Contribution to the knowledge of Gyrodactylus gurleyi Price, 1937 (Monogenea: Gyrodactylidae)

Gyrodactylus longoacuminatus Zitnan, 1964, forma minor sensu Ergens (1985) was identified as G. gurleyi Price, 1937. Morphological and metrical evaluations of the hard parts of opisthaptor of more than 200 specimens provided data on the variability of this parasite; Cyprinus carpio haematopterus represents its new host. Since the shape of the hard parts of opisthaptor of G. gurleyi is very similar to that of G. longoacuminatus, further detailed studies of the two species will be necessary, particularly of their reaction to the changes of environmental temperature.     

Gyrodactylus bohemicus sp. n. (Monogenea: Gyrodactylidae) from Oncorhynchus mykiss (Walbaum) and Salvelinus fontinalis (Mitchill) (Clupeiformes: Salmonidae) in Czechoslovakia.

Gyrodactylus bohemicus sp. n (Gyrodactylidae: Monogenea) is described from the fins, skin and gill filaments of Oncorhynchus mykiss (Walbaum) and Salvelinus fontinalis (Mitchill) (Clupeiformes: Salmonidae) from a trout farm in Czechoslovakia. G. bohemicus sp. n. is most closely related to G. thymalli Zitnan, 1960 and G. magnus Konovalov, 1967 in the shape of the anchors, the ventral and the dorsal bar, but can be distinguished from both these species by the shape of the marginal hook proper.     

A new species of the genus Gyrodactylus Nordmann, 1832 (Monogenea) from Gobio gobio (L.)

Gyrodactylus dykovae sp. n. (Monogenea: Gyrodactylidae) is described from the fins of the freshwater fish, Gobio gobio (L.) (Cyprinidae), from the Rokytná River near Moravsky Krumlov, Czechoslovakia. This species is most related to G. gobii Shulman, 1953 from which it differs by possessing more robust anchors with considerably larger shaft and by the morphology of the hook proper of marginal hooks.     

Chaetotaxy applied to Norwegian Gyrodactylus salaris Malmberg, 1957 (Monogenea) clades and related species from salmonids

Gyrodactylus salaris Malmberg, 1957 is a major pathogen of wild Salmo salar L. parr populations in Norway, and its delimitation from non-pathogenic species is important. The present study was undertaken to test the power of chaetotaxy to differentiate between three populations belonging to both the same and different clades (as stated by mtDNA) of G. salaris, in addition to three different species of gyrodactylids (G. salaris, G. thymalli and G. caledoniensis). The gyrodactylids were processed for chaetotaxy in situ and a maximum of 50 specimens per collection site were used to construct a generalised map over the sensilla. The sensilla were found in all populations to be symmetrically distributed around the median longitudinal axis, according to a formula of 7 dorsal (34 sensilla) and 8 ventral (44 sensilla) clusters on each side of the median line. The three Norwegian populations of G. salaris were found identical, as were the population of G. thymalli. The specimens of G. caledoniensis from Scotland, however, were found to differ from the Norwegian species G. salaris and G. thymalli by the position of one sensillum in two of the clusters. A comparison of the sensillum pattern of laboratory maintained G. salaris (River Lierelva) with results obtained ten years earlier, questions the temporal stability of the chaetotaxy pattern. The present results indicate that chaetotaxy can be used to discriminate between certain Gyrodactylus spp. but not generally.     

Histochemical demonstration of five enzymes' activities in Macrogyrodactylus clarii (Monogenea: Gyrodactylidae) from the catfish Clarias gariepinus

