Effect of infection by the protistan parasiteMarteilia refringenson the enzyme activity and energy reserves of oysterOstrea stentina(Payraudeau, 1826) in Tunisia

Abstract

This is the first study of the metabolic enzyme activity and energy state of the dwarf oysterOstrea stentina(Payraudeau, 1826) in Tunisia and in the Mediterranean region. The main purpose of this study was to examine the modulation of the physiological status of the oysterO. stentinadepending on the season and the presence of parasiteMarteilia refringens. The prevalence of bonamiosis and marteiliosis were established by PCR.Bonamia exitiosawas detected only in 2.91% of oysters while the prevalence ofM. refringenswas 100% (30 Ind./30) in February and 93.93% (28 Ind./30) in March. A 42–87% mortality rate was reported during the study period. Biochemical analyses were carried out to evaluate the management of the energy resources in regard to the biochemical changes of lipids and carbohydrates. The enzyme activity of pyruvate kinase (PK), citrate synthase (CS) and cytochrome c oxidase (CCO) were measured and the mean level of enzyme activity was respectively 20.31 mU mg−1protein; 12.06 mU mg−1protein and 3.59 mU mg−1protein. Carbohydrate contents ofO. stentinawere very low all year round with an average of 15.18% in dry weight, and lipid contents remain similar (11.77% in dry weight) compared with the values reported for most other temperate bivalves. Enzyme activity significantly decreased over time (P< 0.001). The energy resources of the oysterO. stentinawherein much of the energy was devoted to reproduction seem to affect the defence system.

Are Marine Heatwaves Responsible for Mortalities of Farmed Mytilus galloprovincialis? A Pathophysiological Analysis of Marteilia Infected Mussels from Thermaikos Gulf, Greece

“…Although the multiplication and transmission of the parasite are triggered at temperatures above 17 °C, many studies have indicated that the parasite seems to be abundant at mature stages also when exposed to winter temperatures [ 61 , 62 , 63 ]. The presence of protozoan parasites and specifically M. refringens has been associated many times with down-regulation in the physiology and immune responses of marine bivalves [ 60 , 64 , 65 ]. Apart from the presence of pathogenic microorganisms that affect the physiology of the marine bivalves, abiotic factors also possess a key role in the physiology of the marine organisms [ 4 ].…”

Species which may act as vectors or reservoirs of diseases covered by the Animal Health Law: Listed pathogens of molluscs

“…However, actual data on the physiological parameters are lacking from most scientific papers. In the identified reservoir species O. stentina, B. exitiosa was present in Tunisia within the temperature range of 17.1-30.0°C and a salinity of 36.2 psu to 37.8 psu (Elgharsalli et al, 2016). Available data suggest that stressing oysters using warm water (25-26°C) or hypersaline (39-40 psu) water favour B. exitiosa development (Hine et al, 2002).…”

“…However, actual data on the physiological parameters are lacking from most scientific papers. In the identified reservoir species O. stentina , B. exitiosa was present in Tunisia within the temperature range of 17.1–30.0°C and a salinity of 36.2 psu to 37.8 psu (Elgharsalli et al., 2016 ).…”