The Mouth-Brooding Severum, Heros severus

By Andrew Wood

If you consider that the Severum was being imported into Europe and was being successfully bred in private aquaria before the First World War, then the significance of the knowledge learned about keeping and breeding these cichlids in the early days of our hobby and our subsequent success with other species of cichlid cannot be ignored. It is surprising, then, that this group of fish do not figure more prominently in the aquaria of cichlid specialists. This apparent lack of interest is probably due to a combination of an ever-increasing range of new and unusual cichlids that emerge from South America on a regular basis and the presence of mass-produced domestic colour forms of Severum found in our aquatic outlets that bear little resemblance to the wild-type fish. This situation may be changing though, as some of the more colourful wild forms such as the Rotkeil Severum and the subtly coloured mouth-brooding Severum become more widely available within the hobby.

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.



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.

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).

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.

Thanks to AD Wood for this Article , all pictures are © AD Wood