Mesocoelium sociale (Luhe, 1901) 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 : 83

Mesocoelium sociale

( Figures 41–43 ; Table 16)

Definitive host: Bufo asper Gravenhorst , Asian giant toad ( Anura : Bufonidae )

Locality: Malaysia.

Site: Intestine.

Specimens examined: Voucher specimens BMNH 1994.11.25.

Description of specimens. Based on five adult specimens. With characteristics of genus. Body sociale type, small, elliptical, spinose, 2,380 (1,864 –2,775) by 644 (600–688), body spines 9–11 long; forebody 671 (540–715) long, 26–30% of body length. Mouth subterminal; oral sucker spherical, 213 (200– 225) by 236 (215–260); prepharynx short; pharynx wider than long, 88 (70–105) by 107 (93–120); esophagus longer than prepharynx, 46 (28–75) long; cecal bifurcation ⅓ distance down forebody; ceca reaching well posterior to ovary, terminating about ¾ distance down hindbody occupying 57–62% of postovarian space. Ratio of widths of oral sucker and pharynx 1:2.2 (1:2.1–1:2.3). Ventral sucker located upper ⅓ of body, smaller than oral sucker, 167 (146–175) by 134 (123–168). Ratio of sucker widths 1:1.5 (1:1.4–1:1.7).

Testes smooth, nearly side by side to slightly diagonal, overlapping ventral sucker. Right testis 160 (128–182) by 136 (125–150); left testis 148 (140–165) by 139 (118–148). 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, 171 (124–193, 7–9% of body length) by 52 (45–60). Genital pore at level of cecal bifurcation, slightly submedian.

Ovary smooth, posttesticular, situated immediately posterior to right or left testis, 168 (148–195) by 157 (125–180), removed from posterior end by some distance; postovarian space 1,289 (945–1,625) long, 51–59% 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 pharynx posteriorly to about ¾ distance down hindbody, terminating near to, or surpassing cecal ends; vitelline follicles 49 (23–80) by 36 (22–50) (n = 20). Uterus occupies most of hindbody, largely postacetabular. Eggs operculate, 37 (32–43) by 22 (20–25) (n = 30).

Excretory vesicle Y-shaped; excretory pore terminal.

Remarks: These specimens (BMNH 1994.11.25) have moderately long ceca, and a genital pore that is bifurcal and submedian, placing them in the sociale body type. The ceca occupy 57–62% of the length of the postovarian space and the ratio of the width of the pharynx to the width of the oral sucker is 1:2.1–1:2.3, placing them in M. sociale as originally described by Lühe (1901). These specimens have a somewhat smaller ratio of the width of the pharynx to the width of the oral sucker (1:2.1–1:2.3 compared to 1:2.6–1:2.7) and larger ratio of the sucker widths (1:1.4–1:1.7 compared to 1:1.2–1:1.3) than M. sociale , as originally described, but they generally conform to all other aspects of M. sociale (Table 16) and we feel that the slight differences in ratios may be a result of small sample sizes. Both the specimens used in the original description of this species and the specimens represented by BMNH 1994.11.25 are from species of toad from the same general geographical region of the world ( Malaysia and southern India, repectively).

Figures

FIGURES 41–43. Mesocoelium sociale (BMNH 1994.11.25. 8-11). 41. Ventral view of adult. 42. Composite drawing of seminal vesicle, ventral view. 43. Composite drawing of area of oötype, ventral view.