Ceratomyxa

Laamiri, Sayef, 2017, Myxosporea (Cnidaria: Myxozoa) infecting the saddled seabream Oblada melanura (L. 1758) (Teleostei: Sparidae) and the painted comber Serranus scriba (L. 1758) (Teleostei: Serranidae) in Tunisia, Zootaxa 4269 (1), pp. 61-100 : 64-66

Ceratomyxa sp. 1 ex O. melanura

Host: Oblada melanura Linnaeus, 1758 saddled seabream ( Perciformes : Sparidae ).

Locality: Mediterranean off Tunisia, Bay of Bizerte (37°20’ N, 9°53’ E).

Site of infestation: Within gall bladder.

Prevalence: The overall prevalence is 36 % (36/100). The infection rate is distributed as following, 05/2012: 30% (3/10); 06/2012: 33.3% (5/15); 07/2012: 46.7% (7/15); 08/2012: 50% (5/10); 04/2013: 20% (5/25); 05/2013: 44% (11/25) ( Table 10).

Mean intensity: 129±58 spores/20µl bile/infected fish (++++++) ( Table 10).

Vouchers: Digitized photos of spores are deposited in the parasitological collection of the Museum National d’Histoire Naturelle (MNHN), Paris, Coll. No. ZS 135.

Morphological description. Vegetative stages. Coelozoic trophozoïtes (n = 30 live trophozoites) floating freely in the bile at different stages of maturation, Plasmodia are disporous, spherical to sub-spherical and measuring 25.4±1.8 (21.6–28.3) µm in length and 29.1±2.5 (25.7–33.8) µm in width ( Figs. 1 A–F). Each plasmodium contains two identical spores with very refractive granules ( Figs. 1 A–E). Pansporoblast pseudopodia are not detected ( Figs. 1 A–F).

Myxopores. Spores typical for the genus Ceratomyxa (n = 60 fresh spores). Mature spores are transversely elongate and narrowly crescent-shaped with slightly convex anterior margin and concave posterior one in sutural and lateral views ( Figs. 1 F–H, 7A,B) measuring 7.9±0.7 (7.2–9.0) µm in length and 27.7±2.6 (24.4–31.0) µm in thickness. They are cylindrical in the apical view and measuring 7.3±0.8 (6.4–8.4) µm in width (n = 10) ( Figs. 1 E, 7C). Posterior angle is slightly concave to slightly convex 155.4±6.8 (140–164°). The two shell valves, with rounded ends, are unequal in size, with one tapering to a significantly greater degree than the other ( Figs. 1 G, 7A). The pointed one measuring 19.5±1.1 (17.7–21.6) µm while the more rounded one 14.3±1.1 (12.2–16.1) µm. In the lateral view, they are ovoid and superficially smooth with bluntly rounded ends ( Figs. 1 H, 7B). The suture line is straight, non protruding. Homogenous Sporoplasms with numerous sporoplasmosomes do not fill the spore cavity and contain two nuclei, each one occupies one side. Rarely, both nuclei occur at one side ( Figs. 1 B, G, 7A–C). Two capsulogenic nuclei are situated beneath or sometimes between the polar capsules ( Figs. 1 B, G). The two polar capsules are spherical, equal in size and measuring 3.2±0.46 (2.7–3.6) µm in length equaling 40.5% of spore length and 3.2±0.46 (2.7–3.6) µm in width (n = 30), They are positioned medially in anterior part of spore in sutural and lateral views ( Figs. 1 A–H, 7A,B) and in the central plane in apical view ( Figs. 1 E, 7C). The polar filament forms four to five turns arranged along the longitudinal axis of the capsule.

Taxonomic affinities. Since Ceratomyxa sp. 1 discriminates by having two unequal shell valves, we exclude from comparison all Ceratomyxa spp. that possess equal ones. According to the best of our knowledge, no Ceratomyxa species with unequal valves has been described from Mediterranean sparids. However, C. globulifera Thélohan, 1895 , C. inaequalis Doflein, 1898 (cited from Kudo 1920) and C. cretensis Kalatsis, Kokkari & Katharios, 2013 from Mediterranean off France, Italy and Greece respectively, have unequal valves. These species infects unrelated hosts (Table 1). C. globulifera and C. cretensis differ from Ceratomyxa sp. 1. in shape and size. C. inaequalis is distinguished by having smaller spores and polar capsules than those of the recent species (Table 1).

Eight more species, with unequal valves, have been recorded from diverse type of fishes elsewhere ( Eiras 2006): C. undulata Davis, 1917 , C. intexua Meglitsch, 1960 , C. platichtys Fujita, 1923 , C. allantoidea Gaevskaya & Kovaleva, 1984 , C. etroplusi Rajendran & Janardanan, 1992 , C. sympetala Aseeva, 1992 , C. fistulariae and C. syacii Kpatcha, Diebakate, Faye & Toguebaye, 1996 (Table 1). Morphologically, spores of C. undulata are significantly shorter compared to our species (6 µm vs 7.9 µm). Although C. intexua and C. sp. 1 are similar in shape, their measurements differ significantly. C. platichtys separates from the recent species by having longer and wider spores and polar capsules. The spores of C. allantoidea are shorter in length but thicker, with smaller and pyriform polar capsules. However, both spores and polar capsules of C. sympetala are so larger. The species under study is relatively similar in shape of the spores to that of spores of C. etropusi and C. fistulariae , however their dimensions have not matching. Besides, the polar capsules of C. etropusi are smaller and pyriform while those of C. fistulariae are significantly larger than those of the current species. The spores of C. syacii are longer but with smaller polar capsules. Therefore, taking into account the mentioned above differences in morphology, dimensions, host and area of distribution, the present myxosporean Ceratomyxa sp. 1 is designated as a different species, not previously identified neither in O. melanura nor in the Mediterranean Sea.

TABLE]. Comparison of the spore measurements of the present Ceratomyxa sp.] ex O. melanura with taxonomic affinities species (measurements are in µm). Abbreviations: SL, Spore Length; ST, Spore Thickness; SW, Spore Wiđth; PCL, Polar Capsule Length; PCW, Polar Capsule Wiđth; ND, Not Determineđ.

Species Host (s) Locality Spore Polar capsule

SL ST SW PCL PCW

Figures

FIGURE 1. Photomicrographs of Ceratomyxa sp. 1 from the gall bladder of Oblada melanura. (A – E) Disporic sub-spherical to spherical plasmodia (p) containing each one two identical spores surrounded with vary refractive granules (g), Notice the presence of two capsulogenic nuclei (cn) and numerous sporoplasmosomes (spp). (F) Fresh smear contains disporic plasmodia (p) and Mature spores (s). (G) mature spore in sutural view showing the spherical polar capsules (pc), the straight suture line (sl), the sporoplasmic nuclei (sn), the capsulogenic nuclei (cn) and the unequal shell valves. (H) mature spore in lateral view. Scale bar = 20 µm in F; 10 µm in A – E, G – H.