 Rachovia brevis, |
History
The type locality of this Rachovia brevis is Soplaviento, a small village near the Rio Magdalena in Colombia. The description followed 6 years after its first discovery and import by the journalist Hans Stueve in 1906.
Rachovia brevis was orginally described as Rivulus brevis but moved to Rachovia in 1924.
The name <brevis> is coming from the latin word <short> and refers to the relatively short snouth and compact shape of the body which is more robust than its congerers in some Rachovia and all Rivulus.
I myself was recently (2006, 2008 and 2009) in Colombia for collecting. During this expeditions I was able to relocate the species on different locations between Fundacion and Pivijay and also north of Fundacion along the road to Cienega.
The colour- and body shape changes as getting more to the south upstream the Rio Magdalena and there is a need for further investigation to sort out the different species I found in the area of the Magdalena river as far up as Plato.
Prof. Bruce Turner informed me about the presence of R. brevis as far up the Magdalena river as Barranca Bermeja. I aspect, but need to prove this first, that R. brevis can be found up to the town of Puerto Berrio at coordinates around 06'00"00 N. on the map.
He also pointed me to a brown colored species found just south of Barranquilla, at the opposit side of the Magdalena. The species was part of a commercial export so we cannot be sure about the place they came from. As soon as I can I will hunt for them in the area given.
Rachovia brevis forms with the other components R. hummelincki, R. maculipinnis, R. pyropunctata and R. splendens the genus Rachovia.
Reproduction
As Rachovia brevis is wide spread in northern Colombia and as the area has huge dimensions it is likely the habitats differ in soiltype, temperatures and rain cycle. The local species did all adapt to their specific situation and even than this situation fluctuate from year to year. So it is very difficult to give specific time tables for incubation or for temperature for waterquality and measurements.
To give a sort of indication of the time the species need to incubate I will supply you with the most average information. Please keep in mind that this vary's from one location to the other. Normally 12 to 16 weeks the eggs need to be ready for watering. They are ready if the iris is clearly visible inside the egg schell. It further depends on temperature and humidity of the storage conditions.
The higher the temperature - up to 35 C. is possible - the earlier the development. This can speed up the development at the best to 6 weeks but it is not recommended as there is a major loss of eggs possible. The humidity is also a factor and the wetter the peat the earlier the development. But also here is this not without danger of funges attacs if peat is stored to wet.
The species mostly live on clay bottoms that affect the waters pH they live in and mostly the pH is around the neutral level. So, low pH can also effect the survival of the eggs but does not has effect on the time of development. It is wise to choose a spawning medium that has not a very low pH. Therefore I recomment the use of Coco - peat that is boiled well before it is used.
Rachovia is a productive Genus and many eggs can be produced by one single pair if food of good quality is given. They do not like dry foods but do like life food as mosquito larvae and other small insects. In most cases they also love fresh meat but this is not always good for their guts and overfeeding with meat can lead to siknesses or dead.
Juveniles eat artemia from the moment they are born. The growht is very rapid and whitin 6 weeks they are able to spawn themselves. Females are, at a certain point, to be seperated from the males for reasons they grow less rapad in the first weeks and can become prey to the bigger males easely.
Sexes are most of the time in balance but females do grow slower than males and can become prey than.
As images below show clearly, they normally dive into the substrate but ocasionally they also press there body's into the bottem layer.
During my collecting tours thru Colombia I discovered this species in June in a pool where it was the only fishspecies present. As I went to the same pool again in February 2 years later it was filled with predators, Cichlids and Poeciliae.
My hypothese is that the 2 different rain seasons bring different waterlevels. The main one make the waters rise to a level other fish can encounter the pool from nearby rivers and creeks. The second one only mudfish can develop and live their lives as unique species in that habitat as it was dried out completely before that moment that killed the other species. I assume the other period Killies cannot survive among all predetors.
Variations
Map
Meristics
Max. size 6.0 cm.
Dorsal 10.8,
Anal 15.0,
D/A 7.0,
LL scale count (average)30.1
Pre- dorsal length to % SL – 68.5 %
Depth to % SL – 26.7 %
Literature
Regan, C.T. 1912. A Revision of the Poeciliid fishes of the Genera Rivulus, Pterolebias and Cynolebias. Ann.& Mag. Nat. Hist., 8 (10): 504.
Taphorn, D.C. and J.E. Thomerson, 1978. A revision of the South American Cyprinodont fishes of the genera Rachovia and Austrofundulus with the description of a new genus. Acta Biol. Venez. 9 ( 4) :377-452