Complete mitochondrial genome of the marine polychaete, Marphysa sanguinea (Polychaeta, Eunicida)

First mitochondrial genomes of Chrysopetalidae (Annelida) from shallow-water and deep-sea chemosynthetic environments

Among Annelida, Chrysopetalidae is an ecologically and morphologically diverse group, which includes shallow-water, deep-sea, free-living, and symbiotic species. Here, the four first mitochondrial genomes of this group are presented and described. One of the free-living shallow-water species Chrysopetalum debile (Chrysopetalinae), one of the yet undescribed free-living deep-sea species Boudemos sp., and those of the two deep-sea bivalve endosymbionts Craseoschema thyasiricola and Iheyomytilidicola lauensis (Calamyzinae). An updated phylogeny of Chrysopetalidae is performed, which supports previous phylogenetic hypotheses within Chrysopetalinae and indicates a complex ecological evolution within Calamyzinae. Additionally, analyses of natural selection pressure in the four mitochondrial genomes and additional genes from the two shallow-water species Bhawania goodei and Arichlidon gathofi were performed. Relaxed selection pressure in the mitochondrion of deep-sea and symbiotic species was found, with many sites under selection identified in the COX3 gene of deep-sea species.

Morphological and molecular systematic review of Marphysa Quatrefages, 1865 (Annelida: Eunicidae) species from South Africa

A vast polychaete fauna is hidden behind complexes of cryptic and pseudo-cryptic species, which has greatly hindered our understanding of species diversity in several regions worldwide. Among the eunicids, Marphysa sanguinea Montagu, 1813 is a typical example, recorded in three oceans and with various species considered its junior synonyms. In South Africa, specimens previously misidentified as M. sanguinea are now known as Marphysa elityeni Lewis & Karageorgopoulos, 2008. Of the six Marphysa Quatrefages, 1865a species recorded from the same region, three have their distributions restricted to South Africa while the others are considered to have worldwide distributions. Here, we evaluated the taxonomic status of the indigenous M. elityeni and investigated the presence of the widespread species Marphysa macintoshi Crossland, 1903 and Marphysa depressa Schmarda, 1861 in South Africa using morphological and molecular data. Our results reveal that M. elityeni is a junior synonym of Marphysa haemasoma, a species previously described from South Africa which is herein reinstated as a valid species. Both M. macintoshi and M. depressa are not present in South Africa and their status as being distributed worldwide deserves further investigation. Marphysa durbanensis Day, 1934 and the new species described here, M. sherlockae n. sp., had been misidentified as M. macintoshi and M. depressa respectively. Thus, the number of Marphysa species with distributions restricted to South Africa increased from three to five. This study reiterates the importance of implementing an integrated taxonomic framework to unravel local biodiversity.

Digging the diversity of Iberian bait worms Marphysa (Annelida, Eunicidae)

During a visit to polychaete-rearing facilities in the vicinity of Bay of Cádiz (SW Iberian Peninsula, Atlantic Ocean), we sampled two populations of Marphysa (Annelida, Eunicidae) originally occurring at nearby intertidal soft bottoms, one being more than twice as long as the other at the same age. We analysed them using partial sequences of two mitochondrial genes, 16S rDNA and Cytochrome Oxidase I, and classical morphological observations. Our molecular results confirmed that the two populations corresponded to two different species, with PTP species delimitation values ranging from 0.973 (long-bodied species) to 0.999 (short-bodied species). Morphologically, the short-bodied species resembles the recently redescribed M. sanguinea (Montagu, 1813), but differs mainly in having some parapodia with two subacicular hooks (one bidentate and one unidentate) and three types of pectinate chaetae, Two isodont present all along the body, and one particularly large anodont asymmetric appearing only from mid-posterior parapodia. The long-bodied species resembles Marphysa aegypti Elgetany, El-Ghobashy, Ghoneim and Struck, 2018 both in size and in having very robust, unidentate subacicular hooks (single in most parapodia, two-both similar in size and form-in some posterior parapodia), but differs, among other features, in the maxillary formula, the number of acicula per parapodia and the number and shape of pectinate chaetae. Accordingly, we are here fully illustrating and formally describing the two Iberian populations as Marphysa gaditana sp. nov. (short-bodied) and Marphysa chirigota sp. nov. (long-bodied) and we are emending the description of M. aegypti based on our revision of the type material. Also, we discuss on the distribution of the species of the sanguinea-group and on the relevancy of taxonomically robust studies when dealing with species of commercial interest having the potential of being globally spread through human activities, as well as on the misunderstandings caused by the incorrect use of the "cosmopolitan species" concept.

Guess who? On the importance of using appropriate name: case study of Marphysasanguinea (Montagu, 1813)

The common bait worm Marphysasanguinea (Montagu, 1813), originally described from the south coast of England, is the type species of the genus. This species has been widely reported from all around the world and has been considered as cosmopolitan until recently. This is partly because the original description was very brief and poorly illustrated, and also because all species superficially look similar. In order to clarify the situation, M.sanguinea was redescribed and a neotype was designated by Hutchings and Karageorgpoulos in 2003. Recently, specimens from Cornwall, close to the type locality, were sampled, examined morphologically, and used to obtain COI gene sequences for this species. Molecular results permitted us to confirm the identity and presence of M.sanguinea along the French coasts and to highlight the presence of inaccurate sequences of this species on GenBank. Use of this "false" cosmopolitan species at a worldwide scale by many biologists is also discussed in this paper.

The complete mitochondrial genome of the polychaete, Goniada japonica (Phyllodocida, Goniadidae)

The study determined the complete mitochondrial genome (mitogenome) of the polychaete, Goniada japonica, which was first reported in the family of Goniadidae. A total of 7162 reads were generated by Illumina HiSeq2500 platform (Illumina Inc., San Diego, CA) with an average depth of 58.41×. The mitogenome of G. japonica was 15,327 bp in size and consists of 37 typical genes (13 protein-coding genes, 2 rRNA genes and 22 tRNA genes) and a putative control region. All the 37 genes were encoded on the heavy strand whose nucleotide compositions were 35.08% of A, 33.69% of T, 11.66% of G, and 19.57% of C, showing a lower content of G + C (31.23%). The gene order of 15 major coding genes was identical to that of the Nereididae species. Phylogenetic analysis showed that G. japonica has a closer relationship with Tylorrhynchus heterochaetus of Nereididae.