Parahololepidella greeffi ( Augener, 1918 )

Britayev, Temir A., Gil, João, Altuna, Álvaro, Calvo, Marta & Martín, Daniel, 2014, New symbiotic associations involving polynoids (Polychaeta, Polynoidae) from Atlantic waters, with redescriptions of Parahololepidella greeffi (Augener, 1918) and Gorgoniapolynoe caeciliae (Fauvel, 1913), Memoirs of Museum Victoria 71, pp. 27-43 : 28-34

Parahololepidella greeffi ( Augener, 1918)

Zoobank LSID. http://zoobank.org/ urn:lsid:zoobank.org:act:

FAED770C-2A9C-4EF6-AEC2-156863AED046

( Figs. 1-7 )

Hololepidella greeffi : Augener (1918), p. 148, pl. 2, figs. 22-24, pl. 3, fig. 52, text-fig. 9; Hartman (1959), p. 81; Rullier (1964), p. 130, fig.3.

Hololepidella fagei : Rullier (1964), p. 132, fig. 4; Hartman (1965), p. 9.

Parahololepidella greeffi : Pettibone (1969), p. 54 –55, fig. 4; Kirkegaard (1983), p 192.

Material examined. Cabo Verde Archipelago.Santiago Island, SW coast near Ponta da Cidade , 14°54'N 23°38'W . Sta. CANCAP 7.D01, depth to 22 m, one specimen af and pf ( NNMN 24481 ) on Tanacetipathes cf. spinescens , loose boulders on coarse sand, scuba diving, 20- 21.08.1986, “ Tydeman ” Cabo Verde Islands Exped., 1986. W of Boa Vista Island, W of Ilhéu de Sal Rei , 16°11'N 23°00'W , Sta. CANCAP 7.081, depth 70 m, one complete specimen ( NNMN 24644 ) on Tanacetipathes cf. spinescens , antipatharians and sponges, 1. 2 m Agassiz trawl, 28.08.198 6, “ Tydeman ” Cabo Verde Islands Exped., 1986. 00º00´57.94”N

MNCN Catalogue Date Reference N Island Station Coordinates WT Depth 14/01/06 16.01/13707 8 São Tomé Is. Lago Azul 2 00º24´19.0” N 06º36´26.6” E 27 20-25 15/01/06 16.01/13708 4 São Tomé Is. Diogo Vaz 2 00º18´97.1” N 06º30´23.3” E 28 5-15 15/01/06 16.01/13709 1 São Tomé Is. Diogo Vaz 1 00º18´53.2” N 06º29´23.3” E 27 20-25 18/01/06 16.01/13704 1 São Tomé Is. - Rolas Is. Pedra do Braga 00º00´57.94”N 06º30´52.03”E 28 15-20 18/01/06 16.01/13706 1fr São Tomé Is. - Rolas Is. Pedra do Braga 00º00´57.94”N 06º30´52.03”E 28 15-20

18/01/06 16.01/13705 1 São Tomé Is. - Rolas Is. Pedra do Braga 28 15-20 06º30´52.03”E

São Tomé e Príncipe Archipelago. 1 syntype, Ilha das Rolas , Zoological Museum of Hamburg ( ZMH 5692 ); 16 worms (plus some fragments) on Tanacetipathes cf. spinescens , collected during the Republic of São Tomé e Príncipe ( RSTP) cruise by CPD Service Supporting Science Research ( Table 1) .

Description. Based mainly on a well-preserved specimen, broken in two fragments, NNMN 24481). Body long, slender, dorso-ventrally flattened, with sides nearly parallel, tapering posteriorly, with up to 140 or more segments (figs. 1, 2). Without dorsal ciliary bands.

Prostomium slightly wider than long; cephalic peaks present or absent; ceratophore of median antenna in anterior notch, style smooth, tapering, longer than palps; lateral antennae inserted ventrally to median antenna, styles smooth, tapering; anterior pair of eyes dorso-lateral on widest part of prostomium, posterior pair dorsal, near posterior prostomial margin, slightly smaller than anterior ones; palps tapering. Facial tubercle prominent; mouth surrounded by two lateral lips, one dorsal with 6-7 lobes, and one large ventral lip with 7-9 lobes. Pharynx with four light-brown jaws, all similar in shape and size; nine pairs of large marginal pharyngeal papillae.

