Hook Morphology Research Articles

Intraspecific morphological and genetic variation in South African populations of a polystomatid flatworm parasite

The African Clawed Frog Xenopus laevis, a global invader, exhibits a marked phylogeographic divergence among native populations in southern Africa, which seems to enhance its invasive potential. The polystomatid flatworm, Protopolystoma xenopodis, is the frog’s most frequently co-introduced metazoan parasite. In an integrative approach, we utilised morphometrics and molecular markers to assess variation in P. xenopodis in its native range. We measured twelve key morphological characters from 23 flatworms and compared these statistically between flatworms collected from the northern- and southernmost distribution in South Africa. Phylogenetic analyses were based on three concatenated markers, namely 28S and 12S rDNA and COX1, from six flatworms. The combination of five morphological characters, which involve egg size, gut morphology and size of the attachment hooks, differentiated northern and southern populations of P. xenopodis. The multilocus phylogenetic analyses showed a cluster of northern P. xenopodis and two southern lineages with more basal positioning. These findings demonstrate a relatively high level of intraspecific variation in P. xenopodis in its native range. The presented intraspecific variation of P. xenopodis could be potentially informative to trace geographic origin in its non-native range.

Comparative diversity in glochidia of Australasian freshwater mussels

Most freshwater mussels have larvae (glochidia in Unionidae, Margaritiferidae and Hyriidae) that are parasitic on fishes. This study describes and compares the diversity of glochidia among 17 species of Australasian Hyriidae. Here, scanning electron microscopy was used to illustrate shell morphology, while patterns of diversity in size, shape and morphological characteristics were analysed quantitatively and qualitatively with Principal Component, Linear Discriminant, and Multiple Correspondence Analyses to separate species with varying degrees of discrimination. Results showed shell lengths ranged from 50 to 390 μm. Shape varied, from sub-oval to sub-triangular, bilaterally symmetrical to scalene, and hook morphology varied from unicuspid, bicuspid, tricuspid or complex with varying length and structure. Unique observations of this study include the consistent variation in glochidial release mechanisms among Australian subfamilies and New Zealand genera. Hyridellini species and Echyridella aucklandica (Gray and Dieffenbach, 1843) are released either freely or as “mesoconglutinates” (presumed brood lures), whereas Velesunioninae and Echyridella menziesii (Gray and Dieffenbach, 1843) release glochidia in “amorphous mucous conglutinates”. Hyridellini predominantly occur within perennially flowing rivers of coastal south-eastern Australia with generally low turbidity, whereas the Velesunioninae occur more typically in slower flowing, intermittent waters, many prone to extended periods of high turbidity. Thus, where Hyridellini occur, mesoconglutinates as visual brood lures may be a more efficient mechanism for infesting host fishes than the passive infestation strategy typical of velesunionine species frequenting more turbid waters. Finally, this study presents systematic descriptions of glochidia and a provisional key for identification of Australasian hyriid glochidia, making an important contribution to the current understanding of taxonomy and life history traits, both critical for hyriid conservation.

Comparison of Protoscolex Hook Morphologies in Human, Sheep, Cattle Echinococcus granulosus Isolates

