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The study describes a new species of Pallisentis Van Cleave, 1928 infecting the freshwater cat fish Wallago attu Bloch and Schneider, 1801 from Ropar wetland, Punjab, India. The morphological characters of Pallisentis roparensis include proboscis with 4 circles of 10 hooks each gradually declining in size, first circle of hooks, Graphical abstract Image 1, Highlights • Description of Pallisentis roparensis n. sp. from a freshwater cat fish Wallago attu from Ropar wetland, Punjab, India. • Phylogenetic analyses show well nested sequences of new species within the genus and monophyly of the genus Pallisentis. • Molecular data does not show any trend towards the sub-generic classification based on morphology within the genus. • Histopathological study of infected host intestine shows mechanical damage and inflammatory immune response..

Till date 34 species of Pallisentis have been validated with almost negligible studies on its molecular phylogeny. The discovered species of the genus Pallisentis are confined only to the Asian continent. Many different species of Acanthocephala infecting commercially important freshwater as well as the marine fishes have been recorded from India mainly on the basis of morphology. The original record of morphological characteristics of Pallisentis nagpurensis (Bhalerao 1931) Baylis, 1933 can be traced back to the Bhalerao, 1931 from Channa striata (Ophiocephalus striatus) from the state of Uttar Pradesh, India without the separate documentation of male and female characteristics. Same species has also been reported to infect Channa striata from different parts of India as well as from the Indonesia and Ceylon (Baylis, 1933 and Fernando and Furtado, 1963). The present study compiles the morphological characteristics of male and female P. nagpurensis along with the comparison with similar species from same geographical region. This study also reports the first record of 18S, 28S rRNA and ITS1-5.8S-ITS2 gene sequences of P. nagpurensis generated for analyzing the phylogeny within this taxonomic group. P. nagpurensis together with the other species of Pallisentis reported from India distinctly formed a sub-clade separating it from the other members of same genus.

The purpose of the present study was to provide molecular support for the validity of the morphological description of Acanthosentis kashmirensis Amin, Heckmann, Zargar, 2017 which was originally poorly described as Neoechinorhynchus kashmirensis Fotedar and Dar, 1977 from the Indian subcontinent, and to characterise its molecular identity and phylogenetic relationships. Total DNA was extracted, and the partial region of the small subunit (SSU) 18S rDNA and ITS-rDNA genes were amplified and sequenced. Genetic diversity was calculated and phylogenetic analysis of the nucleotide sequence data was performed. In this study, the molecular profile of this acanthocephalan was generated for the first time. Based on the partial 18S rDNA, interspecific variation between A. kashmirensis with different species of Acanthosentis and were 3.6–10.3% and 22.4–38.2% based on 18S rDNA and ITS-rDNA genes, respectively. We described the phylogenetic relationships of A. kashmirensis compared with other species of the genus and also with members of the family Quadrigyridae. The ITS-rDNA sequences of members of the family Quadrigyridae are more variable than 18S rDNA that can be useful for achieving a proper assessment of biodiversity. Sequence data generation from additional species of Acanthosentis will be needed to reconstruct the phylogenetic relationships of this group of acanthocephalans.

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.

In order to study the host-parasite interaction of native fish Middle Parana system, Santa Fe, Argentina, the digestive tracts of 64 specimens of Hoplias malabaricus (Pisces, Erythrinidae) and of 70 specimens of Pimelodus maculatus (Pisces, Pimelodidae) were analyzed. These native species are important for the economy and recreational activities of the region. The fish were collected from two lentic environments associated with the San Javier River, Cayasta, in the province of Santa Fe, Argentina. After dissecting the digestive tracts, parasites were detected by stereoscopic microscopy, collected and preserved in alcohol at 70% for subsequent taxonomic identification and description. In the intestines of both hosts, sixty-nine specimens of Quadrigyrus machadoi (Acanthocephala, Quadrigyridae) were reported for the first time in the Middle Parana System in this province. The parasitic prevalence was determined for each case (P= 20.31 %, H. malabaricus; P= 28.6 %, P. maculatus) and an extended description of the icthyoparasite was carried out. This work broadens the geographical distribution of Q. machadoi for both hosts and contributes to the advancement of knowledge on the icthyoparasites associated with the regional icthyc fauna.

Pallisentis(Pallisentis)nandaiSarkar, 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 asP. nandaibut 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 genusPallisentisVan 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 ofPallisentis,P. İndicaMital & Lal, 1976, were considerably different. The phylogenetic position ofP. nandaiwithin 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 placedP. nandaiin a clade with otherPallisentisspecies under the family Quadrigyridae. This is the first report based on molecular evidence forP. nandai.

One new species of Pallisentis Van Cleave, 1928 is described from Channa punctatus (Bloch) from Gomti River (tributary of the Ganga River), in Uttar Pradesh, Lucknow district, India. Pallisentis thapari n. sp. is characterized morphologically by individuals having a globular proboscis armed with rooted hooks in 4 circles of 8–10 hooks each, the first circle more than 100 long and hooks gradually declining in size posteriorly. The trunk is cylindrical, with collar spines comprised of 15–17 complete circles of spines, each ring with 12–22 spines. As common in members of the genus, a narrow spine-free zone lies in between the rings of collar and trunk spines. Field of spines extends posteriorly to half of the body length, ending above the level of testes in males and slightly past mid-body in females; trunk spines have an optically-dense Y-shaped core. The trunk is only slightly wider at the anterior end. The syncytial cement gland of males contained 23–30 nuclei. Individuals of Channa striatus Bloch from the same locality also were infected with the new species. A second species of Acanthocephala, Acanthosentis seenghalae Chowhan, Gupta, Khera, 1988, was found as a parasite of Puntius sophore (Hamilton) from the same locality. The proboscis is short, globular, with 3 circles of hooks each circle bearing 6 hooks. The trunk is broad in the middle and tapered at both ends, with the posterior end narrower than the anterior end. Twelve to 16 circles of spines, each with 21–40 spines, extend from anterior end to just past mid-body in males and only to mid-body in females. The syncytial cement gland of males contains 6–10 nuclei. The analysis of 18s rDNA identified two clades of a monophyletic Pallisentis and placed the isolate of P. thapari n. sp. within that clade; previously established subgenera were not supported by the results of the analysis.

