Rodentolepis microstoma (Dujardin, 1845)

Martins, Natalia Beatriz Guerreiro, Robles, María del Rosario, Knoff, Marcelo, Navone, Graciela Teresa & Callejon, Rocío, 2022, Rodentolepis microstoma isolated from different species of Sigmodontinae rodents (Rodentia: Cricetidae) in the Cuenca del Plata, Argentina: Morphological aspects and molecular characterization, International Journal for Parasitology: Parasites and Wildlife 19, pp. 56-67 : 60-61

3.1.1. Rodentolepis microstoma ( Figs. 1 and 2 )

Amended diagnosis: Cyclophyllidea , Hymenolepididae . Strobila long, craspedote, with proglottids wider than long, and in gradual maturation. Scolex with four muscular suckers. Rostellum armed with a single crown of hooks of the cricetoid type (Nº = 22–31), retractable into contractile rostellar pouch. Entire worm covered with acicular filitriches (sensu Chervy, 2009). Young proglottids contain only primordia of testes. Mature proglottids containing three spherical to oval testes, arranged one poral and two aporal, are disposed aligned or in a triangle; vas deferens form an external seminal vesicle; cirrus sac ovoid, does not touch or extends beyond osmoregulatory canals, enclosing cirrus smooth and internal seminal vesicle; lobated ovary, located in the medial zone; vitelline gland compact, lobated, median; vagina located below the cirrus sac; well-developed seminal receptacle, visible even in gravid proglottids; common genital pore unilateral, dextral, near the midpoint of the margin. In gravid segments, the uterus occupies almost the entire proglottid, and contains numerous eggs. Eggs are ovoid, enclosing embryophore with polar filaments (difficult to observe) and oncosphere with embryonic hooks.

3.1.2. Taxonomic summary

Rodent hosts: Mus musculus Linnaeus, 1758 , Apodemus spp. Kaup, 1829, Mastomys spp. Thomas, 1915, Mus musculus Linnaeus, 1758 , Rattus norvegicus , R. rattus , Meriones spp. Illiger, 1811 ( Muridae ); Dendromus spp. Smith, 1829 ( Nesomyidae ); Mesocricetus auratus (Waterhouse, 1839) , Microtus spp. Schrank, 1798, Akodon azarae , A. dolores ,

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A. montensis , A. philipmyersi , Necromys lasiurus , Thaptomys nigrita , Oxymycterus misionalis , O. rufus . ( Cricetidae ) ( Hughes, 1940; Dvorak et al., 1961; Litchford, 1963; Cunningham and Olson, 2010; Guerreiro Martins et al., 2014; Panisse et al., 2017; Panti-May et al., 2018).

New localities: see Table 1.

Voucher specimens: MLP-He 6804, 6806, 6810, 6811, 7592-7622.

Remarks: The specimens here studied show diagnostic morphological features of genus Rodentolepis and the parasitic species of American rodents are compared below (Czaplinski and Vaucher, 1994).

Rodentolepis microstoma can be separated from R. evaginata (Barker and Andrews, 1915) , R. johnsoni (Schiler, 1952) , R. octocoronata (Von Linstow, 1879) and R. oregonensis ( Neiland and Senger, 1952) by the number of rostellar hooks (22–31 vs. 10, 10, 8, 10, respectively). The specimens of R. microstoma studied have scolex smaller than R. nana (Von Siebold, 1852) and R. octocoronata (0.07–0.23 vs. 0.30–0.40, 0.39, respectively). Moreover, R. microstoma has the cirrus sac longer than R. nana and R. johnsoni (0.04–0.17 x 0.02–0.05 vs. 0.05–0.07 x 0.02–0.025, 0.11 x 0.04, respectively), and is smaller than R. octocoronata (0.04–0.17 x 0.02–0.05 vs. 0.30 x 0.37). Rodentolepis microstoma can be separated from R. evaginata , R. nana , R. octocoronata , R. oregonensis and R. srivastavai (Rˆego, 1970) by the size of the eggs (Barker, 1915; Neiland and Senger, 1952; Schiller, 1952; Wardle and McLeod, 1952; Rˆego, 1970; Sutton, 1974).

Although some features, e.g., cirrus sac, size of eggs, length and shape of hooks, may separate R. microstoma and R. srivastavai , these should be reviewed in detail, (Rˆego, 1970). In addition, R. microstoma and R. akodontis show a similar morphology of scolex, length and shape of hooks, number of rostellar hooks, size of suckers, size of cirrus sac and eggs (e.g., Rˆego, 1967; Casanova et al., 2001; Cunningham and Olson, 2010; Gomez-Puerta and Valdivia-Carrera, 2018).

Figures

Fig. 1. Morphological features of Rodentolepis microstoma: (A, D, G, J) scolex and rostellar hooks; (B, E, H, K) mature proglottids; (C, F, I, L) egg from different host species, (A–C) Akodon; (D–F) Necromys; (G–I) Thaptomys; (J–L) Oxymycterus.

Fig. 2. Scanning electron micrographs of Rodentolepis microstoma: (A) scolex with invaginated rostellum, lateral view; (B) scolex with invaginated rostellum, apical view; (C) acicular filitriches (mature proglottids). Histological section of Rodentolepis microstoma: (D) testes (t), ovary (o), external seminal vesicle (esv), cirrus sac (cs) and cirrus (c) in mature proglottid.