BackgroundIn the past decades, many studies focused on the cell motility of apicomplexan invasive stages as they represent a potential target for chemotherapeutic intervention. Gregarines (Conoidasida, Gregarinasina) are a heterogeneous group that parasitize invertebrates and urochordates, and are thought to be an early branching lineage of Apicomplexa. As characteristic of apicomplexan zoites, gregarines are covered by a complicated pellicle, consisting of the plasma membrane and the closely apposed inner membrane complex, which is associated with a number of cytoskeletal elements. The cell cortex of eugregarines, the epicyte, is more complicated than that of other apicomplexans, as it forms various superficial structures.ResultsThe epicyte of the eugregarines, Gregarina cuneata, G. polymorpha and G. steini, analysed in the present study is organised in longitudinal folds covering the entire cell. In mature trophozoites and gamonts, each epicytic fold exhibits similar ectoplasmic structures and is built up from the plasma membrane, inner membrane complex, 12-nm filaments, rippled dense structures and basal lamina. In addition, rib-like myonemes and an ectoplasmic network are frequently observed. Under experimental conditions, eugregarines showed varied speeds and paths of simple linear gliding. In all three species, actin and myosin were associated with the pellicle, and this actomyosin complex appeared to be restricted to the lateral parts of the epicytic folds. Treatment of living gamonts with jasplakinolide and cytochalasin D confirmed that actin actively participates in gregarine gliding. Contributions to gliding of specific subcellular components are discussed.ConclusionsCell motility in gregarines and other apicomplexans share features in common, i.e. a three-layered pellicle, an actomyosin complex, and the polymerisation of actin during gliding. Although the general architecture and supramolecular organisation of the pellicle is not correlated with gliding rates of eugregarines, an increase in cytoplasmic mucus concentration is correlated. Furthermore, our data suggest that gregarines utilize several mechanisms of cell motility and that this is influenced by environmental conditions.
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.
The results of a systematic survey of monogeneans collected from the gills of the African carp, Labeo coubie (Cyprinidae) from the Gambia River basins in the Niokolo-Koba National Park, Senegal, are presented. The following 11 previously described species belonging to Dactylogyrus and Dogielius (Dactylogyridae) are reported: Dactylogyrus retroversus Guégan, Lambert & Euzet, 1988, Dactylogyrus titus Guégan, Lambert & Euzet, 1988, Dactylogyrus falcilocus Guégan, Lambert & Euzet, 1988, Dactylogyrus decaspirus Guégan, Lambert & Euzet, 1988, Dactylogyrus oligospirophallus Paperna, 1973, Dactylogyrus jaculus Guégan, Lambert & Euzet, 1988, Dogielius anthocolpos Guégan, Lambert & Euzet, 1989, Dogielius clavipenis Guégan, Lambert & Euzet, 1989, Dogielius harpagatus Guégan, Lambert & Euzet, 1989, Dogielius complicitus Guégan, Lambert & Euzet, 1989, and Dogielius flagellatus Guégan, Lambert & Euzet, 1989. Three new species of Dactylogyrus with 2 haptoral bars are described as follows: Dactylogyrus yassensis n. sp., Dactylogyrus dembae n. sp., and Dactylogyrus leonis n. sp. The sclerotized structures of type and voucher specimens of Dactylogyrus cyclocirrus Paperna, 1973, Dactylogyrus omega Guégan & Lambert, 1991, and Dactylogyrus cf labeous Paperna, 1979 are illustrated for comparative purposes. The type specimens indicate that D. cyclocirrus is based on specimens of two different species, among which the lectotype is designated from the syntypes collected from Labeo cylindricus. Dactylogyrus cyclocirrus of Guégan et al. (1988) and D. cf labeous Paperna, 1979 are considered senior subjective synonyms of D. yassensis n. sp. and D. dembae n. sp., respectively.
The first record of Gyrodactylus species Nordmann, 1832 on the cichlid fish from Senegal is reported. Gyrodactylus parasites were found on four host species studied, Hemichromis fasciatus, Hemichromis letournaeuxi, Oreochromis niloticus, and Sarotherodon galilaeus. Gyrodactylus cichlidarum Paperna (Bamidgeh 13:14-29, 1968) were collected from H. fasciatus, and its identity was confirmed based on the morphometrical comparison with the holotype specimens of G. cichlidarum. Only one specimen of Gyrodactylus sp. was noted on H. letournaeuxi. The gyrodactylid specimens on O. niloticus and S. galilaeus were described as Gyrodactylus ergensi n. sp. based on the detailed morphometrical analysis supported by sequencing. The haptoral sclerites of G. ergensi n. sp., which closely resemble those of Gyrodactylus nyanzae Paperna, 1973, are compared with the type material and discussed. A partial sequence of the internal transcribed spacer recombinant DNA (ITS rDNA) was obtained from two specimens of G. ergensi, and a close relationship between G. ergensi n. sp. and G. cichlidarum is suggested based on 92% similarity in ITS rDNA region.
One previously described and 1 new species of Nanotrema Paperna, 1969 are reported from the gills of Citharinus citharus citharus (Citharinidae) collected from the Niokolo Koba River, Senegal. Nanotrema citharini Paperna, 1969 is redescribed, based on the re-examination of the type specimens and new information obtained from material taken in Senegal (new locality record). Nanotrema niokoloensis sp. nov. is distinguished primarily by possessing a copulatory organ composed of a long thin tube with median portion usually coiled into about 2.5 rings and an accessory piece resembling a braid lying within the rings. Based on the presence of the dorsal anchors modified into paired haptoral spikes, which lack an associated bar, species of Nanotrema phenotypically appear to be related to those of Neotropical Rhinoxenus Kritsky, Boeger et Thatcher, 1988 and Indian Spicocleidus Agrawal, Tripathi et Shukla, 2005.
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