Argentophilic structures as a diagnostic criterion for the discrimination of species of the genus Gyrodactylus von Nordmann (Monogenea)

The mapping of argentophilic surface sensory structures (chaetotaxy) is a technique which has contributed to the taxonomy of larval digeneans. Four species of Gyrodactylus from four different hosts (Salmo salar, Gasterosteus aculeatus, Poecilia reticulata and Carassius auratus) were investigated using this technique in order to ascertain its usefulness in distinguishing species of this monogenean genus. A formula for the arrangement of the natural aggregations of sensilla similar to those prepared for cercariae is proposed. Although the greatest concentration of sensilla occur adjacent to the anterior extremity of the body, it is the region just posterior to the pharynx which most readily permits the discrimination of Gyrodactylus spp. based on the number and spatial configuration of these sensilla. Maps have been constructed to demonstrate these differences. It is concluded that chaetotaxy shows potential as a simple and reliable method of distinguishing species of this genus.     

Nominal species of the genus Gyrodactylus von Nordmann 1832 (Monogenea: Gyrodactylidae), with a list of principal host species

The total diversity of the monogenean genus Gyrodactylus is evaluated. There are 409 potentially valid species names within the genus, recorded from c. 400 host species. Five species have been placed within Fundulotrema and an additional 51 Gyrodactylus species names represent synonyms, nomina nuda or have been reassigned to other non-viviparous monogenean genera. While the majority of Gyrodactylus species (59%) are recorded from single hosts, some have a much broader broad range.     

Gyrodactylus medaka n. sp. (Monogenea: Gyrodactylidae) parasitic on wild and laboratory-reared medaka Oryzias latipes (Beloniformes: Adrianichthyidae) in Japan

Gyrodactylus medaka n. sp. (Monogenea: Gyrodactylidae) is described from the skin, fins, and gills of medaka Oryzias latipes (Beloniformes: Adrianichthyidae) from Japan. This new species was collected from wild medaka in Hiroshima, Aichi, Saga, and Kumamoto prefectures, and laboratory-reared medaka in Chiba and Aichi prefectures. The small marginal hook sickle (≤4?μm) and the length of the marginal hook of the new species are the diagnostic morphological characters differentiated from other gyrodactylids reported from Asia. The pairwise sequence divergences for the interspecific variation in ITS regions and the phylogenetic analysis suggest that the populations of G. medaka n. sp. may have a similar genetic variation as the medaka populations in Japan. Gyrodactylus medaka n. sp. and Dactylogyrus oryziasi (Monogenea: Dactylogyridae) can maintain their populations in laboratory aquaria using medaka as their hosts, and these monogeneans and medaka have the potential as experimental model animals for clarifying various aspects of their host-parasite relationships. In addition, we report the composition of modified ammonium picrate-glycerin (APG) and show it is advantageous for monogenean taxonomy.     

Cercarial chaetotaxy of Euparyphium albuferensis Esteban et al., 1997 (Trematoda: Echinostomatidae), with a review of some genera of the Echinostomatinae

Euparyphium albuferensis Esteban et al., 1997 (Trematoda: Echinostomatidae) is a parasite of the mollusc Gyraulus chinensis (D.) (Gastropoda: Planorbidae) and the mammals Rattus spp. in a nature park near Valencia, Spain. In the present work, the cercarial chaetotaxy is fully determined for specimens emitted by naturally infected G. chinensis. Of particular importance are the following sensillary arrangements: 5 CIV DL, 3 CIV CIV D at the dorso-cephalic level and 0 UV and 22–26 UD in the tail. Evidence is presented to the effect that these sensillary clusters are characteristic of the genus Euparyphium and allow an easy diagnosis, unlike in the case of the adult worms where there are sometimes few or no differences between Echinoparyphium and Echinostoma. A table synthesises the main data on the cercarial sensilla of Euparyphium spp. and the closely related genera Echinoparyphium, Echinostoma, Hypoderaeum, Moliniella, Neoacanthoparyphium, Paryphostomum and Isthmiophora. This shows clear variations in their respective numbers, from 3–5 in CIV DL, 2–4 in CIV D, 0–15 in UV and 19 to 57 in UD, according to the genus. These clusters appear adequate to identify, at the cercarial stage, the principal genera of the Echinostomatinae.     

