Mesocoelium

Calhoun, Dana M. & Dronen, Norman O., 2012, A reevaluation of specimens of Mesocoelium monas (Platyhelminthes: Digenea: Mesocoeliidae) from the Natural History Museum, UK and the United States National Parasite Collection, USA, Zootaxa 3589, pp. 1-29 : 13

Mesocoelium americanum— NHMUK 1994.6.21 3

( Figure 7 ; Table 2)

Host: Smilisca baudinii (Duméril & Bibron) , Mexican tree frog ( Anura : Bufonidae ).

Locality: Mexico. (Native)

Description: Based on one specimen: Body 2,262 by 936; forebody 780 long, representing 34% of body. Mouth subterminal; oral sucker subspherical, 270 by 270; prepharynx absent; pharynx subspherical, 94 by 104; ratio of width of pharynx to width of oral sucker 1:2.6; esophagus 81 long; ceca surpassing ovary posteriorly, occupying 37 % of postovarian space. Ventral sucker subspherical, situated in anterior 1/3 of body, 172 by 187; ratio of ventral sucker width to oral sucker width 1:1.4. Testes spherical to subspherical, oblique; right testis 130 by 143; left testis 117 by 122. Genital pore, submedian, located immediately posterior to midlevel of esophagus. Cirrus sac 200 long, representing 9% of body length. Ovary subspherical, 220 by 200; postovarian space 1,274 long, representing 56% of body length. Uterus filling hindbody. Vitelline follicles distributed in lateral fields from level of oral sucker to level of cecal ends. Eggs 35 (34–39) by 20 (18–22). Excretory system not visible.

Remarks: The specimen is in poor condition and appears to have been cold fixed, likely without coverslip pressure. It is contracted, irregular in shape, and its body has been rolled so that the pharynx, oral sucker and cecal bifurcation are shifted to the left, displacing the oral sucker and genital pore to the right. The forebody is contracted pulling the oral sucker away from the anterior end.

Although this specimen has ceca that surpass the ovary posteriorly and a prebifurcal genital pore, and is assigned to the monas body type, it cannot be assigned specifically to M. monas . This specimen differs from M. monas by having vitelline fields that terminate near to the cecal ends compared with terminating well short of cecal ends, a smaller forebody (780 compared with 970), a narrower pharynx (104 compared with 138), a narrower ventral sucker (172 compared with 344), and a narrower oral sucker (270 compared with 382).

This specimen is consistent with M. americanum by having a submedian genital pore that is immediately anterior to the cecal bifurcation, a similar body length (2,262 compared with 1,325–4,038), a similar ratio of oral sucker width to pharynx width (1:2.6 compared with 1:2.2–1:2.7), a similar ratio of oral sucker width to ventral sucker width (1:1.4 compared with 1:1.5–1:1.7), and a similar of postovarian space length (1,274 compared with 740–2,626).

Figures

FIGURE 7. Mesocoelium americanum— NHMUK 1994.6. 21 3 from Smilisca baudinii, ventral view of adult. FIGURE 8. Mesocoelium cf americanum— USPNC 0 85478.00 from Anolis gingivinus, ventral view of adult.