Synelmis mezianei, Salazar-Vallejo & León-González, 2025

Salazar-Vallejo, Sergio I. & León-González, J. Angel De, 2025, Additional new species of marine annelids from Clipperton Island (Nereididae: Pilargidae: Sabellariidae), European Journal of Taxonomy 1026, pp. 1-29 : 11-14

Synelmis mezianei sp. nov.

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Fig. 2

Diagnosis

Synelmis with lateral antennae inserted basally to palps; notospines from chaetiger 5; median chaetigers with dorsal cirri basally swollen, tapered, ventral cirri twice as long as wide.

Etymology

The species is named after Dr Tarik Meziane, curator of the Annelida collection of the Muséum national d’Histoire naturelle, Paris, in recognition of his long-term support of our research activities. The specific epithet is a noun in the genitive case (ICZN 1999, Art. 31.1.2).

Type material

Holotype

FRANCE • complete spec.; Clipperton Island , stn 10; 10°17.31′ N, 109°12.19′ W; depth 13 m; 17 Jan. 2005; J.-M. Bouchard, L. Albenga and L. Dugrais leg.; coral rubble, suction pump; MNHN IA-2000- 2108 .

Paratype

FRANCE • 1 complete spec.; same data as for holotype, colorless anterior fragment, 10 mm long, 0.5 mm wide, 42 chaetigers; ECOSUR 319 .

Other material examined

FRANCE • 2 median fragm.; same data as for holotype, fragments 9.5–12.5 mm long, 0.5–0.6 mm wide, 31–45 chaetigers, pale, almost breaking off in some portions; MNHN IA-2001-157 .

Description

BODY. Holotype ( MNHN IA-2000-2108 ), anterior fragment, colorless, subcylindrical, tapered anteriorly; in cross section, dorsum elevated, parapodia on lateral depressions, venter with longitudinal groove; 19 mm long, 0.5 mm wide, 74 chaetigers.

PROSTOMIUM. Trapezoidal, slightly wider posteriorly ( Fig. 2A). Palps biarticulate, separated from each other, separation visible dorsally and ventrally, palpostyles hemispherical, ventral papillae tapered, surpassing palpostyles tips. Antennae all cirriform, lateral antennae inserted anteriorly, close to palp bases, surpassing palpostyle tips; median antenna inserted on posterior prostomial margin, ½ × as long as prostomial length. Eyes blackish, semilunar, positioned slightly ahead of lateral antenna.

TENTACULAR BELT. Tentacular cirri cirriform, directed anteriorly, ventral cirri slightly longer than dorsal ones.

PARAPODIA. Sesquiramous throughout fragment. First dorsal cirri longer than following ones. Parapodial cirri thinner, not basally swollen along chaetigers 1–9. Dorsal and ventral cirri basally swollen, with long tapered tips, glandular in median ( Fig. 2B–C), and posterior segments ( Fig. 2D–E). Neurochaetal lobe truncate, sometimes not visible by obstruction of body wall. Notopodia of chaetigers 1–4 without notospines, following one with notospines, progressively longer and more exposed posteriorly, tips usually broken.

CHAETAE. Furcate chaetae not seen, probably broken. Neurochaetae simple, smooth or finely spinulose capillaries, about 14 per bundle by chaetiger 40, with 1–2 larger than others, decreasing to about 10 per bundle by chaetiger 70.

POSTERIOR END. Unknown.

Variation

The paratype (ECOSUR 319) shows a similar morphology. The lateral antennae surpass palpostyles tips; ventral palp papillae tapered, surpassing palpostyles tips; eyes are semilunar; median antenna half as long as prostomium; tentacular cirri wider basally, tapered, ventral ones slightly longer than dorsal ones; parapodial cirri similar, progressively wider basally from chaetiger 8–9; notospines from chaetiger 5; furcates not seen, probably broken.

Distribution

Only known from subtidal rocky bottoms in Clipperton Island, Eastern Pacific.

Remarks

Synelmis mezianei sp. nov. resembles S. kirkegaardi Salazar-Vallejo, 2003 from Cape Verde Islands, Eastern Atlantic, because both species have lateral antennae inserted anteriorly, notospines from chaetiger 5, and parapodial cirri basally swollen. However, they differ because in S. mezianei median segments have parapodial cirri tapered and ventral cirri are 2 × as long as wide, whereas in S. kirkegaardi parapodial cirri are fusiform mucronate, about as long as wide.

