Gyrodactylus rasini Lucký, 1973

Rubio-Godoy, Miguel, Paladini, Giuseppe & García-Vásquez, Adriana, 2010, Gyrodactylus jarocho sp. nov. and Gyrodactylus xalapensis sp. nov. (Platyhelminthes: Monogenea) from Mexican poeciliids (Teleostei: Cyprinodontiformes), with comments on the known gyrodactylid fauna infecting poeciliid fish, Zootaxa 2509, pp. 1-29 : 23

Gyrodactylus rasini Lucký, 1973

( Figure 24 ; Tables 4 and 7)

Type host: Xiphophorus hellerii Heckel (“green swordtail”, “cola de espada verde”).

Site of infection: Gills.

Type locality: Not known.

Type material examined: Four paratypes ( BMNH 1994.11.24.13–18).

Comments: Type locality not known as the original description of G. rasini was based on parasites collected from aquarium fish ( Lucký 1973). The distribution range of the host X. hellerii spans the Atlantic coast of México, Belize, Guatemala and Honduras ( Froese & Pauly 2009). Specimens identified as G. bullatarudis by Harris (1986) were reassigned to G. r a s i n i by Richards et al. (2000), and their measurements are reviewed in Table 7.

While the marginal hooks sickles of G. r a s i n i can be readily discriminated from those of G. j a ro c h o sp. nov. based principally on the shape of the sickle base ( Figure 25 ), their discrimination from G. xalapensis sp. nov. should be supported by information drawn from other haptoral elements and the MCO. If the dimensions of the two latter species are compared, then the ranges for both species also closely coincide, G. xalapensis sp. nov. being towards the upper end of the range of measurements reported for each structure. Only the length of the dorsal bar of G. xalapensis sp. nov. is apparently longer than that of G. r a s i n i (av. 22.2 (19.4–25.7) c.f. 13– 19 ( Lucký 1973; Harris 1986; Richards et al. 2000)) - although the four paratypes re-measured in this study had on average 22.7 µm (21.5–23.4) long dorsal bars ( Table 4 ). When the hamuli of the two species are compared, those of G. xalapensis sp. nov. are more robust, with longer ventral bar articulation regions and more pronounced dorsal bar attachment points. Although the ventral bars of both species are also similar, the membrane of G. rasini is more rhomboid in shape while that of G. xalapensis sp. nov. is lingulate. The armature of the MCO differs between the two species. The MCO of G. rasini is observed to possess a large spine facing 5–6 small spines (current study; 4–7 in the literature). The MCO of G. xalapensis sp. nov., by comparison, possesses a large spine facing 2 medium-sized, upwardly pointing, terminal spines and 2 small, central spines. Given the morphological similarity of these two species, PCA was used to investigate whether they formed discrete clusters ( Figures 30 , 31 ). The first PCA ( Figure 30 ), which included all specimens considered in this study, suggested some overlap between the two gyrodactylids (labelled d and m). The subsequent removal of G. costaricensis , G. gambusiae , G. j a ro c h o sp. nov., G. milleri and G. turnbulli and the re-analysis of the remaining specimens, indicated that G. r a s i n i and G. x a l a p e n s i s sp. nov. formed discrete groups ( Figure 31 ). The component loadings determined for each variable for the second PCA indicated that the hamulus point curve angle and the lengths of the marginal hook and its shaft are key to the separation of G. rasini from G. xalapaensis sp. nov. through Factor2 ( Table 5 ). This is confirmed when the average values for each of these variables is considered (i.e. 13.5° (hamulus point curve angle), 22.8 µm (marginal hook total length) and 17.5 µm (marginal hook shaft length) for G. r a s i n i and 6.7°, 25.8 µm and 20.9 µm for G. xalapensis sp. nov., respectively) (see Tables 3 and 4 ).

