Proboscis Hooks Research Articles

Semibalanus balanoides (L.) and Balanus crenatus Bruguière (Balanidae) Are Intermediate Hosts of Fimbriarioides intermedia (Fuhrmann, 1913) and Two Species of the Genus Microsomacanthus (Cestoda: Hymenolepidae), Parasites of Sea Ducks from the Atlantic Sector of the Arctic and Northern Pacific.

Metacestode infestation of Semibalanus balanoides (L., 1767) and Balanus crenatus Bruguiеre, 1789, collected in the Barents and White Seas and in the northern part of the Sea of Okhotsk in 2020 and 2021, respectively, was studied. A total of 313 S. balanoides from Mogilnaya Bay of Kildin Island (Barents Sea) and isolated mature wrinkled barnacles B. crenatus, two and four specimens from the Pechora Sea and Kandalaksha Bay of the White Sea, respectively, were examined in 2020. Metacestodes Fimbriarioides intermedia (Fuhrmann, 1913) (Cyclophyllidea, Hymenolepididae) were found in 1.0 ± 0.6% of S. balanoides in the Barents Sea with an invasion intensity (I. I.) of 2-5 specimens, and in one of two B. crenatus from the Pechora Sea (I. I. 15 specimens). For the first time, in both B. crenatus from the Pechora Sea, taken from the valves of the mussel Mytilus edulis, metacestodes Microsomacanthus sp. I (I. I. 13 and 20 specimens) with proboscis hooks 38-41 (39.4 ± 0.1) µm long and blades of 9.5-11 (10.7 ± 0.1) µm were obtained. One of four B. crenatus from the Kandalaksha Bay was infected with another Microsomacanthus sp. II (I. I. 19 specimens) with proboscis hooks 44.0-49.5 (45.7 ± 0.5) µm long and blades 14.0-16.0 (14.8 ± 0.07) µm long. A total of 362 S.balanoides were collected and dissected in Gizhiginskaya Bay of the northern part of the Sea of Okhotsk in 2021, of which 8.0 ± 1.4% were infected with F. intermedia metacestodes (I. I. 1-19 specimens). Study results of the infestation of S. balanoides on the Koni-Pyagin coast of the Sea of Okhotsk (according to the collections of 2006-2007) were supplemented and clarified. Description of metacestodes and the taxonomic affiliation of cysticercoids Microsomacanthus spp. are given.

The discovery of Moniliformis saudi (Acanthocephala: Moniliformidae) in the Algerian hedgehog Atelerix algirus in Malta: morphological, molecular, and metal analyses.

The acanthocephalan Moniliformis saudi Amin, Heckmann, Mohammed, Evans, 2016 was originally described from the desert hedgehog, Paraechinus aethiopicus (Ehrenberg) in central Saudi Arabia. The distribution of P. aethiopicus extends to North Africa and west to Mauritania. Moniliformis saudi was recently found in the Algerian hedgehog Atelerix algirus (Lereboullet) in Malta. The distribution of A. algirus is restricted to the North African and east Iberian Mediterranean coast and associated islands. Both host species cohabit and share the same feeding grounds in northern Algeria where common infections appear to take place. The morphology of specimens from both acanthocephalan populations was similar, with minor variations mostly related to the relatively larger Maltese specimens especially the trunk and the male reproductive system. Taxonomic features like the cone-shaped anterior trunk, size and formula of proboscis and hooks, the receptacle, size and shape of eggs, anatomy of the apical proboscis sensory pores, and the stellate body wall giant nuclei were, however, practically identical. SEM and microscope images of specimens of the Maltese population emphasize their qualitative characteristics such as the degree of the extreme spiral muscle development and the development of the posterior nucleated pouches of the proboscis receptacle. Proboscis hooks of specimens from both the Maltese and the Saudi populations had similarly high levels (percent weights) of calcium, moderate levels of phosphorus, and minimal levels of sulfur, magnesium and sodium marking the diagnostic value of the Energy Dispersive x-ray analysis in species recognition. Newly generated partial sequences of the 18S ribosomal RNA and cytochrome C oxidase subunit 1 (Cox1) of the mitochondrial gene were generated from M. saudi from Malta. Moniliformis saudi from Malta, when compared with other available sequences of the same species isolates available in the GenBank database, formed a strongly supported clade with other congeners. The comparison of the molecular profiles of specimens from populations in Malta, Spain, and Saudi Arabia shows no or low genetic variation between them. Ultimately, we provide a morphological and molecular description of a new population of M. saudi from a new host species in a new geographical location, vastly exceeding the originally described ones from Saudi Arabia. A Cox 1 haplotype network inferred with 10 sequences revealed the presence of eight haplotypes, one of which was shared between the populations of Malta and Spain of M. saudi.