First description of monogenean parasites in Lake Tanganyika: the cichlid Simochromis diagramma (Teleostei, Cichlidae) harbours a high diversity of Gyrodactylus species (Platyhelminthes, Monogenea)

Lake Tanganyika harbours the most diverse endemic cichlid fish assemblage of Africa, but its monogenean fish parasites have not been investigated. Here we report, for the first time, on the Gyrodactylus parasites in this hotspot of fish biodiversity. Haptor morphometrics and nuclear ribosomal DNA sequences revealed 3 new species on Zambian Simochromis diagramma: Gyrodactylus sturmbaueri n. sp., G. thysi n. sp. and G. zimbae n. sp. Their distinct morphology and strong genetic differentiation suggest that they belong to distant lineages within the genus Gyrodactylus, and phylogenetic reconstructions suggest affinities with other genera of gyrodactylids. Additional U-shaped haptoral plates in G. thysi n. sp. and a second large spine-like structure in the male copulatory organ of G. zimbae seem to represent new features for the genus. Such large diversity on a single host species can probably be explained by host-switching events during the course of evolution, in agreement with the generally accepted concept that ecological transfer is an important aspect of gyrodactylid speciation. Additional parasitological surveys on other host species, covering a broader phylogenetic and geographical range, should clarify the evolutionary history of Gyrodactylidae on cichlids in the African Great Lake and other parts of Africa.     

Cercarial chaetotaxy of Codonocephalus urniger (Rudolphi, 1819) (Trematoda: Diplostomidae)

The chaetotaxy of Codonocephalus urniger (Rudolphi, 1819) cercariae recovered from Lymnaea palustris in a brackish water lake in Bulgaria is described and figured. Comparisons with Diplostomum spathaceum (Rudolphi, 1819) and D. pseudospathaceum Niewiadomska, 1984 cercariae indicate a similar general pattern in the distribution of sensilla but with marked differences in their number and arrangement on the ventral sucker, tail stem and furcae. Data on the chaetotaxy of other diplostomid species are used to reveal the similarities and variations in some complexes within the members of Diplostomidae with known cercarial chaetotaxy.     

A new gyrodactylid species from Cobitis granoei (Rendahl) (Cobitidae) in central China

Gyrodactylus granoei n. sp. (Monogenea: Gyrodactylidae) is described from the fins and body surface of the spine loach, Cobitis granoei (Rendahl) (Cobitidae), in central China. It resembles a suite of species from cyprinid and cobitid fishes that have short, compact hamuli, a ventral bar with no obvious anterolateral projections, a linguiform posterior membrane, a male copulatory organ with small hooks in multiple rows, a simple cylindrical dorsal bar, and short marginal hooks, with an expanded sickle heel. Of these, the new species resembles most closely Gyrodactylus micracanthus Hukuda, 1940 from Misgurnus anguillicaudatus (Cantor) (Cobitidae), but it is identified by the length of the hamuli and the morphology of dorsal and ventral bars. When searched using BLAST, sequence data (829 bp) spanning the ITS1, 5.8s, and ITS2 region did not return an identical match; close similarity (82-88%) was found with sequenced members of the subgenus Gyrodactylus. It is suggested that the new species is part of a freshwater lineage that has radiated successfully among cyprinid fishes in North America, Europe, and Asia, and some of their predator and amphibian neighbors.     

