Rivulus elegans

• Notes on Aphyosemion elegans and the "Madimba" Strain Anthony Conrad 182

• Aphyosemion elegans, A Review of the Group — Technical Paper No. 7 J. J. Scheel 237

• Aphyosemion elegans (Boulenger 1899) — 141

• just prior to a normal hatch. This point is easily discerned because at this time the eggs are almost totally black. Usually, 60% of the eggs hatch within 20 days but the remaining "sticking" eggs take a total of one to two months to hatch (if they do at all!). Since a large number of these die in the shell (from starvation), various forced hatching techniques have been tried. Methods using infusoria did not work; in fact, a good number of the usually-resistant eggs fungused. Bubbling carbon dioxide into the container did not harm the eggs but it pro- duced no results. All attempts to break open the hard shell with a needle resulted in piercing the embryo. Finally, aeration as strong as possible which tended to roll the eggs about the bottom of their con- tainer without actually lifting them off, was tried. It was found that about 45 minutes of this treatment produced some hatchings within a half-hour. I believe that it is the vibration rather than the increase in oxygen content of the water that forces these hatches. Several months after discovering this technique, I learned that a friend was using another method to hatch "sticking" eggs of this species. He simply took them for a short ride in his car, placing them on the floor boards. The vibration hatched a large percentage everytime! All fry hatched with aeration were normal, with a slight yolk sac as u s u a l , and were ready to take newly-hatched brine shrimp the following day. Another strain of this species was obtained under the name of "Rivulus elegans" (the species was mistakenly called R. agilae, too) in the form of 20 eggs. These subsequently all hatched on the same day and thereafter, each hatching from succeeding generations of this strain produced no "sticking" eggs. All hatchings were within a 5 day spread with the maximum percentage usually on the 15th day (at an average temperature of 73 o F). When the two strains were crossed, "sticking" eggs were again encountered but nowhere near the percent- age obtained from the original stock. The young proved to be normal in all respects and tended to have the muted coloration of the "elegans" strain. Sexing the fry is an easy matter, for the females develop a defina- ble ocellatus spot when about ½ inch long. This is in about three weeks. Young fish begin to show the intense coloration of fully mature speci- mens when approximately 1½ inches. Given adequate room, live foods and weekly partial water changes, this can be accomplished within

• A REVIEW OF THE ELEGANS COMPLEX

• AS SOCIA TE EDITOR/ A Review of Aphyosealon elegans Group John Brill. Jr
• A Review of Aphyosemion elegans Group J.J. Scheel 178

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