POLYCIRRIDAE CHARACTERS

Fitzhugh, Kirk, Nogueira, João Miguel De Matos, Carrerette, Orlemir & Hutchings, Pat, 2015, An assessment of the status of Polycirridae genera (Annelida: Terebelliformia) and evolutionary transformation series of characters within the family, Zoological Journal of the Linnean Society 174 (4), pp. 666-701 : 694-697

POLYCIRRIDAE CHARACTERS

We alluded to the issue of ‘inapplicable’ coding as a possible cause of the non-monophyly of Lysilla relative to Amaeana , as well as the fact that there are no synapomorphies currently recognized for Polycirrus . In this section we present some of the transformation series of characters that also contribute to the questionable standings of Polycirrus , Lysilla , and Amaeana .

Anterior end ( Fig. 13 )

Restriction of the transverse prostomium [cf. character 2(1)] to the base of the upper lip [character 3(0)] is plesiomorphic for Polycirridae , whereas the distal part of the prostomium extending to near the anteri- or margin of the lip [character 3(1)] forms a grade among members of Biremis blandi , Hauchiella tribullata , and several Polycirrus species , as well as a synapomorphy for the Polycirrus octosetus – Enoplobranchus sanguineus clade; character 3(0) is then a synapomorphy at the level of more apomorphic members of Polycirrus , as well as Lysilla and Amaeana . The mid-dorsal process on the anterior margin of the prostomium [character 6(1)] within Polycirridae is restricted to three separate clades among members of some Lysilla and Amaeana . Buccal tentacles with spatulate tips [character 10(1)] is the plesiomorphic condition for Polycirridae . Among members of a clade within Amaeana , however, buccal tentacle tips are broad [character 10(0)], which independently occurs among members of Lysilla pacifica . The expanded lower lip [cf. character 14(0)] being cushion-like across the ventrum [character 15(2)] is plesiomorphic for Polycirridae , whereas the lip is mid-ventral [character 15(1)] among members of more apomorphic Polycirrus [except for the putative reversal to character 15(2) among members of Polycirrus octosetus ], Enoplobranchus , Lysilla , and Amaeana .

Anterior segments ( Fig. 14 )

The visibility of segment 1 (subject 17) presents considerable variation among members of Polycirridae . It is possible that visibility is dependent upon the state of preservation of the specimens, as segment visibility is strongly influenced by the extension of the prostomium, which frequently covers segment 1 laterally, and sometimes also dorsally. Among members of the most plesiomorphic polycirrids, which have a cushion-like lower lip, as discussed above, segment 1 is not usually visible, at least ventrally [characters 17(2) or 17(3)], because of the expanded lip. Among members of species with a short, mid-ventral lower lip, segment 1 is visible at least ventrolaterally [characters 17(0, 1, 4, or 5)].

Lightly papillate glandular ventrolateral pads [character 23(0)] is the plesiomorphic condition for Polycirridae , but with several independent derivations of the densely papillate condition [character 23(1)] among members of several Polycirrus species and Hauchiella , as well as a synapomorphy for the Lysilla – Amaeana clade.

Nephridial and genital papillae are usually restrict- ed to a few anterior segments [characters 26(1) and 27(0)] among members of Terebelliformia , frequently on segments 5–7 in the telothelepodids and segments 4–7 in the thelepodids, for example. Among the polycirrids, the plesiomorphic condition is absence of papillae [character 26(0)], but with subsequent derivation of papillae [character 26(1)] among most members of the family, along with several putative losses among members of some species of Hauchiella , Polycirrus , Enoplobranchus , and Lysilla . Regarding the distribution of genital papillae, there is a general tendency towards an increase in the number of pairs of papillae related to the number of pairs of notopodia: from papillae only present on some anterior segments [character 27(0)]; to presence extending to the mid-body but terminating well before notopodia [character 27(1)]; to presence on all, or nearly all, notopodia [character 27(2)].

Parapodia ( Fig. 15 )

Polycirrids are remarkable for the reduction of parapodia, frequently with loss of one or both parapodial rami. According to our results, the loss of notopodia [character 30(1)] among members of Biremis blandi , loss of neuropodia [character 30(0)] among members of Enoplobranchus and Lysilla , and loss of noto- and neuropodia [character 29(1)] among members of Hauchiella occurred independently.