Objective: Cystic echinococcosis (CE) is an important parasitic infection caused by Echinococcus granulosus (E. granulosus) larvae, adults of which live in Canidae. Although CE is observed in all over the world, it is more prevalent in developing and underdeveloped nations.
 Material and Method: This study was conducted on a total of 60 cyst samples, including 20 sheep and 20 cattle slaughtered in the abattoir and 20 patients operated with the diagnosis of KE in University Medical Center between the dates June 2018 and April 2019. The collected cyst fluids were centrifuged and protoscolices were collected. For each of these hosts, 20 large and 20 small hooks were examined. Large hook length (LHL), small hook length (SHL), large hook width (LHW), small hook width (SHW), large hook blade length (LHBL), small hook blade length (SHBL) were measured. The measurements were made by a single person, taking into account the characteristics specified by Hobbs et al. (1990). The results were evaluated with the SPSS program.
 Results: The average of human, sheep and bovine LHL measurements were 21.710 ± 1.073 μm, 24.322 ± 1.073 μm, 25.223 ± 1.073 μm; SHL measurements were 16.946 ± 0.840 μm, 20.746 ± 0.911 μm, 21.199 ± 0.977 μm; LHW measurements were 5.437 ± 0.358 μm, 7.817 ± 0.729 μm, 8.528 ± 0.589 μm, respectively; SHW measurements were 7.229 ± 0.631 μm, 6.417 ± 0.507 μm, 6.488 ± 0.463 μm, respectively; LHBL measurements were 13.236 ± 0.746 μm, 13.862 ± 0.767 μm, 13.345 ± 0.728 μm; SHBL measurements were determined as 8.918 ± 0.471 μm, 9.414 ± 0.483 μm, 9.457 ± 0.476 μm, respectively. The length, width and blade lengths of large and small hooks isolated from human, sheep and cattle were significant difference between all groups. When hook morphology measurements were grouped in pairs as human-sheep, human-cattle and sheep-cattle and analyzed statistically; It was determined that LHL, SHL, SHW and SHBL were significantly different between human-cattle and human-sheep, but not between sheep-cattle. It was found that LHW was significantly different between human-cattle and sheep-cattle, while LHBL was significantly different only between human-sheep.
 Conclusion: The morphological features of the large and small hooks of E. granulosus may represent morphological adaptation in vertebrate hosts. For this reason, it is thought that morphological parameters can be useful in the differentiation of isolates and can be used together with molecular studies in the future

Taenia crassiceps Cysticercosis in a Wild Muskrat and a Domestic Dog in the Northeastern United States

Taenia crassiceps is a parasite of wild canids and dogs that serve as definite hosts, harboring the adult cestode, whereas rodents are the intermediate hosts in which the metacestode/cysticercus/larval stage occurs. Fecal-oral transmission ensures the parasite's lifecycle. At times, dogs and humans act as accidental intermediate hosts. Despite the public health concern this parasite warrants, its epidemiology remains unclear. In this report, we document the occurrence of metacestodes of T. crassiceps in a muskrat (Ondatra zibethicus) and a domestic dog from the northeastern United States, a development that necessitates increased awareness and surveillance to tackle this disease of "one health" significance. Taenia crassiceps cysticercosis was confirmed in an adult male muskrat in February 2018 and in a 4-year-old female spayed Staffordshire Bull Terrier in December 2020. Parasitological and histopathologic examination of both cases revealed cysticerci with the characteristic rostellar hook morphology that aided in Taenia species identification. In the muskrat case specifically, partial sequencing of the mitochondrial cytochrome oxidase gene confirmed the species identity as T. crassiceps. We report T. crassiceps occurrence in a muskrat in New York State for the first time and document a case presentation in a domestic dog from New Jersey that was infected with metacestode stages of this parasite. Given the detection of this parasite in the northeastern United States, T. crassiceps infection, which otherwise is considered a rare disease, should be on the radar of veterinary, medical and wildlife biologists for timely diagnosis and interventions.

Mechanical properties and failure analysis of refill friction stir spot-welded 5052/2A12 joints

The mechanical properties and failure process of 2 mm-thick 5052 Al and 6 mm-thick 2A12 Al fabricated by refill friction stir spot-welding were investigated. The hooks were bent respectively downwards and upwards at plunge depths smaller and larger than the upper plate thickness. The joint area of the lap interface and bearing thickness of the upper plate were related to the hook direction. The tensile shear failure load was affected by structural characteristics and hardness of the joints. Stress concentration occurred in the hook and strain expanded with the hook during fracture. There were two fracture modes: shear fracture and shear plug fracture, where both cracks passed through the hook and fracture morphology of the hook was less plastic.

A new sexually dimorphic Hyphessobrycon from the western Amazon basin (Characiformes: Characidae).

