Laonice (Appelloefia) barcinensis Sikorski, 2021

Sikorski, Andrey V., Pavlova, Lyudmila V., Sardá, Rafael, Langeneck, Joachim, Gil, João & Ravara, Ascensão, 2021, Two new deep-sea species of Laonice (Annelida: Spionidae) from the Mediterranean Sea, Zootaxa 4908 (4), pp. 515-526 : 519-521

Laonice (Appelloefia) barcinensis Sikorski sp. nov.

( Figures 3 A–K, 4)

LSID: urn:lsid:zoobank.org:act:EC9FFD05-5EDF-46F7-A2C5-00874FCEC69C

Laonice bahusiensis — Sardá et al., 2009: 4, table 2. Material examined. Holotype ( MNCN 16.01 /18548): Foix submarine canyon, SW Barcelona, NW Mediterranean Sea , Projects EC-EUROMARGE-NB / CICYT-CONCENTRA, St. 05C21, 41.0333ºN 01.9333ºE, sediment trap moored 30 m above a sea ground 990 m deep, 04.1993–04.1994.

Three paratypes from Foix submarine canyon, SW Barcelona, NW Mediterranean Sea, Projects EC-EURO-MARGE-NB / CICYT-CONCENTRA: St. 01C22, 40.9833ºN 02.0333ºE, sediment trap moored 30 m above a sea bed 1195 m deep, 04.1993–04.1994 ( MNCN 16.01 /18676); St. 01C24 and St. 02C24, 41.0333ºN 01.9333ºE, sediment trap moored 500 m above a sea bed 990 m deep, 04.1993–04.1994 ( MNCN 16.01 /18677 and MNCN 16.01 /18617) .

Description. Holotype complete, 126 chaetigers, 32 mm long, and 1.2 mm wide at about chaetiger 10. One paratype (MNCN 16.01/18676) complete—99 chaetigers, two other paratypes fragmented, however with pygidial fragments. Worms up to 61 mm long for 142 chaetigers, and 1.6 mm wide at chaetigers 7–12.

Prostomium longer than wide, from almost triangular, slightly T-shaped ( Fig. 3A ) to almost quadrangular, with anterior margin truncated or slightly rounded with slight concavity, and completely separated from the peristomium at the anterior edges. Eyespots nearly invisible, smaller individuals may show one pair of faint (probably deeply embedded) eye-strips close to the base of the occipital antenna. Occipital antenna long and very thin (as long as or longer than notopodial postchaetal lamellae of chaetiger 1), ending in a thread-like tip, usually vertically erect, sometimes with middle bulbous enlargement, and inserted at the end of the prostomium. Intact palps lost from all specimens (one very short, torn off palp present in the sample MNCN 16.01/18617). Nuchal organs as long double U-shaped ciliary bands extending posteriorly to chaetigers 9–11 ( Fig. 3A ). Anterior region of body (i.e. anterior segments bearing the nuchal organs plus the following one to approximately 10 anterior chaetigers) approximately 1.5 times wider than subsequent segments.

Branchiae from chaetiger 2, present nearly along the entire body, although absent in the 18–19 posterior-most chaetigers. Branchiae free, one third shorter than notopodial postchaetal lamellae until chaetiger 4, then gradually increasing in length and reaching about the same length as the notopodial postchaetal lamellae at chaetiger 7–9 ( Fig. 3A,C ), and becoming 1.2–1.3 times longer than notopodial postchaetal lamellae on subsequent segments ( Fig. 3B , D–F), except in the very posterior ones, where they become about one third shorter ( Fig. 3G ). Branchiae from the mid-body ending in a threadlike process ( Fig. 3F ), posterior-most branchiae thin, subulate ( Fig. 3G ).

Notopodial prechaetal lamellae visible from chaetiger 3 to 12–22, attaining maximum size on chaetigers 9–10 (approx. 0.4 the length of notopodial postchaetal lamellae). Longest notopodial postchaetal lamellae at chaetigers 7–25. Notopodial postchaetal lamellae of the first 4–7 chaetigers leaf-like with elongated pointed tips ( Fig. 3C ), more obtuse afterwards, with broadly rounded upper margins on chaetigers posterior to nuchal organs ( Fig. 3 D–E), lacking an upwardly extension after chaetiger 45 ( Fig. 3F ), becoming lanceolate at chaetiger 85 ( Fig. 3G ) and finally disappearing 4 segments before pygidium.

Neuropodial prechaetal lamellae visible from chaetiger 2 to 12–13, reaching maximum size in chaetigers 7–9. Neuropodial postchaetal lamellae reaching their maximum size on chaetigers 8–17 ( Fig. 3C ), then gradually diminishing further back, becoming very short on the posterior 40–45 chaetigers ( Fig. 3G ). Neuropodial postchaetal lamellae bearing acute upwardly turned tips on the first 7 chaetigers ( Fig. 3C ), with a peak gradually shifting along the margin of the lamella afterwards and becoming less evident ( Figs. 3 D–E); neuropodial postchaetal lamellae with acute tips in the posterior half of body again ( Fig. 3 F–G).

