Mesocoelium malayanum, Palmieri & Sullivan, 1977

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 : 60

Mesocoelium malayanum

( Figure 22 ; Table 16)

Definitive host: Psamnophis sibilans (Linnaeus) , striped sand snake ( Squamata : Lamprophiidae ).

Locality: Kenya.

Site: Intestine.

Specimens examined: BMNH 1986.9.22.

Description of specimens: Based on four specimens. With characteristics of genus. Body monas type, small, posteriorly attenuated, body tapering markedly posteriorly, nearly club-shaped, forebody wider than hindbody, 1,581 (1,400 –1,688) by 377 (425–563); body spines not observed; forebody 535 (450–600) long, 32–37% of body length. Oral sucker spherical to subspherical, 233 (200–250) by 247 (200–283), mouth opening anterior from center of sucker, nearly terminal; prepharynx short; pharynx subspherical to spherical, wider than long, 101 (88–120) by 115 (93–135); esophagus 75 (25–170) long; cecal bifurcation near midlevel of forebody; ceca surpassing ovary posteriorly, terminating near midlevel of hindbody, occupying 29–45% of postovarian space. Ratio of width of oral sucker and pharynx 1:2.2 (1:2.0–1:2.4). Ventral sucker located anterior to midlevel of body, smaller than oral sucker, 203 (175–220) by 202 (178–225). Ratio of sucker widths 1:1.2 (1:1.0–1:1.5).

Testes smooth, diagonal, situated at level of ventral sucker. Right testis 155 (98–200) by 131 (85–180); left testis 156 (113–200) by 140 (103–180). 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, 155 (110–170, 8–11% of body length) by 61 (33–95). Genital pore immediately postpharyngeal, prebifurcal, submedian.

Ovary smooth, posttesticular, situated short distance posterior to right or left testis, 172 (100–270) by 86 (76–90), removed from posterior end by some distance; postovarian space 789 (700–870) long, 47–54% of body length. Ratio of width of ovary to mean width of testes 1:1.6 (1:1.3–1:2.0). Seminal receptacle spherical, located immediately sinistral and slightly posterior to ovary. Laurer’s canal present, opening on dorsal surface. Vitelline fields distributed along ceca from level of pharynx posteriorly to near midlevel of postovarian space, terminating near to, or surpassing cecal ends; vitelline follicles 28 (17–43) by 25 (17–33) (n = 20). Uterus largely postacetabular, filling most of hindbody. Eggs operculate, 43 (40–45) by 28 (25–30) (n = 30).

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

Remarks: These specimens (BMNH 1986.9.22) 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 and the body is markedly attenuated posteriorly (nearly club-shaped) so that the forebody is wider than the hindbody, placing them in M. malayanum . Although the eggs of these specimens are somewhat wider (25–30 compared to 22–24), they conform to the original description by Palmieri & Sullivan (1977) in all remaining diagnostic characteristics (Table 16) and were collected from the Old World as the specimens used in the original description of this species (Africa compared to Malaysia). The specimens from BMNH were collected from the striped sand snake, P. sibilans , while those used in the original description were from the fanged river frog, L. macrodon .

Figures

FIGURES 21–22. Mesocoelium meggitti (USNPC 090333.00) and Mesocoelium malayanum (BMNH 1986.9.22.72-90). 21. Mesocoelium meggitti; Ventral view of adult. 22. Mesocoelium malayanum; Ventral view of adult.