Gyrodactylus xalapensis, Rubio-Godoy, Miguel, Paladini, Giuseppe & García-Vásquez, Adriana, 2010

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 : 11-16

Gyrodactylus xalapensis sp. nov.

( Figures 2 , 39–46 ; Table 3 )

Type host: Heterandria bimaculata Heckel (“twospot livebearer”, “guatopote manchado”). Site of infection: Fins.

Type locality: Río Pixquiac, Xalapa, Veracruz, México (19°28'39''N, 96°57'00''W). Type material: Eight specimens were studied for light microscopy. The holotype and three paratypes are deposited in the Parasitic Worm Collection at The Natural History Museum ( BMNH reg. nos. 2010.3.11.10 and 2010.3.11.11–13, respectively) London, UK. In addition, four paratypes are deposited in the Colección Nacional de Helmintos ( CNHE reg. no. 7131), Instituto de Biología, Universidad Nacional Autónoma de México, México City.

Notes: * Except soft body parts, which were measured from holotype and/or smaller sample sizes. 1Based on the measurement of a single specimen.

Abbreviations: TBL = total body length; TBW = total body width; OL×W = haptor length × width; APL×W = anterior pharynx bulb length × width; PPL×W = posterior pharynx bulb length × width; MCOL ×W (NoS) = male copulatory organ (MCO) length × width (number of small spines only - principal spine not included in the count); HTL = hamulus total length; HA = hamulus aperture distance; HPSW = hamulus proximal shaft width; HPL = hamulus point length; HDSW = hamulus distal shaft width; HSL = hamulus shaft length; HICL = hamulus inner curve length; HAA = hamulus aperture angle; HPCA = hamulus point curve angle; IHAA = inner hamulus aperture angle; HRL = hamulus root length; VBW = ventral bar width; VBL = ventral bar length; VBPML = ventral bar process-to-mid length; VBML = ventral bar median length; VBPL = ventral bar process length; VBMemL = ventral bar membrane length; DBL = dorsal bar length; DBW = dorsal bar width; MHTL = marginal hook total length; MHSL = marginal hook shaft length; MHSiL = marginal hook sickle length; MHSiPW = marginal hook sickle proximal width; MHToeL = marginal hook toe length; MHSiDW = marginal hook sickle distal width; MHA = marginal hook aperture; MHI/AH = marginal hook instep / arch height.

Etymology: Named after the city of Xalapa (Veracruz, México), from whose vicinity samples were taken.

Description: Body 262 (245–275) long; 68 (60–75) wide at the level of the uterus. Anterior bulb of pharynx 13.7 long, 30.4 wide; posterior pharynx bulb 12.9 long, 42.7 wide. Haptor spherical, 53 (50–55) long, 54 (50–58) wide. Male copulatory organ (MCO) observed on a single specimen, 11.9 long, 10.4 wide, spherical, armed with one large spine and a single ring of 4 spines (2 medium sized upwardly pointing terminal spines, 2 small central spines whose points face the large spine) ( Figure 46 ). MCO positioned off centre, posterior to the posterior pharynx bulb. Hamulus total length 47.2 (43.3–49.6); shaft length 31.3 (30.2– 32.6); point 21.4 (19.1–23.4) long with a 32.2° (28.6–36.3°) aperture; root proportionately short and approximately rectangular in lateral aspect, one third to half the diameter of the hamulus in the region of the dorsal bar attachment point; 11.9 (10.3–13.7) long ( Figures 39, 44 ). Ventral bar articulation points on the hamuli prominent. Dorsal bar attachment points small, anterior edge marks a sharp angle on union with hamulus. Dorsal bar 22.2 (19.4–25.7) long, 1.7 (1.1–2.3) wide; narrow at its union with the hamulus, the dorsal bar quickly thickens and gradually tapers towards the centre which is marked by a small median notch on the posterior edge ( Figures 39, 44 ). Ventral bar 30.7 (26.4–34.7) long; 30.3 (27.9–32.1) wide. Ventral bar processes prominent, broad, 10.9 (8.7–12.4) long; anterior edge of the processes join the ventral bar proper one quarter in along its length, posterior edge attaches to the lateral extremity of the ventral bar proper close to its posterior edge. Median section of the ventral bar proper rectangular. Ventral bar membrane lingulate, posterior edge rounded 15.0 (12.3–16.5) long; lateral margins not thickened, median zone of membrane striated ( Figures 39, 44 ). Marginal hook 25.8 (24.5–27.2) long; shaft length 20.9 (20.2–22.3); sickle proper 5.0 (4.7–5.3) long; sickle base slender; toe triangular, distance from tip to union with marginal hook shaft 1.6 (1.3–1.8) long; toe bridge proportionately long and gently forward sloping. Sickle heel pronounced, circular to square-ish; sickle proximal width 4.1 (3.5–4.4). Sickle shaft slightly angled forward; sickle point delicate terminating at a point beyond the line of the toe. Sickle distal width 3.4 (3.0–3.8); sickle aperture 4.3 (4.0–4.4) ( Figures 40–42, 45 ).

