Alternative genus name Rivulus imperatrizensis.

(Melano)rivulus imperatrizensis collected in a small spring, at the middle rio Tocantins basin, northeast Brazil. (Melano)rivulus imperatrizensis differs from all other species of the genus (Melano)rivulus by possessing all fins orange (vs. orange fins absent in other species of (Melano)rivulus or orange distal stripe on R. dapazi). The hypothesized close relationship between R. imperatrizensis and R. parnaibensis suggests a historical bio-geographic relationship between Southern Amazonian tributaries and Rio Parnaíba.

Holotype: ZUEC 10506, male, 31.8 mm SL: Brazil, Maranhão, Imperatriz, village of Bananal, rio Tocantins basin, 5°39’00.2”S 47°24’08.4”W, altitude 150 m; C. S. Pinto, 25 January 2014. Paratypes: ZUEC 10507, 5 males, 19.0-21.5 mm SL, 3 females, 17.4-19.0 mm SL (2 cleared and stained, 18.6-21.5 mm SL): same data as holotype. 

Keeping and breeding is easy but a tight fitting cover on the aquarium is necessary because their ability to jump, even through the smallest opening, is unbelievable.

This species can, if there is enough space for them, be housed in a tank with more than one male and several females. If separated before and brought together again however, they can be very aggressive towards each other and fight to become the dominant fish. The best way to produce numbers of fry is to put a pair or a trio in a small tank of about 10 litre with a small filter in it or with some aeration. On the bottom of the tank place some peat moss or dark gravel and a floating "mop" to give space for laying their eggs. The fish will, if they are fed a rich variety of live food, spawn during their whole adult life and produce daily between 5 to 15 eggs.

The eggs should be collected by hand and stored for about 14 days in a small container. Eggs are 1.6 mm and amber colored. It is wise to add an anti fungus to the water you store the eggs in, to prevent fungal attacks.

After hatching the young fry can eat fresh artemia nauplii without any problem. It takes 4 to 5 months to raise them to maturity. Often the males far out number females. For some species this can become a major problem for the breeder, as he has to raise many fry to enable distribution of a few pairs to other hobbyists. Recent personal tests found that lower pH levels during the time of hatching gave a higher percentage of females. To achieve this I used some peat moss that I added to the container with the eggs just before they were ready to hatch. This peat moss also is a good way to prevent eggs from being attacked by fungus.

Their lifespan can be up to 3 years in captivity.

Remarks :

The given info in here is based on general experiences with other species in the group. No specific breeding records for this taxon are provided yet.

Max. size 31.8 mm SL.
Dorsal 9-10,
Anal 13,
LL scale count 32-33
Pre- dorsal length to % SL., 71.7-75.8 %
Depth to % SL – 18.4-20.0 %

Nielsen D.T.B. & B.S. Silva, 2015. Melanorivulus imperatrizensis, a new species of killifish (Cyprinodontiformes:
Rivulidae) from the rio Tocantins basin, Brazil. Aqua, Journal of Ichthyology and Aquatic Biology, 21 (2): 136-143, figs.