 Rivulus breviceps, |
History
Alternative name: Laimosemion breviceps.
The history of Rivulus breviceps is long. This species was a new discovery in 1908 made during the expedition of Carl H. Eigenmann et al. from the well documented Carnegie British Guiana Expedition, September, 1908. They returned with 25,000 specimens, resulting in the description of 128 new species of all kind of fish families. Eigenmann didn't bring fishes alive because this was impossible at that period as he was travelling for many months in the field. After the discovery it would take almost 83 years (1991 Vermeulen & Suijker) until the author of this site followed the footsteps of Eigenmann to rediscover the species in Guyana at the top of the Kaieteur Falls.
Eigenmann discovered the species at the foot of the Kaieteur at Shrimp Creek, where the path from Tukeit to Kaieteur crosses. The name is derived from the Latin (brevis = short) and from the Greek (ceps = snout) and refers to the short snout of the species.
Rivulus breviceps is closely related to Rivulus lyricauda from neighbouring Venezuela. Following Huber, KilliDataOnline, Rivulus breviceps forms a clade with R. gransabanae, R. lyricauda, R. mahdiaensis, R. paryagi, R. sape and R. torrenticola.
Rivulus breviceps was found together with Rivulus waimacui, sometimes in open area in shallow creeks on the stone plateau and sometimes under the roof of the primary forest as well.
The images above show young animals from my last expedition in 2006 to Guyana accompanied by Siegmund Sladkowski, Michael Schlüter and Bernd Schölzel, all from Germany.
Reproduction
Breeding is not easy, eggs are rather big ( 2 mm) and also the species is not very productive. They do not like temperatures above 23 C. as result of their presence at high altitudes where it get's cold during the nights.
In fact it takes a lot of care to breed the species in sufficient numbers for one’s own use, let alone distribution.
Normally, males and females are in even numbers and growth rate is rather slow. R. breviceps reach adulthood after 5 to 6 months and the first eggs will be produced at 4 months at the earliest. Lifespan is 2 to 3 years. It is best to keep them in small tanks, one male per tank only because sometimes males can fight intensely and dominant males can damage other smaller males severely. You must provide some cover like mops or Java moss and a tank bottom with peat moss or other dark material.
The species is found in open water (see image biotope) but prefer the dark cover of primary forests.
So light is not something they adore, they probably will do better in subdued lighting. Strangely though, during all visits, we found R. breviceps , at the end of the airstrip in sunny open landscape but none were seen in that rivulet during the last visit in 2006.Remarks :
The species is adapted to cold temperatures as it lives high in the mountains. Temperatures should not exceed 23º C. Better 18 - 20 C.
Variations
Map
Meristics
Max. size 3.5 cm.
Dorsal 10.6,
Anal 13.5,
D/A 6.3
LL scale count (average)31.8
Pre- dorsal length to % SL – 70.6 %
Depth to % SL – 20.5 %
Literature
Eigenmann, C.H. 1909a. Reports on the Expedition to British Guiana of the Indiana University and Carnegie Museum, 1908. Report no. 1. Some new Genera and Species of Fishes from British Guiana. Ann. Carnegie Mus., 6 (1): 49.