Mesocoelium neohylae, Dronen & Calhoun & Simcik, 2012

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 : 86-88

Mesocoelium neohylae n. sp.

( Figures 45–48 ; Table 12)

Type host: Hyla cinerea (Schneider) , American green treefrog ( Anura : Hylidae )

Type locality: Burleson County, Texas, USA, 30° 24’ N, 96° 13’ W .

Site: Intestine.

Deposited specimens: Holotype USNPC 104821.00 ; Paratype USNPC 104822 .00.

Description: Based on eight adult specimens. With characteristics of genus. Body leiperi type, small, elongate with somewhat tapered posterior end, holotype 2,525 (range 2,500 –2,740; mean 2,620) by 975 (950 –1,175; 1,075); no spines observed; forebody 725 (725–800; 763) long, 27–29% of body length. Mouth slightly subterminal; oral sucker spherical, wider than long, 280 (270–300; 290) by 300 (295–320; 310); prepharynx short; pharynx wider than long, 94 (88–95; 91) by 122 (120–138; 129); esophagus longer than prepharynx, 62 (60–78; 70) long; cecal bifurcation 1/2 distance down forebody; ceca reaching well posterior to ovary, occupying 42% (37–47%; 43%) of postovarian space. Ratio of widths of oral sucker and pharynx 1:2.5 (1:2.3–1:2.5; 1:2.4). Ventral sucker located ⅓ distance down body, smaller than oral sucker, 247 (245–278; 260) by 196 (190–220; 200). Ratio of sucker widths 1:1.5 (1:1.4–1:1.5; 1: 1.5).

Testes smooth, side by side to slightly diagonal, situated at level of upper ⅓ of ventral sucker. Right testis 218 (215–220; 217) by 234 (230–270; 250); left testis 219 (218–230; 224) by 228 (200–230; 220). Cirrus sac medial, situated between cecal bifurcation and ventral sucker, enclosing short cirrus, reduced pars prostatica, short ejaculatory duct surrounded by prostate cells, and bipartite seminal vesicle, 148 (145–169; 159, 6–7% of body length) by 58 (57–62; 59) wide. Genital pore immediately postbifurcal on midline of body.

Ovary smooth, posttesticular, situated immediately posterior to right testis, 216 (214–237; 226 by 182 (182–226; 204), removed from posterior end by some distance, postovarian space 1,685 (1,500–1,740; 1,575) long, 58–64% of body length. Seminal receptacle spherical, located immediately sinistral to ovary. Laurer’s canal present, opening not observed. Vitelline follicles relatively large, 60–99 (53–99; 78) by 36–68 (36–73; 58), distributed along ceca from level of posterior margin of oral sucker posteriorly to midlevel of hindbody, terminating immediately anterior to cecal ends on one side, and some distance posterior to cecal ends on one side. Uterus largely postacetabular, filling most of hindbody. Eggs operculate, 40–44 (40–46; 43) by 24–29 (23–29; 26) (n = 40).

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

Remarks: These specimens (USNPC 104821.00; 104822.00) have moderately long ceca, and a genital pore that is postbifurcal and median, placing them in the leiperi body type. The ceca occupy 37–47% of the length of the postovarian space and the ratio of the width of the pharynx to the width of the oral sucker 1:2.3–1:2.5, placing them in Mesocoelium neohylae n. sp. (Table 12). The new species is most similar to M. leiperi by having the posterior extent of the vitelline fields terminating near to, or surpassing the cecal ends posteriorly, the anterior extent of the vitelline fields reaching to the level of the pharynx or more anterior, ratio of the width of the ventral sucker to the width of the oral sucker that is 1:1.6 or less and ceca that occupy more than 37% of the length of the postovarian space. The new species differs from M. leiperi by having a larger body size (2,500 –2,740 long compared to 1,970), a smaller ratio of the width of the pharynx to the width of the oral sucker (1:2.3–1:2.5 compared to 1:3.5) and a longer egg (40–46 compared to 38–40) (Table 12). The new species is from H. cinerea (treefrog) from Texas, USA rather than from T. piscator (Asiatic water snake) from the Union of Myanmar.

Figures

FIGURES 44–45. Mesocoelium thapari (BMNH 1984.4.25.11-12) and Mesocoelium neohylae n. sp. (USNPC 104821.00). 44. Mesocoelium thapari; Ventral view of adult. 45. Mesocoelium neohylae n. sp.; Ventral view of holotype.

FIGURES 46–48. Mesocoelium neohylae n. sp. 46. Ventral view of paratype (USNPC 102822.00). 47. Composite drawing of seminal vesicle, ventral view. 48. Composite drawing of area of oötype, ventral view.