Marginal Hooklets Research Articles

Polystoma luohetong n. sp. (Monogenea: Polystomatidae) from Rana chaochiaoensis Liu (Amphibia: Ranidae) in China.

Polystoma chaochiaoensis from the urinary bladder of the chaochiao frog Rana chaochiaoensis Liu was briefly described in a symposium abstract and presented at the Third Symposium on Parasitology of China in 1990. Types were not assigned and the original specimens collected are no longer available. The morphological description was incomplete and no illustrations were provided. We consider Polystoma chaochiaoensis a nomen nudum and provide a full description for the species and assign types. Based on morphological characteristics and molecular data of partial 18S rDNA sequences, we describe this species as Polystoma luohetong n. sp. Out of 578 frogs examined, 16 male and 38 female frogs were infected (prevalence 9.3%; mean intensity 1.02). Polystoma luohetong n. sp. is distinguished from all other Polystoma species by the presense of a prominent crest on the hamulus as well as by the shape and size of marginal hooklets and the intestinal arrangement. Furthermore, the phylogentic analysis based on the18S rRNA gene shows Polystoma luohetong n. sp. well nested within the Ploystoma clade and as a sister taxon to Polystoma integerrimum.

Light and transmission electron microscopy of the haptoral sclerites of the monogenean gill parasite Macrogyrodactylus clarii.

The present study represents the first detailed description of the haptoral sclerites of Macrogyrodactylus clarii Gussev 1961. Light microscopy reveals outgrowths of the hamuli roots; two lateral spine-like extensions of the hood-like accessory sclerites; a ridged, fan-shaped distal end of an accessory sclerite; and two thread-like accessory sclerites with biforked ends associated with the pointed hooked region of each hamulus. Transmission electron microscopy (TEM) reveals the presence of parallel tubules in the root of the hamuli and structural differences along the length of the hamulus including the root, shaft, and pointed hooked region. The root consists of two layers, the shaft four layers and pointed hooked region only one layer with dense outer serrations. Characteristic features of the hamulus root are the presence of longitudinally orientated parallel tubules in its central core and parallel electron-dense ridges in the outer layer of its middle region; features not observed in either the shaft or the pointed hooked region. Each hamulus blade of M. clarii is associated with haptoral gland cells producing electron-dense secretory bodies. The 16 marginal hooklets each consist of a blade (sickle) articulating with a handle at the guard region and a domus. TEM revealed structural differences between the handle, the blade at the articulation region, and the distal hooked region. The domus, a filamentous thread-like sclerite at the light microscope level, consists of two electron-dense, fibrous thickenings connected to each other by a cytoplasmic process. Each marginal hooklet is associated with a small cavity and a large reservoir of homogeneous particles and secretory bodies. The possible functions of these structures are discussed in relation to equivalent features in other monogeneans.

Pathological effects of Cichlidogyrus philander Douëllou, 1993 (Monogenea, Ancyrocephalidae) on the gills of Pseudocrenilabrus philander (Weber, 1897) (Cichlidae).

Histopathological changes of Cichlidogyrus philander Douëllou, 1993 on the gills of Pseudocrenilabrus philander (Weber, 1897) were studied using light and scanning electron microscopy. Observations revealed that C.philander attaches to its host by alternating the prohaptor (for temporary attachment or feeding) or haptor (using haptoral parts for firm and secured attachment). The sharp terminal ends of the anchors are inserted basally into the gill lamella, between two adjacent secondary gill lamellae and the marginal hooklets assist by superficially penetrating, holding and lifting epithelial tissue in the proximal region of the secondary gill lamella. The attachment of C.philander resulted in compression, rupturing of the interlamellar epithelium, change in the organization of epithelial cells in both primary and secondary gill lamella, displacement of the extracellular cartilaginous matrix, occasional rupturing of blood vessels and erythrocytes and some cells becoming ill-defined. At the site of attachment, the host response comprises of hyperplasia, increase in the number of mucous cells and infiltration with neutrophils. It was concluded that the effect of C.philander is mild in natural conditions.

Indopolystoma n. gen. (Monogenea, Polystomatidae) with the description of three new species and reassignment of eight known Polystoma species from Asian frogs (Anura, Rhacophoridae).

