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Digenean parasites of shore crabs, Carcinus maenas / ALEXANDER BEDFORD

Swansea University Author: ALEXANDER BEDFORD

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Abstract

This study reports on the prevalence, intensity, and species identification of digenean trematode infections in shore crabs (Carcinus maenas) found at two intertidal survey sites (Mumbles Head and Oxwich Bay) in the Bristol Channel, U.K. between February, and August 2024. Crabs were assessed for the...

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Published: Swansea University, Wales, UK 2025
Institution: Swansea University
Degree level: Master of Research
Degree name: MRes
Supervisor: Rowley, A. F., and Davies, C. E.
URI: https://cronfa.swan.ac.uk/Record/cronfa69872
Abstract: This study reports on the prevalence, intensity, and species identification of digenean trematode infections in shore crabs (Carcinus maenas) found at two intertidal survey sites (Mumbles Head and Oxwich Bay) in the Bristol Channel, U.K. between February, and August 2024. Crabs were assessed for the presence and intensity of trematode infections by the microscopic examination of the hepatopancreas. The metacercariae species identification resulted from the combined use of morphological and PCR-based methods, specifically the 28S rDNA gene. Encysted metacercariae presented in two distinct forms, spherical and asymmetrical, which were shown to be Microphallus similis and M. primas, respectively. A high prevalence and intensity of M. similis metacercariae was found in shore crab populations from both locations throughout the duration of the study. Conversely, M. primas metacercariae were only identified in a limited number of crabs and at low infection intensities during June and August sampling. No cellular host immune responses were observed.Binomial logistic regression models revealed size and colouration to be significant factors in trematode presence at Oxwich Bay only. Additionally, larger/older shore crabs were found to harbour more metacercarial cysts, with larger metacercariae observed in crabs from Mumbles Head. Overall, the findings of this study highlight the widespread prevalence of M. similis infections in shore crab populations at both intertidal survey sites, with notable size and location-specific variations in infection intensity. Additionally, the results underscore the importance of conducting a long-term study to better understand the seasonal dynamics of M. similis and M. primas infections in shore crabs.
Item Description: A selection of content is redacted or is partially redacted from this thesis to protect sensitive and personal information.
Keywords: Crabs, Carcinus maenas, trematodes, Microphallidae, Microphallus similis, Microphallus primas
College: Faculty of Science and Engineering

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