Ceratomyxa hemitriptera, 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 : 312-313

Ceratomyxa hemitriptera sp. n. ( Figs 1I–O , 5D–E ; Table 1)

This organism was incorrectly marked as Ceratomyxa hemitripteri 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 or disporous; mature spore large and strong spore with a smooth surface and a clearly distinguished sutural line, one binuclear sporoplasm and two equal spherical polar capsules positioned anteriorly; 83.0 ± 3.3 (80.0–88.9) in thickness, 9.2 ± 0.3 (8.8–9.5) in length, posterior angle slightly concave to straight (162–170°); two smaller spherical polar capsules positioned anteriorly in a plane perpendicular to the sutural line, 4.8 ± 0.2 (4.0–5.0) in diameter, polar filament 114.0–132.0 in length; sporoplasm with one binuclear located posteriorly in spore cavity; coelozoic.

Host and site of infection: Gall bladder of Hemitripterus villosus Pallas, 1811 .

Type locality: Coastal waters of the Yellow Sea, off Qingdao (36°08′N, 120°43′E) of the Yellow Sea. Salinity about 32‰, water temperature about 13°C.

Prevalence: Of the four fish examined, one was infected (25%).

Date of sampling: May 27, 1998.

Host symptom: No symptom.

Type material: The holotype, on an air-dried slide stained with Giemsa (Coll.: No. qd-19980527a), and a paratype slide stained with Giemsa (Coll.: No. qd- 19980527b), were deposited at the Collection Center of type-specimens, Chongqing KLAB, Chongqing Normal University , China .

Etymology: The species name recalls the host from which this species was originally isolated.

Description: Plasmodia were irregular in shape, and contained different stages of developing spores. Plasmodia at an earlier stage of development usually appeared to be an amoeba with one finger-like pseudopod, ca. 43.0 × 13.0 in size; the late stage of the trophozoites (plasmodia) exhibited a peripheral layer of hyaline non-granular ectoplasm and thick granular endoplasm (Plane 12, figure 5), enclosing one or two developing spores; in vivo cells always showed a monosporous or disporous plasmodium ( Figs 1K–L, N–O , 5D–E ), measuring 42.0 × 15.6 µm in size. Spore large, body of mature spores straight or bent appreci- ably in shape from a sutural view; sutural line straight and distinct; shell valves thin-walled barrel-shaped and slightly tapering to round tips with a smooth surface; spore cavity with binucleated sporoplasm which is often finely granulated; posterior angle slightly concave to straight (162–170°); two polar capsules spherical, of about equal size and located anteriorly in a plane perpendicular to the sutural line ( Fig. 1I–J ), polar filament length 114.0–132.0 µm. No mucous envelope evident around the spore. The measurements of the spores are given in Table 1 (n = 25).

Comparison and comments: Considering the morphology of the spores, the new organism resembles C. streptospora Davis, 1917 , C. robusta Fujita, 1923 , C. inversa Meglitsch, 1960 and C. tenuis Fujita, 1923 . Comparing with these species, the new one can be easily differentiated. C. robusta possesses wider spores and smaller polar capsules than our species; the spores of C. streptospora Davis, 1917 from the gall bladder of Chaetodipterus faber Broussonet, 1782 , were only half the size of the new species ( Davis 1917, Kudo 1919), while the dimensions of the spore for C. inverse is smaller than that of new species. The spore of C. tenuis Fujita, 1923 from the gall bladder of Hippoglossus stenolepis Schmidt, 1904 is similar to our species both in length and in the sizes of the polar capsules ( Fujita 1923), but the thicknesses of the spores are very different ( Table 2). While C. spectabilis Dogiel, 1948 has been reported to parasitize Hemitripterus villosus from the Japanese Sea, our species obviously differs from C. spectabilis Dogiel, 1948 in having an straight spore with a straight and distinct sutural line, thin-walled barrel-shaped shell valves with smooth surface. To sum up the above discussion, this species should be designated as a new member of Ceratomyxa .

Figures

Fig. 1. Schematic illustrations of three myxosporean species. A–E – Sphaerospora sebasta sp. n.; A – mature spore from a frontal view; B–C – spore viewed from the perspective of the capsule; D – spore from a sutural view; E – spore from an oblique sutural view; F–H – Ceratomyxa sebastisca sp. n., showing mature spores with coarse sporoplasm; I–O – Ceratomyxa hemitriptera sp. n.; I–J – mature spore from a lateral view; K–L – plasmodium with one mature spore; M–N – early stage plasmodium with one developing spore; O – plasmodium with one developing spore from a capsule view. Scale bars: 10 µm.

Fig. 5. Microphotographs of myxosporean species. A–B – Sphaerospora sebasta sp. n.; C – Ceratomyxa sebastisca sp. n.; D–E – Ceratomyxa hemitriptera sp. n.; F–H – Ceratomyxa kareus sp. n.; I–J – Ceratomyxa lomi sp. n. Scale bars: 10 µm.