Nannostomus nitidus WEITZMAN, 1978

Shining Pencilfish

Etymology

Nannostomus: from the Latin nannus, meaning ‘small‘, and Greek stoma, meaning ‘mouth’, in reference to the small mouthparts of member species.

Classification

Order: Characiformes Family: Lebiasinidae

Distribution

Described from ‘Igarapé Candiru-Mirim, Rio Capim, Pará, Brazil’, a relatively short river draining into the rio Pará near the city of Belem, eastern Brazil.

Records of similar-looking fish exist from Santarém, Pará state, in the central Amazon region, and the coastal city of Fortaleza, Ceará state, much further southeast. These may require confirmation.

Habitat

Likely to inhabit sluggish tributaries, small rivers and swampy areas, particularly in areas with dense growth of aquatic vegetation or submerged woody structures and leaf litter.

The record from Santarém mentioned in ‘Distribution’ states that it was collected alongside the congeners Nannostomus digrammus and N. limatus.

Maximum Standard Length

30 – 35 mm.

Aquarium SizeTop ↑

Base dimensions of at least 60 ∗ 30 cm or equivalent are required.

Maintenance

Should ideally be kept in a heavily-planted set-up, preferably with a dark substrate.

The broken lines of sight that exist in such a display allow it to display natural behaviour as well as helping to reduce skittishness.

Floating plants are a useful addition as are driftwood branches and dried leaf litter, the latter in particular driving establishment of microbe colonies as decomposition occurs.

Such microorganisms can provide a valuable secondary food source for fry, whilst the tannins and other chemicals released by the decaying leaves are also thought beneficial.

Filtration need only be gentle with an air-powered sponge-style unit normally adequate, though a degree of water movement is acceptable.

Water Conditions

Temperature: 23 – 28 °C

pH: 4.0 – 7.0

Hardness: 18 – 143 ppm

Diet

A micropredator feeding on tiny invertebrates and other zooplankton in nature.

In the aquarium it will accept dried foods of a suitable size but should also be offered daily meals of small live and frozen fare such as Artemia nauplii, Moina, grindal worm, etc.

Behaviour and CompatibilityTop ↑

Relatively peaceful and will not  compete well with very boisterous or much larger tankmates.

In a community it’s best kept with similarly-sized, peaceful characids and smaller callichthyid or loricariid catfishes but sedate surface-dwellers such as hatchetfishes are best omitted, especially in smaller aquaria.

It also makes an ideal dither fish for Apistogramma spp. and other dwarf cichlids since  it tends to inhabit the middle-to-upper regions of the tank, and does not often predate fry.

In a more general community set-up it can be combined with smaller rasboras, barbs, anabantoids, etc.

Buy as many as possible, ideally 10 or more, as when kept in larger groups any aggression is spread between individuals plus the fish are bolder and exhibit more natural behaviour.

Sexual Dimorphism

Adult males are usually slimmer and more intensely-patterned than females.

Reproduction

An egg-scattering free spawner exhibiting no parental care.

When in good condition adults will spawn often and in a mature aquarium it’s possible that small numbers of fry may start to appear without intervention.

However if you want to maximise yield a more controlled approach is required.

The adult group can still be conditioned together but a smaller aquarium should also be set up and filled with mature water.

This should be very dimly lit and the base covered with some kind of mesh of a large enough grade so that the eggs can fall through but small enough so that the adults cannot reach them.

The widely available plastic ‘grass’-type matting can also be used and works well, as does a layer of glass marbles.

Alternatively filling much of the tank with a fine-leaved plant such as Taxiphyllum spp. or spawning mops can also return decent results.

The water itself should be of slightly acidic to neutral pH with a temperature towards the upper end of the range suggested above.

An air-powered sponge filter or air stone(s) should also be included to provide oxygenation and water movement.

When the adult fish are well-conditioned a single pair or group comprising one or two males and several females can then be introduced to each container, though it’s worth noting that the more individuals involved the greater the risk of egg predation, plus males may distract each other from females if there’s more than one in the tank.

The adults can be removed after 2-3 days and the first fry should be visible around 3 days later. Initial food should be Paramecium or a proprietary dry food of sufficiently small (5-50 micron) grade, introducing Artemia nauplii, microworm, etc., once the fry are large enough to accept them.

In memory of the late expert fish-breeder Alan P. Vaissiere who assisted extensively with this section.

NotesTop ↑

This species is poorly-known in the aquarium hobby and is rarely traded in numbers, more often being seen as bycatch among shipments of other species.

