Description and molecular phylogeny of a new species of Phoronis (Phoronida) from Japan, with a redescription of topotypes of P. ijimai Oka, 1897

Abstract

We describe Phoronis emigi sp. n. as the eighth member of the genus based on specimens collected from a sandy bottom at 33.2 m depth in Tomioka Bay, Amakusa, Japan. The new species is morphologically similar to P. psammophila Cori, 1889, but can be distinguished from the latter by the number of longitudinal muscle bundles in the body wall (56–72 vs. 25–50 in P. psammophila) and the position of the nephridiopores (situated level with the anus vs. lower than the anus in P. psammophila). Using sequences of the nuclear 18S and 28S rRNA genes and the mitochondrial cytochrome c oxidase subunit I (COI) gene, we inferred the relationship of P. emigi to other phoronids by the maximum likelihood method and Bayesian analysis. The analyses showed that P. emigi is closely related to P. hippocrepia Wright, 1856 and P. psammophila Cori, 1889. We describe the morphology of the topotypes and additional material for P. ijimai Oka, 1897. Neither our morphological observations of P. ijimai, nor the phylogenetic analyses based on 18S and COI sequences, contradicts that P. vancouverensis Pixell, 1912 is conspecific with P. ijimai, a synonymy that has long been disputed.

Oogenesis in the viviparous phoronid, Phoronis embryolabi

“…Having a basalmost position in all recently published trees (Hirose et al, ; Temereva & Chichvarkhin, ; Temereva & Neklyudov, ) P. ovalis shows the first example of independently evolving tube brooding and a shift to nonfeeding larva (Figure ). In the generally similar molecular trees by Hirose et al (2014) and Temereva and Chichvarkhin (), species of the genus Phoronopsis that are mostly broadcasters, have the basal position pointing to the ancestral reproductive pattern.…”

Hox gene expression during the development of the phoronidPhoronopsis harmeri

“…ovalis (60), which is the sister species to all remaining phoronids (62)(63)(64), suggesting that the actinotrocha was not even present in the most recent ancestor of all Phoronida, but instead appeared during the evolution after split between Ph. ovalis and the remaining phoronids.…”

“…1C) (60,61). The only exception from this pattern is Phoronis ovalis, which is a sister group to the remaining phoronids (62)(63)(64) and which develops through the creeping slug-like larva (60). After few days of development the active larva settles and acquires a smooth hemispherical shape (60).…”

Phoronida

“…Primary oocytes are arrested at metaphase and released from the ovary to fuse with activated V-shaped sperm (Zimmer 1964(Zimmer , 1991Reunov and Klepal 2004 ). Male pronuclei have been found in the coelomic oocytes of Phoronopsis harmeri (Rattenbury 1953 ) and Phoronis ijimai (currently = vancouverensis ;Zimmer 1991 ;Hirose et al 2014 ). There is one largely undocumented report of external fertilization in Phoronis muelleri (Herrmann 1986 ), but this observation requires more data.…”