Faustula keksooni ( MacCallum, 1918 ) Poche, 1926

Dronen, Norman O., Blend, Charles K., Mohammed, Essa T. & Bannai, Majid, 2021, Reconsideration of the species assigned to Faustula Poche, 1926 (Digenea: Microphalloidea) with the proposal of five new genera in the Faustulidae Poche, 1926, Zootaxa 5027 (2), pp. 231-253 : 237

Faustula keksooni ( MacCallum, 1918) Poche, 1926 (type species)

(Syn. Eurema keksooni MacCallum, 1918 nec Hübner, 1820)

( Fig. 1 ; forebody of type species reconstructed based on the remaining posterior aspect of the oral sucker, the general appearance of the forebody in the type specimen and to some extent the basic morphology of known species of Faustula ).

Type host: Gills of a small unspotted ray, most likely Potamotrygon motoro (Müller & Henle) (Potamotrygonidae) .

Type locality: Off Singapore .

Remarks: Faustula keksooni differs from all other described species in the genus by having a larger body (2,800 × 1,200), a larger ventral sucker (285; 10% of body length), a longer cirrus sac (640; 23%), a wider ovary (380), wider testes (mean width 255), a longer postovarian space (1,000; 36%) and the uterus ends well short of the posterior extremity. Given the larger body size of the type specimen, some measurements relative to body length show similar morphometric percentages and sometimes there are similarities in morphometric ratios (see Table 1). The combination of a median or nearly median, postbifurcal genital pore and a cirrus sac that surpasses the ventral sucker posteriorly to some extent is shared only with F. gangetica . Faustula gangetica differs from F. keksooni by having a broadly oval body vs a more lingulate body; more extensive vitelline fields (vitelline follicles distributed from the level of the posterior end of the esophagus to about the midlevel of ovary vs being distributed from just posterior to the level of the intestinal bifurcation to about the midlevel of the testes); a shorter esophagus (160–180; 10–12% vs 370; 13%) and generally larger eggs (16–25 × 12 vs 16–20 × 9–11). MacCallum (1918) noted that Faustula keksooni (as Eurema keksooni MacCallum, 1918 ) was from the gills; however, the specimen was found at the bottom of the dissecting dish after the gills of the small ray were washed and it may have come from the gullet or mouth. We believe it was likely contamination from a previous autopsy or an accidental infection.

Figures

FIGURES 1–2. Diagrammatic illustrations of faustulids (ventral views): 1. Faustula keksooni (MacCallum, 1918) Poche, 1926 largely based on Price (1938); type species of Faustula Poche, 1926. 2. Faustula basiri Hafeezullah & Siddiqi, 1970 based on Hafeezullah & Siddiqi (1970). Abbreviations: C, cecum; E, esophagus; F, vitelline follicles; G, genital pore; L, large glandular cells in cirrus sac; O, ovary; OS, oral sucker; P, pharynx; S, seminal vesicle; T, testes; U, uterus; V, excretory vesicle; VS, ventral sucker.