Pallisentis thapari n. sp. (Figs. 1–8 and 15–18) urn:lsid:zoobank.org:act: 294DD60F- 1233-47 D0-A85E-CDC3B24FABC1 Type host: Spotted snakehead Channa punctatus (Bloch, 1793) (Perciformes, Channidae). Type locality: Nabi Panah Pond, Malihabad, Lucknow, Uttar Pradesh, India (26.5830° N, 80.4322° E). Additional host: Channa striatus (Bloch, 1793) (Perciformes, Channidae). Site of infection: Intestine. Specimens deposited: Holotype deposited in Gangetic Plane Regional Centre, Zoological Survey of India (ZSI), Patna, India- male ZSI / GPRC, IV–4356a and allotype female ZSI / GPRC, IV–4356 b. Paratypes deposited at the Helminthology Laboratory, Department of Zoology, University of Lucknow, U.P., India- males LU /Z/2019/1– LU /Z/2019/07 and females LU /Z/2019/08– LU /Z/2019/014. Zoobank Registration: The Life Science Identifier (LSID) urn:lsid:zoobank.org:pub: 53DFA57F-4D6A-49DE- 8664-0C8B080C58E8 Etymology: The new species is named in honor of the late Dr. Gobind Singh Thapar, Department of Zoology, University of Lucknow, Lucknow, India, for his outstanding contributions in Helminthology. Diagnosis: Quadrigyridae, Pallisentinae, with characters of the genus Pallisentis as diagnosed by Amin et al. (2000). Worms cylindrical, relatively large sized, range of length of males and females overlapping but mean length of males slightly longer than females. Trunk with Y-shaped spines in rings, with anterior set of 14–17 closely spaced rings of collar spines and posterior set of 14–41 more widely spaced rings of trunk spines; posterior set reaching posteriorly only to mid body. Anterior and posterior sets of trunk spines separated by a narrow region lacking spines. Trunk spines conical with an optically-dense Y-shaped core. Proboscis short, broadly ovoid, wider anteriorly, with 4 circles of 8–10 hooks each, hooks decreasing in size posteriorly. Proboscis receptacle single-walled, with cerebral ganglion located at base. Lemnisci cylindrical, much longer than the receptacle, posterior ends hanging loose in body cavity, about equal in length. In males, testes dollioform-depressed in shape (width to length ratio 1.0:3.3), contiguous and slightly overlapping. Cement gland oblong-very depressed in shape, width to length ratio 1:6, syncytial, about as long as testicular field, containing 23–30 giant nuclei. Cement reservoir and Saefftigen’s pouch present. Parasites of freshwater fishes in India. Description: Material examined: seven male and seven female specimens, and two specimens for SEM. Male. Worms relatively large in size (Fig. 1). Trunk 4.9–8.0 (6.6) mm long, 420–560 (484) µm a widest point. Anterior part of trunk (about 1/2) (Fig. 1) covered with 29–58 rings of tegmental spines, pointing posteriorly (Figs. 1 and 16), number of spines per ring declining in numbers from anterior to posterior. Circles of spines separated into two fields, anterior set composed of 15–17 closely spaced rings, each ring consisting of 12–22 spines, called collar spines, and posterior set of 21–41 more widely spaced rings of trunk spines, each anteriormost ring composed of 12–16 spines (Figs. 16 and 17). Area covered by collar spines 340–800 (457) long. Anterior and posterior groups of spines separated by narrow spine-free zone 100–180 (139) in length. Circles of trunk spines reaching posteriorly only to mid-body, ending anterior to testicular field. Individual spines 40–50 (47) long, 20–40 (30) wide at the base. Proboscis globular, broadly ovoid in shape, wider anteriorly and narrowing posteriorly, 230–280 (243) long, 220–260 (241.4) wide anteriorly (Figs. 1, 3 and 15). Proboscis with rooted hooks in 4 circles of 8–10 hooks each (Fig. 3). Hooks longest in first circle, decreasing in size posteriorly in succeeding rings (Figs. 3, 4 and 15). Blades of hooks in anterior circles relatively straight and oriented laterally because of position of insertion point or root; blades increasingly curved posteriorly. Length of hooks from anterior to posterior, 100–130 (112), 80–110 (96), 40–70 (52), 30–50 (34); size ratios anterior to posterior 1.0:0.9:0.5:0.3. Neck short, robust, 150–290 (199) long, 160–290 (213) wide posteriorly. Proboscis receptacle 340–890 (547) long by 130–220 (161) wide. Lemnisci paired, cylindroid, much longer than the receptacle and almost equal sized; right lemniscus 730–2450 (1560) long, 40–60 (52) wide posteriorly, left lemniscus 1200–2450 (1625) long, 40–60 (52) wide. Reproductive system in posterior half of trunk. Testes dollioform-depressed in shape, contiguous with slight overlap. Anterior testis 440–720 (521) long, 140–210 (161) wide; posterior testis 440–730 (53) long, 140–220 (167) wide. Cement gland contiguous with testes, about size of testicular field, 680–1550 (1061) long by 130–240 (180) wide, containing 23–30 nuclei. Cement reservoir contiguous with cement gland, branching posteriorly into two ducts, 550–1070 (824) long, 140–230 (184) wide. Saefftigen’s pouch obdeltoid/very narrowly spatulate in shape, 160–340 (272) long, 130–200 (17) wide anteriorly. Seminal vesicle 400–800 (596) long, 70–140 (104) wide. Gonopore terminal (Figs. 1 and 2). Bursa, when extended (Figs. 1, 2 and 18), 200–300 (183) long and 100–240 (164) wide. Female. Worms slightly smaller in size than males (Fig. 6). Trunk 4.0–7.7 (6.3) mm long, 490–590 µm (503) µm at widest point.Anterior part of trunk (approximately anterior half) (Fig. 6) covered with 30–41 rings of tegmental spines, pointing posteriorly (Fig. 5), number of spines per ring declining in number from anterior to posterior. Circles of spines separated into two fields, anterior set composed of 14–15 closely spaced rings, called collar spines, each ring composed of 16–26 spines and posterior set of 14–40 more widely spaced rings of trunk spines, each ring made up of 12–24 spines. Length of trunk covered by collar spines 430–570 (530) long. Spine-free zone narrow 100–190 (147) in length. Circles of trunk spines reaching posteriorly only to mid-body, ending anterior to testicular field. Individual spines 40–51 (48) long, 20–40 (31) wide at the base. Proboscis globular, broadly ovoid in shape, wider anteriorly and narrowing posteriorly, 180–260 (213) long, 190–250 (220) wide anteriorly (Fig. 6). Proboscis with rooted hooks in 4 circles of 8–10 hooks each (Fig. 6). Hooks longest in first circle, hooks decreasing in size posteriorly in succeeding rings (Figs. 6). Blades of hooks in anterior circles relatively straight and oriented laterally because of position of insertion point or root; blades increasingly curved posteriorly. Length of hooks of proboscis of paratype female, from anterior to posterior, 140, 120, 70, 40; size ratios anterior to posterior 1.0:0.9:0.5:0.3. Neck short, robust, 170–460 (296) long, 160–240 (197) wide posteriorly. Proboscis receptacle 440–840 (643) long, 80–250 (173) wide. Lemnisci paired, cylindroid, much longer than the receptacle and equal in size, 1,600 –2,600 (2,110 ± 500.0) long, 40–60 (53) wide posteriorly. Reproductive system in posterior end of trunk, uterine bell cylindrical shaped, 240–330 (280) long and 50–110 (78) wide (Fig. 7). Uterus 50–260 (110) long, 30–110 (63) wide. Vagina 30–90 (53.3 ± 20.7) long, 30–50 (38.3 ± 9.8) wide. Ovarian balls present in some females, 40–80 (59) long, 20–60 (41) wide. Eggs 15–20 (18) long, 10–10 wide (Fig. 8) (width to length ratio about 2:3). Gonopore ventro-terminal (Figs. 6 and 7). Remarks: Amin et al. (2000) re-described Pallisentis and provided a more detailed diagnosis for the genus. The new species is placed in Pallisentis because it has an anterior set of closely arranged rings of collar spines (15–17 rings) and a posterior set of more widely spaced rings of trunk spines (14–41) separated from the collar spines by a region lacking spines. Giant hypodermal nuclei are present in the trunk wall, the proboscis is broadly ovoid in shape with rooted hooks in 4 circles of 8–10 hooks in each, and the proboscis receptacle is single-walled with the cerebral ganglion located near the base. The lemnisci are much longer than the receptacle, and the syncytial cement gland is long (about as long as the testicular field) with many giant nuclei. The new species is placed in this genus because it shares these characters. If the subgenera of Pallisentis established by Amin et al. (2000) is accepted, P. thapari n. sp. is similar to species previously assigned to the subgenus P. (Pallisentis) Amin, Heckmann, Ha, Luc, and Doanh, 2000 because the longest hooks are in first circle and the hooks of succeeding circles decrease in size posteriorly (Amin et al. 2000). The new species can be distinguished from all known species of Pallisentis because the trunk spines do not extend to the posterior end of either sex, the proboscis hooks in first circles are more than 100 long, and the average length of the proboscis receptacle is more than 500 long. Pallisentis thapari n. sp. is most similar in form to P. clupei Gupta and Gupta, 1979); the length of the first hook in both is about 100, but P. clupei is reported to have conical trunk spines and the new species has spines with a Yshaped core (Gupta & Gupta 1979). In P. clupei, the number of circles of collar spines (12–13 circles in males and 13–14 in females) is similar bit less than that of the new species (15–17 in males and 14–15 in females), although the number of spines per circle in males of P. clupei overlaps with that of the new species (14–20 spines vs. 12–22, respectively). The number of circles of trunk spines in males in both species overlaps (P. clupei 28–30; P. thapari n. sp. 21–41), but the number of circles of trunk spines in females of P. clupei (61) is greater than for females of the new species (14–40). The number of trunk spines in P. clupei and that of the new species also overlaps (males 8–16; females 10–16 vs. males 12–16; females 12–24, respectively). Additionally, the new species can be distinguished from P. clupei in that the trunk spines of the new species extend only to mid-body but they extend to the posterior end in P. clupei. The number of spines in each circle of trunk spines in P. clupei (8–16 in males and 10–16 in females) is less than in P. thapari n. sp. (12–16 in males and 12–24) in females, although there is some overlap in range. Finally, in males, the size and position of testes and the size of the cement gland are similar in P. clupei (1390–1550 long) and the new species (680–1550 long), but in P. clupei there are 9–16 giant nuclei in the cement gland and that of the new species has 23–30 nuclei. Seven species of Pallisentis have been reported to have spines that are Y-shaped (Amin et al. 2000; Gautam et al. 2019): P. basiri Farooqi, 1958; P. cavasii Gupta and Verma, 1980; P. fasciata Gupta and Verma, 1980; P. guptai Gupta and Fatma, 1986; P. indica Mithal and Lai, 1981; P. mehrai Gupta and Fatma, 1986; P. panadei Rai, 1967; and P. unnaoensis Gautam, Misra, and Saxena, 2019 (Farooqi 1958; Rai 1967; Gupta & Verma 1980; Mithal & Lal 1981; Gupta & Fatma 1986; Gautam et al. 2019). In some species the spines are more flattened and evidence of the Y-shape core can be seen externally (Gautam et al. 2019). In the new species the spines are conical but with the Yshaped core (Figs. 5 and 17). Comparisons among species of Pallisentis are difficult because many of the type specimens are not available and one must rely on descriptions in the literature. However, the new species can be distinguished from the abovementioned species by various features. Pallisentis thapari n. sp. is larger than P. cavasii, P. fasciata, and P. unnaoensis (4.9–8.0 mm vs. 2.1–3.0, 2.9–4.0, and 3.4–4.4, respectively) and the new species has more nuclei in the cement gland (23–30 vs. 6–8, 8–10, and 7–8, respectively), and the proboscis hooks of the first row of the new species are longer (100–130) than those of P. cavasii (50–51), P. fasciata (60–70), and P. panadei (70–50) and they are shorter than those of P. unnaoensis (220). The hooks in the first row of the new species and those of P. basiri are about the same size (approximately 100), but the roots of the hooks of the new species are elongate and those of P. basiri are described as being knob-like (Amin et al. 2000). The cement gland of males of the new species is longer than that of P. guptai (680–1550 vs. 500–580, respectively) and the number of nuclei is greater (28–30 vs. 10–12, respectively). Males of the new species have more nuclei in the cement gland than those of P. indica (23–30 vs. 9–18) (Amin et al. 2017a). The trunk spines of the new species reach posteriorly only to about mid-body but those of P. mehrai reach to the posterior end in both males and females. Finally, in results of the molecular analysis, P. unnaoensis is the sister taxa to the clade comprised of the three specimens of the new species. The new species is similar to P. unnaoensis in the number of rings and spines per ring of collar and trunk spines, but the cement gland is longer in the new species (680–1550 vs. 380–520) and the number of nuclei in the cement gland is greater (23–30 vs. 7–8).

