Ceratomyxa mennani n. sp. (Myxosporea: Bivalvulida) parasitizing the gallbladder of the dusky grouper Epinephelus marginatus (Serranidae) from Tunisian waters

Morphological and molecular characterization of Chloromyxum dasyatidis n. sp. (Myxosporea: Chloromyxidae) in the common stingray Dasyatis pastinaca (Linnaeus) from Tunisian waters (Central Mediterranean Sea)

A new species of Chloromyxum Mingazzini, 1890, C. dasyatidis n. sp., is described from the gallbladder of the elasmobranch fish Dasyatis pastinaca (Linnaeus) from the Mediterranean coast off Tunisia. Mature myxospores were subspherical measuring 13.0 ± 0.3 (12.5-13.9) µm in length, 11.3 ± 0.5 (10.2-12.2) µm in width, and 11.8 ± 0.5 (11.4-12.7) µm in thickness. Four pyriform polar capsules 4.4 ± 0.3 (4.0-4.9) µm long and 3.5 ± 0.3 (3.0-3.8) µm wide. Valves were ornamented by 5 to 7 elevated surface ridges and displayed short caudal filaments. Chloromyxum dasyatidis n. sp. had an overall prevalence of infection of 38.5%, with significant seasonal variation, being more prevalent during summer (60.0%) and autumn (70.8%). Phylogenetically, this species grouped within the Chloromyxum sensu stricto lineage, forming a small clade together with the genetically more similar species C. acuminatum and C. myolibati, both from stingray hosts.

Morphological and genetic analysis of Ceratomyxa saurida Zhao et al. 2015 and Ceratomyxa mai sp. nov. (Myxozoa: Ceratomyxidae) from the East China Sea

We describe Ceratomyxa saurida Zhao et al. 2015 and Ceratomyxa mai sp. nov. (Myxozoa: Ceratomyxidae) from the East China Sea. C. saurida was found in the gallbladders of 3/13 specimens of its type host, Saurida elongata Temminck and Schlegel 1846 (Aulopiformes). Myxospore characters were consistent with the original description to which we have added small subunit (SSU) rRNA gene data. C. mai sp. nov. was found in gallbladders of 3/13 specimens of S. elongata and 5/13 specimens of Neobythites sivicola Jordan and Snyder 1901 (Ophidiiformes). Mature myxospores of C. mai sp. nov. were crescentic in sutural view, with a deeply concave posterior angle 142.2±8.2° (125.8‒158.2°) and an arched anterior side. Shell valves were smooth and equal, 20.9±1.9 (17.3‒24.7) µm thick and 9.2±0.5 (8.1‒9.9) µm long, and joined at a straight, thin sutural plane passing between two nematocysts (polar capsules). The nematocysts were equal-sized, pyriform, 2.6±0.2 (2.4‒2.9) µm long and 2.7±0.2 (2.4‒3.3) µm wide, with their tapered ends pointed toward each other, located in the anterior third of the spore. Sequences of the SSU rRNA gene and internal transcribed spacer 1 showed that the isolates of C. mai sp. nov. obtained from S. elongata and N. sivicola were identical. The SSU rRNA gene sequence of C. mai sp. nov. was distinct from all known myxosporeans and clustered with C. saurida, and then with Ceratomyxa filamentosi Kalatzis, Kokkari and Katharios 2013, both of which also infect Aulopiformes fishes.

Morphological and molecular characterization of Ceratomyxa binhthuanensis n. sp. (Myxosporea: Ceratomyxidae) from the gall bladder of blacktip grouper Epinephelus fasciatus (Perciformes: Serranidae) in the East Sea of Vietnam

