Ophryotrocha scutellus, Wiklund, Helena, Glover, Adrian G. & Dahlgren, Thomas G., 2009

Wiklund, Helena, Glover, Adrian G. & Dahlgren, Thomas G., 2009, Three new species of Ophryotrocha (Annelida: Dorvilleidae) from a whale-fall in the North-East Atlantic, Zootaxa 2228, pp. 43-56 : 46-48

Ophryotrocha scutellus sp. nov. ( Figs 1 A–D)

Material examined: Northern North Atlantic, coastal Skagerrak, 58° 53.1’ N; 11° 06.4’ E, female with eggs, 6 mm long, 29 chaetigers, preserved in formaldehyde from experimental tank with bone material sampled from a minke whale carcass, which was implanted at 125 m depth, holotype ( SMNH T- 7816); same location, 2 specimens, preserved in formaldehyde, paratypes (NHM2009.25); same location, one specimen preserved in osmium for SEM, and several specimens preserved in ethanol for DNA extraction. Fishfarm in Mele, Hardangerfjord, 60°21.27’N; 6°20.89’E, 104 m depth, several specimens preserved in formalin.

Description: Body shape elongated, uniform width for majority of body length, tapering slightly at posterior end. Colour transparent, with white eggs visible in females. ( Fig. 1 A).

Prostomium round and dorso-ventrally flattened, disc-like. Eyes lacking. Long cirriform paired antennae inserted dorsally, reaching to first chaetiger, equally long palps cirriform inserted lateroventrally on prostomium. Jaws of P-type, mandibles rod-like without any serration. Maxillae with seven pairs of free denticles ( Fig. 1 B).

Two peristomial achaetous segments. Parapodia uniramous with long dorsal and ventral cirri and cirriform acicular lobe, supraacicular chaetae simple, subacicular chaetae compound with serrated blades ( Figs 1 C–D). Subacicular chaetal lobe with simple chaeta.

Pygidium with terminal anus, two pygidial cirri as long as antennae and palps laterally and a short, nublike unpaired appendage ventrally.

Distribution: Known from a minke whale carcass at 125 m depth (58°53.1’N; 11°06.4’E) in the Koster area in Sweden, and from sediment sampled at 104 m depth beneath a fish farm in Hardangerfjord (60°21.27’N; 6°20.89’E) in Norway.

Reproduction: Eggs present in females from chaetiger 5 and in all segments to posterior end of body. No data available on the presence of sperm.

Ecology: Live observation in aquarium experiments show adult specimens crawling on filamentous bacterial mats on the whale bones, and bacterial pellets are present in the worms guts, indicative of a bacterial diet.

Etymology: Ophryotrocha scutellus is named after its flattened disc-like head, scutella is the latin word for flat dish or saucer.

Remarks: Ophryotrocha scutellus has a rounded dorso-ventrally flattened head-form, shaped like a disc. Another Ophryotrocha that is reported to have flattened prostomium is O. platykephale , from which O. scutellus differs in jaw morphology, form of parapodia and absence of branchiae. Accession numbers for DNA sequences from O. scutellus , published on GenBank: GQ415469 (16S), GQ415488 ( COI), GQ415506 (H3).

Figures

FIGURE 1. Ophryotrocha scutellus sp. nov., (A) live photo, (B) light micrograph of jaws, (C) light micrograph of parapodium, (D) SEM micrograph of chaetae. Scale bars in (B) and (C) are 100 µm, in (D) 20 µm.