Microsporidia in mosquitoes can be divided into two categories based on their life cycles and host-parasite relationships. Some species of microsporidia exhibit simple life cycles with one spore type responsible for oral (horizontal) transmission. They affect only one generation of the mosquito and are not usually host or tissue specific. Brachiola algerae (Vavra et Undeen, 1970) and Vavraia culicis (Weiser, 1947) are examples of species isolated from mosquitoes with relatively straightforward life cycles (one spore type) and simple host-parasite relationships. B. algerae and a close relative of V. culicis have also been isolated from a vertebrate (human) host but sources for these infections are unknown. In contrast to B. algerae and V. culicis, polymorphic (heterosporous) microsporidia in mosquitoes are characterized by complex life cycles involving multiple spore types responsible for horizontal and vertical transmission. They affect two generations of the mosquito and some involve an obligate intermediate host. These microsporidia are generally very host and tissue specific with complex developmental sequences comprised of unique stages and events. The microsporidium Edhazardia aedis (Kudo, 1930) is a pathogen of Aedes aegypti and does not require an intermediate host. The developmental cycle of E. aedis is characterized by four sporulation sequences, two in the parental host and two in the filial generation. Recent speculation relative to the source of B. algerae human infection have implicated infected mosquitoes and raised concerns about the safety of mosquito microsporidia in general. The subject of this review is to compare and contrast three species of microsporidia from mosquitoes, two with broad host ranges (B. algerae and V. culicis) and one specific to mosquitoes (E. aedis). This review describes features that distinguish mosquito-parasitic microsporidia with simple life cycles and broad host ranges from truly mosquito-specific microsporidian parasites with complex life cycles.
Steroid 5α-reductase type 3 congenital disorder of glycosylation (SRD5A3-CDG) is a severe metabolic disease manifesting as muscle hypotonia, developmental delay, cerebellar ataxia and ocular symptoms; typically, nystagmus and optic disc pallor. Recently, early onset retinal dystrophy has been reported as an additional feature. In this study, we summarize ocular phenotypes and SRD5A3 variants reported to be associated with SRD5A3-CDG. We also describe in detail the ophthalmic findings in a 12-year-old Czech child harbouring a novel homozygous variant, c.436G>A, p.(Glu146Lys) in SRD5A3. The patient was reviewed for congenital nystagmus and bilateral optic neuropathy diagnosed at 13 months of age. Examination by spectral domain optical coherence tomography and fundus autofluorescence imaging showed clear signs of retinal dystrophy not recognized until our investigation. Best corrected visual acuity was decreased to 0.15 and 0.16 in the right and left eye, respectively, with a myopic refractive error of -3.0 dioptre sphere (DS) /-2.5 dioptre cylinder (DC) in the right and -3.0 DS / -3.0 DC in the left eye. The proband also had optic head nerve drusen, which have not been previously observed in this syndrome. and Corresponding author: Petra Lišková
Progrillotia pastinacae Dollfus, 1946 (Cestoda: Trypanorhyncha) is redescribed from the spiral valve of Dasyatis pastinaca (Linnaeus) (Dasyatididae) from the coast of France. Progrillotia dasyatidis sp. n. is described from the spiral valves of Dasyatis tortonesei Capapé (Dasyatididae) from the Mediterranean in the Gulf of Gabès (Tunisia) and D. pastinaca from the Bassin d'Arcachon (France). The new species differs from congeners in having, on the tentacles, a single rather than two rows of intercalary hooks and fewer testes. The generic definition is emended based upon the new species, the redescription of P. pastinacae Dollfus, 1946 and re-examination of the type specimen of P. louiseuzeti Dollfus, 1969. Important additional characters noted are that the tentacular hooks are solid, a prebulbar organ is present and that there are gland cells attached to the retractor muscle within the bulb. A cladistic analysis suggests that the genus is closely allied with the Eutetrarhynchidae. Progrillotia dollfusi Carvajal et Rego, 1983 is provisionally excluded from the genus as the adult of the species is unknown and a key character of the genus is that the testes are pre-ovarian.
The family Rhopalothylacidae (Cestoda: Trypanorhyncha) is reviewed. The type species, Rhopalothylax gymnorhynchoides Guiart, 1935, is redescribed from the type specimens and belongs within the genus Pintneriella Yamaguti, 1934, previously described only from the plerocercus. Rhopalothylax therefore becomes a junior synonym of Pintneriella. The adult of Pintneriella musculicola Yamaguti, 1934 is described for the first time, from the shark Carcharias taurus Rafinesque from Australia. Pintneriella is characterised by two bothridia, a typical heteroacanthous armature, a unique, bipartite external seminal vesicle and a uterus deviated porally, terminating at a uterine pore. It belongs within the Heteracanthoidea but is distinguishable both from the Eutetrarhynchidae and the Gilquiniidae, the two families which it most closely resembles. Cladistic analyses align Pintneriella within the clade containing the families Gilquiniidae, Gymnorhynchidae and Molicolidae rather than with the Eutetrarhynchidae. The family Rhopalothylacidae is therefore retained provisionally to accommodate Pintneriella within the Heteracanthoidea. The second genus of the Rhopalothylacidae, Clujia Guiart, 1935, is unrecognisable from its description and cannot be redescribed from its holotype. It is therefore considered a genus inquirendum.