Description and molecular data for a new acanthocephalan parasite, Polymorphus circi n. sp. (Polymorphidae) from the Australasian harrier (Circus approximans Peale) in New Zealand.

Species of genus Polymorphus Lühe, 1911 (Polymorphidae) are acanthocephalans found in fish-eating birds and waterfowl. Although found in many parts of the world, including Australia, no records exist from New Zealand. Because of the largely aquatic intermediate host, Polymorphus species are rarely found in terrestrial birds of prey. During a study of the helminths of the Australasian harrier Circus approximans Peale specimens of Polymorphus were recovered that were found to be new to science. Polymorphus circi n. sp. is formally described and genetic sequence data presented. Specimens were distinguished from all other species by a combination of characters, including their proboscis hook arrangement (20-22 rows of 11-13 hooks), as well as absence of sexual dimorphism, trunk size, proboscis shape and egg size. These acanthocephalans were found in birds from areas with the potential to support freshwater, brackish or marine amphipods, but as yet the actual intermediate hosts are unknown.

Morphological and Molecular Characterization of Two New and Two Already Known Species of the Genus Pallisentis (Acanthocephala: Quadrigyridae) from India with an Update in Key to the Species.

To date, 31 species assigned to the genus Pallisentis Van cleave, 1928 have been reported from India. The present study includes morphological and molecular descriptions of two new species of Pallisentis Van Cleave, 1928, namely P. himachalensis and P. longus from the fresh water fishes Channa punctata (Bloch, 1793) and C. marulius (Hamilton, 1822), respectively, procured from Himachal Pradesh and Chandigarh, India. Of total 35 fishes, 17 were found infected with acanthocephalan parasites. The prevalence of infection was 42.85 and 52.38% for C. punctata and C. marulius, respectively. The morphological characters of P. himachalensis n. sp. include proboscis with 4 circles of hooks with 810 hooks per circle, which gradually decline in size. The trunk in male comprises 1516 circles of collar spines and 2737 circles of trunk spines ending above the anterior testis with syncytial cement gland having 2629 nuclei. The trunk in female comprises of 1418 circles of collar spines and 5573 circles of trunk spines present till the anterior end of reproductive system with additional 34 circles at the posterior end. P. longus n. sp. is the longest species reported in the genus and the length of female reach up to 44 mm. The proboscis comprises 4 circles of proboscis hooks with 910 hooks per circle. In males 1316 circles of the collar spines and 2731 circles of trunk spines are present with syncytial cement gland containing 2025 nuclei. The females are much longer with 1516 circles of collar spines and 6469 circles of trunk spines present till the posterior end. The study also reports two already described species: P. gomtii Gupta and Verma, 1980 from C. punctata and P. nandai Sarkar, 1953 from C. marulius. Total 12 sequences for 4 species have been generated based on 18S, 28S and ITS15.8SITS2 molecular markers. The 18S and ITS15.8SITS2 Bayesian inference trees generated in the present study showed distinct identities of all 4 species. Moreover, the Bayesian inference tree generated in the present study based on 18S showed the clustering of Pallisentis species in three different clades compared to the previous studies in which only two clades within the genus were reported. The molecular analysis showed the monophyletic origin of the genus Pallisentis and does not support subgeneric classification within the genus.

Redescription of Illiosentis cetratus Van Cleave, 1945 (Acanthocephala: Illiosentidae) from Menticirrhus undulatus (Girard) in California, with notes on Illiosentis furcatus from Peru.

