Extraordinary Pencilfish "species" Nannostomus sp. Rio Amaya

Byron

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This photo was posted in the characin study group today. It is as yet undescribed so may or may not be a distinct species, but it is certainly stunning in its colouration. The fish was found in the Rio Amaya in Peru.

I recall when Nannostomus mortenthaleri was first collected from the Rio Nanay near the town of Alvarenga in Peru in 2000 and initially assumed and described as a sub-species of Nannostomus marginatus by Paepke & Arendt (2001), but it was subsequently established as a valid distinct species by Weitzman et.al. in 2001.

Shortly thereafter another similar species, N. rubrocaudatus, was discovered in the Rio Marano in Loreto Province, Peru. This fish remains among branches in the habitat; collectors must consequently catch each fish individually, something that is reflected in the much higher cost for this species and probably why it is much less often seen in the hobby. This species was described as a distinct species by Axel Zarske in 2009. The species epithet comes from the Latin rubro [=red] and caudatus [=tail], referring to the red on the caudal fin.

The species N. marginatus has been known for more than a century now, and is widespread over the Amazon basin in tributary streams of the Rio Negro; it also occurs in Guyana and Suriname. It is found in slow-flowing streams and swampy pond areas. As a widespread polymorphic species, there have been discovered distinct populations occurring in the Guyanas and in several widely-separated areas in the Amazon basin (Weitzman, 1966). At least three distinct colour variants are known. The original description by C.H. Eigenmann in 1909 used specimens collected in Maduni Creek, Guyana. The populations from the lower and upper Amazon basins may prove to be sufficiently different after further study to merit subspecific recognition (Weitzman, 1966).

The genus name Nannostomus comes from the Greek meaning "small mouth." In common with all pencilfish, the mouth is always open, and the fish in all species except N. espei have a diurnal colour pattern. During darkness, the horizontal lines break up into a series of dashes. This has been observed in blind fish, showing that it is an automatic response to light/dark and not controlled by the fish. N. mortenthaleri and N. rubrocaudatus , like their close relative N. marginatus, do not possess an adipose fin; most but not all characins have this small fleshy fin anterior to the caudal fin. In some of the Nannostomus species, N. eques for one, this adipose fin may or may not be present on fish within the species.

All pencilfish are found in the tribe Nannostomini in the subfamily Pyrrhulininae. Three different genera (Nannostomus, Nannobrycon and Poecilobrycon) were used at various times until Weitzman & Cobb (1975) placed all species in the single genus, Nannostomus, erected by Gunther in 1872 with N. beckfordi as the type species; Gery (1977) separated them into two genera, Nannostomus and Nannobrycon, largely on the basis of the swimming position; the two "Nannobrycon" species swim at an oblique angle near the surface, while all other species swim horizontally. Weitzman & Weitzman in Reis et al. (2003) reassigned the species into the single genus Nannostomus which now includes all described pencilfish.

Oliver Lucannus who has collected this species reports as follows:
The Rio Amaya in Peru is a dark red coloured black water river in the Rio Maranon drainage, check out all the new fish coming from this location: Nannostomus spec. Super red (often called Nannostomus Cenepa ) , Dectrobrycon armeniacus , Knodus spec. new , Eryrthinus super red , Aequidens patricki , Crenicichla anthurus , Adontosternarchus nebulosus , Pyrrhulina species , Hyphessobrycon spec. , Apistogramma spec. Amaya (New Cichlid #18) , Lebiasina elongata , Symbranchus marmoratus. Oliver has a video of the habitat linkd below.

 

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GaryE

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Has anyone here bred any of the blackwater pencilfish?

I've bred N beckfordi, but it is from harder water, and is very easy. The group in the @Byron 's text seems quite hard.
 
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Byron

Byron

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I have had Nannostomus beckfordi and N. eques spawn in tanks, on their own (meaning, I did absolutely nothing to encourage them beyond giving them very soft and acidic water which is what comes out of my tap, or did then). I have had N.marginatus, N. mortenthaleri and N. rubrocaudatus but to my knowledge no spawning, though I am only going by no fry but the fish may well have spawned, there were "behaviours" suggesting this, and the fish ate the eggs or fry. Farther back I've had N. unifasciatus, N. espei, N. diagramatus, N. harissoni,

N. eques spawn in a pair laying/fertilizing an egg on the underside of a leaf, much like Corydoradinae. I observed this many times, but other fish (pencils, Ember Tetra, and cories) ate the eggs, saw that too.

N. beckfordi is rather atypical of this family. Most available fish are now commercially raised, something that is not the case with the other species so far as I know. The species was first described and named as Nannostomus beckfordi by Gunther (1872). There are several colour variations or morphs known, and subsequent to the original naming by Gunther, he or other scientists variously assigned the names Nannostomus anomalus, N. aripiragensis, N. surinami and N. simplex to different colour morphs of this fish under the impression they were distinct species. Weitzman (1966) determined that these are conspecifics and the names are now recognized as synonyms (i.e., invalid) for N. beckfordi. This is a polytypic species with a wide geographical range from the Guyanas and along some 700 air miles up the Amazon River in tributary streams and rivers; further study will likely determine that this species consists of several distinct geographical populations and some of these may prove to be subspecies (Weitzman 1966, Weitzman & Cobb, 1975). This is common with polytypic species within the characiformes (tetras, pencilfishes, hatchetfishes).
 
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Byron

Byron

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There is an article in the current PFK on this fish, which has been assigned the unofficial name Cenepa Red Pencilfish, which is comparable to the CW and L numbers for cories and loricariids. The author has kept this fish, and also mentions other stunning characins from the same watercourse.

 

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