The polystomes (Monogenea, Polystomatidae) radiated across semi-aquatic tetrapods including all three amphibian orders, freshwater turtles and the hippopotamus. Prior to this study, phylogenetic analyses revealed that the most diverse and widespread genus, Polystoma, was not monophyletic; a lineage comprising four undescribed species from the bladder of Zhangixalus spp. (Rhacophoridae) in Asia occupied a deep phylogenetic position. Regarding vicariance biogeography and molecular dating, the origin of this lineage is correlated with the breakup of Gondwanaland in the Mesozoic period. Based on a Bayesian analysis of four concatenated genes (18S, 28S, COI and 12S) and morphological evidence, one new genus, Indopolystoma n. gen., and three new species, sampled in Japan and China, are described here: Indopolystoma viridi n. sp. from Z. viridis of Japan, Indopolystoma elongatum n. sp. from Z. arboreus of Japan, and Indopolystoma parvum n. sp. from Z. omeimontis of China. Indopolystoma is unique amongst polystome genera infecting anurans by possessing a small haptor relative to the body size, posteriormost marginal hooklet C1 much bigger than hooklets C2–C8 with conspicuous broad blade and guard and a pair of hamuli lacking a deep notch. Eight species of Asian Polystoma, all from rhacophorids, are transferred as Indopolystoma carvirostris (Fan, Li & He, 2008) n. comb., I. hakgalense (Crusz & Ching, 1975) n. comb., I. indicum (Diengdoh & Tandon, 1991) n. comb., I. leucomystax (Zhang & Long, 1987) n. comb., I. mutus (Meng, Song & Ding, 2010) n. comb., I. pingbianensis (Fan, Wang & Li, 2004) n. comb., I. rhacophori (Yamaguti, 1936) n. comb., and I. zuoi (Shen, Wang & Fan, 2013) n. comb.

First record of viviparity in polystomatid flatworms (Monogenea: Polystomatidae) with the description of two new species of Madapolystoma from the Madagascan anuran hosts Blommersia domerguei and Mantella expectata.

Two frog species, Blommersia domerguei and Mantella expectata, are reported as hosts for new species of Madapolystoma. Phylogenetic analyses and genetic divergences observed in the genus supported the distinction of two morphotypes infesting selectively each host species and morphological investigation combining marginal hooklet morphometrics, genital spine number and measurements further showed that polystomes from the two host species differed from each other and from all other known polystomes. Madapolystoma magnahami n. sp. and Madapolystoma isaloensis n. sp. are therefore described as two new species. Advanced in utero development was illustrated in both polystome species following the observation of well developed hamuli and two pairs of haptoral suckers in developing embryos. Inside some of these in utero embryos a F2 generation embryo was also observed. This is the first report of true viviparity among polystomatid flatworms.

Scanning and transmission electron microscopy of the histopathological impact of Macrogyrodactylus clarii (Monogenea: Gyrodactylidae) on the gills of catfish, Clarias gariepinus.

Scanning and transmission electron microscopy (TEM) were used to study the histopathological effects of the monogenean Macrogyrodactylus clarii Gussev, 1961 on the gills of the catfish Clarias gariepinus (Burchell). Suction generated during attachment created 'footprints' on host surfaces in which the host tissues were elevated above the general gill surface. 'Footprints' were bordered by four clefts caused by the muscular flaps on the anterior, lateral and posterior margins of the haptor. The hamuli points penetrate the gill tissue but no evidence was found for the insertion of the marginal hooklets. At the site of attachment, host cells adjacent to the lateral flaps often appeared compressed and widely spaced with large intercellular spaces. Desquamation of these surface epithelia was also apparent and some of the widely spaced epithelial cells had pseudopodium-like processes. Cells within the upper surface epithelial layer of the host were vacuolated and necrotic. Ruptured blood capillaries (blood spaces) in the secondary gill lamellae contained atypical compressed erythrocytes, agranular and granular leucocytes and evidence of haemorrhaging. Cells with fibrotic cytoplasm, putative phagocytes and host mucous cells were evidence of a host response at the site of parasite attachment. The possible role of these cells is discussed in relation to host resistance against infection.