Illiosentis Van Cleave et Lincicome, 1939 initially included two species: Illiosentis furcatus Van Cleave et Lincicome, 1939 found in the West Atlantic from Cape Cod in Massachusetts, USA to northern Argentina and Illiosentis cetratus Van Cleave, 1945 with restricted distribution in the Pacific coast of southern California. We are reporting I. furcatus from Peru for the first time and describe a population of I. cetratus from the California corbina, Menticirrhus undulatus (Girard), from southern California. The proboscis hook formula was 14 longitudinal rows for I. furcatus of 18-23 hooks each compared to 16 rows of 19-24 hooks each reported by Van Cleave (1945). We complete the inadequate description of I. cetratus with new information on sexual differentiation in the length of the trunk, dorsal vs. ventral hooks, hook roots, trunk spines, two types of anterior recurved rooted hooks vs. posterior rootless straight hooks, measurements of dorsal and ventral hooks and spines, shape of hook roots, terminal position of the female gonopore, and of position of the cephalic ganglion at the anterior margin of the trunk. We also include new details of the reproductive system in both sexes including Saefftigen's pouch and cement gland ducts. We present new SEM and light microscope images. The Energy Dispersive X-ray analysis (EDXA) shows a high level of sulfur in anterior, middle and posterior hooks in various hook sites, as well as spectra of hook tips with a higher relative concentration of sulfur compared to other hook sites. For the placement of I. cetratus, phylogenetic analysis of sequences of three molecular markers, 18S, 28S rRNA and mitochondrial cox 1 genes, was performed with other related available sequences. The resulting analysis illustrated that I. cetratus was nested within a separate clade along with species of two genera, Dentitruncus truttae Sinzar, 1955 and Neotegorhynchus cyprini Lisitsyna, Xi, Orosová, Barčák et Oros, 2022 represented our species of Illiosentis separate from species of Tegorhynchus Van Cleave, 1921 (as also according to the morphology) with which the Illiosentis species were previously synonymised.

Semibalanus balanoides (L.) and Balanus crenatus Bruguière (Balanidae) are intermediate hosts of fimbriarioides intermedia (fuhrmann, 1913) and two species of the genus Microsomacanthus (Cestoda, Hymenolepididae), parasites of sea ducks from the atlantic sector of the Arctic and Northern Pacific

Metacestode infestation of Semibalanus balanoides and Balanus crenatus, collected in the Barents and White Seas and in the northern part of the Sea of Okhotsk in 2020 and 2021, correspondingly, has been studied. 313 S. balanoides from Mogilnaya Bay of Kildin Island (Barents Sea) and isolated mature wrinkled barnacles B. crenatus, 2 and 4 specimens from the Pechora Sea and Kandalaksha Bay of the White Sea, respectively, were examined in 2020. Metacestodes Fimbriarioides intermedia (Fuhrmann, 1913) (Cyclophyllidea, Hymenolepididae) were found in 1.0 ± 0.6% of S. balanoides in the Barents Sea with an invasion intensity (I I) of 2-5 specimens, and in one of two B. crenatus from the Pechora Sea (I I = 15). For the first time in both B. crenatus from the Pechora Sea, taken from the valves of the mussel Mytilus edulis, metacestodes Microsomacanthus sp. I (I I = 13 and 20) with proboscis hooks 38-41 (39.4 ± 0.1) µm long, blades of 9.5-11 (10.7 ± 0.1) µm were obtained. One of four B. crenatus from the Kandalaksha Bay was infected with another Microsomacanthus sp. II (I I = 19) with proboscis hooks 44.0-49.5 (45.7 ± 0.5) µm long and blades - 14.0-16.0 (14.8 ± 0.07) µm. 362 S. balanoides were collected and dissected in Gizhiginskaya Bay of the northern part of the Sea of Okhotsk in 2021, of which 8.0 ± 1.4% were infected with F. intermedia metacestodes (I I = 1-19). Study results of the infestation of S. balanoides on the Koni-Pyagin coast of the Sea of Okhotsk (according to the collections of 2006-2007) were supplemented and clarified. Description of metacestodes and the taxonomic affiliation of cysticercoids Microsomacanthus spp. are given.

