Reproductive Strategies Egg-layers

Reproductive Strategies Egg-layers

The majority of aquarium fish are egg-layers with external fertilization. Egg-layers can be divided into five groups: egg-scatterers, egg-depositors, egg-burriers, mouth-brooders, and nest-builders.

Egg-scatterers: These species simply scatter their adhesive or non-adhesive eggs to fall to the substrate, into plants, or float to the surface. These species do not look after their brood and even eat their own eggs. These, often schooling, fish may spawn in groups or in pairs. Often there is a large number of the small eggs laid. The fry hatch quickly. Egg-depositors: These species deposit their eggs on a substrate (tank glass, wood, rocks, plants).

Egg depositors usually lay less eggs than egg-scatterers, although the eggs are larger. Egg-depositors fall into two groups: those that care for their eggs, and those that do not. Among eggs depositors that care for their eggs are cichlids and some catfish. Egg-depositors that care for their young can be divided into two groups: cavity spawners and open spawners.

Cavity spawners lay their eggs in a cave, while open (shelter) spawners lay their eggs on an open surface. These fish form pairs and have advanced brood care where the eggs are defended and cleaned.

The eggs take a few days to hatch, and the fry are often guarded by the parents. Various catfish, Cyprinds, and Killifish make up the majority of egg-depositors that do not care for their young. These species lays their eggs against a surface, where the eggs are abandoned. These species do not usually eat their eggs.

Egg-burriers: These species usually inhabit waters that dry up at some time of the year. The majority of egg burriers are annual Killifish which lay their eggs in mud.

The parents mature very quickly and lay their eggs before dying when the water dries up. The eggs remain in a dormant stage until rains stimulate hatching.

Mouth-brooders: Are species that carry their eggs or larvae in their mouth. Mouth brooders can be broken up into ovophiles and 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 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 a mouthful of sperm, fertilizing the eggs in her mouth. Many cichlids and some labyrinth fish are ovophile mouthbrooders.

Larvophile or larvae-loving mouth-brooders lay their eggs on 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.

Nest-builders: Nest builders build some sort of nest for their eggs. T

he nest is usually in the form of bubble-nest formed with plant debris and saliva-coated bubbles (labyrinth fish, catfish), or a excavated pit in the substrate (cichlids). Nest builders practice brood care.