Laonice mediterranea Sikorski, Nygren & Rousou, 2021

Sikorski, Andrey V., Radashevsky, Vasily I., Castelli, Alberto, Pavlova, Lyudmila V., Nygren, Arne, Malyar, Vasily V., Borisova, Polina B., Mikac, Barbara, Rousou, Maria, Martin, Daniel, Gil, João, Pacciardi, Lorenzo & Langeneck, Joachim, 2021, Revision of the Laonice bahusiensis complex (Annelida: Spionidae) with a description of three new species, Zootaxa 4996 (2), pp. 253-283 : 274-277

publication ID	https://doi.org/ 10.11646/zootaxa.4996.2.2
publication LSID	lsid:zoobank.org:pub:9FF4827B-A424-4D02-A58D-2CB37E1FAB5A
persistent identifier	https://treatment.plazi.org/id/F53026AC-57C6-422D-B3A2-8B77DEB7141E
taxon LSID	lsid:zoobank.org:act:F53026AC-57C6-422D-B3A2-8B77DEB7141E
treatment provided by	Plazi
scientific name	Laonice mediterranea Sikorski, Nygren & Rousou
status	sp. nov.

Treatment

Laonice mediterranea Sikorski, Nygren & Rousou View in CoL n. sp.

http://zoobank.org:act: F53026AC-57C6-422D-B3A2-8B77DEB7141E

( Figs 14B View FIGURE 14 , 15B–H View FIGURE 15 , 16 View FIGURE 16 , 17 View FIGURE 17 , 18D View FIGURE 18 , 19B View FIGURE 19 , Table 3)

Laonice bahusiensis: Dağli et al. 2011: 54–57 View in CoL , fig. 5. Çinar et al. 2012: 1462; 2014: 746. Çinar & Dağli 2013: 923. Not Söder- ström 1920.

Type locality. CYPRUS, off Cape Greco (Cavo Grekko), 34.9703°N, 34.0839°E, 31 m, shell fragments, fine sand GoogleMaps .

Type material. MOM INV-0022696 (holotype) , INV-0022697 , 0022700–0022705 (20 paratypes) ; MIMB 39040 View Materials (1 paratype) , 40463 (1 paratype), 40464 (1 paratype); MNCNM 16.01 /18567–18569 (14 paratypes) .

Adult morphology. Holotype largest complete specimen 38 mm long, 0.83 mm wide for 105 chaetigers. Pigmentation absent on body and palps.

Prostomium triangular, anteriorly wide, broadly rounded, occasionally truncate to slightly concave, fused with fronto-lateral margin of peristomium ( Figs 15C, G View FIGURE 15 , 16A View FIGURE 16 ), posteriorly extending over 33 chaetigers (to end of chaetiger 30 in holotype) as a well-developed narrow caruncle, shorter in smaller individuals ( Fig. 17A View FIGURE 17 ). Nuchal organs U-shaped ciliary bands on sides of caruncle ( Figs 15C, D View FIGURE 15 , 16A View FIGURE 16 ). Length of nuchal organs was strongly correlated with individual number of branchiate chaetigers ( Fig. 17C, r View FIGURE 17 2 View FIGURE 2 = 0.8124, n = 20). Occipital antenna usually short ( Figs 15C, G View FIGURE 15 , 16B View FIGURE 16 ), occasionally comparatively long ( Fig. 16A View FIGURE 16 ). Two pairs of red eyes (appearing almost black in formalin-fixed specimens) usually present, comprising one pair of very large median eyes and one pair of small lateral eyes situated anteriorly and either in front of median eyes ( Fig. 16A View FIGURE 16 ) or set wider apart, occasionally between prostomium and peristomium and therefore not visible in dorsal view ( Fig. 15C, G View FIGURE 15 ). Median eyes often occupying entire posterior part of prostomium in front of occipital antenna ( Figs 15C View FIGURE 15 , 16A View FIGURE 16 ). Lateral eyes situated well apart from median eyes ( Fig. 16A View FIGURE 16 ). Only in holotype median eyes appearing as two narrow oblique dark stripes surrounded by residual pigment similar in size and shape to big eyes in other specimens, suggesting that original big eyes faded. Palps missing in all specimens examined.

Chaetiger 1 with well-developed capillary chaetae and small postchaetal lamellae in both rami; notopodial lamellae ear-shaped; neuropodial lamellae rounded.All notopodia with capillary chaetae only. Notopodial postchaetal lamellae on branchiate chaetigers usually ear-shaped, each with an acute peak on the upper tip ( Fig. 15E View FIGURE 15 ). Lamellae from chaetigers 5–6 to chaetigers 8–9 usually with peaks shifted onto lateral margin or not developed at all ( Fig. 15F View FIGURE 15 ). Notopodial postchaetal lamellae largest on chaetiger 4, in branchiate region not overlapping over dorsum but projecting considerably above it, in postbranchiate region becoming rounded and smaller, but slightly increasing in size again on 10–15 posterior-most chaetigers. On several posterior branchiate and on anterior postbranchiate chaetigers, acute upper tips of notopodial postchaetal lamellae curving down and outwards, lower parts of lamellae greatly extending below. Neuropodial postchaetal lamellae of about seven anterior chaetigers occasionally with small pointed tip on lateral margin; on posterior chaetigers, tips shifting to lower part of lamellae. On postbranchiate chaetigers, neuropodial postchaetal lamellae gradually diminishing in size, becoming rounded and shifting to a position lower than hooks, but slightly increasing in size again on 10–15 posterior most chaetigers, as with notopodial lamellae.

