Hassalstrongylus aduncus (Chandler)

(= Longistriata adunca Chandler; = Longistriata norvegica Dikmans)

Site of infection: Small intestine

Host species: Sigmodon toltecus

Localities: Hobonil ranch, Vallazoo, Kuncheil cattle ranch (Yucatan), Ich ha lol xaan ecological park, Zoh Laguna community (Campeche), and Balam Nah eco-hotel (Quintana Roo)

Specimens deposited: CNHE 12016‒120221

GenBank accession numbers: OR271669, OR271677, OR271679

Comments: The specimens collected in the Yucatan Peninsula presented morphological characteristics in accordance with the original description given by Chandler (1932) for parasites of S. hispidus and the re-description by Durette-Desset (1972) from the same host, i.e., 23 cuticular ridges in the synlophe at midbody (Figure 4G); subsymmetrical bursa, with two well-developed lateral lobes and small dorsal lobe, bursal pattern type 1-4 with ray 2 well separated and divergent from the ray 3; dorsal ray with a thick trunk at the base and forking in the shape of an inverted U; and spicules 330–600 long with sigmoid tips.

In Mexico, Ha. aduncus has been reported from S. hispidus in Hidalgo and Jalisco (García-Prieto et al. 2012) and from S. toltecus and Rat. rattus in Yucatan (Panti-May et al. 2018). This is the first record of Ha. aduncus in Campeche and Quintana Roo. This finding extends the geographical range of Ha. aduncus in the Yucatan Peninsula.