Tylochromis praecox Stiassny 1989

Parasites of Tylochromis praecox

From Tylochromis praecox, C. bixlerzavalai n. sp. and C. omari n. sp. are described. New species were expected as no monogeneans had yet been described from T. praecox. Furthermore, all dactylogyrids from species of Tylochromis mentioned in the literature are considered strict specialists [14, 23, 35, 36], meaning, they occur on a single host species. In those studies, representatives of Tylochromis were caught in low numbers and restricted to a single host species. In Lower Congo, Tylochromis labrodon Regan, 1920 and Tylochromis lateralis (Boulenger, 1898) occur further upstream and are sympatric, but not with T. praecox [43]. It would be worthwhile to investigate whether C. bixlerzavalai n. sp. and C. omari n. sp. occur on these hosts as well, to see if these parasites are all strict specialists or if they only appear to be so because of biogeographical barriers. The ancestral state for host-specificity within Cichlidogyrus / Scutogyrus is intermediate specialism [21]. Species of Cichlidogyrus that infect species of Tylochromi s are shown to be ancestral to all others within Cichlidogyrus / Scutogyrus [19–21, 37, 48], similar to Tylochromis (and Tylochromini) being ancestral to all African cichlids except Heterochromis [8, 43]. We could hence hypothesize that species of Cichlidogyrus that infect species of Tylochromis are intermediate specialists when sympatric host congeners are present in the area. It has to be noted that only Cichlidogyrus pouyaudi Pariselle & Euzet, 1994 was included as a representative that infects species of Tylochromis in the phylogenies of Cichlidogyrus / Scutogyrus [19–21, 37, 48]. However, we expect species of Cichlidogyrus that infect species of Tylochromis to form a monophyletic clade based on the morphological similarities between the species [37]. Both new species showed typical morphological characters of their congeners that infect species of Tylochromis, such as less developed auricles on the dorsal transverse bar, an accessory piece that does not connect directly to the basal bulb of the penis, and a spirally-winding penis [23, 28]. Following the phylogeny, we assume these morphological characters to be ancestral to all others within Cichlidogyrus / Scutogyrus [37].