Austrolebias nigripinnis Regan, 1912, La Plata, Argentina.
OTHER COMMON NAMES
A small species, 2–2.75 in (5–7 cm) and rarely more than 2 in (5 cm) long. Relatively deep-bodied and sexually dimorphic and dichromatic. Males are larger than females. All fins are blue-black with an iridescent greenish overlay on the pectorals. Fins are rounded, with relatively large anal and dorsal fin bases. Iridescent metallic-green margin on the dorsal fin and similar margins on the anal and caudal fins are made up of a series of separate spots. Opalescent whitish to greenish spots on all fins and the body, forming five to 11 vertical bars. Lines paralleling the fin edges on the unpaired fins. Body color is sometimes pale around the abdomen. All intensities and patterns vary widely. The female has smaller rounded fins and brown mottling on the body, dorsal fin, and anal fin. Clear caudal, ventral, and pectoral fins and whitish abdominal area.
The La Plata River basin in Uruguay and Argentina.
Inhabit temporary waters, such as flooded meadows, shallow ponds, and roadside ditches.
The male takes over an area, which it defends against other males. A female moves in, signaling her receptivity by tilting toward the substrate. The male joins the female, and they move side by side with their heads together. The pair spawns directly on the substrate or, conditions permitting, by diving into it. In an aquarium with more than one male, a dominant male, obvious by his black body and fins, defends a spawning area of his choice; the color of the other males fades to light gray, with some black or brownish blotching. If the aquarium is heavily planted so that the males cannot see each other, more than one dominant male may appear.
FEEDING ECOLOGY AND DIET
The species feeds on live foods, such as aquatic and terrestrial insects, worms, crustaceans, and other aquatic invertebrates. In aquaria live foods (such as fruit flies, brine shrimp, chironomid larvae, tubificid worms, and daphnia) are accepted eagerly and almost everything else is rejected, with the exception of chopped earthworms and certain paste foods.
Eggs placed in the substrate during spawning go into diapause. When the temporary waters evaporate, the adults die off, but the eggs survive until they hatch in the next rainy season, within hours of being wetted. Aquarists simulate this environment by providing garden peat moss as the substrate, periodically collecting the peat and storing it away in an almost dry state at a temperature of about 70°F (20°C). When the peat is flooded after two to four months of storage, most of the eggs will hatch. If the eggs do not hatch, the peat can be dried again and flooded at a later date.
Not listed by the IUCN.
SIGNIFICANCE TO HUMANS
The blackfin pearl killifish is exchanged among aquarium hobbyists but only rarely becomes available in the aquarium trade.
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