Ceratomyxa simplex, Zhao & Al-Farraj & Al-Rasheid & Song, 2015

Zhao, Yuanjun, Al-Farraj, Saleh A., Al-Rasheid, Khaled A. S. & Song, Weibo, 2015, Data on Ten New Myxosporean Parasites (Myxozoa, Myxosporea, Bivalvulida) from the Yellow Sea, China, Acta Protozoologica 54 (4), pp. 305-323 : 320

Ceratomyxa simplex sp. n. ( Fig. 4H–L ; Table 2)

This organism was incorrectly marked as Ceratomyxa simplex Zhao and Song, 2003 in the monograph “Pathogenic Protozoa in Mariculture” ( Song et al. 2003), which has not been described as a new species in that book. Thus, according to ICZN, the species should be an invalid name, hence, we “re-establish” and “re-describe” this form here.

Diagnosis: Trophozoites monosporous; 15–17 × 11–12 µm in size; mature spore crescent-shaped from a sutural view, sutural line straight and clear; anterior edge of spore is parallel to and almost symmetrical with the posterior edge of spore;14.5 ± 1.5 (13–17) in thickness, 5.7 ± 0.5 (5.0–6.3) in length, posterior angle concave (112–165°); two pyramidal polar capsules positioned in a plane perpendicular to the sutural line, 2.1 ± 0.2 (2.0–2.5) × 1.9 ± 0.1 (1.5–2.0) in size.

Type host and site of infection: Gall bladder cavity of Chirolophis japonicus Herzenstein, 1890 (Syn. Azuma emmnius Jordan and Snyder, 1902).

Type locality: Coastal waters off Qingdao (36°08′N, 120°43′E), China. Salinity about 32‰, water temperature about 12–13°C .

Prevalence: Of the nine fish examined one was infected (11%).

Date of sampling: June 22, 1998.

Host symptom; Unknown.

Type material: The holotype, on an air-dried slide stained with Giemsa (Coll. No.: qd-19980622a), and a paratype slide stained with Giemsa (Coll.: No. qd- 19990622b), were deposited at the Collection Center of type-specimens, Chongqing KLAB, Chongqing Normal University, Chongqing, China .

Etymology: The name “ simplex ” refers to the simple body structure of the myxosporean.

Description: Trophozoites: early stage plasmodia were not seen; later stages exhibited a developed spore, trophozoites monosporous; 15.0–17.0 × 10.6–12.0 in size ( Fig. 4K–L ). Mature spores were crescent-shaped from a sutural view, sutural line was straight and clear. The anterior edge of spore was parallel to and almost symmetrical with the posterior edge of the spore, the both ends of spore were truncated; two shell-valves were smooth and symmetry, the length of each shellvalve laterally prolonged and exceeded the axial diameter of the spore (measured from the midpoint of the suture to the most distant point of the valve). Posterior angle was concave (112–165°); two pyramidal polar capsules positioned in a plane perpendicular to the sutural line. Spore cavity is filled with a binucleated mass of sporoplasm which is often finely granulated. No mucous envelope around the spore ( Fig. 4H–J ). Measurements are given in Table 2 (n = 18).

Comparison and comments: The morphology of the myxosporean from Azuma emmnius is closely comparable to C. etroplusi Rajendran and Janardanan, 1992 from Etroplus maculates (Bloch) from Rivulats at Irin- gal and Ramanattukara in the Calicut district of Kerala, India. Both species infect the gall bladder of piscine hosts and C. simplex corresponds to C. etroplusi Rajendran and Janardanan, 1992 in having a similar body shape. The present form differs, however, from C. etroplusi according to the original description ( Rajendran and Janardanan, 1992), in having subspherical plasmodium and monosporous trophozoites, being 15.0–17.0 × 10.6–12.0 in size (vs. plasmodia with branched pseudopods, disporous trophozoites, 31.5 × 18.0 in size in the latter), and in having a different shape of spore (symmetrical crescent-shaped vs. conspicuously asymmetri- cal crescent-shaped body shape). Moreover, the present species is from a different host and different water type ( Azuma emmnius Jordan and Snyder, 1902 from sea water vs. Etroplus maculates from brackish water) ( Table 2). For these reasons the present myxosporean can be considered to be a new species and is here named Ceratomyxa simplex sp. n. on account of its simple body shape.

Figures

Fig. 4. Schematic illustrations of Ceratomyxa spp. A–G – Ceratomyxa saurida sp. n.; A–D, G – lateral view of mature spore; E – lateral view of abnormal spore; F – lateral view of immature spore; H–L – Ceratomyxa simplex sp. n.; H, J – lateral view of mature spore; I – immature spore viewed from the perspective of the capsule; K–L – plasmodia with one spore; M–T – Ceratomyxa triacantha sp. n.; M–N, P – plasmodia with two spores; O, Q – early stage plasmodia with many nuclei; R–T – sutural view of mature spores. Scale bars: 10 µm.