Garman (1895) described three new species from the central Brazilian Amazon. Rivulus ornatus from Silva, Cudajas, Lago Alexo, and Lake Hyanuari. Concerning these names, Costa (1993/2006) reported the locations' names were incorrect and corrected them into Silves, Codajás, Lago Aleixo, and Paraná do Janauari. Rivulus obscurus from Lake Hyanuari (= Lake Janauari) and Rivulus atratus from Jutahy (Jutaí). Rivulus atratus was designated as type species of the then monotypic subgenus Anablepsoides by Huber (1992).

After examining the type series Costa (2006) noted that original descriptions of R. ornatus and R. obscurus were based on different sexes of the same species. (R. ornatus based on males and R. obscurus based on females), then formally giving precedence to R. ornatus over R. obscurus. The hobby circulates a species also seen as Rivulus ornatus (from Peru), but that species's name is not correct, and this misidentified taxon is recently described as Rivulus collieri by Huber 2021.

The newly described Rivulus amanan is a member of the subgenus Anablepsoides (Huber 1992). Costa made this subgenus a full genus in 2011 and added a large number of species that had a scaled chin. However, in this site and by others, this move is not followed.

Costa & Lazzarotto, 2008: detailed morpho-description in genus Rivulus, subgenus Anablepsoides, diagnosed from related components by color pattern of the Caudal fin in male (upper fin, orangish-red, mid fin black with light blue to greenish-blue stripe, lower fin, dark red to black posteriorly). 

Rivulus amanan is a species from the Amanã lake drainage, Amazonas river basin, Brazil. It was found in shallow places of lentic aquatic biotopes at Igarapé do Baré floodplains, within the Amazon forest.

Rivulus amanan differs from other members of the genus by the unique color pattern of the caudal fin in males, in which the dorsal portion of the fin is orangish-red, the middle black with light blue to greenish-blue stripe, and the ventral dark red to black posteriorly, and by having frontal squamation F- pattern.

Rivulus amanan also differs from the other species of the subgenus Anablepsoides by a combination of pelvic fin reaching between urogenital papilla and base of second anal-fin ray in males, 10-12 anal-fin rays, venter light gray with dark gray dots, and mandibular series of neuromasts not interrupted, with six neuromasts. It is considered to be more closely related to A. ornatus (also known as R. obscurus) by both having the caudal fin with three zones distinctively colored in males.

The name chosen is from the vernacular name "amana" (from Nheengatu: amana = rain water) that sources the name Reserva de Desenvolvimento Sustentavel Amana in which the species is discovered.

No records are available for breeding this species but will not differ from how any other small Rivulus from the Anablepsoides species group reproduce. They are seen as very difficult breeders as they need special attention from the one who keeps the species. In general, keep the water level very low at a max of 10 cm and provide shelter using a thick layer of floating plants and leaves at the bottom. If fed well with small live food like Artemia and mosquito larvae, then collect the fry from the surface or leave them with the parents to grow up.

Best to provide them with brownish, soft, and acid water with pH as low as 4,5 to 5,5 pH. Most likely, eggs are produced only in low numbers because they are relatively big (2 mm) for such small fishes.

Remarks :

First of all, live animals are needed for further study on the reproduction and the behavior of this new species.

To the right a Rivulus obscurus/ornatus image of what was found in Rio Purus, Amazon state, Brazil.

On the image to the left, you see a Rivulus know as R. obscurus, but following Costa, this is R. ornatus. Striking is the "reversed" coloration of the caudal fin compared to the caudal of R. amanan. 

Max. size 0.0 cm.
Dorsal 00.0,
Anal 00.0,
D/A 0.0,
LL scale count (average) 00.0
Pre- dorsal length to % SL – 00.0 %
Depth to % SL – 00.0 %