A new polystomatid (Monogenea, Polystomatidae) from the mouth of the North American freshwater turtle Pseudemys nelsoni.

Based on material collected from Pseudemys nelsoni (Reptilia: Chelonia: Emydidae) during a parasite survey of the herpetofauna around Gainesville, Florida, USA, Polystomoides nelsoni sp. n. is described as a new polystome species. This parasite was found in the oral and pharyngeal region of the host. In a sample of nine Pseudemys nelsoni, three specimens were found to release polystome eggs. One turtle was euthanized and dissected and found to be infected in the oral region with 19 specimens belonging to an as-yet-unknown Polystomoides. This is only the fifth Polystomoides recorded from the Nearctic realm. This species is distinguished from known species by a combination of characteristics including marginal hooklet morphology, body length and haptor dimensions.

Eupolystoma namibiensis n. sp. (Monogenea: Polystomatidae) parasitic in Poyntonophrynus hoeschi (Ahl, 1934) of Namibia

Described species of the polystomatid flatworm genus Eupolystoma are only known from Africa and India. A survey conducted in January 1994 in Namibia revealed a previously unknown species from the urinary bladder of Hoesch's pygmy toad Poyntonophrynus hoeschi. Toads were screened from eight different localities within their known distribution. The toads found to be infected were from three localities, namely Mariental, Outjo and Kamanjab in Namibia. Morphologically, this polystome is distinguised from the other known species by a combination of characteristics including the size of the parasite, number of genital spines, and the size and shape of the marginal hooklets. Eupolystoma namibiensis n. sp. is the first polystome to be described from Namibia.http://zoobank.org/urn:lsid:zoobank.org:pub:4F61D4D1-1523-4A31-A08E-36B0F5C9FC87

Description of Acleotrema maculatus sp. nov. (Monogenea: Diplectanidae) infecting the spotted coral grouper Plectropomus maculatus (F:Serranidea) from the Red Sea and its histopathological impact

Acleotrema maculatus sp. nov. (Monogenea: Diplectanidae) was described from the gills of The spotted coral grouper Plectropomus maculatus (F:Serranidea, Forsskal, 1775). Fish were collected from boot landing sites and fishermen at different water locations along the Red Sea at Hurghada City, Egypt. The morphology and morphometric characterization of the recovered worms were described by means of light microscopy. Eight (53.3%) out 15 specimens of P. maculatus were infected. Most of the infected fish had very pale gills. Morphologically, the adult worm of A. maculatus sp. nov., possessed a body which was elongated, fusiform with a total length 0.86–0.90 (0.88 ± 0.02) mm, and a maximum width 0.09–0.13 (0.11 ± 0.02) mm at the level of ovary. Haptor, broad, differentiated from the rest of the body, measured 0.04–0.08 (0.06 ± 0.02) mm and provided with continuous rows of squamodiscs. Two pairs of lateral hamuli, three bars and 14 marginal hooklets were also observed. Lateral (dorsal) bars two, stout, dumbbell-shaped, measured 0.052–0.056 (0.054 ± 0.002) mm in length. Ventral bar slender, with transverse groove, measured 0.09–0.11 (0.10 ± 0.01) mm in length. Ventral hamuli measured 0.02–0.06 (0.04 ± 0.02) mm in total length with an outer root that was very long measured 0.016–0.02 (0.018 ± 0.002), stout, slightly notched at broad proximal end; inner root was conical and measured 0.013–0.017 (0.015 ± 0.002) mm, with shaft measured 0.025–0.029 (0.027 ± 0.002) mm and point length 0.007–0.009 (0.008 ± 0.002) mm. Dorsal hamuli measured 0.034–0.038 (0.036 ± 0.002) in total length; base large, stout, with only lateral rudiment of roots; blade and point were long and curved with shaft length measured 0.024–0.028 (0.026 ± 0.002) mm and 0.02–0.06 (0.04 ± 0.02) mm point length. The worm is hermaphrodite, male copulatory organ measured 0.058–0.062 (0.060 ± 0.002) mm in length with a sclerotized part composed of a well-defined, sclerotized anterior sheath. The new species was compared with those described previously from the same genus, it was shown that there were significant morphological and morphometric, which was a strong criteria for the placement these monogenean parasites as new species with new host and locality records in Egypt.