Histochemical techniques were applied to whole mounts, to study the distribution of the enzymes alkaline phosphatase, acid phosphatase, adenosine triphosphatase, 5'-nucleotidase and glucose-6-phosphatase in the organs and tissues of a viviparous monogenean, Macrogyrodactylus clarii Gussev, 1961, from the gills of the North African catfish Clarias gariepinus (Burchell) in Egypt. The following organs and tissues were studied: head region, anterior adhesive glands, mouth region, pharynx, intestine, testis, vesicula seminalis, male accessory gland, male accessory reservoir, copulatory organ, receptaculum seminis, egg-cell forming region, embryonic cells, excretory system, nerve cells, haptor, muscle fibres and subtegumental cell bodies (cytons). The enzymes showed marked differences in their activities among the studied organs and tissues. Alkaline phosphatase and acid phosphatase activities were detected in many organs and tissues, while the activities of adenosine triphosphatase, 5'-nucleotidase and glucose-6-phosphatase were restricted to a few organs. Although no positive reaction for any enzyme was observed in the anterior adhesive gland cells, a positive reaction for acid phosphatase was detected in the anterior adhesive areas. All enzymes showed marked activity in the digestive and excretory systems. The distribution of the enzymes in the tissues and organs of M clarii is compared with those of other monogeneans, including other gyrodactylids parasitizing the same host fish. Some possible functions of the enzymes are discussed.     

Homing of Gyrodactylus salaris and G. derjavini (Monogenea) on different hosts and response post-attachment

In natural European waters, the congeneric monogeneans Gyrodactylus derjavini Mikailov, 1975 and G. salaris Malmberg, 1957 are primarily found on brown trout Salmo trutta L. and Atlantic salmon Salmo salar L., respectively. Interestingly, rainbow trout, Oncorhynchus mykiss (Walbaum), originating from North America, is as susceptible as brown trout to G. derjavini. However, the mechanisms involved in this host specificity are poorly understood but may include behavioural, mechanical and chemical factors affecting parasite attraction, attachment, feeding, reproduction and host responses. In the present laboratory work, this question has been studied. Detached parasites (either G. derjavini or G. salaris) were offered a choice in small aquaria between fry of rainbow trout, Atlantic salmon and carp Cyprinus carpio L. Within 48 hours more than 90% of G. derjavini colonised rainbow trout and left salmon almost uninfected. Some parasites were found on carp. During the same time span, more than 60% of G. salaris attached to salmon, the rest infected rainbow trout and none were found on carp. Following attachment, the parasites need appropriate stimuli to initiate feeding and reproduction but even such a successful specific colonisation can be followed by a host response. Both humoral and cellular elements have been suggested to participate in these reactions but in the present work it was demonstrated by immunoblotting and immunocytochemistry that no antibodies in host mucus and host plasma bound to any parasite structures or epitopes.     

Neotropical Monogenoidea 37. Redescription of Gyrodactylus superbus (Szidat, 1973) comb. n. and description of two new species of Gyrodactylus (Gyrodactylidea: Gyrodactylidae) from Corydoras paleatus and C. ehrhardti (Teleostei: Siluriformes: Callichthyidae) of Southern Brazil

Two new species of Gyrodactylus (Gyrodactylidae) are described from Corydoras paleatus (Jenyns) and Corydoras ehrhardti Steindachner (Callichthyidae) of Rio Piraquara, Municipality of Piraquara, near Curitiba, Paraná, Brazil: Gyrodactylus anisopharynx sp. n. and Gyrodactylus samirae sp. n. These species are unique among the known Neotropical species of Gyrodactylus by the combination of several characters. Gyrodactylus anisopharynx is characterised by having hooks with point evenly curved, toe moderately pointed, round convex heel, straight sloping shelf, superficial bar with anterolateral projections and male copulatory organ armed with two rows of spinelets. Two variants of G. anisopharynx, of distinct pharynx size, are recognised: forma "large-pharynx" and forma "small-pharynx". Gyrodactylus samirae is characterised by having hook with straight shaft, short slightly recurved point, truncate toe, trapezoidal heel, shelf slightly concave, orthogonal to shaft; anchors with relatively short superficial root; superficial bar with extremities lightly expanded; and male copulatory organ armed with two rows of spinelets. Paragyrodactyloides superbus (Szidat, 1973) is redescribed and transferred to Gyrodactylus based on examination of type and new specimens. Features previously considered as diagnostic for the genus are misinterpretations or primitive characters for Gyrodactylus spp.     

