[Spermatogenesis in Acanthocephala. Flagellogenesis in an Acanthocephala: positioning and disorganization of the spermatic axoneme].
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Acanthocephala↗
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[Acanthocephala of birds; preliminary note; description of Arhythmorhynchus longicollis (Villot 1875) and revision of the genus Arhythmorhynchus Lühe 1911 (Acanthocephala)].
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Acanthocephala↗
Phylogenetic relationships of the Acanthocephala inferred from 18S ribosomal DNA sequences.
Phylogenetic relationships within the Acanthocephala have remained unresolved. Past systematic efforts have focused on creating classifications with little consideration of phylogenetic methods. The Acanthocephala are currently divided into three major taxonomic groups: Archiacanthocephala, Palaeacanthocephala, and Eoacanthocephala. These groups are characterized by structural features in addition to the taxonomy and habitat of hosts parasitized. In this study the phylogenetic relationships of 11 acanthocephalan species are examined with 18S rDNA sequences. Maximum parsimony, minimum evolution, and maximum likelihood methods are used to estimate phylogenetic relationships. Within the context of sampled taxa, all phylogenetic analyses are consistent with monophyly of the major taxonomic groups of the Acanthocephala, suggesting that the current higher order classification is natural. The molecular phylogeny is used to examine patterns of character evolution for various structural and ecological characteristics of the Acanthocephala. Arthropod intermediate host distributions, when mapped on the phylogeny, are consistent with monophyletic groups of acanthocephalans. Vertebrate definitive host distributions among the Acanthocephala display independent radiations into similar hosts. Levels of uncorrected sequence divergence among acanthocephalans are high; however, relative-rate tests indicate significant departure from rate uniformity among acanthocephalans, arthropods, and vertebrates. This precludes comparison of 18S divergence levels to assess the relative age of the Acanthocephala. However, other evidence suggests an ancient origin of the acanthocephalan-arthropod parasitic association.
Acanthocephala↗
Phylogenetic relationships of Acanthocephala based on analysis of 18S ribosomal RNA gene sequences.
Acanthocephala (thorny-headed worms) is a phylum of endoparasites of vertebrates and arthropods, included among the most phylogenetically basal tripoblastic pseudocoelomates. The phylum is divided into three classes: Archiacanthocephala, Palaeacanthocephala, and Eoacanthocephala. These classes are distinguished by morphological characters such as location of lacunar canals, persistence of ligament sacs in females, number and type of cement glands in males, number and size of proboscis hooks, host taxonomy, and ecology. To understand better the phylogenetic relationships within Acanthocephala, and between Acanthocephala and Rotifera, we sequenced the nearly complete 18S rRNA genes of nine species from the three classes of Acanthocephala and four species of Rotifera from the classes Bdelloidea and Monogononta. Phylogenetic relationships were inferred by maximum-likelihood analyses of these new sequences and others previously determined. The analyses showed that Acanthocephala is the sister group to a clade including Eoacanthocephala and Palaeacanthocephala. Archiacanthocephala exhibited a slower rate of evolution at the nucleotide level, as evidenced by shorter branch lengths for the group. We found statistically significant support for the monophyly of Rotifera, represented in our analysis by species from the clade Eurotatoria, which includes the classes Bdelloidea and Monogononta. Eurotatoria also appears as the sister group to Acanthocephala.
Acanthocephala↗
Organisation of the praesoma of Paratenuisentis ambiguus (Van Cleave, 1921) (Acanthocephala: Eoacanthocephala), with special reference to the lateral sense organs and musculature.
The praesoma of the acanthocephalan parasite Paratenuisentis ambiguus was studied at the light and the electron microscope level, with special reference to the lateral sense organs and the musculature, in order to substantiate the basal pattern of the Acanthocephala and to analyse the phylogeny of the taxon. The study includes the first ultrastructural description of a lateral sense organ in the Acanthocephala. Two sensory support cell ducts extend from the binucleate pericaryon of the sensory support cell to the lateral sense organs. On their way to the lateral sense organs the ducts penetrate the receptacle and join the anterior ventral nerves. Each lateral sense organ consists of a conical termination of one of the sensory support cell ducts, in which the neuronal fibres and dendritic terminations of the equilateral anterior ventral nerve are embedded. An analysis of the available data of praesomal sense organs in Acanthocephala suggests that lateral and apical sense organs are absent in the basal pattern of the Acanthocephala. It is likely that two lateral sense organs, a binucleate sensory support cell with two ducts and two anterior ventral nerves evolved within the stem-line of some Palaeacanthocephala, all Eoacanthocephala and all Archiacanthocephala, whereas two apical sense organs, a quadrinucleate sensory support cell with four ducts and two apical sensory nerves presumably represent an autapomorphic character of the Archiacanthocephala. Furthermore, it can be derived from data in the literature and the present study that the praesomal hooks are totally covered by epidermis in the basal pattern of the Acanthocephala, whereas the ontogenetic loss of the epidermal covering can be regarded as an autapomorphy of the Archiacanthocephala.