The morphology and attachment of Protopolystoma xenopodis (Monogenea: Polystomatidae) infecting the African clawed frog Xenopus laevis.

The African clawed frog Xenopus laevis (Anura: Pipidae) is host to more than 25 parasite genera encompassing most of the parasitic invertebrate groups. Protopolystoma xenopodis Price, 1943 (Monogenea: Polystomatidae) is one of two monogeneans infecting X. laevis. This study focussed on the external morphology of different developmental stages using scanning electron microscopy, histology and light microscopy. Eggs are released continuously and are washed out when the frog urinates. After successful development, an active swimming oncomiracidium leaves the egg capsule and locates a potential post-metamorphic clawed frog. The oncomiracidium migrates to the kidney where it attaches and starts to feed on blood. The parasite then migrates to the urinary bladder where it reaches maturity. Eggs are fusiform, about 300 μm long, with a smooth surface and are operculated. Oncomiracidia are elongated and cylindrical in shape, with an oval posterior cup-shaped haptor that bears a total of 20 sclerites; 16 marginal hooklets used for attachment to the kidney of the host and two pairs of hamulus primordia. Cilia from the 64 ciliated cells enable the oncomiracidium to swim for up to 24 h when the cilia subsequently curl up, become non-functional and are shed from the body. The tegument between the ciliated cells bears a series of sensory papillae. The body of the mature parasite is elongated and pyriform and possesses an opisthaptor armed with three pairs of suckers and two pairs of falciform hooks to ensure a firm grip on the flexible internal surface of the urinary bladder.

Functional dynamics observations of haptoral armature in Mizelleus indicus (Jain 1957) Pandey et al. 2003.

The negative effect of monogenea on piscine host may vary in the host species. Genus Mizelleus (Monogenea: Ancyrocephalidae) was reported for the first time from the freshwater shark, Wallago attu (Bl. and Schn.) at Lucknow by Jain (1957). Haptor or opisthohaptor of monogenea which is more or less discoid muscular structure situated posteriorly, is the chief adhesive organ. It is usually provided with anchors and marginal hooklets. Anchors, ventral transverse bar, together with the additional supporting dorsal bars (patches) are active elements of haptor while, marginal hooklets serve as secondary supportive participants, whereas, the dorsal transverse bar can be treated as an inactive element in the whole organ of attachment. Functional dynamics detail of haptoral armature is almost unattended. The anchors in case of M. indicus (Jain 1957) Pandey et al. (2003) are disposed one against the other and used to act like four lobed grapnel like a spreader. All components of haptoral armature contribute in one way or another in the process of functional process. Interestingly the worms do not follow the same pattern of sequences during their movements. Various elements and factors are involved in the process. The authors tried to pinpoint the changes in the activity of one major element i.e., dorsal anchor. The movement and change in position/orientation of various elements with reference to dorsal anchors were observed and summarized. Present paper is rare effort in unexplored aspect in monogenea biology.

Two new polystomes (Monogenea: Polystomatidae) from the eyes of North American freshwater turtles

Neopolystoma moleri n. sp. and Neopolystoma grossi n. sp. are described as new polystome species on the eyes of Apaloneferox and Pseudemys concinna floridana, respectively from Florida, USA. Eleven other polystome species are currently knownfrom chelonian hosts in the USA, but only Neopolystoma elizabethae and Neopolystoma fentoni were described from the eye.Ocular polystomes are characterized as having spindle-shaped eggs; an exceptionally firm grip on the host; as well as the abilityto stretch, which gives them the advantage of being stationary while extending to feed, reducing the risk of being dislodged.The two new species can be distinguished from known Neopolystoma species by a combination of characteristics including marginal hooklet morphology.

