A redescription of Syncarpa composita (Ascidiacea, Stolidobranchia) with an inference of its phylogenetic position within Styelidae

By

Hasegawa, Naohiro
Kajihara, Hiroshi

Type

Article

Date of Publication

2019

Original Publication

ZooKeys

Volume

857

Pages

1-15

Subjects

Chordata , COI , Phylogeny , Sea of Okhotsk , taxonomy , Urochordata

Contributed by

Pensoft Publishers

Language

English

Published by

Sofia, Bulgaria Pensoft Publishers

Identifiers

DOI: https://doi.org/10.3897/zookeys.857.32654

 

Abstract

Two species of styelid colonial ascidians in the genus Syncarpa Redikorzev, 1913 are known from the northwest Pacific. The valid status of the lesser known species, Syncarpacomposita (Tokioka, 1951) (type locality: Akkeshi, Japan), is assessed here. To assess the taxonomic identity of S.composita, we compared one of the syntypes and freshly collected topotypes of S.composita with a syntype of S.oviformis Redikorzev, 1913 (type locality: Ul’banskij Bay, Russia). Specimens of S.composita consistently differed from the syntype of S.oviformis in the number of oral tentacles, the number of size-classes of transverse vessels, and the number of anal lobes. In this paper, S.composita is redescribed as distinct from S.oviformis, and its phylogenetic position inferred within Styelidae based on the 18S rRNA and cytochrome c oxidase subunit I gene sequences. In our phylogenetic tree, Syncarpa formed a well-supported clade together with Dendrodoa MacLeay, 1824. In Syncarpa and Dendrodoa, a single gonad is situated on the right side of the body, which is unique among Styelidae, and thus can be a synapomorphy for this clade.