First record of Lepidonotus tenuisetosus (Annelida: Polynoidae) from Tunisia with distributional notes Abstract Author Chaibi, Marwa Department of Biology, Faculty of Sciences of Tunis, University of Tunis El Manar, 2092 Tunis, Tunisia Author Azzouna, Atf Department of Biology, Faculty of Sciences of Tunis, University of Tunis El Manar, 2092 Tunis, Tunisia Author Martin, Daniel Centre d’Estudis Avançats de Blanes, carrer d’accés a la Cala Sant Francesc 14, 17300 Blanes, Girona, Catalunya, Spain text Mediterranean Marine Science 2023 2023-01-23 24 1 7 18 http://dx.doi.org/10.12681/mms.30404 journal article 299056 10.12681/mms.30404 1283312d-c182-45b7-a64d-87cd13ba8e15 1108-393X 11989992 Lepidonotus tenuisetosus ( Gravier, 1902 ) Euphione tenuisetosa . Gravier (1902) : 222 -226, textfigs. 228-231, pl. 8 figs. 123-126. Lepidonotus tenuisetosus . ( Wehe, 2006 ); 107-109, fig. 24 a-l. Non Barnich & Fiege (2003) : 86 , fig. 44; non Çinar (2009) : 2286 , fig. 2A. Material examined . CEAB .AP.985, 30 specimens , collected from Mars 2018 to Mars 2019 in Radès Area , Gulf of Tunisia ( 36.809424 N ; 10.285653 E ) by Marwa Chaibi , preserved in 70% ethanol. Additional material. NHMR , PMR- 17630, 1 specimen, preserved in 70% ethanol, Croatia , Adriatic Sea , 30/07/2007 , collected by B. Mikac. HCMR _ Nag _ EL_01_2008_0185 and _0194, 2 specimens , preserved in 96% ethanol, 18/06/2008 , rocky substrate with photophilic algae, ( 35.4233°N , 24.9838°E ), Crete , collected by G. Chatzigeorgiou. Description . Complete specimens with body 7.5-18.5 mm long, 1.36-2.44 wide (without parapodia), 2.08-4.08 mm wide (with parapodia) with 26 segments (25 chaetigers); elongated, flattened dorsoventrally ( Fig. 2 A-B), subrectangular in cross-section. Prostomium bilobed, without cephalic peaks; median antenna smooth, with ceratophore in anterior notch, fused to prostomium, style smooth, gradually tapering, without subterminal swelling; lateral antennae smooth, inserted terminally, with ceratophores fused to prostomium, styles smooth, tapering progressively, without subterminal swelling; palps smooth and gradually tapering ( Fig. 2 C-E). Two pairs of eyes close to each other, dorsolaterally on widest part of prostomium ( Fig. 2C ). Facial tubercle present. Pharynx with 18 big, conical, terminal papillae ( Fig. 2 D-F). Tentaculophores inserted laterally to prostomium, with few chaetae and a pair of dorsal and ventral tentacular cirri with smooth, gradually tapering styles. Second segment with first pair of elytra, sub-biramous parapodia and long, tapering, ventral cirri. Twelve pairs of elytra ( Fig. 1A ) on elytrophore segments ( Fig. 3A ) (2, 4, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23), fully covering body dorsally; first pair round, second reniform ( Fig. 2G ), then progressively oval ( Fig. 2H ); with marginal fringing papillae, mostly digitiform but with some small, globular ( Fig. 2I ); surface with some central and posterior small macrotubercles with blunt or warty tips ( Fig. 2I, 2J ) and conical to cylindrical microtubercles ( Fig. 2 I-2K). Cirrophorous segments with dorsal cirri with smooth styles, gradually tapering, without subterminal swelling, reaching beyond tips of neurochaetae; styles of ventral cirri smooth, tapering, shorter than neuropodia; nephridial papillae well-visible, digitiform ( Fig. 3B ). Parapodia sub-biramous, noto- and neuropodia with elongate acicular lobe; tips of noto- and neuroacicula penetrating epidermis ( Fig. 3A, 3B ). Notochaetae slender, with numerous rows of small spines and tapering, capillary tips ( Fig. 4A, 4B ); neurochaetae of chaetiger 1 (i.e., second segment) slender than those of remaining chaetigers, with numerous rows of spines, similar