Gyrodactylus malalai sp. nov. (Monogenea, Gyrodactylidae) from Nile tilapia, Oreochromis niloticus (L.) and Redbelly tilapia, Tilapia zillii (Gervais) (Teleostei, Cichlidae) in the Lake Turkana, Kenya

Gyrodactylus malalai sp. nov. is described from the fin surface of cichlid fishes Oreochromis niloticus (L.) and Tilapia zillii (Gervais) caught in Lake Turkana (Kenya). The new species morphologically resembles Gyrodactylus nyanzae Paperna, 1973, but can be readily distinguished by the shape of the marginal hook sickles and the size of its hamuli. The sequence data of rDNA spanning partial 18S, internal transcribe spacer 1 and 2 and the 5.8S gene is unique within GenBank. Genetically, as most similar Gyrodactylus ergensi Přikrylová, Matějusová, Musilová et Gelnar, 2009 was found (97.5%). Moreover, a specimen of G. cichlidarum from O. niloticus, and a specimen G. ergensi from Sarotherodon galilaeus (L.) were collected during sampling in Kenya. Likewise, additional sampling of O. niloticus from the Blue Nile in Sudan revealed the presence of the newly described species. These findings represent the first records of gyrodactylids in both African countries.

Ieredactylus rivuli gen. et sp. nov. (Monogenea, Gyrodactylidae) from Rivulus hartii (Cyprinodontiformes, Rivulidae) in Trinidad

A new genus and species of Gyrodactylidae, Ieredactylus rivuli gen. et sp. nov. (Platyhelminthes, Monogenea), is described from the skin of Hart’s Rivulus (Rivulus hartii Boulenger), a cyprinodontiform fish collected from streams of the Caroni and Oropouche drainages and the Pitch Lake in Trinidad (prevalence all localities: 16.7–94.6%; mean parasite intensity 1–9 parasites/fish; range 1–34) with the holotype originating from a tributary of the Aripo River. This viviparous monogenean is distinctive from other genera of Gyrodactylidae by its split ventral bar membrane, the shape of its male copulatory organ, the presence of two conical accessory pieces associated with the hamulus root and two differently shaped marginal hook sickles. Its unique rDNA sequence shows the closest ITS2 similarity (70%) to Gyrodactyloides andriaschewii Bychowsky et Poljansky, 1953. The presence of I. rivuli gen. et sp. nov. in the Pitch Lake indicates an adaptation to extreme environmental conditions such as high temperatures and hydrocarbons and adverse pH. Guppies may potentially serve as temporary hosts. The parasite displays distinct behaviours, including a characteristic ‘swimming-like’ movement. The ecology and phylogeny of I. rivuli gen. et sp. nov. is discussed in relation to the diversity of other gyrodactylids in Trinidad.

Gyrodactylus jarocho sp. nov. and Gyrodactylus xalapensis sp. nov. (Platyhelminthes: Monogenea) from Mexican poeciliids (Teleostei: Cyprinodontiformes), with comments on the known gyrodactylid fauna infecting poeciliid fish

Poeciliid fish have been dispersed worldwide with the ornamental fish trade and as part of mosquito control programmes, and with them their gyrodactylid parasites. Due to the easy maintenance and reproduction in aquaria of both poeciliid fish hosts and gyrodactylid parasites, several ecological, epidemiological and parasitological studies have been made with them. To date, nine species of Gyrodactylus are known to infect poeciliid fish: Gyrodactylus bullatarudis Turnbull, 1956, Gyrodactylus costaricensis Kritsky & Fritts, 1970, Gyrodactylus cytophagus Paperna, 1968, Gyrodactylus gambusiae Rogers & Wellborn, 1965, Gyrodactylus milleri Harris & Cable, 2000, Gyrodactylus pictae Cable, van Oosterhout, Barson & Harris, 2005, Gyrodactylus poeciliae Harris & Cable, 2000, Gyrodactylus rasini Lucký, 1973, and Gyrodactylus turnbulli Harris, 1986. We describe two new gyrodactylid species from wild Mexican poeciliid fish collected within their native distribution ranges: Gyrodactylus jarocho sp. nov. from Xiphophorus hellerii Heckel and Gyrodactylus xalapensis sp. nov. from Heterandria bimaculata Heckel, the first gyrodactylid to be described from this host. We also present a new host and locality record for G. bullatarudis, which was found on Poecilia mexicana Steindachner. Mexican samples were compared with museum specimens of all known gyrodactylids from poeciliid hosts, which were subjected to morphometric analysis. Both new species were clearly separated from all other known gyrodactylids infecting poeciliid fish in principal components analyses (PCA). Marginal hook sickle morphology is the key to the separation and discrimination of all the gyrodactylids parasitizing poeciliids, and we provide graphical and morphological data to distinguish between the eleven described gyrodactylid species from poeciliid hosts; we hope this proves a practical tool to discriminate between these otherwise morphologically similar parasites. Finally, we present a re-description of the marginal hooks of G. milleri, because re-examination of the holotype demonstrated the presence of three differently-shaped marginal hook sickles. This is the second known species of Gyrodactylus to have noticeably differently-shaped and sized marginal hooks.

