Monnioticopa planicoxa, Kim & Boxshall, 2021

Kim, Il-Hoi & Boxshall, Geoff A., 2021, Copepods (Cyclopoida) associated with ascidian hosts: Ascidicolidae, Buproridae, Botryllophilidae, and Enteropsidae, with descriptions of 84 new species, Zootaxa 1, pp. 1-286 : 262-265

Monnioticopa planicoxa gen. et sp. nov.

( Figs. 173 , 174 )

Type material. Holotype ♀ (MNHN-IU-2014-21579, dissected and mounted on a slide) from Asaj ẚrus sp.; North of Lubang Island, the Philippines, ESTASE 2 cruise, RV “Jean Charcot”, Stn CP 02 (14°05.4´N, 120°02.5´E), depth 2050 m, Métivier coll., 14 November 1984.

Etymology. The specific name is derived from the Latin plan (=flat) and cçxa, in reference to the flat, discoid coxa of swimming legs.

Description of female. Body ( Fig. 173A ) eruciform, with thin exoskeleton, consisting of cephalosome, 5-segmented trunk, and short genitoabdomen. Body length 3.74 μm; maximum width about 1.2 mm (across third pedi- gerous somite). Cephalosome ( Fig. 173C ) wider than long (0.49× 1.04 mm), with distinct posterodorsal margin, as wide as first pedigerous somite. First to fourth pedigerous somites well-defined from one another, but their tergites obscure or absent; trunk bearing 3 pairs of subcircular tubercles on ventral surface between first and second pedigerous somites ( Fig. 173C ). Genitoabdomen segmentation uncertain due to post-fixation shrinkage. Caudal rami ( Fig. 173B ) broad, oval, about 1.8 times longer than wide (243×135 μm), narrow proximally; armed with 1 major and 4 small, setule-like setae; major distal seta 87 μm long, 2 of small setae positioned at 44 and 70% of ramus length, other 2 small setae positioned distally.

Rostrum ( Fig. 173C ) small. Antennule ( Fig. 173D ) small, 201 μm long, tapering, 4-segmented, articulation between proximal 2 segments incomplete; armed with 0, 5, 2, and 7 small setae on first to fourth segments, respectively. Antenna ( Fig. 173E ) 4-segmented, including short first segment; proximal 3 segments unarmed; fourth segment slightly longer than wide, with 1 small seta plus 1 small tubercle distally.

Labrum ( Fig. 173F ) with convex posterior margin, angular posterolateral corners, and ornamented with 2 patches of minute granules on ventral surface. Mandible ( Fig. 173G ) represented by weakly curved, powerful claw. Maxillule ( Fig. 173H ) bilobed; larger inner lobe tipped with 2 unequal, naked spines (45 and 26 μm long, respectively); small outer lobe tipped with 1 naked seta. Maxilla ( Fig. 173I ) 2-segmented; broad proximal segment unarmed; distal segment slender, 3.35 times longer than wide (87×26 μm), armed with 3 setae (2 distally and 1 at proximal 45% of segment length). Maxilliped absent.

Legs 1-4 biramous, with 2-segmented protopod ( Fig. 174 A-D); coxa extremely inflated, discoid; basis with small seta on outer margin; leg 1 additionally with inner distal seta ( Fig. 174B ) on basis. Exopods of legs 1 and 2 unsegmented, armed with 2 setae (1 on lateral margin and 1at laterodistal corner) and 1 apical, triangular claw. Exopods of leg 3 ( Fig. 174D ) and leg 4 same in segmentation and armature, 2-segmented; proximal segment with 1 spine at laterodistal corner; distal segment with 1 seta at laterodistal corner and 1 apical, triangular claw. Endopods short, wider than long, armed with 2 naked setae distally; laterodistal seta slightly longer than mediodistal seta in legs 1-3, but almost equal in length in leg 4.

Leg 5 ( Fig. 174E ) lamellate, wider than long (370×674 μm), slightly narrowed in proximal third; armed with 4 minute setae (2 on medial margin, 1 near mediodistal corner, and 1 on distal margin). Leg 6 ( Fig. 174F ) probably represented by 3 cusps on genital operculum.

Male. Unknown.

Remarks. Mçnnẚçtẚcçpa planẚcçxa gen. et sp. nov. differs from other species of Mçnnẚçtẚcçpa gen. nov. in having a simple maxilla lacking the inner lobe, a 4-segmented antennule, and better developed setation on the exopods of swimming legs. Despite these differences, there are significant synapomorphies that allows the new species to be accommodated in the same genus. These synapomorphies include the claw-like, modified mandible, the 3- or 4- segmented digitiform antenna, the broad caudal rami armed with 1 major and several vestigial setae, and the bilobed maxillule.

It is noticeable that MK planẚcçxa gen. et sp. nov. shares with the type species of the genus, the expanded, flattened coxa of the swimming legs, but the scale of the expansion is greater in M. planẚcçxa gen. et sp. nov. than in the type species .

Figures

FIG. 173. Mçnnẚçtẚcçpa planẚcçxa gen. et sp. nov., female. A, habitus, dorsal; B, caudal rami, dorsal; C, cephalosome and first pedigerous somite, ventral; D, antennule; E, antenna; F, labrum; G, mandible; H, maxillule; I, maxilla. Scale bars: A, 0.5 mm; B, 0.1 mm; C, 0.2 mm; D-I, 0.05 mm.

FIG. 174. Mçnnẚçtẚcçpa planẚcçxa gen. et sp. nov., female. A, leg 1; B, basis and rami of leg 1; C, leg 2; D, leg 3; E, leg 5; F, genital aperture. Scale bars: A, C, D, 0.1 mm; B, 0.05 mm; E, 0.2 mm; F, 0.02 mm.