A new species of Hyphessobrycon presenting dimorphic males is described from the western Amazon basin in Brazil, Colombia, Ecuador, and Peru. The new species has been mistakenly identified in the literature with the non-congener Hemigrammus marginatus, with which shares a similar color pattern by presenting dark patches of dark pigmentation on caudal-fin lobes. It can be distinguished from the latter species, as well as from Hemigrammus durbinae, and two similar congeners, Hyphessobrycon diancistrus and Hy. otrynus, all of which sharing the same caudal fin color pattern, by the combination of presenting a dark patch of pigmentation on the dorsal fin, a single large anal-fin hook at the last unbranched anal-fin ray in mature males, and a moderately high body depth (22.432.5 % SL, mean 28.4 %). The new species is more similar to Hyphessobrycon diancistrus, which is putatively its closely related taxon. A putative close relationship with Hyphessobrycon otrynus, and with a non-congener presenting a distinct color pattern but sharing a similar sexual dimorphism on anal-fin hook morphology, Hemigrammus boesemani, is suggested.

Effect of Rotation Speed and Steel Microstructure on Joint Formation in Friction Stir Spot Welding of Al Alloy to DP Steel

In this work, friction stir spot welding of 5754 aluminum alloy to dual phase steel was investigated using two different ratios of martensite and ferrite (0.38 and 0.61) for steel sheet initial microstructure and varying tool rotation speed (800, 1200 and 2000 rpm). The effect of these parameters on the joint formation was evaluated by studying the plunging force response during the process and the main characteristics of the joint at (i) macrolevel, i.e., hook morphology and bond width, and (ii) microlevel, i.e., steel hook and sheet microstructure and intermetallic compounds. The plunging force was reduced by increased tool rotation speed while there was no significant effect from the initial steel microstructure ratio of martensite and ferrite on the plunging force. The macrostructural characterization of the joints showed that the hook morphology and bond width were affected by the steel sheet initial microstructures as well as by the tool rotation speed and by the material flow driver; tool pin or shoulder. At microstructural level, a progressive variation in the ratio of martensite and ferrite was observed for the steel hook and sheet microstructure. The zones closer to the tool presented a fully martensitic microstructure while the zones away from the tool showed a gradual increase in the ferrite amount until reaching the ratio of ferrite and martensite of the steel sheet initial microstructure. Different types of FexAly intermetallic compounds were found in three zones of the joint; the hook tips, in the hooks close to the exit hole and in the corner of the exit hole. These compounds were characterized by a brittle behavior with hardness values varying from 456 to 937 HV01.

A New Species of Paradiplozoon (Monogenea: Diplozoidae), A Gill Parasite of the Schizothorax Fish (Cyprinidae: Schizothoracinae) from the Yarkand River, Xinjiang, China.

Monogeneans of the genus Paradiplozoon were found on the gills of specimens of five species of schizothoracid caught using fyke nets in the upper stream of the Yarkand River, Xinjiang, China in May-August 2019. The preserved parasite were stained with boric acid magenta and hematoxylin, respectively. Morphological observations, line drawings, photomicrographs and measurements were made in Nikon ECLIPSE E200 imaging optical microscope and digitally edited. The molecular analysis included the study of the sequence of the second internal transcribed spacer (ITS 2) of the ribosomal DNA region, calculation and analysis of genetic distance, with phylogenetic reconstructions based on the Bayesian inference and Maximum Likelihood analysis. The natural infection rate of host fish was 10-88%. Morphological analysis indicated that the average length of the new species was 2.125mm while the width was 0.69mm. The anterior part was 1.387mm in length and the average length of the posterior part was 0.545mm. The vitellaria was well-developed and located in the front of the body. A single ovary (oval shaped) was located at the back end of the reproductive binding area. A testis (irregular mass) was located behind or parallelled to the ovary. The new species can be distinguished from all the recorded Paradiplozoon species in terms of morphological characteristics such as haptor, clamp and central hook morphology, intestine shape and body size. In addition, the second internal transcribed spacer (ITS 2) of the ribosomal DNA region of the diplozoid was compared with that of known diplozoids previously published. It indicated that there were significant differences between the new species and the published diplozoids. Both morphological and molecular analysis support that the diplozoid is a new species. Based on the sampling location, the new species was named Paradiplozoon yarkandense n. sp.

Apical Sperm Hook Morphology Is Linked to Sperm Swimming Performance and Sperm Aggregation in Peromyscus Mice.

