Cynodonichthys magdalenae
CYNODONICHTHYS MAGDALENAE (Fowler 1941)
Originally published as: “Rivulus magdalenae” B.K.A. Information Pamphlet No.87 October 1972
Biotope: Magdalena drainage.
Description of male: A rather deeper-bodied fish than others of the genus though still retaining the typical Rivulus shape. Dark tan to brown along the upper half of the body. Lower half of sides iridescent blue with numerous brown and carmine spots. Underside of head and belly cream to white. The overall colouring of the body resembles a trout to an astonishing degree. Dorsal and anal fins yellow to orange outlined with a black edging. Caudal dark with a broad vertical stripe varying from yellow to red running the entire trailing edge of the fin. Pectorals and ventral fins smokey grey, the gill covers have a large greenish-blue spot directly in front of the pectorals. A broad lateral line composed of large dark spots runs from the gill covers to the caudal peduncle. This line is most prominent in females and young specimens, rarely becoming obvious in adult males except when they are frightened or ill-at-ease. The lower lip is margined in black and the eye is small with a gold iris.
Size of males: Wild specimens 3.5 to 4 inches, aquarium raised specimens seldom exceeding 3 inches.
Description of female: Basically the same as the male. The blueish sheen on the sides is less vivid, there are many more and larger dots along the entire body and the lateral line is quite prominent. The anal and dorsal fins are pale yellow without the dark edging and the caudal fin lacks the vertical border. There is a large “Rivulus spot” at the base of the tail. Somewhat larger then the males in both wild and tank raised specimens.
Maintenance and breeding: Water conditions seem to mean little here. A pH of from 6.4 to 7.4 and a hardness ranging from 2 to 10 degrees German are all acceptable providing any changes are brought about gradually. An addition of one teaspoon of salt to the gallon is desirable. A heavy cover of floating plants should be provided to give a feeling of security and to prevent leaping out, an exercise at which this fish is extremely adept. This species is very fond of lying, half submerged, on a cover of floating plants and any plant such a Riccia or Water Sprite will serve very well. Temperatures may vary quite a bit, though for best propagation and raising of the young temperatures of from 75 degrees to 80 degrees F. will give the best results. Floating mops or plants such as Riccia can be used for breeding. A well-conditioned trio will produce 90 to 100 eggs within a three-day spawning period with a surprisingly low percentage of infertile eggs. The eggs hatch normally at a temperature of 75F. within 14 days, a few taking 21 days to complete incubation. At times, for some reason unknown to this author, the eggs will refuse to hatch even after 35 days incubation period. In this case a generous supply of micro worms should be introduced to the hatching container. This will usually result in 100% hatching inn less than 2 hours. Milder forms of force-hatching should be tried after 21 days, such as increasing the carbon dioxide content or by changing the water. If this fails, then after 30 days, the mirco worm treatment should be used. The fry are large and dark and after absorbing the yolk sac may be fed micro worms and newly hatched brine shrimp. They grow quite rapidly and can consume grindal worms in 3 to 4 days. After two weeks they may be fed chopped tubifex, crushed beef heart and sifted daphnia. They are completely sexed out at two months of age and will appear as perfect miniatures of the adults when three months old.
They are sexually mature at six months of age and will produce fully viable eggs at this time if properly conditioned. While about 2.5 inches long at this age full size will not be reached until they are 12 to 15 months old.
Summary: A large robust species with an appetite to match. Timid and quite shy when first acquired, they will settle down nicely if conditions are to their liking and in a short time will become quite brave, even to taking food from the fingers of their owner. Will eat just about any food that is supplied and are not over pugnacious. Smaller specimens of Epiplatys, Aphyosemions and the like are tolerated or completely ignored though care should be taken when introducing other Rivulus species to their tank. A very likeable and colourful Rivulus that deserves to be held in higher esteem.
CYNODONICHTHYS MAGDALENAE (Fowler 1941)
Originally published as: “Rivulus milesi” B.K.A. Information Pamphlet No.81 May 1972
Biotope: A species with a wide range inhabiting fast streams and tributaries of the Rio Magdalena and Rio Meta drainage.
Description of the male: Dorsally brownish with some blue highlights, in old adults this may turn a dull white due to loss of pigmentation in the dorsal scales. Flanks blue to mauve with minute red spotting. Belly yellowish white to ochre in adults of advanced age. Dorsal fin small and placed well towards the caudal, green to light blue and having some brownish spotting. Caudal brown with some blue highlights an outer margin top and bottom of thin black, the outer edge of the caudal being of intense white. In some specimens this outer edge may be of yellow or orange. Anal green with some rust spotting at the base and margined thinly with black. Paired fins pale green to transparent.
Description of the female: Brown olive to grey and carrying some dark spotting, occasionally females may carry some highlights of metallic blue. All fins, apart from the caudal, transparent. Caudal being overlaid with white on which is superimposed a pattern of black. Rivulus spot present.
Size attained: Given good feeding plus ample accommodation will reach some four inches. Males in the wild sometimes exceeding five inches. Females in the aquarium to about three and a half inches.
Maintenance and breeding: Easily kept and bred. Any water conditions seeming to suit. As this is no dwarf species large tanks should be used. Feeding presents no real problem as both live and dried foods will be accepted. Earthworms of convenient size eagerly taken as are tadpoles and newly developed frogs.
Spawning will occur at a temperature of 72F. and will be induced by a partial change of water which is slightly cooler than the tank water. Floating nylon mops may be used as a spawning media eggs being laid on any part of the mop and also the cork by which the mop is suspended. Eggs should be collected daily and placed in shallow hatching containers. Eggs hatch in about 14 days at 70-72F. Fry large on hatching and will be able to consume the first fry foods. To encourage growth fry should be moved on at an early stage to larger accommodation. Sexing at an early age but full growth not attained until about 15 months old.
Summary: No doubt a very good fish for the beginner and pretty when a young adult. Not over pugnacious several males and females may be kept together without undue damage occurring. A good species for a display tank. It was thought some years ago that the maximum size attained in the aquarium was somewhat less than the figures given in this IP.
References: