Spio kurilensis Buzhinskaya, 1990

Bick, Andreas, 2011, Redescription of four species of Spio and Microspio (Polychaeta, Spionidae) from the Kuril Islands and Peter the Great Bay, northwest Pacific, Zootaxa 2968, pp. 39-56 : 41-43

Spio kurilensis Buzhinskaya, 1990 comb. nov.

(Figs 1–2)

Spio butleri kurilensis Buzhinskaya, 1990: 33 –34, Fig. 8.

Type material. Holotype: Kuril Islands, Ushishir Islands, Jankich Island, Kraternaya Bight, depth 5 m, 21 Aug 1985, ( ZIN 1/47104); Paratypes: Kuril Islands, Ushishir Islands, Jankich Island, Kraternaya Bight, depth 5–6 m, 21 Aug 1985, 14 specimens, ( ZIN 2/47105), 1 specimen ( ZIN 3/47106).

Diagnosis. Prostomium comparatively narrow, with bluntly rounded anterior part, lateral margin indented in front of the anterior pair of eyes; branchiae on chaetiger 1 short, one-fifth to half as long as second pair and narrower; notopodial prechaetal lamellae on about chaetiger 3–20 well developed and with triangular lobe on the superior margin; 5–8 bidentate neuropodial hooded hooks starting on chaetigers 25–27.

Description. Only fragments without palps available; holotype with about 70 chaetigers, 20 mm long, 1.7 mm wide; longest anterior fragment 22 mm long, with 65 chaetigers, width 2.0 mm; maximum width 2.1 mm.

Prostomium comparatively narrow; anterior part of prostomium bluntly rounded, slightly expanded at anterolateral margin (Figs 1A, 2A); often slightly projecting over the peristomium (Fig. 1B); lateral margin indented in front of the anterior pair of eyes; posterior end short, extending to chaetiger 1, tapered but not or only slightly elevated (Figs 1A, B); usually two pairs of black eyes arranged in trapezoid or rectangle, anterior pair crescent-shaped or rounded, posterior pair smaller and rounded, sometimes eyes not visible; prostomium distinctly separated from peristomium by a considerable furrow (Figs 1A, B, 2A).

Nuchal organs and metameric dorsal ciliated organs indistinct, even when applying methyl green; nuchal organs with short median and long lateral ciliary bands, median bands up to chaetiger 2 and lateral bands up to chaetiger 3 (Figs 1A, B); metameric dorsal ciliated organs double-paired, usually present from about chaetiger 5–6 (Fig. 1B), up to about chaetiger 16 longitudinally oriented and up to at least chaetiger 22 obliquely orientated, posterior extension not observable; transverse ciliary bands also not visible.

Branchiae from chaetiger 1, continuous to the end in all anterior fragments; length of first pair of branchiae about one-fifth to about half the length of second pair, first pair narrower than second pair (Figs 1A, B, 2A); branchiae on chaetiger 2 to about chaetiger 4–7 usually shorter and narrower than branchiae on the respective consecutive chaetiger, reaching midline dorsally and touching on some anterior chaetigers (Fig. 1B); branchiae with narrow base, tapering distally, cilia on inner and outer margin not visible (Figs 1 C–F).

First notopodium shifted slightly dorsally. Notopodial postchaetal lamellae on chaetiger 1 narrow (Fig. 1D); distinctly elongated with rounded tip on following anterior chaetigers (Fig. 1E); becoming shorter and wider on middle chaetigers (Fig. 1C); notopodial postchaetal lamellae of first 20–30 chaetigers fused with branchiae, separated from branchiae in posterior chaetigers (Figs 1C–F). Neuropodial postchaetal lamellae on anterior chaetigers rounded, becoming rectangular on middle chaetigers (Figs. 1C–F). Noto- and neuropodial postchaetal lamella on anterior chaetigers of about same width (proximal–distal axis), on posterior chaetigers notopodial lamellae wider than neuropodial lamellae (Fig. 1C). Notopodial prechaetal lamellae of chaetigers 3–20 well developed, with significant triangular lobe on the superior margin (Figs 1E, F, 2B).

