Mesocoelium, 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 : 39-43

Mesocoelium cf brevicaecum

( Figures 4–6 ; Table 13)

Definitive hosts: Litoria citropus (Tschudi) , (syn. Hyla citropus Tschudi ), the Blue Mountain treefrog ( Anura : Hylidae ).

Locality: New South Wales.

Site: Intestine.

Specimen examined: USNPC 036522.00 (New South Wales)

Description of specimen: Based on one specimen. With characteristics of genus. Body lanceatum type, small, elongate with somewhat tapered posterior end, spinose, 1,975 by 680; body spines 13 (12–14) long; forebody 735 long, 38% of body length. Mouth subterminal; oral sucker spherical to subspherical, 245 by 243; prepharynx nearly absent; pharynx spherical, wider than long, 63 by 98; esophagus 138 long; cecal bifurcation anterior to midlevel of forebody; ceca short, terminating anterior to level of ovary. Ratio of widths of oral sucker and pharynx 1:2.5. Ventral sucker located in anterior ½ of body, smaller than oral sucker, 183 by 158. Ratio of sucker widths 1:1.5.

Testes smooth, slightly diagonal, situated at level of ventral sucker. Right testis 280 by 255; left testis 290 by 240. Cirrus sac unusually robust, situated between cecal bifurcation and ventral sucker, enclosing short cirrus, reduced pars prostatica, short ejaculatory duct surrounded by prostate cells and large, bipartite seminal vesicle, 290 (15% of body length) by 150. Genital pore immediately postbifurcal, median.

Ovary smooth, posttesticular, situated immediately posterior to right testis, 160 by 150, removed from posterior end by some distance; postovarian space 940 long, 48% of body length. Ratio of width of ovary to mean width of testes 1:1.7. Seminal receptacle spherical, located immediately sinistral and slightly posterior to ovary. Laurer’s canal present, opening on dorsal body surface. Vitelline fields distributed along ceca from level of pharynx posteriorly to level of ventral sucker, terminating short distance anterior to cecal ends; vitelline follicles 60 (40–130) by 50 (30–90) (n = 6). Uterus largely postacetabular, filling most of hindbody. Eggs operculate, 42 (40–43) by 27 (26–29) (n = 10).

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

Remarks: A specimen (USNPC 036522.00) from the Blue Mountain treefrog from New South Wales also appears to be M. brevicaecum (Table 13), but it has an unusually large, more broadly extensive cirrus sac (290 long; 15% of body length compared to187 [125–250]; 8–10% of body length) ( Figures 4–6 ). The specimen from New South Wales also differs from those we examined from Taiwan (BMNH 1973.5.24) by having somewhat smaller body spines (12–14 long compared to 17–22), a more extensive forebody (38% of body length compared to 23–32%), and USNPC 036522.00 was from New South Wales rather than Taiwan, and may represent an undescribed species. However, this specimen may have been subjected to excessive coverslip pressure at the time of fixation, which may account for the unusually large appearance of the cirrus sac and seminal vesicle, the displacement of the cecal bifurcation to the right and the displacement of the vitelline follicles towards the midline of the body on the right side in the specimen.

Figures

FIGURES 4–6. Mesocoelium cf brevicaecum (USNPC 036522.00). 4. Ventral view of adult. 5. Drawing of seminal vesicle, ventral view. 6. Drawing of area of oötype, ventral view.