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Paratilapia polleni Bleeker 1868, A Threatened Cichlid From Madagascar

By , 1997. printer
Published
Paul V Loiselle, 2004

Classification: Species overview, Madagascar.

"Madagascar is the naturalist's promised land. Nature seems to have retreated there into a private sanctuary where she could work on different models from any she has used elsewhere. There you meet bizarre and marvelous forms at every step." ­ Philibert Commerson, 1771
Paratilapia polleni

That the female of this breeding pair of Paratilapia polleni sports far heavier metallic spangling than does her consort points up the unreliability of color differences as indicators of sex in this species. Photo by Paul V. Loiselle.

(This article was originally published in Cichlid News magazine, Aquatic promotions, Vol. 2. No. 2, April 1993; pp. 11-16 and Vol. 2. No. 3, July 1993; pp. 17-20. It is here reproduced with the permission of Paul V. Loiselle).

Natural History And Husbandry

Madagascar is a world out of time. Formerly a portion of the southern supercontinent whose fragmentation gave rise to Australia, Antarctica, India, Africa, and South America, Madagascar has existed in nearly total isolation from the rest of the world since it split away from Gondwana nearly 165 million years ago. This long isolation has allowed its plants and animals to follow evolutionary pathways very different from those pursued on the African mainland (or anywhere else in the world, for that matter). For over two centuries, biologists have echoed the amazement of the 18th century French naturalist Commerson over the end products of this parallel evolution. It is thus hardly surprising that popular accounts of the unique Malagasy biota have also tended to focus upon highly unusual terrestrial organisms, either extinct, such as Aepyornis, the heaviest known flightless bird, or extant, such as the island's numerous chameleon species. As scientists have grown more familiar with the plants and animals of Madagascar, it has become equally apparent that this isolation has favored the persistence of phylogenetically primitive species that have long since been replaced elsewhere by more highly evolved representatives of their respective lineages. The numerous lemur species are without a doubt the best known of Madagascar's "living fossils."

However, apart from a handful of ichthyologists, few are aware that Madagascar supports a diverse assortment of endemic freshwater fishes that stand in essentially the same relationship to their extra-Malagasy relatives that lemurs do to other primates. Such ignorance on the part of the wider public is considerably easier to understand than that of tropical fish enthusiasts. The freshwater ichthyofauna of Madagascar is amply endowed with species that would make excellent ornamental fishes. Yet apart from a single killifish, Pachypanchax omalonotus (Dumeril 1861), and the popular Madagascar rainbowfishes of the genus Bedotia, this fauna has been quite unrepresented among the ranks of aquarium fish. The case of Madagascar's endemic cichlids is particularly noteworthy in this regard. Eleven of the thirty-two Malagasy fish species known to complete their life cycles without access to the sea are members of the family Cichlidae. These endemic cichlids are sufficiently attractive to have led at least one ichthyologist to predict their favorable reception by amateurs of the family (Keiner, 1963). Nevertheless, as of the early 1980s, only a single representative of these cichlids, Paratilapia polleni Bleeker 1868, had ever been seen alive outside Madagascar. Specimens were displayed in the zoological garden of the Jardin des Plantes in Paris just prior to World War II, but captive breeding was never achieved (Catala, 1977). Their potential notwithstanding, the Malagasy endemics remained an aquaristic cipher (Loiselle, 1985).

This state of affairs reflected to a considerable extent both the relative inaccessibility of Madagascar to potential collectors of aquarium fish and the difficulties attendant upon collecting and exporting Malagasy animals once on the spot, no less than uncertainty attendant upon any effort to establish an aquarium population with a very limited number of founders (Bardin, 1983). Be this as it may, the unavailability of aquarium stocks of Malagasy cichlids was as frustrating to students of cichlid behavior as it should have been to aquarists. By virtue of their basal position within the family, the Malagasy endemics are particularly well placed to shed light on the evolution of cichlid parental behavior. On the basis of brief accounts by a handful of French biologists who had the opportunity to observe parental individuals in the field (Catala, 1977; Keiner, 1963; Keiner and Mauge, 1966.), it was known that several species were biparentally custodial substratum spawners. However, the laboratory studies necessary to obtain a fuller understanding of their reproductive biology had to remain in abeyance pending the importation of live Malagasy cichlids.

