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A Jewel Of Unexpected Provenance, Gymnogeophagus rhabdotus

By , 1996. printer
Published
Paul V Loiselle, 2004

Classification: Species overview, South America.

* Comment by Dean Hougen.

(This article was originally published in Freshwater and Marine Aquarium Magazine, May 1981; pp. 31-35, 72-75. It is here reproduced with the permission of author Dr. Paul V. Loiselle.).
Gymnogeophagus rhabdotus

Ever since the opening of Lake Malawi to commercial exportation of aquarium fishes, cichlid enthusiasts have tended to regard Africa as the unrivaled source of aquaristic novelties. While no one but a blind man would deny that the Great Lakes of Africa have added some truly magnificent cichlids to the roster of aquarium fish, it is equally true that the Neotropical Cichlidae have also contributed their share of highly desirable species during this period as well. Many of these cichlids were "reference book species," imported in the early years of the hobby and either never established or else lost during the second World War. These apparent newcomers include such species as Cichlasoma salvini, C. maculicauda and C. facetum. Others are true debutants, never before seen by hobbyists. Most of the Central American Cichlasoma species and their allies to have been introduced over the past fifteen years fall into this category, together with a substantial number of South American dwarf cichlids. So also, I contend, does the subject of this essay, the Rainbow Eartheater, Gymnogeophagus australis (Eigenmann 1907).

In a previous article (Loiselle, 1980), I followed Sterba (1966, 1977) in accepting that this species had made its aquaristic debut in 1936. I have since concluded otherwise. Reference to Holly et al. (1934), the source of Sterba's information suggests that the species imported into Germany in 1936 was actually Gymnogeophagus rhabdotus (Hensel 1870), a sympatrically occurring congener. Their account makes no mention of the lyrate caudal fin characteristic of male G. australis, a characteristic clearly visible even in the preserved specimens of the type series (Gosse, 1975, Figure 33). Nor does their description of the color pattern mention the bright red stripes that ornament the upper and lower margins of the caudal fin in both sexes of this species. Both their half-tone drawing and their color description correspond very well to G. rhabdotus, however.

Such an error in identification is understandable if one considers that G. rhabdotus was placed in the synonymy of Geophagus brasiliensis by the Austrian ichthyologist Steindachner in 1874 and not recognized as the senior synonym - and hence valid name - of Geophagus camurus Cope 1894 until Goss (1975) published his revision of the genus Geophagus and its allies. To further complicate matters for Holly and his collaborators, the occurrence of G. rhabdotus in the Buenos Aires region, putative point of origin of the 1936 exportation, does not appear to have been established prior to the late 1960's (Ringuelet et al., 1967). It is, thus, hardly surprising that they drew the conclusion that their fish was identical to G. australis, the only eartheater known to occur in the southern Rio de la Plata area. According to the noted American aquarist, Rosario S. LaCorte, the first person to spawn G. australis in captivity, the present strain of this species is descended from specimens collected in 1978 near Porto Allegre in southern Brazil by Roberto Takase, a Brazilian aquarist who subsequently brought them to the New York import firm TROPA. This represents a significant, though not surprising, northerly range extension for this species, which was heretofore believed to occur only in the coastal rivers of Paraguay, as well as the lower reaches of the Rio de la Plata in Argentina.

For iridescent brilliance of coloration, G. australis has few rivals among Neotropical cichlids. Indeed, the metallic intensity of its color pattern is equaled - but not surpassed - only by the Haplochromis of Lake Malawi and their near allies. I have no hesitation in proposing the common name of Rainbow Eartheater for this scintillating cichlid. As a desirable aquarium resident, it has no rival among the cichlids exported from South American over the last two decades, a contention I can easily document.