Two new species of the genus Gyrodactylus (Monogenea) from the fins of Leuciscus cephalus (L.)

Gyrodactylus kearni sp. n. and G. lamberti sp. n. (Monogenea: Gyrodactylidae) are described from the fins of the freshwater fish, Leuciscus cephalus (L.) (Cyprinidae), from the Rokytná River and St?pánovicky Brook (basin of the River Danube), Czechoslovakia, G. kearni sp. n. is most related to G. leucisci Zitnan, 1964 in the shape and size of marginal hooks, but can be separated from it in the shape of anchors and ventral bar. G. lamberti sp. n. is most closely related to G. gobii Shulman, 1953 and G. truttae Glser, 1974 in the shape of the complex of anchors, but differs markedly from them in the shape of the hook proper of marginal hooks.     

Mormyrogyrodactylus gemini gen. et sp. n. (Monogenea: Gyrodactylidae), a new gyrodactylid from Marcusenius macrolepidotus (Mormyridae) from South Africa

Mormyrogyrodactylus gemini gen. et sp. n. (Gyrodactylidea: Gyrodactylidae), a viviparous monogenean is described from the skin and fins of Marcusenius macrolepidotus (Peters) from South Africa. This new genus is unique in having a large cup-shaped cirrus armed with one large needle-like spine and numerous small hair-like spinelets. A peduncular bar is present. The haptor is clearly demarcated from the body and situated on a small pedicle. The haptor has one pair of large anchors, a ventral bar complex, a small dorsal bar and 16 evenly spaced marginal hooks. The ventral bar complex consists of three parts: an inverted U-shaped piece with two semi-attached bars, each bar consisting of a base and an extension. An accessory inverted T-shaped sclerite is present on the posterior rim of the haptor. Mormyrogyrodactylus is the fifth genus of the Gyrodactylidae to be described from Africa.     

Experimental verification of the effect of physical condition of Gobio gobio (L.) on the growth rate of micropopulations of Gyrodactylus gobiensis Gl?ser, 1974 (Monogenea)

It has been verified experimentally that the growth rate of G. gobiensis micropopulations is markedly affected by the physical condition of the host (Gobio gobio). If the fish were weakened by 50% oxygen deficiency and lack of food, the number of parasites increased much more rapidly than on the fish also unfed but kept in water with 100% oxygen content. If the fish weakened by oxygen deficiency were intensively fed, the growth of the parasite micropopulations started to slow down after 4-5 days. When the feeding was stopped, the number of parasites increased again after 10-11 days. These time shifts seem to be associated with the physical condition of the host improved by feeding or worsened by starvation.     

The use of morphometric characters to discriminate specimens of laboratory-reared and wild populations of Gyrodactylus salaris and G. thymalli (Monogenea)

Gyrodactylus thymalli Zitnan, 1960 and G. salaris Malmberg, 1957 have an indistinguishable ribosomal internal transcribed spacer (ITS) DNA sequence, but exhibit surprisingly high levels of intra- and interspecific sequence variation of the mitochondrial cytochrome oxidase I (CO1) gene. To test whether different populations of these reportedly very similar species could be discriminated using morphometric methods, we examined the morphometry of four different populations representing different mitochondrial clades. Twenty five point-to-point measurements, including five new characters of the attachment hooks, were recorded from three Norwegian laboratory populations (G. salaris from the Rivers Lierelva and Rauma, and G. thymalli from the River Rena), and from one wild population of G. thymalli from the River Test, UK. The Norwegian populations were kept under identical environmental conditions to control for the influence of temperature on the haptoral attachment hooks. Data were subsequently subjected to univariate and linear stepwise discriminant analyses. The model generated by the linear stepwise discriminant analysis used 18 of the 25 original variables, the first two roots accounting for 96.6% of the total variation between specimens. The hamulus shaft length accounts for 66.7% of the overall correct classification efficiency. Based on morphometry, all specimens were assigned to the correct species. Apart from three specimens of G. salaris from the River Lierelva population which were misclassified as belonging to the G. salaris Rauma population, all specimens were assigned to the correct population. Thus, populations of Gyrodactylus identified by mtDNA can also be discriminated using morphometric landmark distances.     