Mammals exhibit a tremendous amount of variation in sperm morphology and despite the acknowledgement of sperm structural diversity across taxa, its functional significance remains poorly understood. Of particular interest is the sperm of rodents. While most Eutherian mammal spermatozoa are relatively simple cells with round or paddle-shaped heads, rodent sperm are often more complex and, in many species, display a striking apical hook. The function of the sperm hook remains largely unknown, but it has been hypothesized to have evolved as an adaptation to inter-male sperm competition and thus has been implicated in increased swimming efficiency or in the formation of collective sperm movements. Here we empirically test these hypotheses within a single lineage of Peromyscus rodents, in which closely related species naturally vary in their mating systems, sperm head shapes, and propensity to form sperm aggregates of varying sizes. We performed sperm morphological analyses as well as in vitro analyses of sperm aggregation and motility to examine whether the sperm hook (i) morphologically varies across these species and (ii) associates with sperm competition, aggregation, or motility. We demonstrate inter-specific variation in the sperm hook and then show that hook width negatively associates with sperm aggregation and sperm swimming speed, signifying that larger hooks may be a hindrance to sperm movement within this group of mice. Finally, we confirmed that the sperm hook hinders motility within a subset of Peromyscus leucopus mice that spontaneously produced sperm with no or highly abnormal hooks. Taken together, our findings suggest that any adaptive value of the sperm hook is likely associated with a function other than inter-male sperm competition, such as interaction with ova or cumulous cells during fertilization, or migration through the complex female reproductive tract.

Dissimilar friction stir lap welding of AA2198 and AA7075 sheets: forces, microstructure and mechanical properties

This paper investigates the dissimilar friction stir lap welding of AA2198 and AA7075 sheets. The influence of processing parameters, namely welding speed and tool rotational speed on joint features, microstructure, and mechanical properties were studied by implementing a full factorial design of experiments. Axial and transversal forces were continuously measured during the welding process using a sensed fixture aiming at the correlation of processing parameters, forces, and quality of the achieved joints. Obtained outcomes showed hook formation for all the combination of parameters and the existence of a very narrow processing window in which it is possible to avoid the formation of internal defects, such as grooves and tunnels. The influence of the weld bead morphology on the lap shear strength was elucidated proving that the strength is ruled by the hook morphology. The microstructure of the joints was studied and discussed considering also the microhardness distribution.Graphical abstract

New apinnate Prionospio (Annelida: Spionidae) species from southeastern Brazil

Eleven apinnate Prionospio Malmgren, 1867 species were recorded from southeastern Brazil, both from coastal environments and the continental slope. Ten of these species-Prionospio acuta sp. nov., P. fosterae sp. nov., P. kinbergi sp. nov., P. hartmanae sp. nov., P. mutata sp. nov., P. cinthyae sp. nov., P. corrugata sp. nov., P. alexandrae sp. nov., P. biancoi sp. nov., and P. quadrilamellata sp. nov. are new to science, whereas P. cf. delta Hartman, 1965 has been previously recorded in Brazil. Most novel species correspond to multibranchiate forms, but can be distinguished based on the prostomial shape, presence of dorsal crests, branchial morphology, presence of sabre chaetae, morphology of parapodial lamellae, and hook morphology. An identification key and a comparison table to all eleven species recorded in the area are provided.

Two new species of Acanthobothrium Blanchard, 1848 (Cestoda: Onchoproteocephalidea) from rajiform batoids off Argentina.

Two new species of Acanthobothrium Blanchard, 1848 were collected from rajiform batoids along the coast of Argentina. They are Acanthobothrium carolinae sp. n. from Bathyraja magellanica (Philippi) and Acanthobothrium domingae sp. n. from Dipturus brevicaudatus (Marini). Both belong to category 1 and 2 because their total length is lower than 15 mm, they have fewer than 50 proglottids, fewer than 80 testes and a symmetric or asymmetric ovary. Acanthobothrium carolinae sp. n. differs from all congeners by the following combination of features: proglottid apolysis, hook morphology, microthrix pattern on the cephalic peduncle and distribution of the vitelline follicles. Acanthobothrium domingae sp. n. is unique in the combination of proglottid apolysis, total length, number of proglottids, hook and septal morphology, microthrix pattern on the cephalic peduncle, number and distribution of testes, cirrus sac length, distribution of the vitelline follicles and genital pore position. The discovery of these species increases the number of species of Acanthobothrium parasitising rajiform batoids off Argentina from one to three. All three species have a unique pattern of distribution of the gladiate spinitriches along the length of the cephalic peduncle, i.e., gladiate spinitriches being interrupted in a medial line both dorsally and ventrally.