The first record of Macrogyrodactylus species (Monogenea, Gyrodactylidae) on freshwater fishes in Senegal with the description of Macrogyrodactylus simentiensis sp. nov., a parasite of Polypterus senegalus Cuvier

The first record of monogenean parasites of the genus Macrogyrodactylus Malmberg, 1957 on freshwater fish in Senegal is presented. Macrogyrodactylus congolensis Prudhoe, 1957 from the skin and Macrogyrodactylus heterobranchii N’Douba et Lambert, 1999 from the gills of Clarias anguillaris L. were found, representing new host records for these parasites. On Polypterus senegalus Cuvier, three Macrogyrodactylus species were identified, Macrogyrodactylus polypteri Malmberg, 1957, Macrogyrodactylus simentiensis sp. nov. and Macrogyrodactylus sp. M. simentiensis sp. nov. can be readily distinguished from the other Macrogyrodactylus species by the size of its hamuli and the shape of its marginal hook sickles. The marginal hooks on the anterolateral lobes of M. simentiensis differ in size and shape from those on the posterior margin of the haptor. Measurements and drawings of the haptoral sclerites of all five identified species are provided.

The use of statistical classifiers for the discrimination of species of the genus Gyrodactylus (Monogenea) parasitizing salmonids

This study applies flexible statistical methods to morphometric measurements obtained via light and scanning electron microscopy (SEM) to discriminate closely related species of Gyrodactylus parasitic on salmonids. For the first analysis, morphometric measurements taken from the opisthaptoral hooks and bars of 5 species of gyrodactylid were derived from images obtained by SEM and used to assess the prediction performance of 4 statistical methods (nearest neighbours; feed-forward neural network; projection pursuit regression and linear discriminant analysis). The performance of 2 methods, nearest neighbours and a feed-forward neural network provided perfect discrimination of G. salaris from 4 other species of Gyrodactylus when using measurements taken from only a single structure, the marginal hook. Data derived from images using light microscopy taken from the full complement of opisthaptoral hooks and bars were also tested and nearest neighbours and linear discriminant analysis gave perfect discrimination of G. salaris from G. derjavini Mikailov, 1975 and G. truttae Gläser, 1974. The nearest neighbours method had the least misclassifications and was therefore assessed further for the analysis of individual hooks. Five morphometric parameters from the marginal hook subset (total length, shaft length, sickle length, sickle proximal width and sickle distal width) gave near perfect discrimination of G. salaris. For perfect discrimination therefore, larger numbers of parameters are required at the light level than at the SEM level.

Description of Gyrodactylus micropteri n.sp. from Micropterus dolomieui in Lake Huron, with a review of the taxonomy of species of Gyrodactylus (Monogenea) parasitizing centrarchid fishes in North America

An extensive collection of Gyrodactylus from centrarchid fishes in Ontario is examined. Gyrodactylus goerani Hanek and Fernando, 1971 is recorded from Ambloplites rupestris in Lake Ontario and Lepomis gibbosus, Lepomis macrochirus, and Pomoxis sp. in Lake Erie. Gyrodactylus macrochiri Hoffman and Putz, 1964 is recorded from L. gibbosus in Algonquin Park. Gyrodactylus micropteri n.sp. is described from Micropterus dolomieui in Lake Huron. The new species has a marginal hook sickle with a blade that toward its tip curves substantially inward. Examination of type specimens of G. goerani, G. macrochiri, and three other species specific to centrarchid fishes in North America (Gyrodactylus gloriosi Rogers, 1968, Gyrodactylus heterodactylus Rogers and Wellborn, 1965, and Gyrodactylus lineadactylus Wellborn, 1967) revealed that the original species descriptions are inadequate with respect to the diagnostically important marginal hook sickles. The haptoral sclerites of these species are redrawn.

