A breeding pair of the colorful Rotkeil Severum. Although taxonomical studies are required, in my opinion the Rotkeil Severum should be regarded as a natural colour form of Heros efasciatus as they share many morphological similarities. Photo by A Wood.

Taxonomy and systematics

For almost 80 years, following Regan’s erection of the genus Cichlasoma in 1905, the genus Heros, which was first described by Heckel (1840), was considered to be part of this larger catch-all Cichlasoma genus and the name Cichlasoma severum was applied. Following Kullander’s revision of the Cichlasoma genus in 1983, the earlier genus name of Heros was revived and following his additional work in 1986 further species were also revived within the genus Heros, which now includes Heros spurius Heckel, 1840, Heros modestus Heckel, 1840, Heros corypaheus Heckel, 1840, Heros severus Heckel, 1840, Heros efasciatus Heckel, 1840 and Heros notatus (Jardine, 1843). A number of other variants have subsequently been identified, however their status as potential new species requires confirmation.

When you consider where the genus Heros fits into the family Cichlidae, then a review of scientific literature would demonstrate links between the Severum family and Angelfish (Pterophyllum spp.), Festive Cichlids (Mesonauta spp.) and even closer links with Discus (Symphysodon spp.) when comparing their respective internal organ arrangements.

Now, before going on to relate my experience with the topic of this article, Heros severus, I would like to comment on the other (currently) described species as I believe there is an enormous amount of confusion surrounding this group of cichlids:

The Río Guaporé Heros. Heckel, 1840 described three species from the upper Madeira catchment area (the Guaporé and Mamoré Beni river systems): Heros coryphaeus, H. modestus, and H. spurius. The systematic and taxonomic status of these Río Guaporé Heros is at present uncertain. Reis et al. (2003 (CLOFFSCA)) regard H. coryphaeus and H. modestus as junior synonyms of H. spurius and the latter as a valid species. Other authors (e.g. Stawikowski & Werner, 1998) have suggested all three may be synonyms of H. efasciatus. However, owing to a number of natural barriers the upper Madeira catchment area is known to have its own fish fauna and hence one or more of the three may well be valid.

Heros efasciatus Heckel, 1840 (one of the more common synonyms (still incorrectly used today) is H. appendiculatus) can be found in the Río Xingu and along the entire length of the Amazon River and Río Solimoes. This is probably the most commonly encountered member of the Severum family and should be considered as being the ancestor of the domestic green and gold colour strains of Severum found in our aquatic outlets. I would also consider the Rotkeil Severum to be a natural colour form of Heros efasciatus, this form is found in the Nanay-region of Peru, north-west of Iquitos (not far from the collecting-sites of Coral Red Pencilfish, Nannostomus mortenthaleri) in clear and black waters and first appeared in Germany in the year 2000 (Werner, 2007).

Heros notatus (Jardine, 1843) can be found in the middle Río Negro. Body patterning and brood care coloration compare with those shown by H. efasciatus and is also shared with H. sp. ‘Guyana’ (which can be found in the Essequibo River in Guyana). It is therefore possible that the distribution of H. notatus extends along the Río Negro, Río Branco and the Rupununi savanna, eventually joining the Essequibo River; it is also possible that H. notatus and H. sp. ‘Guyana’ are synonymous with H. efasciatus. As with all of these suppositions, careful taxonomical study is required to confirm the true identity of these (currently) separate species.

Specific traits

The type species of the genus Heros is Heros severus Heckel, 1840, as laid down by Jordan and Gilbert (1882). Members of the genus are high-sided and strongly compressed laterally, with a narrow neck and flattened chest in frontal view, and the eyes are set relatively far back on the head. Juveniles exhibit 8 clearly defined vertical bands which, as the fish matures, vary in intensity of coloration. When compared with the other members of the Heros genus, Heros severus has a slimmer body, a smaller mouth, narrower lips, and a more pointed face, and displays a broad blue grey stripe on the lower jaw. In adults only the seventh vertical band remains strongly visible at all times and the black coloration of this band may bleed into the dorsal fin but never the anal fin (a key identifier, with the other known members of the Heros genus the black colour of the seventh band bleeds into both the dorsal and anal fins). The remaining vertical bands may either fade or be visible depending on the mood of the fish in question.

Currently, Heros severus is the only described mouth brooding species within the Heros genus. All members of the genus prefer to lay their eggs on vertical surfaces, often choosing wood/roots or stones set into the river bank for this purpose. Here however the similarity ends, while Heros severus will mouth brood the wrigglers and fry, with other members of the genus the wrigglers and very young fry are housed in recesses found in the wood/roots or between stones set into the river bank. Only occasionally will pits be dug in the substrate to accommodate the wrigglers and fry.

