Epistylis wuhanensis Wang, Zhou, Guo, and Gu, 2017

Nitta, Masato, 2022, First Japanese Record of Epistylis wuhanensis (Ciliophora: Epistylididae) Attached to Lernaea cyprinacea (Copepoda), with a List of Epistylis Species Attached to Metazoans in Japan, Species Diversity 27 (1), pp. 61-69 : 63

Epistylis wuhanensis Wang, Zhou, Guo, and Gu, 2017 ( Figs 1 , 2 ; Supplemental Movies 1–3)

Epistylis wuhanensis Wang, Zhou, Guo, and Gu, 2017: 396– 400 , figs 1–5.

Peritrich ciliates: Nagasawa and Nitta 2019: 148, 149, fig. 1C, D.

Description. Colony up to 1 mm in height and comprised of less than 60 zooids, branched dichotomously with secondary or more stalks ( Fig. 2A ); span between first and secondary stalks relatively long, occupying half to twothirds of the total length ( Fig. 2A ). Stalks non-contractile (Supplemental Movie 1), transversely wrinkled weakly when the stalk curved ( Fig. 2A ), with longitudinal striations on the surface ( Fig. 1A ), 11.3–25.9 (15.7, n=11) width in branched regions. Expended zooid elongate bell-shaped to elliptical ( Figs 1B , 2A–D , Supplemental Movies 2, 3), 163.1– 220.3 (190.1, n=15) length in vivo, 128.0–181.9 (150.2, n= 6) length in fixed specimens; in vivo, half of specimens widest close to the single-layered, thin peristomial lip 41.6–56.1 (47, n=15) in width, 36.1–56.9 (46.3, n=15) in width at the mid-point; peristomial lip in fixed specimens 36.2–54.7 (44.7, n=6) wide, widest at the mid-point (47.1–64.0, 55.7, n=6); average length to width ratio in vivo 3.3–5.3 (4.1): 1 (n=15) at mid-point, 2.1–3.5 (2.7):1 (n=6) in fixed specimens. Contracted zooid ovoid ( Fig. 1C ). Peristomial disk mammilla-shaped, 11.2–13.4×14.7–18.4 (12.1×16.1, n=5), surrounded by adoral zone of membranelles ( Figs 1A , 2B, D ). Macronucleus lying in the middle or upper thirds of cell, commonly C-shaped or sometimes J-shaped ( Fig. 2C, D ). Cytopharynx lying in upper third of expended zooid ( Fig. 2B ). Contractile vacuole between macronucleus and peristomial lip ( Fig. 2B ). Aboral trochal band lying in lower third to fourth of zooid ( Figs 1B, C , 2B–D ). Pellicle with circular transverse ( Fig. 1B, C, E ); transverse striations distributed equally, 138–164 (149.2, n=5) striations between peristome and aboral trochal band, 92–102 (95.6, n=5) between aboral trochal band and scopula. Longitudinal fibers continually extending across the body, from peristome to scopula ( Fig. 2C, D ).

Infundibular polykineties lying in upper third of expended zooid ( Fig. 2D ). Haplokinety and polykinety parallel, both making ca. 1.6–1.8 turns around peristome, then entering infundibulum ( Fig. 2F ). Germinal kinety parallel with haplokinety in infundibular region, curving anteriorly to form half-circle anterior to infundibular polykinety 2 (P2), then crossing to infundibular polykinety 1 (P1) and P2 ( Fig. 2E ). Each infundibular polykinety consists of three rows of kinetosomes in lower third of infundibulum ( Fig. 2E ); P1 longest, consisting of three rows, extending laterally, then bending downward, extending shortly, and terminating at end of infundibulum. P2 almost parallel to lateral rows of P1, terminating at posterior curvature of P1. Polykinety 3 (P3) shortest, about half the length of P2, extending to the end of P2, then bending downward with P1 and terminating near the end of P1.

Deposition of specimens. MPM 21760 (mounted specimens) and MPM 21761a [preserved in 70% ethanol with L. cyprinacea (MPM 21761b)].

Sequence data. LC570274 : partial 18S rDNA (1653 bp); LC570273 : partial 18S (14 bp), complete ITS1 (140 bp), 5.8S rDNA (109 bp), ITS2, (170 bp), and partial 28S rDNA (34 bp) .

Molecular data comparison. As found through a BLAST search, the newly obtained partial 18S rDNA sequence ( LC570274 ) was identical, by original description, to E. wuhanensis with 100% coverage ( KU869709 : Wang et al. 2017) and E. cf. wuhanensis collected in the U.S.A. with 94% coverage ( MW443028 – MW443030 : Ksepka and Bullard 2021). The closest hits to the newly generated sequence of ITS1-5.8S-ITS2 ( LC570273 ) is also E. wuhanensis ( KU869710 , Wang et al. 2017, 99.79% similarity with 100% coverage), and the newly determined ITS1 sequence showed only one base deletion.

Remarks. Epistylis wuhanensis was originally described as attached to the fins of the yellow catfish Tachysurus fulvidraco (Richardson, 1846) (as Pelteobagrus fulvidraco ) ( Siluriformes : Bagridae ), and the surface of the exposed neck and trunk of L. cyprinacea , parasitizing the bluegill Lepomis macrochirus Rafinesque, 1819 ( Perciformes : Centrarchidae ) in Hubei Province, China ( Wang et al. 2017). On newly collect- ed specimens, the maximum number of zooids was 60 (vs. 30 in Wang et al. 2017); fully expanded zooids in vivo were slightly longer than those in the aforementioned records [163.1–220.3 µm (this study) vs. 90.2–175.4 µm ( Wang et al. 2017)]. Zooids in half of the living specimens were the widest at the peristomial lip, but those of the other half and fixed specimens were the widest at their mid-point. However, most measurements and morphological characteristics (the composition of the infraciliature; the position of the contractile vacuole; the form of the peristomial disk and lip; and the shape and position of the macronucleus) of the specimens collected in the present study are closely resemble to the description of Wang et al. (2017), partial 18S rDNA sequence was identical, and ITS1-5.8S-ITS2 sequence was also closely similar to the latter. The minor morphological differences of the specimens and the one base deletion of the newly determined ITS1 sequence are considered to be intraspecific variations, thus, the newly collected specimens were identified as a new country-specific record for E. wuhanensis .

Figures

Fig. 1. Scanning electron micrographs of Epistylis wuhanensis Wang, Zhou, Guo, and Gu, 2017 from Japan. A, E. wuhanensis attached to exposed cephalothorax of Lernaea cyprinacea; B, extended zooid, lateral view; C, contracted zooid, lateral view; D, extended zooid, apical view; E, scopula of extended zooid. Abbreviations: AMZ, adoral zone of membranelles; ATB, aboral trochal band; PD, peristomial disc; PL, peristomial lip; SC, scopula; ST, stalk; ZO, zooid.

Fig. 2. In vivo and protargol stained specimens of Epistylis wuhanensis Wang, Zhou, Guo, and Gu, 2017 from Japan (MPM 21760). A, Colony of zooids; B–D, extended zooid, lateral view; E, abstomal region of infraciliature polykineties; F, extended zooid, apical view. Abbreviations: ATB, aboral trochal band; AZM, adoral zone of membranelles; CV: contractile vacuole; CY, cytopharynx; G, germinal kinety; H, haplokinety; MN, macronucleus; P1–3, infundibular polykineties 1–3; PD, peristomial disc; PL, peristomial lip; Po, polykinety; SC, scopula; ST, stalk; ZO, zooid.