The elevation of a unique population of Corynosoma strumosum (Acanthocephala: Polymorphidae) from the Caspian seal, Pusa caspica, in the Caspian Sea to Corynosoma neostrumosum n. sp.

An isolated population of 700 specimens initially described as Corynosoma strumosum (Rudolphi, 1802) Lühe, 1904 and currently reassigned to Corynosoma neostrumosum n. sp. was collected from one young male Caspian seal, Pusa caspica (Gmelin) in the southern land-locked Caspian Sea in April 2009. Collected worms were morphologically unique compared with those reported by other observers in open waters, especially in shape and distribution of proboscis hooks and trunk spines, dorso-ventral differences in proboscis hooks and their organization, the baldness of anterior proboscis, consistently smaller size of trunk and testes, larger eggs, the rough egg topography, epidermal micropores, and variations in the female gonopore. Molecular data from the internal transcribed spacer region of rDNA and the mitochondrial cox1 gene was also provided to supplement the morphological study of the new species.

Review of the concept of Profilicollis Meyer, 1931 with a description of Profilicollis rancoensis n. sp. (Acanthocephala: Polymorphidae) from the freshwater crab, Aegla abtao Schmitt, 1942 (Decapoda: Anomura) in Chile, with a key to congeneric species.

Profilicollis rancoensis n. sp. is the tenth species of Profilicollis Meyer, 1931 which includes 9 other species mostly known from marine decapod crabs and shore birds. Cystacanths of P. rancoensis are described from the dominant freshwater crab Aegla abtao in Ranco Lake, Chile and are morphologically distinguished from cystacanths of the 9 other species based on a combination of 4 characters. These are body size, number of proboscis hook rows, number of hooks per row, and length of the largest anterior 2-4 hooks. Male and female cystacanths of P. rancoensis are 2.10-3.33 mm long having an ovoid proboscis with 14 rows of 6-7 hooks per row, with the largest anterior 2-4 hooks being 105-110 micrometers long; the anterior trunk has many small spines in 70-80 concentric rings, each with 50-60 spines around them; hook roots are simple, directed posteriorly, about as long as the blades anteriorly with unremarkable anterior manubria; the cephalic ganglion are in mid-receptacle just anterior to the level of the anterior trunk; the lemnisci are long and slender; the testes are in the anterior trunk, posterior trunk, or one in each; the primordia of 2 tubular cement glands are evident; strong bundles of fibers link the anterior and posterior trunk; and the posterior trunk has a corrugated surface cuticula. Molecular analysis (COI and 18S) sequences coincided with the morphology and support its taxonomy. The phylogenetic profile revealed that P. rancoensis n. sp. fell into the Profilicollis clade. Both sequences showed low genetic variation, and three different haplotypes were found. The new species was more closely related to P. botulus (Van Cleave, 1916) Witenberg, 1932 than to other Profilicollis species.

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

Specimens of Neoechinorhynchus (Neoechinorhynchus) poonchensis sp. n. are described from Schizothorax richardsonii (Gray) in the Poonch River, Jammu and Kashmir. Specimens are thick-walled with dissimilar dorsal and ventral para-receptacle structures, anteriorly manubriated hooks, two giant nuclei in each lemniscus and many subcutaneousy. The lemnisci barely overlap the larger anterior testis, the cement gland has eight giant nuclei, and the seminal vesicle is large with thin walls. The vagina is unremarkable but the long uterus is made up of four specialised regions. Neoechinorhynchus rigidus (Van Cleave, 1928), resembles N. poonchensis sp. n. It is distinguished from N. poonchensis sp. n. by having smaller trunk, proboscis, and male reproductive structures, equal testes, unequal lemnisci with three giant nuclei each, and much larger anterior proboscis hook (130 μm in males) than that originally described by Van Cleave (1928) (70 μm in a female). Anterior hook length alone is sufficient to conclude that the N. rigidus of Datta (1937) is not the same species as the N. rigidus of Van Cleave (1928). Van Cleave's (1928) species remains valid and that of Datta (1937) is considered a different species named Neoechinorhynchus pseudorigidus sp. n., herein. Micropores of N. poonchensis sp. n. have variable distribution in different trunk regions and the Energy Dispersive X-ray analysis demonstrated higher levels of sulfur and lower levels of calcium and phosphorus. Sequences of the 18S rDNA gene from nuclear DNA, and cytochrome c oxidase subunit I (cox1) from mitochondrial DNA of N. poonchensis sp. n. were amplified and aligned with other sequences available on GenBank. Maximum likelihood (ML) and Bayesian inference (BI) analyses inferred for 18S rDNA and cox1 showed that N. poonchensis sp. n. was nested in a separate clade.

