Jamie Bojko

Parahepatospora carcini n. gen., n. sp., a parasite of invasive Carcinus maenas with intermediate features of sporogony between the Enterocytozoon clade and other microsporidia

Parahepatospora carcini n. gen. n. sp., is a novel microsporidian parasite discovered infecting the cytoplasm of epithelial cells of the hepatopancreas of a single Carcinus maenas specimen. The crab was sampled from within its invasive range in Atlantic Canada (Nova Scotia). Histopathology and transmission electron microscopy were used to show the development of the parasite within a simple interfacial membrane, culminating in the formation of unikaryotic spores with 5-6 turns of an isofilar polar filament. Formation of a multinucleate meront (>12 nuclei observed) preceded thickening and invagination of the plasmodial membrane, and in many cases, formation of spore extrusion precursors (polar filaments, anchoring disk) prior to complete separation of pre-sporoblasts from the sporogonial plasmodium. This developmental feature is intermediate between the Enterocytozoonidae (formation of spore extrusion precursors within the sporont plasmodium) and all other Microsporidia (formation of spore extrusion precursors after separation of sporont from the sporont plasmodium). SSU rRNA-based gene phylogenies place P. carcini within microsporidian Clade IV, between the Enterocytozoonidae and the so-called Enterocytospora-clade, which includes Enterocytospora artemiae and Globulispora mitoportans. Both of these groups contain gut-infecting microsporidians of aquatic invertebrates, fish and humans. According to morphological and phylogenetic characters, we propose that P. carcini occupies a basal position to the Enterocytozoonidae. We discuss the discovery of this parasite from a taxonomic perspective and consider its origins and presence within a high profile invasive host on the Atlantic Canadian coastline.

Parasites, pathogens and commensals in the “low-impact” non-native amphipod host Gammarus roeselii

BackgroundWhilst vastly understudied, pathogens of non-native species (NNS) are increasingly recognised as important threats to native wildlife. This study builds upon recent recommendations for improved screening for pathogens in NNS by focusing on populations of Gammarus roeselii in Chojna, north-western Poland. At this location, and in other parts of continental Europe, G. roeselii is considered a well-established and relatively ‘low-impact’ invader, with little understanding about its underlying pathogen profile and even less on potential spill-over of these pathogens to native species.ResultsUsing a combination of histological, ultrastructural and phylogenetic approaches, we define a pathogen profile for non-native populations of G. roeselii in Poland. This profile comprised acanthocephalans (Polymorphus minutus Goese, 1782 and Pomphorhynchus sp.), digenean trematodes, commensal rotifers, commensal and parasitic ciliated protists, gregarines, microsporidia, a putative rickettsia-like organism, filamentous bacteria and two viral pathogens, the majority of which are previously unknown to science. To demonstrate potential for such pathogenic risks to be characterised from a taxonomic perspective, one of the pathogens, a novel microsporidian, is described based upon its pathology, developmental cycle and SSU rRNA gene phylogeny. The novel microsporidian Cucumispora roeselii n. sp. displayed closest morphological and phylogenetic similarity to two previously described taxa, Cucumispora dikerogammari (Ovcharenko & Kurandina, 1987), and Cucumispora ornata Bojko, Dunn, Stebbing, Ross, Kerr & Stentiford, 2015.ConclusionsIn addition to our discovery extending the host range for the genus Cucumispora Ovcharenko, Bacela, Wilkinson, Ironside, Rigaud & Wattier, 2010 outside of the amphipod host genus Dikerogammarus Stebbing, we reveal significant potential for the co-transfer of (previously unknown) pathogens alongside this host when invading novel locations. This study highlights the importance of pre-invasion screening of low-impact NNS and, provides a means to document and potentially mitigate the additional risks posed by previously unknown pathogens.

White Spot Syndrome Virus and the Caribbean Spiny Lobster, Panulirus argus: Susceptibility and Behavioral Immunity

The Caribbean spiny lobster Panulirus argus is susceptible to infection by Panulirus argus Virus 1 (PaV1), the only virus known to naturally infect any lobster species. However, P. argus is able to mitigate PaV1 transmission risk by avoiding infected individuals. White Spot Syndrome Virus (WSSV) has a particularly wide host range. WSSV has not been documented in wild populations of spiny lobsters, but has been experimentally transmitted to six other lobster species from the genus Panulirus spp. While WSSV has been detected intermittently in wild populations of shrimp in the Caribbean region, the risk to P. argus has not been evaluated. Potential emergence of the disease could result in fisheries losses and ecological disruption. To assess the risk to P. argus, we tested its susceptibility to WSSV via injection and waterborne transmission. We also tested whether healthy lobsters can detect and avoid conspecifics with qPCR-quantifiable WSSV infections. We found P. argus to be highly susceptible to WSSV via intramuscular injection, with mortality reaching 88% four weeks post inoculation. Panulirus argus was also susceptible to WSSV via waterborne transmission, but WSSV burden was low after four weeks via qPCR. Behavioral assays indicated that P. argus can detect and avoid conspecifics infected with WSSV and the avoidance response was strongest for the most heavily infected individuals – a response comparable to PaV1-infected conspecifics. Panulirus argus is the first spiny lobster found to be susceptible to WSSV in the Americas, but it is possible that a generalized avoidance response by healthy lobsters against infected conspecifics provides a behavioral defense and may reduce WSSV infection potential and prevalence. Such avoidance may extend to other directly transmitted pathogens in spiny lobster populations preventing them from becoming common in their population. Author Summary Erica P. Ross is a PhD candidate at the University of Florida, studying the disease ecology of the Caribbean spiny lobster, with a focus on chemosensory ecology. Donald C. Behringer is an associate professor at the University of Florida and his research focuses on disease ecology, epidemiology, and fishery ecology, with a focus on crustaceans and other marine invertebrates. Jamie Bojko received his PhD from the University of Leeds and is currently a post-doctorate associate at the University of Florida studying experimental and systemic crustacean pathology.

Periwinkles and parasites: the occurrence and phenotypic effects of parasites in Littorina saxatilis and L. arcana in northeastern England

Littorina saxatilis is a common intertidal gastropod on shores of the North Atlantic, and an important study species for evolutionary investigations. Its congener L. arcana is much less widely distributed, but both species are common at Old Peak, Yorkshire, UK. The parasite profiles of L. saxatilis and L. arcana from this shore were determined histologically, revealing a ciliated protist, Protophrya ovicola, an unidentified apicomplexan (present in <1% L. saxatilis) and three trematode parasites tentatively assigned to Renicola sp., Microphallus similis and M. pygmaeus. The profile data include prevalence information and associated histology. Protophrya ovicola associated predominantly with the wave ecotype of L. saxatilis (65%) rather than the crab ecotype (16%). Microphallus similis occurred at a higher prevalence in the L. arcana population (38%) in comparison with the L. saxatilis population (11%). Overall, there appeared to be a lower prevalence of trematodes in the high-shore L. saxatilis. By modelling the occurrence of individual parasites and shell morphometrics, an assessment of parasite-associated morphological change was conducted. We conclude that parasitism appeared not to cause shell-shape change, but rather that snails of a certain shell shape were more likely to display infection. Records of parasites in L. saxatilis and L. arcana are briefly reviewed, showing that the diversity of parasites reported here is relatively low.