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 : 67-69

Ceratomyxa sp. 2 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 13 % (13/100). The frequency of infection is distributed as following, 05/2012: 0% (0/10); 06/2012: 0% (0/15); 07/2012: 20% (3/15); 08/2012: 30% (3/10); 04/2013: 12% (3/25); 05/ 2013: 16% (4/25) ( Table 10).

Mean intensity: 70.1±18.4 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 134.

Morphological description. Vegetative stages. Coelozoic trophozoïtes (n = 30 live trophozoïtes) are floating freely in the bile of the gall bladder without existing of any type of pseudopodia. Plasmodia are disporous, globular in shape and measured 20.8±3.5 (17.0–24.2) µm in length and 18.7±1.8 (16.5–20.2) µm in width ( Fig 2 A–C). Each plasmodium contains two identical spores and clear endoplasm, sometimes pale with few refractive granules and inner generative cells ( Figs. 2 A–C).

Myxospores. Spores typical for the genus Ceratomyxa (n = 60 fresh spores). Mature spores are crescentshaped with anterior margin concave and posterior convex one in sutural view ( Figs. 2 D–I) small in size, measuring 5.6±0.2 (5.4–6.0) µm in length and 14.6±0.9 (13.0–15.6) µm in thickness (n = 30). They are cylindrical in apical view and measuring 5.1±0.3 (4.7–5.4) µm in width (n = 6) ( Fig. 7 F). Posterior angle is slightly concave to slightly convex 152±14 (126–172°). The two shell valves, with rounded ends, are equal in size smoothly ovoid in lateral view ( Figs. 2 D–I, 7E). The suture line is straight, visible between valves but not conspicuous. An homogenous sporoplasm occupy most of spore cavity with numerous sporoplasmosomes. Two sporoplasm nuclei are rather small, stained symmetrically and sometimes are migrating both in one side of the shell valves ( Figs. 2 C,D, G, 7D–F). One capsulogenic nucleus is observed and presented below the polar capsule ( Fig. 2 I). The two polar capsules are sub-spherical to pyriform and measuring 2.2±0.3 (1.9–2.7) µm in length equaling 39.5% of spore length and 1.9±0.3 (1.5–2.4) µm in width (n = 30), they are positioned medially in anterior part of spore in sutural and lateral views ( Figs. 2 D–I, 7D–E) and centrally of spore cavity in apical view ( Fig. 7 F). The polar filament wounds into three to four turns, slightly oblique to the longitudinal axis of the capsule.

Taxonomic affinities. After the demise of 42 Leptotheca species to Ceratomyxa on the basis of morphometric similarities and locality in the host tissues (Gunter & Adlard 2010), several species from the Mediterranean Sea, have worth to be compared to Ceratomyxa sp. 2: C. agilis (previously Leptotheca agilis ) Thélohan, 1892, C. hepseti (previously L. hepseti ) Thélohan, 1895, C. lubati (Syn. L. chromis ) Lubat, Radujkovic, Marques & Bouix, 1989, C. sparusaurati Sitjà-Bobadilla, Palenzuela & Alvarez-Pellitero, 1995 and Ceratomyxa sp. 2 ex Sparus aurata Alama-Bermejo, Raga & Holzer, 2011 (Tables 2,5).

Based on spore morphology, the spores of C. agilis are bigger in length and smaller in thickness. The spores of C. elongata are much bigger in all levels than those of current species. C. hepseti has a larger spores. The polar capsules of C. lubati are bigger compared to those of our form. The recent species differentiates from both C. sparusaurati and C. sp 2 ex. S. aurata by having a pyriform polar capsules. Furthermore, their spores have a posterior end more concave compared with the slightly concave slightly convex one of the present species. Besides, spores and polar capsules of C. sp 2 ex. S. aurata have a large dimensions ( Table 5).

In other areas amongst the world, the current species is compared to 11 representatives of the genus Ceratomyxa infecting marine fishes: C. informis (syn. L. informis ) Auerbach, 1910, C. declivis C. faba and C. pinguis (formerly L. pinguis ) Meglitsch, 1960, C. coelorhyncha (formerly L. coelorhyncha ) Yoshino & Noble, 1973, C. buri Yokoyama & Fukuda, 2001 , C. cottoidii Reed, Basson, Van As & Dyková, 2007 , C. cutmorei Gunter & Adlard, 2009 , C. ernsti and C. jonesi Gunter, Whipps & Adlard, 2009 and C. reidi Gunter, Burger & Adlard, 2010 ( Table 2).