A comparative assessment of the morphology of Profilicollis altmani (Acanthocephala, Polymorphidae) from crustaceans and shore birds in Peru, with special notes on hook elemental analysis (EDXA), SEM imaging, histopathology, and molecular profile.

The morphology of cystacanths and adults of Profilicollis altmani (Perry, 1942) Van Cleave, 1947 (Polymorphidae) were studied from the Pacific mole crab Emerita analoga (Stimpson) (Crustacea, Hippidae) and Belcher’s gull Larus belcheri (Vigors) (Aves, Laridae), respectively, in Peru. Comparative morphometrics with accounts of other populations of P. altmani from elsewhere off the Pacific and Atlantic coasts of North and South America revealed marked intraspecific population variations. We report scanning electron micrographs (SEM) of new features, not before noted or captured in line drawings by earlier observers. We further present microscope images that reveal internal details not previously reported or possible to see with SEM. Energy dispersive X-ray analysis (EDXA) revealed unusual patterns in the chemistry of proboscis hooks especially the high sulfur and diminished phosphorous and calcium in hook tips and low sulfur and high levels of phosphorous and calcium at mid hooks. The size and shape of all hooks of the cystacanths are reported for the first time. Histopathological studies in L. belcheri from Peru are also included. Cystacanths of P. altmani from California were also analyzed for molecular patterns and compared with other sequences reported from other locations. The molecular data and the analysis of our new sequences of cytochrome oxidase I (COI) showed that haplotypes of P. altmani had low genetic variation; the species is not geographically structured, and within its clade no monophyletic group is formed.

Three new species of Neoechinorhynchus (Acanthocephala: Neoechinorhynchidae) from fresh-water fish collected from Tigris River, Iraq.

Three new species of Neoechinorhynchus are described from freshwater fish of Tigris River, at Salah Al-Din province, mid Iraq, namely Neoechinorhynchus tigrisensis n. sp. from Shilik Leuciscus vorax (Heckel) and Brond-snout Chondrostoma regium (Heckel), N. planilizai n. sp. from Abu mullet Planiliza abu (Heckel) and Tigris catfish Silurus triostegus (Heckel) and N. barbi n. sp. from Mesopotamian barb Capoeta damascina (Valenciennes). The first two new species shared the para-receptacle structure (PRS) with seven nominal valid species of the genus Neoechinorhynchus but they differed in other taxonomic traits, while the third new species shared the vaginal vestibular muscles (para vaginal patch) at the end of female trunk with N. spiramuscularis Amin, Heckmann & Ha, 2014 and N. zabensis Amin, Abdullah & Mhaisen, 2003 but differed for further morphological features. Proboscis hooks of middle and posterior circles in N. barbi n. sp. are remarkably bigger than in the other two new species (N. tigrisensis and N. planilizai) while the hooks in first circle is almost similar in the three species. Furthermore, N. tigrisensis n. sp. and N. planilizai n. sp. differ from some marine species by having smallest hooks size at anterior circle, with different shape and size of hooks. The three new species reported in the present study are compared with other eight species of Neoechinorhynchus reported so far from fish in Iraq. This work contributes to increase the knowledge on the biodiversity of fish parasites all over the world, especially for acanthocephalans.

Three new species of Acanthocephala from Acanthogyrus (Acanthosentis) (Acanthocephala: Quadrigyridae) from tinfoil barb fish, Barbonymus schwanenfeldii in Lake Kenyir, Terengganu, Malaysia.