First of all, G. australis is as easily maintained as it is beautiful. Contrary to the case with most cichlids from the Amazon basin, this is one South American cichlid that prospers over an enormous range of pH and hardness values. The Rainbow Eartheater was first bred in moderately soft, slightly acid to neutral water. In my tanks, it spawns freely in water with a pH of 8.5 and a hardness of 400.0 ppm TDS. Indeed, G. australis actually seems to look its best in hard, alkaline water, which should certainly endear it immediately to those aquarists living in areas characterized by such water conditions. Like all eartheaters, it is very intolerant of dissolved nitrogenous wastes, however. An easily cleaned, high speed outside power filter charged with an efficient reusable medium such as Ehfi-Fix will prevent solid waste build-up in the aquarium if changed frequently and simultaneously provide this species with the water movement it appears to enjoy. There is no reason why a chemically active filter medium cannot be used to remove dissolved metabolites, but given the tolerance of G. australis for a wide range of water chemistries, a regular program of partial water changes is certainly a more economical means of attaining this end. Like other cichlids from this part of South America, such as C. facetum and Ae. portalegrensis, the Rainbow Eartheater can tolerate temperatures as low as 12°C for brief periods of time without coming to harm. A temperature range of 20°-22°C is ideal for ordinary maintenance, 25°-30°C for spawning.

Like other eartheaters, G. australis is easily fed. A voracious eater, this species takes any of the usual live and prepared foods. The intensity of its red and yellow coloration is, to some extent, dependent upon its diet. Given its catholic tastes, it is a simple matter to supply the appropriate precursor substances for the synthesis of these pigments. Either color enhancing flake foods or finely chopped euphasid zooplankton, sold frozen in most shops that cater to marine aquarists, will suffice quite nicely in this regard. Given its healthy appetite, the Rainbow Eartheater is best given several small feedings daily rather than a single large meal. Though it sifts through the substratum in search of food in the same manner as its congeners, the activities of this species are confined to its superficial layers. They, thus, pose only minimal risk to rooted plants. There is always a chance that the excavation of fry holding pits may result in the uprooting of some plants, but it is sufficiently slight to allow G. australis to be considered a good candidate for planted aquarium.

Perhaps the Rainbow Eartheater's strongest selling points are a combination of modest adult size and easy going disposition. Both Aequidens rivulatus and Cichlasoma festae are newcomers to the hobby who can contend with this species for honors as regards brilliance of coloration, but as far as temperament is concerned, there is no contest at all. As their common names of Green Terror Cichlid and Red Terror Cichlid suggest, neither of those species has established a reputation for docility among aquarists. To put it bluntly, by comparison with their behavior under aquarium conditions, Genghis Khan comes across like a curate at a christening!

Gymnogeophagus australis, on the contrary, is seriously aggressive only towards conspecifics and then only during periods of sexual activity. At this time males begin to defend spawning territories, where females eventually join them. The average territory measures c. 30cms, and resident pairs show little interest in expanding their boundaries beyond these limits even when more space is available. Given such reasonable demands for privacy, several pairs can be housed in a 200 l-300 1 aquarium with a minimum of friction, while a single pair will spawn successfully in an 80 1 tank.

The Rainbow Eartheater will eat very small fish, but it is so inept at catching them that even small poeciliids are safe from its attentions in tanks of l20 l capacity or larger. This species will squabble with tankmates over food, but such interactions are of brief duration and do not seem to lead to serious consequences for any of the parties involved. Heterospecific companions are otherwise ignored save by parental individuals. I hasten to add that the absence of a chip on the shoulder attitude on the part of G. australis does not mean that it cannot hold its own with larger cichlids. Though males rarely exceed 10.0 cm SL, with females approaching a maximum of 8.0 cm SL, this species fares quite well in a cichlid community tank. The Rainbow Eartheater prospers in the company of all save the largest Lamprologus and Cichlasoma species. Haplochromis and their allies appear to be somewhat too frenetic in their behavior to suit G. australis, although the more placid Sarotherodon species make suitable companions.

