Edit Nannostomus rubrocaudatus

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Name

Scientific name

Nannostomus rubrocaudatus

Described by

Authority Zarske, Year 2009

Family

Lebiasinidae

Common names

Purple Pencilfish

Photograph credits

All 4 credited

Summary

The purple pencilfish, Nannostomus rubrocaudatus, is reportedly collected along the Marañón in Peru, between the Morona and Santiago rivers…

Size and aquarium

Maximum size

30mm, standard length

Aquarium size

Minimum length 90 cm, Minimum depth 30 cm, Water movement Low: still or sluggish water

Water

Water conditions

Temperature 24–28°C, pH 4–7

Hardness

1–5dGH

Conductivity

Not recorded

Behaviour

Temperament

Peaceful

Community suitability

Not for a community

Where it lives

Countries, regions, rivers and lakes

Peru, Amazon, Marañón

Writing

Etymology

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

Distribution

The type series was obtained from a commercial shipment of wild fishes from Peru into Germany. The enterprise which imported them later released a statement in…

Habitat

Unconfirmed. Related congeners inhabit sluggish tributaries, small rivers and swampy areas, particularly in areas with dense growth of aquatic vegetation or su…

Aquarium size

Base dimensions of at least 90 ∗ 30 cm or equivalent are necessary if you wish to keep a mixed-sex group since males can be particularly aggressive towards one…

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

Peaceful with other species but does not make an ideal community fish due to its small size and rather timid nature. Ideally it should be maintained alone or a…

Sexual dimorphism

Adult males are noticeably less stocky and far more colourful than females, plus they possess a modified anal-fin with the third to sixth rays being thickened.

Reproduction

Has been achieved in aquaria, albeit rarely, and in a densely-planted, mature aquarium it's possible that small numbers of fry may start to appear without inte…

Notes

Prior to description this species was traded as Nannostomus sp. 'purple', N. cf. marginatus 'red pencil II', or N. sp. 'coral red II'. It can be told apart fro…

Prior to description this species was traded as Nannostomus sp. 'purple', N. cf. marginatus 'red pencil II', or N. sp. 'coral red II'.

It can be told apart from similar species by the following combination of characters, adapted from Zarske (2009): pronounced sexual dimorphism with adult males exhibiting bright red-purple pigmentation between the central, upper, and lower (primary, secondary and tertiary) dark lateral stripes; all three dark lateral stripes strong and distinctive; central (primary) lateral stripe in males extending ventrally to posterior half of anal-fin base; anterior part of dorsal-fin in males red; adipose-fin absent; males with modified, thickened anal-fin rays; 2 teeth on each maxillary bone.

In live fish colour pattern is perhaps the most useful way to identify N. rubrocaudatus plus the closely-related N. marginatus and N. mortenthaleri.

N. marginatus is immediately distinguished from the other two by the fact it lacks red pigmentation on the body in males, but N. mortenthaleri and N. rubrocaudatus are more easily-confused.

Males of N. rubrocaudatus can be told apart from those of N. mortenthaleri by the fact that the red pigmentation in the rear half of the body is purplish and more uniform than in N. mortenthaleri which when not breeding only displays red colouration between the primary and secondary lateral stripes.

In N. rubrocaudatus the anterior portion of the dorsal-fin is red and the distal portion hyaline, and the ventral fins are reddish proximally, hyaline distally, while in N. mortenthaleri there is a white blotch at the anterior base of the dorsal-fin and the distal part of the fin is red, and the ventral and anal fins are more-or-less entirely red.

In females of N. rubrocaudatus the interspace between primary and secondary lateral stripes is silvery with a reddish stripe below the primary dark stripe in the rear of the body and a small red patch between the primary and tertiary stripes anterior to the anal-fin, while in N. mortenthaleri the entire area between primary and secondary stripes is reddish.

As in males the ventral and anal fins are reddish proximally and hyaline distally in N. rubrocaudatus, more-or-less uniformly reddish in N. mortenthaleri.

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 different colour pattern at night, in this case the entire colour pattern paling considerably and the dark lateral stripes disappearing.

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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References

5 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