Ceratomyxa dactyloptena, Yang & Yang & Chen & Yang & Zhou & Ma & Liu & Zhao, 2025

Ceratomyxa dactyloptena sp. nov.

Type host.

Oriental flying gurnard Dactyloptena orientalis Cuvier, 1829 .

Type locality.

Coastal waters near Sanya   GoogleMaps , South China Sea ( 18°14'32"N, 109°30'31"E).

Infection site.

Gallbladder.

Prevalence.

42.9 % (6 / 14). The infected hosts included 5 adults and 1 subadult.

Date of sampling.

15 August 2016.

Type material.

Syntypes (mounted in glycerin-alcohol-formalin; accession numbers SY 2016081501) and DNA samples (accession numbers SY 2016081501 dna) were deposited in collection center of Animal Biology Key Laboratory of Chongqing Education Commission of China, Chongqing, PR China.

Pathology.

The parasite was found in the gallbladder of the host with no obvious pathological sign being observed. The damage to the host is unknown.

Etymology.

The species epithet dactyloptena refers to the genus of the type host, Dactyloptena.

Description.

Immature myxospores at the vegetative stage were observed, displaying irregular shapes with two faintly discernible shell valves, and two polar capsules were distinctly visible (Fig. 2 A View Figure 2 ). Mature myxospores were crescentic in sutural view, characterized by a slightly concave posterior margin and arched anterior, typical of the genus Ceratomyxa . The two shell valves were smooth, with one valve slightly longer than the other, joined by a thin, straight sutural line passing between the two polar capsules. Polar capsules were pyriform, equal in size, with their tapered ends directed toward the anterior top of the myxospore (Fig. 2 B, C View Figure 2 ). Mature myxospores ( N = 30) measured 30.0 ± 1.3 (27.2–32.8) µm in thickness and 6.4 ± 0.4 (5.7–7.0) µm in length, with a posterior angle of 152.9 ± 3.7 ° (146.2–158.9 °). Two polar capsules ( N = 60) were 2.9 ± 0.3 (2.3–3.3) µm in length and 2.4 ± 0.3 (1.7–2.8) µm in width, with polar filaments coiled in 3–4 turns.

Remarks.

Ceratomyxa dactyloptena sp. nov. is the only ceratomyxid identified from D. orientalis and morphologically resembling C. drepanopsettae Awerinzew, 1908 , C. macapaensis Bittencourt, 2022 , and C. orientalis Dogiel, 1948 . Ceratomyxa drepanopsettae can be readily distinguished from C. dactyloptena sp. nov. by its substantially longer and thicker myxospores (Table 1 View Table 1 ). Its polar capsules are also larger, and notably spherical, contrasting with the pyriform polar capsules observed in C. dactyloptena sp. nov. (Table 1 View Table 1 ). Additionally, C. drepanopsettae was described from Pleuronichthys cornutus Temminck & Schlegel, 1846 collected in the Yellow Sea, off Qingdao, China, whereas C. dactyloptena sp. nov. infects D. orientalis and was identified from the South China Sea, off Sanya, China. Ceratomyxa macapaensis , a freshwater species and differs significantly from the new species by its smaller myxospores and smaller polar capsules (Table 1 View Table 1 ). Although both species possess pyriform polar capsules, their environmental origins clearly separate them: C. macapaensis was discovered in the Piririm River ( Brazil), parasitizing Mesonauta festivus Heckel, 1840 , while C. dactyloptena sp. nov. is marine and occurs in Chinese coastal waters. Ceratomyxa orientalis possesses considerably longer and thicker myxospores compared to the new species (Table 1 View Table 1 ). Its polar capsules are also slightly larger (Table 1 View Table 1 ). Furthermore, C. orientalis was described from Sardinops sagax Jenyns, 1842 in the Sea of Japan ( Russia) and clearly differs in both host and locality from C. dactyloptena sp. nov.

Among all valid Ceratomyxa species recorded in China, C. qingdaoensis Zhao, Al-Farraj, Al-Rasheid & Song, 2015 , C. saurida Zhao, Al-Farraj, Al-Rasheid & Song, 2015 , and C. hemitriptera Zhao, Al-Farraj, Al-Rasheid & Song, 2015 share some morphological resemblance to C. dactyloptena sp. nov. However, the new species can be reliably distinguished from these species based on a combination of spore dimensions, polar capsule characteristics, host, and locality data. The myxospore length of C. dactyloptena sp. nov. is nearly identical to that of C. qingdaoensis , yet the latter possesses markedly greater spore thickness (Table 1 View Table 1 ). The polar capsule length of C. qingdaoensis is comparable to that of the new species, but its polar capsules are spherical, whereas those of the new species are pyriform (Table 1 View Table 1 ). Additionally, C. qingdaoensis exhibits a larger posterior angle than C. dactyloptena sp. nov. and occurs in a different host ( Argyrosomus argentatus Houttuyn, 1872 ) and locality (Yellow Sea, off Qingdao, China). Ceratomyxa saurida can be distinguished from C. dactyloptena sp. nov. by its larger myxospores and longer polar capsules (Table 1 View Table 1 ). Similar to C. qingdaoensis , the polar capsules of C. saurida are spherical, contrasting with the pyriform capsules of the new species. The posterior angle of C. saurida is slightly more variable and overlaps partially with that of the new species, but its host ( Saurida elongata Temminck & Schlege, 1846) and distribution (Yellow Sea, off Qingdao, China) are distinct (Table 1 View Table 1 ). Ceratomyxa hemitriptera is readily separated from C. dactyloptena sp. nov. by having considerably thicker myxospores and larger polar capsules (Table 1 View Table 1 ). The myxospore length is also greater (Table 1 View Table 1 ). As with the other two species, C. hemitriptera has spherical polar capsules, while those of C. dactyloptena sp. nov. are pyriform. Moreover, C. hemitriptera infects a different host ( Hemitripterus villosus Pallas, 1814 ) and is found in a different geographic location (Yellow Sea, off Qingdao, China).