sometimes tube-shaped eyes can collect
2409-570: The bluegill sunfish in fresh water. Sneaker males that become too large to hide effectively become satellite males . With bluegill sunfish, satellite males mimic the behaviour and colouration of the females. They hover over a nest containing a pair of courting sunfish, and gradually descend to reach the pair just as they spawn. Males may need to be 6 or 7 years old to function capably as parental males, but may be able to function as sneaker or satellite males when they are as young as 2 or 3 years old. The smaller satellite and sneaker males may get mauled by
2482-399: The characiform family Gasteropelecidae. The Sternoptychidae have 10 genera and about 70 species altogether. The scientific name means " Sternoptyx -family", from Sternoptyx (the type genus ) + the standard animal family suffix "-idae". The type genus derives from Ancient Greek stérnon (στέρνον, "breast") + ptýx (πτύξ, "a fold/crease") + Latin forma ("external form"),
2555-412: The highlight hatchetfish ( Sternoptyx pseudobscura ), large sections of the body at the base of the anal fin and/or caudal fin are transparent. They have perpendicular spines and blade-like pterygiophores in front of the dorsal fin . The anal fin has 11–19 rays and in some species is divided in two parts; almost all have an adipose fin . Their large, sometimes tube-shaped eyes can collect
2628-650: The sardine run occurs when millions of sardines migrate from their spawning grounds south of the southern tip of Africa northward along the Eastern Cape coastline. Chinook salmon make the longest freshwater migration of any salmon, over 3,000 kilometres (1,900 mi) up the Yukon River to spawning grounds upstream of Whitehorse , Yukon. Some green sea turtles swim more than 2,600 kilometres (1,600 mi) to reach their spawning grounds. Goldfish , like all cyprinids , are egg-layers. They usually start breeding after
2701-501: The stomiiform subfamily Sternoptychinae . They should not be confused with the freshwater hatchetfishes , which are not particularly closely related Teleostei in the characiform family Gasteropelecidae. The scientific name means " Sternoptyx -subfamily", from Sternoptyx (the type genus ) + the standard animal family suffix "-inae". It ultimately derives from Ancient Greek stérnon (στέρνον, "breast") + ptýx (πτύξ, "a fold/crease") + Latin forma ("external form"),
2774-471: The "Stenopterygii" are found among the superorder Protacanthopterygii , and that the former would need to be merged in the latter. In some classifications, the "Stenopterygii" are kept separate but included with the Protacanthopterygii and the monotypic superorder Cyclosquamata in an unranked clade called Euteleostei. That would probably require splitting two additional monotypic superorders out of
2847-461: The Greek part in reference to the thorax shape of marine hatchetfishes. Found in tropical , subtropical and temperate waters of the Atlantic , Pacific and Indian Oceans , marine hatchetfishes range in size from Polyipnus danae at 2.8 cm (1.1 in) to the c.12 cm (4.7 in)-long giant hatchetfish ( Argyropelecus gigas ). They are small deep-sea fishes which have evolved
2920-413: The Greek part in reference to the thorax shape of marine hatchetfishes. Found most often at depths of 200–600 meters in tropical , subtropical and temperate waters of the Atlantic , Pacific and Indian Oceans , marine hatchetfishes range in size from Polyipnus danae at 2.8 cm (1.1 in) to the c.12 cm (4.7 in)-long giant hatchetfish ( Argyropelecus gigas ). The members of
2993-558: The Protacanthopterygii, and thus result in a profusion of very small taxa . The Stomiiformes have also been considered close relatives of the Aulopiformes . The latter are otherwise placed in a monotypic superorder "Cyclosquamata" but also appear to be quite close to the Protacanthopterygii indeed. The relationships of these – and the Lampriformes or Myctophiformes , which are also usually treated as monotypic superorders – to
Sternoptychidae - Misplaced Pages Continue
3066-457: The Sternoptychidae are divided into two subfamilies , with the more plesiomorphic members making up the Maurolicinae . Symplesiomorphies are no reliable indicator of actual relationships, however. While it remains to be seen what Sternoptychidae other than the pearlsides ( Maurolicus , the type genus ) do actually belong in the Maurolicinae, it is unlikely that the two-subfamily arrangement
3139-472: The anemone stings. The males do not have to compete with other males, and female anemone fish are typically larger. 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". In other fishes sex changes are reversible. For example, if some gobies are grouped by sex (male or female), some will switch sex. Unisexuality occurs when
3212-420: The approach most commonly used by spawning animals, and is perhaps the "original fish mating system." Common examples are forage fish , such as herrings , which form huge mating shoals in shallow water. The water becomes milky with sperm and the bottom is draped with millions of fertilized eggs. Alternate male strategies which allow small males to engage in cuckoldry can develop in species where spawning
3285-448: The area free from dead embryos and debris. They protect the embryos until they hatch, and often look after the larval stages as well. The time spent guarding can range from a few days to several months. Some guarders build nests ( nest spawners ) and some do not ( substrate spawners ), though the difference between the two groups can be small. Substrate spawners clean off a suitable area of surface suitable for egg laying, and look after
3358-432: The area, but they do not actively build a nest. Bearers are fish that carry their embryos (and sometimes their young) around with them, either externally or internally. Mouth brooders - carry eggs or larvae in their mouth. Mouth brooders can be ovophiles or larvophiles. Ovophile or egg-loving mouth-brooders lay their eggs in a pit, which are sucked up into the mouth of the female. The small number of large eggs hatch in
