Pairs Of Hooks Research Articles

The forgotten origin of Acanthobothrium Blanchard, 1848 (Tetraphyllidea: Onchobothriidae)

The genus Acanthobothrium assembles a set of cosmopolitan onchobothriid tapeworms parasites of elasmobranchs. Despite its clear diagnostic features, which include a scolex with four bothridia each bearing three loculi and a pair of bipronged hooks, this genus is represented by species that possess a diversity of morphologies and host lineages (e.g. rays, skates, guitarfishes, and sharks; Campbell & Beveridge 2002; Zschoche et al. 2011). The wide distribution of this genus, its diverse morphology, and, perhaps most importantly, its lengthy and complex taxonomic history likely account for the fact that, to date, the absolute number of valid species, of potentially more than 200 nominal species, cannot be assigned to the genus with certainty. Clearly, a taxonomic revision of this group is overdue; a task that certainly will only be accomplished by collaborative efforts of cestodologists around the globe, given the widespread distribution of its species and the necessity of collecting new material to verify host identities and morphology in many cases. It is not our purpose here to provide such a revision. However, in order to get the basis for such a task, it is our intention to clarify the authorship, date of publication, type species, and type host of Acanthobothrium. To the best of our understanding, these have been mistakenly assigned throughout the taxonomic history of the genus.

Scanning electron microscopy on Gotocotyla acanthura (Monogenea, Gotocotylidae) from Pomatomus saltatrix (Ostheichthyes, Pomatomidae) in Brazil

Gotocotyla acanthura (Parona & Perugia, 1896) Meserve, 1938 collected from the gills of Pomatomus saltatrix from the coast of the state of Rio de Janeiro state was analyzed using scanning electron microscopy (SEM). The study demonstrated the presence of a buccal cavity, a genital atrium on the ventral surface and a muscular structure on the dorsal surface at the level of the body constriction. An elongated haptor with 80 to 120 pedunculated clamps symmetrically distributed in two rows, with rib-like thickenings and a curved lappet bearing a pair of hooks at the posterior extremity of the body were also observed. The cirrus could be seen protruding from the genital atrium, armed with pectinate spines along its length and presenting up to eight pointed spines around the genital atrium.

Comparative study of the three attachment mechanisms of diplectanid monogeneans

One of the main characteristics of the monogenean family Diplectanidae Monticelli, 1903 is their complex haptor formed by 2 pairs of hooks, transversal bars, 14 peripheral marginal hooks, and accessory adhesive organ (lamellodisc or squamodisc) that can be present or absent. Sub-family Lamellodiscinae Oliver, 1969 presents one or two lamellodiscs, formed by several overlapped lamellar esclerites (lamellae) which are piled up. Species like Furnestina echeneis only have one large ventral lamellodisc. This organ function has been categorized in different ways (i.e. accessory adhesive organ, supplementary or compensating disc or sucker), although its real mode of operation and function is still unclear. Specimens of Lamellodiscus and F. echeneis were examined. The lamellodisc of F. echeneis, studied both in vivo and fixed, seems to work as a sucker: the separated lamellae revolve around the single smallest lamellodisc lamella like the slats of a hand-held fan and create a suction volume. Lamellodiscus spp. lamellae (except the basal one) slide in telescopic movement, exerting a posterior and ventral or dorsal force that tightens it to the secondary gill lamellae. This force is contrary to the pulling force of hooks. Opposite forces together with the attachment to two different secondary gill lamellae gives strong binding and stability. These observations were compared with previous knowledge about Diplectanum aequans of subfamily Diplectaninae Monticelli, 1903, whose squamodiscs are formed by numerous spines and presents a different attach strategy. D. aequans produces extensive and deep alterations in the gill epithelium surrounding the parasite. The different attachment mechanisms of the diplectanid species can explain the different degrees of damage that each species provoke, and the information provided in this work can be useful for anthelmintic treatment designs.