Branchiae from chaetiger 2, up to 32 pairs (on chaetigers 2–30 in holotype); first pair shorter than or approximately as long as notopodial postchaetal lamellae of chaetiger 2; branchiae on succeeding chaetigers up to twice as long as notopodial lamellae ( Fig. 15C View FIGURE 15 ), reduced in length on posterior chaetigers. Individual number of branchiae was strongly correlated with length of nuchal organs ( Fig. 17C View FIGURE 17 ).

Dorsal transverse crests one per chaetiger, beginning on posterior caruncle-bearing chaetigers (usually three chaetigers before last branchiate chaetiger) and arranged on up to 13 following chaetigers. On caruncle-bearing chaetigers, dorsal crests interrupted by caruncle, while on succeeding chaetigers they are complete ( Fig. 15D View FIGURE 15 ).

Lateral interneuropodial pouches from chaetigers 7–27 (from chaetiger 15 in holotype) to end of body. Anterior start of pouches was strongly correlated with individual number of branchiate chaetigers ( Fig. 18D, r View FIGURE 18 2 View FIGURE 2 = 0.7681, n = 20).

Sabre chaetae in neuropodia from chaetigers 11–16 (from chaetiger 15 in holotype), from more anterior chaetigers in small individuals ( Fig. 17B View FIGURE 17 ), 1–2 in a tuft; chaetae with weak granulation on shaft, up to twice as long as hooks. Anterior start of sabre chaetae was moderately correlated with individual number of branchiate chaetigers ( Fig. 17D, r View FIGURE 17 2 View FIGURE 2 = 0.4822, n = 20).

Hooded hooks in neuropodia from chaetigers 18–33 (from chaetiger 28 in holotype), from more anterior chaetigers in small individuals ( Fig. 17B View FIGURE 17 ), up to nine in a series, accompanied by inferior sabre chaetae and alternating capillaries throughout body. Hooks quadridentate, with one pair of upper teeth and single superior median tooth above main fang ( Fig. 16C View FIGURE 16 ), or quinquedentate, with one pair of superior teeth instead of single superior tooth; shaft slightly curved. Anterior start of hooks was strongly correlated with individual number of branchiate chaetigers ( Fig. 17D, r View FIGURE 17 2 View FIGURE 2 = 0.7014, n = 20).

Pygidium with up to four pairs of long dorsal cirri (holotype) and one pair of short ventral cirri.

Digestive tract without gizzard-like structure.

Methylene green staining. Intensely stained frontal and posterior surfaces of upper parts of notopodial postchaetal lamellae from chaetiger 5 to chaetigers 10–11 ( Fig. 15G View FIGURE 15 ). Weakly stained edges of neuropodial postchaetal lamellae from chaetiger 2 to about chaetiger 25. Characteristic diffused staining on ventral body surface, most intensive from chaetiger 16 to about chaetiger 26 ( Fig. 15 H View FIGURE 15 ). No staining on prostomium.

Remarks. The specimens herein referred to L. mediterranea n. sp. had earlier been identified as L. bahusiensis ( Dağli et al. 2011; Çinar et al. 2012, 2014; Çinar & Dağli 2013). However, in L. bahusiensis nuchal organs terminate 0–10 chaetigers before the last branchiate chaetiger ( Fig. 19A View FIGURE 19 ), and dorsal transverse crests first appear on a chaetiger after the end of nuchal organs, whereas in L. mediterranea n. sp. nuchal organs usually extend beyond the last branchiate chaetiger ( Figs 15D View FIGURE 15 , 19B View FIGURE 19 ), and dorsal transverse crests first appear 1–4 chaetigers before the end of nuchal organs ( Fig. 15D View FIGURE 15 ).

left sides, frontal view: E, chaetiger 4; F, chaetiger 6. G, H, methylene green staining: anterior end, dorsal view (G), and chaetigers 13–27, ventral view (H). A— ZMBN 135383 View Materials ; B–D— MOM INV-0022701 (paratype); E, F— MNCNM 16.01 /18569; G,

H— MOM INV-0022700 (paratype). Scale bars: A, B not to scale; C–F = 200 µm; G, H = 300 µm .

Laonice mediterranea n. sp. appears most similar to L. irinae n. sp. (see above) from North European waters, but can be distinguished from the latter by the size of the median eyes and the shape of notopodial postchaetal lamellae on anterior chaetigers. In L. irinae n. sp. the ratio of length of the prostomium in front of median eyes (l 1) to the length of median eyes (l 2) is always more than 2.5, and the acute peaks on upper tips of notopodial postchaetal lamellae are strictly terminal on the ten anterior chaetigers, whereas in L. mediterranea n. sp. the ratio of the length of the prostomium in front of the median eyes (l 1) to the length of the median eyes (l 2) is less than 2.3. Acute peaks on the upper tips of notopodial postchaetal lamellae, if present, in L. mediterranea are shifted onto the lateral margin from chaetigers 5–6 to chaetigers 8–9, unlike lamellae on at least ten anterior chaetigers with terminal acute peaks on upper tips in L. irinae .

In the Mediterranean Sea, L. mediterranea n. sp. co-occurs with L. grimaldii n. sp. ( Fig. 14 View FIGURE 14 ). The adults look similar but can be distinguished by the Br-NO values, which vary from -4 to 1 in the former and from 2 to 12 in the latter species ( Fig. 19B View FIGURE 19 ). Moreover, the adults of L. mediterranea n. sp. have very large median eyes usually occupying the entire posterior part of the prostomium until the occipital antenna ( Fig. 15C View FIGURE 15 ), whereas in the adults of L. grimaldii n. sp. median eyes appear as transverse bars or oblong oval spots ( Fig. 10A View FIGURE 10 ).