Acanthocephala↗
Molecular evidence for Acanthocephala as a subtaxon of Rotifera.
Rotifers are free-living animals usually smaller than 1 mm that possess a characteristic wheel organ. Acanthocephalans (thorny-headed worms) are larger endoparasitic animals that use vertebrates and arthropods to complete their life cycle. The taxa Acanthocephala and Rotifera are considered separate phyla, often within the taxon Aschelminthes. We have reexamined the relationship between Rotifera and Acanthocephala using 18S rRNA gene sequences. Our results conclusively show that Acanthocephala is the sister group of the rotifer class Bdelloidea. Rotifera was nonmonophyletic in all molecular analyses, which supports the hypothesis that the Acanthocephala represent a taxon within the phylum Rotifera and not a separate phylum. These results agree with a previous cladistic study of morphological characters.
Acanthocephala↗
The helminth fauna of the common seal (Phoca vitulina vitulina, Linné, 1758) from the Wadden Sea in Lower Saxony. Part 1: Trematodes, cestodes and acanthocephala.
Between August 1988 and January 1989 110 common seals found dead along the coast of Lower Saxony were investigated for the occurrence of trematodes, cestodes and acanthocephala. Two fluke species, Cryptocotyle lingua Creplin, 1825 and Phagicola septentrionalis Van Den Broek, 1967, two tapeworm species Diphyllobothrium cordatum Leuckart, 1863 and Diphyllobothrium elegans Krabbe, 1865, and the acanthocephala species Corynosoma strumosum Rudolphi, 1802 were found. Phagicola septentrionalis and the cestodes were always found together with Cryptocotyle lingua. The prevalence of Phagicola septentrionalis, the diphyllobothriids and the acanthocephala increased with increasing age of the pinniped host. The worm counts of all species appeared to increase with increasing age of the host. The adult male seals were more often infested with Phagicola septentrionalis and cestodes than the female adults and the younger pinnipeds. There was no correlation between blubber thickness of the seals and parasitic infection. The prevalence of the diphyllobothriids and the intensity of the infection with acanthocephala were higher in seals found in the eastern part of the Wadden Sea.
Acanthocephala↗
Syncytial organization of acanthors of Polymorphus minutus (Palaeacanthocephala), Neoechinorhynchus rutili (Eoacanthocephala), and Moniliformis moniliformis (Archiacanthocephala) (Acanthocephala).
The fine structures of immature and of developed shelled acanthors of three species belonging to the three subgroups of the Acanthocephala were investigated. Acanthors are surrounded by four eggshells (embryonic envelopes) and are composed of three syncytia: a frontal syncytium, a central syncytium, and an epidermal syncytium. Neither a sense organ nor a nervous system has been found. The central syncytium shows a mass of condensed nuclei and 12 decondensed nuclei and gives rise to 10 anterior/posterior subepidermal myofibrillar systems and 2 oblique retractor muscles. Circular muscles are missing. A single decondensed nucleus can be assigned to each of the 12 muscular systems. The epidermal syncytium embeds the other two syncytia and forms the wrinkled epidermis, which shows an extracellular glycocalyx and intrasyncytial condensations. Prominent recurved hooks, which mark the anterior end of each acanthor, and body spines are intraepidermal differentiations. Partly branched tubular infoldings of the epidermal plasma membrane of the acanthor exist and represent precursors of the pore ducts typical of the adult epidermis. Autapomorphies in the ground pattern of the monophylum Acanthocephala are the four eggshells, the early development of three syncytia, the condensed nuclei in the central syncytium, and the differentiation of ten longitudinal muscle bands and two muscle retractors and of intraepidermal hooks and spines. The syncytial organization of the epidermis with intraepidermal skeletal condensations and infoldings of the apical plasma membrane are characteristics inherited from a stem species common to Acanthocephala, Seison, and Rotifera.
Acanthocephala↗
Lecithostaphylus retroflexus (Molin, 1859) (Zoogonidae) and Tergestia acanthocephala (Stossich, 1887) (Fellodistomidae) (Digenea) from the epipelagic teleost Belone belone (L.) in the western Mediterranean.