Twenty-one species of acanthocephalans, representative of thirteen genera from ten families of seven orders and three classes, are included in this updated checklist of acanthocephalans in South Africa.Although South Africa appears to have a less diverse acanthocephalan fauna compared to some other countries such as Iran in Asia, or Brazil in South America, this is probably an artefact of fewer parasitological surveys.

Quadrigyrus machadoi Fabio, 1983 Actinopterygii Hoplias malabaricus (Bloch) (Characiformes, Erythrinidae). SI: intestine. SD: adult. L: Santa Fe Province: San Javier River. R: Chemes and Brusa (2013). C: vouchers (MACN-Pa 548���549; MFA-ZI 05���06). Pimelodus maculatus Lac��p��de (Siluriformes, Pimelodidae). SI: intestine. SD: adult. L: Santa Fe Province: San Javier River. R: Chemes and Brusa (2013). C: vouchers (MFA-ZI 07���08)., Published as part of Hern��ndez-Orts, Jes��s S., Kuchta, Roman, Semenas, Liliana, Crespo, Enrique A., Gonz��lez, Ra��l A. & Aznar, Francisco J., 2019, An annotated list of the Acanthocephala from Argentina, pp. 1-64 in Zootaxa 4663 (1) on page 11, DOI: 10.11646/zootaxa.4663.1.1, http://zenodo.org/record/3772372, {"references":["Fabio, S. P. (1983) Sobre alguns Acanthocephala parasitos de Hoplias malabaricus. Arquivos da Universidade Federal Rural do Rio de Janeiro, 6, 173 - 180.","Chemes, S. B. & Brusa, R. G. (2013) Description of Quadrigyrus machadoi (Fabio, 1983) (Acanthocephala, Quadrigyridae) in native fish of wetlands associated with the San Javier River, Santa Fe, Argentina. Neotropical Helminthology, 7 (2), 187 - 194."]}

Acanthogyrus(Acanthosentis)maroccanus(Dollfus, 1951), an insufficiently described quadrigyrid acanthocephalan of cyprinid fishes from Northwest Africa, is redescribed based on recently collected specimens from the Algerian barbLuciobarbus callensis(Valenciennes) in Algeria. Newly observed morphological features forA.(A.)maroccanusinclude the arrangement of proboscis hooks (not in regular circles), the male reproductive structures extending into the copulatory bursa and the presence of a para-receptacle structure and vaginal sleeve. The mechanism of copulation of this acanthocephalan is described based on several copulating pairs. The phylogenetic position ofA.(A.)maroccanuswithin Eoacanthocephala was assessed based on partial 28S rDNA sequences. Maximum likelihood and Bayesian inference analyses placedA.(A.)maroccanusin a clade withPalliolisentis(Demidueterospinus)ophiocephalus(Thapar, 1931), both species included in the Quadrigyridae, the only family within the Gyracanthocephala.