Functional ultrastructure of the hexacanth larvae in the bothriocephalidean cestode Eubothrium salvelini (Schrank, 1790) and its phylogenetic implications

Functional ultrastructure and its phylogenic implications in the bothriocephalid cestode Eubothrium salvelini (Schrank, 1790) are described and discussed. The infective hexacanth shows bilateral symmetry in cellular organization. The mature hexacanth is armed with three pairs of oncospheral hooks of a heterogeneous electron density. It is covered by a thin layer of the oncospheral tegument, possessing characteristic bubble-like processes at the surface. Within the infective hexacanth larva five cell types were distinguished: (1) a binucleated subtegumental cell; (2) the U-shaped, tetranucleated penetration gland; (3) two nerve cells; (4) three types of somatic cells represented by: i) myocytons of both somatic and hook musculature, ii) numerous degenerating micromeres with pycnotic nuclei and iii) a new oncospheral cell type, the interstitial cell, that has never been observed in any other hexacanth; and (5) large germinative cells with characteristic prominent nucleoli in their large spherical nuclei. Functions of all the cell types are described on the basis of the obtained ultrastructural characteristics and previously published reports. The mode of the penetration gland secretion is classified as apocrine. Flame cells have never been observed within the hexacanth of E. salvelini. The results of the present study, comparing the functional aspects of the ultrastructure of the hexacanths of E. salvelini with literature data on the oncospheres of other bothriocephallideans and diphyllobothriideans, suggest potential phylogenetic and evolutionary criteria for determining relationships among these groups of tapeworms.

Ultrastructural reconstruction of Taenia ovis oncospheres from serial sections

The cellular organisation of Taenia ovis oncospheres is interpreted from ultrathin serial sections and transmission electron microscopy following high pressure freezing and freeze-substitution. The surface of a hatched, non-activated T. ovis oncosphere is covered by an oncospheral membrane below which is the tegument bearing microvilli. The basal lamina of the tegument is underlain by broad bands of peripheral somatic musculature. Three pairs of hooks and associated muscles are present in the somatophoric third of the oncosphere. Approximately 19 cells of seven different types were identified which include: (i) a quadri-nucleated syncytium of penetration gland type 1 containing two lateral pairs of cell bodies interconnected by narrow cytoplasmic bridges (PG1); (ii) a quadri-nucleated syncytium of penetration gland type 2 (PG2); (iii) a single-nucleated median mesophoric gland cell; (iv) 10 somatic cells; (v) two germinative cells; (vi) two nerve cells; and (vii) a pair of median somatophoric cells. This study provides a clear understanding of the morphology of T. ovis oncospheres and forms the basis for further investigations into the biology of taeniid oncospheres.

Open complementary split ring resonators: Physics, modelling, and analysis

This article is focused on the physics and analysis of a new type of planar resonant particles: the open complementary split ring resonators (OCSRRs). These resonators are the complementary counterpart of the open split ring resonators (OSRRs), previously presented by some of the authors, and consist on a pair of concentric hooks etched on a metal layer in opposite orientation. Like OSRRs, OCSRRs are open resonators that can be excited by means of a voltage or current source. An accurate circuit model of the particle is proposed and experimentally validated by exciting the particle by means of a coplanar waveguide transmission line. It will be also shown that OCSRRs exhibit higher order resonance frequencies, which can be selectively suppressed by introducing additional elements, as derived from a simple analysis based on mode parity. Because of the small electrical size of OCSRRs, such particles are useful for the synthesis of planar metamaterials and microwave components. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1520–1526, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25282

A New Gyrodactylid (Monogenea) Genus on Gray Bichir, Polypterus senegalus (Polypteridae) from Senegal (West Africa)

Diplogyrodactylus martini n. g. et sp., a viviparous monogenean, is described from the gills of gray bichir Polypterus senegalus Cuvier, 1829, in Senegal. This new genus can be readily distinguished from the other described viviparous genera based on the morphology of the attachment apparatus. The haptor is equipped with a pair of centrally positioned hamuli, a simple ventral bar without membrane and 8 pairs of marginal hooks of 2 types, 5 pairs of hooks with well-defined large falculate sickles, and 3 pairs of smaller hooks with well-articulated sickles. The new genus is unique in having a teardrop-shaped muscular tubular male copulatory organ which lacks spines. A partial sequence of the internal transcribed spacer (ITS rDNA) was obtained from 4 specimens of D. martini. The relationship among D. martini and other genera of the Gyrodactylidae is discussed based on the similarities of the attachment apparatus.

