Asymmetron lucayanum: How many species are valid?

Lucie Subirana,Stephanie Bertrand,Viviana Farstey,Hector Escriva

doi:10.1371/journal.pone.0229119

Abstract

The cephalochordates amphioxus or lancelets are benthic marine animals representing the earliest divergent evolutionary lineage within chordates. Although amphioxus are present in most of the world’s tropical and temperate oceans, only about thirty different species grouped into three different genera, Branchiostoma, Epigonichthys and Asymmetron have been described. In the genus Asymmetron, only two species have been characterized, although for one of them, A. lucayanum, several cryptic lineages exist. In this work we have sequenced and analyzed the mitogenome of an A. lucayanum population previously described in the Red Sea. The phylogenetic study using this complete mitogenome as well as the analysis of COI gene sequences of several individuals of this Red Sea population show that the Red Sea population is a new cryptic species. We propose to call this new species Asymmetron rubrum.

Highlights

Cephalochordates are filter feeding benthic marine animals living in tropical and temperate waters of the oceans worldwide
These authors discussed the possibility of the existence of a third genus, Asymmetron, but they could not find any synapomorphy characterizing all species in Epigonichthys exclusive of E. lucayanus
The phylogenetic tree reconstructions show a close evolutionary relationship between the populations of the West-central Pacific and the Atlantic areas whereas the West-central Pacific and the Indo-West Pacific populations are sympatric in the Pacific area

Summary

Introduction

Cephalochordates (i.e. amphioxus) are filter feeding benthic marine animals living in tropical and temperate waters of the oceans worldwide They are representatives of the most basally divergent group of the chordate phylum, which includes urochordates and vertebrates [1, 2]. Poss and Boschung regrouped these 29 species in only two genera, Branchiostoma and Epigonichthys, whose major morphological difference is the presence of symmetrical gonads in Branchiostoma and asymmetrical dextral gonads in Epigonichthys. These authors discussed the possibility of the existence of a third genus, Asymmetron, but they could not find any synapomorphy characterizing all species in Epigonichthys exclusive of E. lucayanus (synonym of Asymmetron lucayanum).

Objectives

Methods

Results

Conclusion