Brachylaima sp. Site of infection: Small intestine. Host species: Didelphis virginiana. Localities: Umán and Mérida (Yucatán). Prevalence: 33.3% (2/6). Mean intensity: 28 (range 6‒50). Specimens deposited: CNHE 12898, 12899. GenBank accession number: PP662453. Comments: Specimens of Brachylaima with an elongated body (2,810 –4,050 long by 450–700 in maximum width), covered with fine spines (Figure 1A). Oral (245–320 long by 220–290 wide) and ventral (250–315 long by 220–260 wide) suckers situated in the anterior part of body (Figure 1B). Gonads in tandem near to the posterior extremity of the body. Testes oval and similar in size; anterior testis 235–360 long by 150–370 wide, posterior testis 240–405 long by 150–375 wide. Ovary small, 100–170 long by 129–220 wide. Genital pore posterior, close to the anterior testis. Vitellaria in two lateral fields, reaching anteriorly to level of ventral sucker, posteriorly about level of anterior testis. Eggs numerous, ovoid, 29–30 long by 20–17 wide. These specimens are morphologically closest to Brachylaima virginianum (Dickerson), originally described from D. virginiana in Virginia, USA. However, B. virginianum differs from the studied specimens by a smaller body length (1,535 –2,541 vs 2,810 –4,050) and shorter anterior (177–205 vs 235–360) and posterior (123–204 vs 240–405) testes. The oral sucker is distinctly larger (246– 286) than the ventral sucker (150–205) in B. virginianum, while in the studied specimens the suckers have somewhat similar size (245–320 and 250–315). Brachylaima didelphus Premvati & Bair, another trematode recorded in D. virginiana from Mexico (Acosta-Virgen et al. 2015), differs from the studied specimens by the vitellaria position (Premvati & Bair 1979) (from the pharynx to the end of the body vs. from the ventral sucker to anterior testis). Therefore, we consider that the specimens from Yucatán could represent a putative new specie. Two known species of Brachylaima have been reported from D. virginiana in Mexico: B. virginianum in Mexico State (Monet-Mendoza et al. 2005) and B. didelphu s in Campeche (Acosta-Virgen et al. 2015). In addition, an unidentified species of Brachylaima was reported from D. virginiana in Guerrero (Monet-Mendoza et al. 2005). Our finding represents the first record of the genus Brachylaima in the Yucatán Peninsula.

Published as part of Panti-May, Jesús Alonso, Chan-Casanova, Anyela Jackelin, Canche-Pool, Elsy, Tello-Martín, Raúl, Ruiz-Piña, Hugo, Concha-Guillermo, Henry, Guiascón, Oscar Retana-, Vega, Pedro Pablo Martínez, Chablé-Santos, Juan, Martínez, Erendira Estrella-, Moguel-Chin, Wilson Isaias, Hernández-Orts, Jesús S., Hernández-Mena, David I., Mendoza-Garfias, Berenit & García-Prieto, Luis, 2024, Morphological and molecular data on helminths of Didelphis virginiana and Philander vossi (Mammalia: Didelphidae) from the Yucatán Peninsula, southeast Mexico, pp. 1-24 in Zootaxa 5463 (1) on page 4, DOI: 10.11646/zootaxa.5463.1.1, http://zenodo.org/record/11609981