Numerous individuals of the poorly known species Lecithostaphylus retroflexus (Zoogonidae) and Tergestia acanthocephala (Fellodistomidae) have been recovered from the teleost fish Belone belone gracilis from off the Scandola Nature Reserve, Western Mediterranean. They are redescribed, incorporating previously undescribed features: for L. retroflexus, a post-oral ring, a bipartite seminal vesicle, the shape of the excretory vesicle, the subterminal excretory pore and the flask-shaped gland-cells associated with the distinctly pedunculate ventral sucker; and for T. acanthocephala, the intestinal bifurcation in the forebody, necessitating its return to the genus Tergestia from Theledera. Additionally, T. acanthocephala is compared with T. laticollis from various species of Trachurus from the same geographical area.
Animals↗
Ultrastructure of spermiogenesis and spermatozoon of Leptorhynchoides plagicephalus (Acanthocephala, Palaeacanthocephala), a parasite of the sturgeon Acipenser naccarii (Osteichthyes, Acipenseriformes).
This paper describes the ultrastructure of spermiogenesis and the spermatozoon of Leptorhynchoides plagicephalus, an acanthocephalan parasite of the sturgeon Acipenser naccarii, a species which is under the threat of extinction. At the beginning, spermiogenesis in L. plagicephalus is characterized by the presence of a single centriole in the early spermatid. This centriole generates a flagellum with a 9+0 pattern. Another ultrastructural feature observed during the spermiogenesis of L. plagicephalus is the condensation of chromatin to form an "intranuclear wall". The mature spermatozoon of L. plagicephalus presents a reversed anatomy, as observed in other species of the Acanthocephala. The spermatozoon is divided into two parts: an axoneme and a nucleocytoplasmic derivative. The pattern of spermiogenesis and the ultrastructural organization of the spermatozoon of L. plagicephalus are compared with information available on other acanthocephalan species. The appearance of an "intranuclear wall" observed during the present study represents the first record within the Acanthocephala and is unknown from other animal taxa.
Acanthocephala↗
Phylogenetic analysis based on 18S ribosomal RNA gene sequences supports the existence of class polyacanthocephala (acanthocephala).
Members of phylum Acanthocephala are parasites of vertebrates and arthropods and are distributed worldwide. The phylum has traditionally been divided into three classes, Archiacanthocephala, Palaeacanthocephala, and Eoacanthocephala; a fourth class, Polyacanthocephala, has been recently proposed. However, erection of this new class, based on morphological characters, has been controversial. We sequenced the near complete 18S rRNA gene of Polyacanthorhynchus caballeroi (Polyacanthocephala) and Rhadinorhynchus sp. (Palaeacanthocephala); these sequences were aligned with another 21 sequences of acanthocephalans representing the three widely recognized classes of the phylum and with 16 sequences from outgroup taxa. Phylogenetic relationships inferred by maximum-likelihood and maximum-parsimony analyses showed Archiacanthocephala as the most basal group within the phylum, whereas classes Polyacanthocephala + Eoacanthocephala formed a monophyletic clade, with Palaeacanthocephala as its sister group. These results are consistent with the view of Polyacanthocephala representing an independent class within Acanthocephala.
Acanthocephala↗
Interspecific interactions between Acanthocephala in the intestine of brown trout: are they more frequent in Ireland?
The aim of this paper was to test the hypothesis that when the 2 species of Acanthocephalan Pomphorhynchus laevis and Acanthocephalus clavula are found concurrently within the intestine of brown trout under field conditions, they have the potential to interact negatively. Evidence has shown that Acanthocephala are more likely to exhibit negative interactions with their own and other species, under both field and experimental conditions. Furthermore, the likelihood of these interactions is increased in Ireland because of the absence of certain definitive hosts and the fact that concurrent infections by two or more species of Acanthocephala are more commonly observed in fish. Data collected from wild and stocked brown trout and from 2 lakes provided an opportunity to compare the 2 potentially interacting helminth species in their fundamental and realized niche and several pieces of convincing evidence are provided here to support the hypothesis. A significant negative association between the numbers of each species found in individual fish was reported and this was consistent for both wild and stocked trout. Furthermore, an analysis of the proportions of low, moderate and high intensity infections in single and concurrent infections revealed a significant reduction in increasing intensities in concurrent infections compared to single infections. Finally, strikingly different patterns of niche inhabitation were observed, particularly for P. laevis in the presence of A. clavula in wild trout. Results from the niche width analysis also support the observations on average position in single and concurrent infections. The niche width of P. laevis when it co-occurred with A. clavula decreased markedly in high intensity infections compared to low intensity infections.
