Edit Petitella georgiae

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Name

Scientific name

Petitella georgiae

Described by

Not recorded

Family

Characidae

Common names

False Rummy-nose

Photograph credits

All 1 credited

Summary

The false rummy-nose, Petitella georgiae, is a small tetra from the Rio Purus in Peru and Brazil and the Rio Negro and Rio Madeira in Brazi…

Size and aquarium

Maximum size

50mm, standard length

Aquarium size

Not recorded

Water

Water conditions

Temperature 22–26°C, pH 5.5–7

Hardness

1–12dGH

Conductivity

Not recorded

Behaviour

Temperament

Peaceful

Community suitability

Not recorded

Where it lives

Countries, regions, rivers and lakes

Brazil, Peru, Negro

Writing

Etymology

Petitella, from the French –ella, a diminutive connoting endearment; in honor of zoologist-anatomist Georges Petit (1892-1973). The species epithet georgiae ho…

Distribution

Native to the Rio Purus in Peru and Brazil, as well as the Rio Negro and Rio Madeira in Brazil.

Habitat

Mainly found in clear water tributaries and small rivers.

Aquarium size

This is a species that should be maintained in groups numbering 10 or preferably more, and its active swimming nature requires a tank length of 36 inches/90 cm…

Maintenance

Prefers dim lighting and will show its colours better over a dark substrate. It looks superb in a heavily planted setup decorated with pieces of bogwood and tw…

Water conditions

Temperature: 22 – 26 °C pH: 5.5 to 7.0 Hardness: 1 to 12°H

Diet

Any food offered must be small enough for its tiny mouth. It will take dried foods, but these should be of a small grade or ground down before being added to t…

Behaviour and compatibility

It's a very peaceful species that won't compete well with boisterous or much larger tankmates. Ideally keep it with other South American species, such as other…

Sexual dimorphism

Mature females are noticeably rounder in the body than males.

Reproduction

Can be quite tricky to breed. You'll need to set up a dedicated tank if you want to raise decent numbers of fry. Something around 18" x 10" x 10" in size is fi…

Notes

This is one of three species commonly sold under the name "rummy-nose tetra". The commonest of these is the firehead tetra, Hemigrammus bleheri, whilst the "tr…

This is one of three species commonly sold under the name "rummy-nose tetra". The commonest of these is the firehead tetra, Hemigrammus bleheri, whilst the "true" rummy-nose is Hemigrammus rhodostomus. All three are very similar in appearance, but can be distinguished by several factors.

The first is by the extent to which the red colouration on the head of the fish extends into the body. H. bleheri is the only one of the 3 in which the red extends beyond the gill covers. The amount of red colouration on the other 2 species is similar, although it tends to be a little lighter in tone in P. georgiae. This factor alone cannot be used to positively identify a species, though, as if the fish are not in good condition the red colour can fade considerably. This is particularly true for H. bleheri.

The second thing we can examine is the caudal peduncle of the fish. All the species possess a dark blotch at the top of the caudal peduncle, but only the Hemigrammus possess one at the bottom. If the bottom blotch is absent, you're probably looking at a Petitella.

The third factor to look at is the line extending laterally from the central caudal fin band into the body of the fish. This is quite broad in P. georgiae, narrower in H. rhodostomus
and almost non-existent in H. bleheri. By a combination of these factors, you should be able to identify your fish. The species differ in a couple of other ways, too, such as the patterning of the caudal fin and at the base of the anal fin. Obviously they can also be distinguished by fin ray and scale counts, but the methods described here should suffice for most hobbyists.

Bittencourt, et al. (2020) proposed the transfer of the rummynose tetras Hemigrammus rhodostomus and H. bleheri to the genus Petitella on the basis of molecular and morphological data. Petitella is defined as follows:

The genus Petitella is readily distinguished from all remaining characid genera by the possession of a distinctively bright red head, the presence of a black horizontal bar that extends from the end of the caudal peduncle to the middle rays of the caudal-fin, and the presence of an oblique black bar in each caudal-fin lobe, separated by white colored bands. Contact between frontals anterior to frontal fontanel present; posterodorsal margin of ethmoid cartilage and lateral ethmoids distant from lateral ethmoids; 17 or fewer branched anal-fin rays; only one or two anal-fin hooks on each ray of adult males; the presence of parallel longitudinal ridges on the posterior field of scales; scales covering one-third of the length of caudal-fin lobes; coloration of the head distinctively red, especially the snout.

The phylogenetic reconstruction also confirms Petitella georgiae as a sister-group of Petitella bleheri. The striking p-distance divergence (9.1%) between the Peruvian P. georgiae and our samples from the Purus River indicates the possibility of Petitella georgiae being a species complex. The monophyly of P. bleheri and P. georgiae was highly supported in our analyses — the first time Petitella georgiae was included in any molecular phylogeny — as well as by the morphological data of Mirande (2019), who reported seven morphological synapomorphies supporting the sister-taxon relationship between these two species.

Petitella georgiae is distinguished from its congeners by a long and wide maxillary (vs. very short and round in P. bleheri, and short in P. rhodostomus); single row of premaxillary teeth (vs. two in P. bleheri and P. rhodostomus); dentary with 9–11 teeth with 5 cuspids (vs. 6, with 6 or 7 cuspids, followed by 1 or 2 tricuspidate ones in P. bleheri, and 5–6 with 5 cuspids, usually followed by 4 conical teeth in P. rhodostomus); absence of black spot on lower posterior border of caudal peduncle (vs. present in P. bleheri and P. rhodostomus).

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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

3 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