Folia Parasitologica 54[2] 129-140 (2007) | DOI: 10.14411/fp.2007.018

A revised description of Gyrodactylus cichlidarum Paperna, 1968 (Gyrodactylidae) from the Nile tilapia, Oreochromis niloticus niloticus (Cichlidae), and its synonymy with G. niloticus Cone, Arthur et Bondad-Reantaso, 1995

Adriana García-Vásquez¹, Haakon Hansen^2,3, Andrew P. Shinn¹

¹ Institute of Aquaculture, University of Stirling, Stirling FK9 4LA, UK

² Natural History Museum, Department for Zoology, University of Oslo, P.O. Box 1172, Blindern, NO-0318 Oslo, Norway

³ National Veterinary Institute, Section for Parasitology, P.O. Box 8156 Dep., NO-0033 Oslo, Norway

A recent infestation of Gyrodactylus cichlidarum Paperna, 1968 on yolk sac fry of Nile tilapia, Oreochromis niloticus niloticus (L.), in an isolated aquarium system in the UK resulted in high mortalities and provided an opportunity to study this species in greater detail. A tentative identification was made using the measurements and drawings of the ventral bar and hamuli provided in the original description; however, details on the morphology of the marginal hooks were lacking. A comparison of the gyrodactylid material collected from O. n. niloticus with the holotype of G. cichlidarum, the only known available specimen, from Mango tilapia, Sarotherodon galilaeus galilaeus (L.), confirmed its identity. Proteolytic digestion and image analysis of the opisthaptoral hard parts were used to obtain tissue-free, accurate measurements as part of a complete revised description of G. cichlidarum. Further, a comparison of G. cichlidarum from both hosts with the holotype and several paratypes of Gyrodactylus niloticus Cone, Arthur et Bondad-Reantaso, 1995 cited as parasitizing captive stocks of Nile tilapia in the Philippines revealed the two species to be synonymous. An 803 bp fragment of the ribosomal internal transcribed spacers 1 and 2 and the 5.8S was obtained and is provided with the revised description. This is the first DNA sequence from a Gyrodactylus species originating from the African continent. The sequence is very divergent from other species in the genus and only the 5.8S sequence places it unambiguously in the genus Gyrodactylus. In addition to G. cichlidarum, two specimens of another morphological similar species of Gyrodactylus were also found on the UK held stock of O. n. niloticus. These latter specimens, Gyrodactylus sp., differed from G. cichlidarum in having a longer hamulus point with a smaller hamulus aperture and possessing marginal hook sickles that had a shorter shaft with a longer point giving the sickles a more rounded, closed appearance.

Keywords: Gyrodactylus cichlidarum, parasite, tilapia, taxonomy, cichlid

Received: December 31, 2005; Accepted: January 8, 2007; Published: June 1, 2007  Show citation