Open Complementary Split Ring Resonators (OCSRRs) and Their Application to Wideband CPW Band Pass Filters

In this letter, open complementary split ring resonators (OCSRRs) are introduced for the first time. Such resonators are the dual counterparts of the open split ring resonators (OSRRs), introduced in 2004 by some of the authors, and consist on a pair of concentric hooks etched on a metal layer in opposite orientation. It is shown in the letter that OCSRRs can be modeled by means of an LC parallel resonant tank and that this particle roughly exhibits half the resonance frequency of the complementary split ring resonator (CSRR), hence being electrically very small. The interest of these resonators is illustrated through their application to a wideband coplanar waveguide band pass filter.

Consensus Decision Making by Fish

Decisions reached through consensus are often more accurate, because they efficiently utilize the diverse information possessed by group members [1-3]. A trust in consensus decision making underlies many of our democratic political and judicial institutions [4], as well as the design of web tools such as Google, Wikipedia, and prediction markets [5, 6]. In theory, consensus for the option favored by the majority of group members will lead to improved decision-making accuracy as group size increases [2, 4]. Although group-living animals are known to utilize social information [7-10], little is known about whether or not decision accuracy increases with group size. In order to reach consensus, group members must be able to integrate the disparate information they possess. Positive feedback, resulting from copying others, can spread information quickly through the group, but it can also result in all individuals making the same, possibly incorrect, choice [8, 11, 12]. On the other hand, if individuals never copy each other, their decision making remains independent and they fail to benefit from information exchange [4]. Here, we show how small groups of sticklebacks (Gasterosteus aculeatus) reach consensus when choosing which of two replica fish to follow. As group size increases, the fish make more accurate decisions, becoming better at discriminating subtle phenotypic differences of the replicas. A simple quorum rule proves sufficient to explain our observations, suggesting that animals can make accurate decisions without the need for complicated comparison of the information they possess. Furthermore, although submission to peers can lead to occasional cascades of incorrect decisions, these can be explained as a byproduct of what is usually accurate consensus decision making.

New species of Diplectanum (Monogenoidea: Diplectanidae), and proposal of a new genus of the Dactylogyridae from the gills of gerreid fishes (Teleostei) from Mexico and Panama

While investigating the parasites of several marine fishes from the Western Atlantic, the Southern Gulf of Mexico and Central America (Panama), the following monogenoidean species from the gills of gerreid fishes (Gerreidae) were found: Diplec-tanum gatunense sp. n. (Diplectanidae) and Octouncuhaptor eugerrei gen. et sp. n. (Dactylogyridae) in Eugerres brasilianus (Cuvier) from Gatun Lake in the Panama Canal Watershed, and Diplectanum mexicanum sp. n. in Diapterus rhombeus (Cuvier) from the coast of Campeche State, Mexico. New diplectanid species are distinguished from other species of the genus by the general morphology of the copulatory complex and by the shape of the anchors and bars on the haptor. Octouncuhaptor gen. n. is proposed for its new species having slightly overlapping gonads (testis posterodorsal to the ovary), a dextrolateral vaginal aperture, a copulatory complex consisting of a coiled male copulatory organ with counterclockwise rings with the base articulated to the accessory piece, 8 pairs of hooks and the absence of anchors and bars on haptor. Our analysis of morphological features of Diplectanum species on gerreids evidences that these parasites more closely resemble each other than the known species from sciaenids suggesting that split between gerreids and sciaenids resulted in parasite speciation.

