Ceratomyxa sebastisca, 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 : 309-312

Ceratomyxa sebastisca sp. n. ( Figs 1F–H , 5C ; Table 2)

This organism was incorrectly marked as Leptotheca sebastisci 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 not observed; mature spore roughly crescent-shaped, anterior margin extremely convex and posterior margin concave; ends of valves rounded with smooth surface, sutural line fine, 20.6 ± 1.6 (19.4–22.5) in thickness, 10.2 ± 0.3 (10.0–10.5) in length, posterior angle deeply concave (65–125°); two smaller spherical polar capsules positioned anteriorly in a plane perpendicular to the sutural line, 2.9 ± 0.2 (2.5–3.1) in diameter; granular sporoplasm with one binuclear posteriorly in spore cavity; coelozoic.

Host and site of infection: Gall bladder of Sebastiscus sp.

Type locality: Coastal waters of the Yellow Sea off Qingdao (36°08′N, 120°43′E) in China. Salinity about 32‰, water temperature about 14°C .

Prevalence: Only one fish was obtained and infect- ed (100%).

Date of sampling: June, 2, 1999.

Host symptom: No symptom although with high infection intensity.

Type material: The holotype, on an air-dried slide stained with Giemsa (Coll.: No. qd-19990602a), and a paratype slide stained with Giemsa (Coll.: No. qd- 19990602b), were deposited at the Collection Centre of type-specimens, Chongqing KLAB, Chongqing Normal University , China .

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

Description: Trophozoites were not observed. Mature spore was roughly crescent shaped, anterior margin extremely convex and posterior margin concave, ends of valves rounded with a straight sutural line and smooth shell surface from the sutural view ( Figs 1F–H , 5C ); posterior angle was deeply concave (65–125°). Two smaller spherical polar capsules of equal size positioned anteriorly in a plane perpendicular to the sutural line, in which the polar filament has two coils, and a granular sporoplasm with one binuclear located posteriorly in the spore cavity ( Figs 1F–H , 5C ). No mucous envelope was evident around the spore. Measurements of spores are given in Table 2 (n = 20).

Comparison and comments: In 2010, Gunter and Adlard proposed the demise of Leptotheca and reassigned all its current species to Ceratomyxa , Ellipsomyxa , Myxobolus Bütschli, 1882 or Sphaerospora on the basis of appropriate morphological and biological traits and suggested that the present organism should be transferred into the genus Ceratomyxa . According

Ceratomyxa spp. Shape and size of spore Size of polar capsule Host and location Locality Data resources

C. kareus sp. n. SP crescent, anterior margin very concave and posterior D: 4.3 ± 0.8 (3.5–5.3) Kareius icoloratus, Yellow Sea present study convex; valves with rounded ends. Zebrias zebra , (Rongcheng and

T: 43.2 ± 3.4 (38.2–46.0), gall bladder Qingdao, China)

L: 10.9 ± 0.8 (10.0–11.8)

C. platichthytis SP anterior margin very concave and posterior convex; ( Fujita, 1923) valves with rounded ends.

T: 34.5 ± 1.4 (32.9–36.8),

L: 7.7 ± 0.6 (7.1–8.2)

C. platichthytis SP anterior margin concave and posterior convex; valves ( Fujita, 1923) with rounded ends.

T: 23.4–3, L: 9.1–13 D: 3.5 ± 0.7 (2.9–4.5) Paralichthys olivaceus, Yellow Sea (Culture gall bladder in Qingdao temporarily from Korea)

PC spherical Platichthys stellatus, Oshoro and Ishikari, D : 3.9–4.5 gall bladder Japan (Sea of Japan)

Zhao and Song 2003a

Fujita 1923

C. saurida sp. n. SP arciform, anterior strongly convex and posterior strongly D: 3.6 ± 0.4 (3.0–4.0) Saurida elongata, Yellow Sea concave; valves equal with rounded ends gall bladder (Rizhao and Qingdao) T: 42.7 ± 2.5 (39.5–47),

L: 9.7 ± 0.5 (9.0–10.5)

present study

C. diloba SP very arched; anterior strongly convex and posterior Dogiel, 1948 strongly concave; valves equal with rounded ends.

T: 20, L: 7–8 PC spherical Sphaeroides rubripes, Sea of Japan ( Russia) D: 3 S. pardalis .

gall bladder quoted from Shulman 1966

C. sebastisca sp. n. Spore large, anterior arched and posterior margin strongly PC spherical Sebastiscus sp. , Yellow Sea concave, with rounded ends; D: 2.9 ± 0.2 (2.5–3.1) gall bladder (Qingdao)

T: 20.6 ± 1.6 (19.0–22.5),

L: 10.2 ± 0.3 (10.0–10.5)

C. macrospore Spore large, anterior arched and posterior slightly concave, PC spherical Sebastes viviparous, Bergen, Kristiansund population 1 with rounded ends. D: 5.2, PF: 130 gall bladder

T: 26.0, L: 13.0

C. macrospore Spore large, anterior arched and posterior slightly concave, – Sebastes marinus , North Sea, Northern population 2 with rounded ends. S. viviparus , Atlantic Ocean

T: 26.0, L: 10.5 gall bladder present study

Auerbach 1909

Kalenscher 1926

C. macrospora SP large, posterior slightly concave with rounded ends. population 3 T: 21.0–27.0, L: 12.0–15.0

C. polymorpha SP round; anterior margin arched and posterior concave, Syn. Leptotheca with rounded ends; valves equal.

polymorpha T: 18–20, L: 10–12

PC spherical Sebastiscus marmoratus, Yellow Sea D : 3.0–4.0 gall bladder (Rongcheng and Weihai)

