Emschermannia ramificata Borisanova 2016, sp. nov.

Emschermannia ramificata sp. nov.

(Figs 1–4)

Material examined. Holotype: ZMMU No. Uk-7, from central plateau of Kara Sea, 73°43.05' N, 79°23.38' E, 29 m, September–October 2011. Paratypes: ZMMU No. Uk-8), five specimens from the same locality. Other material: ZMMU No. Uk-9, three specimens from central plateau of Kara Sea, 73°10' N, 79°51' E, 25 m. ZMMU No. Uk-10, three specimens from central plateau of Kara Sea, 74°17' N, 79°37' E, 33 m. ZMMU Uk-11, two species from St Anna trough of Kara Sea, 77º12' N, 78º07' E, 119 m. ZMMU Uk-12, four species from St Anna trough of Kara Sea, 78º00' N, 74º53' E, 364 m, all September–October 2011.

Etymology. Latin ramus, branch, and facio, make, alluding to the unusual branched attachment structure of this species

Description. Solitary, with single zooids attached to substratum by basal plate and short or long, usually branched, pseudostolons. Total length of body from end of stalk to base of tentacles 250–300 µm (Table 1). Calyx length 160–200 μm, width at broadest part 130–160 μm. Calyx laterally compressed, with 8–10 tentacles, facing distally or slightly distofrontally in contracted state. Tentacle crown of calyx with developing larvae directed distofrontally. Sensitive papillae absent. Stomach rounded without lobes. No cuticular septum between calyx and stalk (Fig. 2D). Stalk shorter than calyx, slightly extended at base, 80–110 μm long, 30–60 μm wide. Attachment structure an expanded basal plate from which sterile appendices (pseudostolons) grow out in different directions; these structures unequal, ranging from 50 to 600 μm long and 25–40 μm wide. Long pseudostolons usually growing from basal plate in opposite directions (Figs 2C, 4C); short pseudostolons growing from basal plate in any direction, also originating from long pseudostolons. Basal plate may be reduced in some specimens such that zooid arises only from creeping pseudostolon (Fig. 4B). In other specimens basal plate can attain diameter> 100 μm. Two unusual specimens of Emschermannia were found among solitary forms (Fig. 3). Each of these specimens had two zooids arising from one attachment structure. In one case, both zooids arising from the basal plate, and in the other case one zooid arose from the basal plate and the other zooid from a pseudostolon.

Reproduction. Buds formed from median frontal area of calyx, several (up to 8) buds (Fig. 4A) are developing simultaneously, with new buds lying above older ones. Large buds with 8 tentacles and well-developed foot with foot gland and foot groove (Fig. 4D). Buds attached to the calyx by tip of foot, which is turned away from substratum. Developed buds 150–160 μm long, calyx length c. 80 μm, calyx width c. 60 μm.

Larvae. Some specimens with larvae developing in atrium (Figs 2B, 4B). Up to 5 embryos at different stages observed in one calyx.

Ecology. Emschermannia ramificata is an epibiont on the polychaete Aglaophamus malmgreni. Specimens of E. ramificata are most often in the groove between notopodia and neuropodia but they can also be found on the parapodium itself and on the body surface beneath parapodia. The number of specimens on a single polychaete varies from several zooids to several dozen zooids, and separate specimens of A. malmgreni bear more than 50 entoprocts. Usually entoprocts are on parapodia of the anterior part of the worm’s body, but when the quantity of epibionts is great they also occur in the middle part of the body.