FIGURE 1. Spio kurilensis Buzhinskaya, 1990 comb. nov.: A. Prostomial region, dorsal view. B. Anterior end, dorsal view. C- F. Parapodium from chaetiger 28, 1, 3, 11. G. Neuropodial hook from chaetiger 28. H. Neuropodial inferior chaeta from chaetiger 28. I. Short granulated neurochaeta from 1st parapodium. J. Thin neuropodial capillary from chaetiger 28. Scale: A, B 0.5 mm, C–F 0.1 mm, G–J 10 µm. A. Holotype ZIN N1/47104. All others paratype, ZIN N2/47105.

Notopodial chaetae all capillaries with narrow sheath; capillaries of anterior chaetigers arranged in two rows: chaetae of anterior row shorter than those in posterior row and distinctly granulated; chaetae of posterior row longer than in anterior row, lacking granulations; additional superior fascicle of 2–9 very long, thin capillaries without granulations present; capillaries of middle and posterior chaetigers not clearly arranged in rows, thin, non-granulated, of different length within a fascicle. Neuropodia with rows of capillaries and hooded hooks as well as an inferior fascicle of sabre chaetae in hook-bearing chaetigers; capillaries of anterior neuropodia arranged in two rows, anterior row with granulated capillaries with narrow sheaths (Fig. 1I), posterior row with non-granulated capillaries with narrow sheaths; posterior row replaced by single row of 5–8 bidentate hooded hooks starting from chaetigers 25–27 (Fig. 1G); hooks not narrowed subdistally, with a comparatively long hood, main fang and apical tooth well developed forming an obtuse angle to shaft; on posterior chaetigers additional very thin alimbate capillaries with fine granulation between the hooks or behind the row of hooks present (Fig. 1J); hook-bearing chaetigers with 2 to 4 distally granulated sabre chaetae in inferiormost position (Fig. 1H).

Pygidium unknown.

Pigmentation. No distinct pattern in studied material. Buzhinskaya (1990) reports small pigmented patches in front of the anterior pair of eyes.

Methyl green staining pattern. Inconspicuous; prostomium, peristomium, margin of pre- and postchaetal lamellae, branchiae and boundary of chaetigers ventrally slightly stained ( Figs 2 A, B).

Biology. All specimens were found in sandy substrates in 5–6 m depth in the green sea urchin Stongylocentrotus droebachiensis community together with Harmothoe imbricata, Eteone longa and Haplosyllis cratericola ( Buzhinskaya 1990, Tarasov 2006).

Geographical distribution. So far only known from the type locality Jankich Island, Ushishir Islands, Kurils, northwest Pacific Ocean.

Remarks. All specimens are anterior fragments and in rather poor condition. Nevertheless, most diagnostic characters can be observed. Based on these characters S. butleri kurilensis Buzhinskaya, 1990 is separated from S. butleri Berkeley and Berkeley, 1954 and raised to species level. Spio kurilensis Buzhinskaya, 1990 comb. nov., differs from S. butleri in the beginning, number and shape of neuropodial hooded hooks. Hooks first appear on chaetiger 22–24 (maximum number about 20) in S. butleri and 25–27 (maximum number 8–9) in S. kurilensis comb. nov. The hooks of S. butleri have two long, parallel apical teeth which form a right angle to the shaft whereas they are of different length and forming an obtuse angle in S. kurilensis comb. nov. The superior triangular lobe present in prechaetal notopodial lamellae of anterior chaetigers in S. kurilensis comb. nov. is unique among Spio species. No other Spio species exists with the diagnostic characters assigned to S. kurilensis comb. nov.

The condition of the specimens in the collection of the Zoological Institute, Saint Petersburg, does not enable the description of other important characters which are relevant for Spio species. Thus it is not possible to provide reliable information on the pattern of pigmentation, the pattern of white dots on the ventrum, the shape of the most posterior neuropodial lamellae and the number of posterior abranchiate chaetigers (see Meißner et al. 2011). An amended description can be provided only if new material from the type locality becomes available. Based on current knowledge the species has so far only been found in the Kraternaya Bight close to a thermal spring ( Buzhinskaya 1990, Tarasov 2006).

Figures

FIGURE 2. Spio kurilensis Buzhinskaya, 1990 comb. nov.: A. Anterior end, dorsal-oblique view. B. Parapodia on chaetigers 5 to 9, left side, lateral view; arrows indicate superior extension of notopodial prechaetal lobe. Scale: A 0.5 mm, B 0.1 mm. Both holotype ZIN N 1 / 47104.