Pseudoparamacroderoides seenghali Gupta & Agrawal, 1968

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 : 472-474

Type-species. Pseudoparamacroderoides seenghali Gupta & Agrawal, 1968

(Syns. Pseudoparamacroderoides vittati Kakaji, 1969 n. syn.; Pseudoparamacroderoides vittatusi Kakaji, 1969 [malformed suffix])

Records. 1. Gupta & Agrawal (1968); 2. Kakaji (1969); 3. Kumari et al. (1972).

Pseudoparamacroderoides seenghali was described as the type-species of Pseudoparamacroderoides for specimens collected from the intestine of giant-river catfish, Sperata seenghala (Sykes) (syn. Mystus seenghala [Sykes]) ( Siluriformes : Bagridae ), from the Gomti River (a tributary of the Ganges River) at Lucknow, Uttar Pradesh, India ( Gupta & Agrawal 1968). A year later and from the same locality, Kakaji (1969) added P. vittati (as P. vittatusi ) for one specimen gathered from the intestine of the striped dwarf catfish, Mystus vittatus (Bloch) ( Siluriformes : Bagridae ), and differentiated it from P. seenghali by the former possessing i) an ovary slightly distant from the ventral sucker posteriorly vs an ovary contiguous with the ventral sucker; ii) a seminal receptacle positioned lateral to the ovary vs post-ovarian; iii) the anterior extent of vitellarium located at the level of the anterior end of the ventral sucker vs at the level of the intestinal bifurcation or a little anterior (Note: the vitelline follicles appear distinctly post-bifurcal in the type illustration of P. seenghali [see Gupta & Agrawal 1968, p. 71]); iv) intercecal uterine coils vs coils that overlap the medial margins of ceca; v) an excretory vesicle extending up to the middle of the posterior testis vs up to the anterior margin of the anterior testis; and vi) different host species, M. vittatus vs S. seenghala . In their review, Truong et al. (2021) referred to the dubious and comparatively unjustified state of the aforementioned first four features (i.e., separation between the ovary and ventral sucker, seminal receptacle shape and position, the anterior extent of vitellarium, position of uterine coils relative to ceca) and considered the length or anterior extent of the excretory vesicle to be the only valid feature listed by Kakaji (1969) differentiating P. vittati from P. seenghali . We concur with Truong et al. (2021) except as concerns the anterior extent of the excretory vesicle. The short inter-testicular distance, and resultantly, the difference in location of the anterior extent of the excretory vesicle (either at the middle of the posterior testis or at the level of the anterior margin of the anterior testis) remains indistinctive and we feel it does not preclude conspecifity of P. vittati with P. seenghali . We can see this in different descriptions of the excretory vesicle of P. seenghali in Kakaji (1969) vs Gupta & Agrawal (1968). The anterior extent of the excretory vesicle terminates at the “anterior end [margin] of anterior testis” in P. seenghali (see Kakaji 1969, p. 73) whereas the type description of this species referred to the excretory vesicle as “passing between testes” and the type illustration shows this feature to extend to the mid-level of the anterior testis (see Gupta & Agrawal 1968, p. 70–71). Another example is the anterior extent of the vitellarium. Kakaji (1969, p. 73) stated that the vitelline follicles began from the level “of intestinal bifurcation or a little anterior to it” in P. seenghali whereas Gupta & Agrawal (1968, p. 72) stated the anterior extent of vitellarium “from middle or hind end of ventral sucker”. The implicit meaning of the original text in the Discussion of P. seenghali implies extra-cecal uterine coils (see Kakaji 1969, p. 73) which contradicts the illustration in the type description of P. seenghali which exhibits mainly inter-cecal uterine coils that may overlap the medial margins of the ceca but are not extra-cecal (see Gupta & Agrawal 1968, p. 71). Regarding the host-parasite data of P. seenghali and P. vittati , both hosts ( S. seenghala vs M. vittatus ) belong to the bagrid catfishes, Bagridae Bleeker , and to two closely related genera, the whiskered bagrid catfishes, Mystus Scopoli , and the Sperat bagrid catfishes, Sperata Holly , which share food and feeding habits (see Froese & Pauly 2022) and were captured from the same locality (the Gomti River at Lucknow, Uttar Pradesh, India). According to all aforementioned, we could not find any evidence for separating P. vittati as a distinct species from P. seenghali . Thus, with similarities in host taxa, locality, an absence of differential features, the enantiomorphic appearance of P. vittati with P. seenghali (see Gupta & Agrawal 1968, p. 71; Kakaji 1969, fig. 10), and the probable effects of host-induced variability, we synonymize P. vittati with P. seenghali and consider the features used by Kakaji (1969) and Truong et al. (2021) for differentiating both species as representative of intra-specific variation. Therefore, we consider these two taxa conspecific, P. vittati becoming a new synonym of P. seenghali .

