Edit Nannostomus digrammus

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Name

Scientific name

Nannostomus digrammus

Described by

Authority Fowler, Year 1913, Bracketed

Family

Lebiasinidae

Common names

Twostripe Pencilfish

Photograph credits

All 5 credited

Summary

The twostripe pencilfish, Nannostomus digrammus, is a lebiasinid from the central Amazon basin in Brazil and the Rupununi basin in Guyana. …

Size and aquarium

Maximum size

30mm, standard length

Aquarium size

Minimum length 45 cm, Minimum depth 30 cm, Water movement Low: still or sluggish water

Water

Water conditions

Temperature 22–28°C, pH 5–7

Hardness

1–10dGH

Conductivity

Not recorded

Behaviour

Temperament

Peaceful

Community suitability

Not for a community

Where it lives

Countries, regions, rivers and lakes

Brazil, Guyana, Amazon, Branco, Madeira, Rupununi, Takutu, Tapajós, Trombetas

Writing

Etymology

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

Distribution

Native to the central Amazon basin with records existing from the Madeira, Branco, Trombetas, and Tapajós river drainages, plus the Rupununi basin in Guyana. A…

Habitat

Inhabits sluggish tributaries, small rivers and swampy areas, particularly in areas with dense growth of aquatic vegetation or submerged woody structures and l…

Aquarium size

Base dimensions of at least 45 ∗ 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 displa…

Water conditions

Not written yet

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…

Behaviour and compatibility

Very peaceful but does not make an ideal community fish due to its small size and rather timid nature. In a community it's best kept with similarly-sized, peac…

Sexual dimorphism

Adult males possess a highly-modified, extended anal-fin, are more intensely-coloured, and usually slimmer than females.

Reproduction

Unreported.

Notes

This species is rare in the aquarium hobby and it most commonly arrives as bycatch among shipments of other fishes. Among congeners it's most similar to N. bif…

This species is rare in the aquarium hobby and it most commonly arrives as bycatch among shipments of other fishes.

Among congeners it's most similar to N. bifasciatus but can be distinguished by presence (vs. absence) of an adipose-fin.

Diagnostic characters include: presence of two dark lateral body stripes, one along midbody and the other, often less well-developed, in the upper portion of body; non-permanent noctural patterning of oblique blotches; adipose-fin always present; snout fits 1.1-1.3 times in eye diameter; total vertebrae 34-35; adult male with elongate anal-fin, reachingh caudal-fin when adpressed; 19 caudal-fin rays, 10 in upper and 9 in lower lobe.

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.

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My own experienceFor example, I've kept twelve in a planted 60 cm tank since March 2024.A website I sawFor example, an IUCN Red List assessment, a museum catalogue or a FishBase page.A paperFor example, Marshall et al. (2011), Water temperature differences in interfluvial palm swamp habitats of Paracheirodon axelrodi and P. simulans.A book, or something not onlineFor example, Tappin (2010), Rainbowfishes: their care and keeping in captivity.Something already on the pageFor example, the Behaviour and compatibility section already says this.

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References

4 on this profile

Name

Scientific name

Described by

Family

Common names

Photograph credits

Summary

Size and aquarium

Maximum size

Aquarium size

Water

Water conditions

Hardness

Conductivity

Behaviour

Temperament

Social needs

Community suitability

Where it lives

Countries, regions, rivers and lakes

Writing

Etymology

Distribution

Habitat

Aquarium size

Maintenance

Water conditions

Diet

Behaviour and compatibility

Sexual dimorphism

Reproduction

Notes

References

References