Nannostomus digrammus (FOWLER, 1913) - Twostripe Pencilfish

Synonyms

Poeciliobrycon digrammus Fowler, 1913

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

This fish is indigenous to the central Amazon basin and has been documented in the Madeira, Branco, Trombetas, and Tapajós river systems as well as the Rupununi basin in Guyana.

Guyana

Guyana is a country located on the northeastern coast of South America. It shares borders with Suriname to the east, Brazil to the south, and Venezuela to the west. The country has a population of approximately 800,000 people and covers an area of 215,000 square kilometers. Guyana is known for its diverse culture, vibrant music scene, and natural resources, particularly its rich deposits of bauxite, gold, and diamonds.

History

The history of Guyana can be traced back to the indigenous Amerindian tribes who inhabited the region long before the arrival of Europeans. The Arawak and Carib tribes were the two most prominent groups in the region, and they lived peacefully until the arrival of European colonizers. The first Europeans to arrive in Guyana were the Dutch, who established a trading post in the region in the 16th century.

Over time, Guyana changed hands several times, with the Dutch, French, and British all having a stake in the region at various points. In 1815, the British gained full control of the region, and Guyana became a British colony. The country gained independence in 1966, and today it is a member of the Commonwealth of Nations.

Culture

Guyana is a melting pot of different cultures, with its population consisting of people from various ethnic backgrounds. The three main ethnic groups in the country are Indo-Guyanese, Afro-Guyanese, and Amerindian. The Indo-Guyanese population is descended from Indian indentured laborers who were brought to the region by the British in the 19th century, while the Afro-Guyanese population is descended from African slaves who were brought to the region by the Dutch.

The Amerindian population is made up of the indigenous tribes that inhabited the region long before the arrival of Europeans. Guyana is known for its vibrant music scene, which draws inspiration from the country’s diverse cultural heritage. Popular music genres in Guyana include reggae, calypso, and chutney music.

Economy

Guyana is one of the poorest countries in South America, with a GDP per capita of approximately $4,000. However, the country has enormous natural resources, particularly in the mining sector. The country is the world’s largest producer of bauxite and has significant deposits of gold and diamonds.

In recent years, Guyana has also become an important player in the oil and gas sector. In 2015, ExxonMobil discovered a significant oil deposit off the coast of Guyana, and since then, several other companies have made similar discoveries. The country is expected to become a major oil producer in the coming years, which could significantly boost its economy.

Tourism

Guyana is a popular destination for eco-tourism, thanks to its rich biodiversity and stunning natural scenery. The country is home to a wide variety of wildlife, including jaguars, giant river otters, and several species of monkeys.

One of the country’s most popular tourist destinations is Kaieteur Falls, a breathtaking waterfall that is over five times taller than Niagara Falls. The waterfall is located in Kaieteur National Park, which is also home to several other natural wonders, including the Potaro River and Mount Roraima.

Conclusion

Guyana is a country with a rich cultural heritage and abundant natural resources. Although it faces many challenges, particularly in terms of poverty and inequality, the country has enormous potential, particularly in the mining and oil sectors. As the country continues to develop, it is likely to become an increasingly important player in the global economy.

Despite not being formally recognized as part of the Amazon basin due to its connection to the Rio Essequibo, the Rio Takutu, a tributary of the upper Rio Branco, links the former during the annual wet season. The type locality, as designated by Fowler, is the Rio Madeira, located around 200 miles east of W. Long. 62°20′ in Brazil. More recently, fish that closely resemble the aforementioned species, but possess an additional thin dark stripe in the lower part of their bodies (refer to ‘Notes’), have been exported from Colombia and are thought to occur in Peru as well.

Habitat

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

Maximum Standard Length

25 – 30 mm.

Aquarium Size

To ensure the adequate space for your aquatic pets, it is recommended that the base dimensions of the aquarium should be at least 45 x 30 cm or equivalent. Additionally, selecting an appropriate filter is crucial to maintaining a healthy environment for your aquatic pets. It is advised to choose a filter that has a water flow rate of 4-5 times the volume of your aquarium. For instance, if your aquarium has a volume of 41 litres, we recommend a filter that can be found here. Alternatively, you can also explore other highly recommended aquarium filters by customers in your area, which can be found here.

Nannostomus digrammus (FOWLER, 1913) -Twostripe Pencilfish — Nannostomus digrammus (FOWLER, 1913) –
Twostripe Pencilfish

Maintenance

For optimal health and well-being, it is recommended to house this species in a heavily planted aquarium with a dark substrate. The natural behavior of the fish can be observed better in such a setup, as the plants create broken lines of sight and reduce their skittishness. Floating plants, driftwood branches, and dried leaf litter can also be added to the aquarium. The leaf litter, in particular, helps establish microbe colonies as decomposition occurs, providing a valuable secondary food source for fry. Moreover, the tannins and other chemicals released by the decaying leaves are thought to have beneficial effects on the fish’s health. To maintain a gentle flow of water, an air-powered sponge-style filter unit should suffice in most cases.

Water Conditions

Temperature: 22 – 28 °C
pH: 5.0 – 7.0
Hardness: 18 – 179 ppm

Diet

In its natural habitat, this species is considered a micropredator that feeds on small invertebrates and zooplankton. In an aquarium setting, the fish can be fed dried foods of appropriate size but should also be given small portions of live or frozen food such as Artemia nauplii, Moina, and grindal worm on a daily basis. To ensure a well-rounded diet, high-quality live, frozen, and dry food options can be explored by clicking on the following links for Artemia and here for other recommended food options.

Behaviour and Compatibility

Despite being a peaceful species, it is not recommended to keep this fish in a community tank due to its small size and timid nature. Instead, it is best to keep them with similarly-sized, peaceful characids and smaller callichthyid or loricariid catfishes. Additionally, this fish can serve as an excellent 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 actively predate fry.

Although naturally gregarious, this species is a shoaling rather than schooling fish, with rival males often sparring during daylight hours. Within a group, it is not uncommon to observe nipped fins, although this behavior usually does not extend to tank mates. It is advisable to purchase as many individuals as possible, ideally 10 or more, as when kept in larger groups, any aggression is spread between individuals, and the fish exhibit bolder and more natural behavior.

Sexual Dimorphism

In this species, adult males have a significantly modified and elongated anal fin. Additionally, they are typically more brightly colored and have a slimmer body shape compared to females.

Reproduction

Unreported.

Notes

With nearly 2000 valid species distributed among 19 families, the order Characiformes is one of the most diverse groups of freshwater fishes. However, resolving genetic relationships between many of the genera has been challenging. Molecular phylogenetic techniques have provided some progress, as seen in a 2005 study by Calcagnotto et al., which revealed some interesting hypotheses. According to their findings, Lebiasinidae, along with the families Ctenoluciidae and Hepsetidae, form a trans-Atlantic, monophyletic clade. This clade is further a sister group to Alestidae. Other studies, such as Oliveira et al. (2011), suggest that the family Erythrinidae is also closely related to this group, with Hepsetidae and Alestidae being more distant. All lebiasinid genera share 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. Males of the majority of species possess an enlarged or otherwise well-developed anal fin, which is used in courtship and spawning. The frontal/parietal fontanelle is absent, and the cheek is 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. Some species have an adipose fin, while others do not, and the anal fin has a relatively short base of 13 scales or less

References

Fowler, H. W., 1913 – Proceedings of the Academy of Natural Sciences of Philadelphia 65: 517-179
Fishes from the Madeira River, Brazil.
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.
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.
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).

Nannostomus digrammus (FOWLER, 1913) – Twostripe Pencilfish