Anoplostrongylus allami, Moguel-Chin & Suárez-Galaz & Casanova & Concha-Guillermo & Tzec-Che & Robles & Digiani & Hernández-Orts & Ruiz Torres & Macswiney & Panti-May, 2025

Anoplostrongylus allami sp. nov. Panti-May & Digiani

Infection site: Intestine

Localities: Calcehtok and Homún

Prevalence (%) and mean intensity: Calcehtok 89.7 and 13.3 (11.4‒16.6). Homún 90.6 and 13.5 (11.5‒16.4)

Specimens deposited: Holotype male (No. 12316), Calcehtok; allotype female (No. 12317), Calcehtok; and paratypes (No. 12318, 12319, 12320), Calcehtok and Homún, deposited at the CNHE . Paratypes from Calcehtok desposited at the NHM (2025.8.13.9‒12)

GenBank accession numbers: PX232572‒PX232574 (28S) and PX227565, PX227566 (COI)

ZooBank Life Science Identifier: 6949A151-EABB-475C-84CA-88537D612937

Etymology: This species is named in honor of the late Allam Tzab Pech (1992–2024), a friend, biologist, and passionate bat conservationist from Yucatán, who supported our fieldwork in Homún during the early stages of the project.

Description: General. Medium-sized nematodes. Sexually dimorphic, females larger than males. Oral opening circular with two amphids and six external labial papillae ( Figure 7A‒B View FIGURE 7 ). Dorsal esophageal tooth conspicuous ( Figure 7A View FIGURE 7 ). Nerve ring situated at middle of esophagus; excretory pore located posterior to nerve ring; deirids simple at about same level than excretory pore ( Figure 6A‒B View FIGURE 6 ).

Cephalic vesicle: In males, campanulate with two distinct portions, posterior portion longer ( Figures 6A View FIGURE 6 , 7A View FIGURE 7 ). In females, umbelliform divided into three distinct portions: first one short, second longer, and third with dorsal and ventral notches ( Figures 6B View FIGURE 6 , 7B View FIGURE 7 ).

Synlophe (studied in two males and two females): Cuticle with longitudinally continuous ridges ( Figures 7C‒ H View FIGURE 7 ); oriented ventral to dorsal. Ridges appearing posterior to cephalic vesicle ( Figures 7C‒D View FIGURE 7 ) and disappearing anterior to caudal bursa in males ( Figure 7E, G View FIGURE 7 ) and anterior to cuticular tubercles in females ( Figure 7F, H View FIGURE 7 ). Males: two ridges at level of distal esophagus, 8‒9 at mid-body, and 9‒10 at level of proximal portion of spicules ( Figure 6C‒E View FIGURE 6 ). In the anterior and middle region of the body, the two lateral ridges associated with lateral hypodermal cords widening to form alae; lateral alae are the only ridges present at esophageal level ( Figure 7C View FIGURE 7 ), other ridges appearing posterior to esophagus. Females: 14‒15 ridges at level of distal esophagus, 18‒19 at mid-body, and 15‒16 anterior to caudal tubercles ( Figure 6F‒H View FIGURE 6 ). In esophageal region, lateral ridges associated with lateral hypodermal cords also form alae; at midbody and at posterior part of body lateral ridges with same development as the remaining ridges.

Males (based on holotype and 11 paratypes): 3, 3 ± 0.3 (3–4) mm long and 88, 76 ± 13 (60–100) wide at mid-body. Cephalic vesicle 30, 27 ± 3 (22–30) × 25, 28 ± 3 (22–32). Nerve ring, excretory pore, and deirids situated at 155, 157 ± 12 (140–175), 195, 184 ± 20 (158–230), and 202, 195 ± 19 (175–240) from apex, respectively. Esophagus 320, 309 ± 26 (275–368) long. Bursa bell-shaped, with dorsal lobe poorly developed and accessory internal membrane ( Figure 7E, G View FIGURE 7 ). Bursal pattern of type 2‒3. Rays 2 and 3 longest, with short common trunk; rays 2 strongly curved toward median line, papillae 2 close to each other. Rays 4‒6 with common trunk, rays 4 barely shorter, diverging first and slightly isolated from rays 5 and 6. Rays 8 long, arising symmetrically from proximal third of dorsal ray. Dorsal ray short, divided at distal third into two branches, each one bifurcated at proximal third into two sub-branches, rays 9 (external) and rays 10 (internal). Rays are 9 shorter than rays 10, arising at same level of dorsal ray bifurcation. Rays 10 bearing each a small internal projection ( Figures 6I–J View FIGURE 6 ), probably phasmids. Genital cone small 40, 26 ± 5 (20–35) long and 40, 33 ± 6 (22–45) wide at base, with dorsal lip tapering distally and bearing two ventral papillae and a distal protuberance in form of lappet ( Figure 6I View FIGURE 6 ). Spicules subequal, with a minute salient subterminal hook ( Figure 6K View FIGURE 6 ). Spicules length 115, 129 ± 6 (120–142), representing 4, 5 ± 0.5 (4–5) % of body length. Gubernaculum 50, 43 ± 6 (32–50) long and 12, 11 ± 2 (8–15) wide, tapering at distal part ( Figure 6L View FIGURE 6 ).

