View Full Version : Wami Tilapia O. hornorum

02-15-2009, 02:12 PM
This is a pretty rare tilapia. Very aggressive and quite dark in color. I have to remove the top lip of the males to keep them from killing the females. The females are slow to mature and breed in my experience, but the males will breed at just 4 months.

This tilapia is unusual in that rather than using the XX/XY system for sex determination, like we do, it uses a ZZ/ZW chromosome system with the males being ZZ and the females being ZW. The O. mossambica uses the XX/XY system with females being XX. A cross between the ZZ male and the XX female produces offspring that are all ZX and this turns out to be male hybrid fish. Being hybrids they also grow very quickly.

Mike Sipe has been breeding these for body shape for over 30 years. The hybrids retain the male body shape and fast growth. His tests say the hybrids can reach one kilo in under 9 months.

This picture shows a larger improved hornorum in contrast with a batch of unimproved fish:
http://s25.photobucket.com/albums/c70/b ... proved.jpg (http://s25.photobucket.com/albums/c70/badflash/tilapia/?action=view&current=improved.jpg)

Male breeders are quite expensive at around $150 each, but it gives you the ability to produce thousands of fry a months that are nearly all male and not use hormones for sex reversal.

04-29-2009, 02:51 PM
So how are these as far as a pure strain for growth and size for marketability if you don't hybridize them? I read they originally came from Zanzibar ...... You say they are very aggressive ...... do they eat the young a lot, so you'd have to separate the adults soon after hatching? more info please :)

The native range of the Wami tilapia is Zanzibar, a large island off the coast of Tanzania in East Africa, and the Wami River drainage on mainland Tanzania opposite Zanzibar (Trewavas 1968).
Formerly designated Tilapia hornorum Trewavas, this species should now be named T. urolepis Norman (Robins et al. 1991), and the subspecies from California identified as T. u. hornorum (Courtenay et al. 1991). The hybrid form (T. mossambica x T. urolepis) is a common aquacultural fish called the red tilapia. The closely related T. u. hornorum and T. mossambica are very similar in appearance. For many years the former was considered the Zanzibar strain of the latter, which was termed the Java strain; the hybrid offspring was known as the Malacca hybrid (McConnell 1966; St. Amant 1966b). The two species were first recognized as distinct by Trewavas (1968).

The Wami tilapia is a tilapiine cichlid that grows to over 20 cm in length and is considered a useful food fish in Tanzania and the island of Zanzibar, where it may have been introduced by man. It is tolerant of brackish water and grows well in saline pools, making it particularly suitable for aquaculture by communities living close to the sea. Like other tilapia it is an omnivore and will feed on algae, plants, small invertebrates, and detritus. The common name refers to the Wami River.

Formerly considered a separate species, it is at present merged wioth the Rufigi tilapia and thus the scientific name is Oreochromis urolepis hornorum. The obsolete scientific name Tilapia hornorum is also still seen not infrequently. However, mtDNA sequence analysis has found that the mitochondrial genome is possibly very similar to that of Sarotherodon galilaeus (Nagl et al. 2001); it might be moved to Sarotherodon based on these results. On the other hand, hybridization is quite common in tilapiines and hybrids even between not too closely related species may be fertile.

In captivity, Wami tilapia have been hybridised with the Mozambique tilapia (Oreochromis mossambicus). The resulting fish produce broods almost entirely consisting of males. Male tilapia grow faster and to a more uniform size than females, making them particularly useful for aquaculture[1]. Note that based on the mtDNA study by Nagl et al. (2001), the Mozambique and Wami tilapias do not appear to be closely related.

3 possibilities may explain this discrepancy: Either, the Wami tilapia and its closest relatives (such as the Rufigi and Blue Tilapias) belong into Sarotherodon. Alternatively, they are correctly placed in Oreochromis but their ancestors hybridized with some ancestral Sarotherodon. Given that only a single specimen was analyzed, it is theoretically also possible that the Wami tilapia is a cryptic species complex. This is less likely because cryptic speciation requires barriers to gene flow which in the tilapiines are not well-developed.

The mtDNA data of Klett & Meyer (2002) places the Rufigi tilapia into Oreochromis (though not close to the Mozambique Tilapia, but rather to Oreochromis amphimelas). This would seem to support the second hypothesis - maternal gene flow from Sarotherodon to Oreochromis; whether this is correct or not, it amply illustrates that mtDNA sequences are not a reliable indicator of phylogenetic relationships in these fish.

04-29-2009, 08:41 PM
They are more agressive Male to female. All tilapia I've seen will eat fry given the chance. They get conflicted between the mouth brooding and hunger. Most male horonorum need to have their upper lip removed to keep them from killing the females. This is not needed in pond culture, but in cage or aquarium culture, un-willing females can not get away. Keeping 6 or more females with them is a workable alternative, as some one is nearly always receptive.

10-14-2010, 08:24 PM

01-23-2016, 11:19 AM
Hello Badflash,
I know this post is almost 7 years old, but Im very interested in learning more about the Wami Tilapia and getting a breeder colony, the pics of the tilapia that you have on your photobucket account are they the Wami's at full size?