In 1988, Drs. Melanie Stiassny and Peter Reinthal, both then working at the American Museum of Natural History, informed me that they had received the support necessary to mount a collecting trip to Madagascar. Both were very receptive to the suggestion that they attempt to bring back both living and preserved material of the fishes they intended to collect. I supplied them with plastic bags and life support equipment, made a pest of myself with advice on holding and transporting live fish in the field and packing them for transport, wished them Godspeed and good fishing on their departure, then settled down to impatiently await the outcome of their efforts. My pleasure upon hearing of my colleagues' safe return was exceeded only by my excitement when Melanie informed me that they had succeeded in bringing back live specimens of a distinctive Bedotia phenotype and two Malagasy cichlids, among them P. polleni, the most primitive known living member of the family. She and Peter kindly made a number of wild-caught specimens available to me for photography and observation and were even more generous in their gift of fry resulting from the first successful spawning of this species in captivity. The observations that follow on the general husbandry of this species are based on my experience with both wild-caught and captive-bred individuals, while those on its reproductive behavior derive from the latter alone.

Paratilapia polleni
The so called "Pelmatochromis-spot" is clearly visible in the soft dorsal and on th eupper back of this juvenile marakely. Photo by Paul V. Loiselle.

Paratilapia polleni

This parental male Paratilapia polleni shows the more rounded cranial profile and longer soft dorsal and anal fins characteristic of his sex. Photo by Paul V. Loiselle

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Paratilapia polleni is a midsized cichlid, capable of growing to 30.0 cm standard length (SL), although specimens two-thirds that size would be considered large by contemporary Malagasy fishermen (Raminosoa, 1979). In body plan it is superficially more reminiscent of some of the Mesoamerican cichlids than of any of the family's African representatives. The color pattern of territorial adults is evocative of the diamond sunfish, Enneacanthus gloriosus (Holbrook 1855) or the coral comets of the genus Calloplesiops. It is quite unlike that of any known cichlid, although the presence of a so-called "Pelmatochromis spot" in the dorsal fin of juveniles and sexually quiescent adults recalls that West African lineage.

This distinctive color pattern is recognized in the Merina name of marakely, meaning "black fish" (Raminosoa, 1979), the vernacular designation by which P. polleni is known on the island's populous central plateau and along much of its east coast. As this Malagasy name has passed into both the scientific (Keiner, 1963; Keiner and Mauge, 1966) and French aquaristic (Bardin, 1983; Catala, 1977; Nourissat, 1992) literature, I herein suggest its adoption as the English common name for this distinctive cichlid.

Marakely are easily sexed. Males grow up to a third again as large as females. At a given age they are longer-bodied than females, have a much more rounded cranial profile and sport longer, more pointed soft dorsal and anal fins. These distinctions are clearly evident in fish six months old and become more pronounced with increasing age. Color differences are less marked. According to Raminosoa (1979), the pattern of blue and gold spangling is more extensive in males than in females. This observation proved true for the grandparents of my fish as well (Stiassny and Gerstner, 1992). However, Bardin (1983) presents a photograph of a sexually active pair of P. polleni in which the female is clearly the more extensively spangled of the two. Among the numerous descendants of the pair studied by Stiassny and Gerstner, the sexes are either indistinguishable in this regard or else the female sports more spangling than the male. Given such a degree of interand intrapopulational variability, color pattern does not appear to be a reliable indicator of sex in this species.

This species grows large enough to qualify as a food fish. To judge from comments made about the flavor of its flesh in early accounts of this species' natural history (Bleeker and Pollen, 1875), the marakely has long been appreciated as such by natives and visitors to Madagascar alike. It is impossible to assess its former commercial importance on the basis of existing data. However, it seems safe to conclude that this essentially solitary carnivore was never landed in the same numbers as the herbivorous dambas of the genus Paretroplus or the omnivorous saroy, Ptychochromis oligoacanthus Bleeker 1864.