Subfamily Pallisentinae Van Cleave, 1928 Genus Palliolisentis Machado Filho, 1960, Published as part of Hern��ndez-Orts, Jes��s S., Kuchta, Roman, Semenas, Liliana, Crespo, Enrique A., Gonz��lez, Ra��l A. & Aznar, Francisco J., 2019, An annotated list of the Acanthocephala from Argentina, pp. 1-64 in Zootaxa 4663 (1) on page 11, DOI: 10.11646/zootaxa.4663.1.1, http://zenodo.org/record/3772372, {"references":["Machado Filho, D. A. (1960) Um novo genero da familia Quadrigyridae Van Cleave, 1920 (Metacanthocephala, Palaeacanthocephala). Revista Brasileira de Biologia, 20, 79 - 84."]}

Palliolisentis cf. ornatus Machado Filho, 1960 Actinopterygii Triportheus paranensis (G��nther) (Characiformes, Triportheidae). SI: intestine. SD: adult. L: Santa Fe Province: Colastin�� River (31��40���S, 60��46���W). R: Arredondo (2013)., Published as part of Hern��ndez-Orts, Jes��s S., Kuchta, Roman, Semenas, Liliana, Crespo, Enrique A., Gonz��lez, Ra��l A. & Aznar, Francisco J., 2019, An annotated list of the Acanthocephala from Argentina, pp. 1-64 in Zootaxa 4663 (1) on page 11, DOI: 10.11646/zootaxa.4663.1.1, http://zenodo.org/record/3772372, {"references":["Machado Filho, D. A. (1960) Um novo genero da familia Quadrigyridae Van Cleave, 1920 (Metacanthocephala, Palaeacanthocephala). Revista Brasileira de Biologia, 20, 79 - 84.","Arredondo, N. J. (2013) Platyhelminthes (Digenea, Proteocephalidea) y Acanthocephala parasitos de peces teleosteos de la cuenca del Rio Parana: diversidad, especificidad y morfologia. PhD thesis. Universidad de Buenos Aires, Buenos Aires, 267 pp."]}

Quadrigyrus sp. Actinopterygii Hoplerythrinus unitaeniatus (Spix & Agassiz) (Characiformes, Erythrinidae). SI: caeca, intestine. SD: adult. L: Santa Fe Province: Colastin�� River (31��40���S, 60��46���W). R: Arredondo (2013). Hoplias malabaricus (Bloch) (Characiformes, Erythrinidae). SI: caeca, intestine. SD: adult. L: Santa Fe Province: Colastin�� River (31��40���S, 60��46���W). R: Arredondo (2013). Luciopimelodus pati (Valenciennes) (Siluriformes, Pimelodidae). SI: intestine. SD: adult. L: Santa Fe Province: Colastin�� River (31��40���S, 60��46���W); Entre R��os Province: Paran��-Guaz�� River (33��54���S, 58��52���W). R: Arredondo (2013). Megalonema platanum (G��nther) (Siluriformes, Pimelodidae). SI: intestine. SD: adult. L: Santa Fe Province: Colastin�� River (31��40���S, 60��46���W). R: Arredondo (2013). Pimelodus albicans (Valenciennes) (Siluriformes, Pimelodidae). SI: intestine. SD: adult. L: Santa Fe Province: Colastin�� River (31��40���S, 60��46���W). R: Arredondo (2013). Pimelodus maculatus Lacep��de (Siluriformes, Pimelodidae). SI: intestine. SD: adult. L: Santa Fe Province: Colastin�� River (31��40���S, 60��46���W). R: Arredondo (2013). Pseudoplatystoma fasciatum (Linnaeus) (Siluriformes, Pimelodidae). SI: intestine. SD: adult. L: Santa Fe Province: Colastin�� River (31��40���S, 60��46���W). R: Arredondo (2013). Sorubim lima (Bloch & Schneider) (Siluriformes, Pimelodidae). SI: intestine. SD: adult. L: Santa Fe Province: Colastin�� River (31��40���S, 60��46���W). R: Arredondo (2013). Ageneiosus inermis (Linnaeus) (Siluriformes, Auchenipteridae). SI: intestine. SD: adult. L: Santa Fe Province: Colastin�� River (31��40���S, 60��46���W); Entre R��os Province: Paran��-Guaz�� River (33��54���S, 58��52���W). R: Arredondo (2013)., Published as part of Hern��ndez-Orts, Jes��s S., Kuchta, Roman, Semenas, Liliana, Crespo, Enrique A., Gonz��lez, Ra��l A. & Aznar, Francisco J., 2019, An annotated list of the Acanthocephala from Argentina, pp. 1-64 in Zootaxa 4663 (1) on pages 11-12, DOI: 10.11646/zootaxa.4663.1.1, http://zenodo.org/record/3772372, {"references":["Arredondo, N. J. (2013) Platyhelminthes (Digenea, Proteocephalidea) y Acanthocephala parasitos de peces teleosteos de la cuenca del Rio Parana: diversidad, especificidad y morfologia. PhD thesis. Universidad de Buenos Aires, Buenos Aires, 267 pp."]}

A detailed list of acanthocephalans from Argentina was generated based on 205 published records. The list includes 52 named and 35 undetermined species of Acanthocephala infecting 6 species of invertebrate (2 amphipods, 3 decapods and 1 insect) and 155 species of vertebrate (one cartilaginous fish, 95 bony fishes, 10 amphibians, 3 reptiles, 13 birds and 33 mammals) host species in the Argentinean territory. The present list contains information on the invertebrate and vertebrate host(s), site of infection, developmental stage and locality(ies) of the acanthocephalans listed and references. For some species of acanthocephalans, information about repositories of the type material, voucher specimens, and DNA sequences of individual taxa are also presented. Finally, a host-Acanthocephala list is also provided. The data compiled revealed considerable gaps in the knowledge of the diversity, taxonomy, distribution, and life cycles of the acanthocephalans from Argentina. Fil: Hernández-Orts, Jesús S.. Universidad Nacional del Comahue. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni". - Provincia de Río Negro. Ministerio de Agricultura, Ganadería y Pesca. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni". Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet Centro Nacional Patagónico. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni"; Argentina Fil: Kuchta, Roman. Biology Centre Of The Academy Of Sciences Of The Czech Republic. Institute Of Parasitology. Laboratory Of Fish Protistology; República Checa Fil: Semenas, Liliana. Lab de Parasitologã­a-inibioma (conicet); Argentina Fil: Crespo, Enrique Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; Argentina Fil: González, Raul Alberto Candido. Universidad Nacional del Comahue; Argentina Fil: Aznar, Francisco J.. Universidad de Valencia; España

Pallisentis ( Brevitritospinus) indica Mittal and Lal, 1976 was found infecting the spotted snakehead Channa punctatus Bloch and Schneider (Channidae) from Meerut, Uttar Pradesh (U.P.), India. The species was identified on the basis of proboscis hooks, trunk spines, and other structures that separate it from all described species. Molecular analysis based on 18S rDNA placed the P. indica isolates within a clade of Pallisentis spp. but distinct from other representatives of the same genus. This study documents the first molecular characterization of P. indica from India.