to notochaetae but shorter ( Fig. 3C ); from chaetiger 3, all neurochaetae with unidentate tips, stouter than notochaetae, falcate, with numerous rows of spines in distal region ( Fig. 3D ). Nephridial papillae from segment 8 (chaetiger 7) onwards. Remarks . The specimens from Tunisia fully agree with the original description by Gravier (1902) , except for the special neurochaetae of chaetiger 1 (i.e., segment2), which do not show the terminal tuft of long, tight filiform extensions illustrated by Gravier (1902) in his fig. 231. Particularly, our specimens agree with the revision of types and additional materials by Wehe (2006) , ( Tables 1 and 2 , Fig. 5 A-5E), including the shape of the neurochaetae of chaetiger 1, which he described as “ Neurochaetae of second segment altered (Fig. 24 l), more slender, with more numerous rows of spines and fine tips ” and illustrated in his figure 24 l as lacking the terminal tuft of filiform extensions ( Wehe, 2006 ). Conversely, they differ from the Sinai specimens reported by Barnich & Fiege (2003) , specifically in the shape of the antennae and dorsal cirri, in the eye position, the types of micro- and macrotubercles and the shape of neurochaetae tips ( Fig. 5 F-5I), which fully agree with the features of L. carinulatus ( Tables 1 and 2 , Fig. 5 J-Q). Fig. 2: Lepidonotus tenuisetosus . A. Whole body, dorsal view. B. Whole body, ventral view. C. Anterior region (without elytra), dorsal view. D. Anterior region (pharynx everted), dorsal view. E. Anterior region (pharynx everted), ventral view. F. Anterior region (pharynx everted), lateral view. G. Second elytra. H. Tenth elytron. I. Detail of fringing papillae from the tenth elytron. J. Detail of macrotubercles from the tenth elytron. K. Detail of microtubercles from tenth elytron. Fig. 3: Lepidonotus tenuisetosus . A. Elytrophorous parapodium. B. Cirrophorous parapodium. The very small specimen (i.e., an anterior fragment with only eight chaetigers, measuring about 1.6 mm long and 0.4 mm wide) reported as L. tenuisetosus from the Croatian coasts of the northern Adriatic Sea is in very poor conditions, lacking elytra and all appendages ( Fig. 6A, 6B ). However, the chaetae are well-visible, being uni-and bidentate, with several rows of spines and the distal ones much longer than the basal ones ( Fig. 6 C-6E). Therefore, if it belongs to Lepidonotus (which cannot be confirmed considering its present conditions), it could be L. carinulatus , but certainly not L. tenuisetosus . The specimens from Crete show unidentate chaetae, but the antennae and cirri have distal swellings and pigmented bands and, most importantly, the elytra have smooth margins ( Fig. 7 A-7E). Therefore, they belong to L. clava . Fig. 4: Lepidonotus tenuisetosus . A. Notochaetae from chaetiger 15. B. Tip of notochaeta. C. Neurochaetae from first chaetiger. D. Neurochaetae from chaetiger 15. Fig. 5: Lepidonotus tenuisetosus , redrawn from Wehe (2006) : A. Cephalic region, dorsal view. B. Second right elytron. C. Macrotubercles. D. Fringing papillae. E. Neurochaetae. Lepidonotus carinulatus , redrawn from Barnich & Fiege (2003) : F. Cephalic region, dorsal view. G. Third right elytron. H. Lateral margin showing macrotubercles, digitiform papillae and fringing papillae. I. Neurochaetae. Lepidonotus carinulatus , redrawn from Wehe (2006) : J. Cephalic region, dorsal view. K. Second right elytron. L. Macrotubercle. M. Carinate microtubercles and pigmentation. N. Digitiform papillae. O. Fringing papillae. P. Upper neurochaetae. Q. Lower neurochaetae. Table 1. Main characters distinguishing between Lepidonotus tenuisetosus sensu Barnich & Fiege (2003) and Wehe (2006) and Lepidonotus carinulatus sensu Wehe (2006) .