A new species of Sciadicleithrum (Monogenea: Ancyrocephalinae), gill parasite of Geophagus brasiliensis (Quoy & Gaimard) (Teleostei: Cichlidae) from reservoirs in the State of Parana Brazil

Sciadicleithrum frequens n. sp. is described from the gills of the acará, Geophagus brasiliensis (Cichlidae), from nine reservoirs in the State of Paraná, Brazil. The new species differs from the others members of Sciadicleithrum in the following features: dorsal anchors more than twice as long as the ventral anchors and hook pair 5 reduced in size. Sciadicleithrum frequens n. sp. is similar to species of this parasite genus from South America by having the male copulatory organ comprising less than 2 rings, and to species of Sciadicleithrum from Central America and southeast Mexico by the presence of longitudinal lateral grooves on the shafts and points of the ventral and dorsal anchors. This new species is the first species of Sciadicleithrum in South America with longitudinal lateral grooves on shafts and point of the ventral and dorsal anchors. It is the first dactylogyrid described from G. brasiliensis, and it is the first species of Sciadicleithrum described from Southern Brazil.

New morphological data on the acanthocephalan Hypoechinorhynchus magellanicus Szidat, 1950 (Palaeacanthocephala: Arhythmacanthidae)

Hypoechinorhynchus magellanicus Szidat, 1950 (Acanthocephala: Arhythmacanthidae) is redescribed based on specimens collected from a sub-Antarctic notothenioid fish, Champsocephalus esox (Günther). The host was caught in the Beagle Channel (Magellanic sub-region). H. magellanicus has a trunk with an antero-dorsal curvature, a spherical proboscis, spines on the anterior region of the trunk, narrow lemnisci which are considerably longer than the proboscis receptacle, six cement glands and a single vaginal sphincter. The proboscis is armed with 40 hooks, including 15 large hooks with roots and 25 rootless basal spines. The large hooks are arranged in 10 alternate rows of one and two hooks. Each single large hook is followed by two spines, and pairs of large hooks are followed by single spines. Ten single spines are also present at the base of the proboscis between the rows. The eggs have polar prolongations of the middle envelope.

Neotropical Monogenoidea. 52. Diechodactylus joaberi n. g., n. sp. from the banded knifefish Gymnotus carapo (Gymnotiformes: Gymnotidae) in southeastern Brazil

Diechodactylus joaberi n. g., n. sp. is described from the body surface of the banded knifefish Gymnotus carapo L. (Gymnotiformes: Gymnotidae) from southeastern Brazil. The new genus is proposed to accommodate species with five pairs of hooks in anterior bilateral clusters on the haptor, three pairs of hooks in a single cluster on the posterior margin of the haptor, sclerites R1 associated with the superficial bar, and confluent intestinal caeca. The presence of five pairs of hooks in two bilateral clusters anterior in the haptor permits the differentiation of species of Diechodactylus from species of all known genera of the Gyrodactylidae. The genus is likely a member of a clade of the Gyrodactylidae comprising genera with a similar hook distribution.

A Monogenoid from the Gills of Freshwater Garfish, Xenentodon cancila (Teleostei: Beloniformes: Belonidae) in India, with Proposal of Xenentocleidus n. g. (Monogenoidea: Dactylogyridae)

Xenentocleidus n. g. (Monogenoidea: Dactylogyridae) is proposed for Xenentocleidus xenentodoni (Jain, 1961) n. comb. (jr syn. Urocleidus xenentodoni Jain, 1961) collected from the gills of a freshwater garfish, Xenentodon cancila (Hamilton, 1822), in the River Gomti and Sai, Lucknow, Uttar Pradesh, India. The new genus is characterized by species with a dextroventral vagina with distally lightly sclerotized funnel-shaped vestibule and proximally highly sclerotized tube, a coiled copulatory tube with counterclockwise ring(s), a grooved, sheathlike accessory piece, rod-shaped haptoral bars, and a ventrally striated tegument at the region of copulatory complex. Xenentocleidus appear to be a sister group of Sclerocleidoides Agarwal, Yadav and Kritsky, 2001 on the basis of the following: a coiled male copulatory tube with counterclockwise coil(s), a ventral vaginal pore, and a subhexagonal haptor, armed with dorsal and ventral anchor/bar complexes, and 7 pairs of hooks.