Schizorhynchia (Platyhelminthes, Rhabdocoela) from eastern Cuba, with the description of fifteen new species.

We report on the schizorhynch species collected in a survey in the eastern region of Cuba. Eighteen species were identified, of which only three are known to science: Cheliplana asica, C. terminalis, and Carcharodorhynchus flavidus. The 15 new species belong to three different genera: Cheliplana (five species), Carcharodorhynchus (four species), and Schizochilus (six species). The five new species of Cheliplana (C. gibarenha sp. n., C. santiaguera sp. n., C. spuriaseminalis sp. n., C. subproximalis sp. n. and C. verrucosa sp. n.) differ from their congeners in the detailed morphology of the proboscis hooks and the atrial organs. The proboscis hooks bear a distal small hook in C. verrucosa sp. n., a feature only shared with C. paradoxa. Two of the four new species of Carcharodorhynchus (C. smilodon sp. n. and C. papillaris sp. n. ) are very similar to C. flavidus in that the toothed belts of the proboscis are not continuous. However, they clearly differ from that species and from each other in the detailed construction of the teeth and copulatory organ. Carcharodorhynchus spiniformis sp. n. and C. nativus sp. n. can also be distinguished from the other species of Carcharodorhynchus by the detailed construction of the proboscis teeth and copulatory organ. The six new species of Schizochilus here described show a spiny cirrus around a central stylet. Two species lack the distal sclerotized cap of the copulatory bulb: S. favus sp. n. and S. bueycabonensis sp. n.. All new species of Schizochilus can be distinguished from each other and their congeners by the detailed construction of the hard parts (cirrus and stylet) of the copulatory organ.

New Species of Gyrodactylus von Nordmann, 1832 from Native Fish from Chiapas, Mexico, Studied by Morphology and Molecular Analyses.

Three new species of Gyrodactylus von Nordmann, 1832 are described from Poeciliopsis hnilickai and Tlaloc labialis (syn. Profundulus candalarius and Profundulus labialis) from the state of Chiapas, Mexico. Gyrodactylus chiapaneco n. sp. is described from T. labialis. Gyrodactylus guatopotei n. sp. was found to infect P. hnilickai. Gyrodactylus tlaloci n. sp. is described from T. labialis. The new species were characterised morphologically (haptoral hooks) and molecularly (sequences of the Internal Transcribed Spacer region (ITS1-5.8S-ITS2) of rDNA). During a survey in March 2017 in the state of Chiapas, individuals of Tlaloc labialis were collected by electrofishing from Arroyo Ojo de Agua and from Río Hondo, Ixtapa, Río Las Lajas and Poeciliopsis hnilickai from Río Hondo, Ixtapa and Río Cacao. Three new species of Gyrodactylus were found and are described herein based on morphological and genetic analysis. Attachment hooks were excised and partially digested with a proteolytic solution to remove tissue enclosing the haptoral armature. Measurements and pictures of the haptoral hard structures were taken and were compared with other Gyrodactylus species found on poeciliids and profundulids. The bodies from which haptoral hook were removed were stored individually in 95% ethanol at -20 °C for molecular analyses. Sequences of the Internal Transcribed Spacer region of rDNA were obtained for each species and were compared with 26 Gyrodactylus spp. The genetic divergence among species of Gyrodactylus was estimated using uncorrected "p" distances with the program MEGA. The haptoral hook of Gyrodactylus chiapaneco n. sp. are similar to G. poeciliae from Venezuela; those from Gyrodactylus guatopotei n. sp. resemble the sclerites of G. turnbulli from Singapore and G. pictae from Trinidad, and the haptoral hooks of Gyrodactylus tlaloci n. sp. are comparable to those of G. pseudobullatarudis and G. zapoteco from Mexico; most of these parasites were described from poeciliid fishes, except G. zapoteco which was recently described from Profundulus oxacae from Oxaca, Mexico. The sequences of the three new species were aligned with sequences of 26 other Gyrodactylus spp. Maximum likelihood and Bayesian inference analyses indicated that the three new taxa are members with well-supported lineages-the new taxa are the first species of Gyrodactylus to be described from Poeciliopsis hnilickai and Tlaloc labialis from Chiapas. Gyrodactylus chiapaneco n. sp., Gyrodactylus guatopotei n. sp. and Gyrodactylus tlaloci n. sp. are described based on morphological and molecular analyses. Two of the three new species of Gyrodactylus described here, and both roughly fall morphologically and molecularly into the group of parasites harbouring slender marginal hooks: G. chiapaneco n. sp. and G. tlaloci n. sp. both possess marginal sclerites with slim shafts and group phylogenetically with other gyrodactylids of similar marginal hook morphology. Gyrodactylus guatopotei n. sp. groups with gyrodactylids possessing marginal hooks with quite elongated shafts, most of which have been found infecting poeciliids in the Antilles (e.g. G. pictae and G. turnbulli). Poeciliid, profundulid and goodeid fishes are morphologically and ecologically similar and nowadays live in sympatry or close geographical distance in Mesoamerica.

