Taxonomy & naming
Charax notulatus was described by Carlos Alberto Santos de Lucena in 1987, with the type locality recorded as a small caño (creek) near the mouth of Caño Soroco on the Orinoco River in Delta Amacuro state, Venezuela. The valid name is recorded in Eschmeyer's Catalog of Fishes as Charax notulatus Lucena, 1987. A subsequent comprehensive taxonomic review of the genus by Menezes and Lucena (2014), published in Neotropical Ichthyology (SciELO), provided a redescription of the species alongside other Charax members and documented superficial neuromasts — a feature noted in some species of the genus.
Charax is placed in the subfamily Characinae of the family Characidae and belongs to a loose assemblage of South American characterins sometimes called glass tetras or dog tetras on account of their semi-transparent bodies and pronounced canine-like teeth. The genus occurs across much of tropical South America east of the Andes. C. notulatus is distinguished from congeners on the basis of meristic and morphometric characters established in the original description and revisited in the 2014 revision.
Morphology
Like other members of the genus, Charax notulatus is a slender to moderately compressed characin with a markedly large, upturned mouth equipped with canine-like teeth suited to seizing small prey. The body is semi-translucent in life, as is typical of Charax, with internal organs visible through the skin of the abdomen — a characteristic responsible for the informal name 'glass tetra' applied to the genus as a whole.
The specific epithet notulatus (from Latin, meaning 'marked with small spots') suggests a spotted or speckled pigmentation pattern, though precise colour descriptions for live specimens are sparse in the published literature. Detailed meristic counts are established in the original 1987 description; the 2014 genus revision by Menezes and Lucena provides the most current diagnostic framework. Maximum standard length is not specified in the available literature for this species.
Habitat
Charax notulatus is known from the lower Orinoco River basin of Venezuela, with the type series collected from a small creek near the mouth of Caño Soroco in Delta Amacuro state. FishBase records the species as a benthopelagic, tropical freshwater fish, occupying the water column rather than being strictly bottom-associated.
A checklist of the ichthyofauna of the Rio Negro basin in the Brazilian Amazon (Beltrão et al.) lists a specimen (INPA 7884) attributable to this species, suggesting the range may extend into adjacent drainages — the lower Orinoco and upper Rio Negro systems share faunal affinities through historical connections and the Casiquiare canal. The Orinoco delta region is characterised by blackwater and whitewater habitats, warm temperatures, and variable water chemistry across its many caños and floodplain lakes.
Feeding
Members of the genus Charax are predominantly piscivorous and invertivore predators, using their large, toothed mouths to seize prey. Their body form — slender, fast, with an upturned jaw — is adapted for ambush or pursuit feeding on smaller fish, aquatic insects, and crustaceans. Juveniles likely shift diet as they grow, relying more on invertebrates before graduating to small fish.
No specific dietary studies are available for Charax notulatus in the wild. In the aquarium, members of this genus are typically offered live or frozen small fish, earthworms, and invertebrates, though individuals can sometimes be trained to accept suitably sized pellets or pieces of fresh seafood. Given the predatory nature of the genus, tankmates small enough to be consumed are at risk.
Mating
No published observations of courtship or mating behaviour are available for Charax notulatus specifically. Based on the reproductive biology of closely related characins and the broader Characidae, the species is presumed to be an egg scatterer with no parental care. Males of predatory characins often pursue females in open water, with brief parallel-swimming or chasing bouts preceding egg release.
Charax species are not commonly bred in captivity, and detailed courtship descriptions are absent from the hobby literature. Spawning is expected to follow the general characid pattern of adhesive or semi-adhesive eggs deposited among fine-leaved aquatic vegetation or substrate, with both sexes scattering gametes freely and departing immediately after.
Breeding
No successful captive breeding accounts have been recorded in the available literature for Charax notulatus. The reproductive biology of the genus as a whole is poorly documented in aquarium practice, as most Charax species are collected sporadically and rarely maintained in dedicated breeding set-ups.
By analogy with other small to mid-sized Characinae, breeding would likely involve conditioning adults on protein-rich live or frozen foods, a separate spawning tank with fine-leaved plants or mops to collect eggs, and the removal of adults after spawning to prevent egg predation. Incubation and larval development timings are unknown for this species. Data on this species' reproduction remain sparse.
In the aquarium
Charax notulatus is rarely encountered in the aquarium trade and is not an established hobby fish. The genus Charax in general attracts a niche following among enthusiasts interested in predatory characins, but most Charax species are kept as curiosities rather than community fish. Their predatory nature and need for protein-rich live or frozen foods make them less suitable for mixed community tanks containing smaller species.
For those who do maintain Charax, warm, well-filtered water in the tropical range appropriate to Orinoco drainage species is recommended, with subdued lighting and some cover to reduce stress. Given the semi-translucent body form and active hunting behaviour, a longer tank with open swimming space and a secure lid — Charax can be jumpy — suits them best. Tankmates should be of similar size and temperament. Published care information specific to C. notulatus is essentially absent; hobbyists keeping this species should consult the broader Charax genus literature and the Characinae keeping community.
Conservation
Charax notulatus has not been assessed by the IUCN Red List, and no formal conservation status has been assigned to the species. Its known distribution encompasses the lower Orinoco basin of Venezuela, with a possible record from the Rio Negro basin of Brazil, suggesting it may not be narrowly endemic — but the evidence base is thin.
The lower Orinoco delta and adjacent Amazonian drainages face ongoing pressures from land conversion, artisanal mining, and fisheries. Without a dedicated population survey or assessment, the species' actual abundance and vulnerability remain unknown. Given its obscurity in both scientific and aquarium literature, C. notulatus is a candidate for future survey work in Venezuelan and Brazilian lowland ichthyological inventories.