Alternative name Melanorivulus megaroni.

Rivulus megaroni is described from the Xingu River drainage, southern Amazonas River basin, central Brazil. It is similar to other species of Rivulus endemic to the southern Amazonian tributaries of central Brazil by having a unique color pattern of flank in males, consisting of red marks arranged in a chevronlike pattern, in which the chevron vertex is placed on the ventral portion of the flank. The new species is distinguished from all other species sharing that color pattern by a combination of 34-36 scales in the longitudinal series,seven well-developed pelvic-fin rays, chevron marks of flank arranged as oblique bars, absence of red pigmentation on the tip of the lower jaw, a horizontal series of white spots on the dorsal portion of the caudal fin in females, and caudal fin pink in males.

Stream crossing road BR-080, 7 km east of the right bank of the Xingu River,about 10°43'S, 53°00'W, Parque Indígena do Xingu, Municipío de São José, Estado de Mato Grosso, Brazil.

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 litres 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 coloured. 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 :

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Dorsal 00.0,
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Costa, W.J.E.M., 2009. Rivulus megaroni, a new killifish from the Xingu River drainage, southern Brazilian Amazon (Cyprinodontiformes: Rivulidae) Ichthyol. Explor.freshwaters, Vol. 20, No. 4, pp. 365-370,