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

By

Komeda, Sota
Adachi, Kenta
Ohtsuka, Susumu

Type

Article

Date of Publication

2021

Original Publication

ZooKeys

Volume

1038

Pages

179--194

Subjects

Arietelloidea , Calanoid copepods , Colonization , hyperbenthos , molecular phylogeny , Nansei Islands

Contributed by

Pensoft Publishers

Language

English

Published by

Sofia, Bulgaria Pensoft Publishers

Identifiers

DOI: https://doi.org/10.3897/zookeys.1038.63170

 

Abstract

A new species of the continental shelf hyperbenthic genus Pilarella is described, the first from the Indo-Pacific. This is the second species of Pilarella known, and the first description of a male in the genus. The new species is easily distinguished from other species of Pilarella (P. longicornis) based on: (1) short caudal rami, approximately 1.5 times longer than wide; (2) 2 setae on the mandibular endopod; (3) 6 setae on the maxillular coxal epipodite; and (4) in the female, a short left antennule reaching the posterior border of the genital double-somite. The new diagnosis of Pilarella differs from Metacalanus in the separation of ancestral segments IX–XII and XIV–XV of the antennule, and the presence of 5–6 setae on the maxillular praecoxal arthrite. Pilarella is also separated from Metacalanalis based on the absence of a seta on the third ancestral segment of the antennary exopod, the symmetry of legs 1–3, the presence of a medial basal seta on the female leg 5, and 2 lateral exopodal spines on the female leg 5. A molecular phylogenetic analysis of some representative genera of the family Arietellidae, including the present new species, recovers two arietellid clades (Metacalanus- and Arietellus-clades) as in previous studies. Dichotomous keys for the genera of Arietellidae and the species of Pilarella are included.