The marakely occurs on both slopes of Madagascar at altitudes up to 1500 meters

The marakely occurs on both slopes of Madagascar at altitudes up to 1500 meters (Keiner, 1963). Not surprisingly given its extensive range this species is the most physiologically plastic of all Malagasy cichlids. It can survive brief exposure to temperatures as low as 12°C and considerably longer stays at 15°C (Keiner, 1963). This tolerance of low water temperatures doubtless explains why specimens of P. polleni collected by Stiassny and Reinthal survived several nights in an unheated hotel bidet better than other Malagasy cichlids! At the other extreme, populations have been reported from hot springs in the southern portion of the island with water temperatures as high as 40°C (Catala, 1977). This species is equally undemanding with regards to water chemistry. The marakely appears to be the dominant predator of the blackwater habitats favored by Bedotia species (Bardin, 1983). Reference has already been made to its occurrence in the alkaline, highly mineralized waters of soda springs, while there are published accounts of its capture in lightly brackish water along the coast (Keiner, 1963; Nourissat, 1992).

This plasticity persists in captivity. A temperature range of 20-23°C suffices for day to day maintenance, with an increase to 25-30°C for spawning. Wild-caught marakely bred repeatedly in New York City's soft (= 3 DH) water, to which one heaped teaspoon of non-iodized table salt was added per 50 I of water and whose pH had been adjusted to 7.5-8.0 (Stiassny and Gerstner, 1992). Their Fl and F2 descendants have done likewise in water of the same hardness with a neutral to slightly acidic pH to which no salt was added. Fry sent to the Dallas Aquarium have grown to a robust maturity in much harder, alkaline water, but have not to date spawned successfully. An independent test of the ability of P. polleni to cope with hard, alkaline conditions in southern Florida was prematurely terminated by Hurricane Andrew. However, this species' ability to prosper in a wide range of habitats in nature suggests such efforts are likely to enjoy a positive outcome. Marakely are considerably less tolerant of poor nitrogen cycle management. I do not know whether they are simply sensitive to high nitrate concentrations per se or intolerant of the abrupt pH drop that elevated concentrations of this ion can provoke in my soft water. Whatever the immediate causal factor, fish stressed in this manner are extremely vulnerable to parasitic protozoans. I lost fish to such epizootics on two occasions when my program of regularly scheduled water changes was disrupted.

Paratilapia polleni is, as its overall appearance, pharyngeal dentition, and short, simple intestine suggest, a carnivore (Keiner, 1963). Juveniles feed chiefly upon planktonic crustaceans and insect larvae. Larger individuals display a marked preference for small fish, but take invertebrates as the opportunity presents (Raminosoa, 1979). Wild-caught specimens took frozen bloodworms and mysid shrimp enthusiastically from the first. Freeze dried krill were approached cautiously from below and ingested with such care that their disappearance left hardly a ripple on the water surface. Such circumspection suggests a response to avian predation. Madagascar is well endowed with kingfishers and I would predict on the basis of this behavior that at least one species grows large enough to prey routinely on cichlids 15.0-20.0 cm SL. Prepared foods were initially refused. With the passage of time, wild-caught specimens kept with other cichlids learned to take pelletized foods, but they never responded favorably to flakes. Captive-bred fish are much less particular at feeding time. They snap up flakes and pellets as soon as (and in the case of the individuals in my office tank, often before) they hit the surface of the water!

As live fish can transmit parasites to captive cichlids, I do not usually use them as food. Hence the wild-caught marakely were not offered feeder guppies until they had been in my care for nearly eight months and had grown quite large. I was frankly more concerned with documenting their feeding behavior than upgrading their diet, which to all appearances seemed more than adequate to their nutritional requirements. The initial results of this experiment were surprising. Their appearance notwithstanding, the marakely proved amazingly inept predators. At the end of an hour's time, nineteen out of twenty-four guppies were still swimming-albeit cautiously at the surface of the 90 gallon tank to which they had been introduced. None of the missing had fallen victim to Paratilapia predation! Despite many energetic attempts by the marakely, honors were instead about evenly divided between a male Haplochromis "rock kribensis" and a pair of 'Cichlasoma' heterospilus. Something is clearly amiss when a piscivore is outcompeted at its own game by species that feed chiefly upon insect larvae and detritus. As all contestants were equally naive with respect to piscine prey, prior experience could not be invoked to explain this differential success rate. I went to bed that evening wondering if marakely have a sensitive developmental period during which they must be exposed to piscine prey in order to develop appropriate hunting behavior.