Figures

FIGURE 30. Principal Components Analysis plot (Factor 1 vs Factor 2) of the 13 point-to-point measurements made on 45 gyrodactylids collected from a range of poeciliid hosts. Separation of the specimens is principally influenced by the hamulus total length (HTL), shaft length (HSL), point length (HPL) and aperture distance (HA) acting along Factor 1 in a negative direction, and the inner (CosIHAA) and outer (CosHAA) hamulus angles acting along Factor 1 in a positive direction. The total length (MHTL) and the shaft length (MHSL) of the marginal hook are key variables in the separation of specimens along Factor 2. The raw ellipses highlight the specimens of Gyrodactylus xalapensis sp. nov. from Heterandria bimaculata Heckel (1), and Gyrodactylus jarocho sp. nov. from Xiphophorus hellerii Heckel (2). Plot codes: a. Gyrodactylus bullatarudis Turnbull, 1956 from Poecilia mexicana Steindachner; b. G. bullatarudis from X. hellerii; c. G. j a ro c h o sp. nov. from X. hellerii; d. G. xalapensis from H. bimaculata; e. G. bullatarudis paratype from Poecilia sphenops Valenciennes; f. Gyrodactylus costaricensis Kritsky & Fritts, 1970 from P. sphenops; g. Gyrodactylus gambusiae Rogers & Wellborn, 1965 from Gambusia affinis Baird & Girard; h. Gyrodactylus pictae Cable, van Oosterhout, Barson & Harris, 2005 from Micropoecilia (= Poecilia) picta Regan; i. Gyrodactylus turnbulli Harris, 1986 from Poecilia reticulata Peters; j. Gyrodactylus poeciliae Harris & Cable, 2000 from Poecilia caucana Steindachner; k. Gyrodactylus milleri Harris & Cable, 2000 from P. caucana; l. Gyrodactylus cytophagus Paperna, 1968 from Aplocheilichthys pumilus Boulenger; m. Gyrodactylus rasini Lucký, 1973 from X. hellerii.

FIGURE 31. Principal components analysis plot (Factor 1 vs Factor 2) of Gyrodactylus bullatarudis Turnbull, 1956, Gyrodactylus cytophagus Paperna, 1968, Gyrodactylus poeciliae Harris & Cable, 2000, Gyrodactylys rasini Lucký, 1973 and Gyrodactylus xalapensis sp. nov. (13 ln - transformed variables; n = 29 specimens). The specimens of G. xalapensis sp. nov. (ellipse 1) are clearly separated from G. rasini (ellipse 2). Separation of the specimens is effected by the several hamulus variables acting along Factor 1 (total length (HTL), shaft length (HSL), point length (HPL), aperture distance (HA), distal shaft width (HDSW) and the proximal shaft width (HPSW )) and by point curve angle of the hamulus (CosHPCA), the total length (MHTL) and shaft length (MHSL) of the marginal hook acting through Factor 2. Plot codes: a. G. bullatarudis from Poecilia mexicana Steindachner; b. G. bullatarudis from Xiphophorus hellerii Heckel; d. G. xalapensis sp. nov. from Heterandria bimaculata Heckel; e. G. bullatarudis paratype from Poecilia sphenops Valenciennes; j. G. poeciliae from Poecilia caucana (Steindachner); l. G. cytophagus from Aplocheilichthys pumilus (Boulenger); m. G. rasini from X. hellerii.

FIGURES 15 – 29. A size invariant comparison of the marginal hook sickles of two new species of Gyrodactylus with the nine species previously recorded infecting poeciliids. 15. Gyrodactylus milleri Harris & Cable, 2000 (re-examination of the small, common form of marginal hook); 16. Overlay of G. milleri with G. j aroc h o sp. nov. (broken line); 17. Overlay of G. milleri with G. xalapensis sp. nov. (broken line); 18. Gyrodactylus pictae Cable, van Oosterhout, Barson & Harris, 2005 (re-examination); 19. Overlay of G. pictae with G. ja ro c ho sp. nov. (broken line); 20. Overlay of G. pictae with G. xalapensis sp. nov. (broken line); 21. Gyrodactylus poeciliae Harris & Cable, 2000 (re-examination); 22. Overlay of G. poeciliae with G. jaroc h o sp. nov. (broken line); 23. Overlay of G. poeciliae with G. xalapensis sp. nov. (broken line); 24. Gyrodactylus rasini Lucký, 1973 (re-examination); 25. Overlay of G. r a s i n i with G. j a ro c ho sp. nov. (broken line); 26. Overlay of G. rasini with G. xalapensis sp. nov. (broken line); 27. Scanning electron micrograph of Gyrodactylus turnbulli Harris, 1986 from Andrew P. Shinn’s collection (re-examination); 28. Overlay of G. turnbulli with G. j a ro c ho sp. nov. (broken line); 29. Overlay of G. turnbulli with G. xalapensis sp. nov. (broken line). Scale bars = 3 µm.