Spermatozoon ultrastructure and phylogenetic relationships in the monogeneans (platyhelminthes)

Justine J.-L., Lambert A. and Mattei X. 1985. Spermatozoon ultrastructure and phylogenetic relationships in the monogeneans (Platyhelminthes). International Journal for Parasitology15: 601–608. New observations reported in this study together with bibliographical data allow comparisons of spermatozoon ultrastructure in 28 genera of monogeneans, belonging to 19 families. The authors propose to compare and classify monogenean spermatozoa using two simple ultrastructural characteristics: (a) the number of axonemes, 1 or 2, (b) the presence or absence of cortical microtubules. These traits make it possible to group monogenean spermatozoa in four patterns. Pattern 1 (2 axonemes plus microtubules) is characteristic of the polyopisthocotyleans (9 families). The three other patterns are found in the monopisthocotyleans. Pattern 2 (2 axonemes without microtubules) is found in the Capsalidae and Dionchidae, which seem closely related, and also in the Udonellidae, Gyrodactylidae and Euzetrema. Pattern 3 (1 axoneme plus 1 altered axoneme plus microtubules) is found in the Monocotylidae and Loimoidae. Pattern 4 (1 axoneme without microtubules) is found in the Amphibdellatidae, Ancyrocephalidae, Calceostomatidae and Diplectanidae. A phylogeny of the monogeneans is drawn from the data of comparative spermatology; this scheme coincides in many points with the phylogeny of Lambert (1980) which was based on the study of chaetotaxy and ciliated cells of the oncomiracidium.     

鱼类三代虫研究进展

三代虫是一类常见的鱼类体表寄生虫,广泛寄生于各种鱼类,其危害近年有加剧之势,对鱼类养殖业造成较大威胁。本文从三代虫的分类方法、种群动态和引起寄主免疫反应等方面综述了鱼类三代虫研究现状及发展趋势。     

Redescription of Folsomia loftyensis Womersley with notes on the sensillary arrangement of the genital segment in the genus (Collembola: Isotomidae)

Folsomia loftyensis Womersley is redescribed based on material from South Australia, Victoria and Queensland. The species exhibits, for the genus, an unusual sensillary pattern on the posterior abdominal segments. The arrangement and form of the five sensilla on the genital segment of most described species of Folsomia from the Palearctic are analysed and species divided into groups based on these characters. Several different lineages are detected.     

Phylogenetic study of nine species of freshwater monogeneans using secondary structure and motif prediction from India

The present study was performed to identify and validate monogenean species from different piscine hosts using molecular tools. Nine species of freshwater monogeneans were collected from gills and skin of freshwater fishes at Hastinapur, Meerut, India. After microscopic examination, molecular analysis was performed utilizing 28S gene marker. Phylogenetic analysis indicated the validation and systematic position of these nine different monogeneans belongs to the Dactylogyridae and Gyrodactylidae families. The findings also confirm that the 28S rDNA sequence is highly conserved and may prove to be useful in taxonomic studies of parasitic platyhelminthes. Besides this, the study is also supplemented by molecular morphometrics that is based on 28S secondary structure homologies of nine monogenean species. The data indicate that 28S motifs i.e., ≤ 50bp in size can also be considered a promising tool for monogenean species identification and their validation.     

