Carnegiella marthae (MYERS, 1927) Blackwing Hatchetfish

Etymology

In 1909, C.H. Eigenmann created the genus Carnegiella for the species C. strigata, which was previously known as Gasteropelecus strigatus. The name “Carnegiella” was chosen in honor of Miss Margaret Carnegie and reflects the elegant nature of these fish.

Classification

Order: Characiformes
Family: Gasteropelecidae

Distribution

The type locality for this species is located in Caño de Quiribana near Caicara, Venezuela. However, it is believed that this species can be found throughout the upper Orinoco drainage in Venezuela and the rio Negro drainage in Amazonian Brazil, with occasional specimens being recorded from the rio Madeira, which is located downstream from the mouth of the Negro on the opposite bank. There have also been records of this species in Colombia, with at least one record from the Río Vichada and another from the Río Inírida, both of which are tributaries of the Orinoco.

Venezuela

Venezuela is a country located on the northern coast of South America, bordering the Caribbean Sea, Brazil, Colombia, and Guyana. It is home to a diverse population of over 28 million people, with a blend of indigenous, African, and European cultures contributing to the country’s rich cultural heritage. The country’s geography is characterized by its variety of landscapes, ranging from the Andean mountain range in the west to the vast plains of the Llanos in the east. The Amazon Rainforest also covers a significant portion of the southern part of the country. Venezuela’s climate varies by region, with tropical and subtropical climates dominating the landscape. Venezuela is known for its vast oil reserves, which have been a major source of income for the country’s economy since the 20th century. The oil industry has allowed Venezuela to become one of the wealthiest countries in South America, although this wealth has not always been equitably distributed among its citizens. Despite its wealth, Venezuela has been plagued by political instability and economic turmoil in recent years. A protracted political crisis that began in 2013 has resulted in the country’s current president, Nicolás Maduro, being widely regarded as illegitimate. The crisis has resulted in widespread shortages of basic goods, hyperinflation, and the emigration of millions of Venezuelans seeking better opportunities abroad. Despite these challenges, Venezuela is a country rich in cultural heritage and natural resources. Its diverse landscapes offer opportunities for adventure, including hiking, rafting, and exploring the Amazon rainforest. The country’s music, art, and cuisine are also highly regarded, with a mix of indigenous, African, and European influences contributing to their unique character. Venezuela’s history is also a fascinating one, with the country having been colonized by the Spanish in the 16th century. It was a key player in South America’s wars of independence, with Simón Bolívar leading the charge against Spanish colonial rule. The country has also been a hub for revolutionary movements in the region, with socialist ideologies taking root in the mid-20th century. In conclusion, Venezuela is a country with a complex and often tumultuous history. Despite its challenges, it remains a country of great cultural significance and natural beauty, with the potential for economic growth and stability. However, the path forward for Venezuela remains uncertain, and it will require significant political and economic reforms to overcome its current challenges and fully realize its potential.

Although it is possible that this species may have a more restricted distribution, research published by Piggott et al. (2011) suggests the existence of at least three species in the Rio Negro basin alone.

Carnegiella marthae (MYERS, 1927) Blackwing Hatchetfish

Habitat

It appears that the fish species, known as Carnegiella marthae, is adapted to living in blackwater environments. Specifically, it can be found in the rio Negro system, where it inhabits igapó and igarapé habitats. These habitats are characterized by thick, overhanging riparian vegetation, and substrates covered in fallen branches, tree roots, and leaf litter.

The water in these habitats is typically acidic, with a low carbonate hardness and conductivity. Additionally, the water is stained brownish due to the presence of humic substances that are released by decomposing organic matter. The rio Negro has a substantial floodplain, and during the annual wet season, the water level can rise by up to 15 meters.

During the period of inundation, small fishes like the Carnegiella marthae move upstream within the river’s tributaries and then laterally into the flooded forest itself to feed and reproduce. When the water level falls, they return to the tributaries. This behavior suggests that Carnegiella marthae is well-adapted to the seasonal fluctuations of the rio Negro’s floodplain.

In conclusion, Carnegiella marthae is a fish species that is adapted to living in blackwater environments. Its ability to move between different habitats during the wet season shows that it is well-adapted to the seasonal fluctuations of its environment.

Maximum Standard Length

The specimen that holds the official record for being the largest measures 28.1 mm in length.

Aquarium Size

It is recommended that the surface dimensions for keeping this species should be 60 * 30 cm or larger. This is because it is best to maintain this species in groups, as explained in the ‘Behaviour and Compatibility’ section.

