High prevalence of Paramarteilia canceri infecting velvet swimming crabs Necora puber in Ireland

Abstract

The velvet swimming crab Necora puber has been fished in Ireland since the early 1980s and contributes significant income to smaller fishing vessels. From 2016 onwards, reduced landings have been reported. We undertook a full pathological investigation of crabs from fishing grounds at 3 sites on the west (Galway), southwest (Castletownbere) and east (Howth) coasts of Ireland. Histopathology, transmission electron microscopy and molecular taxonomic and phylogenetic analyses showed high prevalence and infection level of Paramarteilia canceri, previously only reported from the edible crab Cancer pagurus. This study provides the first molecular data for P. canceri, and shows its phylogenetic position in the order Paramyxida (Rhizaria). Other parasites and symbionts detected in the crabs were also noted, including widespread but low co-infection with Hematodinium sp. and a microsporidian consistent with the Ameson and Nadelspora genera. This is the first histological record of Hematodinium sp. in velvet crabs from Ireland. Four N. puber individuals across 2 sites were co-infected by P. canceri and Hematodinium sp. At one site, 3 velvet crabs infected with P. canceri were co-infected with the first microsporidian recorded from this host; the microsporidian 18S sequence was almost identical to Ameson pulvis, known to infect European shore crabs Carcinus maenas. The study provides a comprehensive phylogenetic analysis of this and all other available Ameson and Nadelspora 18S sequences. Together, these findings provide a baseline for further investigations of N. puber populations along the coast of Ireland.

Long amplicons as a tool to identify variable regions of ribosomal RNA for improved taxonomic resolution and diagnostic assay design in microeukaryotes: using ascetosporea as a case study

“…Orchestia spp. amphipods infected with P. orchestiae were collected from the Gann Estuary, Pembrokeshire in 2019 (Collins et al, 2022) and velvet swimming crabs (N. puber) infected with P. canceri were collected from Galway Bay in 2015 and 2016 (Collins et al, 2022). Flat oysters infected with B. ostreae were sourced from Mersea, Essex in 2018.…”

“…A tissue cross-section from individual cockles from Wales infected with M. cocosarum (Skujina et al, 2022), digestive gland from cockles infected with M. cochillia (Skujina et al, 2022), gill tissue from velvet crabs infected with P. canceri (Collins et al, 2022) and whole amphipods infected with P. orchestiae (Collins et al, 2022) were fixed whole in 100% molecular grade ethanol. Tissue was homogenised in Lifton's Buffer (Nishiguchi et al, 2002) or CTAB and extracted using a phenol:chloroform method (Winnepenninckx et al, 1993).…”

“…P. orchestiae amplicons covering partial 18S, ITS1, 5.8S, ITS2 and partial 28S were amplified using PMart_18S_For (Collins et al, 2022) and LSU8799degen with an annealing temperature of 65°C, and P. canceri amplicons covering the same region were amplified using PMart_18S_For (Collins et al, 2022) and s20cAS with an annealing temperature of 60°C. Amplicons for both Paramarteilia species covering partial 28S, IGS, 18S, ITS1 and partial 5.8S were amplified using PMart28SF and PMart_58S_Rev (Collins et al, 2022) with an annealing temperature of 57°C.…”

“…Until recently, the known host range of P. canceri was limited to the edible crab, Cancer pagurus, and was infrequently detected. However, (Collins et al, 2022) reported that the decline in landings of the adult velvet swimming crab (Necora puber) in Galway Bay, Ireland, was associated with high levels of infection by P. canceri, suggesting that this parasite may be of significance to fisheries. P. orchestiae has been shown to infect multiple amphipod species including Orchestia aestuarensis (Pickup and Ironside, 2018), O. gammarellus (Ginsburger-Vogel and Desportes, 1979;Ginsburger-Vogel, 1991) and Echinogammarus marinus (Short et al, 2012;Ward et al, 2016).…”

“…P. orchestiae has been shown to infect multiple amphipod species including Orchestia aestuarensis (Pickup and Ironside, 2018), O. gammarellus (Ginsburger-Vogel and Desportes, 1979;Ginsburger-Vogel, 1991) and Echinogammarus marinus (Short et al, 2012;Ward et al, 2016). Collins et al (2022) showed that P. canceri and P. orchestiae cannot be reliably separated phylogenetically using 18S sequence data alone, and that the ITS1 region was more suitable to discriminate between these closely related parasites. Like M. cochillia and M. cocosarum, considering differences in host specificity and sequence data, P. canceri and P. orchestiae were considered to be distinct species.…”