Parasites of invasive crustacea: risks and opportunities for control

Invasive species are one of the foremost damaging environmental problems for biodiversity and conservation, and can affect human health and man-made structures. They pose a great challenge for pest management, with little known about their control and few available success stories. Many crustacean species are invasive and can affect both biodiversity and aquaculture. Controlling invasive Crustacea is a complex and arduous process, but success could lead to increased environmental protection and conservation. Invasive Crustacea also comprise a significant pathway for the introduction of invasive pathogens. If these invaders carry pathogens, parasites or commensals to a new site they may threaten native species. Alternatively, pathogens can control their invasive host and could be utilised in a targeted biological control effort as a biocontrol agent. Looking specifically at one species of invasive brachyuran crab (Carcinus maenas) collected from the UK, Faroes Islands and Atlantic Canada, and several species of invasive amphipod from the UK and Poland, I explore which groups of microorganisms are carried alongside invasions, and if any could be used as biocontrol agents or whether they pose a threat to native wildlife. This thesis involves wide-scale screening of Carcinus maenas and several amphipod species, identifying a range of metazoans, fungi, protozoa, bacteria and viruses; many new to science. Taxonomic descriptions are provided for previously unknown taxa: Parahepatospora carcini; Cucumispora ornata; Cucumispora roeselii; and Aquarickettsiella crustaci. The application of metagenomics to pathogen invasion ecology is also explored, determining that it can be used as an early screening system to detect rare and/or asymptomatic microbial associations. Finally, I used experimental systems to assess the impact of pathogens carried by Dikerogammarus haemobaphes upon both itself and alternate host species (Dikerogammarus villosus and Gammarus pulex), identifying that C. ornata can infect native species and decrease their chance of survival. Overall this thesis describes a research process following through three main steps: i) invasive pathogen detection, ii) taxonomic identification, and iii) host range and pathological risk assessment and impact. Screening invasive and non-native hosts for pathogens is recommended for invasive species entering the UK, to provide a fast and informed risk assessment process for hazardous hitchhiking microbes

Revising the Freshwater Thelohania to Astathelohania gen. et comb. nov., and Description of Two New Species

Crayfish are common hosts of microsporidian parasites, prominently from the genus Thelohania. Thelohania is a polyphyletic genus, with multiple genetically distinct lineages found from freshwater and marine environments. Researchers have been calling for a revision of this group for over a decade. We provide evidence that crayfish-infecting freshwater Thelohania are genetically and phylogenetically distinct from the marine Thelohania (Clade V/Glugeida), whilst also describing two new species that give further support to the taxonomic revision. We propose that the freshwater Thelohania should be transferred to their own genus, Astathelohania gen. et comb. nov., in a new family (Astathelohaniidae n. fam.). This results in the revision of Thelohania contejeani (Astathelohania contejeani), Thelohania montirivulorum (Astathelohania montirivulorum), and Thelohania parastaci (Astathelohania parastaci). We also describe two novel muscle-infecting Astathelohania species, A. virili n. sp. and A. rusti n. sp., from North American crayfishes (Faxonius sp.). We used histological, molecular, and ultrastructural data to formally describe the novel isolates. Our data suggest that the Astathelohania are genetically distinct from other known microsporidian genera, outside any described family, and that their SSU rRNA gene sequence diversity follows their host species and native geographic location. The range of this genus currently includes North America, Europe, and Australia

Cirolana westbyi, (Isopoda: Cirolanidae) a new species in the ‘Cirolana parva-group’ from the Turneffe Atoll, Belize

Figure 9. Maximum Likelihood phylogenetic comparison of several members in the Cirolanidae, including the newly sequenced 18S genes of Cirolana westbyi n. sp. and Cirolana parva.Published as part of Jennings, Lucas A., Bojko, Jamie, Rotjan, Randi D. & Behringer, Donald C., 2021, Cirolana westbyi, (Isopoda: Cirolanidae) a new species in the 'Cirolana parva-group' from the Turneffe Atoll, Belize, pp. 2053-2069 in Journal of Natural History 54 (31-32) on page 2065, DOI: 10.1080/00222933.2020.1837273, http://zenodo.org/record/502898

Systematic assessment of the Panopeidae and broader Eubrachyura (Decapoda: Brachyura) using mitochondrial genomics

Abstract This study provides a broad phylogenetic analysis for the Eubrachyura, with the inclusion of three new Panopeidae mitochondrial genomes: Eurypanopeus depressus (flatback mud crab) (15,854bp), Panopeus herbstii (Atlantic mud crab) (15,812bp) and Rhithropanopeus harrisii (Harris, or ‘white-fingered’ mud crab) (15,892bp). These new mitogenomes were analyzed alongside all available brachyuran mitochondrial genomes (n = 113), comprising 80 genera from 29 families, to provide an updated phylogenetic analysis of the infra-order Brachyura (“true crabs”). Our analyses support the subsection Potamoida within the Eubrachyura as the sister group to Thoracotremata. The family Panopeidae aligns with the family Xanthidae to form the Xanthoidea branch, which is supported by current morphological and genetic taxonomy. A unique gene arrangement termed ‘XanGO’ was identified for the panopeids and varies relative to other members of the subsection Heterotremata (within the Eubrachyura) via a transposition of the trnV gene. This gene arrangement is novel and is shared between several Xanthoidea species, including Etisus anaglyptus (hairy spooner crab), Atergatis floridus (brown egg crab), and Atergatis integerrimus (red egg crab), suggesting that it is a conserved gene arrangement within the Xanthoidea superfamily. Our study further reveals a need for taxonomic revision of some brachyuran groups, particularly the Sesarmidae. The inclusion of panopeid mitogenomes into the greater brachyuran phylogeny increases our understanding of crab evolution and higher level Eubrachyuran systematics

Alternosema astaquatica n. sp. (Microsporidia: Enterocytozoonida), a systemic parasite of the crayfish Faxonius virilis

Crayfish have strong ecological impacts in freshwater systems, yet our knowledge of their parasites is limited. This study describes the first systemic microsporidium (infects multiple tissue types) Alternosema astaquatica n. sp. (Enterocytozoonida) isolated from a crayfish host, Faxonius virilis, using histopathology, transmission electron microscopy, gene sequencing, and phylogenetics. The parasite develops in direct contact with the host cell cytoplasm producing mature spores that are monokaryotic and ellipsoid in shape. Spores have 9–10 coils of the polar filament and measure 3.07 ± 0.26 µm (SD) in length and 0.93 ± 0.08 µm (SD) in width. Our novel isolate has high genetic similarity to Alternosema bostrichidis isolated from terrestrial beetles; however, genetic data from this parasite is restricted to a small fragment (396 bp) of the SSU gene. Additional data related to spore morphology and development, host, environment, and ecology indicate that our novel isolate is distinct from A. bostrichidis, which supports a new species description. Alternosema astaquatica n. sp. represents a novel member of the Orthosomella-like group which appears to be a set of opportunists within the Enterocytozoonida. The presence of this microsporidium in F. virilis could be relevant for freshwater ecosystems across this crayfish's broad geographic range in North America and may affect interactions between F. virilis and invasive rusty crayfish Faxonius rusticus in the Midwest USA.</p