Laonice grimaldii Sikorski, Nygren & Mikac 2021, n. sp.

Laonice grimaldii Sikorski, Nygren & Mikac n. sp.

http://zoobank.org:act: D21FC5F2-B9E2-4840-B75F-2D24EBBC2F45

(Figs 10, 11, 12A–C, 13, 14A, 18C, 19B, Table 3)

Aonides cirrata: Fauvel, 1909 (Part.): 4–5. Not M. Sars 1851.

Laonice cirrata: Fauvel, 1927 (Part.): 37–38, fig. 12a–e. Not M. Sars 1851.

Type locality. ITALY, Ligurian Sea, st. GAS 10 ter., 43.6368°N, 10.0983°E, 70–80 m, muddy sand.

Type material. MOM INV-0022706 (holotype), INV-0022681–0022693, 0022698, 0022699 (35 paratypes); HUJI NVPOLY-2950 (4 paratypes); MIMB 39037–39039, 39047 (23 paratypes); MNCNM 16.01 /18549–18566 (144 paratypes).

Adult morphology. Holotype largest complete specimen 40 mm long, 0.8 mm wide for 109 chaetigers. Smallest complete paratype 13 mm long, 0.26 mm wide for 61 chaetigers. Pigmentation absent on body and palps. Gatherings of glandular cells on branchiae and postchaetal lamellae appearing dark in some formalin-fixed specimens.

Prostomium triangular, anteriorly wide, truncate or broadly rounded, fused with anterior margin of peristomium (Figs 10A, B, F, 12A), extending posteriorly to chaetiger 37 (to end of chaetiger 33 in holotype) as a low caruncle (Figs 10A, 12A), shorter in small individuals (Fig. 13A). Posterior end of caruncle flat and often indistinct (Fig. 12B). Nuchal organs U-shaped ciliary bands on sides of caruncle (Fig. 10A). Length of nuchal organs was strongly correlated with individual number of branchiate chaetigers (Fig. 13C, r 2 = 0.8927, n = 30). Occipital antenna present, usually small (Fig. 10A, B, F, 12A). One pair of medium-sized median eyes as transverse short wide bands or oblong oval spots oriented obliquely (Figs 10A, F, 12A). Palps as long as 10–14 chaetigers, with deep frontal longitudinal groove lined with cilia.

Chaetiger 1 with short capillaries and moderate sized postchaetal lamellae in both rami. Capillaries in each anterior parapodium arranged in two vertical rows. All notopodia with capillary chaetae only. Notopodial postchaetal lamellae with pointed upper tips usually on 3–4 anterior chaetigers (Fig. 10A), occasionally on 5–9 anterior chaetigers (Fig. 11A–D), with rounded to truncate upper edge on succeeding chaetigers (Fig. 11E, F). Notopodial postchaetal lamellae of chaetiger 3 slightly larger than those of chaetiger 4. Notopodial lamellae and branchiae on anterior chaetigers usually overlapping middorsally, thus obscuring observation of nuchal organs. Notopodial postchaetal lamellae on last branchiate chaetiger and on about seven succeeding postbranchial chaetigers with lower part expanded ventrally (Fig. 11G). Neuropodial postchaetal lamellae until chaetiger 4 with upper part acute (Fig. 11A, B), on succeeding chaetigers with rounded edges (Fig. 11C–G).

Branchiae from chaetiger 2 to chaetigers 12–45 (on chaetigers 2–38 in holotype), fewer in smaller individuals (Fig. 13A). Branchiae short on anterior chaetigers, full-sized and slightly longer than notopodial postchaetal lamellae from chaetigers 4–5 onwards (Fig. 11B–F). Individual number of branchiae was strongly correlated with length of nuchal organs (Fig. 13C).

Dorsal transverse crests absent on chaetigers with nuchal organs (Fig. 12B). Two dorsal crests usually present on each of 2–3 last branchiate chaetigers (Fig. 10D). Anterior crest on each of those chaetigers appearing as an extension of posterior sides of lateral interneuropodial pouches onto dorsum (Fig. 10C, D), becoming prominent from chaetiger 16 (Fig. 10C) and forming complete dorsal crests on 3–4 last branchiate chaetigers (Fig. 10D). Posterior crests appearing 1–2 chaetigers after first start of anterior crests and interconnecting notopodial postchaetal lamellae (Fig. 10D). Anterior and posterior crests almost equal in maximum height on 2–3 last branchiate chaetigers. Anterior crests reduced in height on succeeding chaetigers and disappearing completely after 2–6 postbranchiate chaetigers. Posterior crests on approximately 20 postbranchiate chaetigers (until chaetiger 57 in holotype) becoming nearly as high as notopodial postchaetal lamellae.

