Spiophanes Grube, 1860

MEISSNER, Karin & Hutchings, Pat A., 2003, Spiophanes Species (Polychaeta: Spionidae) From Eastern Australia-With Descriptions of New Species, New Records and an Emended Generic Diagnosis, Records of the Australian Museum 55, pp. 117-140 : 118-120

Genus Spiophanes Grube, 1860 , emended

Spiophanes Grube, 1860: 88–89 , pl. 5, fig. 1. Type species: S. kroyeri Grube, 1860 , by monotypy.

Morants Chamberlin, 1919: 17 . Type species: M. duplex Chamberlin, 1919 , by monotypy. Junior synonym.

Diagnosis. Prostomium broad anteriorly; subtriangular, bellshaped or rarely rounded; anterior margin often laterally extended, forming horns of different length; with or without occipital antenna (Fig. 2A,C). Eyes present or absent. Nuchal organ as 2 parallel ciliated bands along dorsum, maximally extending to chaetiger 16 (Fig. 2C) or as pair of dorsal loops not extending beyond chaetiger 4 (Fig. 2A). Peristomium moderately to well developed, forming lateral bulges or wings. Branchiae absent. Dorsal ciliated crests usually present. Body divided into 3 different regions: (a) Anterior region extending up to chaetiger 4: with parapodia 1–4 usually exhibiting well-developed neuro- and notopodial postchaetal lamellae compared to those of subsequent chaetigers, often positioned dorsally or dorsolaterally. (b) Middle body region: extending from chaetiger 5 to last chaetiger bearing capillary chaetae rather than hooks in neuropodia (chaetiger 13, 14 or 15 depending on species). Chaetigers usually with parapodial glandular organs: anterior organs exhibit a chaetal spreader in gland opening (Fig. 1A–E); from chaetiger 9, gland opens as simple vertical slit (Fig. 2D), often surrounded by pigmented cells. (c) Posterior region:indicated by presence of neuropodial hooks; largest number of hooks usually in first chaetigers of this region. Ventrolateral intersegmental genital pouches present or absent between neuropodia (Fig. 2H).

Notochaetae as capillaries, often limbate or hirsute, in middle body region usually in 3 rows. Neuropodia of chaetiger 1 with 1–2 conspicuous crook-like chaetae.

Neurochaetae of chaetigers 1–4 simple, hirsute or limbate capillaries arranged in 2 rows. From chaetiger 5 neurochaetae short, broad, often bilimbate and distally pointed; arranged in 1–2 indistinct rows. Neuropodial hooks first present from chaetiger 14, 15 or 16; quadridentate, with main fang surmounted by single unpaired tooth and pair of smaller distal teeth, additional small teeth rarely present; hood absent or present (Fig. 2F,G). Bacillary chaetae may be exposed from chaetigers 5–8, emerging from inside the parapodium along slit between chaetal spreader and gland opening (Fig. 2E). One to 2 ventral sabre chaetae from chaetiger 4, or sometimes not present until neuropodial hooks appear; sabre chaetae accompanying the hooks often with cryptic ridge (easy to observe under the SEM, difficult to observe with light microscopy) (Fig. 2F). Stout, curved notochaetae often present in far posterior parapodia (Fig. 2B). Pygidium with 2 or more anal cirri.

Remarks. The present diagnosis is based on examinations of type and non-type specimens of every species in the genus. The major changes from past diagnosis concern chaetal arrangements along the body, and characters related to the glandular organs in the middle body region. The arrangement of neurochaetae on chaetigers 1–4 in two rows and of notochaetae on chaetigers of the middle body region in three rows has been found to be present in all species of Spiophanes . However, the interpretation of the chaetal arrangement may depend on the number of chaetae in a ramus; if small numbers of chaetae are present, their arrangement in rows may be difficult to discern. In the neuropodia of the middle body region, a large number of chaetae are present in two indistinct rows, whereas smaller numbers of chaetae usually appear to be arranged in a single row. Therefore, the arrangement of chaetae in a specific number of rows is not a useful specific character.

In the middle body region, different forms of gland openings occur. Useful taxonomic information is given by the gland openings presenting a chaetal spreader, the type of which is species specific. The description of the different types and explanations concerning their terminology was given earlier. According to Söderström (1920), the chaetal spreader function is closely related to the function of the bacillary chaetae. Therefore, it is suggested that bacillary chaetae may be present only in parapodia where chaetal spreaders are developed, rather than potentially being present in the entire glandular region (compare, e.g., Foster, 1971; Imajima, 1991; Blake, 1996; Maciolek, 2000). This assumption is supported by our own observations that, in cases where bacillary chaetae are exposed, they are only present in chaetigers with chaetal spreaders developed. From chaetiger 9, glands are obviously producing material similar to bacillary chaetae, which in preserved material resembles a sort of white fibre wool. The appearance of bacillary chaetae probably cannot serve as a useful diagnostic character. Observed differences in the appearance of the chaetal tip or in the arrangement of fine hairs of varying or constant length covering the shafts of the bacillary chaetae have previously been considered as species specific. Based on our observations, the observed differences may just represent a different state of condition.

From chaetiger 9, parapodial glands often have associated pigmented cells which also appear to be useful for species identification.

SEM studies revealed that all known species in the genus possess quadridentate hooks. Previous reports of bi- or tridentate hooks might be due to teeth being worn down or a slightly lateral position of the uppermost pair of small teeth, e.g., in S. bombyx Claparède, 1870 , which is usually positioned clearly above the unpaired tooth surmounting the main fang and hence allows easier recognition of all four denticles when viewed with light microscopy.