Ophelina bowitzi, Helgason, 2011

Helgason, Julio Parapar Juan Moreira Gudmundur V., 2011, Distribution and diversity of the Opheliidae (Annelida, Polychaeta) on the continental shelf and slope of Iceland, with a review of the genus Ophelina in northeast Atlantic waters and description of two new species, Organisms Diversity & Evolution (New York, N. Y.) 11 (2), pp. 83-105 : 95-97

Ophelina bowitzi sp. nov.

( Figs. 1d , 12 , 13 and 14 )

? Ammotrypanella arctica McIntosh —as misidentified by Fauvel (1914: 246); Kirkegaard (1996: 68).

Etymology The species is named in honour of the Norwegian polychaetologist Dr. Carl Støp-Bowitz (1913–1997), Associate Professor at the University of Oslo, for his relevant contributions to the knowledge of the Norwegian and Arctic polychaetes, particularly of the Opheliidae .

Material examined BIOICE material: 162 specimens (1.36% of Opheliidae ) in nine samples (see Electronic Supplementary Material), as follows. Holotype ( Icelandic Museum of Natural History , IMNH 24320 ), BIOICE sample 3167: North Atlantic Ocean S of Iceland, bottom tow from 60°54′88″N 22°47′26″W to 60°55′28″N 22°47′ 62″W, 1897 to 1899 m depth, 26 July 2000, bottom temperature 2.98°C. 10 paratypes ( BIOICE sample 3167, IMNH 24321 ); 14 paratypes ( IMNH 24322 , BIOICE 2860 ), 13 paratypes ( IMNH 24323-24 , 2863 ), 12 paratypes ( IMNH 24325 , BIOICE 2863 DK); 1 paratype ( MNCN 16.01 /13272, BIOICE sample 3012 DK), 1 paratype ( MNCN 16.01 /13273, BIOICE 3076 ). Complementary material (Icelandic Museum of Natural History): 8 specimens ( BIOICE sample 2859), 72 spec. (2863), 2 spec. (3012), 3 spec. (3171 DK), 8 spec. (3173), 17 spec. (3176–0.5).

Diagnosis A large species mostly distinguishable by (1) the presence of branchiae that are very short in the anterior half of the body, larger in the posterior half, and short again in some chaetigers anterior to the last abranchiferous segments; (2) a large anal tube characteristically bent upwards and usually present in the specimens, wide in the basal part and becoming narrower in the distal part.

Description (of holotype, unless otherwise mentioned) Body 39 mm long (15–43 mm in paratypes) and 2.5 mm wide (1.0–3.0 mm in paratypes); fusiform, with 45 chaetigers (44–46 in paratypes), deeply grooved both laterally and ventrally. Prostomium short and conical ( Figs. 12a and 13a ), with short palpode and two prominent nuchal organs ( Fig. 13b ). Eyes not observed. Parapodia rounded, provided with dorsal branchiae from second chaetiger, with a ventral tongue-shaped lobe ( Fig. 13c–f ) and a button-shaped ciliary organ (lateral organ) between chaetal bundles ( Fig. 13f ). Branchiae short in first half of body ( Figs. 12a and 13a, c, d ), becoming much larger in middle body region ( Fig. 14a, b ), diminishing again in last quarter of body and disappearing in last chaetigers ( Fig. 14c, d ). Branchiae provided with two ciliary rows ( Fig. 13e ); surfaces of some long gills with small, blister-shaped bumps ( Fig. 14b ). Chaetae all smooth capillaries. Anal tube as long as last 10 chaetigers ( Fig. 14e ), becoming narrower from base to distal part, characteristically bent upwards and provided with about 10 short terminal cirri ( Fig. 14f ).

Occurrence Species restricted to deep (1897–2709 m) and temperate (2.07–3.29°C) waters off the south coast of Iceland ( Fig. 1d ).

