Titanolebias monstrosus, (Huber, 1995)


Described in the genus Cynolebias.

2023, moved to genus Titanolebias.

Titanolebias monstrosus was originally described by Dr. Jean Huber as Cynolebias monstrosus but was transferred to Austrolebias by Costa (1998) as he erected this genus and now transferred to Titanolebias.

Diagnosis: 12-16 dark, rather faint and mood-driven, vertical bars on sides of both sexes (more conspicuous in male) ; low sexual dichromatism, with male showing red dorsal and blue anal, innerly and a dark caudal, distally ; both, with a 120 degrees angled dark eye-bar (Huber, 1995) ; also separated from T. elongatus, according to Costa (2006c), in having fewer dorsal fin rays in male (16-18 vs. 18-20).

Etymology: prone (from Latin: -osus) to be a monster (from Latin: monstrum), in reference to the morphology and its cannibalistic behavior towards small congeners in Cynolebias s.l.

The type locality of Austrolebias monstrosus is near La Serena, Boqueron Department, Paraguay. First discovery was on March 21, 1950 by S. Pierotti. Later the species was rediscovered by Dan and Pat Fromm on October 10, 1992. On March 15, 1994 it was collected again by the dutch Leen & Arjan van den Berg.

Costa placed this species with others in the genus Megalebias (but as turned out this was not a good decision he placed them back in the genus Austrolebias in 2001.

Titanolebias monstrosus. - male. Santa Maria, KCA 75/08. Image made and donated by Jorge Stojan, Argentina.
Titanolebias monstrosus - pair. Santa Maria, KCA 75/08. Image made and donated by Jorge Stojan, Argentina.
Titanolebias monstrosus - detail head. Santa Maria, KCA 75/08. Image made and donated by Jorge Stojan, Argentina.

Close relatives from Titanolebias monstrosus are T. elongatus and T. prognathus. These fishes are seldom seen in the hobby as they requier big tanks, lot of food and special breeding skills.


To breed most Austrolebias, you need a tank with about 10 to 25 liter water in it, a small jar or plastic container of about 10 to 15 cm high, a little bit of well-boiled peat moss, or coco-peat, and a water temperature between 18 and 24 C. It is wise to add a small filter to that tank and change the water regularly for 90 %. Bring one male and, if possible, two or more females in the tank and feed the fishes daily with live food like daphnia, red- and black mosquito larvae, and white worms. Austrolebias does not accept dry food quickly, and also, the prepared cow-heart is not preferred if live food is offered. If possible, breed this genus in larger tanks with more than one pair or trio and give some hiding places if you do so. When breeding with more than one male, you should also provide more than one spawning container. Every male must have one, and you will see they show interesting territorial behavior to attract females into their spawning place.

The male "flinders" around the female, displaying his fins high- up with the most intense colors. As the female is willing to spawn, she follows the male, pressing his head towards the layer of peat, and when the female contact the male's belly, both will dive into the peat layer. This layer should have a thickness of at least the length of the largest animal or, better, some deeper so they can dive entirely into it.

The spawning occurs during the whole fertile life of the fishes, starting at 5 to 6 weeks of age, till they become old and weak or die from the lack of water in their natural environment. This "end-of-life" will be within 8 to 11 months, depending on the temperature. Higher temperatures will trigger more rapid aging.

In the wild, Austrolebias live in colder environments during the wintertime. Temperatures in Uruguay, Paraguay, and Argentina can get very low. Incubation time usually is six weeks if stored at high temperatures ( 25 C.) and more extended if kept at lower temperatures. The development can last five to six months also. So it is wise to check the eggs regularly to see if the eyes inside the eggs are fully developed and the iris is well visible. When "eyed-up," put a part of the peat with the eggs in water at cool (ca. 18 C) temperature. If the fry usually hatches- and swims within a few hours, wet the rest of the peat.


After hatching, feed the fry immediately with freshly born Artemia nauplii. A day or so later, I pour the water together with the fry off and place them in a well-filtered tank without any peat moss to grow up. Austrolebias are not used to strong currents, and juveniles can die if turbulence is too strong. The remaining peat will still have eggs inside that are not ready to hatch yet. Re-pack the peat and store it for some extra time. This hatching delay is nature's answer to short rain showers that fill pools only temporarily, followed by another dry period. Such an event would kill the entire population of the species in that area if all eggs were hatched with first rains. These (late) eggs will hatch later, sometimes very much later, and the fishes that were born earlier will eat these youngs.

As stated before, young's are growing fast and will produce their first eggs after 5 to 6 weeks already, if not even sooner. This breeding information applies to most Austrolebias. However, if the above Austrolebias- species have different behavior or extreme adult size, find these adaptions below in this chapter under <remarks>.


Jorge Stojan wrote:

The biotope of Austrolebias monstrosus "Santa Maria, KCA 75/08" is situated in the province of Salta, Northern Argentina. It is a very dangerous place to go and the most northern record in Argentina. In this biotope the following species live together: Austrolebias monstrosus, Austrolebias vandenbergi, Papiliolebias bitteri, Trionectes aplocheiloides, and Neofundulus paraguayensis. The maximum depth of 1.70 meters was there, PH 7.

Reproduction in aquarium is not easy because the male can grow up to about 17 cm, and the pair need a deep layer of peat that is constantly spread around by the strong movements of fish. The incubation of their eggs is 12 weeks at approximately 25 ° C.


Be aware.... Titanolebias monstrosus is a predetor on smaller fish, also the youngster's that are growing less rapid become food for the bigger ones. Mostly those are the females so males only remain if no action is taken by the breeder. Separate the faster growing fishes directly from the smaller ones is the advise. The use of a breeding container with the entrance- opening at the side can become handy as the fish will not propell all the peatmoss out of the upper opening during the dive.

Biotope of Titanolebias monstrosus. Santa Maria, Nothern Argentina, KCA 75/08. Image made and donated by Jorge Stojan, Argentina.


Max. size 15.0 cm.
Dorsal 17.0,
Anal 22.0,
D/A 7.0
LL scale count (average) 69.6
Pre- dorsal length to % SL – 69.3 %
Depth to % SL – 28.6 %


Huber, J. H. 1995. Nouvelles Collections de Cyprinodones paraguayens, avec Description de 4 Especes Rivulines inedites et Redecouverte d'une Espece a la Localite typique jusqu'alors indeterminee. Assoc. Killliphile Francophone de Belgique, Killi Contact, Aug. 23 (2): 9, fig. 4.

Alonso F., G.E. Terán, W.S. Serra Alanís, P. Calviño, M.M. Montes, I.D. Carcía, J.A. Barneche, A. Almirón, L. Ciotek, P. Giorgis, J. Casciotta, 2023. From the mud to the tree: phylogeny of Austrolebias killifishes, new generic structure and description of a new species (Cyprinodontiformes: Rivulidae) Zool. Journ. of the Linnean Society, XX, 1-30, Fig. 15, Tab. 2.