First (tentacular) segment with a pair of tentaculophores inserted laterally to prostomium, with one, rarely two aciculae and one slightly serrated unidentate notochaeta, with dorsal and ventral tentacular cirri, styles smooth, tapering. Second (buccal) segment with first pair of elytra, sub-biramous parapodia and long, tapering ventral cirri. Nuchal fold absent. Following segments with ventral cirri short, not reaching to tip of neuropodium. Cirrigerous segments without dorsal tubercle. Dorsal cirri smooth, with cylindrical, relatively long cirrophores and very long styles.

Elytra numerous up to 50 and more pairs, on segments 2, 4, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 26, 29, 32, thereafter irregularly arranged on alternate segments, often asymmetrical, with different number on right and left sides ( Table 2). Elytra almost oval in outline, smooth, soft, tubercles and micropapillae absent; first 11-12 pairs slightly folded, medium sized, usually covering mid-dorsum; following ones, very small, leaving mid-dorsum and parapodia uncovered (fig. 3).

Parapodia sub-biramous (fig. 4A). Notopodia small, digitiform (fig. 4B). Neuropodia with longer rounded prechaetal lobes with subacicular digitiform acicular lobe; postchaetal lobes shorter, distally rounded; tips of noto- and neuroacicula penetrating epidermis (figs. 4B-4D, 5A, 5B). Nephridial papillae short, bulbous, starting on segment 6 (fig. 4E).

Notochaetae slightly thinner than neurochaetae, few in number (0-5), nearly smooth, unidentate; neurochaetae few in number, but more numerous (5–10) than notochaetae, with unidentate tips and faint serration, all of same type (fig. 4F, 4G).

Surface of elytra and body often covered with scattered, angular, extraneous particles.

Measurements. 75-120 chaetigers, L 26-44 mm, WW 1.2-1.5 mm, WC 2.6-3.3 mm ( Table 2).

Colour. Living worms not seen. Alcohol preserved worms with light brown background, a prominent dark brown longitudinal mid-dorsal band along all body (figs. 1A, 1C, 2), and dark brown pigmentation on cirrophores and, sometimes, on bases of cirri. Some specimens may also show a longitudinal dark brown band on ventral side, narrow in anterior segments, occupying nearly all body width from mid-body to posterior end (fig. 1B, 1D).

Remarks. Our specimens agree well with Pettibone’s (1969) description. However, the syntype deposited at the ZMH was in a very poor state of preservation, being almost dehydrated (fig. 6A), to the extent that the the chaetae were damaged (fig. 6B). The material from the museum included a few dissected parapodia in an additional jar, which appeared to be in better conditions (fig. 6D-F). The only differences with the parapodia of the newly collected material were that the neurochaetae seemed to be slightly thicker in the syntype, two of them appearing slightly bidentate (black arrow, fig. 6E). Taking into account the conditions of this material, however, we cannot dismiss the possibility that these two traits could have been caused by the dehydrating process suffered by the syntype.

Some of the features commonly used to discriminate species and, even, genera among polynoids are highly variable within the newly collected material. For instance, specimen MNCN 16.01/137094 lacks cephalic peaks, while they are present in specimen NNMN 24644. Also, the elytra distribution becomes asymmetrical (within a given worm) and irregular (between worms) from chaetiger 32 or 33 to the end of the body ( Table 2). A similar variability was also described for another long bodied species, Medioantenna variopinta ( Di Camillo et al., 2011) . The shape of elytra may also vary. They are relatively large, covering prostomium and mid-dorsum up to chaetigers 15–23, becoming then very small and leaving the dorsum uncovered. However, several specimens also show some small anterior elytra leaving the dorsum uncovered, we suggest this being caused by the presence of regenerating (small) elytra and/or parapodia. The restricted distribution of these damaged elytra and/or parapodia, lead us to attribute its presence to intra-specific aggressive behaviour that seems to characterize different species of symbiotic polychaetes, particularly polynoids (e.g. Britayev et al., 2007).