C. informis and C. pinguis are only similar in form to the present species but no measurements are matched between all of them. For C. declivis , the polar capsules are more ovoid and subspherical. Besides, according to Meglitsch (1960), the anterior margin of C. declivis was convex in sutural view, curving smoothly over the suture line and its trophozoïtes were characterized by pseudopodia-like lobopodia which are lacking at the present Species Host (s) Locality Spore Polar capsule

SL ST SW PCL PCW Ceratomyxa sp. 2 (Present Oblada melanura Bay of Bizerte ( Tunisia) 5.6 (5.4/6) 14.6 (13/15.6) 5.1 2.2 1.9 stuđy) (4.7/5.4) (1.9/2.7) (1.5/2.4). agilis Thélohan (1892) Dasyatis pastinaca Međiterranean anđ (6/7) (11/12) ND ND ND

Tyrrhenian coasts

. hepseti Thélohan (1895) Atherina hepsetus Off France (7/8) (12/15) ND ND ND. informis Auerbach (1910) Merlangius merlangus North Sea 9.8 19.1 ND 3.6 3.6 (9/12) (15/21) (2.5/4) (2.5/4). declivis Meglitsh (1960) Cyttus novaezelandiae Pacific Ocean (New 5.9 14.4 5.6 2.4 2 Zealanđ) (5.1/6.8) (13.5/15.2) (5.1/6.2) (1.7/2.2) (1.7/2.2)

. faba Meglitsch (1960) Caulopsetta scapha Pacific Ocean (New 6.2 12.7 6.4 2.4 2.4 Zealanđ) (5.6/6.7) (10.7/14.1) (6.1/7.0) (2/3.1) (2/3.1)

. pinguis Meglitsch (1960) *Peltorhamphus Pacific Ocean (New 9.7 16.4 9.2 2.9 2.9 novaezeelandiae Zealanđ) (8.3/10.8) (13.7/18.6) (8.3-9.8) (2.4/3.9) (2.4/3.9) Arnoglossus scapha

. coelorhyncha Yoshino anđ Coelorhinchus off Irelanđ 6.7 11.34 ND 2.01 2.01

Noble, 1973 coelorhinchus (6/8) (9/13) (1.5/3) (1.5/3)

. lubati Lubat et al. (1989) Chromis chromis off France 6 14 ND 3 2.75

(5.5/7) (12.5/15)

. buri, Yokoyama & Fukuđa Seriola quinqueradiata Japan 6.5 14.3 ND 2.4 2.4

2001) (5.5/7.5) (11/16.5) (2/3) (2/3)

. cottoidii Reeđ et al. (2007) Clinus cottoides South Africa 7.1 18.2 ND 2.7(2.3/3) 2.4 (6.5/8) (17/22) (2/3)

. cutmorei Gunter & Ađlarđ Epinephelus fasciatus GBR ( Australia) 7 16.1 ND 2.4 2.3 2009) (5/8.5) (12/21.5) (1.5/3) (1.5/3). ernsti Gunter et al. (2009) Sillago ciliata GBR ( Australia) 5.76 11.94 ND 1.66 1.58

(4.67/6.84) (9.47/14.79) (1.3/2.13) (1.3/2). jonesi Gunter et al. (2009) Pseudolabrus GBR ( Australia) 5.1 12.99 ND 1.92 1.81

guentheri (4.1/6.08) (11.17/16.45) (1.55/2.3) (1.42/2.29)

. reidi Gunter et al. (2010a) Chaetodon vagabundus GBR ( Australia) 6.8 17.5 6.5 2.1 2

(5.8/7.5) (14.3/20.7) (6.0/7.0) (1.7/2.4) (1.7/2.5)

) Original host.

correspondent studied species. The spores of C. faba are less wider and its polar capsules are spherical. Moreover, the posterior angle of this species is strongly concave. The recent finding species separates from C. coelorhyncha by having a broader spores with a pyriform polar capsules. The polar capsules of both C. buri and C. acanthopagri are spherical. Besides, the spores of C. acanthopagri and C. cottoidii are bigger in length and thickness. The spores ranges of C. sp. 2 and all species C. cutmorei , C. ernsti , C. jonesi overlap however their polar capsules are the most spherical. The average thickness and width of spores of C. reidi are larger than those of the recent species and its trophozoïtes are monosporous whereas those of the current species are ordinarily disporous and therefore they are two distinct species. No available details concerning the vegetative stages of C. cutmorei , C. ernsti and C. jonesi or their development into the host organ for further comparison. In light of these differences with closely related species, the present myxozoan Ceratomyxa sp. 2 should be established as a different species, has been recorded for the first time in O. melanura from the Mediterranean Sea.

Figures

FIGURE 2. Photomicrographs of Ceratomyxa sp. 2 from the gall bladder of Oblada melanura. (A – C) Globular to subspherical disporic plasmodia (p), notice the presence of immature spores (is) within plasmodium in B and the migration of two sporoplasmic nuclei (sn) in one side of pre – mature spore in C. (D – E) Fresh smears of mature spores. (F – H) Variable forms of mature spores in sutural view showing the pyriform polar capsules (pc), the suture line (sl) and an iodinophilous vacuole (v). (H) Mature spore in lateral view presented one capsulogenic nucleus (cn) below the polar capsule. Scale bar = 10 µm.

FIGURE 7. Line drawing of Myxozoan species infecting the saddle seabream Oblada melanura from the Bay of Bizerte, Tunisia. (A – C) Variable forms of Ceratomyxa sp. 1 in sutural view (A), in lateral view (B), in apical view (C). (D – F) Variable forms of Ceratomyxa sp. 2 in sutural view (D), in lateral view (E), in apical view (F). Scale bar = 10 µm.