Mesocoelium pesteri, Saoud, 1964

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 : 48

Mesocoelium pesteri

( Figure 8; Table 14)

Definitive host: Bufo marinus Linnaeus , the cane toad ( Anura : Bufonidae ).

Locality: Rio de Janeiro, Brazil.

Site: Intestine.

Specimens examined: BMNH 1988.9.15. 6.

Description of specimens: Based on three specimens. With characteristics of genus. Body pestri type, small, oval, spinose, 1,721 (1,613 –1,775) by 884 (850–913); body spines 9–10 long; forebody 597 (570–610) long, 32–38% of body length. Mouth slightly subterminal; oral sucker spherical to subspherical, 244 (228–265) by 256 (254–260); prepharynx short; pharynx subspherical to spherical, wider than long, 79 (63–90) by 105 (98–110); esophagus 74 (35–123) long; cecal bifurcation near midlevel of forebody; ceca short, terminating anterior to midlevel of ovary. Ratio of widths of oral sucker and pharynx 1:2.4 (1:2.3–1:2.6). Ventral sucker located immediately anterior to midlevel of body, smaller than oral sucker, 225 (201–234) by 219 (215–223). Ratio of sucker widths 1:1.2 (1:1.1–1:1.2).

Testes smooth, diagonal, situated at level of ventral sucker. Right testis 195 (165–240) by 141 (130–170); left testis 148 (130–170) by 148 (120–163). Cirrus sac situated between pharynx and cecal bifurcation, enclosing short cirrus, reduced pars prostatica, short ejaculatory duct surrounded by prostate cells, and bipartite seminal vesicle, 164 (125–188, 7–12% of body length) by 58 (53–68). Genital pore near posterior margin of pharynx, prebifurcal, median.

Ovary smooth, posttesticular, situated across from right or left testis, 220 (170–280) by 165 (150–194), removed from posterior end by some distance; postovarian space 873 (780–990) long, 48–56% of body length. Ratio of width of ovary to mean width of testes 1:0.9 (1:0.7–1:1.1). Seminal receptacle spherical, located immediately sinistral and slightly posterior to ovary. Laurer’s canal present, opening not observed. Vitelline fields distributed along ceca from level of oral sucker posteriorly to near midlevel of hindbody, surpassing cecal ends; vitelline follicles 47 (23–75) by 33 (15–60) (n = 20). Uterus largely postacetabular, filling most of hindbody. Eggs operculate, 37 (32–39) by 24 (21–25) (n = 30).

Excretory vesicle Y-shaped, with poorly developed arms; excretory pore slightly subterminal.

Remarks: These specimens (BMNH 1988.9.15.6) have short ceca, and a genital pore that is prebifurcal and median, placing them in the pesteri body type. These specimens correspond in nearly all respects to M. pesteri , as originally described by Saoud (1964) (Table 14). They differ by having a somewhat larger ratio of the pharynx width to the oral sucker width (1:2.3–1:2.6 compared to 1:1.6–1.9) and wider eggs (21–25 compared to 18–22). The specimen represented in Figure 1 of the original description is contracted, pulling the ventral sucker anteriorly close to the oral sucker, and apparently was not fixed under coverslip pressure, which makes comparisons to other specimens difficult. The BMNH specimens have short ceca and were collected in Brazil, and we feel that M. pesteri may have been introduced into the New World from Africa and that the differences in egg size and sucker ratios may be a product of the quality of the specimens used in the original description. It should be noted that in Figure 1 of the original description by Saoud (1964) that the scale is apparently in error because if it represents 100µ, then the body of the specimen would be 650 long and the oral sucker would be 160 wide, and both measurements would be outside of the ranges as given in the original description.

Figures

FIGURES 1–3. Mesocoelium brevicaecum (BMNH 1973.5.25.1-11). 1. Ventral view of adult. 2. Composite drawing of area between cecal bifurcation and ventral sucker showing placement of genital pore, uterus and seminal vesicle, ventral view. 3. Composite drawing of area of oötype, ventral view. Abbreviation used in figures: C=cecum; E=egg; Ev=excretory vesicle; G= genital pore; L= Laurer’s canal; M=Mehlis’ glands; OV=ovary; P=pharynx; SR= seminal receptacle; SV=seminal vesicle; T=testis; U=uterus; VD=vitelline duct.