Transverse dorsal crests connecting bases of notopodial postchaetal lamellae ( Fig. 3B ) from chaetiger 12–15 to chaetiger 50–74. Transverse dorsal crests generally low, attaining maximum height between chaetigers 15–47.

Inter-parapodial pouches from chaetigers 5–8 to nearly the end of the body, ending 5–7 chaetigers before pygidium. The inter-parapodial pouches may start from unpaired segments on opposite sides of the same specimen (difference of up to 2 segments).

Anterior parapodia with notopodial capillary chaetae arranged in more than 2 vertical rows in chaetigers 1–15 (with up to 6 rows in chaetigers 8–10), in 2 vertical rows from chaetiger 16; and neuropodial capillaries arranged in more than 2 vertical rows in the 12 anterior most chaetigers ( Fig. 3C ), in 2 rows only on more posterior chaetigers. Neuropodial hooded hooks appearing from chaetiger 19–22, numbering 9–11 per bundle, and bearing 3 apical teeth above the main fang ( Fig. 3 H–I, K). Sabre chaetae appearing from chaetiger 11–12, numbering at first 3–4 per bundle, and then 1–2 from chaetiger 16.

Pygidium with a pair of short ventral lobes and two pairs of thin and long, threadlike lateral anal cirri ( Fig. 3J ).

No specific pigmentation observed.

Staining in Methyl Green. Anterior margin of prostomium and peristomium, occipital antenna, margins of postchaetal lamellae and small oval lateral spots between notopodia and neuropodia visibly staining more intensely than adjacent parts of body.

Etymology. The name barcinensis is derived from Barcino, ancient Latin name of Barcelona, and is given to this species in honor of the city of Barcelona, located close to the type locality of the new species.

Distribution. Mediterranean Sea ( Fig. 4 ): Foix submarine canyon (off NE Spain), in sediment traps moored 30 m above a seabed 990–1195 m deep, and 500 m above a seabed 990 m deep.

Remarks. Laonice (Appelloefia) barcinensis sp. nov. is morphologically very similar to L. (A.) appelloefi Ŝderstr̂m, 1920 and L. (A.) maciolekae Aguirrezabalaga & Ceberio, 2005 (synonymized with L. appelloefi in Meissner et al., 2014 ). However, branchiae and inter-parapodial pouches were only observed in L. appelloefi on a limited number of segments, whereas in the new species these structures are present through almost the entire length of the body, with the exception of the last posterior-most segments. These two characters suggest that the new species is similar to Laonice (Norgensia) norgensis Sikorski, 2003 , but this species has much longer nuchal organs, reaching chaetiger 15–29, and the inter-parapodial pouches appear from chaetiger 8–17 (against chaetiger 5–8 in L. barcinensis sp. nov.).

It is remarkable to notice how large adult worms of several dozens of milligrams of wet weight ( Sardá et al. 2009), belonging to a typically benthic genus, seem able to reach sediment traps moored as high as 500 m above the seabed. Sardá et al. (2009) hypothesized that the existence of a highly turbulent environment associated with the transport of large amounts of water and sediment inside the Mediterranean submarine canyons ( Canals et al. 2006), along with their strong bottom currents and resuspension events, would be responsible for the mobilization of sediment and benthic and epibenthic species into the water column. Such resuspension could even transport the specimens, up to hundreds of meters above the seabed where they normally live, reaching this way the sediment traps where they were found.

Figures

FIGURE 3. Laonice (Appelloefia) barcinensis sp. nov. A. Anterior end, dorsal view. B. Midbody chaetigers 37–40, dorso-lateral view, showing transverse dorsal crests. C–G. Right parapodium, anterior view: C, chaetiger 7; D, chaetiger 18; E, chaetiger 30; F, chaetiger 57; G, chaetiger 111. H. Neuropodial hooded hook of chaetiger 52, side view. I. Neuropodial hooded hook of chaetiger 52, frontal view. J. Pygidium, dorsal view. K. Neuropodial hooded hook from posterior segment, SEM photo. Material: A–I—paratype MNCN 16.01/18617; J—paratype MNCN 16.01/18677; K—paratype MNCN 16.01/18676. Scales (mm): A–B = 1.0; C–G = 0.5; H–I = 0.005; J = 0.4.

FIGURE 4. Distributional map of the Mediterranean deep-sea Laonice species: circles, Laonice (Sarsiana) alberti sp. nov.; triangles, Laonice (Appelloefia) barcinensis sp. nov.; star, Laonice (Laonice) sp.; T, type localities.