Alternative name Laimosemion steacki.

The neotropical killifish genus Rivulus Poey, 1860 is the most species rich within the Rivulidae. Currently it contains more than 145 species which are distributed from Middle America in the north to northern Argentina in the south.

The centre of the species diversity and phenetic manifoldness of the genus is situated in the Amazon and Orinoco drainages. The genus Rivulus is divided into several species groups and formally recognized subgenera (Costa, 2006, 2008a; Huber, 1992).

The new species described here is a member of the subgenus Owiyeye (Costa 2006). This subgenus contained ten species (R. altivelis, R. amanapira, R. kirovskyi, R. mahdiaensis, R. nicoi, R. rectocaudatus, R. romeri, R. tecminae, R. uakti and R. uatuman), which are distributed in the Orinoco and Amazon drainages (Costa, 2006, 2008b; Costa & de Souza, 2009). An eleventh species in this secies group was described named Rivulus tomasi. (Vermeulen et al. 2013)

All these taxa were described within the last three decades, with Rivulus rectocaudatus Fels & de Rham, 1981 as the oldest. They are small fish usually living in forest creeks, shallow ponds and swamps. According to Costa (2006) the subgenus Owiyeye was a monophyletic unit but is placed later in Laimosemion (Costa 2011). The move by Costa to upgrade the subgenus Laimosemion to the genus status is discussed and not followed by the initiater of this site.

Its major diagnostic characters are the transversally arranged frontal scales (S-patterned) and a transverse stripe through the chin (Costa, 2006). During a field trip to the state Amazonas in Venezuela Wolfgang Staeck (Berlin, Germany) collected a new colourful Rivulus possessing the diagnostic character states of the subgenus Owiyeye. The species was introduced in the aquaristic literature as Rivulus spec. “San Carlos de Rio Negro” by Staeck (2006).

Source: Original description.

There are no records about breeding behavior and the fish is not available in the hobby anymore. Keeping and breeding should be 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.

After hatching the young fry can eat fresh artemia nauplii without any problem. It takes 4 to 5 months to raise them to maturity I think.

Eggs may need to be stored on peatmoss or in water. (See remarks).

Remarks :

I assume this species need longer incubation time than other Rivulus. This is also the case with close relatives like R. spec. "Maroa", R. tecminae, R. nicoi and in a lesser degree R. tomasi,. They form a clan that adapt by chance to annual behavior.

If this is tru the eggs need storage on peat only.

Size holotype 28.4 mm.
Dorsal 8-9,
Anal 13-14,
D/A 8-10,
LL scale count 35-38
Pre- dorsal length to SL – 68.8 - 73.2 %
Depth to SL – 19.0 - 21.5 %