Butterfly goodeid

Ameca splendens

Order: Cyprinodontiformes

Family: Goodeidae

Genus: Ameca

The butterfly goodeid is a critically endangered livebearing freshwater fish known for its shimmering, metallic sheen and striking colouration. Males are particularly eye-catching, with iridescent bodies and distinct black-and-yellow banded tail fins that resemble butterfly wings, especially during courtship displays. Adults typically reach 8 to 12 centimetres in length, with females being slightly larger and more robust.

This species is the only member of its genus (Ameca), and exhibits a compressed body shape, large eyes, and a terminal mouth adapted for omnivorous grazing. Butterfly goodeids are social fish that form loose shoals and display complex mating and territorial behaviours.

The butterfly goodeid has a stocky high-backed body with a pointed head. The general colour is brown on the back with sides that are silver fading to white on the belly. The flanks of the male fish are overlaid with scales that reflect green, blue or yellow from light. The whole of the body is covered with dark spots. Males exhibit a dark lateral line and the caudal (tail) fin is edged in yellow with a black band. The females have black stripes or mottled bands on the body but not the reflective scales of the male. Fins are normally yellow at the point where they join the body, with black markings on the yellow, and then fade to clear. They develop more intense spotting and colour definition as they get older.

Conservation Status: IUCN

Distribution

Rio Ameca, Rio Teuchitlan, Jalisco, and Mexico (extinct in the wild).

Habitat

Warm neutral to slightly alkaline freshwater streams and rivers with lots of vegetation. Depth range two metres.

Diet

Live worms or aquatic animals that will fit into its small mouth; likes to browse on water plants, green hair algae or blue-green algae. They are known to eat duckweed.

Reproduction

Fertilization is via an internal oviduct with a placenta-like organ that allows them to give birth to large fry. They are livebearers. The belly of a pregnant female becomes almost square in appearance as she reaches term. Gestation lasts 55 to 60 days after which 6 to 30 large (2 cm.) fry are born. Frequently fry are born with the umbilical cord still attached; this cord disappears in two to three days. This species does not store sperm and must mate for each batch of fry. From the first day, the fry eat the same food as the parents. The parents do not bother the fry, which look after themselves from birth.

Adaptation

This fish is extinct in the wild and is now bred as an aquarium hobby specimen. It requires hard alkaline water up to 28¢ª C in the aquarium. It can share its habitat with most other species of livebearers, but has a tendency to nip at the fins of other fish as tiger barbs do. In captivity it eats baby brine shrimps and grindal worms.