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Lake Tanganyika cichlids — species, locations & maps
tanganyika.si
Lake Tanganyika cichlids — species, locations & maps.
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The provisional name “Cygnus” derives from the Latinised Greek word for swan. The species was discovered in 1988 by Walter Dieckhoff and later named by Ad Konings. Early introductions to the aquarium hobby included a presentation by Konings at the 7th international cichlid exhibition in Antwerp in 1989, followed by exports to the USA and Sweden in 1991, and later to the Netherlands and Germany. Specimens for these early exports were collected at Mwila Island, at the north-eastern corner of the Kipili archipelago. Prior to export, the fish were allowed to spawn to confirm the yellow juvenile coloration, resulting in a brood of at least 30 juveniles in early 1991.
Geographic colour variation is pronounced along the Tanzanian range. At the northern limit around Silaf Rocks at Cape Mpimbwe, adults may show a subtle yellowish to reddish-yellowish head. Around the Kipili area, the Mwila Island variant is noted for yellow pectoral fins. Further south, between Ninde and Chisanze Point (possibly extending to Kalandasi Point near Msamba), populations may develop an orange-brown body and an orange caudal fin, including the Kisi Island variant; these fish may show tiny blue dots on the caudal fin, with the caudal-fin lobes grading from orange to yellow posteriorly. In these southern variants, the soft part of the dorsal fin may also show bright orange and sometimes tiny blue dots.
Many variants occasionally display a bicoloured dorsal-fin margin—blue anteriorly and yellow posteriorly—interpreted as a remnant of juvenile coloration and not typical of fully adult fish. Juveniles and semi-adults often show a short dark horizontal stripe behind the eye and a dark vertical stripe at the edge of the operculum, a combination also observed in several N. brichardi variants. South of Msamba, both juveniles and adults commonly display a yellow pectoral spot, which becomes especially conspicuous between Popo Point and Wampembe, including Popo Rocks and Fulwe Rocks, and is reported to be even stronger around Molwe. In southern Kala Bay, including Kalala Island and several islands farther south, the pectoral spot is not conspicuous and the posterior dorsal-fin edge seen in semi-adults becomes black. Farther south again, between Lwasase Point and the Lwazi River, a thick bright yellow margin may adorn the posterior part of the dorsal fin and the upper part of the caudal fin.
Ontogenetic changes have been reported in some natural populations: large or old males may develop a deeper body and a nuchal hump, confirmed in populations between Cape Mpimbwe and Mtosi Bay. Behaviourally, N. sp. “Cygnus” does not aggregate in schools and produces very small broods, typically 2–3 juveniles in aquaria and rarely more than four observed with a pair in the wild, although one documented spawn produced at least 30 juveniles. In shaded rocky habitats it may superficially resemble N. furcifer, N. timidus, and especially juveniles or subadults of N. christyi. Within the lake, it shares parts of its habitat with N. savoryi, N. brichardi, and N. pulcher.
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