Neotropical Monogenea. 15. Dactylogyrids from the gills of Brazilian Cichlidae with proposal of Sciadicleithrum gen. n. (Dactylogyridae)

Abstract

Sciadicleithrum gen. n. is proposed for dactylogyrids possessing overlapping gonads, a coiled cirrus with clockwise rings, unmodified anchors, a ventral bar with 2 umbelliform membranes or cavities on the anterior bar margin, and similar hooks with undilated shanks and erect thumbs. The following species are described from neotropical cichlids: Gussevia asota, G. astronoti, and G. rogersi spp. n. from Astronotus ocellatus (Cuvier); Sciadicleithrum undnatum (type), S. umbilicum, and S. ergensi spp. n. from Cichla ocellaris Bloch and Schneider; S. tortrix sp. n. from Uaru amphiacanthoides Heckel; 5. iphthimum sp. n. from Pterophyllum scalare (Lichtenstein); and S. geophagi sp. n. from Geophagus surinamensis (Bloch). Urocleidoides variabilis Mizelle and Kritsky, 1969, Urocleidus aequidens Price and Schlueter, 1967, and Urocleidus cavanaughi Price, 1966, are transferred to Sciadicleithrum. Ancyrocephalus kostomarovi Lucky, 1973, is considered a junior subjective synonym of S. variabilum comb. n. Prior to the revision of Urocleidoides by Krit- sky et al. (1986), the genus as emended by Mizelle et al. (1968) contained 30 neotropical species from fishes representing 4 teleost orders. Kritsky et al. (1986) considered the taxon polyphyletic and proposed limiting the genus to monogeneans possessing a sinistral vaginal sclerite, overlap- ping gonads, counterclockwise cirral rings, sim- ple anchors, and hooks (pairs 1 and 5 usually reduced) with enlarged shanks. Gussevia Kohn and Paperna, 1964, was resurrected from syn- onymy with Urocleidoides for some dactylogy- rids from neotropical cichlid hosts. This revision resulted in 22 (1 from a cichlid host) of the orig- inal Urocleidoides species without final generic placement (status incertae sedis). In the present paper, 9 new ancyrocephalines from cichlid hosts are described, Sciadicleithrum gen. n. is pro- posed, and Urocleidoides variablis Mizelle and Kritsky, 1969, Urocleidus aequidens Price and Schlueter, 1967, and Urocleidus cavanaughi Price, 1966, are transferred to Sciadicleithrum. As a result, only Gussevia Kohn and Paperna, 1964, Trinidactylus Hanek, Molnar, and Fernando, 1974, and Sciadicleithrum gen. n. currently in- clude species infesting neotropical cichlids; how- ever, the monotypic Trinidactylus from Cichla-