Key to genera of the Gyrodactylidae from African freshwater fish

1 (2) Opisthaptor with 16 marginal hooks of one type ...... 3

2 (1) Opisthaptor with 16 marginal hooks of differing morphologies; five pairs of marginal hooks with large falculate sickles and three pairs of smaller hooks with well articulated sickles ….............................. Diplogyrodactylus

3 (4) Marginal hooks of one morphological type, but of differing sizes, length of each sickle being approximately equal in length to that of their handle ................................... ................................................... Tresunicidactylus gen. n.

4 (5) Marginal hook of one type and of equal size and equally distributed around the periphery of the opisthaptor........... 6 5 (4) Distribution of the marginal hooks unequal; 14 marginal hooks located along the posterior margin of the opisthaptor, two marginal hooks located on anterolateral lobes; ventral bar with two pairs of rods ....................... Macrogyrodactylus

6 (7) Opisthaptor with additional suction discs; ventral bar complex consists of an inverted U-shaped piece with two semi-attachedbars ........................... Mormyrogyrodactylus

7 (8) Hamuli with only one (inner) developed root ........... 9

8 (7) Hamuli with two developed roots; outer root conspicious ............................................. Afrogyrodactylus

9 (10) Bulbous MCO; MCO equipped with one apical spine and one to several rows of small spines; one pair of hamuli connected by a simple dorsal bar; ventral bar with or without anterolateral processes, ventral bar membrane present ........................................................... Gyrodactylus

10 (9) MCO muscular; MCO consists of central curved cone, muscular pouch armed with numerous small spines; one pair of hamuli with a notable constriction at the junction between the shaft and point regions on each hamulus; simple dorsal and ventral bars; parasite on Citharinidae .. Citharodactylus