On the ontogeny of the haptor and the evolution of the Monogenea

Data on the ontogeny of the posterior haptor of monogeneans were obtained from more than 150 publications and summarised. These data were plotted into diagrams showing evolutionary capacity levels based on the theory of a progressive evolution of marginal hooks, anchors and other attachment components of the posterior haptor in the Monogenea (Malmberg, 1986). 5 + 5 unhinged marginal hooks are assumed to be the most primitive monogenean haptoral condition. Thus the diagrams were founded on a 5 + 5 unhinged marginal hook evolutionary capacity level, and the evolutionary capacity levels of anchors and other haptoral attachement components were arranged according to haptoral ontogenetical sequences. In the final plotting diagram data on hosts, type of spermatozoa, oncomiracidial ciliation, sensilla pattern and protonephridial systems were also included. In this way a number of correlations were revealed. Thus, for example, the number of 5 + 5 marginal hooks correlates with the most primitive monogenean type of spermatozoon and with few sensillae, many ciliated cells and a simple protonephridial system in the oncomiracidium. On the basis of the reviewed data it is concluded that the ancient monogeneans with 5 + 5 unhinged marginal hooks were divided into two main lines, one retaining unhinged marginal hooks and the other evolving hinged marginal hooks. Both main lines have recent representatives at different marginal hook evolutionary capacity levels, i.e. monogeneans retaining a haptor with only marginal hooks. For the main line with hinged marginal hooks the name Articulon-choinea n. subclass is proposed. Members with 8 + 8 hinged marginal hooks only are here called Proanchorea n. superord. Monogeneans with unhinged marginal hooks only are here called Ananchorea n. superord. and three new families are erected for its recent members: Anonchohapteridae n. fam., Acolpentronidae n. fam. and Anacanthoridae n. fam. (with 7 + 7, 8 + 8 and 9 + 9 unhinged marginal hooks, respectively). Except for the families of Articulonchoinea (e.g. Acanthocotylidae, Gyrodactylidae, Tetraonchoididae) Bychowsky's (1957) division of the Monogenea into the Oligonchoinea and Polyonchoinea fits the proposed scheme, i.e. monogeneans with unhinged marginal hooks form one old group, the Oligonchoinea, which have 5 + 5 unhinged marginal hooks, and the other group form the Polyonchoinea, which (with the exception of the Hexabothriidae) has a greater number (7 + 7, 8 + 8 or 9 + 9) of unhinged marginal hooks. It is proposed that both these names, Oligonchoinea (sensu mihi) and Polyonchoinea (sensu mihi), will be retained on one side and Articulonchoinea placed on the other side, which reflects the early monogenean evolution. Except for the members of Ananchorea [Polyonchoinea], all members of the Oligonchoinea and Polyonchoinea have anchors, which imply that they are further evolved, i.e. have passed the 5 + 5 marginal hook evolutionary capacity level (Malmberg, 1986). There are two main types of anchors in the Monogenea: haptoral anchors, with anlages appearing in the haptor, and peduncular anchors, with anlages in the peduncle. There are two types of haptoral anchors: peripheral haptoral anchors, ontogenetically the oldest, and central haptoral anchors. Peduncular anchors, in turn, are ontogenetically younger than peripheral haptoral anchors. There may be two pairs of peduncular anchors: medial peduncular anchors, ontogentically the oldest, and lateral peduncular anchors. Only peduncular (not haptoral) anchors have anchor bars. Monogeneans with haptoral anchors are here called Mediohaptanchorea n. superord. and Laterohaptanchorea n. superord. or haptanchoreans. All oligonchoineans and the oldest polyonchoineans are haptanchoreans. Certain members of Calceostomatidae [Polyonchoinea] are the only monogeneans with both (peripheral) haptoral and peduncular anchors (one pair). These monogeneans are here called Mixanchorea n. superord. Polyonchoineans with peduncular anchors and unhinged marginal hooks are here called the Pedunculanchorea n. superord. The most primitive pedunculanchoreans have only one pair of peduncular anchors with an anchor bar, while the most advanced have both medial and lateral peduncular anchors; each pair having an anchor bar. Certain families of the Articulonchoinea, the Anchorea n. superord., also have peduncular anchors (parallel evolution): only one family, the Sundanonchidae n. fam., has both medial and lateral peduncular anchors, each anchor pair with an anchor bar. Evolutionary lines from different monogenean evolutionary capacity levels are discussed and a new system of classification for the Monogenea is proposed.In agreeing to publish this article, I recognise that its contents are controversial and contrary to generally accepted views on monogenean systematics and evolution. I have anticipated a reaction to the article by inviting senior workers in the field to comment upon it: their views will be reported in a future issue of this journal. EditorIn agreeing to publish this article, I recognise that its contents are controversial and contrary to generally accepted views on monogenean systematics and evolution. I have anticipated a reaction to the article by inviting senior workers in the field to comment upon it: their views will be reported in a future issue of this journal. Editor     

Gyrodactylus longipes n. sp. (Monogenea: Gyrodactylidae) from farmed gilthead seabream (Sparus aurata L.) from the Mediterranean