New Species and Records of Anacanthorus (Monogenea: Dactylogyridae) Parasitizing Serrasalmid Fish (Characiformes) from Brazil, Including Molecular Data.

Species of the genus Anacanthorus Mizelle & Price, 1965 represent commonly known parasites of Neotropical Characiformes. Anacanthorus is one of the most specious Neotropical monogenean genus, currently comprising 73 nominal species. Fish were obtained from the Miranda River, Mato Grosso do Sul, from the Xingu River, Pará, from the Mogi Guaçu River, São Paulo and from the Upper Parana River, Paraná, Brazil. The monogeneans found were examined in a light microscope and partial sequences of the mitochondrial cytochrome c oxidase 1 gene were obtained for most species. Two new species of Anacanthorus were retrieved from Brazilian serrasalmids and are described herein. Anacanthorus paraxaniophallus n. sp. from Serrasalmus maculatus Kner has great similarity to A. xaniophallus Kritsky et al. (J Helminthol Soc Wash 59:25-51, 1992) by the general morphology of the copulatory complex, but it can be easily differentiated by a larger accessory piece with a slightly curved point, by having a basal flap in the male copulatory organ and by the morphology of hooks, with flattened thumb. Anacanthorus myleusi n. sp. from Myloplus schomburgkii (Jardine) is mainly distinguished by its unique copulatory complex, possessing an inverted J-shaped MCO with terminal flare and a hook-shaped accessory piece. Additionally, new host records are provided to A. lepyrophallus, geographical records are provided to four species of Anacanthorus (A. lepyrophallus, A. maltai, A. sciponophallus and A. thatcheri), which are being recorded in the Paraná River basin for the first time, and we also provide molecular data for six species of Anacanthorus.

The ecological niche of Echinococcus multilocularis in North America: understanding biotic and abiotic determinants of parasite distribution with new records in New Mexico and Maryland, United States

Understanding the factors shaping the niche of parasites and its expression over geographical space and through time continues to be a modern scientific challenge with the results of research in this area directly influencing both theoretical and applied biology. This is especially important for proactive management of zoonotic parasites such as Echinococcus multilocularis, the etiologic agent of alveolar echinococcosis. Echinococcus multilocularis has a Holarctic distribution; with its geographic range and prevalence increasing recently in areas of the western Palearctic, while its distribution dynamics are poorly understood in the Nearctic. In this paper, we use an ecological niche modeling (ENM) approach to: i) estimate the current spatial distribution of suitable conditions for the parasite in the Nearctic. ii) Evaluate the abiotic and biotic factors influencing the species distribution. iii) Assess the potential impact of climatic change on the distribution of this species in the Nearctic. Additionally, we report two new occurrence records of this parasite that significantly expands its known geographic range. We reviewed the occurrence records of E. multilocularis for the Nearctic. This was complemented by two new records of the species from Maryland and New Mexico identified using morphology and multivariate morphometrics of the rostellar hooks. From these data we created two ENMs using the software Maxent. The first ENM included climatic variables, while the second included the same abiotic data plus biotic information consisting of four host community-related data sets. We evaluated model performance and variable importance to explore the relation of these variables to the parasite niche. Finally, we projected the resulting niche model onto future climate change scenarios. We found that an important portion of the Nearctic has suitable conditions for E. multilocularis with adequate habitat in the West and East of the continent where the parasite has not been detected. We also found that the proposed biotic variables improve the model performance and provide unique information, while the most critical abiotic variable was related to the amount of solar radiation. Finally, under the future emission scenarios explored, the distribution of suitable habitat for the parasite is predicted to increase by 56 % to 76 %. We obtained a robust model that provides detail on the distribution of suitable areas for E. multilocularis, including areas that have not been explored for the presence of the parasite. The host community variables included in this study seem a promising way to include biotic data for ecological parasite niche modeling.

