A new polychaete genus and species of the Kongsfjorden, Spitsbergen, Svalbard

Glyphochaeta laudieni, a new genus and species of the “Spionidae”, is described from the Arctic. The specimens were collected from the Kongsfjorden, Spitsbergen, Svalbard, in a marine grotto. Glyphochaeta laudieni was associated with colonies of unidentified Bryozoa. This new genus and species is characterized by a prostomium with frontal horns, the absence of branchiae and sabre chaetae, and the presence of grooved spines which replace hooded hooks in some chaetigers of the middle body region. These spines are associated with glandular organs situated in neuropodia. The significance of characters for determining the systematic position of Glyphochaeta within “Spionidae” is discussed. Glyphochaeta laudieni is probably related to Pygospio elegans.


Introduction
The ''Spionidae' ' Grube, 1850 as currently defined comprises 38 genera and more than 450 species (Wilson 2000;Rouse and Pleijel 2001), but it is now known to represent a paraphyletic assemblage (e.g. Blake and Arnofsky 1999;Rouse and Pleijel 2001). Features that have usually been used to characterize species within this group include the shape of the prostomium, especially the anterior margin and the posterior end (caruncle); the length and shape of the nuchal organ or dorsal sense organ; the number of branchiae, their distribution and the degree of fusion of branchiae with postchaetal notopodial lamellae; the distribution and form of hooded hooks, as well as the number of anal cirri or lobes. In addition, some genera are clearly characterized by strongly modified neuro-or notochaetae anteriorly or posteriorly, e.g. species of the Polydora and Atherospio (sensu Mackie 1996) complexes, Australospio Blake and Kudenov, 1978, Lindaspio Blake and Maciolek, 1992, Scolecolepides Ehlers, 1907, Spiophanes Grube, 1860, and Xandaros Maciolek, 1981. In most cases the function of these modified chaetae remains to be clarified.
Investigations of the intertidal and shallow subtidal polychaete fauna of the Kongsfjorden, Spitsbergen, yielded about 20 specimens belonging to the ''Spionidae''. These specimens all belong to the same species, which differs from all other spionids in having grooved chaetae in some neuropodia of the middle body region. These modified chaetae are grooved spines and are associated with glandular organs of the corresponding chaetigers. Based on this character, a new genus and species of ''Spionidae'' is described.

Material and methods
The specimens were collected in a marine grotto near Hansneset (78u59.089N, 11u57.439E) Blomstrandhalvøya, in the Kongsfjorden, Spitsbergen, between colonies of unidentified Bryozoa. The grotto is about 8 m wide and 15 m long, the opening is partially above the sea level. The water depth in the entrance of the grotto is about 6 m and in the back about 3 m. The light gradient is a major factor determining the hard bottom community here: the macroalgae Laminaria solidungula Agardh, 1868, Phycodrys rubens (Linnaeus) Batters, 1902, and Ptilota plumosa (Hudson) Agardh, 1868 dominate in the entrance of the grotto, whereas mainly sponges (Halichondria panicea (Pallas, 1766), H. genitrix (Schmidt, 1870), Haliclona viscosa (Topsent, 1888), Grantia utriculus (Schmidt, 1869), and Suberites ficus (Johnston, 1842)), but also the ascidian Halocynthia sp., the nephtheid soft coral Gersemia rubiformis (Ehrenberg, 1834) and Bryozoa occur in the back. The echinoderms Strongylocentrotus droebachiensis (O. F. Mü ller, 1776) and Henricia sanguinolenta (O. F. Mü ller, 1776) were also found on the wall of the grotto. The Kongsfjorden is an Arctic glacier fjord, influenced by tides (tidal range 1.5-2.0 m), bound by rocky shores, and covered by ice during the winter season. Since freshwater from glaciers and snowfields enters the shallow coastal areas at several places, brackish water overlies the marine water in summer. The salinity on the surface was between 5 and 10 psu, and between 30 and 34 psu near the bottom. More information about this fjord is given by Svendsen et al. (2002) and Hop et al. (2002). The Bryozoa colonies were scraped off from the cave wall by scuba divers at a depth between 3 and 4 m. The Bryozoa colonies and the associated fauna were preserved in a 4% formaldehyde-seawater solution. In the laboratory, samples were washed and sieved through a 0.5 mm screen. The unknown spionids and the other polychaetes were picked out under a dissecting microscope at 10-156 magnification. Methyl green staining was employed to visualize body structures. Drawings were made using a microscope and drawing attachment. For SEM studies, specimens were dehydrated in a critical point drier, attached to a stub and sputter-coated with gold palladium. SEM observations were made with a Zeiss DSM 960 A. For histological investigations of the glandular organ, samples were infiltrated and embedded in Araldite after dehydration. Sections with a thickness of about 1 mm were cut using a Leica Reichert Ultracut S ultramicrotome and subsequently stained in a solution modified after Richardson et al. (1960). Micrographs were taken with a Zeiss-Axioplan microscope and a CCD-camera ProgRes C10 (Jenoptik). Type material has been deposited in the Zoologische Sammlung der Universität Rostock (ZSRO); catalogue numbers are given below.

