Mesocoelium
Creators: name: Calhoun, Dana M.
name: Dronen, Norman O.
Publisher: name: Zenodo
Year: 2012
Subjects: Biodiversity
Taxonomy
Animalia
Platyhelminthes
Trematoda
Plagiorchiida
Mesocoeliidae
Mesocoelium

description: Mesocoelium cf americanum— USPNC 0 85478.00
(Figure 8; Table 2)
Host: Anolis gingivinus (Cope), Anguilla bank anole (Squamata: Iguanidae).
Locality: Lesser Antilles, Caribbean. (Native)
Description: Based on one specimen: Body 1,738 by 600; forebody 550 long, representing 32% of body length. Mouth subterminal; oral sucker circular, 250 by 250; prepharynx absent; pharynx wider than long, 52 by 62; ratio of oral sucker width to pharynx width 1:4.0; esophagus 65 long; ceca surpassing posterior margin of ovary, occupying 22% of postovarian space. Ventral sucker oval, situated in anterior 1/3 of body, 200 by 227; ratio of ventral sucker width to oral sucker width 1:1.1. Testes spherical to subspherical, slightly oblique; right testis 88 by 95; left testis 85 by 92. Genital pore submedian located immediately anterior to cecal bifurcation. Cirrus sac clavate, 125 long, representing 7% of body length. Ovary subspherical, 115 by 93; postovarian space 1,000 long, representing 58% of body length. Uterus extensive, filling hindbody. Vitelline follicles distributed along ceca in lateral fields from level of posterior 1/3 of oral sucker to near level of cecal ends posteriorly. Eggs 46 (43–48) by 29 (28–30). Excretory system not visible.
Remarks: This specimen appears to have been cold fixed without coverslip pressure. It is contracted, irregular in shape and the body has been rolled to one side displacing the ventral sucker and genital pore to the right. Additionally, the pharynx is pulled anteriorly into the posterior aspect of the oral sucker.
Although this specimen has ceca that surpass the ovary posteriorly, and a prebifurcal and submedian genital pore, and is assigned to the monas body type, it cannot be assigned specifically to M. monas. This specimen can be distinguished from M. monas by having vitelline fields that surpass the cecal ends posteriorly compared with terminating well short of the cecal ends, a larger ratio of the oral sucker width to pharynx width (1:4.0 compared with 1:2.6), a smaller ventral sucker (277 compared with 344) and larger eggs (46 [43–48] by 29 [28–30] compared with 39 [34–44] by 23 [21–25]).
This specimen is consistent with M. americanum by having a posterior extent of vitelline fields that terminate near to the cecal ends, gonads that overlap the area of ventral sucker; an oval body shape where it is widest from level of the ventral sucker to the midlevel of the hindbody, a prebifurcal genital pore that is submedian and located posterior to the midlevel of the esophagus, an anterior extent of the vitelline fields that reaches the level of oral sucker, and by having a generally similar host locality (Texas Gulf coast compared with the Caribbean). Additionally M. americanum has a similar body length (1,738 compared with 1,325–4,038), a similar length of the postovarian space (1,000 compared with 740–2,626); and a similar egg length (46 [43–48] compared with 41 [39–45]). This specimen differs from M. americanum by having a larger ratio of the oral sucker width to the pharynx width (1:4.0 compared with 1:2.4 [1:2.2–1:2.7]), a smaller percentage that the ceca extend into the postovarian space (22% compared with 35%), a shorter cirrus sac length (125; 7% of body length compared with 113–238; 10%), and a larger egg width (29 [28–30] compared with 24 [21–26]). Based on these differences, this specimen may represent an undescribed species, but without additional, properly fixed specimens it cannot be adequately distinguished or described.
description: Published as part of 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, pp. 1-29 in Zootaxa 3589 on page 13, DOI: 10.5281/zenodo.209761