Gyrodactylus longipes n. sp. (Monogenea, Gyrodactylidae) is described from the gills of farmed juvenile gilthead seabream (Sparus aurata L.) from two sites located in Italy and Bosnia-Herzegovina and represents the second species of Gyrodactylus to be described from S. aurata. Gyrodactylus orecchiae Paladini, Cable, Fioravanti, Faria, Di Cave et Shinn, 2009 was the first gyrodactylid to be described from S. aurata, from populations cultured in Albania and Croatia. In the current study, G. longipes was found in a mixed infection with G. orecchiae on fish maintained in Latina Province, Italy, thus extending the reported distribution of the latter throughout the Mediterranean. The morphology of the opisthaptoral hard parts of G. longipes is compared to those of G. orecchiae, using light and scanning electron microscopy. Gyrodactylus longipes is characterised by having larger, elongated ventral bar processes and long, triangular-shaped toe region to their marginal hook sickles which, by comparison, are rhomboid in G. orecchiae. The marginal hook sickles of G. longipes are almost double the size of G. orecchiae which allows for their rapid discrimination from each other in mixed infections. A comparison of the DNA sequence of the ribosomal internal transcribed spacer 1 and 2 regions (ITS1 and ITS2) of G. longipes with the corresponding sequence from G. orecchiae and with those available in GenBank, supports the separate species status of G. longipes. Part of this study necessitated an overview of the existing Gyrodactylus fauna from Italy and Bosnia-Herzegovina; a summary from each country is provided here to assist future investigations.     

Gyrodactylus gvozdevi n. sp. (Gyrodactylidae: Monogenea) from Noemacheilus dorsalis (Kessler) in Kazakhstan

Gyrodactylus gvozdevi n. sp. (Gyrodactylidae: Monogenea) is described from the skin of the freshwater fish Noemacheilus dorsalis (Kessler) (Cobitidae: Cypriniformes) from Kazakhstan. This species is most closely related to G. pseudonemachili Ergens & Bykhovsky, 1967 in the shape and size of the anchors and both the ventral and dorsal bars, but can be distinguished from it by the shape and size of the hookproper of the marginal hooks.     

Gyrodactylus longidactylus n. sp., a monogenean from Pomatoschistus lozanoi (de Buen) (Gobiidae) from the North Sea

Gyrodactylus longidactylus n. sp., a gyrodactylid monogenean parasitising the gills of Pomatoschistus lozanoi (de Buen, 1923) in the North Sea is described. It is a species with rather small anchors which are only connected to a ventral bar which lacks a ventral bar membrane. The marginal hooks have long handles, which are always longer than the total length of the anchor. The pharynx has long pharyngeal processes. Measurements, drawings of the opisthaptoral hard parts, penis and pharynx, and SEM micrographs of this monogenean are presented. G. longidactylus n. sp. is the first monogenean species described from P. lozanoi.     

Parasite fauna of young landlocked salmon (Salmo salar m. Sebago girard) in the Pista River (the White Sea Basin)

A native population of landlocked salmon of the Pista River was investigated in 2000-2002. Adult salmon in Pista River has smallest size among other populations of landlocked salmon in Karelia. Data on the biology and parasite fauna of young salmon are presented. The presence of local salmon populations in lakes of the river system is apparently one of the mechanisms keeping the magnitude of population. The presence of Gyrodactylus salaris, a harmful parasite of the young landlocked salmon, is established in this territory for the first time. This monogenean species is believed to have been introduced into the Pista River via stocking from Finland.     

Gyrodactylus gemini n. sp. (Monogenea: Gyrodactylidae), a parasite of Semaprochilodus taeniurus (Steindachner) from the Venezuelan Amazon

Gyrodactylus gemini n. sp. (Monogenea, Gyrodactylidae) is described from the surface of the body and fins of the fish Semaprochilodus taeniurus (Steindachner) imported into Britain from the Venezuelan Amazon. The new species differs from other species of the genus, including those described from South and Central America, by having: (i) stout hamuli with straight shafts and diverging roots; (ii) marginal hooks with the sickle length larger than the width; (iii) a dorsal bar without a medial constriction; (iv) a rectangular ventral bar with short processes; (v) a triangular ventral bar membrane; and, most obviously, (vi) at least two generations which can develop two embryos simultaneously. This is the first known species of the genus Gyrodactylus from the Venezuelan Amazon and the first record of the subgenus Gyrodactylus (Gyrodactylus) from South America.