Pathology of five species of Gyrodactylus Nordmann, 1832 (Monogenea)

Attachment-site pathology of the ectoparasites Gyrodactylus adspersi Cone and Wiles, 1983 on Tautogolabrus adspersus, Gyrodactylus avalonia Hanek and Threlfall, 1969 on Gasterosteus aculeatus, Gyrodactylus bullatarudis Turnbull, 1956 on Poecilia reticulata, Gyrodactylus sp. on Carassius auratus, and Gyrodactylus salmonis (Yin and Sproston, 1948) on Salmo gairdneri was examined using optical microscopy and scanning electron microscopy. In the first four species, the disc-shaped haptor attached itself to the host skin surface by means of blade tips of 16 peripherally located marginal hooks, with the two ventrally located hamulus blades compressing the underlying epithelium into a small depression. Tissue damage from attachment and feeding was minimal. However, G. salmonis lodged its marginal hook sickles deep into the host epidermis and appeared to cause extensive fin damage and skin discoloration. There was little evidence of bacterial involvement in the wounds, but bacterial microcolonies were observed on the body surface and haptor of G. salmonis. The latter results are discussed in relation to our understanding of gyrodactyliasis.

Gyrodactylus fryi n. sp. (Monogenea) from Esox masquinongy Mitchill in Ontario

Gyrodactylus fryi n. sp. (Monogenea) is described from the body surface of Esox masquinongy Mitchill in Ontario. Gyrodactxlus fryi resembles most closely G. lingulatus Rogers, 1968 from the cyprinid Hypentelium etowanum (Jordan) in Alabama in having well-developed hamuli, a compact ventral bar with no anterolateral processes, a tongue-shaped ventral bar membrane, and a penis with small spines in two arched rows. Gyrodactylus fryi is easily distinguished from G. lingulatus by marginal hook size (11 to 14 μm long. 7 to 8 μm wide proximally, 14 to 16 μm wide distally) and shape (relatively small base with a long thin blade). Gyrodactylus fryi resembles at least nine other Gyrodactylus species known from cyprinid and catostomid fishes. The study concludes that a close ecological association between a piscivorous ancestral E. masquinongy and cyprinid and (or) catostomid fishes led eventually to evolutionary radiation of a gyrodactylid lineage from prey to predator.

The oncomiracidium and post-oncomiracidial development of the hexabothriid monogenean Rajonchocotyle emarginata

SUMMARYA description is given of some features of the embryonic development, the structure of the oncomiracidium and the postlarval development of R. emarginata, a hexabothriid parasite on the gills of Raia clavata.There are three phases in the larval development of the haptor of Rajonchocotyle: an oncomiracidial or marginal hook stage, a hamulus stage and a sucker stage. Neither the embryo nor the oncomiracidium ever possesses more than five pairs of marginal hooks and marginal hooks I (the posterior-most pair) are considered to be missing. The marginal hooks develop within distinct binucleate oncoblasts. During the early stages of post-oncomiracidial growth the secondary attachment organs of the haptor are formed and it is only after the completion of the development of the haptor that the reproductive organs begin to appear. Firstly, a pair of hamuli is acquired, followed by four pairs of suckers, which form in posterior-anterior succession at the site of marginal hooks III-VI. The first pair of suckers remains unarmed while the other three pairs acquire hooked sclerites and become the main functional attachment organs of the adult. As the first pair of suckers appears the posterior part of the haptor lengthens to form a caudal appendage. Hexabothriids are considered to show closer affinity to the 8-suckered chimaericolids and diclidophorids than to the 6-suckered polysto-matids, the unarmed suckers representing a simplification, by loss of the sclerite and reduction in sucker size, of an originally armed sucker.I would like to express my thanks to Dr J. Llewellyn for his interest and for much helpful discussion.Thanks are also due to the Director and Staff of the Marine Biological Association at Plymouth, in particular Mr J. E. Green for material and assistance, and to Dr A.j Brinkmann, of the Department of Zoology, University of Bergen, for supplying specimens of Squalonchocotyle borealis.