Notes: * Male copulatory organ, pharynx and marginal hook measurements taken from one paratype only; these structures were not visible on the second paratype; ** the ventral bar was not visible this specimen; *** pharynx and male copulatory organ not visible; 1Marginal hooks come in three different sizes (see Table 6 ). Measurements presented here were made on the small marginal hooks (n = 10) only, which were the most common in the single specimen of G. milleri .

Comments: This is the first gyrodactylid species to be described from H. bimaculata . Separation of the gyrodactylids parasitizing poeciliids is most effectively achieved using marginal hook sickle morphology and the discrimination of G. xalapensis sp. nov. from each of the already known species is commented upon under the comments section for each species. Gyrodactylus jarocho sp. nov. and G. xalapensis sp. nov., however, are described for the first time and can be easily separated on the morphology of the sickle base - approximately triangular in G. j a ro c h o sp. nov., trapezoidal in G. xalapensis sp. nov. The morphology of the MCO, when present, can also be used to discriminate G. j a ro c h o sp. nov. from G. xalapensis sp. nov. The MCO of G. jarocho sp. nov. is armed with one large spine facing 8 smaller, but differently sized spines, while the MCO of G. xalapensis sp. nov. is armed with one large spine facing 4 smaller sized spines the terminal two of which are larger and appear, in the single MCO-bearing specimen examined here, to be upwardly directed. The marginal sickles of G. xalapensis sp. nov. and G. r a s i n i are morphologically similar but the separation of these two species is possible using the size of the hamulus point curve angle and the lengths of the marginal hook and its shaft.

Figures

FIGURES 1 – 14. A size invariant comparison of the marginal hook sickles of two new species of Gyrodactylus with the nine species previously recorded infecting poeciliids. 1. Gyrodactylus jarocho sp. nov.; 2. Gyrodactylus xalapensis sp. nov.; 3. Gyrodactylus bullatarudis Turnbull, 1956 (re-examination); 4. Overlay of G. bullatarudis with G. j a ro c h o sp. nov. (broken line); 5. Overlay of G. bullatarudis with G. xalapensis sp. nov. (broken line); 6. Gyrodactylus costaricensis Kritsky & Fritts, 1970 (re – examination); 7. Overlay of G. costaricensis with G. j a ro c h o sp. nov. (broken line); 8. Overlay of G. costaricensis with G. xalapensis sp. nov. (broken line); 9. Gyrodactylus cytophagus Paperna, 1968 (reexamination); 10. Overlay of G. cytophagus with G. ja ro c ho sp. nov. (broken line); 11. Overlay of G. cytophagus with G. xalapensis sp. nov. (broken line); 12. Gyrodactylus gambusiae Rogers & Wellborn, 1965 (re-examination); 13. Overlay of G. gambusiae with G. j a ro c h o sp. nov. (broken line); 14. Overlay of G. gambusiae with G. xalapensis sp. nov. (broken line). Scale bars = 3 µm.

FIGURES 39 – 46. Gyrodactylus xalapensis sp. nov. from Heterandria bimaculata Heckel. 39. Light micrograph of the haptoral central hook complex showing the hamuli, the dorsal and the ventral bar (ventral view); 40 – 41. Light micrographs of the marginal hooks; 42. Light micrograph of the marginal hook sickle; 43. Light micrographs of the male copulatory organ (MCO); 44. Drawing of the central hook complex; 45. Drawing of the marginal hook sickle; 46. Drawing of the MCO. Scale bars: Figures 39 – 41 and 44 = 5 µm; Figures 42, 43, 45 and 46 = 3 µm.