3431-477: The brooding but cannot handle all the eggs the female produce, such as with some pipefish . The males in some deep sea anglerfishes are much smaller than the females. When they find a female they bite into her skin, releasing an enzyme that digests the skin of their mouth and her body and fusing the pair down to the blood-vessel level. The male then slowly atrophies , losing first his digestive organs, then his brain, heart, and eyes, ending as nothing more than
3504-515: The disputed subfamily Maurolicinae have a more conventional fish shape. The mouth is located at the tip of the snout and directed downwards, more so in the Sternoptychinae. Unlike other Stomiiformes , they still have fully developed pseudobranchs . Their branchiostegal rays are 6–10, three of them attach to the posterior ceratohyal ( epihyal ). Their bodies are covered in delicate silvery scales which abrade easily. In some species, such as
3577-450: The egg capsule into miniature versions of their parents. To survive, they must then become miniature predators themselves, feeding on plankton. Fish eventually encounter others of their own kind ( conspecifics ), where they form aggregations and learn to school. Internally, the sexes of most marine animals can be determined by looking at the gonads . For example, male testes of spawning fish are smooth and white and account for up to 12% of
3650-507: The environment. They usually spawn in shoals without complex courtship rituals, and males outnumber females. Broadcast spawners : release their gametes (sperm and eggs) into open water for external fertilisation. There is no subsequent parental care. About 75% of coral species are broadcasters, the majority of which are hermatypic, or reef-building corals. Brood hiders hide their eggs but do not give parental care after they have hidden them. Brood hiders are mostly benthic spawners that bury
3723-472: The eyes from above. The patterns of light created by the photophores are also unique to each species , probably playing a role in courtship. The Sternoptychidae belong to the order Stomiiformes , which is often placed in the teleost superorder Stenopterygii , usually together with the Ateleopodiformes (jellynoses), but sometimes on their own. But it may well be that the closest living relatives of
SECTION 50
#17331069983133796-414: The faintest of light and focus well on objects both close and far. In many genera , the eyes are fixed gazing permanently upwards, enabling them to discern the silhouettes of prey moving overhead against the slightly brighter upper waters. Sternoptychidae undertake nightly mass migrations from depths of 3,600 metres to the upper 50–100 metres of the starlit water column . There they feed throughout
3869-423: The faintest of light and focus well on objects both close and far. They are directed somewhat upwards, most conspicuously in the genus Argyropelecus . This allows them to discern the silhouettes of prey moving overhead against the slightly brighter upper waters. There are three genera in this subfamily , with some 40 species altogether: Four fossil genera are also known: Spawn (biology) As
3942-532: The fertilized eggs. For example, among salmon and trout the female digs a nest with her tail in gravel. These nests are called redds . The female then lays her eggs while the male fertilizes them, while both fish defend the redd if necessary from other members of the same species. Then the female buries the nest, and the nest site is abandoned. In North America, some minnows build nests out of piles of stones rather than dig holes. The minnow males have tubercles on their head and body which they use to help them defend
4015-415: The host. The same female may use a number of mussels, and she deposits only one or two yellow, oval eggs into each. Early developmental stages are protected from predation within the body of the mussel. After 3 to 4 weeks larvae swim away from the host to continue life on their own. Guarders protect their eggs and offspring after spawning by practicing parental care (also called brood care ). Parental care
4088-470: The male is pregnant, the female starts a new batch of eggs, which are ready at about the same time that the male gives birth to the young from the previous mating. This close timing of development promotes monogamy, especially if the likelihood of encountering another potential mate is low." Polygyny occurs when one male gets exclusive mating rights with multiple females. In polygyny, a large conspicuous male usually defends females from other males or defends
4161-527: The male they want to be their mate. 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. The females, which are mouth brooders, choose which male they want to fertilize their eggs. Polyandry occurs when one female gets exclusive mating rights with multiple males. This happens among fish like clownfish that change their sex. It can also happen when males do
4234-494: The males often have penis-like intromittent organs in the form of a modified fin. A species is semelparous if its individuals spawn only once in their lifetime, and iteroparous if its individuals spawn more than once. The term semelparity comes from the Latin semel , once, and pario , to beget, while iteroparity comes from itero , to repeat, and pario , to beget. Semelparity is sometimes called "big bang" reproduction, since
4307-661: The mass of the fish, while female ovaries are granular and orange or yellow, accounting for up to 70% of the fish's mass. Male lampreys, hagfish and salmon discharge their sperm into the body cavity where it is expelled through pores in the abdomen. Male sharks and rays can pass sperm along a duct into a seminal vesicle , where they store it for a while before it is expelled, while teleosts usually employ separate sperm ducts. Externally, many marine animals, even when spawning, show little sexual dimorphism (difference in body shape or size) or little difference in colouration . Where species are dimorphic, such as sharks or guppies ,