Loma salmonae (Putz, Hoffman et Dunbar, 1965) is a common gill parasite of salmonids, and essentially all species in the genus Oncorhynchus are susceptible. Infections occur in both fresh and salt water. Loma salmonae is directly transmissible by ingestion of spores or infected tissue. The parasite infects the wall of blood vessels of various organs, but the gill is the primary site of infection. Initial infection occurs in the intestine, and xenomas are easily detected in the gills by standard histology at 4-6 wk post-exposure. A few presporogonic stages of the parasite are found in the heart endothelium prior to xenoma formation in the gills. Ultrastructure studies of early infections demonstrated that wandering blood cells transport the meronts to the gills, and that merogony occurs in pillar cells and other cells underlying the gill endothelium. Xenomas develop in these cells, resulting in hypertrophied host cells filled with spores. Xenomas ultimately rupture, and are associated with severe inflammation in which free spores are found in macrophages. The parasites are most pathogenic during this phase of the infection, resulting in severe vasculitis and clinical disease. Both rainbow trout (Oncorhynchus mykiss) and Chinook salmon (Oncorhynchus tshawytscha) recover from infections, but free spores persist in kidney and spleen phagocytes for many months after xenomas are absent in Chinook salmon. Fish that have recovered from the infection show strong immunity against the parasite, lasting up to 1 year. Fish are susceptible to infection by other routes of exposure by spores; co-habitation, anal gavage, and intramuscular, intraperitoneal and intravascular injection. Autoinfection probably occurs following release of spores in blood vessels after xenomas rupture. The optimal temperature for L. salmonae infections is 15-17°C, with a permissive range of 11-20°C.
Species of Rhamnocercinae Monaco, Wood et Mizelle, 1954 are gill parasites of sciaenid fishes (Perciformes). Seven are marine species (three in the western Atlantic and four in oriental Pacific) and one is a neotropical freshwater species (Rio Doce Basin, Brazil). While the status of the subfamily may be questioned, this assemblage of species is apparently supported by several shared apomorphic and plesiomorphic characters, such as: (1) peduncular spines with anterior and posterior roots; (2) haptor laterally expanded, armed with anchors (two pairs); bars (one ventral, two dorsal); 14 hooks and haptoral accessory spines; and (3) double (nested) tubes of the male copulatory organ (MCO), directed posteriorly with the genital pore lying posterior to the MCO. The phylogenetic hypothesis for the eight known species of this clade is: (Spinomatrix penteormos (Rhamnocercoides stichospinus, Rhamnocercoides menticirrhi) Rhamnocercus oliveri (Rhamnocercus rhamnocercus (Rhamnocercus stelliferi, Rhamnocercus bairdiella, Rhamnocercus margaritae)). This hypothesis indicates that Spinomatrix penteormos represents the sister group of all remaining rhamnocercines. The resulting phylogenetic sister-group relationships support the transfer of Rhamnocercus stichospinus Seamster et Wood, 1956 to Rhamnocercoides Luque et Iannacone, 1991 as Rhamnocercoides stichospinus (Seamster et Wood, 1956) n. comb.
Dioncopseudobenedenia Yamaguti, 1965 (Monogenea: Capsalidae) is redefined. Dioncopseudobenedenia kala Yamaguti, 1965 (type species) is redescribed from type material from Hawaii and from new specimens from Heron Island, Queensland, Australia and New Caledonia. We made detailed observations on D. macracantha Yamaguti, 1968 from type material from Hawaii, and from new material from Heron Island and New Caledonia. Dioncopseudobenedenia ancoralis sp. n. is described from the gill chamber of Siganus lineatus (Valenciennes) from Green Island and Heron Island, Australia and from New Caledonia. This study confirms that only one pair of large central sclerites is present on the haptor in Dioncopseudobenedenia species. The male copulatory organ in species of Dioncopseudobenedenia is a penis contained in a fluid-filled space (= penis canal) with weakly muscular walls. Dioncopseudobenedenia kala and D. ancoralis bear a sclerite at the tip of the penis. In D. macracantha, the structure of the penis, which has no terminal sclerite, indicates it may combine the functions of a penis and a cirrus. Dioncopseudobenedenia is compared with Calicobenedenia Kritsky et Fennessy, 1999, the other capsalid genus with a single pair of large sclerites on the haptor. The large haptoral sclerites in species of Dioncopseudobenedenia resemble accessory sclerites, whereas those of C. polyprioni Kritsky et Fennessy, 1999 resemble hamuli. Observations of oncomiracidia confirmed that the large haptoral sclerites in D. kala are accessory sclerites. Haptoral morphology suggests that different Dioncopseudobenedenia spp. employ different means of attachment. Mating behaviour was observed twice between two different pairs of D. kala specimens from Heron Island. Two preserved specimens from Nouméa, New Caledonia had structures near the dorsal vaginal pore that we interpret as spermatophores. This is the first report of spermatophores in a capsalid inhabiting the gill chamber. The geographic distribution of Dioncopseudobenedenia spp. is discussed.