The acanthocephalan species Quadrigyrus torquatus Van Cleave, 1920 has been found in different hosts from South America, but recent papers have not focused on its morphology traits. Different species of Astyanax Baird & Girard, 1854 were collected with seine nets between January 2017 and October 2017 in Pintada Island, Lake Guaíba, Porto Alegre city (30º17’11’’S and 51º18’01”W), Rio Grande do Sul State, Brazil. Acanthocephalans found in cysts were processed according to the techniques for the group. Specimens of Q. torquatus were identified based mainly in the morphology of proboscis hooks and trunk spines, and by the measurements made using light microscopy. Supplemental observations on the morphology of Q. torquatus were made for the first time considering the morphology and amount of hooks and spines. The amplitude of intensity of infections was 1 (A. aff. fasciatus) and 1‒3 (A. lacustris) helminths. This difference could be related to the number of hosts examined, the feeding habit of the hosts or related to aspects in the parasite life cycle. This paper is the first report of Q. torquatus in A. aff. fasciatus and A. lacustris from Lake Guaíba, extending the distribution to the southernmost state of Brazil, thus contributing to the knowledge of acanthocephalans in freshwater fishes from South America. Resumo: A espécie de acantocéfalo Quadrigyrus torquatus Van Cleave, 1920, tem sido encontrada em diferentes hospedeiros na América do Sul, contudo os estudos recentes não focam no estudo dos caracteres morfológicos. Diferentes espécies de Astyanax Baird & Girard, 1854 foram coletadas com redes do tipo picaré entre janeiro e outubro de 2017, na Ilha da Pintada, Lago Guaíba, Cidade de Porto Alegre (30º17’11’’S e 51º18’01”W), Estado do Rio Grande do Sul, Brasil. Os acantocéfalos encontrados encistados foram processados de acordo com as técnicas para o grupo. Os espécimes de Q. torquatus foram identificados principalmente pela morfologia dos ganchos da probóscide, espinhos do tronco e, pelas medidas realizadas através de microscopia de luz. Observações suplementares na morfologia de Q. torquatus foram realizadas pela primeira vez, considerando a morfologia e o número de ganchos e espinhos. A amplitude das infecções foi 1 (A. aff. fasciatus) e 1‒3 (A. lacustris) helmintos. Esta diferença pode estar associada com o número de hospedeiros examinados, com os hábitos alimentares dos hospedeiros, ou relacionada com aspectos no ciclo de vida do parasito. Este estudo é o primeiro registro de Q. torquatus em A. aff. fasciatus e A. lacustris do Lago Guaíba, estendendo a distribuição do parasito para o sul do Brasil, contribuindo com o conhecimento dos acantocéfalos parasitos de peixes de água doce na América do Sul.

Four new species of genus Pallisentis (Van Cleave, in Records Indian Mus 30:147–149, 1928) are described from the state of Uttar Pradesh, India, infecting freshwater fish. The detailed morphology of all four species was studied using light and scanning electron microscopy. They are: Pallisentis lucknowensis n. sp. from Channa punctatus (Bloch 1785); Pallisentis amini n. sp. from Channa striatus (Bloch 1785); Pallisentis meyeri n. sp. from Channa punctatus (Bloch 1785); and Pallisentis unnaoensis n. sp. from Glossogobius giuris (Hamilton 1822). All four Pallisentis spp. differed from other congeners because of the morphology of the proboscis hooks, size and shape of proboscis hooks, shapes, number and arrangement of trunk spine, size of cement gland, numbers of cement gland nuclei, lemnisci, size and position of testes, gonopore, etc. An updated key of genus Pallisentis of 33 species accepted as valid are provided. The present study extends the number of Pallisentis from 29 to 33 species.

The third part of the catalogue of type material in the Helminthological Collection of the Oswaldo Cruz Institute/FIOCRUZ (CHIOC), comprising types deposited between 1979 and 2016, is presented to complement the first list of all types that was published in 1979. This part encompasses Acanthocephala, Nematoda and the other non-helminth phyla Cnidaria, Annelida, and Arthropoda. Platyhelminthes was covered in the first (Monogenoidea) and second (Rhabditophora Trematoda and Cestoda) parts of the catalogue published in September 2016 and March 2017, respectively. The present catalogue comprises type material for 116 species distributed across five phyla, nine classes, 50 families, and 80 genera. Specific names are listed systematically, followed by type host, infection site, type locality, and specimens with their collection numbers and references. Species classification and nomenclature are updated.

Pallisentis indica Mital and Lal, 1976 was originally described from Channa gachua Hamilton (Channidae) in Kali Nadi River, Aligarh, India. The parasite was later placed in the subgenus Brevitritospinus Amin, Heckmann, Ha, Luc, and Doanh, 2000 . Our collection from the spotted snakehead Channa punctatus Bloch & Schneider in another locality of the same stream in Aligarh produced many specimens with variable traits, revealing new structures that have never before been described in the Acanthocephala, especially relating to the ducted trunk spines. The proboscis has 4 circles of 10 hooks each, with hooks in the anterior 2 circles being considerably larger than those in the posterior 2 circles. Y-shaped trunk spines are ducted in 2 regions separated by a spineless zone. The anterior collar spines are in complete rings of 9-17 circles of crowded spines and the larger posterior trunk spines are in 1 (posterior) to 41 (anterior) circles extending to level of cement glands in males posteriorly. Considerable variations from the original description and new structures are reported for the first time.

Helminth Parasites of Little Cormorant, Phalacrocorax niger from central District Sanghar of Sindh Pakistan were investigated during December 2014-2015. Little Cormorant,P. niger is fish eating, migratory cum resident bird, harbour diverse parasites and commonly found in water bodies of the study area. Eleven hosts (P. niger) were examined in Parasitological Laboratory of Zoology department, Sindh University Jamshoro. Only one host was harbouring two specimens of acanthocephalan. These were collected from intestine and have proboscis with four circles of spines, eleven circle of collar spine with 14 spines in each circle, sacculate proboscis receptacle, tubular lemenisci, cylindrical testes and long cement glands. These features correspond to generic features of genus PallisentisVan Cleave, 1928. However, genus Pallisentis usually collected from freshwater fishes and has not been reported from birds. Therefore, present infection in Little Cormorant might be result of its piscivorous feeding habit. Present paper deals first record of genusPallisentisVan Cleave, 1928 in Little Cormorant, P. niger from Pakistan. Keywords: Acanthocephalan; Little Cormorant; Phalacrocorax niger; Pallisentis; Intestine http://dx.doi.org/10.19045/bspab.2016.50163

The para-receptacle structure (PRS) was first described in Neoechinorhynchus (Neoechinorhynchus) qa- tarensis Amin, Saoud, and Alkuwari, 2002 (Neoechino- rhynchidae), as a prominent vesicle connected proximally to the anterior body wall and distally to the posterior wall of the proboscis receptacle then extending into the body cavity of males and females as a posterior conduit tube. The PRS has since been observed in Neoechinorhynchus (Neoechino- rhynchus) golvani Salgado-Maldonado, 1978 (a new sub- generic diagnosis), and described in a member of another eoacanthocephalan family, Acanthogyrus (Acanthosentis) parareceptaclis Amin, 2005 (Quadrigyridae). In the latter species, a similar structure was also observed at the posterior end of the trunk. Our optical and transmission electron mi- croscopy (TEM) observations in specimens of N. qatarensis show the PRS as a tandemly arranged set of nucleated cells delimited by a double-walled membrane and a muscular wall. It appears to be contractile with a secretory function related to changes in the hydrostatic pressure that may be associated with the extrusion and retraction of the proboscis in worms with weakly developed proboscis receptacle mus- culature. This is the first detailed study of the PRS and of its proposed function in the only 3 acanthocephalan species from which it has been identified to date. It is considered as an archaic structure present only in a few representatives of some primitive taxa having only a single-walled proboscis receptacle wall.