Kumari et al. (1972) referred to the existence of a great amount of variation in A. reniferum after gathering a number of specimens from the intestine of two freshwater siluriform fishes at Kolkata (Calcutta), India: the Gangetic mystus, Mystus cavasius (Hamilton) ( Siluriformes : Bagridae ), and the Philippine catfish, C. batrachus . These variations included i) size of suckers, either equally or subequally sized; ii) presence of a prepharynx, either small or not evident; iii) esophagus length, between short to moderately long, and either straight to twisted; iv) intestinal bifurcation position, at mid-forebody level or more posterior; v) location of cecal ends where terminate, a little anterior to the posterior extremity or midway within the post-testicular space; vi) positioning of testes, tandem to obliquely tandem; vii) length of inter-testicular space highly variable; viii) anterior extent of cirrus-pouch, in region posterior to the ventral sucker to the middle of the ovary or extends further posterior; ix) cirrus-pouch, either claviform or twisted to nearly S-shaped; x) position of ovary in relation to ventral sucker, either overlapping/contiguous with ventral sucker or positioned between the ventral sucker and anterior testis; xi) difference in the ratio between the length and the width of the body; xii) vitellarium extent, from slightly posterior to the intestinal bifurcation anteriorly and to the posterior end of the posterior testis posteriorly; xiii) genital pore, either median or submedian; xiv) excretory vesicle shape, from I-shaped to Yshaped with intermediate phases; xv) variation in anterior extent of the excretory vesicle, between the level of the posterior testis to close to the ovarian level; and xvi) excretory pore, either terminal or subterminal. These variations were attributed to the degree of relaxation or contraction of specimens as well as time and state of fixation ( Kumari et al. 1972). Based on these variations, Kumari et al. (1972) synonymized Pseudoparamacroderoides with Astiotrema . We concur with Kumari et al. (1972) in the noticeable similarities between these two genera, but the I-shaped excretory vesicle represents a differential diagnostic feature for Pseudoparamacroderoides . Although Kumari et al. (1972, p. 320) stated that in A. reniferum there is great variation in excretory vesicle shape (i.e., “shape varies from ‘I’ to ‘Y’ with intermediate conditions”), our examination of their illustrations ( Kumari et al. 1972, figs. 2A–F) did not find a distinct Y-shaped excretory vesicle. Some of the excretory vesicles of these illustrated individuals appear to be transversely inflated at the distal end (i.e., anterior swelling); such a case was also observed in P. dongthapensis (see Truong et al. 2021, fig. 4). Regarding host-parasite data, Pseudoparamacroderoides is restricted to freshwater bagrid catfishes ( Mystus and Sperata ) (see Truong et al. 2021) whilst Astiotrema (sensu stricto) is distributed within a wide variety of host groups (i.e., reptilians, amphibians and freshwater fishes) (see Karar et al. 2021). However, neither M. cavasius nor C. batrachus has been reported as a host for any taxon of Astiotrema before and/or after Kumari et al. (1972). Mystus cavasius belongs to a commonly known host genus harboring taxa of Pseudoparamacroderoides (see Kakaji 1969; Agarwal & Kumar 1983; Agarwal & Agarwal 1984; Truong et al. 2021). Clarias batrachus is widespread along with M. cavasius in Indian freshwaters, and both share food and feeding habitats ( Froese & Pauly 2022). As a result, we believe that Kumari et al. (1972) erroneously identified their specimens as A. reniferum . These specimens represent a taxon that belongs to Pseudoparamacroderoides , most likely P. seenghali , based on their identical morphology, the same wide range of intraspecific variability observed, a sharing of the same and/or close host group, their nearby localities, and similar host feeding habitats.

We also noted that one of the most striking variations observed in P. seenghali is the position of the cirrus-pouch relative to the ventral sucker and ovary which varies from either confined to the area between the ovary and ventral sucker (see Kakaji 1969, fig. 10; Kumari et al. 1972, figs. 1A & 1E) or positioned laterally in the same direction from both the ventral sucker and ovary (i.e., ventral sucker situated between ovary and cirrus-pouch) (see Gupta & Agrawal 1968, p. 71; Kumari et al. 1972, figs. 1B–D & 2B). Such a case has been observed in other digeneans (e.g., A. impletum – see Karar et al. 2021); thus, with the absence of distinct morphometrical and/or obvious morphological variation as well as the sharing of the same host group, food/ feeding habits and nearby localities, we consider this variability (i.e., positions of the cirrus-pouch relative to the ventral sucker and ovary) as an example of intraspecific variation and not indicative of a lack of con-specificity with P. seenghali across these three studies.