PC pyriform Phycis phycis Off France L: 3.0, W: 2.5 (= P. mediterranea ),

gall bladder

Zhao and Song 2009

Kudo 1919 C. lovei SP anterior arched and posterior moderately to deeply con- PC spherical Sebastes serranoides, Off California Syn. Leptotheca sebasta cave; valves equal with rounded ends. D: 3.5 (3.0–4.0) gall bladder

T: 13.8 (13.0–15.0), L: 8.0 (7.5–8.5)

C. shasta Anterior margin very convex and posterior very concave; PC spherical Oncorhynchus mykiss freshwater ( USA) Noble, 1950 SP strongly arched; valves broadly rounded. D: 2.2

T: 14–17, L: 6–8

Moser et al. 1976

Noble 1950

to the ICZN Article 16 (1999), Leptotheca sebastisci Zhao and Song, 2003 remains invalid, it has been never formally reported as a new taxon. So it is the first report as a new one of genus Ceratomyxa in the present work.

With regard to the originally confused problems for genus Leptotheca and Ceratomyxa , our attention has to focus on the characters of family Ceratomyxidae . Only to clarify the relationship between Leptotheca and Ceratomyxa , we can find out the reason for establish- ment of the new species. In the family Ceratomyxidae , most members are coelozoic, generally infecting the gall bladders of marine fish hosts. The family contains four genera: Ceratomyxa Thelohan, 1892 , Leptotheca Thelohan, 1895 , Meglitschia Kovaleva, 1988 and Ellipsomyxa Koie, 2003 . The diagnosis characteristics of the genus Ceratomyxa Thelohan, 1892 is that the spores are crescent-shaped or arcuate, and with elongated shell valves generally thicker than they are long ( Lom and Dyková 2006). There are about 200 Ceratomyxa species described to date, which comprise almost 8% of the known diversity of myxosporeans ( Zhao and Song 2003 c, Eiras 2006, Lom and Dyková 2006, Reed et al. 2007, Abdel-Ghaffar et al. 2008, Heiniger et al. 2008, Gunter and Adlard 2009, Gunter et al. 2009). Recently, Gunter et al. transferred 43 species of Leptotheca into the genus Ceratomyxa ( Gunter et al. 2010) , meaning that Ceratomyxa now contains over 250 species.

The modified diagnosis for Ceratomyxa : Spores generally crescent-shaped or arcuate; shell valves conical or barrel-shaped and significantly exceeding in length half of the axial diameter of the spore. Sub-spherical or spherical polar capsules located anteriorly in a plane perpendicular to the sutural line and open close to it, but exceptionally open laterally from the central suture line. A binucleate or two uninucleate sporoplasm may fill spore cavity completely. Trophozoites monoporic, disporic or polysporic. Usually coelozoic parasites of marine fishes, exceptionally in freshwater and rarely histozoic ( Lom and Dyková 2006, Gunter et al. 2010).

Based on the comments above, all the morphological characters of the present species conforms with the modified diagnosis for genus Ceratomyxa , hence, here it is regarded as one new Ceratomyxa species in this work. Considering the morphology of the spore-body, the current organism is superficially similar to Ceratomyxa macrospora ( Auerbach 1909) , Ceratomyxa polymorpha ( Labbė 1899) , Ceratomyxa lovei ( Moser et al. 1976) and C. shasta Noble, 1950 , but the new taxon differs from C. macrospora as follows: a smaller spore-body 19.4–22.5 × 10.0–10.5 (vs. 21.0–27.0 × 12.0–15.0 for C. macrospora ), smaller polar capsules, 2.5–3.0 in diameter (vs. 3.5–5.0 in diameter for C. macrospora ); sporoplasm with granules (vs. sporoplasm fine for C. macrospora ). The new species can be distinguished from C. lovei by: a roughly crescent shaped anterior margin which is extremely convex with a concave posterior margin, (vs. anterior margin convex and posterior deeply to moderately concave for C. lovei ), the larger spore-body 19.4–22.5 × 10.0– 10.5 in size (vs. 13.0–15.0 × 7.5–8.5 in size for C. lovei ), the smaller polar capsules, 2.5–3.1 µm in diameter (vs. 3.0–4.0 µm in diameter for C. lovei ). Comparing the new organism and C. polymorpha , meanwhile, the former exhibits a thicker and smaller spore than C. polymorpha (19.4–22.5 × 10.0– 10.5 µm vs. 18–20 × 10–12 µm) and a sporoplasm with granules (vs. sporoplasm fine for C. polymorpha ). The current species differs from C. shasta in that the former exhibits a larger spore-body than C. shasta (19.4–22.5 × 10.0–10.5 vs. 14–17 × 6–8) and a larger polar capsule (2.9 ± 0.2 (2.5–3.1) in diameter vs. 2.2).

Moreover, the five Ceratomyxa species were obtained from different hosts and geographic areas: C. polymorpha from Phycis phycis off France; C. lovei from Sebastes serranoides in coastal waters off California; C.macrospora from Sebastesviviparus and S.dactylopterus in Bergen and California; from Sebastes viviparous , S. serranoides , Sebastes marinus in the North Sea and Northern Atlantic Ocean and Sebastes schlegeli , Sebastiscus marmoratus in the Yellow Sea, respectively ( Zhao and Song 2009). C. shasta , meanwhile, is a freshwater species found in Oncorhynchus mykiss in the USA. Fi- nally, our new taxon is found from Sebastiscus sp. in the Yellow Sea, China. Based on this our species is considered as a new member of the genus 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.