Any feelings of guilt I might have entertained with regard to the upbringing of my charges were dissipated by the splashing sounds that came from my fish room about 6:00 the following morning. The aquarium lights were off, the room's only illumination coming from the slowly breaking dawn. Given the placement of the room's windows, this had the effect of silhouetting the surviving guppies, who were still swimming about just beneath the water surface, against the brightening sky. The same Paratilapia that had performed so miserably as predators the previous day were picking off panicked guppies with a degree of precision that would have done credit to a laser-guided anti-tank missile! The marakely, it seems, is a crepuscular predator, feeding preferentially at those times when its prey is more easily located and, presumably, approached. These observations dovetail nicely with those of Raminosoa (1979), who found that individuals captured prior to 8:00 in the morning and around 17:00 in the afternoon had much fuller stomachs than individuals taken during the remainder of the day. On the basis of these data, she concluded that the Manganosy population of P. polleni fed twice daily, the pattern one would expect of a crepuscular predator.

Nourissat (1992) reported this species to be susceptible to Oodinium. As noted previously, this species seems vulnerable to "ich." Once infested, individuals seem incapable of mobilizing any sort of effective immune response to the parasite. It is not unusual for a specimen to look as if it had been rolled in salt within a few days of the initial appearance of the first encysted parasites. Prompt treatment of ich-outbreaks is therefore of the essence. Proprietary malachite green/formalin based medications can be expected to give satisfactory results if parasitized fish are treated promptly. Extremely heavy outbreaks may not always respond to such treatment. The most effective way of dealing with such stubborn outbreaks is to slowly increase the salinity in the hospital tank. Paratilapia can tolerate a gradual increase in salinity up to that of sea water without difficulty (Kiener and Mauge, 1966). Far lower concentrations of sodium chloride than this effectively combated the infective stages of the ich parasite. Massive outbreaks of ich damage their victims' skin, leaving them susceptible to opportunistic secondary bacterial infections. These may very well prove more dangerous than the original parasitic infestation. Thus regardless of the antiparasitic treatment chosen, it is prudent to dose the patient concurrently with one of the furan-ring based antibiotics.

Predatory cichlids are not as a rule notably gregarious animals and P. polleni is no exception to this pattern. Juveniles engage in a fair amount of agonistic behavior after reaching ca. 2.5 cm SL, but if housed in a sufficiently large tank, this behavior rarely results in more than split fins. Even sexually quiescent adults, if well-fed and housed in a well-furnished tank of at least 75 gallons capacity, tolerate the presence of conspecifics reasonably well. Towards heterospecific tankmates too large to make a convenient snack, their behavior is exemplary. I have housed adult marakely with a wide range of African and Neotropical cichlids. Apart from the odd tiff over access to a particular morsel at feeding time, I have never observed a nonbreeding P. polleni initiate a conflict with its tankmates. This is not to say that the marakely is incapable of holding its own in an aggressive encounter. Primitive though it may be, I have found P. polleni quite capable of giving as good as it gets in encounters with the likes of Hemichromis cf. cristatus, male Haplochromis "rock kribensis" and Herichthys pantostictus. Sexually active individuals are another story altogether, but even established pairs seem disinclined to practice "ethnic cleansing" with quite the preemptive verve of such ecologically equivalent African and Neotropical cichlids as Hemichromis elongatus and 'Cichlasoma' salvini. Tankmates that respect the boundaries of a pair's territory are left alone up to the point at which their fry become free-swimming. Sexually inactive individuals neither dig nor otherwise molest rooted plants, but pairs more than compensate for this forbearance with the onset of spawning.

