Gyrodactylus milleri Harris & Cable, 2000

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 : 21-22

Gyrodactylus milleri Harris & Cable, 2000

( Figures 15 , 47–52 ; Tables 4 , 6 and 7)

Type host: Poecilia caucana Steindachner (“Cauca molly”, “piponcita”).

Site of infection: Body surface.

Type locality: La Concepción, Venezuela.

Type material examined: Holotype ( BMNH 1999.4.12.1).

Comments: The original description of G. m i l l e r i by Harris & Cable (2000) was based on three specimens and contained limited morphological measurements. We provide new measurements based on the holotype deposited in the BMNH (reg. no. 1999.4.12.1), although some morphological details were not visible as the specimen was bisected and mounted on two slides. Thus, the anterior pharynx, posterior pharynx and MCO were not visible. The holotype possesses three morphologically different marginal hooks of various sizes ( Figures 47–52 ): 10 small (S), 4 medium (M), 2 large (L) hooks (the exact measurements of the three types of marginal hooks are given in Table 6 , while the mean values are presented in Table 4 ). This is the second known species of Gyrodactylus to have noticeably different shaped and sized marginal hooks ( Figures 47–52 ). Previously, Gyrodactylus heterodactylus Rogers & Wellborn, 1965 collected from banded pygmy sunfish, Elassoma zonatum Jordan, was shown to possess marginal hooks of two different sizes ( Rogers & Wellborn 1965).

The PCA presented in Figure 30 shows three different points (labelled k) on the scatterplot, reinforcing the idea that G. milleri marginal hooks differ markedly within the same individual (as only the holotype was available, the specimen was measured and entered in PCA analyses as three individuals with the same hamuli measurements, but different marginal hooks, using data given in Table 6 ).

The marginal hook sickles of G. m i l l e r i are morphologically most similar to those of G. gambusiae and G. turnbulli - large, angular, open faced sickles, both of which can be readily discriminated from G. j a ro c h o sp. nov. and G. xalapensis sp. nov. ( Figures 16, 17 ). Figure 15 depicts and contrasts the sickles of the small marginal hooks of G. m i l l e r i, as these are the most abundant. Although the marginal hook sickles of G. milleri are morphologically similar to those of G. gambusiae and G. turnbulli , its discrimination from the other two species is possible by virtue of its three differently shaped and sized marginal hooks.

milleri Harris & Cable, 2000 (holotype BMNH 1999.4.12.1).

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.

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.

FIGURES 47 – 52. Light photographs and drawings of Gyrodactylus milleri Harris & Cable, 2000 (holotype), showing the three different sizes and morphologies of the marginal hook sickles. 47, 50. Small marginal hook sickle; 48, 51. Medium sized marginal hook sickle; 49, 52. Large marginal hook sickle. Scale bar = 3 µm.