(This article was originally published in Cichlids Yearbook Vol. 6 pp. 80-82, It is reproduced here with the permission of author Frank Warzel and Cichlid Press).
|As far as it is known, Dicrossus sp. "Tapajos" is found only upstream of the São Luis de Tapájos rapids. Photos by Frank Warzel.|
The members of the genus Dicrossus Agassiz, 1875, generally known in the literature as checkerboard cichlids, are among the most popular of South American cichlids. These darting, rather graceful, fishes are nowadays being imported more frequently, in particular on account of their interesting patterning, but also because of their splendid finnage. In addition they are very peaceful towards other aquarium occupants and thus appear well-suited to the community setup, but they are in fact basically rather delicate fishes, as becomes quickly apparent when an attempt is made to breed them (if not before). Thus, for example, Dicrossus filamentosus, which originates from a blackwater biotope, requires very acid water with minimal nitrate content. And aquarium decor which involves a bottom layer of scalded oak or beech leaves is not to everyone's taste. In their native waters these fishes are commonly found in quiet riparian bays or residual pools with an accumulation of leaf litter, dead twigs, and the like. Their typical method of searching for food as in the rather larger Crenicara species as well consists simply of grubbing around in the leaves lying on the bottom. An individual leaf is seized by its edge and the fish then swims upwards just far enough for the leaf to begin slowly to tip over; in this way it can turn over leaves that are much larger and heavier than itself. It would appear that these cichlids are searching for the small organisms that live beneath and among the layers of leaves, and which they pick up one at a time.
This behaviour is also exhibited by Dicrossus sp. "Tapajos", an undescribed species known only from a few specimens which were imported live to Germany in September 1992. This new Dicrossus is very easily distinguished from other members of the genus. While almost all members of the Crenicara-like genera, ie the checkerboard cichlids, have two rows of spots, C. sp. "Tapajos" has 3 longitudinal rows of black blotches. Another, again undescribed, species from the Rio Negro system exhibits a comparable pattern, but while in this latter species the individual spots are divided in the centre, those of D. sp. "Tapajos" are uninterrupted. Interestingly, both the Rio Tapajós and the Rio Negro are each home to two Dicrossus species, one with 2, and another with 3, rows of spots. If we work on the assumption that relationships can be deduced from common colour patterns as well as morphological features, then D. sp. "Rio Negro" and D. sp. "Tapajós" should be more closely related to each other than to the other Dicrossus species (with two rows of spots) found in the same river systems. A possible explanation for this would be that the "three-banded" Dicrossus are the geographically separated remnant populations of a species which was formerly far more widespread. It will probably come as no surprise to learn that both species are found in similar habitats, in both cases small streams with sandy bottoms, and rather acid (pH 5.56.5), relatively cool (24-26° C) water.
The specimens we observed, at 2-3 cm only half-grown, were seen singly over leaf-litter in shallow water near the banks. Larger individuals were rather rare. We likewise saw mainly juveniles of D. maculatus, which also originates from the Tapajos system. Their biotope contrasted with conditions at the localities in the upper Tapajos: crystal-clear lagoonlike areas of spring water, where the D. maculatus were generally found in the vicinity of stands of plants. In the Tapajós, as in the Rio Negro, the different species of Dicrossus appear not to be syntopic.
Although it has so far proved impossible successfully to breed D. sp. "Tapajos", and thus establish it in the aquarium hobby, a number of observations on its breeding behaviour have been made. Like D. sp. "Rio Negro" (Windisch, 1992) and D. maculatus (Linke & Staeck, 1995) this species prefers to spawn in concealed sites. So although it was possible to observe the 30 minutelong spawning, the size of the clutch could not be ascertained. The female played the major role in the preceding courtship activity. The pelvic fins of the breeding female took on a reddish coloration and the two lowest rows of spots were replaced by a dark, slightly "washed out" band. After the pair had spawned laying and fertilising alternately the male showed no further interest in the eggs. This behaviour, rather atypical of substrate-spawners as a whole, appears to be the norm for the genus. As the eggs developed the male suffered increasingly frequent attacks by the female, so I removed him for his own safety.
On top an adult male of Dicrossus sp. "Tapajós" (TL about 7.5 cm.), then a male of Dicrossus sp. "Rio Negro" from the upper Rio negro system, lower left it is shown a female of Dicrossus sp. "Tapajós" in spawning dress, evident because of the midlateral stripe pattern. The illustration shows the distribution of the four known Dicrossus species, this illustration appears in Cichlids Yearbook Vol. 6 page 81. Photos by Frank Warzel, illustration by Ad Konings.
At a pH of 5.2, a temperature of 26° C, and a conductivity of about 80 µS/cm (about 1 dH), it was on the 8th day after spawning that the female was first seen leading the fry around the tank, which was decorated with beech leaves, pieces of wood, and small bogwood roots. The small size of the fry at this stage was particularly striking. Unlike those of most other cichlid species, newly free-swimming Dicrossus fry are not yet capable of taking freshly-hatched Artemia nauplii, and as a result the original brood of 40, guarded attentively by the female, decreased in number day by day, even though the aquarium was well-established and should thus have contained adequate micro-organisms. And even though the surviving fry were able to take Anemia on the 4th day, it was not long before none were to be seen. It would thus appear that the conditions in the 70 litre aquarium were not optimal. Unfortunately no further breeding has occurred, so there has been no opportunity to experiment on the basis of what has been learned so far.
|A female of Dicrossus sp. "Tapajos" guarding her 5 days old fry in the aquarium. Photo by Frank Warzel.|
- Kullander, Sven., 1978, "A re-description of Crenicara filamentosa Ladiges, 1958 (Teleostei: Cichlidae)", Mitt. Hamb. Zool. Mus. htst., 75: pp 267-278.
- Kullander, Sven., 1990, "Mazarunia mazarunii (Teleostei: Cichlidae), a new genus and species from Guyana, South America", Ichthyological Exploration Freshwaters, Vol. 1 (1): pp 314.
- Linke, H. & W. Staeck 1992, American Cichlids 1: Dwarf Cichlids. Tetra Press, Melle, Germany
- Windisch, W. (1992) Dicrossus spec. "Rio Negro". DATZ, 45 (12): pp 767-770.", Meet. Mus. Nntl. Hist. Nat. 40(2); pp 51-99.