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 : 6

Mesocoelium meggitti— USNPC 0 90333.00

(Table 1)

Host: Eleutherodacytlus planirostris (Cope) , green house frog ( Anura : Leptodactylidae )

Locality: Metairie, Louisiana; 29 35’ N 90 61’ W. (Introduced)

Description: Based on one specimen: Body 1,950 by 676; forebody 500 long, representing 26% of body length. Mouth subterminal; oral sucker subspherical, 263 by 270; prepharynx absent; pharynx subspherical, 101 by 109; ratio of width of pharynx to width of oral sucker 1:2.5; esophagus (could not be measured); ceca surpassing ovary posteriorly, occupying 47 % of postovarian space. Ventral sucker subspherical, situated in anterior 1/3 of body, 179 by 161; ratio of ventral sucker width to oral sucker width 1:1.7. Testes oval to subspherical, oblique; left testis 130 by 150; right testis 140 by 120. Genital pore median, located at level of posterior 1/3 of pharynx. Cirrus sac clavate, 164 long, representing 8% of body length. Ovary oval, 160 by 150; postovarian space 1,196 long, representing 61% of body length. Uterus extensive, filling hindbody. Vitelline follicles distributed in lateral fields from level of posterior margin of oral sucker to level of cecal ends posteriorly. Eggs 36 (33–40) by 22 (20–23). Excretory system not visible.

Remarks: Although these specimens have ceca that surpass the ovary posteriorly and a prebifurcal genital pore, the genital pore is median rather than submedian, precluding their assignment to the monas body type. Based on these characters, this specimen is assigned to the mesembrinum body type. In addition, M. monas as originally described and redescribed has vitelline fields that terminate well short of cecal ends, as compared with having vitelline fields that surpass the cecal ends, as is the case in USNPC 0 90333.00. This specimen further differs from M. monas by having the vitelline fields terminating near to the cecal ends compared with terminating well short of cecal ends, a shorter forebody (500; 26% of body compared with 970; 53%), a narrower ventral sucker (179 compared with 300), larger percentage that ceca surpass the ovary into the postovarian space (47% compared with 31%), and a narrower ovary (150 compared with 267).

This specimen is consistent with M. meggitti by having a similar body size (1,950 compared with 1,070–2,110), a genital pore that is median and located anterior to the midlevel of the esophagus, vitelline fields that surpass the cecal ends posteriorly, a similar ratio of the ventral sucker width to the oral sucker width (1:1.7 compared with 1:1.5), a similar ratio of pharynx width to oral sucker width (1:2.5 compared with 1:2.0), a similar egg length (36 [33–40] compared with 36 [34–37]) and a similar percentage of the distance that the ceca extend into the postovarian space is within the range reported for M. meggitti (47% compared with 29–47% of the postovarian space, as reported by Dronen et al. 2012).