Acanthocephala↗
Phylogeny of the Acanthocephala based on morphological characters.
Only four previous studies of relationships among acanthocephalans have included cladistic analyses, and knowledge of the phylogeny of the group has not kept pace with that of other taxa. The purpose of this study is to provide a more comprehensive analysis of the phylogenetic relationships among members of the phylum Acanthocephala using morphological characters. The most appropriate outgroups are those that share a common early cell-cleavage pattern (polar placement of centrioles), such as the Rotifera, rather than the Priapulida (meridional placement of centrioles) to provide character polarity based on common ancestry rather than a general similarity likely due to convergence of body shapes. The phylogeny of 22 species of the Acanthocephala was evaluated based on 138 binary and multistate characters derived from comparative morphological and ontogenetic studies. Three assumptions of cement gland structure were tested: (i) the plesiomorphic type of cement glands in the Rotifera, as the sister group, is undetermined; (ii) non-syncytial cement glands are plesiomorphic; and (iii) syncytial cement glands are plesiomorphic. The results were used to test an early move of Tegorhynchus pectinarius to Koronacantha and to evaluate the relationship between Tegorhynchus and Illiosentis. Analysis of the data-set for each of these assumptions of cement gland structure produced the same single most parsimonious tree topology. Using Assumptions i and ii for the cement glands, the trees were the same length (length = 404 steps, CI = 0.545, CIX = 0.517, HI = 0.455, HIX = 0.483, RI = 0.670, RC = 0.365). Using Assumption iii, the tree was three steps longer (length = 408 steps, CI = 0.539, CIX = 0.512, HI = 0.461, HIX = 0.488, RI = 0.665, RC = 0.359). The tree indicates that the Palaeacanthocephala and Eoacanthocephala both are monophyletic and are sister taxa. The members of the Archiacanthocephala are basal to the other two clades, but do not themselves form a clade. The results provide strong support for the Palaeacanthocephala and the Eoacanthocephala and the hypothesis that the Eoacanthocephala is the most primitive group is not supported. Little support for the Archiacanthocephala as a monophyletic group was provided by the analysis. Support is provided for the recognition of Tegorhynchus and Illiosentis as distinct taxa, as well as the transfer of T. pectinarius to Koronacantha.
Acanthocephala↗
[Hosts of Acanthocephala. II--Definitive hosts. 1. Fishes].
From an attentive study of the largest number of available publications, we tried to establish the list of fish species harbouring fully mature Acanthocephala, i.e. females with completely developed eggs. This character is the sole on which we are allowed to assure that this fish is truly a definitive host for the parasite. This very preliminary work shows that acanthocephalan specificity for the definitive host is narrower than it was generally said. If few so called "primitive" Acanthocephala are indeed parasitic in "primitive" fishes, in the majority of cases the main factor for infestation is related to the trophic behaviour of the definitive host and do not depends on its phylogenic position.
Acanthocephala↗
Identification of Acanthocephala discovered in changran-pickles and myungran-pickles.
To identify acanthocephala found in 'Changran-pickles' and 'Myungran-pickles' each organ was measured in permanent slides. In the present report, the results obtained were as follows: 1. Morphology of male worms: Worms possessed 18-19 longitudinal rows, with 4 hooks per row, which became smaller towards the base of proboscis. Each worm contained two testis and six cement glands arranged linearly. Body 22.0 by 0.8-0.6 mm and 15.0 by 0.6-0.4 mm, proboscis 284.8 by 227.6 micro m and 524.9 by 151.4 micro m, proboscis sheath 1570.7 by 72.7 micro m and 751.9 by 280.4 micro m, lemnisci length 2566.7 and 1085.6, testis 2202.9-1860.5 by 737.0-575.7 micro m and 1033.8-981.1 by 463.1-351.6 micro m, cement glands 940.2 by 441.2 micro m and 610.0 by 369.1 micro m. 2. Morphology of female worms: Worms possessed 14-18 longitudinal rows, with 6-10 hooks per row and become smaller toward the base of proboscis. Each worm contained an uterine bell and uterus in the posterior portion and the eggs filled the body cavity. Body, approximately 14.0 - 51.0 mm by 0.7-0.5 - 2.2-1.4 mm, proboscis 466.1-268.9 micro m by 259.9-252.0 micro m, proboscis sheath 1550.7-506.0 by 298.8-231.1 micro m, lemnisci length 1325.7-473.1 micro m, eggs approximately 112.4 by 28.5 micro m - 51.7 by 14.0 micro m. In this present study, the acanthocephala collected in 'Changran-pickles' and 'Myungran-pickles' were identified as Echinorhynchus gadi by morphological features.
