“Chloromyxum dasyatidis (Myxosporea: Chloromyxidae) a parasite of the common stingray Dasyatis pastinaca (L.) from Tunisian waters (7076)”

Chloromyxum dasyatidis (Myxosporea: Chloromyxidae) a parasite of the common stingray Dasyatis pastinaca (L.) from Tunisian waters

The present study, aims to describe a new marine coelozoic Chloromyxum species, based on morphological, ultrastructural, and molecular features. Phylogenetic analyses were performed for analysing the relationship of the new species with the existing marine Chloromyxum spp. from different hosts and continents. In addition, seasonal variation and the effect of host size on the prevalence of infection were evaluated.

The new species Chloromyxum dasyatidis is described from the gallbladder of the elasmobranch fish Dasyatis pastinaca (Linnaeus) from the Mediterranean coast off Tunisia. Plasmodia were polysporic (containing up to 30 myxospores) floating free in the bile. Mature myxospores were subspherical measuring 13.0 ± 0.3 (12.5–13.9) µm in length, 11.3 ± 0.5 (10.2–12.2) µm in width, and 11.8 ± 0.5(11.4–12.7) µm in thickness. The four polar capsules were pyriform measuring 4.4 ± 0.3 (4.0–4.9) µm long and 3.5 ± 0.3 (3.0–3.8) µm wide. Valves were ornamented by 5 to 7 elevated surface ridges and displayed short caudal filaments.

Phylogenetically, this species grouped within the Chloromyxum sensu stricto lineage, forming a small clade together with the genetically more similar species C. acuminatum (Lisnerová et al., 2022) infecting Rhinoptera jayakari in South Africa with 95.4% similarity, and C. myolibati (Gleeson & Adlard, 2012) infecting Myliobatis australis in Tasmania with 95% similarity.

Prevalence of infection of C. dasyatidis displayed notable seasonal fluctuation. C. dasyatidis had an overall prevalence of infection of 38.5%, with highest values recorded during autumn (70.8%), followed by summer (60.0%), spring (16%), and winter (4.5%).

The prevalence of infection of C. dasyatidis showed a slight variation in relation to host size. The comparison between the disc width size classes showed that the highest prevalence of infection 48.1% (13/27) was observed in the 28–33 cm size class, followed by the prevalence of infection 41.2% (14/34) recorded in the 34–39 cm size class, then 35.0% (7/20) recorded in the 40–45 cm size class, while the lowest rate of infection 20.0% (3/15) recorded from larger fish (46–51 cm). Nevertheless, no significant relathionship was found between host size and prevalence rates of C. dasyatidis (χ2 = 3.4, df=3, P>0.05).

1. BAHRI, Sihem, UNIVERSITY OF TUNIS EL MANAR, FACULTY OF SCIENCES OF TUNIS, Presenter
2. ELLOUMI, Amira, UNIVERSITY OF TUNIS EL MANAR, FACULTY OF SCIENCES OF TUNIS, Author
3. RANGEL, Luis F., CIIMAR, University of Porto, Matosinhos, Portugal, Author
4. QUILICHINI, Yann, University of Corsica Pascal Paoli, Corte, France, Author
5. SANTOS, Maria J., CIIMAR, University of Porto, Matosinhos, Portugal, Author