Terebella, Linnaeus, 1767

Bharathidasan, Veeraiyan, Sarathy, Palanivel Partha, Murugesan, Perumal & Nogueira, João Miguel De Matos, 2021, New records for associations between peritrich protozoan ciliates (Ciliophora, Sessilida) and polychaete worms (Annelida) from off the southeastern coast of India, Zootaxa 5071 (4), pp. 492-504 : 497

1. Terebella (Annelida, Terebelliformia) and Epistylis sp.1 (Ciliophora, Sessilida)

Most if not all specimens of Terebella sp. collected at Vellar estuary were severely infested with ciliate epibiont protozoans Epistylis sp.1 . The ciliates were found all over the worms’ bodies, on the buccal tentacles, lips, branchiae and dorsal and ventral body surfaces, but with clear preference for grooved regions on the body wall, such as between neuropodia and along the mid-ventral groove ( Fig. 2A–C ), possibly because these regions are more sheltered. Partially contracted individuals of Epistylis sp.1 are 52.56 µm long, in average, in 50 individuals measured, and were only found in solitary form ( Fig. 2A–E ), ~300–350 individuals per worm, in average, in 10 worms counted. Nevertheless, the tissues of the worm did not show lesions of any type at attachment points, suggesting that the ciliates are more likely ectocommensals, rather than parasites.

Figures

FIGURE 2. Specimens of Epistylis sp.1 attached to Terebella sp. (A–C) SEM images, (D, E) light microscopy images. (A). Epistylis sp.1. on the dorsal surface of the anterior end of the worm; (B). Epistylis sp.1 on the ventral surface of the anterior end of the worm; (C). Epistylis sp.1, on grooves between neuropodia; (D–E). Epistylis sp.1 attached to buccal tentacles of Terebella sp. White arrow points to folds of the posterior region of zooid, yellow arrow points to projecting tube formed by constriction of the peristomial lip, red arrow points to macronucleus.