Pilarella Alvarez, 1985

Komeda, Sota, Adachi, Kenta & Ohtsuka, Susumu, 2021, A new species of Pilarella (Copepoda, Calanoida, Arietellidae) from the hyperbenthic layer of Japan, with a molecular phylogenetic analysis of some representative genera of the Arietellidae, ZooKeys 1038, pp. 179-194 : 179

Genus Pilarella Alvarez, 1985

Diagnosis.

Female. Cephalosome separated from first pediger. Fourth and fifth pedigers completely fused. Rostrum produced ventrally, with pair of frontal filaments disposed distally. Genital double-somite symmetrical with paired seminal receptacles and gonopores located ventrolaterally. Antennules asymmetrical, 21-segmented, ancestral segments I-IV and XXIV-XXVIII fused. Left antennule exceeding fifth pediger, approximately 1.5 times longer than right counterpart. Antenna with unarmed coxa; exopod 5-segmented, with ancestral segments II-IV, V-VII and IX-X fused, setal formula as 0, 0-0-1, 1-1-1, 1, 0-2. Mandible with row of setules on dorsal margin of gnathobase; endopod rudimentary, unsegmented, with 2 setae. Maxillule with 5-6 spines on praecoxal arthrite; coxal endite with 1 seta; coxal epipodite with 5-6 setae; proximal and distal basal endites without seta; endopod unsegmented with 2 setae; exopod with 3 setae. Maxilla with 2 setae on all praecoxal and coxal endites; basis having 1 heavily-chitinized spine [Maxilla with 2 setae on all praecoxal, coxal and basal endites; first endopodal segment having 1 heavily-chitinized spine (the homology by Ferrari and Ivanenko 2001, 2008)]. Maxilliped syncoxal endites with 0, 1, 0, and 2 setae, respectively; basis with 2 setae; first to sixth endopodal segments with 1, 4, 3, 2, 2 and 4 setae, respectively [Maxilliped praecoxal endites with 0, 1 and 0 setae, respectively; coxal endite with 2 setae; basis with 2 setae midway and 1 seta distally; first to fifth endopodal segments with 4, 3, 2, 2 and 4 setae, respectively (the homology by Ferrari and Ivanenko 2001, 2008)]. Legs 1-4 symmetrical; Seta and spine formula shown in Table 2 , but basal lateral seta of leg 4 reduced in P. longicornis . Leg 5 uniramous, 3-segmented; basis with long medial seta and short lateral seta; exopod unsegmented, with 1 lateral spine and 2 terminal spines.

Male. Body, antenna, mandible, maxillule, maxilla, maxilliped, and legs 1-4 similar to female counterparts. Antennules asymmetrical; right antennule 21-segmented, ancestral segments I-IV fused, XXIV-XXVIII partly fused, I-VIII with long tape-like aesthetascs. Leg 5 uniramous, 5-segmented; basis with lateral seta; exopod 3-segmented, proximal 2 segments with 1 lateral spine, distal segment with 2 terminal setae.

Type species.

Pilarella longicornis Alvarez, 1985 (by monotypy). Other species: Pilarella compacta sp. nov., described herein.

Remarks.

The diagnosis of Metacalanus from Ohtsuka et al. (1994) differs from Pilarella in the fusion of ancestral segments IX-XII and XIV-XV on the antennule, and the display of 0-2 setae on the maxillular praecoxal arthrite (vs. 5-6 setae in Pilarella ). The diagnosis of Metacalanalis from Ohtsuka et al. (2005) differs also from Pilarella in the presence of 1 seta on the third ancestral segment of the antennary exopod, the asymmetry of legs 1-3, the absence of medial basal seta on female leg 5, and the presence of 3 lateral exopodal spines on the female leg 5 (vs. 2 in Pilarella ).