A new myxozoan species, Ceratomyxa binhthuanensis n. sp. (Myxosporea: Ceratomyxidae), was found in the gall bladder of blacktip grouper Epinephelus fasciatus (Perciformes: Serranidae) in the East Sea of Vietnam. Myxospores were observed floating free in the gall bladder of 3 out of 20 fish examined (15%). Mature myxospores were elongate and slightly crescent-shaped and measured 12.2 ± 1.3 (10.8-16.0) μm in thickness and 5.8 ± 0.6 (4.8-6.9) μm in length, with two smooth equal shell valves. The two polar capsules were spherical and equal in size, measuring 2.6 ± 0.3 (2.3-2.9) μm in diameter. The posterior angle was slightly concave, 153.7° ± 5.6° (148.9°-166.0°). Molecular analysis of SSU rDNA sequence showed that Ceratomyxa binhthuanensis n. sp. differs from other Ceratomyxa spp. available in GenBank. Phylogenetic analysis indicated that C. binhthuanensis n. sp. was closely related to three species, Ceratomyxa nolani, Ceratomyxa yokoyamai, and Ceratomyxa cutmorei, which also infect fish hosts of the genus Epinephelus.

First description of Chloromyxum squali Gleeson and Adlard, 2012 (Myxozoa) in the Mediterranean Sea in a new host Squalus blainville (Chondrichthyes: Squalidae): morphological, ultrastructural and phylogenetic data

Chloromyxum squali Gleeson and Adlard, 2012 originally described from Squalus acanthias Linnaeus, 1758 is reported for the first time from the gallbladder of Squalus blainville (Risso, 1827) caught from the eastern coast of Tunisia. In the present study, this chloromyxid was described based on morphological and ultrastructural features combined with molecular analysis of 18S rDNA. Young plasmodia were found attached to the gallbladder, while mature plasmodia and myxospores were observed floating free in the bile. Mature plasmodia were polysporic, subspherical in shape, measured 97.8 ± 0.5 µm long and 63.4 ± 0.4 µm wide. Mature myxospores were ovoid with a pointed anterior end, measuring 10.2 ± 0.5 µm long and 8.3 ± 0.5 µm wide. Two asymmetrical shell valves adhered together along an S-shaped suture line. Each valve has 5-7 elevated surface ridges parallel to suture line. A bundle of long caudal filaments extended from the basal end of shell valves. Four pyriform polar capsules equal in size, measuring 3.1 ± 0.4 µm long and 2.5 ± 0.3 µm wide, were situated at the same level in the anterior pole of the myxospore, each with a polar filament coiled in 7-8 turns. Pairwise comparisons among the SSU rDNA sequences revealed significant similarity between Chloromyxum squali infecting S. acanthias with the sequence obtained in this study. Phylogenetic analysis revealed that C. squali clustered in the clade of Chloromyxum species infecting the gallbladder of marine Chondrichthyes. Chloromyxum squali showed a seasonal variation of prevalence with significantly higher prevalence noted in summer and in autumn and absence of infection in winter.

Zschokkella epinepheli n. sp. (Myxosporea: Myxidiidae) infecting the gallbladder of the white grouper Epinephelus aeneus (Serranidae) from Tunisian waters

A new coelozoic myxosporean species, Zschokkella epinepheli n. sp., collected from the gallbladder of the white grouper Epinephelus aeneus (Perciformes: Serranidae) from the bay of Bizerte, Tunisia, is described based on morphological and molecular characteristics. Myxospores and plasmodia were observed floating free in the bile. Mature plasmodia were polysporic and subspherical in shape, measuring 85.0-94.0 μm long and 70.0-82.0 μm wide. Mature myxospores were ovoid in valvular view, measuring 10.0 ± 1.7 (8.0-11.0) μm in length and 7.0 ± 0.3 (6.6-7.5) μm in width. Polar capsules were pyriform and equal in size, measuring 3.0 ± 0.2 (2.8-3.6) μm in length and 2.3 ± 0.3 (1.8-2.7) μm in width. Myxospore valves had 12-14 longitudinal striations. Based on the small subunit rDNA, the new species Z. epinepheli n. sp. differs from all other Zschokkella species for which there is a DNA sequence deposited in GenBank. Phylogenetic analysis revealed that Z. epinepheli n. sp. clustered in the marine subclade of Zschokkella species within the biliary tract IV clade. This is the first report of a Zschokkella species from the gallbladder of an epinephelin fishes.