Maintenance

It is recommended that this species be kept in a heavily-planted aquarium with a dark substrate, and patches of floating vegetation. They tend to spend most of their time at or towards the surface, and these plants provide them with the necessary shelter and hiding places.

In addition to plants, driftwood branches and dried leaf litter can also be added. These items will encourage the establishment of microbe colonies as decomposition occurs. Such microorganisms can provide a valuable secondary food source for fry, while the tannins and other chemicals released by the decaying leaves are also thought to be beneficial.

Water movement should be gentle to moderate. Also, it is important to ensure that the aquarium cover is tightly-fitted as this species may jump when startled. Overall, a well-planted and appropriately decorated aquarium is essential for the health and well-being of this species.

Water Conditions

Temperature: 20 – 28 °C
pH: 4.0 – 7.0
Hardness: 18 – 179 ppm

Diet

In its natural habitat, this species primarily feeds on terrestrial and aquatic invertebrates and other zooplankton that are found at or near the water surface. As for their diet in the aquarium, they will accept dried foods of a suitable size, but it is essential to offer them regular meals of small live and frozen fare such as Artemia nauplii, Daphnia, Moina, and grindal worm.

Small insects such as young crickets or Drosophila fruit flies are also suitable to use, although it is best to fill their stomachs by feeding them fish flakes or some kind of vegetable matter before offering them to the fish. Providing a varied diet is essential to maintain their health and promote their natural behavior.

Behaviour and Compatibility

This species is known to be very peaceful, but it may not be the best choice for a community tank due to its small size and timid nature. It is recommended to keep this fish with other peaceful characids and smaller catfish species such as callichthyids or loricariids. It can also be a great addition as a dither fish for Apistogramma spp. and other dwarf cichlids.

Because it is a gregarious animal, it is recommended to purchase as many as possible, ideally 10 or more, as they will exhibit more natural behavior and any aggression will be spread out among individuals. Additionally, keeping them in larger groups will make the fish bolder and less likely to be stressed.

Although this species is generally peaceful, it is important to note that individual fish may display territorial behavior towards others of the same species, particularly when breeding. If breeding is desired, it is best to keep a larger group in a well-planted aquarium with plenty of hiding places to disperse aggression.

Gregarious

Gregarious behavior refers to the tendency of animals to live in social groups, and is a characteristic commonly observed in a wide range of species, including mammals, birds, fish, insects, and even some reptiles. This behavior has evolved as a survival strategy in many species, as living in a group can provide several benefits such as protection against predators, improved access to food and mating partners, and increased ability to defend territory.

In the animal kingdom, there are various forms of gregarious behavior, ranging from small groups to large colonies. For instance, some birds form small flocks of just a few individuals, while others, such as geese or ducks, can form large groups of hundreds or even thousands of individuals. In the marine environment, fish such as anchovies, sardines, and herring form massive schools that can number in the millions, providing them with protection from predators and increasing their chances of finding food.

One of the primary benefits of gregarious behavior is improved protection against predators. Living in a group can provide a “safety in numbers” effect, making it more difficult for predators to target and capture an individual. Animals can also work together to defend their territory, with some species engaging in cooperative hunting or mobbing behavior to repel predators.

Another significant benefit of living in groups is improved access to food and mating partners. For example, social insects such as bees, ants, and termites can work together to find and gather food for the colony. Social groups can also help increase an individual’s chance of finding a mate, with many species engaging in courtship behaviors or displays within the group.

Despite the advantages of gregarious behavior, there are also some drawbacks to living in a group. One potential issue is competition for resources such as food, water, and nesting sites. This competition can be especially intense in large groups, leading to aggression and fighting between individuals.

Overall, gregarious behavior is a complex and fascinating aspect of animal behavior, with numerous benefits and drawbacks. Understanding the factors that drive this behavior and its effects on individual animals and populations can provide valuable insights into the natural world and how species have adapted to survive and thrive in their environments.

Sexual Dimorphism

It is worth noting that some individuals of this species may exhibit a larger and more rounded body shape, which is likely to be characteristic of adult females.

Reproduction

Unrecorded.

Notes

The Gasteropelecidae family is distinctive from other Characiformes by its unique characteristics, including a longitudinally corrugated frontal bone with a strong longitudinal ridge, a fused posttemporal and supracleithrum bone, small pelvic fins and associated bones, and a greatly expanded coracoids that fuse to a single fan-shaped and corrugated median bone. The family also has a lateral line that extends ventroposteriorly to approach the anal-fin insertion, 0-2 or 3 scales behind the head, and one or very few scales on the caudal-fin base. Larger species have an adipose fin, while smaller species lack it. Currently, there are three valid genera of Gasteropelecidae, with Carnegiella being the most diverse, consisting of four small species that lack an adipose fin.