Experimental verification of the effect of the form (scaly or scaleless) of carp host (C. carpio L.) on the growth rate of micropopulations of Gyrodactylus katharineri Malmberg, 1964 (Monogenea)

It was demonstrated that the growth rate of Gyrodactylus katharineri micropopulations parasitizing the fry of Cyprinus carpio L. was effected by water temperature and by the form of the fish host (scaly or scaleless). At lower water temperature (12 degrees C) the number of parasites increased in both host forms approximately at the same intensity. In warmer water (18 degrees C), the parasites reproduced intensively only on the scaly form of fish, whereas no parasites were found on the scaleless form some days after infection.     

Experimental verification of the effect of constant and changing water temperature on the micropopulation growth in Gyrodactylus gobiensis Gl?ser, 1974 (Monogenea) parasitizing gudgeon (Gobio gobio L.)

It has been verified under laboratory conditions that constant and changing water temperature markedly affects the micropopulation growth in Gyrodactylus gobiensis parasite on the body surface of gudgeons (Gobio gobio L.). At a water temperature of 12 degrees C, the number of gyrodactylids gradually increased up to the mean value of 63 specimens per host, which was reached on days 27-28 after experimental infection. At a constant temperature of 18 degrees C, the parasites completely disappeared from the bodies of infected fishes on days 15-20 p.i. A similar effect was produced by gradually increasing temperature from 12 to 18 degrees C, while the decrease in water temperature from 18 to 12 degrees C resulted in an increase in the parasite number.     

Annulotrematoides bryconi sp. n. (Monogenea: Dactylogyridae) parasitic on Brycon cephalus (Osteichthyes: Characidae) from Brazil

Annulotrematoides bryconi sp. n. is described and illustrated from specimens collected from gills of characiform fish, Brycon cephalus (Günther, 1869), in pisciculture ponds from Pirassununga, S?o Paulo, Brazil. Diagnostic characters of the new species are the tegument of trunk showing annulations, except on the cephalic regiona, and copulatory complex comprising sclerotized male copulatory organ coiled in 1 1/2 rings. This is the first record of monogeneans parasitic on the gills of B. cephalus.     

Description of Pseudorhabdosynochus seabassi sp. n. (Monogenea: Diplectanidae) from Lates calcarifer and revision of the phylogenetic position of Diplectanum grouperi (Monogenea: Diplectanidae) based on rDNA sequence data

Pseudorhabdosynochus seabassi sp. n. (Monogenea: Diplectanidae) from the gill filaments of Lates calcarifer Bloch, a marine teleost fish held in floating sea cages in Guangdong Province, China, is described based on morphological observations and molecular data. The shapes of the male copulatory organs (MCO) of Pseudorhabdosynochus spp. were the focus of this study. The typical proximal part of the MCO in most species of Pseudorhabdosynochus is reniform, heavily sclerotized, and divided into four chambers. However, the new species from L. calcarifer has a bulbous proximal region with four concentric layers of apparent muscular origin, instead of a reniform structure with four compartments. This organ is also different in Diplectanum grouperi Bu, Leong, Wong, Woo et Foo, 1999, being sclerotized, cup-shaped, wide proximally with four concentric muscular layers and tubular distally. The 3' terminal portion of the small subunit ribosomal RNA gene (ssrDNA) and the 5' terminal region (domains C1-D2) of the large subunit ribosomal RNA gene (lsrDNA) were used to reconstruct the phylogenetic relationships of P. seabassi and D. grouperi with related taxa utilizing maximum-parsimony and neighbour-joining methods. Phylogenetic analyses unequivocally placed D. grouperi amongst Pseudorhabdosynochus using either ssrDNA or lsrDNA data. All species of Pseudorhabdosynochus (including D. grouperi) used in this study clustered together, inferring monophyly. Based on molecular phylogenetic evidence, we propose that D. grouperi from Epinephelus coioides Hamilton be transferred to Pseudorhabdosynochus as P. grouperi comb. n.