Anomalomacroderoiditrema, Karar & Blend & Dronen & Adel, 2023

Karar, Yasser F. M., Blend, Charles K., Dronen, Norman O. & Adel, Asmaa, 2023, Towards resolving the problematic status of the digenean genus Astiotrema Looss 1900: Taxa excluded from Astiotrema (sensu stricto) with special reference to plagiorchioid genera closely related to the restricted concept of Astiotrema, Zootaxa 5284 (3), pp. 445-495 : 478-480

Genus Anomalomacroderoiditrema n. gen.

( Fig. 27 )

Type- and only species. Anomalomacroderoiditrema keni ( Agarwal & Agarwal, 1984) n. comb.

(Syn. Pseudoparamacroderoides keni Agarwal & Agarwal, 1984 )

Etymology. The generic designation is based on the Greek word roots “anomalos, macro, deros, trema” meaning “dissimilar/unlike, large/big, long or long-lived & Trematoda ”, respectively, and refers to the dissimilarities of this genus compared to all taxa of the Macroderoididae , wherein one species now composing this genus was originally considered.

Diagnosis. Body small, elongate oval, spatulate. Tegument spinous. Forebody approximately 1/3 of body length. Suckers subglobular, unspecialized. Oral sucker ventro-subterminal. Ventral sucker, pre-equatorial, at anterior half of the second 1/3 of body, more or less equal to oral sucker in size. Prepharynx prominent. Pharynx well developed, smaller than suckers. Esophagus short, thin-walled, straight. Intestine bifurcates in posterior extremity of forebody, slightly dorsal to ventral sucker, near posterior end of first 1/3 of body. Ceca terminate in post-testicular space, a little anterior to posterior end of body. Testes two, intercecal, smooth, oblique to obliquely tandem, subglobular, separated by large inter-testicular space. Cirrus-pouch clavate, dextral to midbody line, extends around right margin of ventral sucker from its posterior margin up to intestinal bifurcation, does not extend into hindbody. Internal seminal vesicle large, thick-walled, unipartite, occupies approximately 1/3 space in cirrus-pouch. Pars prostatica short, tubular; few glandular cells around pars prostatica or upper aspect of seminal vesicle. Ejaculatory duct long, tubular, distinct from pars prostatica. Genital atrium shallow, inconspicuous. Genital pore submedian, extra-cecal, bifurcal. Ovary lobed, intercecal, pre-equatorial, posterolateral to ventral sucker or abutting it. Canalicular seminal receptacle distinct, post-ovarian, variable in size, elliptical to saccate. Vitellarium follicular, cecal to slightly extracecal, fields extend between pharyngeal level and cecal ends; anterior extent of vitellarium pre-bifurcal or bifurcal; posterior extent slightly anterior to cecal extemities. Uterus inter and post-cecal, fills most of hindbody posterior to ovary, extends to posterior extremity. Metraterm distinct, alongside cirrus-pouch. Eggs numerous, operculated, elliptical, unfilamented, tanned, unembryonated in uterus. Excretory vesicle I-shaped, extends to testicular level. Excretory pore terminal. In intestine of freshwater bagrid catfishes; South Asia (e.g., Indian subcontinent).

Pseudoparamacroderoides keni was proposed by Agarwal & Agarwal (1984) for four specimens collected from the intestine of the striped dwarf catfish, Mystus vittatus , captured from the Ken River, a tributary of the Ganges River, Panna District, Madhya Pradesh, India. Agarwal & Agarwal (1984) differentiated P. keni from P. seenghali (and its synonym P. vittati ) by the vitellarium extending from pharyngeal level to a little anterior to cecal extremities and a short esophagus. It further differed from the original description of P. seenghali by possessing a prepharynx and from P. vittati (= P. seenghali ) in the sucker ratio. We agree with Truong et al. (2021) in considering the anterior extent of the vitellarium to the intestinal bifurcation – and we add that the vitellarium can be seen to reach to the pharnyx (see Agarwal & Agarwal 1984, fig. 1B) – as a valid diagnostic feature for differentiating P. keni from other taxa of Pseudoparamacroderoides , and we do not consider taxonomically informative the last-three aforementioned features (i.e., short esophagus, presence of a short prepharynx and sucker ratio) based on our earlier comparisons and overlap with features described and illustrated for P. seenghali (and its synonym P. vittati ) (see Gupta & Agrawal 1968, p. 71; Kakaji 1969, p. 73; Kumar et al. 1972, figs. 1 & 2).