Reproductive Biology

Paratilapia polleni is a monogamous, biparentally custodial substratum-spawning cichlid (Catala, 1977; Keiner, 1963). Two instances of successful captive breeding have to date been reported. In July 1990, Stiassny and Gerstner (1992) elicited a spawning from a group of five wild-caught individuals held indoors in a large wooden tub 2.0 x 1.5 m. The second likewise involved five wild-caught fish, placed in an outdoor pond in the summer of 1991 (Nourissat, 1992). The following account is based upon my observations of a single F1 and two F2 pairs maintained in the company of a clown pleco (Peckoltia sp.) and a diverse community of West African riverine and Lake Victoria cichlids. All are housed in a planted 250-l aquarium 2.0 m long x 45.0 cm wide serviced by a Sicce outside power filter containing unglazed ceramic rings and a Tetra Double Brillant sponge filter mated to a Hagen 201 power head. Water temperature is held between 25°-28°C with a thermostatic heater; nitrate levels are kept at < 5.0 ppm by replacing 40-60% of the tank's volume with fresh tap water every seven to ten days. The tank is illuminated by two 40 W full spectrum fluorescent lights. A timer guarantees a 14:10 photoperiod. Its residents are fed flake and pelletized food or freeze-dried krill in the morning and frozen mysid shrimp or bloodworms in the evening.

In a community setting, marakely pair readily and unostentatiously. Sexually inactive individuals usually hold solitary station near a cave or piece of waterlogged wood. Interactions with conspecifics are usually limited to discouraging their close approach. Joint occupation of the same space by a male and female is the first indication that pairing has taken place. If other P. polleni are present, the pair may actively exclude them from their territory. Heterospecific tankmates are usually ignored at this point. Young pairs defend a territory ca. 30 cms. The size of the defended area increases with the size of its proprietors. By the time the male of a pair has grown to 15.0 cm SL, the size of their territory may be closer to a square meter in extent. Failure to take this trend into account can result in serious injury to a pair's tankmates and seriously destabilize the pair bond, with possibly lethal results for the female.

Overt courtship begins as early as five and as late as two days (mode: 4 days, mean 3.75 days) prior to spawning. The male performs a quivering display in front of the female, either with his body held parallel to the substratum (lateral display) or with his body tilted at an angle of 45-60° (headstand). I have seen strikingly similar displays performed by courting male Hemichromis cristatus Loiselle 1978 and Gymnogeophagus meridionalis Reis and Malabarba 1988. The female may reciprocate a lateral display and seems more likely to do so with the approach of oviposition, but headstanding is performed exclusively by the male. I never observed either frontal displays or male-female mouth fighting in this species. At the onset of courtship, males are typically darker than females, but both sexes assume a comparable velvety black base coloration as spawning approaches.

Paratilapia polleni
Female marakely fanning a newly deposited, multilayered egg mass. Photo by Paul V. Loiselle.

Paratilapia polleni
Spawns of Paratilapia polleni deposited on waterlogged wood take the form of "ropes" of developing eggs. Photo by Paul V. Loiselle.

Paratilapia polleni

Earlier reports to the contrary, parental female marakely do mouth their eggs, as can be seen in this photograph. Photo by Paul V. Loiselle.

Spawning site preparation typically begins a day after the onset of courtship (mode: 3 days; mean: 2.5 days prior to spawning). Both sexes participate in the excavation of a pit, but the male does the majority of actual gravel moving. The end result of this activity is a substantial pit in the gravel of their aquarium. The volume of gravel displaced in this process substantially exceeds the pair's combined weight. Following the onset of digging, both sexes actively excluded other fish from the vicinity of the spawning site, their intolerance of intruders increasing with the approach of spawning, which occurs within 24 hours of the appearance of the female's beige ovipositor. In four of eight spawnings for which the preliminaries were recorded, the eggs were deposited in a natural depression in a piece of waterlogged wood. The female actively nipped off this site prior to spawning. Such behavior by the male was never observed. In two instances, the pair spawned on the bottom of the pit they had excavated, placing their eggs directly upon the gravel, while in the remaining two, the fish systematically exposed the roots of a stand of Hygrophila and placed their clutch thereupon. It is noteworthy that two reproductively naive F2 pairs showed this behavior. The only other cichlid that habitually spawns on the roots of aquatic plants is Etroplus suratensis (Bloch 1790).