Polystoma nacialtuneli n. sp. (Monogenea: Polystomatidae) from the eastern spadefoot, Pelobates syriacus (Pelobatidae) in Turkey

Polystoma nacialtuneli n. sp. is described from the urinary bladder of the eastern spadefoot, Pelobates syriacus from Turkey. This is the fifth polystome species known from Turkey and the third species in Pelobates. We show that this new parasite species can be distinguished from other polystome species in the area by a combination of characteristics, including parasite size and the shape and size of the hamuli. Polystoma pelobatis from Pelobates cultripes has a pair of well-developed hamuli, while P. fuscus from Pe. fuscus characteristically has a pair of underdeveloped hamuli barely larger than the marginal hooklets. Polystoma nacialtuneli n. sp. has well-developed hamuli that vary significantly in shape. Phylogenetic relationships of P. nacialtuneli n. sp. within Polystoma, supplemented with molecular divergences estimated from internal transcribed spacer 1 (ITS1) sequences, indicate that they are well separated from their closest relatives, i.e. P. fuscus and P. pelobatis from Pe. fuscus and Pe. cultripes, respectively.

Ultrastructure of musculature of the marginal hooklets of Macrogyrodactylus congolensis, a monogenean skin parasite from the catfish Clarias gariepinus

AbstractThe musculature of the marginal hooklets of adult Macrogyrodactylus congolensis (Prudhoe, 1957) Yamaguti, 1963 has been studied. Each marginal hooklet of M. congolensis is associated with three pairs of muscles. The possible role of these muscles in the operation of the marginal hooklet is discussed. Transmission electron microscopy has been used for the first time to study the marginal hooklets of M. congolensis. The handle articulates with the blade in the region of the guard. Internally, the handle, the proximal region of the blade in the articulation region and the distal pointed region of the blade consist of three layers. Distal to the articulation region, the blade consists of four layers with differing electron densities. A cavity is associated with the distal region of the blade and the handle. A cyton containing secretory bodies of different sizes and shapes was found in association with each marginal hooklet. The possible function of these secretions is discussed.

Polystoma vernonin. sp. (Monogenea: Polystomatidae) from the sharp nosed grass frogPtychadena oxyrhynchus(Smith, 1849) in South Africa

Polystoma vernoni (Polystomatidae) is a new species in the urinary bladder of Ptychadena oxyrhynchus in KwaZulu-Natal province, South Africa. Ptychadena is a true African species and the 49 currently known species in Africa harbour 11 polystome parasites. Ptychadena oxyrhynchus has an extensive distribution through Africa and harbours Polystoma prudhoei in West Africa. This new parasite differs significantly from P. prudhoei. The new species is distinguished by its long body relative to its haptor length, its unique shape and its ratio of marginal hooklets. In a sample of 13 frogs, 53.8% were infected with up to 18 parasites per host (mean intensity 4.86).

Polystoma okomuensisn. sp. (Monogenea: Polystomatidae) from Boulenger's striped frog,Phlyctimantis boulengeri(Perret, 1986) in Nigeria

Polystoma okomuensis is described as a new species of the Polystomatidae parasitic in the urinary bladder of Boulenger's striped frog Phlyctimantis boulengeri in the Okomu National Park, Edo State, Nigeria. Although other African polystomes have been reported from Nigeria, this is the first to be described from the country and the first from Phlyctimantis. It is distinguished from other African Polystoma species by a combination of characters, including the body size, size and shape of the hamuli, size and shape of marginal hooklets and intestinal location. Phlyctimantis boulengeri was found to be infected in two of four seasonal lakes where specimens were caught with prevalences and mean intensities ranging from 14.3 to 22% and 1.0 to 1.5, respectively. Of the total number of 45 frogs examined, the prevalence was 15.6% and mean intensity 1.4.

Mode of attachment and histopathological effects of Macrogyrodactylus clarii, a monogenean gill parasite of the catfish Clarias gariepinus, with a report on host response

AbstractA detailed account is given about the mode of attachment and histopathological effects of Macrogyrodactylus clarii Gussev, 1961, a viviparous monogenean from the gills of the catfish Clarias gariepinus. Most parasites attach their haptors to the proximal region of the gill filament (primary gill lamellae), while few specimens were seen attached to the distal region. Attachment of the haptor was achieved mainly by the blade of the hamuli, but no evidence was found indicating the participation of marginal hooklets in the attachment. The hamuli of M. clarii penetrate into the interlamellar epithelium of the gill tissue. Some evidences were found to indicate that M. clarii may also utilize suction force during haptoral attachment. The pathological effects of M. clarii are manifested by breakdown of the coating epithelium, necrosis of the epithelial cells, vacuolations inside and outside the host cells, fusion of the gill lamellae, rupture of blood capillaries, infiltration of erythrocytes and degeneration and fibrosis of the interlamellar epithelium. The host response includes the appearance of lymphocytes, mucoid secretions and hyperplasia of the tissue at the site of attachment.

