360 FISH FOR EXPERIMENTATION 



The female turns a brilliant pink in color when about to breed, which may be as frequently 

 as every 7 to 10 days at 80°-84°F. The fish generally attach their eggs to the bottom of 

 the tank, first excavating a clear circular area in the sand or gravel. Taking advantage 

 of this tendency it is well to place, on the bottom of such a tank, broken pieces of a 

 flower pot or crockery, onto which the fish will attach their eggs. These pieces of 

 crockery may then be removed and the early development studied. The fish develop very 

 rapidly (See Noble, Kumpf, and Billings, 1938). 



f. The Sea-horse, Hippocampus Hudsonius 



Since it is now known that the brine shrimp, whose eggs can be kept in a dry condition for 

 a long period, can be cultured in salt water and then fed to sea horses, these curious 

 fish can now be maintained in the fresh-water laboratory and the unique method of rear- 

 ing the young studied. 



Sea water may be obtained by direct shipment from the seashore, or Turks Island Salt 

 may be added to distilled water to simulate sea water. Sand is placed in the bottom of 

 the 4 to 6 gallon all-glass aquarium, adequate for one pair of fish. The original salt 

 water line must be indicated on the aquarium and this line maintained by the semi-weekly 

 addition of distilled water to replace that lost by evaporation. Direct and intense (sun) 

 light should be avoided. (See references by Breder, MacGinitie and Chin) 



Sea horses may be fed entirely on small Guppyi, Mosquito Larvae, Enchytrea (white 

 worms) Tubifex (red worms), and brine shrimp. Fresh water food cannot survive for 

 long in a salt water aquarium, hence there must be no overfeeding. Brine shrimp live 

 naturally in the same environment as the sea horses, and are excellent food for the fish. 

 Brine shrimp do better at higher temperatures (up to 1 00° F. ) and in slightly hypotonic 

 sea water. The occasional addition of some wilted lettuce is advised. The success of a 

 Sea Horse colony depends largely upon the success of a Brine Shrimp culture as food. 



The female sea horse deposits her fertilized eggs in the brood pouch of the male where 

 they are incubated for from 6 to 7 weeks. The breeding period is March through June. 

 The young fry are fed on Protozoon infusions or on the smallest of the brine shrimp. 



Little is known of the normal development of these eggs and embryos, but since the adults 

 can now be reared in the inland laboratory, it is expected that they will provide new 

 fruitful material for investigation. 



g. The Japanese Medaka, Oryzias Latipes 



These fish may be kept in groups of 50 in ten gallon tanks, and in such a colony egg lay- 

 ers will be found almost daily throughout the year. The ratio of males to females should 

 be about 2/1. Breeding females may be isolated with (2) males in small half-gallon fish 

 bowls, covered with wire screen to keep them from jumping out. Vegetation should be 

 reduced so that the eggs will not be covered with algae. (See section on Reproductive 

 Physiology and Embryology of Oryzias for further details, and see papers by various 

 authors such as Goodrich, Robinson, Solberg, and Waterman.) 



CHARACTERISTICS OF THE ADULT FISH: ORYZIAS LATIPES 



Oryzias latipes has a wide distribution in China and Japan except in the mountains. It is 

 found in ponds, stagnant pools, running streams and rice fields. The adults measure 

 from 20 to 40 mm. in length with an average of about 30 mm. The wild species is 



* Available through Bcldt's Aquarium, 2141 Crescent Avenue, St. Louis, Missouri. 