This study was carried out in order to identify acanthocephalan species complexes, based on morphological variability, infecting Barbonymus schwanenfeldii from Lake Kenyir, Terengganu, Malaysia. Acanthocephala were fixed in ethanol, stained with aceto-carmine and studied morphologically by using a light microscope. Variation in morphological traits such as proboscis, proboscis receptacle, egg, testes shape and location, number of hooks and cement gland has been traditionally used to diagnose the acanthocephalans species but the delimitations between closely related species are still confusing and are always questionable among taxonomists. Molecular analysis was used for support the identification. Morphological variability prospecting reveals the presence of three different new species complexes from the subgenus Acanthosentis by referring published taxonomic keys. These new species may be distinguished from the other 46 described species of Acanthosentis by having six unique structures: the presence of an anterior parareceptacle structure (PRS); vaginal sleeve structure; a paired lateral, cone-shaped, muscular jacket surrounding the vagina; alternating pattern and size of proboscis hooks, variation in proboscis size and shape; the presence of the circular collar ring around the neck between the proboscis and trunk and lastly the presence of a muscular-like structure attached to the collar ring on the proboscis. These acanthocephalans found in the intestine of B. schwanenfeldii in Kenyir Lake Malaysia represent new species, named Acanthogyrus ( Acanthosentis) kenyirensis n.sp., A. ( A.) terengganuensis n.sp. and A. ( A.) tembatensis n. sp.

MORPHOLOGY OF ADULTS AND IMMATURES OF THE ACANTHOCEPHALAN, POMPHORHYNCHUS FUHAIENSIS YUE, 1998 (ACANTHOCEPHALA: POMPHORHYNCHIDAE) FROM CYPRINID FISH IN NORTHWEST CHINA.

Adult specimens of Pomphorhynchus fuhaiensis were identified from common carp (Cyprinus carpio L.) in Ulungur Lake of northwest China, and acanthors, acanthellae, cystacanths dissected from Gammarus lacustris in a small tributary of Ulungur River for the first time. The acanthocephalans were also found in crucian carp (Carassius carassius L.), tench (Tinca tinca L.), oriental bream (Abramis brama orientalis Berg), and ide (Leuciscus idus L.) in the lake. This species is distinguished from other species in Pomphorhynchus by its large, spherical bulb and very long neck as well as by a cylindrical proboscis armed with 15-17 longitudinal rows of 9-12 hooks each. The anterior proboscis hooks are almost uniform in size and shape, the sixth hook in a short row and the seventh hook in long row decrease abruptly in size posteriorly with the last end hook being a little larger than the prebasal hook, and in a ring; posterior proboscis hooks much more widely spaced. Furthermore, the lemnisci are claviform. The mean neck:trunk ratio is about 0.5, which is larger than most other species in Pomphorhynchus. Females are larger than males. In males, the testes are in one-third to one-half of the trunk, equal, ovoid-spheroid, usually contiguous, and small relative to the body size, and there are 6 ovoid cement glands. Pomphorhynchus fuhaiensis is similar to Pomphorhynchus laevis but can be distinguished by the number of longitudinal rows of hooks. Pomphorhynchus laevis is armed with 18-20 longitudinal rows of 11-13 hooks, P. fuhaiensis is armed with 15-17 longitudinal rows of 9-12 hooks.

Redescription and molecular analysis of Pallisentis (Pallisentis) nandai Sarkar, 1953 (Acanthocephala: Quadrigyridae) in India.

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.

New perspectives on Aspersentis Megarhynchus (Acanthocephala: Heteracanthocephalidae) from Notothenia Coriiceps Richardson (Nototheniidae) in the West Antarctic, with emended generic diagnosis.

