Mytilicola Intestinalis (Copepoda: Cyclopoida): A Ten Year Survey of Infested Mussels in a Cornish Estuary, 1978–1988

Abstract

Fifty-five samples, each of fifty mussels, have been examined over a ten year period from a population in the estuary of the River Lynher, Cornwall, England for the incidence of infestation with the parasitic copepod Mytilicola intestinalis Steuer. A previously reported pattern of two overlapping generations of the copepods each year is shown to have persisted in a regular way over the ten years. Perturbations to the rhythm of this cycle can occur as a result of unusual weather conditions and an example is documented of a cold spring affecting the following autumn's recruitment phase of the copepod population cycle. Intensity of infestation reaches levels higher than any reported for Mytilus, yet the cycle continues without apparent effect on the host population which is evidently capable of sustaining the infestation indefinitely. While slight effects of crowding of the parasites on the growth attained by adult female copepods could be detected in mussels under 60 mm, larger hosts were capable of supporting maximum parasite burdens. In even the smallest size classes of hosts sampled, mortality of hosts due to infestation could not be demonstrated. It is concluded that in every respect Mytilicola intestinalis exhibits the features of a commensal rather than a parasite capable of harmful effects on its host.

Symbionts and diseases of farmed mussels Mytilus galloprovincialis throughout the culture process in the Rías of Galicia (NW Spain)

“…The effects of this copepod on the host is controversial. It does not seem justified to blame the copepod for large-scale mortalities among mussels (Davey & Gee 1988, Davey 1989, but it may cause loss of condition to the host (Theisen 1987). Limited histopathological changes in the mussel gut associated with the copepod were detected in our study.…”

High mortality of mussels in northern Brittany – Evaluation of the involvement of pathogens, pathological conditions and pollutants

“…Regarding Mytilicola sp., Brienne (1964) and Blateau (1989) observed weight loss in French mussels infested with this copepod at the end of winter and early spring (breeding period); the mortality it caused was related to the decrease in mollusc vitality. Nevertheless, in most cases, despite a high infestation intensity reported in English and Spanish mussels, it is evident that the host population can sustain the infestation indefinitely (Davey, 1989;Robledo et al, 1994). Again, our results were consistent because the highest prevalence of this copepod was recorded in St. Brieuc and no abnormal mortalities were observed over the period at this site;…”

Mussel histopathology: effects of season, disease and species

“…In addition to its role in providing a 'baseline' measure of health, histopathology has been employed to investigate the changes related to PAH, PCB and heavy metal exposure in mussels (Sunila 1984, Auffret 1988, Kluytmans et al 1988, Marigómez et al 2006. However, since histopathology has also been used to investigate the effects of disease and parasite infestation in wild mussel populations (Rasmussen 1986, Davey 1989, Figueras et al 1991, Robledo et al 1994, Powell et al 1999, Svärdh 1999, care must be taken when using histopathology as a biomarker of contaminant exposure per se. In this respect, histopathology can be considered as a means to provide supporting information for measures (biomarkers) that specifically aim to assess historic exposure to, or effect of, a contaminant.…”