Abstract A new annual killifish species, Moema beltramonorum, is described from a seasonal swamp next to arroyo Crespo, belonging to Río San Martin, a tributary of Río Iténez, Amazon River basin, Bolivia. The new taxon presents an unique combination of male colour pattern characters not present in any congener, and an unique caudal fin coloration.

Introduction The Neotropical annual fishes of the genus Moema (Rivulidae) are seasonal, being uniquely found in temporary pools formed during the rainy seasons, a unique life style occurring both in American and African aplocheiloid killifishes (e.g., Parenti 1981; Costa 1998). A great proportion of the species of the genus have been discovered in this century, probably as a result of the incipient state of exploration of the ichthyofauna inhabiting isolated temporary pools within savannah and forested areas, which were (and still are) rarely sampled, and also because ichthyological expeditions are mostly conducted during the more accessible dry season. The genus Moema was originally proposed as a genus to include M. piriana Costa, 1989, the type species, and M. portugali Costa, 1989, both described from the Brazilian Amazon, and was then diagnosed by presenting a pointed pectoral fin and dentary with a ventro-proximal process (Costa 1989). Aphyolebias was described nine years later (Costa 1998), diagnosed by the metapterygoid being dorsally constricted, presence of posterior dorsal and ventral extensions on the caudal fin in males, a dark brown to black humeral spot, and a narrow black margin on the ventral margin of the pectoral fin in males, comprising Moema peruensis (Myers 1952), the type species, and other three species from the western Amazon River basin in Peru and Bolivia. More recently, Costa (2014) have shown that because of the rapid increase of known species in both Moema and Aphyolebias the known geographical range of both genera progressively overlapped and generic diagnostic features were not applicable to some described taxa, making generic limits unclear.

In the same publication, that author has showed that both genera cannot be properly distinguished, and additionally, a phylogenetic analysis supported M. staecki as being more closely related to M. peruensis than to M. piriana. Consequently, Aphyolebias was considered a synonym of Moema by Costa (2014), and the genus was then morphologically rediagnosed by its unique opercle shape, which has the ventro-posterior part expanded, and its dorsal portion distinctively longer than the ventral portion, and by a pectoral fin with distal portion narrow, forming a long-pointed tip (Costa, 2014). The genus Moema currently includes 21 valid species and its geographical range comprises mostly the central and western portions of the Amazon basin, but also extending into a coastal river system in Pará state (Rio Morcego) and the upper Rio Paraguai basin in the Pantanal region (Costa 2003, 2008; Valdesalici et al. 2015; Valdesalici 2019)). A new species recently discovered from Rio Iténez drainage (called RioGuaporé in Brazil) in Bolivia is herein formally described

Keeping and breeding Moema is easy but it takes some patience from the breeder, a bigger breeding tank and special breeding container. The eggs need long incubation periods up to 10 months. Normally eggs are ready to hatch after 5 to 6 months.

To produce many eggs the parents need to get life food only in a rich varity and quantity. As all fast growing SAA's they do not like dry food and rather die than get used to is. Sometimes they eat frozen foods also but you should never skip the life food for them. They can be very productive and the best set-up is one male and 2 or more females in a tank from 30 to 50 litrs or more. Males are not to agressive against female as you will see.

They are peacefull fishes and only males can get agressive to each other especilally if they are separated from each other for a while before.

Storing the eggs is easy to but, as said before, a matter of patience. You must boil the peat, before you use it in the breeding tank. I use deep containers with peat to avoid food enters the peat and later affects the eggs. This also to keep the amount of peat as small as possible but the layer high enough to dive in completely. After spawning during 2 weeks the peat is squeezed out and dried to an level of fresh tabacco. Store it at 25 C. in a dark place. After a few months it is wise to look into the peat if eggs are stil there and if any development in it is visable already. Because it need of a long incubation time it is recommended to check the peat bi- monthly to assure it is still wet enough. If peat is put away very moist and warm (up to 28 C.) is is possible the eggs will hatch in an earlier stage. It is however also possible the eggs disappeare fully by fungus if you do so.

There lifespan can be up to 1.5 years in captivity but they will not get that chance in their natural invironment.

Max. size 38.7 mm S.L..
Dorsal 9-10,
Anal 14-16,
D/A 11-12,
LL scale count 32-35
Pre- dorsal length -71.7 to 76.1 to % SL
Depth to % SL average 21.5 %