Diagnosis
Body not clearly divided in different regions. Anterior margin of prostomium with frontal horns; posterior end forming a short caruncle extending to chaetiger 1; without occipital antenna; eyes present. Nuchal organ as small ciliated patch on the posterior margin of the prostomium. Peristomium well developed. Branchiae absent. Postchaetal lamellae well developed only in the anterior body region. Mid-segmental dorsal ciliated crest present. Lateral organs absent. Notopodia with capillaries. Anterior neuropodia with capillaries; neuropodia of the middle and posterior body region with hooded hooks, replaced by grooved spines in some neuropodia of the middle body region. Some chaetigers of the middle body region with glandular organs. Sabre chaetae absent. Pygidium with four anal lobes.

Etymology
The generic name refers to the shape of the grooved spines that replace the hooded hooks in some neuropodia of the middle body region (glyphanos-Greek for a carving tool or chisel; chaite-Greek for bristle).    lamellae present; on chaetiger 1 tongue-like ( Figure 1B); thereafter, notopodial lamella first triangular, later broadly rounded ( Figure 1C-E), absent posteriorly; neuropodial lamella broadly rounded, absent when hooks appear ( Figure 1C-E). Notopodia with smooth or hirsute capillaries, usually in two rows. Anterior neuropodia with smooth or hirsute capillaries, from chaetiger 8 or 9 in juveniles and from chaetiger 11 or 12 in adults additionally one or two hooded hooks ( Figures 1H, 2E), usually only slightly bent, uni-or bidentate ( Figure 1H); with appearance of hooks, the number of capillaries decreases considerably, one or two capillaries up to chaetiger 14 at most, in posterior chaetigers two or three neuropodial hooded hooks, uni-, bi-or sometimes tridentate ( Figure 2F); spines, with longitudinal groove basally ( Figures 1F, G, 2C, D) first appear on chaetiger 14 on specimens with more than 28 chaetigers in total (one specimen with 33 chaetigers without spines as an exception), only one grooved spine per neuropodium present, grooved spines replace hooded hooks from chaetiger 14 up to chaetiger 20, depending on total number of chaetigers (Table I), sometimes on posteriormost spine-bearing neuropodia one hooded hook present additionally; spines are 10-12 mm in diameter at the very base, posterior spines sometimes thinner; grooved spines associated with glandular organs (Figures 1F,  2C, 3B). Glandular organs about 25-35 mm in diameter ( Figure 3A, B). Sabre chaetae (recurved chaetae with a broad blade in the ventralmost position of the neuropodia) absent. Pygidium with four anal lobes, maximum about 58 mm in length. No discernible methyl green or Shirlastain AH staining pattern.

Additional observations
The hooded hooks and spines are sometimes asymmetrically arranged. For example, hooded hooks are first present only on one side of the body, whereas the corresponding neuropodium of the other side still bears capillaries. In other cases, spines may be developed in some neuropodia, whereas hooded hooks are present on the corresponding neuropodia of the other side.

Etymology
The species is dedicated to Dr Jü rgen Laudien of the Alfred-Wegener-Institut Bremerhaven. He collected some of the specimens and he assisted us greatly during our field investigations on Spitsbergen in June 2003.

Geographical distribution
Species known only from the type locality.