Pallisentis (Pallisentis) sp. (= Acanthocephalorhynchoides sp.) Host: Schizothorax pelzami Locality: Hamoon Lagoon, Sistan and Baluchestan Province (Sharif-Rohani 1995), Published as part of Tavakol, Sareh, Amin, Omar M., Luus-Powell, Wilmien J. & Halajian, Ali, 2015, The acanthocephalan fauna of Iran, a check list, pp. 237-258 in Zootaxa 4033 (2) on page 241, DOI: 10.11646/zootaxa.4033.2.3, http://zenodo.org/record/233772, {"references":["Sharif-Rohani, M. (1995) Study of fish parasites in Hamoon Lagoon. Scientific report of Abzigostar Company, Tehran, 68 pp."]}

Pallisentis (Pallisentis) cholodkowskyi (Kostylew, 1928) Amin, 1985 Host: Ap. vladykovi Locality: Gandoman Lagoon, Chaharmahal and Bakhtiari Province (Raissy et al. 2011) Host: Capoeta aculeata Locality: Choghakhor Lagoon, Chaharmahal and Bakhtiari Province (Fadaei-fard et al. 2001), 15 Khordad Lake, Delijan, Esfahan Province (Shafei 2002), Zayandehrud River, Esfahan Province (Mehdipour 2006) Host: Cap. bushei Locality: Zayandehrud River, Esfahan Province (Williams et al. 1980) Host: Cap. capoeta Locality: Zayandehrud River, Esfahan Province (Williams et al. 1980), Mahabad Dam Lake (Mohamadi 1997), Golestan Park River, Golestan Province (Mokhayer et al. 2000) Host: Cap. damascina Locality: Zayandehrud Dam, Esfahan Province (Kasraei 2001), Zayandehrud River, Esfahan Province (Mehdipour 2006) Host: Cap. trutta Locality: Vahdat Dam Lake, Kordestan Province (Barzegar & Jalali 2006) Host: Carassius carassius Locality: Zayandehrud Dam, Esfahan Province (Kasraei 2001) Host: Cyprinus carpio Locality: Mahabad Dam Lake, West Azerbaijan Province (Mohamadi 1997), Choghakhor Lagoon, Chaharmahal and Bakhtiari Province (Fadaei-fard et al. 2001), Zayandehrud Dam, Esfahan Province (Kasraei 2001), 15 Khordad Lake, Delijan, Esfahan Province (Shafei 2002) Host: Rutilus rutilus Locality: Mahabad Dam Lake, West Azerbaijan Province (Mohamadi 1997), Published as part of Tavakol, Sareh, Amin, Omar M., Luus-Powell, Wilmien J. & Halajian, Ali, 2015, The acanthocephalan fauna of Iran, a check list, pp. 237-258 in Zootaxa 4033 (2) on page 241, DOI: 10.11646/zootaxa.4033.2.3, http://zenodo.org/record/233772, {"references":["Kostylew, N. N. (1928) Acanthocephalen der Fische der Goktscha-Sees. Centralblatt fur Bakteriologie, Parasitenkunde und Infektionskrankheiten, Abteilung I. Orig., 108, 146 - 150.","Amin, O. M. (1985) Classification. In: Crompton, D. W. T. & Nickol, B. B. (Eds.), Biology of the Acanthocephala. Cambridge University Press, Cambridge, pp. 27 - 72.","Raissy, M., Ansari, M. & Moumeni, M. (2011) Parasite fauna of the Zagros tooth-carp, Aphanius vladykovi Coad, 1988 (Osteichthyes: Cyprinodontidae), in Gandoman Lagoon. Comparative Parasitology, 78 (1), 104 - 106. http: // dx. doi. org / 10.1654 / 4474.1","Shafei, M. (2002) Distribution and importance of fish Acantocephalans in 15 Khordad Dam Lake. Honors dissertation, Isfahan University of Technology, Isfahan, 79 pp.","Mehdipour, M. (2006) Parasites of native and introduced fishes of Zayandehrud River. Doctor of Philosophy dissertation, Islamic Azad University, Science and Research Branch, Tehran, 153 pp.","Williams, J. S., Gibson, D. I. & Sadighian, A. (1980) Some helminth-parasites of Iranian freshwater fishes. Journal of Natural History, 14, 685 - 699. http: // dx. doi. org / 10.1080 / 00222938000770581.","Mohamadi, R. (1997) Investigation of fish parasites in Mahabad Dam Lake, Doctor of Veterinary Medicine thesis, University of Urmia, Urmia, 112 pp.","Kasraei, M. (2001) Study on Acanthocephalans from fishes in Zayandehrud River. Master of Science thesis, Isfahan University of Technology, Isfahan, 86 pp.","Barzegar, M. & Jalali, B. (2006) Helminthes, Acanthocephala and Crustacean parasites of fishes in Vahdat Reservoir. Iranian Journal of Veterinary Science, 3, 229 - 234."]}

All 44 described species of the subgenus Acanthosentis Varma & Datta, 1929 are recognised as valid. These include two new species, Acanthogyrus (Acanthosentis)alternatspinus n. sp. from Rhodeus ocellatus ocellatus (Kner) (Cyprinidae) and A. (A.) parareceptaclis n. sp. from Cobitis biwae Jordan & Snyder (Cobitidae) in the Lake Biwa drainage, Japan. These are the first representatives of the subgenus Acanthosentis recorded from Japan. Most other species are found in the Indian subcontinent, but a few have been reported from China, elsewhere in Asia, Africa, Europe and Central America. Only A. (A.) alternatspinus has the lateral proboscis hooks in the apical and middle circles markedly displaced posteriorly but of equal size to the other hooks in the same circles and multi-branched lemnisci. Acanthogyrus (A.) parareceptaclis uniquely possesses parareceptacle structures in both sexes as well as a pair of cone-shaped genital jackets flanking the vagina (vaginal sleeve). Two new names are provided: Acanthogyrus (Acanthosentis) adriaticus nom. nov. for A. (A.) lizae Orecchia, Paggi & Radujkovic, 1988 nec Wang, 1896, and A. (A.) cheni nom. nov. for A. (A.) coiliae (Yamaguti) sensu Chen et al. (1973). A review of the species composition of Acanthosentis is provided and a key to its species and zoogeographical notes are included.

Acanthosentis cheni is a marine or brackish acanthocephalan found in fish. The complete mitochondrial genome of A. cheni (Acanthocephala: Quadrigyridae) is first sequenced. It is a circular molecule of 13,695 bp in size and consists of 12 protein-coding genes (PCGs), 20 transfer RNA (tRNA) genes, 2 ribosomal RNA (rRNA) genes. Except tRNA-Gln, all other mitochondrial genes were encoded on the heavy strand. The gene order and orientation of A. cheni mitogenome are basically identical to that of other acanthocephala. This study will facilitate the further research of the population genetics of this species and systematic analyses of the acanthocephala.

Late cystacanth stages were discovered in the haemocoel of the marine benthic harpacticoid Halectinosoma herdmani (T. & A. Scott, 1896) (Copepoda: Ectinosomatidae) collected off La Rochelle, France. This represents the first record of Acanthocephala infesting marine copepods. On the basis of the hook formula on the proboscis and the spine pattern on the trunk, the parasites were identified as juveniles of Acanthogyrus (Acanthosentis) lizae Orecchia, Paggi & Radujkovic, 1988 (Eoacanthocephala: Gyracanthocephala: Quadrigyridae) which utilizes the golden grey mullet Liza aurata (Risso, 1810) as the definitive host. The literature on acanthocephalans utilizing copepods as intermediate hosts is reviewed and some morphological details of both the cystacanth and host copepod are presented using differential interference contrast and scanning electron microscopy. Halectinosoma porosum Wells, 1967 from Inhaca Island (Mozambique) is formally transferred to Ectinosoma Boeck, 1865 as E. porosum (Wells, 1967)...

