Nothobranchius ocellatus

• Species profile: Nothobranchius ocellatus (Seegers, 1985) Brian R. Watters 118

• Dr. Harry Specht Dr. Jim Thomerson Nothobranchius ocellatus (Seegers, Kindercare in a Screwbox
• Nothobranchius ocellatus Finn Larsen 186

No table-of-contents lines available.

• ish-green and are edged in black. They have a few of the reddish body spots at their base and more faintly, also along the trailing edges of these fins. The caudal fin is not as fan-shaped as those of related rivulids, the rear edge being more straight than circular and quite variable in pattern. Generally, it is black along the top and bottom edges. Beginning at the caudal peduncle, just below the top black edge, is a yellowish-green horizontal streak which fades into the dark-gray central region below. The end of the tail fin has a vertical white band between the top and bottom black edges and is the most eye-catching feature of the species. The males originally imported into this country in 1956 had a bright orange streak instead of the white one, hence the popular name, "goldentail rivulus." The author has seen males which had a completely-black border around the entire caudal fin, the center being a dark gray. They were found in a wild shipment of normally-colored males. Females are gray in color, overlaid with black spots that gather in places all over the body, presenting a mottled appearance. Belly region, throat and jaw are pink-white and the typical rivulus ocellatus is visible on the upper caudal peduncle. The dorsal and caudal fins present the same mottled pattern, the ventrals are clear and the anal fin is the same as described for the male but muted in coloration. Keeping the species is no problem as they will greedily accept dry foods, chopped beef heart, shrimp, etc., as well as live foods. They do well at temperatures between 68 to 85° F and very seldom do males viciously drive the females during spawning. Water conditions can vary widely. The author has kept them in water varying from 6.2 to 7.3 pH and 0 to 9 DH with no apparent discomfort. They make good community tank killies with the larger top-spawners such as Aplocheilus lineatus, Pachypanchax homolonotus, P. playfairii, Epi- platys sexfasciatus, etc. They are, however, occasional jumpers so their tank should be completely covered. Credit goes to Albert J. Klee for introducing the scientific name of this species to the hobby when in 1959, his search for its taxonomic description proved fruitful and it was found to have been described by Fowler in 1941. Spawning R. milesi is easy although the breeders are avid egg- eaters. Unless many thick mops are used, don't expect more than
• 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

No table-of-contents lines available.

No table-of-contents lines available.

No table-of-contents lines available.

No table-of-contents lines available.