Heros severus should be regarded as a bi-parental larvophilous mouth-brooding species, that is, eggs are attached to a suitable spawning site and only once they have hatched will both parents start to mouth brood the wrigglers.

Sexual dimorphism

In both sexes the body is a dull grey green with shades of brown coloration and varying degrees of red pigmentation over the flanks of the fish. This red pigmentation becomes stronger on the chest and intensifies as it leads up to the throat area (the bottom lip may also take on the red coloration). Males possess longer extensions to their dorsal and anal fins when compared with the female. I have found that the most reliable method of determining the sex of these fish is the series of dots displayed on the lower part of the gill cover by the male; these are either much reduced in number or not visible at all in female fish.

Distribution

The type locality is recorded as Marabitanas on the upper Río Negro (Brazil). Within Brazil the distribution of Heros severus extends over the upper Río Negro and the upper and middle Río Orinoco. Collection sites located in Venezuela and Colombia include Río Arauca, Río Cunaviche, Río Caura, Río Vichada (where they are locally known as the ‘false discus’) and the Río Casiquiare. H. severus have also been captured in the Río Guárico, a northern tributary of the middle Orinoco, the easternmost known collection location so far found.

Heros severus male (above) and female (below). Note the spots on the gill cover of the male and the strongly visible seventh vertical band on both fish. Photographs by A Wood.

Ecology

Stawikowski and Werner report that they have found Heros severus in a variety of water types including white water, black water and clear water habitats. In general sub-adult and adult fish were found in slower moving areas of water (when compared with the main river flow) that were rich in riparian and submerse vegetation. Additional protection from predators for the sub-adult and adult fish is provided by fallen and submerged trees. In the case of juvenile fish the recorded habitat was a sandy, stone-free substrate with plenty of submerse vegetation. The dense, almost impenetrable maze of interconnecting branches and roots from the surrounding vegetation provided suitable protection from predators. It should also be noted that sub-adult and adult H. severus were not found in this sort of environment.

When Stawikowski and Werner returned to the Rio Atabapo in 1995 they were able to record the water parameters and these are reported as a pH of 5, a temperature of 84 °F (29 °C) and carbonate and general hardness that was not detectable with the test kits used. They also noted that further upstream, still in the quiet backwater areas, it was possible to find mixed groups of adult and sub-adult fish in even warmer water.

In the aquarium

Over a three month period a group of wild fish were observed at an aquatic outlet. Finally the common sense approach of telling myself that there was no room for these fascinating fish in the fish house failed, and a pair of fish were selected from the group. While waiting for a suitable tank to become free in the fish house, they were housed in my show tank. The inhabitants of the show tank at that time included a group of wild Angelfish (Pterophyllum scalare) and a pair of dwarf pike cichlids (Crenicichla regani). Over an eight week period the Heros severus spawned on two occasions, unfortunately having the dwarf pikes in the same tank meant the fry never survived.

Female Heros severus guarding eggs. Photo by A Wood.

The pair were eventually moved into the fish house and were housed in a 36 x 18 x 15” (90 x 45 x 36 cm, lxbxh) aquarium which holds approximately 37 gallons (140 litres) of water. The tank is linked to the centralized filtration system in the fish house (approximately 660 imperial gallons (3000 litres) of water) and the water parameters are maintained at approximately pH 4.5 to 5.0, carbonate hardness (°dKH) undetectable, general hardness (°dGH) undetectable, Total Dissolved Solids (TDS) at 56 ppm and the temperature held around 79 °F (26 °C). Water is prepared by passing tap water through a Heavy Metal Axe (HMA) filter (this contains a sediment pre-filter and two different activated-carbon-based cartridges that will remove chlorine, chloramines and dissolved metals but do not soften the water or alter the pH) and then circulating the collected water through moss peat for a minimum of 24 hours prior to use.

The tank is decorated with a silica sand substrate to an approximate depth of 1.5” (3.5cm), large chunks of bogwood and plants (Amazon sword (Echinodorus sp.) and Salvinia natans).

Adult fish are fed twice daily using a combination of a commercially available granular food and frozen foods including bloodworm, mysis shrimp and Pacific Krill.

Female Heros severus guarding fry. Photo by A Wood.

I have now successfully spawned and raised fry from this pair three times; on all occasions spawning has taken place on a selected vertical site (on all occasions so far this has been the bog wood within the aquarium). The eggs are guarded by both parents for up to 48 hours, and once hatched the wrigglers are taken into the mouth by one of the adults for brooding (unfortunately I have yet to be around at the right time to see if the parents help rupture the egg sacs prior to brooding). Over the next five to six days the parents alternate brood-care duties (the process of swapping fry between the adults is something I have yet to witness) before finally releasing a brood of 60 to 80 free-swimming fry for the first time. For the next ten to fourteen days, at the first sign of threat the parents ‘dive’ into the shoal of fry which immediately stream into the parents open mouths; however, after this period mouth-brooding ceases.

