Amatitlania myrnae

Amatitlania myrnae is a small, Central American cichlid that breeds in burrows or otherwise sheltered places.

Amatitlania myrnae

Cryptoheros myrnae is named after the Costa Rican ichthyologist Myrna Isabel López Sánchez, director of the Zoological Museum in San Jose. In 1986 she assisted the American Cichlid Association ACA on a catching trip in Costa Rica. Also included was Paul Loiselle, who obtained the type material of this fish on this trip.

Description

Amatitlania myrnae is a small, Central American cichlid that breeds in burrows or otherwise sheltered places. In contrast to most other cichlids from Central America, it is the females here that form a territory during the mating season. Here they court passing men (in the same manner as the men of the rest of the generations). During the courtship period, these females display a distinctly different bridal plumage from males. We call this “sexual dimorphism”. More precisely, “reverse sexual dimorphism” because it is precisely the females with the most striking colours here.

During the mating season, females develop a trapezoidal dark zone on a predominantly sky-blue abdomen, surmounted by a horizontal golden-yellow band of gill covers to the dark spot in the middle of the body and sometimes further. This lateral spot increases in intensity while at the same time the intensity of the caudal peduncle decreases. The chromatophores of the double gold-lined dorsal fin spot are now also fully open. The males hardly change during this period.

Amatitlania myrnae is not the only Cichlid with reverse sexual dimorphism. This form of courtship has also been observed in other members of the genus Cryptoheros, such as Cryptoheros nigrofasciatus, Cryptoheros Septemfasciatus and Cryptoheros nanoluteus. Much is still unclear, for example, “what drove the evolution of reversed sexual dimorphism”. Competition between females? Limited breeding opportunities? Polygamy of men? We do not know. The question of why reverse sexual dimorphism does not lead to an inverted role pattern in brood care, or in the reverse order (as you would expect) remains unanswered. Females of Amatitlania myrnae raise their offspring in the same way as other Central American cichlids.

After spawning, the appearance of the female changes dramatically. All red and yellow shades disappear from the body. This also largely applies to the blue. The melanophores in the dorsal fin and caudal peduncle contract, while the melanophores in the nose, throat and abdomen and those of the lateral spot open further. The result of this makeover is a silvery-grey fish with a black nose, throat and belly region. She will herd her young in this conformation for the next few weeks. And she does this with gusto. Few female cichlids are as fanatical as Cryptoheros females. Even in crowded aquariums, they often manage to raise young and not just their own.

In nature, three out of four Amatitlania myrnae nests are found to contain young from other Cichlid species (Michael Tobler 2007). Another notable in-situ observation by the latter researcher is that most Amatitlania myrnae females raise their young alone, in contrast to aquarium observations in which the males apparently cannot evade their parental duties and are often even more fanatical than the females.

Origin

Panama, Costa Rica.

Distribution

According to the existing literature, the fish occurs in only a few rivers of Costa Rica and Panama that flow into the Atlantic Ocean, namely from the Rio Estrella in Costa Rica (Fromm 1988) to the Rio Guarumo in Panama, where the baton is taken over by Cryptoheros nanoluteus (Bussing 1998). Here they occur between 40 and 150 meters above sea level. However, Michael Tobler did not find the fish in the Rio Estrella in his 2007 survey. However, the fish certainly occurs in the Rio Sixaola basin. In 2002 Michael captured fifteen specimens for his research in the Rio Uatsi (one of the entrances to the Sixaola) and transported them to Europe. The Rio Sixaola is considered a transition zone between the Costa Rican (San Juan) Ichthyofauna and the Panamanian (Istmica) Ichthyofauna and contains several endemic species.

Amatitlania myrnae
Amatitlania myrnae

Behaviour

The temperament of this fish does not keep up with the size. The fish are much spicier than you would expect. Especially during the mating season, the character of these dwarfs can be called enormous and they often manage to raise young even in overcrowded tanks.

Diet

Omnivore that in nature feeds, among other things, on detritus of plant origin (Bussing 1998). This should be taken into account when caring for the aquarium.

