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 monodi— USNPC 0 90332.00
(Figure 12, Table 3)
Host: Incilius valliceps (Weigermann) (syn. Bufo valliceps Weigermann), Gulf coast toad (Anura: Bufonidae).
Locality: Metairie, Louisiana; 29 35’ N 90 61 W. (Introduced)
Description: Based on one specimen: Body 1,456 by 494; forebody 460 long, representing 32% of the body length. Mouth subterminal; oral sucker wider than long, 172 by 169; prepharynx short; pharynx wider than long, 75 by 78; ratio of pharynx width to oral sucker width 1:2.2; esophagus 50 long; ceca terminating posterior to posterior margin of ovary, occupying 49% of postovarian space. Ventral sucker oval, situated in anterior 1/3 of body, wider than long, 140 by 143; ratio of ventral sucker width to oral sucker width, 1:1.8. Testes opposite; right testis 96 by 120; left testis, 104 by 101. Genital pore submedian, immediately postpharyngeal. Cirrus sac 99 long, representing 7% of body length. Ovary longer than wide, overlapping posterior margin of right testis, 100 by 85; postovarian space 790 long, representing 54% of body length. Uterus extensive, filling hindbody. Vitelline follicles distributed in lateral fields from level of lower margin of oral sucker to level of cecal ends posteriorly. Eggs (30 by 22) (n=1). Excretory system not visible.
Remarks: This specimen appears to be contracted, pulling the genital pore into the oral sucker. Most eggs were not measured because this specimen appeared to be a young adult and had only a few undeveloped eggs in the uterus. Also, the poor condition of the specimen limited measurements of some other structures (e.g. excretory system, cirrus sac).
Although the 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 can be distinguished from M. monas by having vitelline fields that terminate near to the cecal ends rather than terminating well short of the cecal ends, a smaller forebody (460; 32% of the body length compared with 970; 53%), a narrower oral sucker (169 compared with 295 [230–360]), a narrower pharynx (78 compared with 133 [100–166]), a narrower ventral sucker (143 compared with 300), a larger percentage that the ceca surpass the ovary into the postovarian space (54% compared with 31%); a narrower ovary (85 compared with 267), and smaller egg lengths (30 compared with 34–44).
This specimen is consistent with M. monodi by having similar forebody lengths (460; 32% forebody length compared with 778; 26%), a similar ratio of oral sucker width to pharynx width (1:2.2 compared with 1:2.8), a similar oral sucker width to ventral sucker width (1:1.8 compared with 1:1.3) and a similar egg width (22 compared with 20–23). This specimen can be distinguished from M. monodi by having a shorter body length (1,456 compared with 3,000), a longer percentage of ceca that surpass the ovary into the postovarian space (49% compared with 33%) and these specimens were collected in different geographical areas (Louisiana compared with Cameroon). Although we feel this specimen may represent M. monodi, these differences suggest this specimen might represent an undescribed species. This appears to be the same species as represented by USNPC 0 90334.00.
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 19, DOI: 10.5281/zenodo.209761