Once the fry are free-swimming (both while mouth-brooding and after mouth-brooding ceases) both parents use a series of fin-flicking (ventral and anal fins) gestures to control the group; this flicking appears to indicate a potential threat but not to the degree where a ‘fright’ (hide) response is required.

Fry are fed twice daily using a mixture of baby brine shrimp and frozen Cyclops. After approximately four weeks a crushed commercial flake food is also added into the diet. As the juveniles continue to mature their diet is further supplemented with frozen foods (including Artemia, Daphnia, Bloodworm) and a commercial granular food.

Remarks

For anyone who has successfully kept and bred the Rotkeil Severum, the mouth-brooding Severum Heros severus provides a welcome diversion, and being able to watch mouth-brooding activities ‘close-up’ provides a wonderful insight into the gentler side of these fish.

The one thing that has surprised me though is the poor pair bond between the adults, even the simple action of removing then replacing the décor so that the juveniles can be moved to their own tank disrupts the pair bond sufficiently to lead to two weeks of squabbling and fin nipping before they settle down and patrol the tank together again.

Since writing this article the pair have been moved to a 30 x 24 x 18” (76 x 61 x 45 cm, lxbxh) aquarium in the fish house and would now be considered one (of the few) permanent residents. In this size aquarium I have been able to leave the juveniles with the parents for up to 8 to 10 weeks which coincidentally appears to be a natural method of stopping the parents spawning again.

The maximum size of Heros severus is reported as 8” (20cm), my pair currently measure approximately 7” (17cm) SL (8” (20cm) TL) and apart from increasing in bulk during the last 10 months I do not believe they have grown in length, so would consider them to be at their maximum size now.

Finally, if you have the tank space available it’s worthwhile devoting a tank to a pair, even if just to watch a mass of fry disappear into a mouth that from the outside just doesn’t look big enough.

Fright response, the male Heros severus gathering fry into his mouth. Photo by A Wood.

Etymology

Heros = Greek, heros – hero. It is unclear from the original description why Heckel has used this term.
coryphaeus = Latin, coryphaeus – leader (of a theatrical chorus). It is difficult to relate this context to the species in question. However Heckel remarks that this species is notable for its high forehead and the name may be an error for coryphaenus. A reference to the dolphin genus Coryphaena that shares this characteristic high forehead.
efasciatus = Latin, efasciatus – without bars. In reference to the absence of vertical bars on the type specimen.
modestus = Latin, modestus – modest, unassuming, restrained, sober. In reference to the appearance of this species, known locally as ‘Acara Preto’ (black acara).
notatus = Latin, notatus – marked. In reference to the dark markings in the (preserved) type material.
severus = Latin, severus – serious, severe. Perhaps a reference to the ‘dignified’ appearance of this large cichlid or possibly even a reference to the serious and severe appearance of the preserved type specimen whose coloration was described as brown, barely lighter on the chest with black vertical bars.
spurius = Latin, spurius – false. Possibly in reference to its external similarity to Heros modestus (also described by Heckel in 1840) but not actually being the same species. It is also noted that H. modestus and H. spurius share the same local name of ‘Acara Preto’ (black acara).

References

Jordan, D.S. and Gilbert, C.H. (1882). Synopsis of the fishes of North America. Bulletin of the United States National Museum (16), I-LV, 1-1018.
Kullander, S.O. (1983). A revision of the South American cichlid genus Cichlasoma. Swedish Museum of Natural History, Stockholm, 296 pp.
Kullander, S.O. (1986). Cichlid fishes of the Amazon River drainage of Peru. Swedish Museum of Natural History, Stockholm, 431 pp.
Kullander, S.O. (2003). Cichlidae (Cichlids). In Checklist of the Freshwater Fishes of South and Central America. eds, Reis, R.E., Kullander, S.O. and Ferraris, C.J. pp.605-654. Porto Alegre, Brazil: EDIPUCRS.
Regan, C. T. (1905). A revision of the fishes of the American cichlid genus Cichlasoma and of the allied genera. Annals and Magazine of Natural History (7), 16: 60-77; 225-243; 316-340; 433-445.
Stawikowski, R. and Werner, U. (1988) Die Buntbarsche der Neuen Welt - Südamerika. pp.31-36. Germany: Reimar Hobbing GmbH Verlag.
Stawikowski, R. and Werner, U. (1998) Die Buntbarsche Amerikas, Band 1. pp.221-234. Germany: Eugen Ulmer GmbH.
Werner, U. (2007) Personal communication.

Images and text remain copyright of the author.

First published in Cichlidae, 2008, Volume 29, 4 (July). The journal of the British Cichlid Association.