In addition, there is a general tendency towards a reduction in the number of pairs of notopodia among members of Polycirridae species. When present, notopodia begin on segment 3, as is also the case among members of Telothelepodidae . Except for Polycirrus parvus , which has fewer pairs, the most plesiomorphic members of polycirrid species have notopodia extending to mid-body [character 32(1)]. Members of more apomorphic taxa have notopodia restricted to 12 segments at most [character 32(0)], usually around ten, although several independent reversals occur to a greater number. Notable examples of reduced numbers of notopodia occur among Polycirrus octosetus and Lysilla loveni Malmgren, 1866 , each with eight pairs, or Lysilla macintoshi Gravier, 1907 , with five or six pairs of notopodia extending to segments 7–8.

The plesiomorphic condition for neuropodia distribution is that they begin immediately after the termination of notopodia [character 31(3)]. This condition is found among most members of Polycirrus , but within this grade are several independent modifications: neuropodia beginning on last one or two segments with notopodia [character 31(1)], neuropodia on anterior segments [character 31(0)], or neuropodia limited more posteriorly [character 31(2)]. Neuropodia are absent among all members of Lysilla , but are present among all members of Amaeana , beginning after notopodia terminate [character 31(2)], resulting in an achaetous gap of several segments.

The plesiomorphic condition for the distally bilobed condition of notopodia [cf. character 35(1)] is that the postchaetal lobes are longer than prechaetal lobes [character 36(1)], with more apomorphic members of Polycirrus [except Polycirrus octosetus , with character 36(1)], Lysilla , and Amaeana , with lobes of about the same length [character 36(0)].

Chaetae ( Fig. 16 )

Notochaetae are winged [characters 38(1), 40(1)], with relatively wide wings [characters 39(1), 41(1)] among members of the Telothelepodidae and plesiomorphic Polycirridae . Anterior notochaetal rows are pinnate [character 38(2)] among most members of Polycirrus and Lysilla . A reversal to the winged character occurs in the clade comprising the most apomorphic members of Lysilla , L. loveni and L. jennacubinae , as well as all members of Amaeana , but chaetae are narrowly winged in this latter clade. The pattern of distribution of pinnate notochaetae in posterior rows [character 40(2)] among members of Polycirrus differs from that in anterior rows in that they are limited to more apomorphic members.

The traditional definitions of Amaeana and Lysilla are the absence of neuropodia [cf. character 30(0); Table 1] among members of Lysilla , whereas members of Amaeana bear neuropodial acicular spines [character 42(2)]. The present results deny such a distinction given the paraphyletic status of Lysilla relative to Amaeana . Regarding the types of neurochaetae, type-1 uncini [characters 42(1), 43(0), 45(0), and 46(0)] are plesiomorphic, occurring among members of Biremis blandi and most included members of Polycirrus , whereas more apomorphic members of Polycirrus species have type-2 uncini [characters 42(1), 43(1), 45(1), and 46(1)].

Posterior end ( Fig. 16 )

The plesiomorphic condition for the pygidium among members of Polycirridae is smooth to crenulate [character 50(0)], with the papillate condition [character 50(1)] present among members of most included Polycirrus species , Hauchiella , Enoplobranchus , Lysilla , and Amaeana . The overall transformation series is, however, quite tentative as in many cases the specimens examined were not complete and the pygidium is unknown.

Figures

Figure 13. One of the 54 minimum-length cladograms, showing transformation series for selected characters (see also Figs 14–16) that contribute to the non-monophyly of Polycirrus, Lysilla, and Amaeana.

Figure 14. One of the 54 minimum-length cladograms, showing transformation series for selected characters (see also Figs 13, 15–16) that contribute to the non-monophyly of Polycirrus, Lysilla, and Amaeana.

Figure 15. One of the 54 minimum-length cladograms, showing transformation series for selected characters (see also Figs 13–14, 16) that contribute to the non-monophyly of Polycirrus, Lysilla, and Amaeana.

Figure 16. One of the 54 minimum-length cladograms, showing transformation series for selected characters (see also Figs 13–15) that contribute to the non-monophyly of Polycirrus, Lysilla, and Amaeana.