Furthermore, Agarwal & Agarwal (1984) provided three diagnostic features that we feel are sufficient to differentiate P. keni from all taxa of Pseudoparamacroderoides as well as this species from all taxa of the Macroderoididae . These features are: i) a lobed ovary appearing partially tri-lobed ( Agarwal & Agarwal, 1984, figs. 1A & 1C) to irregularly shaped ( Agarwal & Agarwal, 1984, fig. 1B); ii) a ventral sucker that overlaps the posterior portion of the intestinal bifurcation and left cecum at its origin ( Agarwal & Agarwal, 1984, figs. 1A & 1B); and iii) a submedian, extracecal genital pore, sinistral to the intestinal bifurcation.

One of the most controversial and ambiguous observations we noted in our research was the orientation of the type illustrations of P. keni . Specifically, where Agarwal & Agarwal (1984) for their figs. 1A–1C stated that they were drawn in ventral view. In contrast, our findings reveal these illustrations possess aspects of both ventral and dorsal views. Figures (1A–C) show the ovary over the ventral sucker which, in turn, represents a dorsal view, whereas the original illustrations were stated as drawn in a ventral view (see also our Fig. 27 ). The ventral sucker and genital pore were illustrated over the cecum, which reflects a ventral aspect. In the main text, Agarwal & Agarwal (1984) stated that the genital pore was positioned “extracaecal on left side of intestinal bifurcation”, whilst based on the aforementioned ventral view of their illustrations, the genital pore is apparently on the right side of the intestinal bifurcation. To avoid confusion, we suggest changing the orientation of the illustrations of Agarwal & Agarwal (1984) from a ventral view to a dorsal view so as to be consistent with the original text (i.e., “genital pore on the left side of intestinal bifurcation”) and to remove the ambiguity regarding the position of the ovary over the ventral sucker.

Based on what we think in P. keni are distinct generic-level morphological features (i.e., the combination among the aforementioned three characteristics along with the distinctive extent of the vitellarium), we believe P. keni neither belongs within Pseudoparamacroderoides , related taxa (e.g., Macroderoides and Paramacroderoides ) nor any other macroderoidid genus and is in need of its own genus. Therefore, we propose Anomalomacroderoiditrema n. gen. to accommodate specimens of P. keni as its type-species, Anomalomacroderoiditrema keni ( Agarwal & Agarwal, 1984) n. comb.

Figures

FIGURES 26 & 27. Alloglossidium raychaudhurii (Agarwal & Kumar, 1983) n. comb. and Anomalomacroderoiditrema keni (Agarwal & Agarwal, 1984) n. gen., n. comb. 26. Al. raychaudhurii (syn. Pseudoparamacroderoides raychaudhurii Agarwal & Kumar, 1983), ventral view, redrawn from Agarwal & Kumar (1983, fig. 1A). 27. An. keni (syn. Pseudoparamacroderoides keni Agarwal & Agarwal, 1984), dorsal view, redrawn from Agarwal & Agarwal (1984, fig. 1A). Abbreviations: AT, anterior testis; BS, body spines; Ce, cecum; CP, cirrus-pouch; ED, ejaculatory duct; Eg, egg; EP, excretory pore; Es, esophagus; EV, excretory vesicle; GP, genital pore; LC, Laurer’s canal; OC, ôtype complex; OS, oral sucker; Ov, ovary; Ph, pharynx; PP, pars prostatica; Pr.Ph, prepharynx; PT, posterior testis; SR, seminal receptacle; SV, seminal vesicle; Ut, uterus; VD, vitelline duct; VF, vitelline follicle; VS, ventral sucker. Scale bars: Fig. 26 = 500 µm; Fig. 27 = 300 µm.