Fish in Finnish is kala

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Retroculus lapidifer

Blue lipped macho from Rio Tocantis, Brazil

The Latin name for the genus Retroculus is derived from its relatively back positioned eyes. Just as well the name could have been Robustorpedus, for these fish are very powerful and muscular, and yet their overall shape is sleek. The type species R. lapidifer has a distinctive habit of resting on the bottom in a pose resembling pushups, only the supporting hands are replaced by the erect ventral fins. Their swimming seems aqward at first and due to the diminished swimming bladder the fish need to overcome a constant "over weight". However, all aqwardness is gone instantly as something interesting catches their attention and the fish darts with lightning speed. This and everything else in Retroculus seems to be perfectly suited to their rheaphilic (rapids loving) lifestyle starting from behavioural characteristics and strong fins, and ending to the extremely adhesive eggs.

Phylogenetic relationship of the genus Retroculus to other neotropical cichlids has been much studied lately. Kullander separated Retroculus from being a part of subfamily Geophaginae to forming its own group Retroculinae . This view was later confirmed by two studies on mitochondrial and nuclear DNA by Farias et al., which demonstrated the basal position for Retroculus among all of the neotropical cichlids. In other words, even though Retroculus might seem as stretched Satanopercas to some they bare no more relation than Retroculus and for example discus do.

 

Spawning

I got my first four R. lapidifers in 2002 when the 3-4 cm long juveniles being the very first in Finland moved to small 160 litre aquarium. The small Retros ate almost anything with gusto and after growing to double the size they moved to a larger 530 litre aquarium. In the bigger tank the fish spurted in growth and after a year of maintenance the largest measured 15 cm. At this point a pair was suddenly formed and both the male and female (this was evident due to larger size and bulkier appearance of the male) began to dig a large sand pit. There was clear excitement in the aquarium for couple of weeks but eventually nothing happened. A week later I was fortunate to meet with Thomas Weidner who visited our national club's (Ciklidistit) seminar series in Helsinki and asked him for his opinion on my high hopes of breeding. Thomas was rather blunt in his answer that the fish are still too small and young, and that maybe when they are 20 cm...

As foreseen by Thomas courtship ceased and it took a full year before it resumed. This time it got wild. The couple put up a show of branchiostegal flaring and lateral display unmatched by any cichlid I've witnessed to spawn. They also displayed a curious habit of pointing their head to a certain spot next to some stones and then shaking their head aggressively. After almost two weeks of courtship the pair dug a pit to the spot they had pointed to. Digging went on for couple of days until one day as I returned from work everything seemed to be over. The pit was half covered and the couple showed lessened interest to each other. The next day it became evident that something had gone wrong as they lost their interest totally and let other eartheaters to rumble through the spot of their pit. The water parameters during the spawn were the following: +28.4°C, pH 6.3, NO3 10mg/l, NO2 <0.1mg/l, and 2.5°dKH.

Another month later courtshiping started again being, if possible, even more extravagant. This time I removed the Satanoperca daemon that had also gotten over exited the last time. After this all other fish in the tank withdrew to their hiding places and the retro-couple started digging. They generated a 25 cm wide and 10cm deep pit next to pile of fist sized rocks aligned by a handsome pile of sand. Three days later the spawning took place. This time I happened to be at home as the courtship suddenly changed to a synchronized swimming where the female first laid 10-20 eggs per run and the male having waited right next to females tail immediately followed to fertilize and mix the sperm, eggs and sand. After couple of runs both parents started to carry on top of eggs one to three mouthfuls of coarser sand and gravel they previously had separated from otherwise fine sand and piled right next to spawning site. At this point it was noticeable that the eggs were very adhesive. This no doubt reflects the fast flowing natural habitats of the Retroculinae; the already heavy eggs gain extra weight by clinging to sand grains and therefore avoid being swept away by the current. Wild R. lapidifers use even relatively large pebbles to cover their eggs, but apart from the fine “eartheater sand” of 1mm grain size I only had to offer gravel 5-10mm in grain size. Apparently by using larger sand/pebbles Retroculus secure the oxygen supply of even deeply covered eggs as more water will flow through.

After over ten runs of egg laying the couple had a breather. I couraged my self to remove approximately a third of the sand with eggs by hose and moved them in to a hatching/fry box located right in front of filters exhaust to provide enough of current in a separate 60 litre tank. The male was relatively aggressive towards me as I siphoned some of the eggs, but the parents relaxed after I finished. Next they started a task that would go on for 24 hours a day. The pair moved the eggs together with the coarser sand in to newly dug pits approximately 4 times a day. The fish did not rest but even during the night the process went on facilitated by the night-light left on in the neighbouring room. This effort was such that being used to the well oxygenated waters in their natural habitats the fish stressed themselves to near fatigue by their hyper active behaviour under the suboptimal conditions offered in aquarium and were breathing abnormally heavy all the time. None the less, the couple found both the time and energy to keep on bonding with each other with regular lateral display extravaganzas even in the middle of all the moving and digging.

The separated fry started to hatch already 72 hours after spawning, but despite of the small preventive dose of methylene blue approximately 80% of the eggs fungused and did not hatch. The high density/weight of the eggs seemed to remain and hatching really just meant an appearance of a hair thin and rapidly moving tail in to the eggs. Meanwhile the parents in the larger tank continued their over active moving business, which especially now that the fry had hatched seemed so rough that it is a small wonder the fry were not injured by the accompanying gravel. After a week I siphoned the rest of the fry together with the sand to the same smaller tank since the parents by then seemed exhausted. Even though the fry were hard to distinguish from the sand it became later evident that the hatching success had been far greater with the parents than in the separate tank. It is likely that the rough looking caring and constant egg manipulation is beneficial by possibly rubbing off any detrimental substances or even by shedding off some outer shell protecting the eggs for the very first days after fertilization.

The following day (eight days after mating) fry became free swimming and already day after they started feeding on freshly hatched Artemia naupli. Later the little Retros have moved to Bosmids and further to Chironomid larvae (blood worms). Blood worms seem to be the preferred food which is not surprising since Moreira et al . have published that 50-99% of the stomach content of Retroculus lapidifer consists of Chironomid larvae. Despite their appetite R. lapidifer s are rather slow in their growth at least in comparison to Satanoperca jurupari fry kept in the same 240 litre tank. Where as the S. juruparis peacefully graze the bottom non-stop the R. lapidifers concentrate on the people in the room and rush to the feeding spot due to even the slightest movement many meters from the tank. They apparently also consume far more in their very active mode of living and at four months of age and three cm of length they start to exhibit some of their parents character. What marvellous fish!

 

 

 

 

 

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