Mesocoelium carli

López-García, Ashley Samara & García-Prieto, Luis, 2017, A reevaluation of the specimens of Mesocoelium (Trematoda: Mesocoeliidae) in the Colección Nacional de Helmintos, Mexico, Zootaxa 4273 (2), pp. 151-176 : 169-172

Carli body type

Mesocoelium sp. carli body type CNHE-876a (2 slides: two specimens) ( Figure 14 ), R. marina ( Anura : Bufonidae ) from Tilarán , Guanacaste, Costa Rica.

Mesocoelium sp. carli body type CNHE-1067c (2 slides: two specimens) ( Figure 15 ), Plestiodon sp. (= Eumeces sp.) ( Squamata : Scincidae ) from Cuicatlán , Oaxaca, Mexico.

Mesocoelium sp. carli body type CNHE-1068 (7 slides: seven specimens) ( Figure 16 ), Plestiodon sp. (= Eumeces sp.) ( Squamata : Scincidae ) from Cuicatlán , Oaxaca, Mexico.

Mesocoelium sp. carli body type CNHE-1528d (2 slides: two specimens) ( Figure 17 ), R. marina ( Anura : Bufonidae ) from Laguna El Zacatal, Veracruz, Mexico (CNHE-1528d).

Characterization. Based on 13 specimens. Body oval, covered with numerous spines that gradually diminish to posterior end, surpassing ovary and disappearing at different body levels; slightly visible on specimen CNHE- 1068; oral sucker subspherical, wider than long or spherical (CNHE-1068); prepharynx very short, almost absent; pharynx wider than long; cecal bifurcation slightly posterior to mid-forebody or slightly anterior (CNHE-1068 and CNHE-1528d); intestinal ceca surpass ovary posteriorly and end slightly posterior to mid-body or slightly anterior to mid-body (one specimen of CNHE-1067c and one of CNHE-1068). Testes lateral or slightly diagonal at level of ventral sucker or anterior to it; cirrus sac between cecal bifurcation and ventral sucker, completely or almost completely inside cecal bow (except for one specimen of CNHE-876a); the vitelline fields extends from the midlevel of oral sucker in some specimens or from the posterior end of oral sucker, surpassing cecal ends and enter into the postovarian space. Seminal vesicle bipartite; genital pore postbifurcal, submedian; ovary sinistral (seven specimens) or dextral (six specimens). Uterus widely distributed but located mostly under ventral sucker. Excretory system partially visible ( Table 9).

Remarks. The specimens labelled CNHE-876a and CNHE-1067c were identified as M. meggitti (= M. travassosi ) by Caballero & Brenes (1958) and Zerecero (1951), respectively. Nevertheless, this material differs from M. meggitti by the position of the genital pore (prebifurcal and medial in M. meggitti and postbifurcal and submedian in the CNHE specimens); therefore, they belong to the carli body type and not to the mesembrinum body type as M. meggiti . Another difference lies with the body shape, which is attenuated, typically clavate and relatively large in M. meggitti and oval in the CNHE specimens.

Some characteristics of the specimens identified by Zerecero (1950) as M. leiperi (CNHE-1068) differ of those established for this species, e.g., the position of the genital pore (postbifurcal and medial in M. leiperi [ leiperi body type] and postbifurcal and sub median in the specimens with the catalogue number CNHE-1068, which is typical of the carli body type), the percentage of the postovarian space occupied by ceca (in CNHE specimens, it is 28.14% Characteristics Mesocoelium sp. body type carli Mesocoelium carli

CNHE-876a CNHE-1067c CNHE-1068 CNHE-1528d

n=2 n=2 n=7 n=2

Reference Caballero & Brenes Zerecero (1951) Zerecero (1950) Guillén-Hernánđez et al. Anđré (1915)

(1958) (2000)

Original đetermination M. travassosi M. travassosi M. leiperi M. monas -

and in M. leiperi , it is equal to or larger than 37%), the ratio oral sucker width/pharynx width (1: 3.5 in M. leiperi in contrast with 1: 2.7 in our specimens), and egg length, which is a diagnostic trait of M. leiperi according to Dronen et al. (2012); in the CNHE specimens, the egg diameter was 0.034, while in M. leiperi , it ranged from 0.038–0.040.

The last group of specimens (CNHE-1528d) were assigned to M. monas by Guillén-Hernández et al. (2000); however, this material differs from M. monas in all their diagnostic characteristics: 1) the posterior extent of the vitelline fields, which ends from near the mid-level of the caecal ends to up three quarters of it in M. monas (Dronen et al. 2012) , while in the CNHE specimens, the follicles significantly surpass the intestinal ceca; 2) the position of genital pore, which is located posterior to the margin of the pharynx to near the mid-level of the esophagus (prebifurcal and submedian) in M. monas (Dronen et al. 2012) , which is in contrast with the genital pore (postbifurcal and submedian) observed in the CNHE specimens; and 3) in M. monas , the vitelline fields do not surpass the ovary, but in the studied specimens, the vitelline fields surpass it, occupying 43.25% of the postovarian space.

All the specimens previously characterized (CNHE-876a, CNHE-1067c, CNHE-1068, CNHE-1528d) share a carli body type; nonetheless, the only known species within this body type ( M. carli described by André [1915]) differ from our material in the following traits: the percentage occupied by the forebody of the total body length, the total body length, the oral sucker size, the ventral sucker size, the percentage occupied by the cirrus sac of the total body length, the size of the ovary and testicles, the percentage occupied by the postovarian space of the total body length, the percentage of ceca that surpasses the ovary, eggs length, the ratio oral sucker width/pharynx width, the ratio oral sucker width/ventral sucker width (except in CNHE-1068), the host species, and the geographical distribution. The differences cited above prevent the assignment of the CNHE specimens to M. carli ; its exact identification depends on the completion of new collections of specimens to determine if the position of the genital pore is an intrinsic feature or a technical artefact.

Figures

FIGURES 14 – 15. 14. Mesocoelium sp. carli body type (CNHE- 876 a) parasite of Rhinella marina from Tilarán, Guanacaste, Costa Rica. Ventral view of the specimen (A) and detail of the cirrus sac (B). 15. Mesocoelium sp. carli body type (CNHE- 1067 c) parasite of Plestiodon spp. (= Eumeces sp.) from Cuicatlán, Oaxaca, Mexico. Ventral view of the specimen (A) and detail of the cirrus sac (B).

FIGURES 16 – 17. 16. Mesocoelium sp. carli body type (CNHE- 1068) parasite of Plestiodon spp. (= Eumeces sp.) from Cuicatlán, Oaxaca, Mexico. Ventral view of the specimen (A) and detail of the cirrus sac (B). 17. Mesocoelium sp. carli body type (CNHE- 1528 d) parasite of Rhinella marina from Laguna El Zacatal, Veracruz, Mexico. Ventral view of the specimen (A) and detail of the cirrus sac (B).