Elytrae also seem the reason why Rullier (1964) described a small (i.e. juvenile) specimen of P. greeffi as a new species, Hololepidella fagei Rullier, 1964 . Being small, this specimen showed all elytra large, covering mid-dorsum, like those from anterior-most segments in larger worms. This species was synonymized with P. greeffi by Pettibone (1969) while describing Parahololepidella as a new genus.

Ecology. Parahololepidella greeffi was found at 0–30 m deep, living in association with colonies of the antipatharian Tanacetipathes cf. spinescens , while it was previously recorded as free living ( Augener, 1918; Pettibone, 1969; Rullier, 1964). In fact, Rullier (1964) reported specimens of H. greeffi occupying white mucous tubes, incrusted with sand grains and fragments of shells. According to Pettibone (1969), these tubes were perhaps formed by some commensal host. However, the supposed presence of tubes was not observed in our material, as the worms were always directly attached to the surface of the host antipatharian, without any trace of tubes. They were crawling on the main stems of the plumose branches of the coral (fig. 7), having very similar, cryptic colour (when preserved). All six colonies examined harboured polychaetes, two of them with several individuals on each colony (up to 6 in a 15x 10 cm branch, MNCN 16.01/13707).

As previously reported for all known symbiotic polychaetes ( Martin & Britayev, 1998), the finding of P. greeffi as symbiont reinforces the high diversity of the representatives of the family Polynoidae living in association with antipatharian hosts: of the 12 known species, eight are polynoids, three are species of Eunice , and the remaining one is a syllid ( Table 3).

Distribution. Tropical and Equatorial East Atlantic, Cabo Verde and São Tomé Archipelagos.

Figures

Figure 1.- Parahololepidella greeffi. MNCN 16.01/13708. (A, B) and MNCN 16.01/14341 (C, D). Adults in dorsal (A, C) and ventral (B, D) view.

Figure 2.- Parahololepidella greeffi. MNCN 16.01/13708. Juvenile. A. Entire view. A1 – A4. Detail of the anterior end (A1), mid-anterior region (A2), mid-posterior region (A3), and posterior end (A4). Scale bars are cm.

Figure 3.- Parahololepidella greeffi. MNCN 16.01/13708. Elytrae. Numbers represent the segment from which elytra were removed.

Figure 4.- Parahololepidella greeffi. MNCN 16.01/13708. Mid-body segment. A. Whole view of a transversal section, showing elytra and dorsal cirri on the same segment. B. Notopodium. C. Neuropodial acicular lobe. D. Neuropodial post-acicular lobe. E. Ventral cirri and nephridial papilla (black arrow). F. Neuropodial chaetae. G. Notopodial chaetae. Scale bars are cm (A) and mm (B-G).

Figure 5.- Parahololepidella greeffi. MNCN 16.01/13708. Right cirrigerous parapodium. A. From chaetiger 44, posterior view, chaetae omitted. B. From chaetiger 12, posterior view, with chaetae. Gorgoniapolynoe caeciliae. MNCN 16.01/14337. C. Left elytron of first pair; left margin folded on dorsal side. D. Detail of margin of same elytron. E. Notochaeta. F. Ventral-most neurochaeta. G. Dorsal-most neurochaeta. H. 35th parapodium. Scale bars are µm.

Figure 6.- Parahololepidella greeffi. Syntype ZMH 5692. A. Anterior end, dorsal view. B. Neurochaetae from anterior region, showing damaged tips. C. Notochaetae. D. Dissected parapodia from mid-body. E. Neurochaetae of the same (black arrow pointing at the apparently bidentate chaetae). F. Notochaetae of the same. B, C, E, F: scale bar 125 µm.

Figure 7.- Tanacetipathes cf. spinescens. MNCN16.01/13707. A.- Whole view of a host colony harbouring four specimens of Parahololepidella greeffi. B. Detail of a host curled on the main stem of the host black coral. White arrows point to the position of the symbionts.