Monozoic cestodes of the genus Khawia Hsü, 1935 (Caryophyllidea: Lytocestidae), parasites of cyprinid fish in Europe, Asia, Africa and North America, are revised on the basis of taxonomic evaluation of extensive materials, including recently collected specimens of most species. This evaluation has made it possible to critically assess the validity of all 17 nominal species of the genus and to provide redescriptions of the following seven species considered to be valid: Khawia sinensis Hsü, 1935 (type species); K. armeniaca (Cholodkovsky, 1915); K. baltica Szidat, 1941; K. japonensis (Yamaguti, 1934); K. parva (Zmeev, 1936); K. rossittensis (Szidat, 1937); and K. saurogobii Xi, Oros, Wang, Wu, Gao et Nie, 2009. Several new synonyms are proposed: Khawia barbi Rahemo et Mohammad, 2002 and K. lutei Al-Kalak et Rahemo, 2003 are synonymized with K. armeniaca; K. coregoni Kritscher, 1990 with Caryophyllaeus laticeps (Pallas, 1781) (family Caryophyllaeidae); K. cyprini Li, 1964 and K. iowensis Calentine et Ulmer, 1961 with K. japonensis; K. dubia (Szidat, 1937) (syn. Bothrioscolex dubius Szidat, 1937) with K. rossittensis; and Tsengia neimongkuensis Li, 1964 and T. xiamenensis Liu, Yang et Lin, 1995 with K. sinensis. Khawia prussica (Szidat, 1937) (syn. Bothrioscolex prussicus Szidat, 1937) is considered to be species incertae sedis, but its morphology indicates it may belong to Caryophyllaeus Gmelin, 1790 (Caryophyllaeidae). The molecular analysis of all seven valid species, based on comparison of sequences of two nuclear ribosomal and two mitochondrial genes, has shown that the species form three major groups clustered according to their fish hosts. Five species from common and crucian carp and goldfish were grouped together, whereas K. armeniaca from barbels (Barbinae) and K. baltica from tench (Tinca) formed separate clades. In contrast, geographical distribution does not seem to play a crucial role in grouping of individual taxa. A phylogenetic tree based on morphological characters was incongruent with that inferred from molecular data, which indicates that some morphological traits may be homoplastic. A key to identification of all species of Khawia based on morphological characteristics is provided.
This study revises the originally monotypic genus Afrogyrodactylus Paperna, 1968 (Monogenea), the species of which infect alestid fish (Characiformes) in Africa, and includes new records of these parasites from three geographically distant countries, Senegal, Sudan and South Africa. Morphology of opisthaptoral hooks and bars and nuclear ribosomal DNA data revealed three Afrogyrodactylus species. Afrogyrodactylus girgifae sp. n. is described from the fins of the Sudanese nurse tetra, Brycinus nurse (Rüppell), and A. kingi sp. n. presents from the gill arches of the South African sharptooth tetra, Micralestes acutidens (Peters), whereas a previously undescribed Afrogyrodactylus sp. occurred on the fins of B. nurse from Senegal. All three species differ conspicuously from the only one known species of this genus, A. characinis Paperna, 1968, by the dimensions of their haptoral hard parts. Detailed morphological and molecular descriptions and comparisons are presented.
The free-energy-based reinforcement learning is a new approach to handling high-dimensional states and actions. We investigate its properties using a new experimental platform called the digit floor task. In this task, the high-dimensional pixel data of hand-written digits were directly used as sensory inputs to the reinforcement learning agent. The simulation results showed the robustness of the free-energy-based reinforcement learning method against noise applied in both the training and testing phases. In addition, reward-dependent sensory representations were found in the distributed activation patterns of hidden units. The representations coded in a distributed fashion persisted even when the number of hidden nodes were varied.