Abstract: A new species of the annual fish genus Austrolebias from the lower Uruguay river basin. The fusion of the urogenital papilla to the first anal fin ray in males and the pigmentation pattern, indicates a close relationship with the clade formed by A. bellottii, A. melanoorus, and A. univentripinnis. The new species can be differentiated from those by the following combination of characters: presence of well-defined light bands contrasting with the sides of the body, the distal portion of the anal fin dark gray, pelvic fins dark bluish green and bases united at about 50–80% on their medial margins, pectoral fins with iridescent blue sub-marginal band, and general coloration of body bluish green. The new species can only be found in wetlands of the Queguay river, an area included in the Uruguayan protected areas system and represents so far the only annual fish species endemic to the lower Uruguay river basin.

Introduction: Austrolebias, one of the most specious annual fish genus in the family Rivulidae, is composed of 47 valid species and is distributed in Bolivia, Paraguay, southern Brazil, northeast Argentina, and Uruguay, in the La Plata, Patos-Merin, and southwestern Amazon basins (Alonso et al. 2018, Calviño et al. 2016, Costa, 2006, 2014, Costa et al. 2017, García et al. 2012, Loureiro et al. 2011, Nielsen and Pillet 2015, Volcan et al. 2014, 2017). In a systematic revision of the genus, Costa (2006) provided three exclusive synapomorphies and three synapomorphies independently arisen in other cynolebiatines. Costa (2006) defined five species groups within the genus. One of them, the “Austrolebias bellottii” species group (clade A4; fig. 1 in Costa 2006), diagnosed by the presence of anteromedian rays of the anal fin elongated in females (triangular fin shape) is composed of two subclades: the “Austrolebias adloffi” species group (clade A5, fig. 1 in Costa 2006), diagnosed by chromatic characters; and an unnamed clade that lacks morphological diReceived 15 August 2018 Accepted 20 October 2018 Published 22 November 2018 Academic editor: Peter Bartschagnostic characters. This clade is composed of A. bellottii (Steindachner), A. vandenbergi (Huber), A. apaii Costa (all from La Plata basin), A. melanoorus (Amato) (from La Plata and Patos Merin basins), and A. univentripinnis Costa and Cheffe (from Patos Merin basin).

Afterwards, based on another morphological phylogeny, Costa (2010) added A. patriciae to the “A. bellottii” species group. In addition, Nielsen and Pillet (2015), described a species from the upper Mamoré river basin (Amazon basin), A. accorsii, morphologically very similar to A. vandenbergi.

However, Alonso et al. (2016) questioned some of the diagnostic characters for A. acorsii. In spite of the low statistical support of A5 and the unnamed clade in morphological analyses (Costa 2006, 2010), mitochondrial and total evidence phylogenetic reconstructions, support the monophyly of both clades (García et al. 2002, 2012, 2014, Loureiro and García 2008; Loureiro et al. 2018). However, these analyses differ in the relationships between and within them, and with other Austrolebias species groups.

According to Garcia et al. (2014) and Loureiro et al. (2018), A. patriciae is not closely related to the “A. bellottii” species group, and according to Garcia et al. (2012), A. apaii should be con- sidered a synonym of A. bellottii, a proposal that was followed by Calviño et al. (2016). In this article we describe a new species of Aus- trolebias from wetlands of the Queguay river (lower Uru- guay river basin), that shares similar morphological traits to the clade formed by A. bellottii, A. melanoorus, and A. univentripinnis.

Source: the original description at: zse.pensoft.net

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>.

Remarks;

This is a recently (2018) described species and no actual breeding info for this species is available.

Max. size 00 mm in males - female smaller.
Dorsal (average, male only ) 00.0,
Anal (average, male only ) 00.0,
D/A (average, male only ) 0.0,
LL scale count (average) 00.0
Pre- dorsal length to SL – 00.0 %
Depth to SL – 00.0 %
Vertebrae count (average) 00.0