Polycirrus Grube, 1850

Nogueira, João Miguel Matos, Hutchings, Pat & Carrerette, Orlemir, 2015, Polycirridae (Annelida, Terebelliformia) from Lizard Island, Great Barrier Reef, Australia, Zootaxa 4019 (1), pp. 437-483 : 448-449

Genus Polycirrus Grube, 1850 , emended

Polycirrus .— Hutchings & Glasby 1986: 330 –332; Glasby & Hutchings 2014: 13 –14.

Type-species. Polycirrus medusa Grube, 1850 , by monotypy.

Diagnosis. Transverse prostomium attached to dorsal surface of upper lip, usually covering segment 1 laterally and extending ventrally, terminating lateral to mouth; basal part of prostomium usually as thick crest; crest almost straight, horseshoe-shaped, curved to semicircular, or inverted V-shaped, probably strongly dependent on preservation. Distal part of prostomium low, of uniform length, restricted to base of upper lip, sometimes as flaring lobe, or extending along the lip and terminating near anterior margin. Buccal tentacles of at least two types, short ones uniformly cylindrical, long ones spatulated; modified stouter and longer tentacles with specialised tips may be present. Peristomium forming lips; upper lip large, frequently circular and convoluted, folded into three lobes; swollen lower lip, entire or divided into two parts, varying from button-like, restricted to oral area, to expanded as cushion-like structure, and sometimes occurring across entire ventrum. Segments throughout biannulated or with more annulations; segment 1 reduced, usually visible dorsally and ventrally, laterally covered by expanded prostomium. Segment 2 distinctly narrower than following segments, usually with rectangular or pentagonal midventral shield at beginning of mid-ventral groove, sometimes extending anteriorly through segment 1 until near posterior margin of lower lip. Body wall papillate throughout, papillae distinctly larger and more abundant on ventro-lateral pads of anterior segments, present usually from segment 2 to last with notopodia. Notopodia beginning from segment 3, extending for variable number of segments, terminating anteriorly in most taxa; bilobed, elongate notopodia, lobes about same size or post-chaetal lobe longer. Notochaetae winged, with wings of variable width, and/or pinnate. Neuropodia, beginning posteriorly to notopodia, frequently only after notopodia terminate; neurochaetae as avicular uncini of types 1 or 2. Nephridial and genital papillae usually present, anterior to bases of all notopodia, or only anteriorly. Pygidium smooth or with rounded ventral papilla.

Remarks. Polycirrus is a well-known genus of Terebelliformia, but the taxonomy of its species has always been considered as difficult. Recently, Glasby & Hutchings (2014) reviewed the group, designated a neotype for the type species, P. medusa Grube, 1850 , and provided redescriptions for all species in this genus based on reexamination of type material.

The diagnosis above emends that by Glasby & Hutchings (2014) because it does not consider the hirsute-type of notochaetae of Glasby & Hutchings (2014). Wings of notochaetae of Polycirrus are of variable width, usually conspicuous under intermediate magnification of light microscopy, broadly-winged sensu Fitzhugh et al. (2015), but some species have very narrowly-winged chaetae, acicular, with wings inconspicuous under higher magnifications of light microscopy, as also occurs in some species of Amaeana and Lysilla . In the case of the species with broadly-winged notochaetae, sometimes the layers of chitin of the wings spread apart and these chaetae may assume a hirsute appearance under light microscopy. Under the SEM, however, the wings are always hirsute, independent of state of preservation, even in acicular chaetae, and the only variation observed is in the width of the wings.

On the other hand, in some cases Glasby & Hutchings (2014) considered as “hirsute” chaetae that in our opinion are pinnate. For instance, Glasby & Hutchings described the notochaetae of P. latidens as hirsute, however in all cases we have seen chaetae with regularly arranged “hairs” under light microscopy, as represented in their Fig. 33c ( Glasby & Hutchings 2014: 65), they are pinnate under the SEM. For these reason, we consider the hirsute type of notochaetae of Glasby & Hutchings (2014) as misleading, as it may refer to poorly preserved broadlywinged or to pinnate chaetae.

Glasby & Hutchings (2014) suggested an intraspecific variation of 5 segments on the number of pairs of notopodia, and of 4 segments on the beginning of neuropodia, and that these two characters were independent of each other. We consider, however, these characters are linked, so that a variation in the number of pairs of notopodia implies in similar variation in the beginning of neuropodia. So, the relative distance between termination of notopodia and beginning of neuropodia is more important than segment numbers where these occur, considering some little variation in segment numbers may occur.

Several other characters of polycirrids are also directly related to the number of pairs of notopodia. Frequently, the paired ventro-lateral pads are present until the segment on which notopodia terminate, although they may be less conspicuous posteriorly. Furthermore, the body is usually swollen anteriorly and tapers abruptly on last segments with notopodia. Similarly, in most species, nephridial and genital papillae are present anterior to bases of all notopodia. An intraspecific variation on the number of pairs of notopodia also implies variation in the number of pairs of ventro-lateral pads and nephridial and genital papillae present. For that reason, in most taxa the termination of notopodia determines the transition between a thorax and an abdomen. Such demarcation is not clear in specimens of several taxa of Terebelliformia, and because of that Nogueira et al. (2010, 2013) suggested the names “thorax” and “abdomen” should be used with caution, but it is usually conspicuous among polycirrids.

In regards to beginning of neuropodia, we suggest that four groups of Polycirrus can be recognized, those in which: (1) neuropodia begin on anterior segments, up to segment 10; (2) neuropodia begin near to the termination of notopodia, on the last segment with notopodia, or close to that (with an obvious overlap between groups 1 and 2 in the cases of species with few pairs of notopodia); (3) neuropodia begin immediately to shortly after the termination of notopodia; (4) neuropodia begin more posteriorly, with a gap of several achaetous segments between termination of notopodia and beginning of neuropodia (see Fitzhugh et al. 2015). Within each group, a variation of some segments is acceptable, but usually no more than three segments.

However, except for few cases of aberrant specimens, we have never observed any intraspecific variation which would cause an overlap between groups 2 and 3. A variation in the number of pairs of notopodia present is accompanied by a similar change in the beginning of neuropodia, so that a variation between “neuropodia beginning on the last segment with notopodia, or close to that” and “neuropodia beginning immediately or shortly after notopodia terminate” does not occur, even if that means a difference of a single segment.

We also interpret the types of uncini slightly differently from Glasby & Hutchings (2014). Glasby & Glasby (2006) divided the types of uncini of Polycirrus into two types, based on morphometrics. However, the differences between types 1 and 2 of uncini should be based on not only morphometrics but also on other characters. For example, type 1 uncini are usually minute, with short, triangular heel directed posteriorly, relatively high base, horizontally aligned with the heel, and a short neck; while type 2 uncini are usually larger, with longer heel directed downwardly, low base, at an angle with the heel, and elongate neck. For this reason, some uncini which would be considered by Glasby & Hutchings (2014) as type 2 are treated herein as type 1, such as in the case of P. culcita n. sp. (see below).