Ophryotrocha hartmanni Huth, 1933

Ravara, Ascensão, Wiklund, Helena & Cunha, Marina R., 2021, Four new species and further records of Dorvilleidae (Annelida, Polychaeta) from deep-sea organic substrata, NE Atlantic, European Journal of Taxonomy 736, pp. 44-81 : 59-61

Ophryotrocha hartmanni Huth, 1933

Fig. 8

Ophryotrocha hartmanni Huth, 1933: 309–381 , fig. 1 (mentioned as a new species on page 311, but the description is mainly based on cytological characters; type locality: Plymouth)

Ophryotrocha hartmanni – Parenti 1961: 440–444, figs I6–11, II4–5 (re-description; Roscoff).

Material examined

MOROCCO • 1 spec. (ethanol), damaged; GoC, Mercator MV; 35°17.916′ N, 06°38.709′ W; 354 m depth; 19 May 2009; Stn B09-14b_01W; wood substrata; DBUA0002292.01 • 1 spec. (slide preparation), very damaged; same locality as for preceding; 3 Mar. 2008; Stn 64PE284_12752A; alfalfa substratum; DBUA0002293.01 • 1 spec. (ethanol); GoC, Darwin MV; 35°23.523′ N, 07°11.513′ W; 1100 m depth; 19 May 2009; Stn B09-14b_02W; wood substratum; DBUA0002292.02 .

Additional material

GERMANY • 1 spec.; Helgoland , North Sea ; shallow water; GNM: Polychaeta: 14698 .

Remarks

The original description of O. hartmanni given by Huth (1933) is based mostly on cytological features. The only morphological details included reference to the specimens’ average length (4–5 mm), to the body shape as being torpedo-like and to the position of the sperms and oocytes (sperms in the first three chaetigers and oocytes from the fourth chaetiger onwards). The specimens examined by Huth were collected at Plymouth and kept in laboratory conditions, but no information is given on type material or its deposition. Parenti (1961) provided a re-description of the same species based on material from Roscoff also kept in laboratory conditions. There is no mention to a re-examination of type material or other material from the type locality, but Parenti (1961) confirmed some of the cytological observations made by Huth (1933) and provided a complete morphological description, highlighting the differences between this and other species. Again, there is no indication regarding the deposition of the examined material. Åkesson (1973) studied the reproduction and larval morphology of O. hartmanni using specimens from Plymouth and Roscoff aquaria and from the harbours of Malaga (S Spain) and concluded that interbreeding of the three strains produced fertile progeny in all combinations, and also in subsequent generations. This denotes the widespread distribution of this species.

Only three specimens of O. hartmanni were found in the present study, two of which are not in good condition. The smallest (13 chaetigers, 0.76 mm long), and better preserved, and the larger (approximately 20 chaetigers, 2.3 mm long) specimens were mounted in a permanent slide where the jaw apparatus, parapodia and chaetae could be properly examined ( Fig. 8 ). The molecular analysis performed with the posterior part of the third specimen failed, thus preventing molecular comparison. Except for the presence of small dorsal cirri on the parapodia ( Fig. 8D ), stated as absent for O. hartmanni , the GoC specimens have all the morphological diagnostic characteristics described by Parenti (1961). However, the DNA voucher of O. hartmanni included in our phylogenetic analysis, identified by Bertil Åkesson and also obtained from crossbreeding experiments with the previous strains, has very small dorsal cirri on its parapodia (H. Wiklund pers. obs.). Similarly to O. hartmanni , the antennae of our specimens are poorly developed, palps are absent and mandibulae are rod-shaped, widening distally into bifid serrated cutting plates with tiny pointed teeth (around 14 teeth in the smaller specimen spread along all the cutting edge, including around the inner peak, Fig. 8 A–B; in the larger specimen, the teeth are worn out and the inner peak is almost smooth, Fig. 8E ). The juvenile and adult forms of maxillae are also similar to those of O. hartmanni . The P-type forceps have a large distal tooth, the distal half is comb-like with alternating large and small teeth, and the posterior part has a ridge of tiny teeth ( Fig. 8C ). The K-type forceps have bifid tips strongly bent inwards (more gently curved in O. hartmanni , as illustrated in Parenti 1961: fig. II-4); the sub-apical tooth has a straight spine superiorly and is finely denticulated inferiorly ( Fig. 8F ). Denticles 1 to 7 (D1–7) are similar in shape for P- and K-type maxillae. Denticle 1 is similar in shape to the P-type forceps; D2 is shovel-shaped but also with a large tooth on the inner edge; D3 is shovel-shaped, narrow, with coarse teeth; and D4–7 are shovel-shaped, wider and with smaller teeth. According to Parenti (1961), O. hartmanni is particularly abundant in muddy sediments rich in organic detritus. This study provides a new record of O. hartmanni for the North Atlantic (at the GoC) and extends the bathymetric distribution of the species to 1100 m depth.

Ecology and distribution

N Atlantic: from Norway to northern France on soft bottoms from the intertidal down to around 100 m depth ( Oug & Pleijel 2015 and references within), and in the Gulf of Cadiz (Moroccan Margin) in experimentally deployed wood and alfalfa substrata at 354–1100 m depth (present study); Mediterranean: Spain ( Åkesson 1973), Italy (Simonini et al. 2010).

Figures

Fig. 8. Ophryotrocha hartmanni Huth, 1933 (DBUA0002293.01). Compound microscope images. A. Mandibulae of a small specimen, ventral view. B. Detail of the cutting edge of the same. C. P-type maxillae of the same specimen, dorsal view. D. Mid-body parapodium, anterior view. E. Mandibula of a larger specimen, ventral view. F. K-type maxillae of the same specimen, dorsal view. G. Acicular chaeta of sub-acicular lobe. H. Supra-acicular chaetae, mid-body parapodium. I. Sub-acicular chaeta, mid-body parapodium. Numbers refer to free denticles.