Redescription and molecular analysis ofPallisentis(Pallisentis)nandaiSarkar, 1953 (Acanthocephala: Quadrigyridae) in India

Abstract

Pallisentis (Pallisentis) nandai Sarkar, 1953 is a freshwater fish parasite restricted to the Indian subcontinent in the Ganga River and its tributaries. It was described from the leaffish, Nandus nandus (Hamilton) from the Ganga River delta at Calcutta. We recovered variant specimens from the same host species from the Ganga near its headwaters at Bijnor about 1500 km away. Our specimens were clearly identifiable as P. nandai but varied considerably from those in the original description, especially in the size of proboscis hooks, receptacle and lemnisci. The original description was incomplete (missing line drawings of female trunk and reproductive system, male trunk, complete proboscis, hooks and hook roots) and inaccurate (proboscis, hooks, receptacle wall), and some measurements were lumped together for both sexes. We provide a complete description and include new morphological information including the first description of para-receptacle structure in the genus Pallisentis Van Cleave, 1928, scanning electron microscopy and microscope images, molecular analysis, and energy dispersive X-ray analysis (EDXA) of hooks and spines of our specimens for the first time. Additional details of proboscis hook roots, trunk spines, micropores and micropore distribution are described. The unique metal composition of hooks (EDXA) demonstrated a considerably high but variable level of sulphur and negligible level of calcium in collar and trunk spines and hook tips, but a higher level of sulphur and calcium at the hook basal arch than at the hook tip and edge. A comparison with the EDXA pattern of another species of Pallisentis, P. İndica Mital & Lal, 1976, were considerably different. The phylogenetic position of P. nandai within Eoacanthocephala was generated to assess the molecular characterization based on 18S and ITS1-5.8S-ITS2 ribosomal DNA sequences. Maximum likelihood and Bayesian inference analyses placed P. nandai in a clade with other Pallisentis species under the family Quadrigyridae. This is the first report based on molecular evidence for P. nandai.

Morphological and molecular description of Pallisentis roparensis n. sp. (Acanthocephala: Quadrigyridae) infecting the freshwater cat fish Wallago attu from Ropar Wetland, Punjab, India

“…Demidueterospinus , Brevitritospinus and Pallisentis based on the more consistent morphological characteristics like the difference in the size of the proboscis hooks from anterior to posterior circles, size of the cement gland and number of the giant nuclei of the cement gland. This sub-generic classification resolved the uncertainty related to the placement of different species within the genus contemporarily and was followed by Amin (2013) , Chaudhary et al (2019) , Gautam et al (2019) , Gautam et al (2020) , and Amin et al (2021) . Lately, the phylogenetic analyses based on the 18S gene marker by Chaudhary et al (2019) , Gautam et al (2020) and Rana and Kaur (2021) have shown monophyletic origin of the genus Pallisentis but create ambiguity within the genus.…”

“…The description of most of the Acanthocephalan species is lacking in complete morphological characterization which is based on few specimens and in addition the material cannot be referred due to the unavailability of the type specimens ( Amin et al, 2021 ). The species like P. channai Gupta et al, 2015 , Gupta et al, 2015 , P. vinodai Gupta et al (2015) and P. anandai Gautam et al (2017) were erected with incomplete morphological and molecular characterization and therefore are more likely to be questioned.…”

“…So far, molecular data of very few species is available in the database in comparison to the larger number of described species with incomplete and confusing morphological details. Some of the species described by Gautam et al (2019) , Chaudhary et al (2019) , Gautam et al (2020) and Amin et al (2021) have been supplemented with the molecular identity based on 18S molecular marker which is helpful to study the genetic divergence among the species in the same geographic location. Earlier to our study, only one species P. allahabadi Agarwal (1958) has been isolated from the W. attu from India.…”

The morphological and molecular description of Neoechinorhynchus (Neoechinorhynchus) poonchensis sp. n. from Schizothorax richardsonii (Gray) in Poonch, Jammu and Kashmir, India

“…Other species in different genera of acanthocephalans with single-walled proboscis receptacle also have single long ventral PRS. Examples include Acanthogyrus (Acanthosentis) parareceptaclis Amin, 2005 (Quadrigyridae) from Japan (Amin 2005), Intraproboscis sanghae Amin, Heckmann, Sist et Basso, 2021 (Gigantorhynchidae) from Central Africa (Amin et al 2021a), Pallisentis (Pallisentis) nandai Sarkar, 1953 (Quadrigyridae) from India (Amin et al 2021b), and Tenuisentis niloticus (Meyer, 1932) (Tenuisentidae) from Burkina Faso (Amin et al 2016). In Acanthogyrus (Acanthosentis) fusiformis Amin, Chaudhary, Heckmann, Ha et Singh, 2019, there are two long similar PRS inserting at the posterior end of the receptacle (Amin et al 2019b).…”

New perspectives of Microsentis wardae Martin & Multani, 1966 (Acanthocephala: Neoechinorhynchidae) from Gillichthys mirabilis Cooper in California, with scanning electron microscopy images and energy dispersive X-ray analysis

“…12). It was also prominent in whole hooks of Pallisentis nandai Sarkar, 1953 (see Amin et al , 2021) as well as in egg shells of Neoechinorhynchus qatarensis Amin, Saoud, Alkuwari, 2002 (see Heckmann et al , 2007). ‘The absence of sodium at the hook tip and its presence at the hook base and the opposite pattern of sulfur are characteristic of Neoechinorhynchus dimorphospinus Amin and Sey, 1996 hooks’ (Amin et al , 2019a, p. 616).…”