Breeding in the Wild
Breeding in the Wild
Written by Friday, 23 March 2001 01:00
Fishes have developed many ways of mating and spawning that characterize them in some way. There are two different techniques of breeding, with which we separate fishes in two great groups, the livebearers and the egg layers. Live bearing is a more primitive behavior than egg laying.
The livebearers give birth to formed fishes as fertilization takes place inside the bodies of the parents as their ancestors did. Most of the time this happens inside the females' bodies (Poecilidae and Carcharinidae), but in some species (Sygnathidae) as Hippocampus, the fertilization and incubation takes place inside the male specimens' bodies. This is the easy part. But let us take a look at the breeding events taking place among what we call egg layers.
Many species are free spawners. They release their genetic material (milt and ova) into the water column (i.e. many of the marines), so fertilization happens accidentally due to currents or other natural events. These species breed either in pairs or in schools. Spawning teams are composed of one dominant ♂, one dominant ♀ and the subdominant individuals (♂♂ and ♀♀), or only one dominant ♂ with its female harem (m'bunas) or even the opposite of this, as is common with Corydoras and Amphiprion species.
A number of free spawning species will glue their clutches onto plantation (Carassius auratus), on rocks, in crevices and on underwater walls. Though rare, there are some species that deposit their eggs inside living mussels (Rhodeus amarus). Except for the free spawners, other egg layers exhibit numerous "styles" of breeding and show a great deal of mating, incubation, carrying and care of their fry. All these styles separate fish species into many categories based on these breeding behaviors. Some keep their eggs, larvae and fry in the cavities in their mouths (mouth brooders) until the fry become developed fishes capable of surviving, before releasing them in the open water. "Carrying" females release their fry about the same time in the sallow water region of their underwater habitat in the wild.
Many of them build nests. There are many kinds of nests these fishes use for spawning. Some of these so - called nests are just spawning sites like plants' leaves (Pterophyllum scalare scalare), flat stones (Heros severus), holes (Mikrogeophagus ramirezi), rockworks (Julidochromis ornatus) and crevices (Altolamprologus compressiceps), caves (Thorichthys meeki) or simply a clean wide place, safe as possible, on the opened substratum (Nimbochromis venustus). All of them defend the territory of their nests, and for the most part the care of eggs, larvae and fry is biparental (from both parents).
The cave spawners can be separated in two different kinds: one type is monogamous (one ♂ and one ♀ as permanent breeding pair), and the guarding of their nests and their "product" is either biparental, maternal (from the mother only) or colony duty (Neolamprologus brichardi).The others are polygamous. These species form female harems with one dominant ♂, or they form colonies with a complicated hierarchy. They use natural indentations for nesting sites and they do not build nests.
Some glue their eggs on the ceiling of the spawning cave (Pelvicachromis pulcher). Ancistrus species, for instance, use a vertical cavity in bogwood and one ♂ mates with several ♀♀. He then chases them out of the nesting site right after spawning and becomes a single father, taking care of both eggs and larvae (paternal care).
The ones that build nests dig them in soft substrates or use holes that they improve by enlarging and cleaning them and by making them safer for spawning. Some even use empty shells for breeding (Lepidiolamprologus callipterus).
♂♂ Belondidae construct bubble nests on the water surface between floating vegetation. These ♂♂ also take care of the nest, eggs and larvae. At least one species of Betta is recorded as a paternal mouth brooder (Betta unimaculata).
The substrate spawners are either monogamous or polygamous. Some of them use horizontal, while some others use vertical, nests. Some die soon after spawning due to dry season, and their eggs are preserved inside the moist muddy peat until the next rainy season (killifishes) when they hatch.
In mouth brooding species, the fertilization is either external or totally internal (oral). These species that perform external fertilization are usually monogamous and biparental. They build nests by digging caves, and some breed simultaneously, while others change mates alternatively for some reason.
There are some species that are specialized because of the time fertilization takes place, the size of eggs and the lack of care of the released fry from the male specimens. The special methods of exchanging the larvae between the two parents is also a good reason of further breeding taxonomy (i.e. Erythrodus cyanostictus).
There are also monogamous but maternal mouth brooders. Both sexes care for the eggs, larvae and fry and maintain polygamous communities of maternal mouth brooders with one dominant ♂ individual and several ♀♀. Cyphotilapia frontosa is one of these, but the ♂ releases the milt in a depression of the substratum before the ♀ lays the eggs in it (pre-oviposition). When the ♂ is "done", the ♀ enters the depression, lays eggs, and swimming backwards, picks them up.
There are polygamous species, but also maternal mouth brooders, that spawn either on the substratum or in the open water.
Some species establish temporary spawning sites (Satanoperca leucosticta), while others protect their territory permanently, so they offer themselves a permanent breeding place. These species perform oral fertilization but by dint of mouth brooding. Some other species that spawn either on substratum or in the open water exclusively fertilize their eggs orally.
It seems every single species has its own feeding and breeding techniques that are unique. This fact makes some species very popular even if the look of these species are not anything special enough (colorful with great fins, etc) to make someone keep them as ornamental pets. Some cases like these have made this hobby so special, and they have taught us hobbyist that beauty is beyond colors and shapes, and this drives us to enrich our criteria for fish keeping.
When we know their “ways” we know their demands and we can arrange for their husbandry correctly. We can provide them with enough space, spawning sites, the suitable aquascaping, the right filtration, the essential lighting and tank mates that they can tolerate and are tolerant of them. We must keep in mind that this is not the end of the story. There are many species and such a large variety of feeding and breeding demands making it impossible to describe all of them in only a few pages.
There is a vast bibliography about this very important topic that we can read to evaluate observations of our own tank mates and to learn and discover things about these vital strategies that characterize fish species.
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