4380-437: The more powerful parental males, but they spawn when they are younger and they do not put energy into parental care. Hermaphroditism occurs when a given individual in a species possesses both male and female reproductive organs, or can alternate between possessing first one, and then the other. Hermaphroditism is common in invertebrates but rare in vertebrates. It can be contrasted with gonochorism , where each individual in
4453-581: The more primitive bony fishes is the assemblage of polyandrous (many males) breeding aggregations in open water and the absence of parental care..." There are two main reproduction methods in fish. The first method is by laying eggs and the second by live-bearing (producing their young alive). Monogamy occurs when one male mates with one female exclusively. This is also called pair spawning . Most fish are not monogamous, and when they are, they often alternate with non-monogamous behaviours. Monogamy can occur when feeding and breeding grounds are small, when it
SECTION 60
#17331069983134526-434: The mother's mouth, and the fry remain there for a period of time. Fertilization often occurs with the help of egg-spots, which are colorful spots on the anal fin of the male. When the female sees these spots, she tries to pick up the egg-spots, but instead gets sperm that fertilizes the eggs in her mouth. Many cichlids and some labyrinth fish are ovophile mouthbrooders. Larvophile or larvae-loving mouth-brooders lay their eggs on
4599-399: The nest site. Bitterlings have a remarkable reproduction strategy where parents transfer responsibility for the care of their young to mussels . The female extends her ovipositor into the mantle cavity of the mussel and deposits her eggs between the gill filaments. The male then ejects his sperm into the mussel's inhalant water current and fertilization takes place within the gills of
4672-468: The night, returning to the depths by daybreak. Their prey consists primarily of tiny crustaceans , such as amphipods , copepods , euphausiids (krill) and ostracods (seed shrimp), and of fish smaller than themselves. What little is known of their life cycle suggests that at least some members of this family are short-lived, dying after no more than a year. They spawn in the open water, and do not guard or otherwise care for their offspring; species with
4745-415: The normal way on the substrate, but in the process accidentally fertilize eggs that the female retains and does not spawn. These eggs are spawned later, usually without allowing much time for embryonic development. The next step in the evolution of livebearing is obligate (by necessity) internal bearing, where the female retains all the embryos. "The only source of nutrition for these embryos, however,
4818-456: The production of light by the fish for the purpose of camouflaging its silhouette from observers lurking below. Sternoptychidae produce this light with organs called photophores , of which they have between 3 and 7 – usually 6 – on the branchiostegal membrane along the lower edge of the chest and belly. The intensity of the light produced is controlled by the fish, an appropriate brightness chosen according to how much light reaches
4891-458: The right shows the main spawning grounds and larval drift routes. Capelin on the way to feeding grounds is coloured green, capelin on the way back is blue, and the breeding grounds are red. In a paper published in 2009, researchers from Iceland recount their application of an interacting particle model to the capelin stock around Iceland, successfully predicting the spawning migration route for 2008. Referred to as "the greatest shoal on earth",
4964-477: The single reproductive event of semelparous organisms is usually large and fatal to the spawners. 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. Other spawning animals which are semelparous include mayflies , squid , octopus , smelt , capelin and some amphibians. Semelparity
5037-415: The spawn is released and whether or how the spawn is subsequently guarded. Marine animals, and particularly bony fish , commonly reproduce by broadcast spawning . This is an external method of reproduction where the female releases many unfertilised eggs into the water. At the same time, a male or many males release a large amount of sperm into the water which fertilises some of these eggs. The eggs contain
5110-427: The standard, large, hook-nosed males and that spawn by sneaking into a redd (spawning nest) to release sperm simultaneously with a mated pair. This behaviour is an evolutionarily stable strategy for reproduction, because it is favoured by natural selection just like the "standard" strategy of large males. Cuckoldry occurs in many fish species, including dragonets , parrotfishes and wrasses on tropical reefs and
5183-518: The taxa mentioned before is still not well resolved at all, and regardless whether one calls them Protacanthopterygii sensu lato or Euteleostei, the phylogeny of this group of moderately advanced Teleostei is in need of further study. The ancestral Stomiiformes probably resembled the Gonostomatidae , with thin brownish bodies, rows of egg-shaped photophores adorning the lower body parts, and mouths with numerous teeth. The family Gonostomatidae
5256-428: The water, often in large quantities, while males simultaneously or sequentially release spermatozoa ( milt ) to fertilize the eggs. The fungi ( mushrooms ), are also said to "spawn" when they release a white, ‘fibrous’ matter, forming the matrix from-which they grow. There are many variations in the way spawning occurs, depending on sexual differences in anatomy, how the sexes relate to each other, where and how
5329-548: Was thought to be ovoviviparous until it was shown in 2001 that the embryos received nutrients from the mother. Spawning grounds are the areas of water where aquatic animals spawn, or produce their eggs. After spawning, the spawn may or may not drift to new grounds which become their nursery grounds. Many species undertake migrations each year, and sometimes great migrations, to reach their spawning grounds. For example, lakes and river watersheds can be major spawning grounds for anadromous fish such as salmon . These days, it
#312687