Lanassicola bilobatus gen. et sp. nov. Type material: Holotype ovigerous ♀ from tube of Lanassa nordenskjoeldi Malmgren, 1866, Argus Miljø, Stn 2-2 (67° 08.515’N, 15° 24.902’E), depth 245 m, 12 May 2011; collected by A. Sikorski; NHMUK Reg. No. 2015.466. 2 allotype ♂♂ attached to Holotype female; same locality and habitat data. Differential diagnosis. Adult female ectosoma (Fig. 19A) elongate, about 3.5 times longer than maximum width, connected to small bulla inserted within host, via short stalk. Ectosoma dorsoventrally flattened, about 2.79 mm in length and with a maximum width of about 0.8 mm anteriorly, tapering to a width of about 0.5 mm posteriorly. Cephalothorax with paired frontal and anterolateral lobes. Frontal lobes directed slightly anterolaterally, unarmed, probably representing antennules. Anterolateral lobes expanded dorsally (Fig. 19B). Posterior margin of ectosoma (Fig. 19C) expanded to form median lobe bearing anal slit. Paired genital apertures located ventrally at posterolateral extremities of ectosoma. Cement glands irregularly curved (Fig. 19C), up to 0.6 mm in length. Egg sacs multiseriate, about 3.76 mm in length (Fig. 19A). Paired antennae located anterior to stalk originating in oral region (Fig. 19B); directed medially. Antenna 2- segmented (Fig. 19D); proximal segment unarmed, distal segment with paired corrugated adhesion pads. Maxilla (Fig. 19E) located posterolateral to stalk; comprising robust proximal segment; distal segment with paired corrugated pads. Male sac-like (Fig. 20A), pear-shaped with narrow anterior end and broad posterior extremity, 110 µm in length, with maximum width of 82 µm. Paired antennules located anteriorly on lateral margin, paired antennae located on frontal margin either side of mid-line (Fig. 20A). Antennules unsegmented (Fig. 20B), tapering, armed with 5 setae along anterior margin and apex. Oral region modified into funnel-like structure located anteriorly on ventral surface. Oral funnel ovoid in ventral view (Fig. 20C), enclosing paired spinulate pads. Maxillae similar in structure to those of female, located posterior to oral funnel on ventral surface (Fig. 20C). Male producing paired cylindrical spermatophores (Fig. 20D) about 30 µm long, each with short tubule. Etymology. The name of the new species, bilobatus, alludes to the presence of two pairs of lobes on the frontal margin of the cephalothorax. Remarks. The adult female of Lanassicola bilobatus gen. et sp. nov. can be distinguished from L. arcticus gen. et sp. nov. by the bilobate frontal margin of the cephalothorax in the former compared to the unilobate condition of the latter. The paired lobes of L. bilobatus gen. et sp. nov. are interpreted as representing antennulary and anterolateral lobes. The body of L. bilobatus gen. et sp. nov. is also larger, so the body length of the adult female is 2.79 mm, compared to 2.19 mm in the type species, and the trunk is thicker and more robust. The adult male of L. bilobatus gen. et sp. nov. is sub-triangular in dorsal view compared to the rounded sac-like trunk of male L. arcticus gen. et sp. nov. The ectosoma was detached from the host and so there is no information on the form of the endosoma, or on the positioning on the host.

Published as part of Boxshall, Geoff A., O'Reilly, Myles, Sikorski, Andrey & Summerfield, Rebecca, 2019, Mesoparasitic copepods (Copepoda: Cyclopoida) associated with polychaete worms in European seas, pp. 1-69 in Zootaxa 4579 (1) on page 48, DOI: 10.11646/zootaxa.4579.1.1, http://zenodo.org/record/2637477