It’s sometimes referred to as ‘glittering pencilfish’.

Apart from the brightly-coloured lateral stripe above the primary dark lateral stripe in males, it can be told apart from congeners by the following combination of characters: possession of primary and secondary lateral body stripes; narrow nocturnal oblique bars present, of which the anteriormost does not extend far past the anterior dorsal-fin origin; adipose-fin present (but see below); 23-25, usually 24, scales in the lateral series; 0-2 perforated lateral line scales; 34-35 vertebrae; 10-11+16-18 gill rakers; 2-3 simple, laterally-placed conic teeth in inner dentary; 10 rays in upper caudal-fin lobe, 9 rays in lower lobe; anal-fin of male slightly modified with thicker rays than female.

Although the description states that N. nitidus possesses an adipose-fin, 24% of fry raised from captive wild adults did not possess this fin and thus questions have been raised about the validity of N. limatus, a similar-looking fish that does not have an adipose-fin according to its description (Zarske, 1993).

The only other characters separating the two species are that N. nitidus has 2-3 inner dentary teeth and lacks a tertiary lateral stripe on the body, while in N. limatus the opposite is true.

Weitzman and Weitzman (2003) state that further study is required to confirm the validity of these two ‘tentatively distinct’ taxa.

Don’t worry if your fish look different when you switch on the aquarium lights after dark or in the morning as like most Nannostomus species it assumes a cryptic, vertically-barred colour pattern at night.

This diurnal rhythm has been show to occur in blind specimens, suggesting it’s an automatic response that the fish cannot control.

The family Lebiasinidae is included in the order Characiformes and sometimes split into the nominal subfamilies Lebiasininae and Pyrrhulininae, though there has not been a major review of the grouping in recent times.

All lebiasinid genera possess a relatively long, elongate body shape with 17-33 scales in the lateral series and laterosensory canal system absent or reduced to 7 scales or less.

Some species have an adipose fin while others do not, and the anal-fin has a relatively short base of 13 scales or less.

In the majority of members males have an enlarged or otherwise well-developed anal-fin used in courtship and spawning. The frontal/parietal fontanelle is always absent, the cheek well-covered by the orbital and opercular bones, the supraoccipital crest is absent, and the scales of the dorsal body begin over  the parietal bones.

Characiformes is among the most diverse orders of freshwater fishes currently including close to 2000 valid species distributed among 19 families.

This tremendous taxonomical and morphological diversity has historically impaired the ability of researchers to resolve their genetic relationships with many genera remaining incertae sedis.

A further limiting factor has been that in many cases exhaustive study of these on an individual basis is the only way to resolve such problems.

Modern molecular phylogenetic techniques have allowed some headway, though, and a research paper by Calcagnotto et al. published in 2005 revealed some interesting hypotheses.

Their results suggest that Lebiasinidae forms a trans-atlantic, monophyletic clade alongside the families Ctenoluciidae and Hepsetidae, this clade further forming a sister group to Alestidae.

Others such as Oliveira et al. (2011) have concluded that the family Erythrinidae is also closely-related to this grouping with Hepsetidae and Alestidae more distant.

References

1. Weitzman, S. H., 1978 - Smithsonian Contributions to Zoology 263: 1-14
   Three new species of fishes of the genus Nannostomus from the Brazilian states of Pará and Amazonas (Teleostei: Lebiasinidae).
2. Calcagnotto, D., S. A. Schaefer, and R. DeSalle, 2005 - Molecular Phylogenetics and Evolution 36(1): 135-153
   Relationships among characiform fishes inferred from analysis of nuclear and mitochondrial gene sequences.
3. Oliveira, C. A., G. S. Avellino, K. T. Abe, T. C. Mariguela, R. C. Benine, G. Orti, R. P. Vari, and R. M. Corrêa e Castro, 2011 - BMC Evolutionary Biology 11(1): 275-300
   Phylogenetic relationships within the speciose family Characidae (Teleostei: Ostariophysi: Characiformes) based on multilocus analysis and extensive ingroup sampling.
4. Weitzman & Weitzman in: Reis, R. E., S. O. Kullander, and C. J. Ferraris, Jr. (eds), 2003 - EDIPUCRS, Porto Alegre: i-xi + 1-729
   Check list of the freshwater fishes of South and Central America. CLOFFSCA.
5. Weitzman, S. H. and J. S. Cobb, 1975 - Smithsonian Contributions to Zoology 186: i-iii + 1-36
   A revision of the South American fishes of the genus Nannostomus Günther (family Lebiasinidae).