Ilyodon furcidens

The states of Jalisco and Colima, Mexico.

Inhabits fast-flowing streams and small rivers with varying biotopes.

75 ∗ 30 ∗ 30 cm30 ∗ 12 ∗ 12 in

A planted aquarium with some floating cover and a scattering of smooth rocks is ideal for I. furcidens. A good flow of water is also appreciated as these fish prefer well-oxygenated water.

Temperature: 18 – 24 °C64 – 75 °F

pH: 7.0-8.0

Hardness: 10-20 dH

Omnivorous and unfussy they will accept most foods offered. They do consume large amounts of algae in their natural habitat so some greenstuffs should be included in the diet.

A peaceful fish and can be kept in a community tank provided the other species can cope with the lower temperatures required. Males may squabble amongst themselves but physical damage is rare.

Males are smaller, more colourful and possess an andropodium (this is a notched anal fin used for reproduction).

Easy. Livebearer. Should be mated in a species aquarium and can be bred using a single pair or a group (flock spawning). The breeding tank should contain lots of plants. Goodeids breed in a slightly different way to other livebearers. Females do not store sperm as in many other livebearing species and must be mated separately for each brood of young. They also display no gravid spot.

Gestation takes between 7-8 weekss after which 5-50 huge (up to 1.5 cm0.6 in"!) fry are produced. Sometimes these may have what appears to be an umbilical cord attached. This is quite normal (see below) and will disappear in 2-3 days. The fry are large enough to accept the same foods as the adults from birth and will be bold and outgoing from the outset, competing for food with any other fish in the aquarium. The parents rarely predate on the fry.

The species name 'furcidens' is derived from the interesting fork-shaped teeth of this fish. This species may develop a cervical hump as it matures. As with other goodeids, there is less of a size difference between the sexes than in many other livebearers. This is thought to be related to the relatively primitive structure of the andropodium, as the fish tend to choose mates that are of similar size so that the sex organs are synchronised.

Goodeids are unique among livebearers in that the developing young are nourished by a specialised structure known as the trophotaenia. This performs a similar function to the placenta in mammals and the remnants of it can often be seen attached to the young fish at birth. Male fish also possess an internal muscular structure known as a pseudophallus, which connects the sperm ducts to the genital opening, and is said to forcibly eject sperm.

Also referred to as the Goldbreast Splitfin.