Lateral interneuropodial pouches from chaetigers 7–26 (from chaetiger 14 in holotype) to body end. Anterior start of pouches was moderately correlated with individual number of branchiate chaetigers (Fig. 18C, r 2 = 0.5278, n = 29).

Sabre chaetae in neuropodia from chaetigers 8–18 (from chaetiger 15 in holotype), from more anterior chaetigers in smaller individuals (Fig. 13B), 1–2 in a tuft below vertical row of capillaries or hooded hooks (Fig. 11F, G). Anterior start of sabre chaetae was weakly correlated with individual number of branchiate chaetigers (Fig. 13D, r 2 = 0.2854, n = 30).

Hooded hooks in neuropodia from chaetigers 13–36 (from chaetiger 34 in holotype), from more anterior chaetigers in smaller individuals (Fig. 13B), up to 13 in a series (Fig. 11G). Hooks tri- or quinquedentate, with one or two pairs of small apical teeth above main fang (Figs 11H, 12C); superior pair of teeth tiny and hardly discernible, not developed in some hooks. Anterior start of hooks was strongly correlated with individual number of branchiate chaetigers (Fig. 13D, r 2 = 0.9189, n = 31).

Pygidium with one pair of short ventral cirri and up to four pairs of longer and thinner thread-like dorsal cirri with swollen bases (Fig. 10E).

Digestive tract without gizzard-like structure.

Methylene green staining. Intensely stained narrow band along frontal edge of prostomium and peristomium (Fig. 10F); usually stained as well the posterior surfaces, lateral margins and sometimes frontal surfaces of distal parts of notopodial postchaetal lamellae from chaetiger 4 to chaetiger 9 (rarely up to chaetiger 19), and basal parts of pygidial cirri (Fig. 10F). Characteristic diffused staining on ventral body surface, most intensely from approximately chaetiger 21 to chaetigers 33–35 (Fig. 10G).

Remarks. Adult L. grimaldii n. sp. appear similar to L. bahusiensis in having the prostomium fused with the frontal margin of the peristomium, dorsal crests only on postbranchiate chaetigers and a narrow band along the frontal edge of prostomium stained with Methylene Green. They differ from all other species of Laonice in having double dorsal crests on chaetigers near the last branchiate chaetiger. Within the L. bahusiensis complex, L. grimaldii n. sp. differs from the other species in having rounded instead of acute notopodial postchaetal lamellae after chaetigers 4–9, and branchiae being slightly longer instead of considerably longer (from 1.3 to 2 times longer) than notopodial postchaetal lamellae. Moreover, the adults of L. grimaldii n. sp. characteristically have a caruncle flattened and therefore indistinct on its posterior end (Fig. 12B), contrary to adults of most other species, which have distinct caruncles that terminate clearly and abruptly.

The adults of L. grimaldii n. sp. are similar to those of L. antipoda Sikorski, 2011 from South Africa in various numeric characteristics, especially in the presence of branchiae and prominent dorsal crests on several chaetigers posterior to nuchal organs. In the original description of L. antipoda, Sikorski (2011) noticed the absence of an occipital antenna in the specimens examined but assumed that it might be due to damage. Recent examinations of additional material of L. antipoda from Angola and Gabon (Sikorski, unpublished), however, confirmed the lack of an occipital antenna in this species (Fig. 12D). Thus, L. grimaldii n. sp. differs from L. antipoda by having smaller adults (maximum body width ≤ 0.8 mm in L. grimaldii n. sp. versus ≥ 1.0 mm in L. antipoda), double dorsal crests on 1–2 last branchiate chaetiger(s), an occipital antenna on the prostomium, and notopodial postchaetal lamellae of chaetiger 4 smaller than those of chaetiger 3 (instead of much bigger as in L. antipoda).

Etymology. The name of the species refers to the House of Grimaldi, the princely family of Monaco and, more specifically, it is dedicated to Prince Albert I, who collected some of the specimens used for the present species description.

Distribution. Mediterranean Sea (Fig. 14A). At 4–80 m depth.