Ophryotrocha bohnorum, Zhang & Zhou & Yen & Hiley & Rouse, 2023

Zhang, Dongsheng, Zhou, Yadong, Yen, Nicole, Hiley, Avery S. & Rouse, Greg W., 2023, Ophryotrocha (Dorvilleidae, Polychaeta, Annelida) from deep-sea hydrothermal vents, with the description of five new species, European Journal of Taxonomy 864, pp. 167-194 : 187-189

Ophryotrocha bohnorum sp. nov.

urn:lsid:zoobank.org:act:181A86F6-7F8D-401C-B252-21FF39F6C5C0

Fig. 9

Etymology

Ophryotrocha bohnorum sp. nov. is named for Jeffrey and Brenda Bohn and their family in recognition of their enduring support of deep-sea research.

Material examined

Holotype TONGA • 1 spec. (fixed in ethanol and a midbody piece used for DNA extraction); Lau Back-Arc Basin, Southern Valu Fa Ridge, Hine Hina Vent Field , active hydrothermal vents; 22.539° S, 176.718° W; depth 1845–1906 m; 22–23 May 2005; Greg Rouse, Fredrik Pleijel and Robert Vrijenhoek leg.; collecting event: ROV Jason II dive 146; GenBank: OP311742 (COI), OP304895 (16S), OP311649 (H3); SIO-BIC A14092 .

Paratypes TONGA • 1 spec. (fixed in ethanol); same collection data as for holotype; SIO-BIC A14094 • 4 specs (fixed in formalin); same collection data as for holotype; SIO-BIC A14095 • 1 spec. (fixed in ethanol and a midbody piece used for DNA extraction); same collection data as for holotype; GenBank: OP311744 (COI); SIO-BIC A14165 • 1 spec. (fixed in ethanol and a midbody piece used for DNA extraction); same collection data as for holotype; GenBank: OP311743 (COI); SIO-BIC A14166 • 1 spec. (fixed in ethanol); same locality as for holotype; 22.532° S, 176.719° W; depth 1818–1907 m; 21–22 May 2005; Greg Rouse, Fredrik Pleijel and Robert Vrijenhoek leg.; collecting event: ROV Jason II dive 145; SIO-BIC A14088 • 1 spec. (fixed in ethanol); same collection data as for preceding; SIO-BIC A14089 • 1 spec. (fixed in ethanol); same collection data as for preceding; SIO-BIC A14090 • 3 specs (fixed in formalin); same collection data as for preceding; SIO-BIC A14091 • 1 spec. (fixed in ethanol); same collection data as for holotype; SIO-BIC A14093 .

Description

In life, white, yellow gut, with white eggs mid-body ( Fig. 9A ), opaque white after preservation. Body 12 mm long with 60+ segments, tapering slightly along body.Prostomium rounded, wider than long,with a slightly rise posteriorly in the middle. Paired antennae long cirriform, inserted dorsally, tapering distally. Paired palps cirriform, slightly shorter than antennae, inserted dorsal-laterally ( Fig. 9A ). Peristomium two equal rings, similar in length to first chaetiger, slightly longer than following chaetigers, with two brown spots located dorsal-laterally between the two rings ( Fig. 9A–B ). Maxillae P-type, maxillary carriers comb-like, with large main fang, 8 pairs of free denticles. Posterior 4 denticles (D1–D4) heavily sclerotized, with large main fang and sharp teeth; anterior 4 denticles (D5–D8) translucent, with a small main fang and tiny teeth, D5–D6 overlap with D3–D4 ( Fig. 9C ). Mandibles transparent, rod-like shafts, cutting plates triangular, with blunt teeth on the anterior edge ( Fig. 9D ). Parapodia uniramous, acicular lobe rounded with a small tip in the middle of the distal margin, dorsal cirri short, rounded lobes, ventral cirri long extending from distal margin of acicular lobe ( Fig. 9E ). Supra-acicular chaetae simple, distally serrated, with a small hook on the tip ( Fig. 9F ). Sub-acicular chaetae all compound, shafts bifid on the top, serrated blades with a small hook similar as supra-acicular chaetae on the tip ( Fig. 9G ). Pygidium with two long digitiform cirri ( Fig. 9A ).

Distribution

Only known from vents at the Lau Back-Arc Basin, southwest Pacific Ocean at depths of 1845–1907 m.

Remarks

The phylogenetic results ( Fig. 1 ) show that Ophryotrocha bohnorum sp. nov. is most closely related to an undescribed species complex of Ophryotrocha (O. Seep4) from eastern Pacific methane seeps ( Thornhill et al. 2012). There is no morphological information available for these specimens. A clade comprising other eastern Pacific species, Ophryotrocha globopalpata from hydrothermal vents, O. flabella from a whale fall and O. Seep3 ( Thornhill et al. 2012), is then the well supported sister group to this clade. Based on this topology Ophryotrocha bohnorum appears to have independently colonized hydrothermal vents from O. globopalpata ( Fig. 1 ). Ophryotrocha bohnorum has hooked tips of the supra- and sub-acicular chaetae and red-brown spots located dorsal-laterally between two peristomial segments, features not seen in other species from hydrothermal vents. Only four species of Ophryotrocha , O. atlantica Hilbig & Blake, 1991 , O. mediterranea Martin Abello & Cartes, 1991 , O. pachysoma Hilbig & Blake, 1991 , and O. socialis Ockelmann & Åkesson, 1990 , have been described with chaetae with hooked tips. Ophryotrocha bohnorum can be easily distinguished from these species by its transparent mandibles with serrated anterior edge.

Figures

Fig. 9. Ophryotrocha bohnorum sp. nov. A. Whole body of living paratype (SIO-BIC A14095). B. Dorsal view of anterior living holotype (SIO-BIC A14092) one of the distinctive brown spots on the peristomium indicated by white arrow. C. Mandibles of paratype (SIO-BIC A14093). D. Maxillae of paratype (SIO-BIC A14093). E. Parapodium of paratype (SIO-BIC A14093). F. Simple supra-acicular chaetae of paratype (SIO-BIC A14093). G. Compound sub-acicular chaetae of paratype (SIO-BIC A14093).

Fig. 1. Phylogenetic tree of Dorvilleidae Ophryotrocha Chamberlin, 1919 based on the Maximum Likelihood and Bayesian Inference analysis of the concatenated dataset of three genes. The outgroup, Eunice pennata (Müller, 1776) is not shown. Numbers on the nodes represent bootstrap support (BS) values followed by posterior probability (PP) values. Blank values indicate BS score of less than 50 or PP of less than 0.7. The * symbol indicated BS support was 95% or greater and PP was 1. Orange branches indicate hydrothermal vent lineages showing that vents have been colonized at least 5 × by Dorvilleidae, 3 × within Ophryotrocha Claparède & Mecznikow, 1869. The letters A and B refer to the two main clades of Ophryotrocha.