During a survey of freshwater fishes from Turkey two species of Acanthocephala, one of them new, were found. Pomphorhynchus tereticollis (Pomphorhynchidae) is reported at 24% prevalence in 37 Cobitis bilseli (Cobitidae) from Lake Beysehir, Konya, for the first time. The eoacanthoacaphalan Triaspiron aphanii gen. n. et sp. n. (Quadrigyridae), at a prevalence of 90%, is described from 29 Aphanius mento (Cyprinodontidae), from Kirkgoz Springs, Antalya. The new genus most closely resembles Raosentis Datta, 1947, both having a small spindle shaped trunk, and Acanthogyrus Thapar, 1927, both having a proboscis armature of three circles of hooks. Triaspiron differs from Raosentis in proboscis shape, cylindrical not globular, proboscis armature, three circles, a total of 16 hooks in all, not four circles, a total of 26-30 hooks in all, and trunk spination, two fields of spines in the anterior field with spines arranged in up to 40 circular rows, not a single field with 9-17 rows of spines. Triaspiron differs from Acanthogyrus in having fewer proboscis hooks, 16 compared with 18-24, arranged in three circles, one anterior and two posteriorly placed, with an unarmed region between, not three circles of hooks evenly spaced, and two fields of trunk spines, not one.

Acanthogyrus (Acanthosentis) barmeshoori n. sp. (Quadrigyridae) is described from the Persian tooth-carp, Aphanius farsicus Teimori, Esmaeili, and Reichenbacher, 2011 (Cyprinodontidae) in the Maharlu Lake basin, southern Iran. Aphanius farsicus is an endemic freshwater fish found in streams and springs that drain into Maharlu Lake, Shiraz, Iran. The new species is the smallest of all the 44 known species of the subgenus Acanthosentis Verma and Datta, 1929, measuring between 0.26 and 1.68 mm in length. It is further distinguished by having a short cylindrical proboscis with very long anterior hooks widely separated from very small hooks in 2 very close circles posteriorly (hook length ratio about 4:1). It is separated from 4 other species of Acanthosentis with similar proboscis armature but with less-extreme diversification of hook length. The new species is also distinguished in having anterior para-receptacle structures (PRS) and a similar posterior structure like those reported in only 1 other species of Acanthosentis from Japan. Proboscis receptacle is single walled with a large triangular cephalic ganglion. Testes are large, pre-equatorial, and Saefftigen's pouch is prominent. Fourteen to 25 circles of spines cover the anterior 50-70% of the trunk, but a few spines may be present at posterior end of trunk. This is the first species of Acanthosentis where SEM images, showing external morphological details, are provided. From a total of 357 fish specimens examined between July 2006 and June 2007, 173 specimens (48.5%) were infected with individuals of the new species. The prevalence of infection decreased with increasing fish size. The parasite was observed all year, with the highest abundance and intensity in May while the prevalence was highest in February. The prevalence of acanthocephalans decreased with increasing fish size. While most worms were recovered in fish within the length range of 18-29.9 mm, 1 of the longest parasites (1.68 mm long) was found in fish within the range of 30-33.9 mm long.

Family Quadrigyridae Van Cleave, 1920 Machadosentis travassosi Noronha, 1992 ���adult Host and habitat: Gymnothorax ocellatus (MAR) Locality: Off Bahia Reference: Noronha (1992) Palliolisentis quinqueungulis Machado-Filho, 1960 ���adult Hosts and habitat: Triportheus angulatus (FW), Triportheus paranensis (FW) Locality: Salobra, Mato Grosso References: Machado Filho (1960), Thatcher (1991) Quadrigyrus brasiliensis Machado Filho, 1941 ���adult Hosts and habitat: Hoplerythrinus unitaeniatus (FW), Hoplias malabaricus (FW). Locality: Salobra, Mato Grosso, Upper Parana River/Paran�� References: Machado Filho (1941), Thatcher (1991), Pavanelli et al. (2004) Quadrigyrus machadoi Fabio, 1983 ���larva and adult Hosts and habitat: Cichla monoculus (FW���larva), Hemisorubim platyrhynchos (FW���larva), Gymnotus sp. (FW���adult), Hoplias malabaricus (FW���adult) Localities: Parana River/Paran��, S��o Paulo, Rio de Janeiro, Rio Ba��a, Mato Grosso do Sul References: Fabio (1983), Weiblen and Brand��o (1992), Pavanelli et al. (2001, 2002, 2004), Machado et al. (2000), Guidelli et al. (2003), Isaac et al. (2004), Rosim et al. (2005) Quadrigyrus torquatus Van Cleave, 1920 ��� adult Hosts and habitat: Acestrorhynchus lacustris (FW), Hoplias malabaricus (FW), Leporinus lacustris (FW) Localities: Upper Parana River/Paran��, Rio de Janeiro References: Fabio (1983), Thatcher (1991) Pavanelli et al. (2004), Carvalho et al. (2003), Guidelli et al. (2006) Quadrigyrus sp.���adult Hosts and habitat: Astyanax altiparanae (FW), Iheringichthys labrosus (FW), Pachyurus squamipennis (FW), Prochilodus lineatus (FW) Localities: Upper Parana River/Paran�� S��o Francisco River, Mato Grosso, Paran�� References: Pavanelli et al. (2004), Lizama et al. (2005), Moreira et al. (2005),Takemoto et al. (2005), Published as part of Santos, Cl��udia P., Gibson, David I., Tavares, Luiz E. R. & Luque, Jos�� L., 2008, Checklist of Acanthocephala associated with the fishes of Brazil, pp. 1-22 in Zootaxa 1938 on pages 7-8, DOI: 10.5281/zenodo.184999, {"references":["Noronha, D. (1992) On Machadosentis travassosi n. g., n. sp. (Eoacanthocephala: Quadrigyridae) parasite of a moray Gymnothorax ocellatus in Brazil. Memorias do Instituto Oswaldo Cruz, 87, 151 - 153, suppl.","Machado Filho, D. A. (1960) Um novo genero da familia Quadrigyridae Van Cleave, 1920 (Metacanthocephala, Palaeacanthocephala). Revista Brasileira de Biologia, 20, 79 - 84.","Thatcher, V. E. (1991) Amazon fish parasites. Amazoniana, 11, 263 - 572.","Machado Filho, D. A. (1941) Sobre alguns acantocefalos provenientes do estado de Mato Grosso. Revista Brasileira de Biologia, 1, 57 - 61.","Fabio, S. P. (1983) Sobre alguns Acanthocephala parasitos de Hoplias malabaricus. Arquivos da Universidade Federal Rural do Rio de Janeiro, 6, 173 - 180.","Weiblen, A. M. & Brandao, D. A. (1992) Levantamento parasitologico em Hoplias malabaricus, Bloch, (1794) (Traira) de aguas da regiao de Santa Maria - RS. Ciencia Rural, 22, 203 - 208.","Pavanelli, G. C., Guidelli, G. M., Isaac, A. & Takemoto, R. M. (2001) Composicao e estrutura da comunidade endoparasitaria de Hemisorubim platyrhynchos (Valenciennes, 1840) (Pisces: Pimelodidae) do Rio Baia, na planicie de inundacao do Alto Rio Parana, Brasil. Acta Parasitologica Portuguesa, 8, 206.","Pavanelli, G. C., Eiras, J. C. & Takemoto, R. M. (2002) Doencas de peixes. Profilaxia, diagnostico e tratamento. 2 nd Edit. Editora Universidade Estadual de Maringa, Maringa, 305 pp.","Machado, P. M., Almeida, S. C. & Pavanelli, G. C. (2000) Ecological aspects of endohelminths parasitizing Cichla monoculus Spix, 1831 (Perciformes: Cichlidae) in the Parana River near Porto Rico, State of Parana, Brazil. Comparative Parasitology, 67, 210 - 217.","Isaac, A., Guidelli, G. M., Franca, J. G. & Pavanelli, G. C. (2004) Composicao e estrutura das infracomunidades endoparasitarias de Gymnotus spp. (Pisces: Gymnotidae) do rio Baia, Mato Grosso do Sul, Brasil. Acta Scientiarum, Biological Sciences, 26, 453 - 462.","Rosim, D. F., Ceccarelli, P. S. & Silva-Souza, A. T. (2005) Parasitismo de Hoplias malabaricus (Bloch, 1794) (Characiformes, Erythrinidae) por Quadrigyrus machadoi Fabio, 1983 (Eoacanthocephala, Quadrigyridae) de uma lagoa em Aguai, Estado de Sao Paulo, Brasil. Revista Brasileira de Parasitologia Veterinaria, 14, 147 - 153.","Carvalho, S., Guidelli, G. M., Takemoto, R. M. et al. (2003) Ecological aspects of endoparasite fauna of Acestrorhynchus lacustris (Lutken, 1875) (Characiformes, Acestrorhynchidae) on the Upper Parana River floodplain, Brazil. Acta Scientiarum, Biological Sciences, 25, 479 - 483.","Guidelli, G. M., Tavechio, W. L. G., Takemoto, R. M. & Pavanelli, G. C. (2006) Fauna parasitaria de Leporinus lacustris e Leporinus friderici (Characiformes, Anostomidae) da planicie de inundacao do alto rio Parana, Brasil. Acta Scientiarum Biological Sciences, 28, 281 - 290."]}

