Vivgottoia, Kim & Sikorski & O’Reilly & Boxshall, 2013

Kim, Il-Hoi, Sikorski, Andrey, O’Reilly, Myles & Boxshall, Geoff A., 2013, Copepods associated with polychaete worms in European seas, Zootaxa 3651 (1), pp. 1-62 : 41

Vivgottoia n. gen.

Diagnosis. Body vermiform, elongate, cylindrical, and composed of cephalosome, first to fifth pedigerous somites, genital complex and 1-segmented abdomen. Rostrum shield-like and directed posteroventrally. Antennule 5- segmented, with few setae. Antenna 2-segmented; distal segment perpendicular to proximal segment and inserted on outer margin of proximal segment. Labrum simple, with strongly tapering posterior margin. Mandible with 1 distal blade articulated at base. Maxillule with 2 medial and 2 outer setae. Maxilla 2-segmented; distal segment claw-like. Maxilliped 3-segmented; terminal segment forming strong claw. Legs 1–4 biramous, positioned ventrolaterally and visible in dorsal view of body, lacking intercoxal sclerite, with unsegmented rami; exopod bearing 1 or 2 setae; endopod foliaceous, unarmed. Leg 5 rudimentary, represented by 2 setae.

Etymology. The generic name is in memory of the late Dr. R. V. (Viv) Gotto (Queen’s University, Belfast) in recognition of his many contributions to the study of copepods associated with invertebrates.

Type species. Vivgottoia garwoodi n. gen. et n. sp. by original designation.

Remarks. The elongate vermiform body, the ventrolaterally displaced legs 1–4, and the unsegmented abdomen in the female of Vivgottoia n. gen. suggest a possible affinity with the Serpulidicolidae . However, the new genus cannot be placed within the Serpulidicolidae because of the vestigial leg 5, the prehensile maxilla, the segmented metasome, and the characteristic form of the antenna and legs 1–4. Unlike the new genus, the genera of the Serpulidicolidae are all ectoparasites of polychaetes.

Like Vivgottoia n. gen., copepods of genus Entobius Dogiel, 1908 , the sole genus of the family Entobiidae Ho, 1984 , are endoparasites of polychaetes and have ventrolaterally displaced legs 1–4, a rudimentary leg 5, and a prehensile maxilliped in the female. However, Vivgottoia n. gen. cannot be assigned to the Entobiidae because the members of this family invariably have elongate rami of legs 1–4 and a simple 3-segmented, antenna, plus they lack a maxilla.

The antenna of Vivgottoia n. gen. is the most outstanding feature of the genus. The two-segmented condition of this appendage, with the distal segment displaced laterally to the proximal segment, has not been observed in any representative of the nereicoliform families ( Nereicolidae , Serpulidicolidae , Entobiidae , Spiophanicolidae , and Clausiidae ), all of which comprise copepods living in association with polychaete hosts. The antenna of the new genus probably functions as an attachment organ; the proximal segments of left and right antennae directed towards each other to form pincers ( Fig. 23F ).

In the Clausiidae , Nereicolidae and Serpulidicolidae the key limbs for securing attachment to the host are the maxillae and/or maxillipeds, at least in females. In these taxa the distal tip of both appendages is blunt and provided with a distinct spinulose pad. In the female of the new genus both the maxillae and maxillipeds terminate in claws, and only the maxilla has a patch of spinules that may represent a vestigial spinulose pad, as found in several families.

The mandible of the new genus terminates in a single blade that articulates with the segment. It closely resembles the mandible of the clausiid genera Sheaderia n. gen. and Boreoclausia n. gen. The derived form of this mandible is strongly suggestive of a relationship with the family Clausiidae , but in view of the numerous differences we can only tentatively place Vivgottoia n. gen. in the Clausiidae .

Figures

FIGURE 23. Vivgottoia garwoodi n. gen. et n. sp., holotype female. A, habitus, dorsal; B, urosome, dorsal; C, rostrum, anteroventral; D, antennule; E, antenna; F, antennae and mouthparts, ventral; G, labrum, ventral; H, mandible; I, maxillule; J, maxilla; K, maxilliped. Scale bars: A, 0.2 mm; B, 0.1 mm; C, D, F, J, K, 0.02 mm; E, G–I, 0.01 mm.