A revision of Megalonchos Baer & Euzet, 1962 (Tetraphyllidea: Onchobothriidae), with the description of two new species and transfer of two species to Biloculuncus Nasin, Caira & Euzet, 1997

The onchobothriid tapeworm genus Megalonchos Baer & Euzet, 1962 is revised and the generic diagnosis amended based on the examination of some of Southwell's material of M. mandleyi (Southwell, 1927) Baer & Euzet, 1962, the type-specimens of M. dubius Prudhoe, 1969 and M. musteli Prudhoe, 1969, and material of two new species, M. sumansinghai n. sp. and M. shawae n. sp., collected from the snaggletooth shark Hemipristis elongatus off northern Australia. Based on their possession of two pairs of uni-pronged hooks (rather than one pair of bi-pronged hooks) and possession of, rather than lack of, post-vaginal testes, M. dubius and M. musteli are transferred to Biloculuncus Nasin, Caira & Euzet, 1997 as B. dubius (Prudhoe, 1969) n. comb. and B. musteli (Prudhoe, 1969) n. comb. Both new species of Megalonchos differ from M. mandleyi in their possession of conspicuously smaller hooks and shorter cephalic peduncles. The new species are readily distinguished from one another in that, whereas the pores of the axial prongs of the medial and lateral hooks are located well anterior to the middle of the prong in M. sumansinghai n. sp., they are well posterior to the middle of the prongs in M. shawae n. sp. In addition, the base of the lateral hook is longer relative to that of the medial hook in the latter species than it is in the former species. The proglottid anatomy of valid species of Megalonchos is described for the first time, and the lack of post-vaginal testes is confirmed for the genus. In addition, members of this genus appear to be characterised by a sacciform uterus that extends only to the level of the cirrus-sac and an ovary that is H-shaped in frontal view and bilobed in cross-section. Species of Megalonchos have now been reported from two of the eight known species of hemigaleid sharks.

New observations on the palaeoscolecid worm Tylotites petiolaris from the Cambrian Chengjiang Lagerstätte, south China

The Lower Cambrian Chengjiang Lagerstätte provides a remarkable window to enable investigation of the early diversification of introvert worms. Tylotites petiolaris Luo and Hu, 1999 is a very rare animal of the fauna originally regarded as a kind of lobopodian based on an incomplete specimen, but its affinities to recent phyla are still controversial. New materials of the taxon collected in recent years confirm that it is most closely related to the palaeoscolecidians with which it shares features such as a proboscis consisting of a slightly swollen introvert bearing many scalids, a collar (buccal cone) and a spinose pharynx. Both possess a smooth neck as a median zone between the introvert and the trunk, a pair of terminal hooks and a trunk bearing transverse ridges intercalated with furrows. Therefore, a new order Cricocosmida of the class Palaeoscolecida is erected herein based on these shared characters. The trunk spines of T. petiolaris are somewhat dorsoventrally differentiated indicating an epifaunal life on the sea floor. Numerous fine transverse wrinkles possibly beneath the uppermost cuticle of the ventral trunk of the animal are tentatively interpreted as the circular muscles, a feature crucial to understanding the problematic systematic position of the palaeoscolecidians.

Heterochromatin Protein 2 Interacts with Nap-1 and NURF: A Link between Heterochromatin-Induced Gene Silencing and the Chromatin Remodeling Machinery in Drosophila

Heterochromatin protein 2 (HP2) is a nonhistone chromosomal protein from Drosophila melanogaster that binds to heterochromatin protein 1 (HP1) and has been implicated in heterochromatin-induced gene silencing. Heretofore, HP1 has been the only known binding partner of HP2, a large protein devoid of sequence motifs other than a pair of AT hooks. In an effort to identify proteins that interact with HP2 and assign functions to its various domains, nuclear proteins were fractionated under nondenaturing conditions. On separation of nuclear proteins, nucleosome assembly protein 1 (Nap-1) has an overlapping elution profile with HP2 (assayed by Western blot) and has been identified by mass spectrometry in fractions with HP2. Upon probing fractions in which HP2 and Nap-1 are both present, we find that the nucleosome remodeling factor (NURF), an ISWI-dependent chromatin remodeling complex, is also present. Results from coimmunoprecipitation experiments suggest that HP2 interacts with Nap-1 as well as with NURF; NURF appears to interact directly with both HP2 and Nap-1. Three distinct domains within HP2 mediate the interaction with NURF, allowing us to assign NURF binding domains in addition to the AT hooks and HP1 binding domains already mapped in HP2. Mutations in Nap-1 are shown to suppress position effect variegation, suggesting that Nap-1 functions to help to assemble chromatin into a closed form, as does HP2. On the basis of these interactions, we speculate that HP2 may cooperate with these factors in the remodeling of chromatin for silencing.