The species in Carnegiella show geographic variations based on their locality, with the marble hatchetfish C. strigata being a prime example. At various times, it has had five recognized species. Gery (1977) noted that the species in this genus are polytipic, meaning that there are two or more distinct populations within each species. He suggested that the Orinoco and Negro system fish of the C. marthae group should be considered a subspecies, C. marthae marthae, and the species C. schereri from the Peruvian Amazon as the subspecies C. marthae schereri. Recent research by Piggott et al. (2011) identified three cryptic species in the Negro floodplain streams.

Due to their unique body shape, gasteropelecids are commonly known as freshwater hatchetfishes. Their bodies are heavily-keeled, which is due to an enlarged, heavily-muscled pectoral girdle, giving them a shape resembling the head of a hatchet.

It is sometimes said that hatchetfish can fly above the water surface by beating their pectoral fins, but this is not true. Wiest’s (1995) research using high-speed video photography disproved this myth. He found that the pectoral fins are used to leave the water but not while the fish is in the air. Instead, hatchetfish are capable of powerful jumps, which are actually a modified threat response used in extreme circumstances, much like other fishes.

Interestingly, Wiest also discovered that hatchetfish can only jump once or twice before needing a rest due to the amount of energy required to work their massive pectoral girdle muscles. When fatigued, they revert to a typical diving response.

Furthermore, anecdotal evidence from fish collectors and ichthyologists working in the field suggests that hatchetfish rarely jump and tend not to do so in aquariums, even when chased with a net. However, during darkness, they may jump, and leaving the aquarium cover slightly open can result in hatchetfish on the floor by morning.

The order Characiformes is known for its vast diversity of freshwater fish species, with almost 2000 valid species spread across 19 families. However, this taxonomic and morphological diversity has presented a challenge for researchers attempting to determine genetic relationships between genera, with many remaining incertae sedis. In many cases, exhaustive individual studies have been necessary to address these issues.

Nonetheless, modern molecular phylogenetic techniques have allowed researchers to make some progress in this area. For instance, Javonillo et al. (2010) and Oliveira et al. (2011) published research papers that offered some hypotheses about genetic relationships within the order. The former paper suggested that the family Gasteropelecidae forms a monophyletic clade nested within the family Characidae. Meanwhile, the latter paper expanded on this hypothesis and proposed that within the family, Carnegiella is the sister group of Gasteropelecus, with Thoracocharax sister to that clade.

Additionally, the authors suggested that Gasteropelecidae is most closely related to their expanded Bryconidae, which includes the genera Brycon, Henochilus, and Salminus. Other researchers, such as Oliveira et al. (2011), have concluded that the family Erythrinidae is also closely related to this grouping, with Hepsetidae and Alestidae being more distant.

References

Myers, G. S., 1927 – Bulletin of the Museum of Comparative Zoology 68(3): 107-135
Descriptions of new South American fresh-water fishes collected by Dr. Carl Ternetz.
Gery, Jacques, 1977 – TFH Publications Inc.
Characoids of the World
Javonillo, R., L. R. Malabarba, S. H. Weitzman and J. R. Burns, 2010 – Molecular Phylogenetics and Evolution 54(2): 498-511
Relationships among major lineages of characid fishes (Teleostei: Ostariophysi: Characiformes), based on molecular sequence data.
Oliveira, O., G. S Avelino, K. T. Abe, T. C Mariguela, R.C Benine, G. Ortí, R. P. Vari and R. M. Corrêa e Castro, 2011 – BMC Evolutionary Biology 11: 275
Phylogenetic relationships within the speciose family Characidae (Teleostei: Ostariophysi: Characiformes) based on multilocus analysis and extensive ingroup sampling.
Piggott, M. P., N. L. Chao and L. B. Beheregaray, 2011 – Biological Journal of the Linnean Society 102(2): 391-403
Three fishes in one: cryptic species in an Amazonian floodplain forest specialist.
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.
Weitzman, S. H. and L. Palmer, 1996 – Tropical Fish Hobbyist 45(1): 195-206
Do freshwater hatchetfishes really fly?
Wiest, F. C., 1995 – Journal of Zoology 236(4): 571-592
The specialized locomotory apparatus of the freshwater hatchetfish family Gasteropelecidae