Mesocoelium, Odhner, 1910

Dronen, Norman O., Calhoun, Dana M. & Simcik, Steven R., 2012, Mesocoelium Odhner, 1901 (Digenea: Mesocoelidae) revisited; a revision of the family and re-evaluation of species composition in the genus 3387, Zootaxa 3387 (1), pp. 1-96 : 79-83

Mesocoelium cf americanum

( Figure 39 ; Table 18)

Definitive host: Peltophryne fustiger (Schwartz) , western giant toad ( Anura : Bufonidae )

Locality: Died at Washington National Zoo, originally from somewhere in the Caribbean.

Site: Intestine.

Specimens examined: Voucher specimens USNPC 031723.00.

Description: Based on three adult specimens. With characteristics of genus. Body monas type, small with slightly rounded posterior end, 1,158 (1,150 –1,175) by 682 (475–800); no body spines observed; forebody 380 (350–410) long, 30–34% of body length. Mouth slightly subterminal, nearly terminal; oral sucker spherical, rotated anteriorly, 134 (150–138) by 155 (150–160); prepharynx short; pharynx wider than long, 74 (58–98) by 89 (80–103); esophagus longer than prepharynx, 79 (63–95) long; cecal bifurcation ¾ distance down forebody; ceca reaching well posterior to ovary, terminating about ⅓ distance down hindbody, occupying 25–29% of postovarian space. Ratio of widths of oral sucker and pharynx 1:1.8 (1:1.7–1:2.2). Ventral sucker located about ⅓ distance down body, smaller than oral sucker, 118 (103–133) by 151 (139–163). Ratio of sucker widths 1:0.9 (1: 0.9–1:1.9). Testes smooth, side by side to slightly diagonal, situated at upper ½ of ventral sucker. Right testis 103 (100–105) by 108 (109–115); left testis 104 (93–110) by 102 (89–119). Cirrus sac medial, situated between cecal bifurcation and ventral sucker, enclosing short cirrus, reduced par prostatica, short to medium ejaculatory duct surrounded by prostate cells and bipartite seminal vesicle, 133 (120–150, 8–12% of body length) by 45 (41–52). Genital pore to left of esophagus, submedian.

Ovary smooth, posttesticular, situated immediately posterior to right testis, 109 (103–115) by 105 (93–118), removed from posterior end by some distance; postovarian space 613 (600–625) long, 52–54% of body length. Seminal receptacle spherical, located immediately sinistral to ovary. Laurer’s canal present, opening not observed. Vitelline fields distributed along ceca from posterior margin of oral sucker posteriorly to midlevel of hindbody, terminating near to, or surpassing cecal ends; follicles 39 (23–63) by 30 (23–40). Uterus occupies most of hindbody, largely postacetabular. Eggs operculate, 39 (33–40) by 24 (20–25) (n = 30).

Excretory vesicle Y-shaped; excretory pore terminal.

Remarks: These specimens (USNPC 031723.00) were of marginal quality, but have moderately long ceca, and a genital pore that is prebifurcal and submedian, placing them in the monas body type. They appear to be most like M. americanum ( Table 18) because the posterior extent of the vitelline fields terminate near to, or surpass the cecal ends posteriorly; the gonads overlap the area of the ventral sucker; the body is oval, widest near midbody; the genital pore is located posterior to the midlevel of the esophagus, just above the cecal bifurcation and the ceca terminate near midlevel of the postovarian space, occupying 25–29% of the length of the postovarian space. As far as we could tell, the anterior extent of the vitelline fields reached anteriorly only to about the level of the pharynx and the oral sucker is rotated anteriorly so that the mouth approaches being terminal, suggesting that these specimens may represent a species different from M. americanum .

Mesocoelium briene as originally described and illustrated by Vercammen-Grandjean (1960)

( Figure 40 ) – Not redescribed herein

Figures

FIGURE 39. Mesocoelium cf americanum (USNPC 0.31723.00). 39. Ventral view of adult.

FIGURE 40. Mesocoelium brieni adapted from Figure 198 of Vercammen-Grandjean 1960 as an example of the brieni body type. 40. Ventral view of adult.