568 EXPERIMENTAL FISH EMBRYOLOGY 



9- Pterophjllum elmekl . the angel fish deposits eggs on Saglttarla, Spatter- 

 dock, or Cryptocoryne. Fry hatch In kQ hoiirs. 



10. Ambaasls lala . the glaaaflsh deposits eggs on Myrlophyllum or Elccla. Fry 



hatch in 1+8 hoxu-s. 



11. Hippocampus . the sea horse. Incubation period 6 to 7 weeks. 



B. Buhble nest builders . 



In general these fish are Isolated from each other until males and females 

 show tendency to build surface nests of bubbles. Pairs of such fish are then 

 brought together and observed for several hours to determine whether they will 

 mate or fight. After ovlposition, the females are removed from the tank and the 

 males care for the eggs and young through hatching. Females will be destroyed by 

 the males if they are not removed. 



1. Betta splendans . the Siamese Fighting fish. Suggest getting pure colors, 



such as red, white, and blue (representing varieties). Mortality of eggs 

 and embryos is very high, but the egg is excellent for study and the court- 

 ship and fertilization procedures allow the investigator to secure eggs at 

 the moment of Insemination. Very rapid embryonic development. 



2. Gourami . various species such as Dwarf, Blue, Mosaic, and Kissing Gouramis 



all of which breed rather frequently and eggs develop rapidly. 

 5. Paradise : Brown and Albino. These need not be kept in isolation until they 

 show signs of bubble-nest building, and breeding. Early embiyos develop 

 rapidly with high viability, but mortality great after about 2 weeks when 

 there is a change of diet. Many will go through to sexual maturity. 



LITE BEARERS : 



With these fish the eggs are fertilized within the female where they develop in a 

 chamber, without any maternal connections, sometimes beyond a stage comparable to the 

 hatching stage of egg laying fish embryos. The young lie folded head to tall and are born 

 singly. Females may be Induced to drop their young prematurely by excessive handling such 

 as transferring to new tanks, etc. 



The gestation period is irregular since it depends upon the temperature of the en- 

 vironment of these cold blooded forma. Psychological factors may also enter into the 

 picture, females dropping their young so early in their development that they cannot sur- 

 vive, or retaining them too long. For most live bearers the best temperature is about 

 75°F. , although some species can stand as much as 10°C. lower or higher. 



The young must be caught In traps, or provided with hiding places in vegetation, or 

 the adults must be removed because there is a tendency for them to eat their young almost 

 immediately. Since the young are bom at an advanced stage, these fish are the easiest to 

 raise in large numbers. Infusorlan food is too small for them and they must be put on a 

 diet of chopped white worms (Enchytrae) or small Daphnia. The adults are good eaters, ac- 

 cepting almost anything whether at the surface, dropping, or on the bottom. Species should 

 be segregated because there is frequent interbreeding among live bearers, particularly be- 

 tween the Sword tails and Platys. Live bearers are generally omnivorous. 



From the standpoint of early embryology these fish are not so satisfactory, but there 

 are numerous experimental approaches that are yet to be made on these forms. 



1. Leblstes retlculatus, the common Guppy. The Gold Guppy and the Black Tall Guppy 



are very good. 



2. Gambusia affinls. breed at 5-10 week intervals, called Mosquito fish from southern 



U.S. Is pugnacious and cannibalistic. 



5. Xlphophorus . the Swordtalls. Red or Green Swordtails very good. These may be 

 hybridized with the Platys. (Species helleri most common.) 



k. Platypoecilus maculatus (150 patterns), the multicolored Platy brought to the U.S. 

 from Mexico by Dr. Myron Gordon and distributed widely by him. The mutants Red, 

 Blue, and Gold Crescent are all excellent. Female may drop as many as 60 young 

 at a time, at monthly interval^. P. varlatus is found in at least 20 patterns. 



5. Molllenisis latipinna . the Sailfin Molly. The Perma Black Molly is very common 

 and entirely satisfactory. Breeds at 5-10 week intervals. PredcTiinantly herbi- 

 vorous. Require large aquarium and heavy aquatic greens in which the young can 

 hide during growth. 