Four New Species of the Genus Pallisentis (Quadrigyridae, Van Cleave, 1920) from Freshwater Fish in Uttar Pradesh, India.

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.

Quadrigyrus torquatus cystacants Van Cleave, 1920 (Acanthocephala: Quadrigyridae) parasitizing species of Astyanax (Characiformes: Characidae) from southern Brazil

Abstract: 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.

A study of the parameters influencing mechanical properties and the fatigue performance of refill friction stir spot welded AlMgSc alloy

Friction spot welds of 1.6-mm-thick AlMgSc alloy were investigated in this work. A design of experiment method was used to evaluate the effect of process parameters on the shear static strength. The optimized condition of parameters was employed in the assessment of the fatigue behavior. The typical hook feature was minimized by restricting the tool penetration into only the upper sheet. As a consequence, shear strength was sensitive to the extension of the welded region rather than the hook morphology. The fatigue performance was affected by the multiple crack initiation sites that resulted from a complex stress state during the axial loading. Striations were observed in practically the entire crack propagation region, suggesting that unstable fatigue crack growth did not take place in this specific weld configuration.

Assesment of Echinococcus granulosus protoscolex viability after incubation in solution of sodium taurocholate

Background: Visualization of echiniococcal elements in cyst content is a routinely used diagnostic method, but it is not sufficient in evaluating the viability of protoscolices. In 1998. we started to add 0.2% sodium taurocholate to each sample to immitate conditions in the canine intestine. In the period from 1998. to 2014. 322 specimens were analyzed (178 female, 144 male, aged 6-81 years). The aim was to estimate the level of protoscolex viability based on motility and morphological characteristics to predict the outcome of the antiparasitic treatment. Methods & Materials: All evaluations were done by light microscopy. Native specimens were first evaluated for the presence of protoscolices. Further analysis estimated the level of protoscolex viability based on motility and morphological characteristics. No motility was observed in any sample after centrifugation. To re-create conditions in the canine intestine, 1 mL of each sample was incubated with 0.05 mL of 0.2% solution of sodium taurocholate in 1.0 mL of balanced Hank's buffer for 48 hours at 37 °C and it was analyzed after 24 and 48 hours. Two outcomes were assessed: a) presence of any protoscolex showing motility; b) proportion of observed protoscolices showing morphological signs of destruction (complete disintegration and free hooks, destruction of the tegmentum, loss off rostellar hook morphology, and loss of hooks) graded as “very good response” (>66%), “good response” (33%-66%), and “poor response” (<33%). Results: All patients received albendazole 7 to 28 days prior to PAIR procedure dosed 15 mg/kg/d in three divided doses with a fatty meal. “Very good response” was observed in 79 patients (24,5%), “good response” in 180 patients (55,9%) and “poor response” in 63 patients (19,56%). “Poor response” was an indication for another cycle of albendazole administration (28 days).The follow-up period for recurrence of hydatid disease for all patients were at least two years. Recurrences were observed in 18 patients (5.59%), all recruited from the “poor response” group. Conclusion: Described method appears superior to standard examination of protoscolices. Although protoscolices appeared immobile, after stimulation in sodium taurocholate some demonstrated motility which is of paramount importance for assessing viability and clinical outcome.