Lanassicola dorsilobatus, Boxshall & O’Reilly & Sikorski & Summerfield, 2019

Boxshall, Geoff A., O’Reilly, Myles, Sikorski, Andrey & Summerfield, Rebecca, 2019, Mesoparasitic copepods (Copepoda: Cyclopoida) associated with polychaete worms in European seas, Zootaxa 4579 (1), pp. 1-69 : 48-51

Lanassicola dorsilobatus gen. et sp. nov.

Type Material: Holotype ♀ from Proclea graffii (Langerhans, 1884) , 6160 Skjerstadfjorden, Stn H 2-4 (67.23486°N, 15.3628°E), depth 245 m, 10 September 2013; collected by A. Sikorski; NHMUK Reg. No. 2015.3001 . Paratype ♀ from P. graffii, Codfarmers, Mørkvedbukta Stn Dyp 2-2 (67° 16.528’N, 14° 33.207’E), depth 56 m, 15 July 2009; collected by A. Sikorski; NHMUK Reg. No. 2015.3002 .

Additional material: 1♀ from Leaena abranchiata (M. Sars, 1865) , Buktodden FFH, Stn S 1-A (66.30828°N, 13.43095°E), depth 170 m, 26 March 2003; collected by A. Sikorski; NHMUK Reg. No. 2015.3003 .

Differential diagnosis. Adult female ectosoma dorsoventrally flattened, about 3.3 times longer than wide; comprising indistinctly separated cephalothorax and elongate postcephalic trunk ( Fig. 21A, B ); mean body length 1.61 mm, ranging from 1.53 to 1.68 mm. Cephalothorax with paired frontal lobes, paired lateral lobes and median hemispherical dorsal lobe. Frontal lobes directed anterolaterally, unarmed, probably representing antennules. Lateral lobes conspicuously expanded dorsally ( Fig. 21A ); small paired processes present on ventral surface ( Fig. 21B ) near base of each lateral lobe. Stalk narrow, connecting to bulla inside host. Posterior margin of ectosoma expanded to form small median lobe bearing anal slit ( Fig. 21C ). Posterolateral corners rounded, bearing paired genital apertures ventrally. Egg sacs multiseriate.

Paired antennae originating anterior to stalk in oral region ( Fig. 21B ); antennae directed medially. Antenna 2- segmented ( Fig. 21D ); proximal segment unarmed, distal segment with paired apical adhesion lobes. Maxilla located posterolateral to stalk; comprising robust proximal segment densely ornamented with spinules on posterior surface ( Fig. 21E ) and distal segment bearing paired apical pads.

Male unknown.

Etymology. The name of the new species, dorsilobatus , alludes to the gross morphology of the cephalothorax of the female which carries a distinct median hemispherical lobe on the dorsal surface.

Remarks. This species can be readily distinguished from its congeners by the gross morphology of the cephalothorax. It has paired antennulary lobes on the frontal margin like both of its congeners and it has paired anterolateral lobes as in L. bilobatus gen. et sp. nov., but these are absent in the type species, L. arcticus gen. et sp. nov. It differs from L. bilobatus gen. et sp. nov. in the possession of a conspicuous dorsal lobe on the cephalothorax which is lacking in the latter. This is also a much smaller species, ranging from 1.53 to 1.68 mm in body length: its congeners have an adult female body length of 2.79 mm in L. bilobatus gen. et sp. nov. and 2.19 mm in L. arcticus gen. et sp. nov.

The female lies in a deep longitudinal groove in the host, with its anterior end pointing back towards the host’s posterior end, as in the type species. Both hosts, Proclea graffii , the type host, and Leaena abranchiata , belong to the subfamily Terebellinae . The known depth range of the parasite is 56 to 245 m.

Figures

FIGURE 21. Lanassicola dorsilobatus gen. et sp. nov. female. A, habitus, dorsal view; B, head region, ventral view showing location of antennules, antennae and maxillae relative to stalk; C, posterior region of trunk, ventral view showing paired genital apertures; D, antenna; E, maxilla. Scale bars: A, 0.5 mm, B–C, 200 µm, D–E, 25 µm.