Breeding Amatitlania myrnae

Juan Artigas says “Amatitlania Myrnae breeds in the spring before the rainy season starts. I witnessed breeding activities in March and April in the tributaries of the Rio Sixaola. Females chose a sheltered nesting site between rocks or wood and showed themselves to males, exhibiting their colourful body parts, which intensified during this time.

Pairs were formed and the colour changed to a bright black and white pattern. Flocks guarded their swarm of babies (which don’t exceed 100 in my estimation) once they swam free. Females closely guarded their young, leading them with spastic movements of opening and closing the fins. Males guarded the space around it.

Juveniles were fed by the female (probably also, but less frequently by males) who used the pectoral fins to turn the soil on which the young fed. The cubs were apparently kept under surveillance for several weeks because I saw babies as small as 1.5 cm and still in the care of the parents.” Thus, Juan Miquel Artigas Azas.

The Aquarium

Similar to Amatitlania septemfasciata.

The habitats of Amatitlania myrnae are the shallow areas of rivers and streams with medium to fast-flowing water with sandy silt or leaf bottom. Shelter in the form of rocks or driftwood, but with few plants. Water is clear, alkaline and hard. Temperature between 24 and 26 Celsius. Occurs together with Amatitlania nigrofasciata and Cribroheros bussingi. This fish is easy to keep in an aquarium from 120 centimetres that take into account the natural habitat.

Amatitlania myrnae
Amatitlania myrnae

The water in which Amatitlania myrnae naturally occurs is in all cases oxygen-rich. This is therefore an important condition with regard to keeping them in an aquarium. This means not too many fish in combination with good filtration and regular water changes. We also have to keep an eye on the maximum temperature in this regard. The fish are found within a temperature range between 21 and 27 degrees. Juan Artigas even mentions a site with a water temperature of 20 degrees. I would therefore not maintain too high temperatures for the aquarium. Certainly not above 26 Celsius. The water in which they occur can also be called soft by Central American standards. Until 9 dgh. with a pH range between 5.5 and 8.

Considering the foregoing, Amatitlania myrnae is not a difficult aquarium fish. The small size allows housing in aquariums from one metre. Juan Artigas tells on his site about successfully keeping a colony of Amatitlania septemfasciata in a 120-centimetre tank for many years. This tank accommodated 25 fish of various sizes and four territories. Whenever a male belonging to one of these territories died, he was succeeded by the next in the hierarchy. Juan also says that these are the absolute minimum conditions for keeping these fish. Under current European standards, an aquarium of approximately 160 centimetres would be recommended for the aforementioned setup.

Amatitlania myrnae keeps well with other Central American fish. Combinations with small species such as Thorichthys and larger species such as Astateros do not cause any problems. Less suitable are combinations with other Amatitlania. This is due to the risk of hybridization.

Video’s

Author

Rene Beerlink – NVC

Copyright images

AquaMojo
Matthijs Meindertsma

Literature

Bussing W. A. 2002. Freshwater Fishes of Costa Rica. Blz 340-342.

References

Loiselle P. 1997. “Diagnoses of two new cichlids from the Rio Sixaola Drainage, Costa Rica”. Buntbarsche Bulletin. (n. 180); p 1-8. Hiervoor werd deze vis gezien als een variant van C. septemfasciatus en stond bekend onder de naam Cryptoheros (Archocentrus) septemfasciatus “Topaz”. C. myrnae onderscheidt zich van C. septemfasciatus door, (1) de aanwezigheid van paralelle rijen gele punten op de schubben van de onderste helft van het lichaam. (2) De vage zichtbaarheid of afwezigheid van vertikale banden. (3) De aanwezigheid van kleine iriserende blauwe puntjes in de zachte stralen van de rugvin en staartvin. (4) Bij de vrouwtjes (in de paartijd) aanwezigheid van een trapeziumvormige donkere buikzone, lopend schuin naar boven vanaf  het begin van de buikvinnen, tot aan één schubbenrij boven de borstvinnen. Van daaruit naar achteren naar het onderste gedeelte van de midden-laterale vlek en dan weer schuin naar beneden tot net boven het begin van de anale vin. Aldus Loiselle P. 1997.

Last Updated on 5 December 2021 by John

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