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 : 9-10

Mesocoelium burti— NHMUK 1980.11.12 4

( Figure 5 , Table 4 )

Host: Bufo marinus (Linneaus) , cane toad ( Anura ; Bufonidae ).

Locality: Kingston, Jamaica. (Introduced)

Description: Based on five specimens (three specimen fully measured): Body 1,378 (1,274–1,482) by 615 (572–650); forebody 430 (410–450) long, representing 31% of body length. Mouth subterminal; oral sucker oval, 216 (200–231) by 228 (216–240); prepharynx absent; pharynx oval, 98 (91–104) by 81 (78–83); ratio of pharynx width to oral sucker width 1:2.8 (1:2.6–1:3.0); esophagus 80 (n=1) long; ceca surpassing ovary posteriorly, occupying about 37% of postovarian space. Ventral sucker oval, situated in posterior margin of anterior 1/3 of body, 172 (166–177) by 167 (156–177); ratio of ventral sucker width to oral sucker width 1:1.3 (1:1.2–1:1.4). Testes oblique; right testis 96 by 114; left testis 91 long by 117 wide (n=1). Genital pore median, located near level of posterior margin of pharynx. Cirrus sac 94 (91–96) long, representing about 7% of body length. Ovary oval to round, 100 (96–104) by 112 (104–120); postovarian space 940 (910–960), representing 68% of body length. Uterus extensive, filling hindbody. Vitelline follicles distributed in lateral fields from posterior margin of oral sucker to posterior margin of cecal ends. Eggs 34 (31–36) by 21(18–24). Excretory system not visible.

Remarks: These specimens were apparently cold fixed without slight coverslip pressure resulting in contraction of the body, and two were damaged therefore only three specimens could be fully measured. In these the pharynx was pulled anteriorly into the posterior end of the oral sucker and the anterior ends of the vitelline fields were shifted medially to near the posterior margin of the oral sucker.

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, these specimens are assigned to the mesembrinum body type. These specimens further differ from M. monas by having vitelline fields that surpass the cecal ends posteriorly, a shorter body (1,378 [1,274–1,482]) compared with 1,835 [1,260–2,410]), a narrower pharynx (78–83 compared with 138), and a narrower ventral sucker (156–177 compared with 344).

These specimens are somewhat similar to M. sibynomorphi by having a similar ratio of oral sucker width to ventral sucker width (1:1.2–1:1.4 compared with 1:1.2), a similar ratio of the oral sucker width to the pharynx width (1:2.8 [1:2.6–1:3.0] compared with 1:2.8 [1:2.7–1:2.8]), and a prebifurcal genital pore that is located immediately posterior to the posterior margin of the pharynx. These specimens can be distinguished from M. sibynomorphi by having a smaller body length (1,378 [1,274–1,482] compared with 4,200 [3,700–4,700]), a shorter forebody (410–450 compared with 1,090), a narrower oral sucker (228 [216–240] compared with 353 [325–381]), and a higher percentage that the ceca extend into the postovarian space (37% compared with 6%).

These specimens are consistent with to M. burti by having a similar postovarian space length (710 [590–830] compared with 665), a similar ratio of the oral sucker width to the pharynx width (1:2.6–1:3.0 compared with 1:2.9), a similar ratio of the oral sucker width to the ventral sucker width (1:1.2–1:1.4 compared with 1:1.3), a similar percentage that the ceca extend into the postovarian space (31% compared with 21–35%), and a similar eggs (34 [31–36] by 21 [19–22] compared with 36 [35–36] by 21[19–22]).

Figures

FIGURE 5. Mesocoelium burti— NHMUK 1980.11. 12 4 from Bufo marinus, ventral view of adult.