A number of variable descriptive accounts of Aspersentis megarhynchus (von Linstow, 1892) Golvan, 1960 have been reported from specimens collected from many species of fish in various locations off Antarctic islands. We have described a new population from Notothenia coriiceps Richardson (Nototheniidae) off Galindez Island, West Antarctica, and features not previously reported, resolved the taxonomic controversies and nomenclature, and emended and updated the generic diagnosis taking into account the newly observed structures. These are depicted in microscopic images and include the outer spiral wall of the proboscis receptacle, the thicker dorsal wall of the receptacle compared to the ventral wall, parts of the female reproductive system, the separate cement gland ducts, the dorsal position of the male gonopore and more detail of proboscis hooks and trunk spines. It is surprising that the newly observed features were missed from the many descriptions of A. megarhynchus created since the original description. The variability in A. megarhynchus is noted with a comparison of the morphometrics of our specimens vs. those in six other descriptions. We also analysed the metal composition of hooks and spines using energy-dispersive X-ray analysis and concluded a molecular characterization of the species based on 18S DNA gene, with related phylogenetic analyses.

Corynosoma australe and Bolbosoma vasculosum (Polymorphidae: Acanthocephala) from Arctocephalus pusillus pusillus (Otariidae) and Argyrosomus spp. (Sciaenidae) from the Namibian Coast of Africa

Five Cape fur seals, Arctocephalus pusillus pusillus, 1 dusky kob, Argyrosomus coronus, and 55 silver kob, A. inodorus, collected from Cape Cross, Henties Bay, and Skeleton Coast Park, Namibia, were examined for acanthocephalans. Adults of Bolbosoma vasculosum and Corynosoma australe were recovered from 5 Cape fur seals, and cystacanths of C. australe from the single dusky kob and 3 of the silver kobs that were examined. This is the first record of B. vasculosum and the second of C. australe from the Namibian coast. Scanning electron microscopy of specimens of C. australe revealed features such as bursal papillae and micropores both on the proboscis hook surfaces and across the epidermal surface of the trunk. X-ray analyses of gallium cut hook, egg, and spines of C. australe are presented with analyses of spines of Corynosoma strumosum for comparison.

Application of DNA barcoding and morphometric analysis in differentiating cystacanths of Polymorphus species (Acanthocephala: Polymorphidae) from central Alberta, Canada.

Acanthocephalans are multi-host endoparasites, many of which use freshwater amphipods as intermediate hosts for their larval stages (e.g., cystacanths) while adults live in the intestines of vertebrates, including waterfowl. In central Alberta, Canada, several co-occurring species of the acanthocephalan genus Polymorphus use the amphipod Gammarus lacustris Sars, 1863 as an intermediate host. We applied DNA barcoding and morphometric analysis to differentiate cystacanth larvae from G. lacustris sampled from 17 Albertan water bodies. We slide-mounted specimens and measured morphological traits relating to proboscis hooks. We sequenced the standard DNA barcoding region of the mitochondrial cytochrome c oxidase subunit I gene (COI). Morphometric analysis suggested that the acanthocephalans we collected belonged to four morphologically different groups that keyed to Polymorphus contortus (Bremser, 1821) Travassos, 1926; P. marilis Van Cleave, 1939; P. paradoxus Connel et Corner, 1957; and P. strumosoides (Lundström, 1942) Amin, 2013. Our Bayesian tree based on COI sequences generally corroborated the morphological results and supported that the specimens assigned to P. cf. contortus and P. cf. strumosoides belong to two distinct species. In contrast, the Bayesian tree showed that specimens of P. cf. marilis were nested as a cluster within the P. cf. paradoxus clade. Similarly, small pairwise genetic distance (< 2%) between specimens identified as P. cf. contortus and P. cf. strumosoides suggests that they are conspecific. Future studies should use morphology and sequence data from adult acanthocephalans to assess the taxonomic identity of the cystacanth-based Polymorphus taxa. Our study is the first to provide genetic information for the four Polymorphus taxa and emphasizes the importance of applying multiple approaches to differentiate parasite species.

The Molecular Profile of Rhadinorhynchus dorsoventrospinosus Amin, Heckmann, and Ha 2011 (Acanthocephala: Rhadinorhynchidae) from Vietnam.