Paratilapia polleni has an unblemished record of success in protecting its privacy chez Loiselle. I have yet to observe an actual spawning. I offer this as evidence that the ability to outwit their keeper is a primitive character state for the family Cichlidae! The ovoid eggs measure ca. 2.0 mm along their major axis. Newly laid eggs are a clear rosy beige, becoming darker as the developing embryos become progressively more heavily pigmented. The eggs are not individually attached to the substratum. Each egg has a long adhesive fiber that tends instead to attach to other such filaments. The end result is a central "rope" to which several hundred eggs are attached. When the eggs are deposited within a pit in the gravel, the end result is a single, very long string of eggs which, through the female's fanning activity, folds back repeatedly on itself to form the dense mass many egg layers deep described by Stiassny and Gerstner (1992). This egg mass is effectively mobile and may very well be moved over the bottom by the female's fanning behavior. The clutch assumes the same form when the eggs are deposited on exposed plant roots, but because the egg bundle is so thoroughly tangled within them, it is not mobile. When deposited entirely or in part upon waterlogged wood, the clutch takes the form of several discrete, shorter egg strings attached at one end to the substratum. Young females produce clutches of several hundred eggs; larger females can spawn up to a thousand.

Each egg has a long adhesive fiber that tends to attach to other such filaments

Hygienic behavior towards the eggs is the exclusive responsibility of the female. It consists chiefly of vigorous fanning of the egg mass with the pectoral fins. Stiassny and Gerstner (1992) did not observe any mouthing of the egg mass by the parental female. Based upon my observations, mouthing of the eggs does occur, but only infrequently. Females were never observed to pick up and move the eggs. The male is not allowed to approach the eggs more closely than a single body length. He spends the interval between oviposition and hatching enlarging the pit excavated earlier and patrolling the perimeter of the pair's territory. The eggs hatch in approximately 48 hours. This observation is consistent with those of Stiassny and Gertsner (1992) and Nourissat (1992) but stands in sharp contrast to the ten day developmental interval at 22°C reported by Keiner (1963) and Catala (1977). The wrigglers are usually simply allowed to pile up on the bottom of the spawning pit. In one instance, the wrigglers and the gravel to which they were attached were moved from the bottom of the pit up into a natural depression in a piece of waterlogged wood. My observations otherwise accord with those of Stiassny and Gertsner (1992) with regard to the absence of overt hygienic behavior towards the wrigglers; parental disinclination to pick up and move them; and the tendency for the female to respond much more aggressively to perceived threats after hatching than before. However, my observations of male female parity with regard to threat displays and overt attack behavior do not support theirs that the female becomes the more aggressive partner once circumstances relieve her of the necessity to fan the clutch.

The fry become fully mobile four days posthatching. They are large enough to take Artemia nauplii for their initial meal and will also accept finely powdered prepared foods without demur. Both parents are actively involved in fry defense. They follow the school of fry as it moves over the bottom of the tank and make no attempt to direct or control its movements, although both male and female retrieve fry that stray too far from the main body of the school and spit them back into its midst. I never observed such overt signaling behavior as ventral fin flicking or head-jerking by the adults nor did I ever see any contacting behavior directed by the fry towards their parents. Once their fry begin moving about the tank, the adults become far less tolerant of other fish. I found it necessary at this point to remove either the target fish or the fry from the breeding tank. The premature separation of parents and fry two days after the first spawn attained full mobility on 29 December 1991 did not elicit intersexual fighting. However, the removal of target fish from the breeding tank at the same point in the ontogeny of the second batch of fry some three weeks later did result in male harassment of the female, followed by the disappearance of the young.

As humane considerations precluded reintroducing target fish into the breeding tank, I installed a barrier made of plastic egg crate diffuser grating with openings large enough to allow the female free passage but too small to admit the male. The history of the next four spawning efforts was varied in the extreme. Shortly after the third clutch of eggs was observed, on 7 February 1992, the male began behaving very aggressively towards the female, whose refusal to leave her clutch placed her at some risk of injury. I moved the male to the other side of the barrier to protect her and by the next day the eggs had disappeared. The pair spawned again a month later and brought their clutch to the free-swimming stage. I removed about half to be reared apart from their parents. Parental care persisted four days longer before the pair ate their young. Five days later, the pair produced another clutch of eggs. The female tended the spawn until hatching, then the male drove her away and assumed a solo custodial role. Either his interest waned or his enthusiasm was not matched by his competence as a parent, because three days later, the wrigglers were gone and he was courting the female through the barrier.