Remarks Ophelina bowitzi sp. nov. presents all the characters currently accepted as diagnostic for the genus Ophelina . However, its long body and the size of its branchiae make it very different from congeneric species in the NEAW which are usually small and often have branchiae of the same size throughout the body (although they may be missing from the mid-body). Ophelina bowitzi also shows a considerable increase in branchiae length in the posterior region of the body. We agree with Schüller (2008) that the material from the Azores islands identified as Ammotrypanella arctica by Fauvel (1914) is unlikely to correspond to the latter species. That material was not examined by us, but according to the description and illustrations by Fauvel (1914), especially regarding the patterns of distribution and shape of the branchiae and anal tube ( Fig. 9b ), it is likely to belong to O. bowitzi sp. nov. The record by Kirkegaard (1996) of A. arctica from the Kermadec Trench ( New Zealand) should also be reviewed because of the distance from the type locality of that species. Ophelina ammotrypanella Schüller, 2008 , from Antarctic waters, corresponds fairly well to the description of O. bowitzi sp. nov. regarding the shapes and sizes of the body and anal tube and the absence of an anal cirrus. However, the two species differ in the shape of the nuchal organ (prominent in O. bowitzi sp. nov., indistinct in O. ammotrypanella ), the upward bend of the anal tube in O. bowitzi , and especially in the presence in O. bowitzi of very small branchiae on some chaetigers preceding the abranchiate chaetigers near the end of the body.

SEM examination of Ophelina bowitzi sp. nov. has revealed, as in O. basicirra sp. nov., the presence of two ciliated bands associated to the branchiae and a well defined ciliated button between the dorsal and ventral chaetal bundles. In addition, small bumps have been observed on the surface of some gills. Similar structures were previously reported from Euzonus zeidleri Hartmann-Schröder & Parker, 1995 and described as small pinnae ( Hartmann-Schröder and Parker 1995). However, based on our observations the latter structures might represent blister-shaped artefacts resulting from the fixation of specimens rather than a true branchial feature.

Genus Tachytrypane McIntosh, 1878 Tachytrypane jeffreysii McIntosh, 1878 Tachytrypane jeffreysii McIntosh — McIntosh (1878: 505); Fauvel (1927: 135); Støp-Bowitz (1948: 24); Eliason (1951: 135); Hartman and Fauchald (1971: 134); Castelli et al. (1995: 11); Martínez and Adarraga (2001: 42).

Material examined BIOICE material: 21 specimens (0.18% of Opheliidae ) in ten samples (see Electronic Supplementary Material) .

Occurrence Species restricted to relatively warm waters (2.07–4.78°C) of the southeast to southwest coast of Iceland, always below the 1000 m isobath (1066–2709 m).

Previously reported distribution The few known records indicate that T. jeffreysii is mostly restricted to the North Atlantic Ocean. This species was originally described from the Davis Strait between Canada and Greenland, then recorded from European coasts by Fauvel (1927), Støp-Bowitz (1948) and Martínez and Adarraga (2001), from the Central North Atlantic by McIntosh (1878) and Eliason (1951), from the Mediterranean Sea (Adriatic) by Castelli et al. (1995), and from North America by Hartman and Fauchald (1971).

Figures

Fig. 1 Maps of the study area and collecting sites of samples including specimens of Opheliidae. a All samples combined. b Ammotrypanella cf. arctica McIntosh. c Ophelina basicirra sp. nov. d Ophelina bowitzi sp. nov

Fig. 12 Ophelina bowitzi sp. nov. (holotype, IMNH 24320). a Anterior end, lateral view. b Posterior end, lateral view. Scale bar: 2 mm

Fig. 13 Ophelina bowitzi sp. nov. (IMNH 24324, BIOICE sample 2863). a Anterior end, lateral view. b Detail of nuchal organ. c Chaetiger 11. d Chae- tiger 18. e Chaetiger 25; arrows mark positions of two ciliary bands. (f) Chaetiger 28; arrow marks position of lateral organ. Scale bars: (a) 1 mm; (b) 90 μm; (c, d, f) 100 μm; (e) 900 μm

Fig. 14 Ophelina bowitzi sp. nov. (IMNH 24324, BIOICE sample 2863). a Mid-body chaetigers (branchiae lost on two chaetigers at right). b Chaetigers 27–30. c Last chaetigers, lateral view; arrow marks last branchiferous chaetiger. d Last branchiferous chaetigers. e Posterior end, lateral view; shape of arrow reflects typical bend to dorsal of posterior body region. f Detail of posterior end of anal tube. Scale bars: (a) 900 μm; (b) 500 μm; (c) 2 mm; (d) 100 μm; (e) 700 μm; (f) 200 μm

Fig. 9 Posterior body region in some Atlantic Ophelina species (redrawn from originals). a O. abranchiata (from Støp-Bowitz 1948). b O. bowitzi sp. nov. (from Fauvel 1914, as A. arctica). c O. delapidans longicephala (from Hartmann- Schröder 1977). d O. groenlandica (from Støp-Bowitz 1948). e O. helgolandica (from Augener 1912). f O. norvegica (from Støp-Bowitz 1945). g O. nybelini (from Eliason 1951)