Heligmosomoidea, Travassos

Panti-May, Jesús Alonso, Moguel-Chin, Wilson Isaias, Hernández-Mena, David Iván, Cárdenas-Vargas, Miguel Humberto, Torres-Castro, Marco, García-Prieto, Luis, Digiani, Maria Celina, Hernández-Betancourt, Silvia F. & Vidal-Martínez, Víctor Manuel, 2023, Helminths of small rodents (Heteromyidae and Cricetidae) in the Yucatan Peninsula, Mexico: an integrative taxonomic approach to their inventory, Zootaxa 5357 (2), pp. 205-240 : 217-219

Heligmosomoidea gen. sp. cf. Vexillata

Site of infection: Small intestine

Host species: Ototylomys phyllotis

Localities: Kuncheil cattle ranch, Papam ranch (Yucatan), Jolie Jungle eco-hotel, Balam Nah eco-hotel, and David Gustavo community (Quintana Roo)

Specimens deposited: CNHE 12005‒12009

GenBank accession numbers: OR271665, OR271682

Comments: The specimens found in this study had a cephalic vesicle and a buccal capsule reduced to an annulus. Females were monodelphic and lack a caudal spine. The synlophe showed 15 ridges with struts, including a careen moderately developed composed of two stout ridges, an axis of orientation of the ridges oblique to subfrontal, and a slight decreasing gradient of the ridge size from right to left on the dorsal side ( Figure 4E ). Males possessed a subsymmetrical caudal bursa with a pattern of type 2-2-1, spicules filiform and a gubernaculum. In females, at the ovejector level, the synlophe was highly modified, with hypertrophy and loss of orientation of the ridges on the whole-body circumference.

The combination of the abovementioned characters allows us to place these specimens undoubtedly in the Heligmosomoidea excluding, among these, the families Herpetostrongylidae , Nicollinidae , Heligmosomidae and Viannaiidae ( Beveridge et al. 2013) . Particularly, the bursal pattern 2-2-1, the synlophe with careen, the ridges continuous and the presence of gubernaculum approach them to the Nippostrongylinae (Heligmonellidae) or, to a lesser degree, to species of Vexillata (Ornithostrongylidae) , all parasites of rodents. The cosmopolitan Nippostrongylinae are typically parasites of cricetids, whereas species of the New World genus Vexillata have been reported from geomyids and heteromyids and from leporids of the genus Sylvilagus ( Digiani et al. 2007) . The only carenated Nippostrongylinae from the New World is, up to now, the monotypic genus Mazzanema Digiani, Notarnicola & Paulos, 2013 , with a species parasitic in Holochilus chacarius from Argentina, characterized by a female synlophe of 19 ridges and a male bursal pattern 1-3-1 ( Digiani et al. 2013). Attending to the main synlophial and bursal characters of the present specimens, plus the fact that the host is a cricetid, they could be assigned to a genus and species not yet described in the Nippostrongylinae . However, the phylogenetic analysis based on the 28S sequences recovered them as sister species of V. vexillata , and not of the other Nippostrongylinae comprised in the study. Morphological characters that approach these specimens to Vexillata are the careen made up of two ridges, the axis of orientation subfrontal, the bursal pattern 2-2-1, the bursal rays 8 filiform, and the distal division of the dorsal ray. However, the 14 known species of Vexillata are characterized by fewer ridges (9-12), ridges of the careen long and thin; usually lack modifications of the synlophe at the ovejector level and, up to now, have never been reported from cricetids. The taxonomic value of all these characters (morphology, genetics, host specificity) will be assessed with an integrative approach. By the moment the scenario is rather puzzling, and we prefer to consider these specimens from O. phyllotis as Heligmosomoidea gen. sp. cf. Vexillata .

This is the first record of the Heligmosomoidea for O. phyllotis .

Figures

FIGURE 4. A. Posterior end of male specimen of Trichuris silviae from Heteromys gaumeri showing the slightly campanulate spicular sheath (arrow), lateral view. B. SEM micrograph of the anterior extremity of Monodontus sp. from Sigmodon toltecus showing the mouth opening, paired cutting plates and cervical papillae (arrow), ventral view. C. Cross section at midbody showing features of the synlophe of female Vexillata vexillata from Heteromys gaumeri. D. Male caudal bursa of Vexillata vexillata from Heteromys gaumeri, ventral view. E. Cross section at midbody showing features of the synlophe of male Heligmosomoidea gen. sp. cf. Vexillata from Ototylomys phyllotis. F. Cross section at midbody showing features of the synlophe of female Carolinensis sp. from Peromyscus yucatanicus. G. Cross section at midbody showing features of the synlophe of male Hassalstrongylus aduncus from Sigmodon toltecus. H. Cross section at midbody showing features of the synlophe of female Hassalstrongylus musculi from Oligoryzomys fulvescens. I. Male caudal bursa of Hassalstrongylus musculi from Ototylomys phyllotis, dorsal view. J. SEM micrograph of female Heligmostrongylus sp. from Peromyscus yucatanicus showing the discontinuous ridges, lateral view. K. Male caudal bursa of Heligmostrongylus sp. from Peromyscus yucatanicus, ventral view. L. Cross section at midbody of female Heligmonellidae gen. sp. from Sigmodon toltecus showing the absence of synlophe. Abbreviations: r, right side; v, ventral side. All cross sections of the synlophe orientated as in figure C.