Key to the species of Synelmis Chamberlin, 1919

(modified after Salazar-Vallejo 2003; most references therein)

1. Prostomium with lateral antennae positioned anteriorly, close to base of palpostyles ..................... 2 – Prostomium with lateral antennae positioned medially .................................................................... 7

2. Notospines from chaetigers 5–6 ....................................................................................................... 3

– Notospines from chaetiger 9; with four eyes; median chaetigers with cirri basally swollen ............. ........................................................................................................ S. gracilis ( Hessle, 1924) ( Japan)

3. Median chaetigers with thin cirri, sometimes basally expanded ...................................................... 4 – Median chaetigers with thicker cirri, expanded basally ................................................................... 6

4. Prostomium with two eyes ................................................................................................................ 5 – Prostomium with two rows of lateral eyes, each with 4–5 ocelli; chaetiger 1 with dorsal cirrus as long as following ones .................................................................... S. knoxi Glasby, 2003 ( New Zealand)

5. Anterior segments without pigmented lateral glands; median antenna short, about ½× as long as prostomial length; chaetiger 1 with dorsal cirri longer than following ones ...................................... ...................................................................................... S. amoureuxi Salazar-Vallejo, 2003 ( Brazil)

– Anterior segments with abundant, dark lateral glands; median antenna long, ¾ × as long as prostomial; chaetiger 1 with dorsal cirri longer than following ones ................................................. ............................................................ S. gibbsi Salazar-Vallejo, 2003 (Red Sea to Marshall Islands)

6. Median segments with parapodial cirri fusiform mucronate, ventral cirri as long as wide ................ ..................................................................... S. kirkegaardi Salazar-Vallejo, 2003 (Eastern Atlantic)

– Median segments with parapodial cirri tapered, ventral cirri 2 × as long as wide ............................. .............................................................................................. S. mezianei sp. nov. ( Clipperton Island)

7. Prostomium with eyes ....................................................................................................................... 8 – Prostomium without eyes ............................................................................................................... 15

8. Only one pair of lateral eyes ............................................................................................................. 9 – Eyes multiple, 2–4 in each lateral row (sometimes laterally fused) ............................................... 13

9. Median segments with parapodial cirri fusiform; median antenna short, not reaching chaetiger 1 ... ......................................................................................................................................................... 10 – Median segments with parapodial cirri digitate to basally swollen, not fusiform .......................... 12

10. All antennae fusiform ......................................................................................................................11 – All antennae cirriform; notospines from chaetigers 10–11; without lateral glands behind chaetal lobes ......................................................................... S. albini ( Langerhans, 1881) (Eastern Atlantic)

11. Notospines from chaetiger 8; dorsal cirri as long as wide .................................................................. ............................................................................................ S. cf albini Wolf, 1984 (Gulf of Mexico)

– Notospines from chaetigers 10–16; dorsal cirri 2 × as long as wide .................................................. ............................................. S. harrisae Salazar-Vallejo, 2003 (California to northwestern Mexico)

12. Median antenna short, not reaching chaetiger 1; eyes dorsal; notospines from chaetiger 13–18 ....... ................................................................. S. britayevi Salazar-Vallejo, 2003 ( Mozambique Channel) – Median antennae long, reaching chaetiger 1; eyes lateral; notospines from chaetigers 7–14; eyes lateral or absent ...................................... S. emiliae Salazar-Vallejo, 2003 (partim) (Eastern Pacific)

13. With two eyes per side, fused to each other .................................................................................... 14 – With four eyes per side; median and posterior chaetigers with dorsal and ventral cirri basally swollen to digitate; notospines from chaetigers 17–22 .................................................................................... ............................................................................... S. sotoi Salazar-Vallejo, 2003 (Grand Caribbean)

14. Median and posterior chaetigers with dorsal and ventral cirri digitate, similar in length and width; notospines from chaetigers 15–23 ...................... S. rigida ( Fauvel, 1919) ( India to Western Pacific) – Median chaetigers with dorsal and ventral cirri fusiform; notospines from chaetigers 9–11 ............. .................................................................................. S. gorgonensis ( Monro, 1933a) Eastern Pacific

15. Notospines from chaetiger 5; median segments with parapodial cirri of similar length; median antenna short, not reaching chaetiger 1 .............................................................................................. ............................................................. S. levinae Salazar-Vallejo, 2003 (Eastern Pacific seamounts) – Notospines from chaetigers 8–20; median segments with ventral cirri longer than dorsal ones .... 16

16. Median antenna long, reaching chaetiger 1 .................................................................................... 17 – Median antenna short, not reaching chaetiger 1 ............................................................................. 18

17. Median segments with ventral cirri 2 × as long as wide; notospines from chaetigers 13–15 ............ ................................................................ S. emiliae Salazar-Vallejo, 2003 (partim) (Eastern Pacific)

– Median segments with ventral cirri 4 × as long as wide; notospines from chaetigers 9–20 .............. ......................................................................................... S. sergi Glasby & Marks, 2013 ( Australia)

18. Median segments with parapodial cirri tapered .............................................................................. 19 – Median segments with parapodial cirri swollen medially, mucronate; notospines from chaetiger 12 ................................................................... S. glasbyi Salazar-Vallejo, 2003 ( Mozambique Channel)

19. Notospines from chaetiger 8–10; all antennae of similar size ............................................................ .............................................................................. S. urogorri Moreira & Parapar, 2007 (NW Spain)

– Notospines from chaetigers 12–15; median antenna slightly longer than laterals ............................. .................................................................................. S. sinica Sun & Chen, 1990 (South China Sea)