Syllis profunda Cognetti, 1955

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 : 209-211

Syllis profunda Cognetti, 1955 stat. nov.

( Figure 7 )

Syllis variegata profunda Cognetti 1955: 3 , Fig. 2b ; Cognetti 1957: 20 ‒21, Fig. 4b . Syllis alternata Moore, 1908 sensu Çinar & Gambi 2005: 754 ‒755.

? Syllis alternata Moore, 1908 sensu Çinar & Ergen 2003 partim: 777‒778.

Material examined. Holotype: SZN-POL31: Grotta Azzurra, 100 m (04/09/1955). Additional material: St. 7: 3 individuals; St. 8: 2 individuals; St. 9: 1 individual.

Description. Holotype with regenerating anterior end, 11.3 mm long, 0.29 mm wide for 90 chaetigers. Prostomium (regenerated) oval, palps approximately 1.5x as long as prostomium; four reddish eyes in subtrapezoidal arrangement. Median antenna with 22 articles, lateral antennae with 15 articles. Dorsal cirri slender, moniliform, alternating in length, with 25–49 articles anteriorly, 20–40 articles at mid-body, and 28–30 articles posteriorly. Anterior parapodia with 6–8 compound chaetae, two distinctly longer, 2–4 of intermediate size and two short ( Fig. 7a ); mid-body parapodia with 5–6 compound chaetae, one long, 3–4 intermediate and one short ( Fig. 7c ); posterior parapodia with 5–6 compound chaetae, one longer, two intermediate, 2–3 short ( Fig. 7e ). Blades of compound chaetae 42 to 17 µm long, strongly bidentate, with subdistal tooth similar in size to distal one, and a coarse, moderately long ventral serration. Simple chaetae absent. Parapodia well-developed: anterior parapodia with 3 aciculae of similar thickness, central one slightly thicker and longer ( Fig. 7b ); midbody parapodia with 2 aciculae, larger acicula with tip progressively broad, smaller acicula pointed, straight ( Fig. 7d ); posterior parapodia with single, thick acicula, distally pointed ( Fig. 7f ), protruding out from parapodial lobes. Pharynx and proventricle impossible to notice in the regenerating individual.

Specimens from northern Tyrrhenian Sea ( Fig. 7g ) with very long, relatively wide pharynx, through nine chaetigers, with a small tooth close to opening; proventricle long, barrel-like, through 8 chaetigers, with ca. 35–40 muscle cell rows. Largest entire individual measuring ca. 20 mm long, 0,60 mm wide for 136 chaetigers, with up to 12 compound chaetae anteriorly, 10 at mid-body, and 8 posteriorly. Chaetae and aciculae as in holotype; anterior parapodia with three aciculae, simple chaetae always absent. Colour in living specimens pale brown to yellowish; yellowish when preserved.

Distribution. Mediterranean Sea, from the Gulf of Naples ( Cognetti 1955) to the Northern Tyrrhenian Sea (present data) and probably Levant Sea as S. alternata in Çinar & Ergen (2003) ; on hard and soft circalittoral bottoms (90–180 m, our data), including assemblages dominated by Leptometra phalangium and sponges. Other records of S. alternata in deep environments probably correspond to S. profunda .

Remarks. Syllis alternata was described by Moore (1908) from muddy bottoms between 15 and 350 m depth in the north Pacific Ocean and includes at least five cryptic Pacific species ( Carr et al., 2011). In the Mediterranean, this species has been reported mostly from shallow, hard bottoms, such as calcareous algae and coralligenous bottoms ( San Martín 2003); such clear differences in ecological requirements in respect to the original description suggest that these hard bottom records might possibly belong to a different, undescribed species. However, other Mediterranean records of S. alternata refer to circalitoral habitats, i.e. hard bottoms (100 m) of the Gulf of Naples ( Cognetti 1955—as S. variegata profunda ) and muddy bottoms (90 m) of the Eastern Mediterranean Sea (Çinar & Ergen 2003). It is worth noting that the type material of S. alternata from the Pacific Ocean, shows pseudo-spiniger compound chaetae ( Licher, 1999), which are neither present in the shallow-water, nor in the deep-water Mediterranean specimens. The examination of the holotype of S. variegata profunda Cognetti, 1955 showed that chaetal features are identical to the presently reported deep-water material, even if the dark pigmentation in peristomium reported by Cognetti (1955) is not visible anymore. This species was considered synonymous with S. alternata by Çinar and Gambi (2005); on the basis of the mentioned difference, we here consider S. variegata profunda a clearly different species, and in addition raise it to species rank as Syllis profunda Cognetti, 1955 . The shallow-water Mediterranean specimens of Syllis alternata sensu San Martín (2003) differ from the deep water ones in having up to seven aciculae in the anterior parapodia (three in S. profunda ), the blades of compound chaetae up to 60 µm (up to 45 µm in S. profunda ) and the presence of simple chaetae (absent in S. profunda ) ( San Martín 2003). We here consider them as separate taxa, even if molecular analyses may be useful to correctly assess this taxonomic issue.

Figures

FIGURE 2. Erinaceusyllis barbarae n. sp. Holotype (atoke) (MSNP:P/236/V):a) compound chaetae of chaetiger 5; b) compound chaetae of chaetiger 20; c) dorsal simple chaeta; d) acicula. Scale-bar:a-b:30 µm; c‒e:20 µm; f: 0.20 mm.

FIGURE 4. Exogone sophiae n. sp. Paratype (MSNP: P/001/SEM) a) Prostomium in dorsal view, showing the absence of antennae; b) anterior end in ventral view; c) anterior parapodia in ventral view; d) spiniger-like chaeta from chaetiger 2; e) falciger-like chaetae from chaetiger 2.

FIGURE7. Syllis profunda Cognetti, 1955.Holotype (SZN: SZN-POL31, Grotta Azzurra, 100 m):a) compound chaetae from the anteriorpart of thebody; b) aciculae from the anterior part of the body; c) compound chaetae from the midbody; d) aciculae from the midbody; e) compound chaetaefrom the posterior part of the body; f)acicula from the posterior part of thebody.Nontype individual (St.9, 180 m):g) anterior end in dorsal view.Scale-bar:a‒f: 30µm; g: 0.40 mm