Galactosomum erinaceum ( Poirier, 1886 ) Bittner & Sprehn, 1928

Karar, Yasser F. M., Blend, Charles K., Dronen, Norman O. & Adel, Asmaa, 2023, Towards resolving the problematic status of the digenean genus Astiotrema Looss 1900: Taxa excluded from Astiotrema (sensu stricto) with special reference to plagiorchioid genera closely related to the restricted concept of Astiotrema, Zootaxa 5284 (3), pp. 445-495 : 455

Galactosomum erinaceum ( Poirier, 1886) Bittner & Sprehn, 1928

( Fig. 9 )

(Syns. Distomum erinaceum Poirier, 1886 ; Distoma erinaceum Poirier, 1886 ; Distoma [ Dicrocoelium ] erinaceum [ Poirier, 1886] Stossich, 1892; Astiotrema erinacea [ Poirier, 1886] Stossich, 1904 [Malformed suffix]; Astiotrema erinaceum [ Poirier, 1886] Stossich, 1904)

Record. 1. Poirier (1886).

Remarks. Poirier (1886) described D. erinaceum to accommodate some immature specimens liberated from cysts and collected from the intestine of the short-beaked common dolphin, Delphinus delphis Linnaeus (Artiodactyla: Delphinidae ), in European waters of the North Atlantic Ocean. Stossich (1892) moved D. erinaceum into the subgenus Dicrocoelium Dujardin, 1845 within Distoma Retzius, 1786 . Looss (1899) noted that the immature specimens of D. erinaceum highly corresponded to the two known members of Astia Looss, 1899 nec Koch, 1879 (= Astiotrema ) (i.e., the type-species A. reniferum and A. impletum ) in all recognizable structural details, but no reassignment of D. erinaceum within this genus was proposed. Stossich (1904) reassigned D. erinaceum within Astiotrema as A. erinaceum and Nicole (1923) also followed this same approach. Jägerskîld (1908) and Odhner (1911) pointed out the similarity and close relationship of this form with monostomids (i.e., members of Monostoma Zeder, 1800 [syn. Monostomum Creplin, 1829 ]) such as Galactosomum (particularly Galactosomum lacteum [Jägerskîld, 1896] Looss, 1899) and other closely related forms despite the difference in host groups; A. erinaceum has been reported from a marine mammalian host ( D. delphis ) whereas adult worms of Galactosomum are parasites of birds and their metacercariae are encysted in fishes (see Jägerskîld 1908). Bittner & Sprehn (1928) investigated A. erinaceum and concluded its placement in Galactosomum as a recognized species based on its distinctive marine mammalian host. Reassignment of A. erinaceum to Galactosomum has been considered by subsequent authors who differ in the validity of G. erinaceum (i.e., either accepted [ Price 1931; Morozov 1952] or currently a taxon inquirendum [ Pearson 1973; WoRMS 2022a]). The description of G. erinaceum was based on excysted metacercaria and exhibited a close affinity to G. lacteum , particularly the larval form (see Culurgioni et al. 2007); however, it differs from the latter in its adult (see Prudhoe 1949) and metacercarial forms (see Culurgioni et al. 2007) by having (i) an ovary well-separated from the ventral sucker by a long distance vs contiguous, (ii) a seminal receptacle distinctly larger than ovary vs an ovary larger than seminal receptacle, and (iii) a distinct esophagus, more than half the length of the prepharynx vs an absent to indistinct esophagus, in addition to (iv) a record of encysted metacercaria from a marine mammalian host vs records of adult worms from birds and their encysted metacercariae from fishes. Thus, we consider G. e rinaceum a valid species within Galactosomum and in need of future collection of their adults.

Figures

FIGURES 9–11. Galactosomum erinaceum (Poirier, 1886) Bittner & Sprehn, 1928 and Glossidium pedatum Looss, 1899. 9. Ga. erinaceum (syn. Distomum erinaceum Poirier, 1886), ventral view, redrawn from Poirier (1886, fig. 6). 10. Gl. pedatum (syn. Astiotrema lazeri El-Naffar, Saoud & Hassan, 1984), ventral view, redrawn from El-Naffar et al. (1984, fig. 1). 11. Gl. pedatum (syn. Astiotrema reniferum of Beverley-Burton 1962 nec Looss, 1900), ventral view, redrawn from Beverley-Burton (1962, fig. 2). Abbreviations: AT, anterior testis; BS, body spines; Ce, cecum; CP, cirrus-pouch; Es, esophagus; EV, excretory vesicle; GA, genital atrium; GP, genital pore; LC, Laurer’s canal; MF, muscular fibrils; MG, Mehlis’ gland; OS, oral sucker; Ov, ovary; Ph, pharynx; Pr.Ph, prepharynx; PP, pars prostatica; PT, posterior testis; SR, seminal receptacle; SV, seminal vesicle; Ut, uterus; V-D, vas-deferens; VF, vitelline follicle; VS, ventral sucker. Scale bars: Fig. 9 = 500 µm; Fig. 10 = 300 µm; Fig. 11 = 500 µm.