Mesomyzostoma leukos Rouse, Lanterbecq, Summers and Eeckhaut, sp. nov.
Creators: name: Greg W. Rousea
name: Deborah Lanterbecq
name: Mindi M. Summersa
name: Igor Eeckhaut
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Annelida
Polychaeta
Myzostomida
Mesomyzostoma
Mesomyzostoma leukos

description: Mesomyzostoma leukos Rouse, Lanterbecq, Summers and Eeckhaut sp. nov.
(Figure 7)
Mesomyzostoma n. sp. 4a in Lanterbecq et al. (2006, 2009) Mesomyzostoma n. sp. 4b in Lanterbecq et al. (2006, 2009) Mesomyzostoma n. sp. 4 in Summers and Rouse (2014)
Material examined
North Point, Lizard Island Great Barrier Reef (Australia), 14°38.655' S, 145°27.267ʹ E; 10 – 15 m depth. Collector: Greg Rouse, 20 November 2001. One specimen each from two hosts that cannot be reliably identified at present. Each was parasitic inside a species of the Dichrometra, Lamprometra or Liparometra complex (Mariametridae) pending revision by Taylor et al. (in prep.; see Summers, Messing, et al. (2014). Holotype (SAM- E3408) (host = Dichro- /Lampro- / Liparometra sp. 1) incomplete, in two fragments; one piece in 70% ethanol following formalin fixation; the other fixed and preserved in 95% ethanol. A fragment of the holotype was dissolved in bleach for observation of the parapodial hook apparatus. A piece of the holotype and the whole of the other individual (host = Dichro- /Lampro- / Liparometra sp. 4) were digested for DNA extraction and molecular phylogenetic analyses.
Etymology
Named for the white colour of the body, from leukos, Greek for white.
Diagnosis
As the holotype is incomplete, in two fragments, a complete morphological diagnosis is not possible, though its separation from other species is clearly supported based on DNA data (Figure 8). Lanterbecq et al. (2006: table 3) published the GenBank accession numbers for the COI, 16S and 18S DNA sequences for two individuals of this species (as Mesomyzostoma n. sp. 4a and Mesomyzostoma n. sp. 4b), all of which are unique among available sequences for species of Mesomyzostoma, but mere reference to accession numbers does not fulfil the conditions for availability of M. leukos sp. nov. under Article 13.1.2 of the International Code of Zoological Nomenclature. Therefore, as a diagnostic feature of this new species fulfilling Article 13.1.1 of the Code, we here provide the COI gene ’ s DNA sequence in full (Appendix 1). This sequence differs from those of all previously sequenced Mesomyzostoma (Table 1) by an uncorrected pairwise distance of at least 5.5%.
Description
Holotype (Figure 7 A), a 2-mm anterior or posterior fragment, thickest part about 1 mm across; two chaetigers present. Other fragment from an undetermined body region. No pharynx visible. No lateral organs visible. Chaetae from one side of a chaetiger removed for microscopy. Emergent hook inconspicuous, very thin shaft, tip curving to 90° with respect to shaft (Figure 7 B, C). No replacement hooks. Aciculae 0.1 mm long and 5 μm wide along most length except at tip, as long but thicker than emergent hooks. Manubrium small (Figure 7 C). Colour of individuals in life white.
Remarks
Mesomyzostoma leukos sp. nov. is clearly a new species based on DNA data (Figure 8), but the limited amount of material for morphological study means only a cursory description can be made at this time. The two specimens of M. leukos sp. nov. sequenced for DNA showed no differences for any gene.
description: Published as part of Greg W. Rousea, Deborah Lanterbecq, Mindi M. Summersa & Igor Eeckhaut, 2016, Four new species of Mesomyzostoma (Myzostomida: Annelida), pp. 1-23 in Journal of Natural History 50 (1) on pages 18-19, DOI: 10.1080/00222933.2015.1056266, http://zenodo.org/record/163246