Anenterotrema auritum Stunkard, 1938

Lunaschi, Lía I. & Drago, Fabiana B., 2011, A revision of Anenterotrema Stunkard, 1938 (Digenea: Anenterotrematidae) and a key to its species, Zootaxa 2775, pp. 50-64 : 51-52

Anenterotrema auritum Stunkard, 1938

( Figure 1 ; Table 1)

Syn. Anenterotrema singulare Stunkard, 1938 (new synonymy)

Material studied. Holotype, 21 paratypes, wholemounts and specimens in cross-sections AMNH. Ex Micronycteris megalotis mexicana Miller (Phyllostomidae) (type host); small intestine; Xmahit Cave, Tekax (type locality), Yucatan, Mexico.

Holotype in cross-sections, AMNH. Ex Natalus stramineus mexicanus Miller (as Natalus mexicanus Miller ) ( Natalidae ) (type host of A. singulare ); Balaam Cave, Chichen Itza, Yucatan, Mexico.

Hosts. Phyllostomidae : M. megalotis mexicana ; Glossophaga soricina (Pallas) ; Phyllostomus discolor Wagner ; Natalidae : N. stramineus mexicanus .

Distribution. Mexico (Yucatán: Xmahit Cave, Tekax (type locality); Xconsacab, Tizamin; Balaam Cave, Chichen Itza); Belize (Shipstern Nature Reserve and North-Eastern Belize); Colombia (Jardín Botánico de Medellin).

References. Stunkart (1938); Castiblanco & Vélez (1982); Bärtschi (2000).

Redescription. [Based on 3 extended specimens, 7 contracted specimens and cross-sections] Body small, fusiform, with maximum width at level of testis. Forebody 1.2–2.4 times smaller than hindbody. Ratio of body length to forebody length 1:3–4. Tegument unarmed. Anterior end with transverse fold of body wall dorsal to oral sucker and extending laterally or ventro-laterally in form of 2 papilliform processes. Oral sucker spherical, large, subterminal. Ventral sucker spherical, similar in size to oral sucker, in middle third of body. Pharynx, oesophagus and intestinal caeca absent. Gonads in anterior region of hindbody. Testes enormous, spherical to oval, entire, symmetrical. Cirrus sac smaller than ventral sucker, entirely anterior to or slightly overlapping ventral sucker; containing long, coiled internal seminal vesicle, pars prostatic, prostatic cells concentrated anteriorly and cirrus. Genital atrium shallow, with thin wall. Genital pore median, anterior to ventral sucker. Ovary spherical, sub-median, overlapping testis dorsally. Mehlis’ gland post–ovarian; Laurer’s canal short; uterine seminal receptacle in proximal region of uterus surrounded by Mehlis’ gland cells. Vitellarium follicular, in hindbody just posterior to gonads, in right lateral field of body, partly masked by loops of uterus. Uterus thin-walled, extensive, occupies entirely hindbody. Metraterm thick-walled, strongly muscular, with length similar to that of cirrus sac, opens anterior to cirrus sac into genital atrium. Eggs operculate, with yellow coloration, small in relation to body size. Excretory pore terminal; excretory vesicle not seen.

Remarks. Of all the known species of Anenterotrema , A. auritum is the only one characterized by possessing enormous testes ( Fig. 1 A, B, E). Moreover, it has a transverse fold dorsal to the oral sucker, extending laterally, or ventro–laterally, as two papilliform processes ( Fig. 4 C, D). These processes are apparent as two cells in specimens with the anterior end somewhat withdrawn into the forebody ( Fig. 1 F). Specimens with this characteristic have been found by Stunkard (1938) parasitizing M. megalotis mexicana from Mexico, and by Castiblanco & Vélez (1982) parasitizing P. discolor from Colombia. Furthermore, Stunkard (1938) described A. singulare on the basis of a single adult specimen found in N. stramineus mexicanus from Mexico, which was sectioned by the author to enable the study of its internal structures. This author observed similarities between A. auritum and A. singulare in the arrangement and distribution of the vitellarium and the course of the uterus, and differences in the size of the suckers, gonads and cirrus sac. However, our re-examination of type material of A. auritum extends the size range for these organs (Table 1). Since the specimen from N. stramineus mexicanus is identical to those from M. megalotis mexicana in general appearance and in almost all metrical features (Table 1), we consider A. singulare to be a junior synonym of A. auritum .

Portes Santos & Gibson (1998) and Gibson & Portes Santos (2008) considered that one of the most important differences between the genera Anenterotrema and Apharyngotrema is the body size, less than 1 mm in the first, and more than 1 mm in the second. The specimens described by Castiblanco & Vélez as A. auritum from Colombia are greater than 1 mm (0.9–1.41 mm) in length, but, given that they have the transverse fold at the level of oral sucker, which is absent in Apharyngotrema, and that they are morphologically similar to the specimens described by Stunkard and that most of the ratios are coincident (Table 1), we consider the differences in size as intraspecific variations.

Conversely, the specimens described by Zdzitowiecki & Rutkowska (1980) in Cuba as A. auritum fall well outside the minimum values reported for this species (Table 1–2). According to this study, the metrical data and ratios calculated for the specimens described by these authors are closely related to those given by Freitas (1960) for A. eduardocaballeroi . Therefore, we consider that these specimens belong to the latter species.

Figures

FIGURE 1. Anenterotrema auritum. A – D, holotype. A – B, dorsal view. C – D, anterior end showing the transverse fold of the body wall. E – G, paratype. E, ventral view. F, anterior end. G, detail of the terminal genitalia. Scale bars: A – B: 200 μm; C and E: 100 μm; D and F: 50 μm.

FIGURE 4. Anenterotrema stunkardi. A – C paratypes CNHE 1452, ventral view. B, enlarged view of terminal genitalia. Scales: A and C: 200 μm; B: 100 μm.