A reevaluation of specimens of Mesocoelium monas (Platyhelminthes: Digenea: Mesocoeliidae) from the Natural History Museum, UK and the United States National Parasite Collection, USA
Author
Calhoun, Dana M.
Author
Dronen, Norman O.
text
Zootaxa
2012
3589
1
29
journal article
10.5281/zenodo.209761
2b78cedc-fd40-4bff-98c5-12aacd319fc4
1175-5326
209761
Mesocoelium
cf lanceatum—
USNPC 0 84288.00
(
Figure 14
;
Table 4
)
Host:
Anaxyrus americanus
(Frost)
(
syn.
Bufo americanus
Holbrook
), American toad (
Anura
:
Bufonidae
).
Locality:
Arkansas,
USA
. (Native)
Description:
Based on one specimen: Body 1,250 by 470; forebody 373 long, representing 30% of body length. Mouth subterminal; oral sucker subspherical, 153 by 161; prepharynx absent; pharynx subspherical, 50 by 48; ratio of pharynx width to oral sucker width 1:3.4; esophagus 75 long; ceca short, terminating anterior to anterior margin of ovary. Ventral sucker subspherical, situated anterior 1/3 of body, 123 by 115; ratio of ventral sucker width to oral sucker width 1:1.4. Testes subspherical, oblique; right testis 100 by 125; left testis 125 by 100. Genital pore postbifurcal, median. Cirrus sac, 150 long, representing 12% of body length. Ovary spherical, 105 by 110; postovarian space, 620 long, representing 50% of body length. Uterus extensive, filling hindbody. Vitelline follicles distributed in lateral fields from level of pharynx to level of posterior margin of ovary. Eggs 45 (44–45) by 30 (29–30). Excretory system not visible.
Remarks:
The edges of this specimen are convoluted and folded on the right side, suggesting it may have been fixed without coverslip pressure and/or heat. The body also is twisted at the level of the gonads, and the cirrus sac and right testis are displaced to the left, so that the right testis is located immediately anterior to the right testis.
This specimen cannot be assigned to
M
.
monas
because it has a postbifurcal genital pore, the vitelline fields terminate at, or posterior to the posterior margin of the ovary and the ceca do not surpass the ovary posteriorly, whereas in
M
.
monas
the vitelline fields do not surpass the ovary posteriorly and the ceca surpass the ovary posteriorly (occupying 31% of postovarian space). This specimen; however, can be assigned to the
lanceatum
body
type
because it has short ceca that do not surpass the ovary and it has a postbifurcal genital pore.
TABLE 4.
Comparative measurements, morphometric percentages and morphometric ratios for species of
Mesocoelium
previously identified as
Mesocoelium monas
that appear to be
Mesocoelium burti
,
Mesocoelium lanceatum
or
Mesocoelium pesteri
from the Natural History Museum, UK and the United States Parasitology Collections.
| Characteristic |
M
.
burti
NHMUK 1980.11.12 4 n=5
|
M
. cf
lanceatum
USNPC 0 84288.00 n=1
|
M
. cf
pesteri
USNPC 0 89067.00 n=2
|
| Body length |
1,378 (1,274–1,482) |
1,250 |
923 (806–1,040) |
| Forebody length |
430 (410–450) |
373 |
245 |
| Forebody length as a percentage of body length |
31% (30–32%) |
30% |
27% |
| Oral sucker width |
228 (216–240) |
161 |
246 (216–276) |
| Pharynx width |
81 (78–83) |
48 |
NM |
| Oral sucker width/pharynx width |
1:2.8 (1:2.6–1:3.0) |
1:3.4 |
NM |
| Ventral sucker width |
167 (156–177) |
115 |
153 (120–182) |
| Oral sucker width/ventral sucker width 1:1.3 (1:1.2–1:1.4) |
1:1.4 |
1:1.7 (1:1.5–1:1.8) |
| Esophagus length 80 |
75 |
NM |
| Percentage ceca surpass ovary into 37% postovarian space |
Short ceca |
Short ceca |
| Ovary width 112 (104–120) |
110 |
NM |
| Average testes width 116 (114–117) |
112 (100–125) |
NM |
| Cirrus sac length 94 (91–96) |
150 |
NM |
| Cirrus sac length as a percentage 7% of body length |
12% |
NM |
| Postovarian space length 940 (910–960) |
620 |
NM |
| Postovarian space length as 68% (65–71%) a percentage of body length |
50% |
NM |
| Egg length 34 (31–36) |
45 (44–45) |
34 |
| Egg width 21 (18–24) |
30 (29–30) |
23 |
Host species
Bufo marinus
|
Anazyrus
americanus
|
Anolis sagrei
|
|
| Locality Jamaica |
Arkansas |
Panama |
| NM=No accurate measurement possible. n=Sample size. |
This specimen further differs from
M. monas
by a shorter body (1,250 compared with 1,835 [1,260–2,410]), a narrower ventral sucker (115 compared with 344), larger eggs (45 [44–45] by 30 [29–30] compared with 39 [34–44] by 23 [21–25]), and a larger ratio of oral sucker width to the pharynx width (1:3.4 compared with 1:2.6).
This specimen is consistent with
M
.
lanceatum
by having a similar ratio of ventral sucker width to oral sucker width (1:1.4 compared with 1:1.6 [1:1.6–1:1.7]), and similar eggs (45 [44–45] by 30 [29–30] compared with 42 [40–44] by 25 [23–27]). This specimen differs from
M
.
lanceatum
by having a shorter body length (1,250 compared with 2,700 [2,100–3,300]) and a shorter postovarian space (620 compared with 1,728).
Mesocoelium lanceatum
was originally described from
Japan
and to our knowledge there has not been a species of
Mesocoelium
described from the Americas that has short ceca. Although this specimen may represent an undescribed species, it is possible that an Old World species may have been introduced into
Anaxyrus (Bufo) americanus
in Arkansas.