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Roberts Tetra

Scientific Name: Hyphessobrycon bentosi
Family: Characidae, Hemigrammus Clade

About the Roberts Tetra

Species Type: Freshwater Fish
Category: Characins

Care Level: Easy. Does well in a slightly more narrow range of water parameters and shouldn't be used to cycle an aquarium. Will eat most prepared foods. May have some specific care requirements in terms of particular water parameters, social behaviors, food items etc.

Origin: Distributed widely along the main course of the Rio Amazonas in Brazil and into Peru as far as Iquitos. Inhabits slow-moving blackwater igarapes and ponds, sluggish tributaries in forested areas, found among marginal vegetation and submerged branches.

Compatibility/Temperament: Very peaceful tetra recommended for a community tank of other peaceful fish like tetras, pencilfish, hatchetfish, small catfish and loaches, rasbora; suitable for discus and angelfish. This fish must be kept in groups, minimum 6, and remains in the lower half of the aquarium. It readily mixes in with the other related species in the "rosy tetra clade" of Hyphessobrycon, forming groups that may include any of the species.

Description

This is one of the most beautiful species in the rosy tetra clade; the overall body red is deeper than on the other species, especially when displaying and spawning, but only if maintained in an aquarium with a dark substrate and subdued lighting.

The rosy tetra clade of some 30 species within the genus Hyphessobrycon share several traits in colour and pattern. All species are somewhat disk-shaped and share the "flag" signal, being a very conspicuous black spot on the dorsal fin, usually underlined by a white or sometimes yellow zone and tipped with white depending upon species. They also share a darkened humeral or shoulder patch immediately posterior of the gill covers. The underlining white or yellow zone on the dorsal fin is absent in the subject species. The humeral spot is sometimes pale, usually due to the fish being maintained over a light-coloured substrate.

Sex differentiation is easy with this species; males have an elongated black dorsal fin that drapes down past the adipose fin over the caudal peduncle, while females have a small dorsal with a more prominent white upper tip and are rounder in the body. The white tips of the ventral and anal fins are absent in this species.

Keeping an even ratio of males and females will provide for continual displays by the males with fully extended dorsals, much like the closely-related Black Phantom Tetra and Rosy Tetra. Spawning will occur with subdued light, very soft (< 3 dGH) and acidic (pH below 6.0) water.

In aquaria containing two or more species in the rosy tetra clade, the various species regularly intermingle, and some authors have noted that they may cross-breed. All of them remain in the lower half of the aquarium, interacting socially among plants and wood. With a dark substrate and subdued light, these fish will also exhibit much more intense colouration and interactive behaviours.

The species was originally thought to be a hybrid of other bentosi-group species, but Gery opinioned that it is a distinct species that subsequently was sometimes seen as "H. robertsi." Weitzman & Palmer (1997) identified this fish as the true H. bentosi, and Lima & Malabara in Reis et al. (2003) established H. robertsi as a synonym of H. bentosi [Durban 1908]. H. rosaceus [Durbin 1909] was established by Weitzman & Palmer (1997) as a distinct species from H. bentosi and confirmed by Lima & Malabara in Reis et al. (2003).

The genus Hyphessobrycon--the name from the Greek "hyphesson" [believed to mean "slightly smaller"] and "brycon" [=to bite]--was erected by C.H. Durbin in 1908 and presently contains more than 100 valid species. The classification is deemed incertae sedis [Latin, "of uncertain placement"]. It was formerly considered within the Subfamily Tetragonopterinae, but Javonillo et.al. (2010) suggest that this subfamily should be restricted to species within the genus Tetragonopterus since they do not share physiological characteristics with species in other genera such as Hyphessobrycon.

Authors that have recently studied the systematics of the genus Hyphessobrycon have unanimously pointed out that the group is not well defined and its monophyly is yet uncertain. [A monophyletic genus is one wherein the species share a common ancestor, thus linking them together physiologically.] Mirande (2009) for example has proposed several revisions to the Family Characidae based upon phylogenetic diagnosis. Some genera have been moved to a new Subfamily, while others are now (temporarily) assigned to a specific clade within the Family pending further study. The recognition of groups of species [clades] within Hyphessobrycon is based primarily on similarities of color patterns; an hypothesis of its intra-relationships is currently unavailable, except for the rosy tetra clade proposed as monophyletic by Weitzman & Palmer (1997).

Hyphessobrycon has until recently been differentiated from Hemigrammus solely on the basis of the fish in Hemigrammus possessing a scaled caudal fin; this however is now known to be unreliable, since it occurs in intermediate conditions (de Lucina, 2003).

References:

de Lucena, Carlos Alberto Santos (2003), "A new characid fish, Hyphessobrycon scutulatus, from the Rio Teles Pires drainage, upper Rio Tapajos system (Ostariophysi: Characiformes: Characidae)," Neotropical Ichthyology 1 (2), pp. 93-96.

Javonillo, Robert, Luiz R. Malabarba, Stanley H. Weitzman and John R. Burns (2010), "Relationships among major lineages of characid fishes (Teleostei: Ostariophysi: Characiformes), based on molecular sequence data," Molecular Phylogenetics and Evolution, Vol. 54, No. 2 (February 2010).

Mirande, J. Marcos (2009), "Weighted parsimony phylogeny of the family Characidae (Teleostei: Characiformes)," Cladistics, Vol. 25, No. 6 (July 2009).

Reis, R.E., Sven O. Kullander & C.J. Ferraris Jr. (2003), "Check list of the Freshwater Fishes of South and Central America."

Weitzman, Stanley H. & Lisa Palmer (1997), "A new species of Hyphessobrycon (Teleostei: Characidae) from the Neblina region of Venezuela and Brazil, with comments on the putative 'rosy tetra clade'," Ichthyological Exploration of Freshwaters volume 7 (no. 3), pp. 209-242.

Roberts Tetra Diet

Primarily carnivorous, will readily accept most prepared foods, including flake and frozen bloodworms and daphnia.

Size

Grows to 2 inches.

Minimum Tank Suggestion

24 inches in length

Ideal water parameters for Roberts Tetra

Soft (hardness below 10 dGH) and acidic (pH below 7.0) water, temperature 23-28C/73-82F. A heavily-planted tank with diffused light and a dark substrate suits this species admirably.

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