Females (based on allotype and 11 paratypes): 7, 8 ± 1 (6–10) mm long and 210, 185 ± 35 (150–250) wide at mid-body. Cephalic vesicle, 60, 66 ± 12 (50–95) × 110, 95 ± 10 (80–110). Nerve ring, excretory pore, and deirids at 190, 240 ± 30 (190–280), 220, 280 ± 38 (212–330), and 240, 309 ± 43 (235–360) from apex, respectively. Esophagus 455, 483 ± 42 (400–542) long. Didelphic, amphidelphic. Branches of ovejector divergent or both directed anteriorly then curving posteriorly ( Figure 6N View FIGURE 6 ). Vulva at 5, 6 ± 1 (4–8) mm from anterior extremity, representing 73%, 74 ± 1 (72–76) of body length. Vagina vera 100, 92 ± 26 (65–160) long. Ovejector with posterior branch of vestibule slightly longer than anterior one; anterior branch 95, 72± 12 (65–95) long, posterior branch 100, 97 ± 15 (75–125) long. Anterior sphincter and infundibulum 50, 48 ± 8 (40–68) and 105, 95 ± 13 (75–120) long, respectively; posterior sphincter and infundibulum 52, 46 ± 9 (40–65) and 100, 83 ± 17 (50–110) long, respectively. Most gravid females with 17, 13 ± 16 (2–59) eggs in different embryonic development stages; eggs containing juvenile stage observed only in two females. Segmented eggs, 76 ± 8 (62–90) × 47 ± 6 (35–55) (based on 20 eggs measured from 11 paratypes). Eggs with juvenile stage, 72 ± 6 (68–80) × 52 ± 5 (45–55) (based on four eggs measured from allotype and one paratype). Anus 80, 82 ± 5 (70–90) from posterior extremity. Tail with three conical, sharp tubercles (two latero-ventral and one dorsal), and one thin, ventral spine 40, 44 ± 4 (38–50) long with a subterminal swelling ( Figures 6M View FIGURE 6 , 7H View FIGURE 7 ). A small papilla (probably phasmid) behind each latero-ventral tubercle ( Figure 7H View FIGURE 7 ).

Remarks: The monotypic genus Anoplostrongylus was created to accommodate the species Histiostrongylus paradoxus Travassos described from N. laticaudatus in Brazil. This species was characterized by the absence of spines in the cephalic vesicle, the presence of three tubercles and a terminal spine on the female tail, and spicules with barbed distal extremities ( Boulenger 1926). Later, Travassos (1937) expanded the generic definition to include the marked difference in size between males and females, the umbelliform cephalic vesicle of females; the postequatorial vulvar opening located within a depression; the bursa with reduced dorsal lobe, lateral rays decreasing in length from anterior to posterior, rays 8 arising from base of dorsal ray and dorsal ray forking distally, and the elongated gubernaculum.

Anoplostrongylus paradoxus was redescribed in detail by Lent et al. (1946) based on the type material and newly collected specimens; the synlophe of the species in transverse sections was described by Durette-Desset & Pinto (1977), also using the Brazilian type material.

Anoplostrongylus allami sp. nov. shares most of the morphological characters (e.g., sexual dimorphism in size, cephalic vesicle and synlophe; pattern of bursal rays; female tail) and biometrics (e.g., body length, spicules length, distance from vulva to anus). However, A. allami differs from A. paradoxus by the number of portions of the cephalic vesicle of males (two vs. three), the shape of the proximal half of the gubernaculum (asymmetric vs. symmetric) and, especially, by the marked sexual dimorphism in the ridge number and development. Durette-Desset & Pinto (1977) specified for A. paradoxus the same synlophe in both sexes at mid-body (19 ridges with similar development), but, at the anterior part of body the number and development of ridges differed in males and females: males with seven ridges of which the two lateral are developed forming lateral alae; and females with 18 ridges of which the two lateral ones are barely more developed than the other ones. In A. allami , males and females differ in their synlophe not only at the esophageal region but also at midbody. At level of distal esophagus, females possess 14‒15 ridges of which the two lateral form the lateral alae; and males possess only the two ridges forming the lateral alae. At mid-body, males possess 8‒9 ridges and the lateral alae are preserved, whereas females possess 18–19 ridges and the lateral alae disappear.

Anoplostrongylus allami and A. paradoxus share the same type of dimorphism on the cephalic vesicle. This structure in females shows dorsal and ventral notches whereas that of the male does not. That is why we consider that the generic definition of Anoplostrongylus should be further expanded to incorporate the sexual dimorphism of both the cephalic vesicle and the synlophe as important features.

Sexual synlophial dimorphism has been documented not only in Anoplostrongylus but also in other genera of Anoplostrongylinae parasitic in New World bats. In Molostrongylus mbopi Durette-Desset & Vaucher , a parasite of Molossops sp. from Paraguay, males possess a maximum of four ridges (lateral alae plus two other ridges) between the esophago-intestinal junction and the caudal bursa, whereas in females the number of ridges increases progressively with body length from four ridges at the esophago-intestinal junction (including the two lateral alae) to 24 ridges behind the vulva ( Durette-Desset & Vaucher 1999). A case of extreme sexual dimorphism of the synlophe is found in Macuahuitloides inexpectans Jiménez, Peralta-Rodríguez, Caspeta-Mandujano & Ramírez-Díaz a parasite of M. megalophylla in Mexico in which males exhibit at mid-body 12 ridges, oriented ventral to dorsal, whereas females lack a synlophe. This latter species is also characterized by sexual dimorphism of the anterior part of the body. Males exhibit a simple, cap-like cephalic vesicle, whereas in females this structure is smooth and not prominent and is followed by a series of minute spines arranged in spiral rings covering the first quarter of body length ( Jiménez et al. 2014).

Comments: Specimens of A. allami had been already isolated from N. laticaudatus in the same two sites sampled in the present study, and were treated provisionally as Anoplostrongylus sp. in Moguel-Chin et al. (2023).