Mesocoelium monodi, Dollfus, 1929

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 : 70-75

Mesocoelium monodi

( Figures 30–34 ; Table 17)

Definitive hosts: Mabuya sp. , skink ( Squamata : Scincidae ); Hylarana occidentalis (Perret) , Ivory Coast Frog ( Anura : Ranidae ); Ameitophrynus regularis (Reuss) , the African common toad ( Anura : Bufonidae ) (syn Bufo regularis Reuss ); Incilius valliceps (Weigmann) , Gulf coast toad ( Anura : Bufonidae ); Eleutherodactylus planirostris Cope , greenhouse frog ( Anura : Eleutherodactylidae ); Anolis carolinensis Voigt , Carolina anole ( Squamata : Polychrotidae ).

Localities: the Gold Coast; the Democratic Republic of the Congo; Louisiana, USA.

Site: Intestine.

Specimens examined: BMNH 1954.11.4 (the Gold Coast) , 1960.5.27 ( the Democratic Republic of the Congo) ; SLU-7a, 7b, 11, USNPC 090332 .00, 090334.00 (Louisiana, USA) .

Redescription: Based on nine specimens. With characteristics of genus. Body monas type, small, oval, spinose, 2,317 (1,450 –3,513) by 816 (525–1,263), body spines 7–10 long; forebody 643 (320–850) long, 25% (21–30%) of body length. Mouth slightly subterminal; oral sucker spherical to subspherical, 254 (183–330) by 267 (178–300); prepharynx short; pharynx subspherical to spherical, wider than long, 108 (75–145) by 129 (68–170); esophagus 58 (28–105) long; cecal bifurcation near midlevel of forebody; ceca reaching some distance posterior to ovary, occupying (35–56%) of postovarian space. Ratio of widths of oral sucker and pharynx 1:2.1 (1:1.8–1:2.5). Ventral sucker located anterior to midlevel of body, smaller than oral sucker, 205 (135–260) by 189 (143–260). Ratio of sucker widths 1:1.3 (1:1.1–1:1.6).

Testes smooth, diagonal, situated at level of ventral sucker. Right testis 203 (108–300) by 197 (95–228); left testis 204 (93–283) by 190 (175–225). Cirrus sac situated between pharynx and ventral sucker, enclosing short cirrus, reduced pars prostatica, short ejaculatory duct surrounded by prostate cells, and bipartite seminal vesicle, 220 (88–325, 6–12% of body length) by 67 (38–105). Genital pore near posterior margin of pharynx, prebifurcal, submedian.

Ovary smooth, posttesticular, situated short distance posterior to right or left testis, 207 (118–345) by 193 (103–300), removed from posterior end by some distance; postovarian space 1,542 (850–2,150) long, 47–66% of body length. Ratio of width of ovary to mean width of testes 1:0.9 (1:0.8–1:1.1). 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 body or more posterior, terminating near to, or surpassing cecal ends; vitelline follicles 65 (20–108) long by 49 (25–85) (n = 30). Uterus largely postacetabular, filling most of hindbody. Eggs operculate, 38 (32–44) by 21 (18–25) (n = 40).

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

Remarks: These specimens (BMNH 1954.11.4, 1960.5.27; SLU-7a, 7b,11, USNPC 090332.00, 090334.00) have moderately long ceca, and a genital pore that is prebifurcal and submedian, placing them in the monas body type. 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 near posterior margin of the pharynx; the ceca are moderately long, terminating near midlevel of postovarian space and occupying 35–56% of the postovarian space, placing them in M. monodi (Table 17). As previously pointed out under “Body shape”, the original description of M. monodi was based on a specimen where fixation under slight coverslip pressure was apparently not used, resulting in the unusual pyriform shape shown in Figure 10 from the original description ( Dollfus 1929). This species is very similar to M. danforthi , differing only by the extent the ceca surpass the ovary posteriorly into the postovarian space. With the information at hand we have maintained M. danforthi and M. monodi as distinct species. We examined one small (950 long), apparently young specimen, where the postovarian space was not well developed and there were few eggs present, of which the majority had not developed the outer protein coat. This specimen was from I. valliceps from Louisiana (Table 17, SLU 7b), and was similar to M. monodi by having a similar ratio of the width of the pharynx to the width of the oral sucker (1:2.3), sucker ratio (1:1.1) and a similar egg size (37–42 by 21–25), but the poor state of development made identification to species impossible.

Figures

FIGURES 29–30. Mesocoelium danforthi (BMNH 1980.12.3.18) and Mesocoelium monodi (BMNH 1954.11.4.1). 29. Ventral view of adult. 30. Ventral view of adult.

FIGURES 31–32. Mesocoelium monodi. 31. Ventral view of adult (BMNH 1954.11.4.4). 32. Ventral view of adult. (BMNH 1960.5.27.16).

FIGURES 33–34. Mesocoelium monodi. 33. Ventral view of adult (USNPC 090332.00). 34. Ventral view of adult (090334.00).

FIGURES 10–12. Mesocoelium meggitti (HWML 1570). 10. Ventral view of adult. 11. Composite drawing of seminal vesicle, ventral view. 12. Composite drawing of area of oötype, ventral view.