Notophyllum

Kato, Tetsuya & Pleijel, Fredrik, 2002, A revision of Notophyllum Örsted, 1843 (Phyllodocidae, Polychaeta), Journal of Natural History 36 (10), pp. 1135-1178 : 1140-1143

Morphology of Notophyllum

The shape of the prostomium may be rounded, pentagonal or triangular, although the diOEerences are poorly de nable and variable from specimen to specimen. An antero-ventral ciliated elongation is always present (gure 1A). There are two pairs of similar frontal appendages of which the dorsal pair is labelled antennae, and the ventral pair palps (homologous to palps in other Phyllodocida , e.g. Nereididae ). A single pair of large rounded eyes is always present, and a median antenna is inserted between the eyes. The relative length of antennae and palps varies both within and between species.

Details of the proboscis are highly variable within Notophyllum and provide an important source of characters which has been little explored previously. Length and width in relation to overall size of the animal varies and is potentially informative. The lateral, longitudinal rows of papillae can consist of a single or several more or less merged rows, and the extension of the rows along the proboscis diOEers. The papillae in these rows can be discoidal, rounded or hooked-shaped, and may vary in shape from the proximal to the distal part of the proboscis (gure 1B, C) (all descriptions of proboscis characters refer to the proboscis as seen in everted condition). On each side of the proximal-most, dorso-lateral part of the proboscis there is a group of large papillae which varies in number.

The dorsal and ventral surfaces of the proximal part of the proboscis are covered by minute rounded papillae, the distal part by large rounded to attened papillae; shape and relative size of these papillae provide further information, as does the ratio between length of proximal and distal parts. The terminal ring is smooth and lacks papillae.

The number of lobes of the nuchal organs has traditionally been employed to distinguish diOEerent species of Notophyllum . The character is problematic in that the number of lobes increases with increasing body size, and also in that considerable interspeci c overlap is found between smaller specimens (gure 2). Although not uninformative, it should be used with due consideration to overall size.

Size diOEerences of segments 1 and 2, as seen in dorsal view, provide more, previously unrecorded information. However, careful examination is needed, as these segments are occasionally covered by the posterior margin of the prostomium, especially in large specimens.

The cirri of segment 1, the dorsal and ventral cirri of segment 2, and the dorsal cirri of segment 3 diOEer in shape from following dorsal and ventral cirri in being long, cylindrical and usually tapered, and are here labelled ‘tentacular cirri’ in accordance with previous phyllodocid literature. The length of these cirri exhibits interspeci c diOEerences, although important intraspeci c variation is present in N. foliosum . The ventral tentacular cirri of segment 2 are asymmetrical and posteriorly directed in Notophyllum . Segments 2 and 3 are both provided with single dorsal and ventral aciculae.

Neuropodial chaetae occur from segment 2 and are inserted on the anterior side of the ventral tentacular cirrophores. From segment 3 and onwards they emerge from the neuropodial lobes. Number of chaetae varies between species, although not in a very xed pattern and is also related to body size.

Segment 4 and following segments lack notoaciculae and are provided with reniform, attened dorsal and ventral cirri. Notoaciculae reappear from segment 12–15, and may be accompanied by a single or a few capillary notochaetae. The number of dorsal aciculae has been reported as variable (e.g. Izuka, 1912: 200; Pleijel, 1993: 7), although we have in no instance observed more than one.

The shape of the dorsal cirri is broad reniform in adult Notophyllum . In juveniles of N. foliosum the dorsal cirri are cordate with distinct tips (which may be retained in adults), whereas they are rounded to reniform without tips in N. japonicum and N. imajimai ; they are unknown in other species. The shape of the dorsal cirrophores shows little intraspeci c variation, and are dorsally elongated in some species and symmetrical in others. Notochaetae are unornamented, simple capillaries, and emerge from the cirrophores (gure 1D); they may be present or absent, although careful examination of a series of parapodia is necessary since they are di cult to detect and apparently easily lost. The shape of the neuropodial lobes varies in relation to body size and position along body; this character was not explored further due to di culties in interpreting the variation. The ventral cirri are reniform, with the longitudinal axes obliquely orientated as in other Notophyllinae . The ventral cirri of the posterior segments tend to be more pointed, although there are considerable diOEerences between neighbouring segments. The neurochaetae are all compound (gure 1E). Within Notophyllum we were unable to detect any consistent variation in chaetal morphology.

The pygidial cirri are always rounded and attened, although unknown in some species, and a pygidial papilla is present (gure 1F).

The colour and pigmentation pattern of live Notophyllum are highly variable and informative, although unfortunately rarely documented. In some taxa the patterns may be retained in well-preserved specimens and provide additional means of indenti cation.