Of the 46 known species of Rhadinorhynchus Lühe, 1911, only 6 species, including Rhadinorhynchus dorsoventrospinosus Amin, Heckmann, and Ha, 2011, have dorsal and ventral, as well as lateral, trunk spines in the posterior field of trunk spines. The other 5 species are Rhadinorhynchus erumei Gupta and Fatima, 1981, Rhadinorhynchus adenati (Golvan and Houin, 1964) Golvan, 1969, Rhadinorhynchus lintoni Cable and Linderoth, 1963, Rhadinorhynchus pacificus Amin, Rubtsova, and Ha, 2019, and Rhadinorhynchus multispinosus Amin, Rubtsova, and Ha, 2019. These 5 species are distinguished from R. dorsoventrospinosus by differences in proboscis hook armature, trunk spine organization, and egg size. The distinction of R. dorsoventrospinosus is further demonstrated by its molecular description. We amplified the 18S and ITS1+5.8S+ITS2 rDNA region and cytochrome c oxidase subunit 1 (COI) gene for this study. Unfortunately, no ITS1+5.8S+ITS2 gene sequences are available for comparison with other species of the genus Rhadinorhynchus. Therefore, phylogenetic trees generated from sequences of the 18S nuclear region and COI gene were analyzed for the phylogenetic position of isolates of R. dorsoventrospinosus. Rhadinorhynchus dorsoventrospinosus has been validated as a species based on comparisons of morphological (original description) and molecular features (this paper). The additional genetic data will be useful as more species are described and as more genetic material becomes available to improve taxon sampling in the genetic analysis.

Special Description of Pallisentis (Brevitritospinus) allahabadii Agarwal 1958 (Acanthocephala: Quadrigyridae) from Channa punctata (Bloch, 1793) by Scanning Electron Microscope.

The aim of this study was to investigate the morphological features of acanthocephalans isolated from Channa punctata (Bloch, 1793). Fishes collected alive from fish farms in Nadia District of West Bengal (India) were dissected for collection of acanthocephalans. Parasites isolated from intestine were fixed in formalin-aceto-alcohol and finally preserved in 70% ethanol for light microscopic studies and in 2.5% glutaraldehyde for scanning electron microscopy. The morphological characteristics of adult acanthocephalans were found to be similar to the original descriptions describing the basic characters of proboscis hooks, the spines of the collar and trunk region, and cement gland nuclei. New taxonomic characters were identified for the first time by scanning electron microscopy. The acanthocephalan Pallisentis (Brevitritospinus) allahabadii Agarwal 1958 was described as an important parasite infecting fishes. The prevalence of the parasite was 23% and its adult stage was observed.

Morphological and Molecular Description of Rhadinorhynchus hiansi Soota and Bhattacharya, 1981 (Acanthocephala: Rhadinorhynchidae) from Marine Fish off the Pacific Coast of Vietnam

Rhadinorhynchus hiansi Soota and Bhattacharya, 1981 , has remained unknown since its original incomplete description from 2 male specimens collected from the flat needlefish Ablennes hians Valenciennes (Belonidae) off Trivandrum, Kerala, India. Recent collections of fishes along the Pacific coast of Vietnam in 2016 and 2017 produced many specimens of the same species from the striped bonito Sarda orientalis Temminck and Schlegel (Scombridae) off the southern Pacific coast of Vietnam at Nha Trang. We describe females for the first time, assign a female allotype status, and provide an expanded description of males from a larger collection completing missing information on hooks and hook roots, receptacle, lemnisci, cement glands, Saefftigen's pouch, and trunk spines. Specimens of R. hiansi characteristically have no dorsal spines in the posterior field of trunk spines and a long proboscis with 36-48 dorso-ventrally differentiated proboscis hooks per row becoming progressively smaller posteriorly then increasing in size near the posterior end to a maximum at the posterior-most ring. Trunk, testes, and lemnisci in our specimens were considerably larger than those reported in the original description, but the proboscis was relatively smaller. The females had long reproductive system and corrugated elliptic eggs without polar prolongation of fertilization membrane. Energy Dispersive X-ray Analysis (EDXA) demonstrates high levels of calcium and phosphorus in large gallium cut hooks and high levels of sulfur in tip cuts of large and small hooks and in spines. This EDXA pattern is a characteristic fingerprint of R. hiansi. The molecular profile of R. hiansi is described from 18S rDNA and COI genes, and phylogenetic relationships with most closely related species are discussed.