Discussion
Glyphochaeta laudieni sp. n. is unique among ''Spionidae'' in having grooved spines connected with glandular organs in some middle neuropodia ( Figures 1F, 2C, D, 3B). The position of the species within the ''Spionidae'', however, is not clear. Glyphochaeta shares the absence of branchiae within ''Spionidae''-as currently defined (excluding Apistobranchidae, Longosomatidae, Poecilochaetidae, Trochochaetidae, and Uncispionidae)-only with Spiophanes. Moreover, large parapodial glandular organs in the middle body region are present only in Glyphochaeta and Spiophanes. In Spiophanes these glandular organs are present from chaetiger 5 to about chaetiger 13-15 (Meißner and Hutchings 2003), whereas in Glyphochaeta they first appear from chaetiger 14. The structure of these glands is completely different as well. In Spiophanes the glandular organs producing ''bacillary chaetae'' are mainly composed of a large glandular sac and an accessory gland taking up almost the whole chaetiger (unpublished data), whereas in Glyphochaeta the glands are restricted to the neuropodia (Figure 3). In Glyphochaeta the glands probably produce a liquid secretion, and the attached grooved spines may act as a moving open drain ( Figures 1F, 2C, D, 3B). A potential convergent development of glandular organs and a convergent reduction of branchiae in Spiophanes and Glyphochaeta cannot be excluded. Most characters mentioned in the diagnosis of Spiophanes provided by Meißner and Hutchings (2003) are absent in Glyphochaeta.
Comparable glandular organs have also been described in other species of spionids, for examples the ''poches glanduleuses'' in Polydora (Claparède 1870), the ''podialen Drü senorgane '' in Microspio, Pygospio, and Spio (Sö derströ m 1920), or the glands in the fifth chaetiger of juvenile Polydora ciliata (Johnston, 1838) (Hannerz 1956). These glands are usually smaller than those found in Spiophanes or Glyphochaeta, but they are also connected with neuropodial chaetae as in Glyphochaeta (except for P. ciliata). Comparative studies into homologies of the glandular structures in spionids remain to be performed.
The function of the grooved spine as a drain seems apparent, yet the function of the secretion is obscure. The specimens were found only in samples with colonies of Bryozoa. The samples from the bottom of the grotto with a high amount of detritus never contained G. laudieni sp. n. All specimens were found free in the samples, without any indication of a tube, so that this gland is probably not involved in formation of a tube. This assumption is reinforced by the absence of spines in juvenile specimens. Spines first appear when about 28 chaetigers have been developed (Table I). The presence of spines in adults may indicate a reproductive function. The small size of the species points to a low number of larvae and a lecithotrophic or direct development, although this hypothesis remains to be tested.
The appearance and the shape of hooded hooks have been regularly used in taxonomic descriptions. The first appearance of hooks in juveniles is most important for phylogenetic analyses. It has already been used in the cladistic analysis of Prionospio and related genera (Sigvaldadó ttir 1998). The first appearance of hooks is often invariable (e.g. Polydora complex, Pygospio, Streblospio), but in other cases their presence depends to a certain extent on the total number of chaetigers (and it is only useful for identification at best, e.g. Marenzelleria, Prionospio, Spio). In G. laudieni sp. n. the hooded hooks first appear on chaetiger 8 or 9 in the smallest specimens but in chaetiger 11-12 in adults; thus, as the individuals grow, the first hooks become displaced two to four chaetigers backwards. This minor shift of hooks is probably the most common case among spionids. The first appearance of neuropodial hooded hooks at chaetiger 8 is not unusual: it has been recorded for example in certain genera of the Polydora complex and in some species of Pygospio and Streblospio. Interesting in this context is that Sö derströ m (1920) described a transformation of bidentate hooded hooks into spoon-like hooks (''lö ffelfö rmige Borsten'') in the neuropodia of chaetigers 8-11 of mature P. elegans Claparède, 1863. This transformation was also described by Berkeley and Berkeley (1954) from a single specimen from Nova Scotia and by Light (1977) from specimens from California. The California specimens exhibit spoon-like hooks in chaetiger 8 through to chaetiger 10 or 12. Hilbig (1982) provided SEM micrographs of these spoon-like hooks. The hooks possess a groove on the concave side; hoods are still present, but the hood may be opened at the concave side of the hook. Adult P. elegans from the Baltic Sea also possess these modified hooded hooks (personal observation). Some of these hooks resemble those described for P. elegans by Sö derströ m (1920), whereas others resemble those found on species of the Atherospio complex (sensu Mackie 1996) (personal observation). The transformation of hooded hooks parallels that found in G. laudieni, because already Sö derströ m (1920) concluded that the development of the spoon-like hooks was a function of age and that they derived from a transformation of the bidentate hooded hooks as the specimens matured. In Glyphochaeta, however, the hooded hooks of chaetiger 14 and subsequent chaetigers are replaced by grooved spines without a conspicuous hood ( Figure 2D), and the spines are a great deal thicker. Additional similarities with P. elegans are the absence of sabre chaetae, the presence of neuropodial glands, and the number and shape of anal cirri. Therefore, an assignment of Glyphochaeta into the third group (with P. elegans, the Atherospio complex, and Pseudopolydora primigenia Blake, 1983) of the strict consensus tree provided by Mackie (1996) is most likely.