Robbea seahi sp.nov.

ZooBank registration: http://zoobank.org: urn:lsid:zoobank.org: act: 5B3D9322-A4D5-44FB-8B55-B45FC258C271.

Type location: Yakata, Okinawa, Japan; shallow subtidal sand. Coordinates: 26.4926 N, 127.842126 E.

Type material: One holotype (NHMW-ZOO-EV-M-5871), three paratypes male (NHMW-ZOO-EV-M-5872/1-3). Collection date: Dec. 2017. Collector: B. Seah.

Other material: Several specimens in J.A. Ott collection.

Etymology: The species is dedicated to Brandon Seah, marine scientist who collected the worms.

Description: With the characters of the genus. Measurements see Supporting Information, Table S2.

Small (<6 mm long) and slender species (Figures 10 and 11). Males with prominent, enlarged GSO in ventral post-pharyngeal region, protruding as 17–20 bumps. Subcephalic setae almost as long as cephalic setae. Cephalic capsule short, extending over about 50% of corpus. Corpus occupying about 25% of pharynx length, isthmus long (>60%), very small, round, glandular bulbus. Small somatic setae distributed over body. Tail conical with pointed tip. Symbiotic bacteria slender rods, 3,7 × 1.5 µm.