Gymnogeophagus australis is embarrassingly easy to breed. Indeed, short of physically separating the sexes, I know of no way to prevent a pair from spawning! The onset of reproductive activity is marked by the defense of a territory by a male. His behavior is reminiscent of that of male , but the main object of his defense is a solid vertical surface, not a cave. A resident male will sortie from his demesne to display to available females. Such displays are by no means restricted to unpaired females. A bachelor male will often swim along the perimeter of an established pair's territory and display actively to the resident female. These apparent attempts at seduction are most likely to occur immediately prior to actual oviposition or else two or three weeks into the interval of parental care. Both partners vigorously repulse such importunate attentions in the first instance, but only by the male in the second. I have no idea how successful such a strategy would be under other circumstances, but in my tanks, females appear disinclined to swap partners at any point in the reproductive cycle.


Ripe female

Pair spawning

Female tending eggs

Pair caring wrigglers

Female caring wrigglers

Pair looking after fry

Unattached females respond to a male's lateral displays initially by simply swimming away. Following such a rebuff, a male will typically return to his territory and often engage in a bout of nipping off the future spawning site or digging at its base. As her eggs mature, a female becomes more receptive and signal her interest by remaining stationary at a male's approach. This results in the tempo of the male's display increasing, with vigorous head-shaking and tail-beating appearing in conjunction with the simpler lateral display pattern. The male will then circle back to his territory, nip off or dig some more, and return to repeat his displays to the female. Eventually - - which can be from a few hours to a week from the onset of the male's activities - - the female will follow him onto his territory. The length of her stay will initially be brief, but she will return with increasing frequency and remain longer with each visit. The appearance of a conspicuous lachrymal stripe by the female, together with her participation in the defense of the territory with the male, signals that she has assumed consort status.

The tempo of activity picks up considerably once the female joins the male on his territory, as can be seen from the accompanying photos. With the passage of time, the frequency of the male's displays appears to decline, while that of the female's increases. Digging of pits, primarily by the male, continues throughout this interval. A few days before spawning, both sexes begin making dummy spawning runs over the future oviposition site.

The appearance of a blunt white ovipositor is a reliable indicator that spawning is no more than 24 hours distant. The mechanics of the actual spawning act do not differ from the norm for substratum spawning cichlids. The one spawning I witnessed was in progress at 7:45 a.m. In all other cases wherein I was able to place the timing of spawning with a reasonable degree of accuracy, this penchant for spawning at first light was confirmed. The vertical placement of the spawn depicted in the accompanying photograph is typical. In ten out of eleven spawnings in my tanks, G. australis selected and prepared a vertical surface as an oviposition site. I believe the tally would have been eleven on eleven had I not in one instance substituted a rounded river rock for the pair's preferred spawning site at the last minute. Though not a large species, the Rainbow Eartheater is a prolific one. The spawn-tending female depicted herein measured 5.7 cm SL, but the plaque of eggs being tended numbered over 300. The female is the egg-tending parent. The male is repulsed if he attempts to approach the egg plaque. His role at this stage of the reproductive process is to defend the perimeter of the spawning territory against intruders. The female alternates bouts of fanning the eggs with the excavation of several small pits at the base of the spawning site.

At 28°C, the embryos develop visible eyes 30 hours postspawning. Twenty four hours thereafter, a well developed vertebral column and visible heart action are evident. The eggs begin to hatch 60 hour's postspawning. The female examines the plaque intently at this time and carefully removes the first few wrigglers as they appear. These fry are carried to one of the pre-dug pits.

