Syllis, Lamarck, 1818

Langeneck, Joachim, Musco, Luigi, Busoni, Giulio, Conese, Ilaria, Aliani, Stefano & Castelli, Alberto, 2018, Syllidae (Annelida: Phyllodocida) from the deep Mediterranean Sea, with the description of three new species, Zootaxa 4369 (2), pp. 197-220 : 211-212

Syllis sp. 1

( Figure 8 )

Langerhansia caeca Katzmann 1973: 439 ‒442, Fig. 3 ; Arvanitidis 2000: 77. Typosyllis caeca Licher 1999: 64 ‒66, Fig. 29.

Syllis katzmanni Arvanitidis 1994: 98 ‒100.

Material examined: St. 3: 1 individual; St. 6: 1 individual; St. 11: 5 individuals; St. 12: 2 individuals.

Description. All individuals incomplete; best preserved individual 48 chaetigers for ca. 8 mm total length, 0.37 mm maximum width ( Fig. 8a ). Body thin, slender, elongate; prostomium ovate, distinctly wider than long, without eyes, palps elongate, distally rounded, longer than prostomium. Antennae, peristomial cirri and dorsal cirri moniliform, articulated, similar in shape, easily brokable; median antenna with more than 20 articles, lateral antennae with 10–15 articles, peristomial cirri and first dorsal cirri with up to 15 articles, then becoming shorter (7– 9).

Parapodia well-developed, with two aciculae of similar shape, pointed, subdistally slightly enlarged; in anterior parapodia both aciculae similar in size; in midbody parapodia one acicula distinctly larger than other; in posterior parapodia single acicula, with slightly enlarged subdistal region and rounded tip. Up to 10 compound chaetae with smooth, heterogomph shafts: 1–2 long spiniger-like chaetae, with extremely long blade (80–100 µm), unidentate, with almost smooth margin ( Fig. 8b ); 1–3 shorter spiniger-like chaetae, with shorter blades (40–50 µm), finely bidentate, with almost smooth ventral edge ( Fig. 8c ); and 4–5 falcigers, with shorter blade (35–17 µm), bidentate, with finely serrated edge and slightly rounded tip ( Fig. 8d ). Simple capillary chaetae apparently absent. Pharynx through 6 chaetigers, relatively broad, with small, pointed tooth; proventricle through 7 chaetigers, with 31–34 muscle cell rows.

Distribution. Adriatic Sea ( Katzmann 1973), Aegean Sea ( Arvanitidis 2000), Levant Sea (Çinar & Ergen 2003), Sicily Channel and Sea of Sardinia; from deep circalittoral (140 m depth) of the Adriatic Sea ( Katzmann 1973 Cantone & Di Pietro, 2002) to bathyal (500 and 1000 m depth with compact, clayish muds) bottoms ( Arvanitidis 2000; Çinar & Ergen 2003). Records of this species (as Syllis caeca / Langerhansia caeca ) from sciaphilous hard bottoms habitats at distinctly lower depths (10–45 m) ( Campoy 1982; Rubbiani 1986; Sardá 1991) most likely refer to a different species.

Remarks. The morphology of the examined individuals agrees with that of the type material of Langerhansia caeca Katzmann, 1973 redescribed by Licher (1999) as Typosyllis caeca , even if secondary teeth in falciger chaetae are often difficult to see at 400x magnification. The only remarkable difference is the less pronounced spinulation along the ventral edge of spiniger chaetae. This species was described as Langerhansia caeca by Katzmann (1973) for the central Adriatic Sea. Langerhansia Czerniavsky, 1881 is currently a synonymy of Syllis Lamarck, 1818 . However, the name is preoccupied by Syllis caeca Monro, 1933 . Hence, the species was renamed as Syllis katzmanni Katzmann, 1973 by Arvanitidis (1994). Later, Licher (1999), placed Langerhansia caeca in Typosyllis , thus resurrecting Typosyllis caeca (with T. katzmanni as synonymy). Since Licher’s use of Typosyllis is not widely accepted ( San Martín 2003), and the taxonomy of Syllis is currently unclear ( Aguado et al. 2012), Katzmann’s original name ( L. caeca ) in the current combination would be unavailable. However, according to ICZN rules (ICZN code, art. 8) Arvanitidis’ name ( S. katzmanni ) is not valid, as the dissertation where it was provided has not been published.

Our data confirm the bathymetric range, as well as the peculiar ecological requirements of this species, which appears to be the deepest Syllinae species occurring in the Mediterranean Sea.

Figures

FIGURE 3. Exogone sophiae n. sp. Paratype (MSNP: P/0242/V) a) anterior end indorsal view. Holotype (MSNP:P/3879): b) pygidium in dorsal view; c) spiniger-like chaeta from chaetiger 5; d) compound falciger chaetae from chaetiger 5; e) dorsal simple chaeta.Scale-bar: a‒b: 0.20 mm; c‒d‒e: 7 µm.

FIGURE 8. Syllis sp. 1 (St. 12, 900 m): a) anterior end in dorsal view; b) long spiniger-like chaeta from anterior chaetigers; c) short spiniger-like chaeta from anterior chaetigers; d) falcigers chaetae from anterior chaetigers. Scale-bar: a: 0.5 mm; b‒d: 20 µm.