Acanthocephala↗
Ultrastructural and genetic diversity studies of two Sclerocollum (Acanthocephala) species infecting Siganid and Lutianid fishes from the Red Sea, Egypt.
Little is known about the distribution of Acanthocephala in local waters. A survey was carried out on the commercially important herbivorous Siganid fish, Siganus rivulatus and S. luridus, as well as Lutianid fish Centropristisfilamentosus inhabiting the Red Sea to determine the prevalence of Acanthocephala parasites. One hundred and thirteen fish were examined. The infection rates of S. rivulatus and S. luridus with Sclerocollum rubrimaris Schmidt and Paperna 1978 (Rhadinorhynchidae: Gorgorhynchinae) were 59 % & 33%, respectively. Meanwhile, 59% of C. filamentosus were found infected by Sclerocollum sp. The abundance, host-parasite relationships and microhabitat of S. rubrimaris were investigated and discussed. SEM was the employed to investigate the differences between the two species of Sclerocollum. For accurate estimation of genetic diversity of these species, randomly amplified polymorphic DNA (RAPD) genomic fingerprinting was proposed, using four different random primers. SEM studies showed that the two examined species differ in the length of proboscis hooks, the number of longitudinal rows of hooks on proboscis, distance between the bases of hooks and in egg size. The trunk surface of Sclerocollum sp. had minute, scale-like spines that were arranged in oblique lines whereas the trunk surface of S. rubrimaris had small pores and sclerotised plates on its anterior portion. RAPD primers revealed 52 amplification products and species-specific markers were identified. The deduced phenogram comprised two main clusters each includes one of the examined Sclerocollum species. Results indicated that RAPD markers are useful for the assessment of genetic diversity between the investigated Sclerocollum species which concur with SEM outcome.
Acanthocephala↗
Performance of 18S rDNA helix E23 for phylogenetic relationships within and between the Rotifera-Acanthocephala clades.
The species diversity of the phylum Rotifera has been largely studied on the basis of morphological characters. However, cladistic relationships within this group are poorly resolved due to extensive homoplasy in morphological traits, substantial phenotypic plasticity and a poor fossil record. We undertook this study to determine if a phylogeny based on partial 18S rDNA, which included the helix E23 of 18S rDNA sequence, was concordant with established taxonomic relationships within the order Ploimida (class: Monogononta). We also estimated the level of polymorphism within clones and populations of Ploimida 'species'. Finally, we included the Cycliophora Symbion pandora as outgroup and the variable helix E23 region to examine the influence of their signal on the evolutionary relationships among Acanthocephala, Bdelloidea and Ploimida. Phylogenetic reconstruction was performed using maximum parsimony, neighbour joining and maximum likelihood methods. We found 1) that morphologically similar Ploimida 'species' show vastly different 18S E23 rDNA sequences; 2) inclusion of the helix E23 of 18S rDNA and its secondary structure analysis results in better resolution of family level relationships within the Ploimida; 3) an impact of Symbion pandora as an outgroup with inclusion of the helix E23 on the relationships between the Rotifera and the Acanthocephala; and 4) partial incongruence and differential substitution rate between conserved region and helix E23 region of the 18S rDNA gene depending on the taxomic group studied.
Animals↗
Comparative investigations of the morphology and chemical composition of the eggshells of Acanthocephala. III. Eoacanthocephala.
Eggshells of the eoacanthocephalans Neoechinorhynchus rutili (Neoechinorhynchidae) and Paratenuisentis ambiguus (Tenuisentidae) were investigated for their fine structure and their chemical composition. The acanthor larvae of P. ambiguus are surrounded by four eggshells (E1-E4) separated by electron-lucent interstices (G1-G4). This resembles the stratification of the eggshells of archiacanthocephalans and palaeacanthocephalans. However, an additional outer envelope (E0) exists in N. rutili. In mature eggs of this species, the broad interstice between E0 and E1 is densely packed with polysaccharides, but the other interstices also showed an intense Thiéry label. In both species, E2 along with its outer protuberances contains keratin, as does E2 in archiacanthocephalans and palaecanthocephalans, whereas E4 does not contain chitin, which contrasts with findings in the eggs of the two other classes of acanthocephalans. The results are discussed with respect to the classification of the Acanthocephala and to their transmission to the intermediate hosts.
Acanthocephala↗