Twenty-three genera comprising thirty-four named and thirteen undetermined species of acanthocephalans are associated with one hundred and nineteen marine, brackish and freshwater fish species from Brazil. These are listed, with information on their hosts, habitat, distribution and records. A key to these parasites at the generic level is provided.

Studies on the seasonal population dynamics ofPallisentis (Neosentis) celatus(Acanthocephala: Quadrigyridae) in the intestine of the rice-field eelMonopterus albusfrom the paddies and ditches in the Dong-ting Lake basin of China, were carried out with samples taken from June 2002 to May 2003. Prevalences were above 21% in all seasons sampled and with a distinct seasonal trend, which was highest (45.81%) in the spring and decreased by degrees. The mean intensity of infection was above 4.0 worms per fish. The maximum intensity of worms recovered from a single fish was 86 in the autumn of 2002. No significant seasonal differences were found in mean intensities, and differences in the mean abundance between winter and spring, winter and autumn were significant. Over-dispersed distributions ofP. (N.) celatusin the host population, due to heterogeneity and feeding habits, were observed in all seasons. The size composition of both sexes ofP. (N.) celatusshowed males between 2.0 mm and 14.0 mm and females between 2.2 mm and 22.2 mm, with the main recruitment phase in the worm populations occurring in the summer and autumn, especially in the autumn, with the lowest recruitment occurring in the winter. The maturation and copulation of worms were mainly focused in the spring season. The sex ratio of female to male was both high in summer (1.09:1) and autumn (1.08:1). The higher proportion of females and the change in the worm sex ratio in summer can be attributed to the reduced longevity of male worms. As immature male worms exhibit a higher proportion of the worm population than females in all seasons, further studies are needed to determine if such a situation compensates for the shorter life span of males.

The acanthocephalan fauna of Iran is reported for the first time since the report of Pomphorhynchus perforator (von Linstow, 1908) Meyer, 1932 in 1964. The knowledge of the acanthocephalan biodiversity of Iran, with parasite-host and host-parasite checklists, is presented. The species of Acanthocephala are presented in alphabetical order, followed by the species of hosts, localities and references. A total of 30 known species of Acanthocephala from 21 genera, 12 families and 7 orders are reported from 80 species of different vertebrates of Iran. One species, Moniliformis moniliformis (Bremser, 1811) Travassos, 1915 was recorded from humans. The group of hosts with the largest number of reported species of acanthocephalan is Actinopterygii (ray-finned fishes).

Pallisentis rexus Wongkham & Whitfield, 1999 (Eoacanthocephala: Quadrigyridae) infects the freshwater snakehead fish, Channa striata, in the Chiang Mai Basin, Thailand. All stages of egg development within the body cavity of the female parasite were observed, using transmission electron microscopy. Changes in mature eggs after contact with water were also investigated. The mature egg has five egg envelopes separated from each other by four gaps. The fertilization membrane, which is formed first, is pushed centrifugally by other, subsequently formed, envelopes and gaps, which produces a final total shell thickness of 8–36 μm around the acanthor. The disappearance of the outermost layer and the unpleating of an adjacent inner layer causes the expansion of eggs on contact with water. The volume of an expanded egg is approximately 27 times that of an unexpanded one, but the density of eggs is reduced from a value greater than water to one almost equal to water. This is believed to aid the dispersion of eggs.

Machadosentis travassosi n. g., n. sp. an acanthocephalan parasite of a moray are proposed after comparison with the related genera in Quadrigyridae VVan Cleave, 1920. The new genus differs from the other related by the arrangement of proboscis hooks (five circles of rows with five hooks each, with well developed roots) besides the distribution of cuticular spines.

Pallisentis nagpurensis (Bhalerao, 1931) Baylis, 1933 from the small intestine of the gabus, Ophiocephalus striatus, from Depok, Indonesia, is redescribed. Additional data are given for the males, and for females for which previous descriptions were either inadequate or absent. The relationship between P. nagpurensis (Bhalerao, 1931) Baylis, 1933 and Pallisentis gaboes (MacCallum, 1918) Van Cleave, 1928 is clarified.

Nearly thirty specimens of Hexaspiron nigeriensis from the intestine of the fish Heterosynodontis membranaceus captured in the Niger river, gave the opportunity of a redescription of this acanthocephalan species. The presence of 7 crowns of minute spines on the fore part of the trunk obliged to transfert H. nigeriensis from Neoechinorhynchidae family into Quadrigyridae family.

The ultrastructural study of the Eoacanthocephala sperm cell shows a variation from 0 to 5 in the number of the axial fibers in the axoneme. All the species of the order Eoacanthocephala available to us show this variation; moreover, every individual possesses simultaneously several different structural types. So, we are dealing with a new flagellar organization: 9+n, with 0 less than or equal to n less than or equal to 5. In the Quadrigyridae and the Tenuisentidae families, n varies from 0 to 4, with a maximum of 2 for most individuals, exceptionally at 1 for some individuals. In the Neoechinorhynchidae family, n varies from 0 to 5 with a conspicuous prevalence of 3 (from 84 to 99%, according to the individual). These results prompted us to reexamine the two other orders of Acanthocephala in which the structural types 9+2 or 9+0 have been considered as fixed. Indeed, we have found a few flagella the structure of which is different from the prevalent one. It seems, therefore, that the number of the central fibers of the axoneme in the Acanthocephala sperm cell is never absolutely fixed.

A new acanthocephalan, Acanthogyrus partispinus nov. sp. (Quadrigyridae), is described from the Malayan freshwater cyprinid, Hampala macrolepidotavan Hasselt. Its affinity to the Indo-Malaysian species of this genus is discussed.

The present paper gives an account of a new genus and species of an Acanthocephala of the family Quadrigyridae Van Cleave, 1920, collected from the intestine of a fresh water fish P. garua (= Clupisoma garua) at Patna. Only one of a large number of fishes examined harboured these worms. Their incidence, therefore, appears to be low. The number of specimens recovered from the host were two males and six females.

Acanthosentis acanthuri Cable et Quick 1954 is redescribed from the type host, Acanthurus coeruleus, from Tobago, W.I. The sizes of proboscis hooks in the 3 circles is corrected to 66 to 88 mu, 30 to 40 mu, and 30 to 40 mu.