CELLULAR ORGANIZATION OF THE ONCOSPHERE OF MOSGOVOYIA CTENOIDES (CESTODA: ANOPLOCEPHALIDAE)

The ultrastructure of the infective oncosphere of the cestode Mosgovoyia ctenoides (Anoplocephalidae) is described. The surface of the infective oncosphere is covered by a thin cytoplasmic layer of tegument connected by a narrow cytoplasmic process with the binucleate subtegumental cell, situated deeper in the body. Below the basal matrix of the cytoplasmic layer of the tegument are situated wide bands of the peripheral, somatic musculature responsible for body movements. The 3 pairs of hooks and their muscles form a complex hook muscle system, responsible for coordinated hook action. Five major types of cells have been distinguished: (1) a binucleate subtegumental cell, (2) a binucleate penetration gland, (3) 2 nerve cells, (4) numerous somatic cells, and (5) about 6 germinative cells. The approximate number of cells is 24 (26 nuclei, including 2 syncytial structures). The results of this study, when compared with other published reports from other cestode taxa, support previous hypotheses that the progressive reduction of oncosphere cells is an adaptive feature in cestode evolution.

A NEW DIPLECTANID (MONOGENEA) GENUS AND SPECIES FROM THE GILLS OF THE BLACK SNOOK, CENTROPOMUS NIGRESCENS (PERCIFORMES: CENTROPOMIDAE) OF THE PACIFIC COAST OF MEXICO

Cornutohaptor nigrescensi n. sp. (Diplectanidae) is described from the gills of the black snook, Centropomus nigrescens (Perciformes: Centropomidae) from the Pacific coast of Mexico. Cornutohaptor n. gen. is proposed for this new species and is characterized by possessing 2 intestinal ceca terminating blindly; a germarium looping right intestinal cecum; bilobed testis; 2 seminal vesicles; 7 pairs of hooks, each with protruding thumb; a grooved ventral bar and coiled male copulatory organ (MCO); an accessory piece comprising a "baglike structure" with an appendage; dorsal bars associated parallelly to body midline; and no adhesive accessory organs on the haptor. Cornutohaptor differs from all confamilial genera by including species with anchors with straight and deep root longest, hook pair 1 reduced in size, MCO with counterclockwise rings, and by the morphology of the accessory piece. Cornutohaptor nigrescensi most closely resembles species of Murraytrema Price, 1937, Lobotrema Tripathi, 1937, and Murraytrematoides Yamaguti, 1958, because of the absence of squamodiscs or lamellodiscs on the haptor and tegumental scales on the posterior portion of the body. Cornutohaptor differs from these genera in the position and number of haptoral bars (2 bars in Lobotrema spp., dorsal bars transversally associated in Murraytrema and Murraytrematoides spp.) and in having a coiled MCO (copulatory organ is a comparatively straight, poorly sclerotized tube in Murraytrematoides spp.). This is the first diplectanid described from a centropomid along the Pacific coast of Mexico.

The Occurrence of Nymphal Stage of Linguatula serrata in Water Buffaloes (Bubalus bubalis): Nymphal Morphometry and Lymph Node Pathology

The mesenteric lymph nodes (MLN) of buffaloes (n = 100) were examined for the presence of parasitic infection. The nymphal stage of Linguatula serrata was observed in two buffaloes. A single white-coloured nymph with transversely striated spines on a segmented body, two pairs of oral suckers and hooks was observed in the MLN. The morphometrics of the nymphs were studied. The affected lymph nodes were grossly enlarged with cyst and showed pathological lesions of fibroblastic reaction with a mild underlying inflammatory zone.