The remaining fry are gently chewed out of their eggshells. The first two times the pair pictured here spawned, the female alone discharged this responsibility. In subsequent spawns, both parents shared this aspect of parental care. The wrigglers adhere to the substratum by means of the adhesive threads secreted by special cranial glands. Both parents move them from one pit to another until they become free-swimming, four day posthatching. Both parents actively repel potential predators from the vicinity of the occupied shelter pits. The slender fry measure c. 6.0 mm TL. Either microworms or the very small nauplii produced by San Francisco Bay, or Brazilian, brine shrimp eggs are thus in order as their first meal. Within a week to ten days they will grow large enough to manage largerArtemia nauplii and finely divided prepared foods. Their parents, who will also stir up the bottom to produce a cloud of fine detrital particles within which their progeny can forage, diligently tend them. The problem of fry defense is complicated by the fact that young G. australis appear relatively unresponsive to parental direction. They also appear to school more Loosely than do those of either Aequidens or Cichlasoma species of a comparable size. In view of these peculiarities in the behavior of the fry, it would not surprise me to discover that, in nature, the Rainbow Eartheater moves into areas characterized by reduced densities of potential fry predators to breed.

I have found that pairs of G. australis lose interest in their fry between 14 and 21 days posthatching, the point at which the female seems to begin ripening another batch of eggs. La Corte, on the other hand, reports that parental care can persist much longer, the presence of the fry apparently serving to inhibit further spawning. The interaction of water temperature and availability of food in nature probably determine the duration of the period of parental care. In captivity, there is little practical purpose served in prolonging the association of parents and offspring much beyond the third week in any case. Fry growth appears rather slow for the first four to six weeks, then accelerates considerably.

With frequent feedings and partial water changes, the fry can measure 1.5 cm-2.0 cm SL by the eighth week postspawning. Sexual maturity is attained between the sixth and eighth month postspawning, at c. 6.0 cm SL for males, 5.0cm SL for females.

I anticipate a future in the hobby for the Rainbow Eartheater as dazzling as its color pattern. Hardy, unaggressive and modestly proportioned, G. australis combines the iridescent brilliance of a Lake Malawi Haplochromis with the fascinating behavior of a biparental substratum spawning cichlid. This species enjoys only limited commercial availability at present. However, G. australis lends itself extremely well to large-scale propagation. Thus, I feel confident in predicting that aquarists everywhere will soon be able to enjoy keeping this jewel of unexpected provenance in their tanks.

Literature Cited

  • Gosse, J.P. 1975. Revision du genre Geophagus (Pisces: Cichlidae). Mem. Acad. roy. Sci. Outre-Mer (Bruxelles) l 9 (3):1- 172.
  • Holly, , H. Meinken and A. Rachow. 1934-. Die Aquarienfische im Work und Bild. (Lief. 69/70, prepared by H. Meinken) Alfred Kernen Verlag, Stuttgart.
  • Loiselle, P.V. 1978. South AmericanEartheaters: The genus Geophagus and its allies. F.A.M.A. 3 (6): 23- 27 et. seq. Ringuelet, R.A., R.H.
  • Aramburu and A.A. Aramburu 1967. Los peces argentinos de agua dulce. Comision de Investigacion Cientifica, Provincia de Buenos Aires, La Plata.
  • Steindachner, 1874. Die Susswasserfische des Sudostichen Brasilien. Sitz. Akad. Wissench. Wien 70: 499- 538.
  • Sterba, 1966. Freshwater Fishes of the World. Revised English language edition.
  • Studio Vista Ltd., London. 1977 Sus.swasserfische aus aller Welt. Second editon. J. Neumann-Neudamm Verlag, Melsungen.

Comment by Dean Hougen Jan-97

With time comes new information, particularly in the area of nomenclature these days it seems. Such is the case here. The fish Loiselle wrote about as Gymnogeophagus australis in 1981 is now recognized as Gymnogeophagus rhabdotus. Gymnogeophagus australis is a member of the Gymnogeophagus gymnogenys complex and has only been found in the hobby very recently, if it all.

Citation

Loiselle, Paul V. (December 20, 1996). "A Jewel Of Unexpected Provenance, Gymnogeophagus rhabdotus". Cichlid Room Companion. Retrieved on December 17, 2018, from: https://www.cichlidae.com/article.php?id=40.