Six days later, on 1 April 1992, the female was once again fanning eggs. Its inauspicious date notwithstanding, this reproductive effort proved an unqualified success. Parental care persisted for three weeks posthatching. By this time, the fry measured 9.0-13.0 mm TL and had begun to show the "Pelmatochromis -spot" characteristic of juvenile individuals. The discrepancy in size was somewhat surprising. Fry reared apart from their parents were much more homogeneous in size at the same age, perhaps due to heavier feeding. As I had two other batches of fry under culture by this time and anticipated an opportunity to display this species at the New York Aquarium, I took the pair and most of their progeny into work, retaining several dozen fry to be reared at home. Although their growth rates continued to be uneven, the size differences that resulted did not lead to sibling cannibalism. Nor was such behavior ever observed in any of the earlier broods prematurely removed from their parents. Intersibling aggression begins about six weeks postspawning. As long as the fry are held at fairly high densities and kept well fed, nothing more serious than the odd split fin will result.

By the sixth month postspawning, the largest fry measure ca. 5.0 cm TL, the smallest half that size. These differences are sexually related, the larger individuals invariably proving to be males. Some individuals will also have developed the midnight black base color of adults and begin to display a rudimentary pattern of metallic spangling. This variation in color intensity occurs independently of size and is a poor predictor of sex. It does seem to reflect social status, the darker individuals also being the most aggressive fish in the group. Serious aggressive interactions begin about 10 months postspawning. Unless the fish are housed in a very large aquarium, human intervention at this juncture is essential to avoid losses. Otherwise the fish will adjust their population density downwards to the level their quarters can support. Females produce their first spawns 11 months postspawning, at ca. 5.0 cm SL, but it takes several months longer to become reproductively competent.

In closing, the freshwater fishes of Madagascar share many features with its terrestrial biota, including that of seriously endangered status. Given the dismal outcome of past attempts to translocate fish populations, it is hardly unmitigated alarmism to predict that unless immediate steps are taken to establish managed populations of those species still extant, the endemic freshwater fishes of Madagascar will not survive through the next century. Aquarists can play a role in such efforts as active participants in institutionally directed species survival programs for Malagasy cichlids. However, the persistent popularity of a given species among tropical fish fanciers can also assure the persistence of captive populations large enough to preserve a significant percentage of its genetic diversity over long periods of time. The physiological plasticity of the marakely makes it a prime candidate for commercial propagation in Florida, while its vivid coloration guarantees its commercial success. It is my sincere hope that this article will engage the interest of both cichlid fanciers and commercial breeders sufficiently to assure Paratilapia polleni the future in the ornamental fish trade that human folly has denied it in the wild.

References Cited

  • Bardin, 1983. A la recherche des cichlides endemiques de Madagascar. Rev. fr. Cichlidophiles (29): 21-34.
  • Bleeker, P. and F. L. P. Pollen. 1875. Poissons d'eau douce de Madagascar et de l'Ile de la Reunion. Leiden.
  • Catala, 1977. Poissons d'eau douce de Madagascar par Rene Catala (suite). Rev. fr. Aquariol. 1:27-32.
  • Keiner, 1963. Poissons, peche et pisciculture a Madagascar. Publ. Centre Technique Forestier Tropical (24): 1-224.
  • Keiner, A. and M. Mauge. 1966. Contribution a l'etude systematique et ecologique des poissons Cichlidae endemiques de Madagascar. Mem. Mus. Natl. Hist. Nat. 40(2):51-99.
  • Loiselle, P. V. 1985. The Cichlid Aquarium. Tetra Press, Melle.
  • Nourissat, - 1992. Madagascar. Reveu Francaise Cichlidophiles (118):9-29.
  • Raminosoa, N. R. 1979. Contribution a l'etude ecologique et biologique du Paratilapia polleni Bleeker 1868 dans le marais de Manganosy. MSc Thesis, University of Madagascar, Antananarivo.
  • Stiassny, M. L. J. and C. L. Gerstner. 1992. The parental care behavior of Paratilapia polleni (Perciformes, Labroidei), a phylogenetically primitive cichlid from Madagascar, with an evolution of maternal care in the family Cichlidae. Env. Biol. Fishes 34:219-233.

Citation

Loiselle, Paul V. (December 14, 1997). "Paratilapia polleni Bleeker 1868, A Threatened Cichlid From Madagascar". Cichlid Room Companion. Retrieved on December 16, 2018, from: https://www.cichlidae.com/article.php?id=76.