Overview of South African Dendromonocotyle (Monogenea : Monocotylidae), with descriptions of 2 new species from stingrays (Dasyatidae) kept in public aquaria

Two new species, Dendromonocotyle citrosa n. sp. off Dasyatis chrysonota (Smith) from Two Oceans Aquarium in Cape Town and off Himantura gerrardi (Gray) from uShaka Sea World in Durban and D. ukuthena n. sp. off H. gerrardi and H. uarnak (Forsskal) also from uShaka Sea World in Durban, are described. These can be distinguished from previously described Dendromonocotyle species by the morphology of the distal portion of the male copulatory organ and the proximal part of the vagina. Vaginal morphology is proposed as an important diagnostic character for species in the genus. Dendromonocotyle colorni Chisholm, Whittington & Kearn, 2001 which was originally recorded from H. uarnak in Israel, was discovered on H. uarnak sympatrically with D. ukuthena n. sp. and with D. citrosa n. sp. and D. ukuthena n. sp. off H. gerrardi. Minor differences in the number of papillary sclerites, the presence of septal tripartite sclerites and in the number of eyespots were seen between D. colorni collected from H. uarnak and H. gerrardi from uShaka Sea World and those originally described off H. uarnak from Israel. We demonstrate that the position of the marginal hooklets can be used to determine the orientation of the haptor of all representative Dendromonocotyle species with or without hamuli. We conclude that Dendromonocotyle species may not be as host-specific as previously believed and that minor differences in morphology are host or geographically induced.

Polystoma floridana n. sp. (Monogenea: Polystomatidae) a parasite in the green tree frog, Hyla cinerea (Schneider), of North America

Polystoma floridana is described as a new species of the Polystomatidae parasitic in the urinary bladder of Hyla cinerea in Gainesville, Florida, USA. This is the fifth polystome from an anuran host described from North America but only the third belonging to the genus Polystoma. Here we show that the parasite from H. cinerea is a separate species. It is distinguished from other American Polystoma species by a combination of characters including body size, haptor length, body rations, size and shape of hamuli and marginal hooklets. In a sample of 235 frogs, 13.6% were infected with up to four parasites per host (mean intensity 1.6).

Neuromusculature of Gyrodactylus rysavyi, a monogenean gill and skin parasite of the catfish Clarias gariepinus

Phalloidin fluorescence technique, enzyme cytochemistry and immunocytochemistry in conjunction with confocal scanning laser microscopy were used for the first time to describe the nervous and muscle systems of the viviparous monogenean parasite, Gyrodactylus rysavyi inhabiting the gills and skin of the Nile catfish Clarias gariepinus. The body wall muscles are composed of an outer layer of circular fibres, an intermediate layer of paired longitudinal fibres and an inner layer of well-spaced bands of diagonal fibres arranged in two crossed directions. The musculature of the pharynx, intestine, reproductive tract and the most prominent muscles of the haptor were also described. Two characteristic muscular pads were found lying in the anterior region of the haptor in close contact with the hamuli. To each one of these pads, a group of ventral extrinsic muscles was connected. The role of this ventral extrinsic muscle in the body movement was discussed. The mechanism operating the marginal hooklets was also discussed. The central nervous system (CNS) consists of paired cerebral ganglia from which three pairs of longitudinal ventral, lateral and dorsal nerve cords arise. The nerve cords are connected at intervals by many transverse connectives. The CNS is better developed ventrally than dorsally or laterally and it has the highest reactivity for all neuroactive substances examined. Both the central and the peripheral nervous system (PNS) are bilaterally symmetrical. Structural and functional correlates of the neuromusculature of the pharynx, haptor and reproductive tracts were explained. The results implicated acetylcholine, FMRFamide-related peptides (FaRPs) and serotonin in sensory and motor function. The results were compared with those of the monogeneans Macrogyrodactylus clarii and M. congolensis inhabiting the gills and skin respectively of the same host fish C. gariepinus.