Lepidonotus tenuisetosus		Lepidonotus carinulatus
Characters	Barnich & Fiege (2003)	Wehe (2006)	Wehe (2006)
Median ceratophore	Slightly inflated subdistally	Tapering to terminal filum, no subterminal swelling	Slightly inflated subdistally
Eye pairs on prostomium	Anterior dorsolateral on widest Anterior dorsolateral on widest Close to each other, part, posterior dorsally near hind part, posterior dorsally near hind dorsolateral margin margin
Dorsal cirri	Slightly inflated subdistally	Tapering to terminal filum, no subterminal swelling	Slight subterminal swelling and terminal filum
Elytra microtubercles	Cylindrical with multifid, crown-like tips	Posterolateral warty, with nodules Conical to globular or pointed projections
Elytra macrotubercles	Present centrally and Centrally conical and globular, Absent posteriorly with blunt or posterolateral warty warty tips
Neurochaetae 1st chaetiger	Slender, with numerous Slender, with numerous rows of Non-defined rows of spines and fine spines and fine tips tips
Other neucochaetae	Bidentate, with small secondary Mostly unidentate, a few minutely tooth, lower ones apparently All unidentate, with few bidentate; with numerous rows of unidentate; with several rows of rows of spines spines spines, distal ones usually much larger than basal

Table 2. Dichotomous key showing the main characters allowing distinguishing the species of Lepidonotus mentioned in this paper. *: Specimens directly observed by the authors.

Characters	Species	Location	References
1a	Elytra with smooth margins	–––	Lepidonotus clava	Greece*	Faulwetter et al. (2017) ; Chatzigeorgiou et al. (2016)
Mediterranean Sea	Barnich & Fiege (2003)
1b	Elytra with fringing papillae	–– 2
2a	Neurochaetae uni- and bidentate; antennae and dorsal cirri slightly inflated subdistally	–––	Lepidonotus carinulatus	Sinai	Barnich & Fiege (2003)
Alboran Sea	Baratech et al. (1986)
Red Sea, Arabian Sea, Indo-West Pacific	Wehe (2006)
2b	Neurochaetae unidentate; antennae and dorsal cirri tapering to terminal filum	–– 3
3a	Eyes dorsoventrally on prostomium; microtubercles with blunt or warty tips	–––	Lepidonotus tenuisetosus	Gulf of Aden	Gravier (1902)
Red Sea	Wehe (2006)
Arabian Sea	Wehe (2006)
Tunisia *	This paper
3b	Anterior pair of eyes dorsolaterally on widest part, posterior dorsally near hind margin; filiform papillae on elytra	–––	Lepidonotus sp.	Turkey	Çinar (2009 , 2013 )

Fig. 6: Lepidonotus sp. , NHMR PMR-17630, Croatia: A. Anterior end, dorsal view. B. Parapodia 7 and 8, right side. C. Neurochaetae from parapodium 8 (right side). D. Neurochaetae from parapodium 8 (left side). E. Neurochaetae from parapodium 9 (right side). Upon the authors’ request, M. E. Çinar re-examined the specimens from Mersin Bay in Turkey – ESFM-POL/05-547 (n=17, 18/09/2005 , K15, 0.2= 3 m , stones with algae, approx. ( 36.7167°N , 34.5°E ). Mersin Bay) and ESFM-POL/2005-547 (n=1, 19/09/2005 , K17, 0.1-2 m , stones with algae, approx. 36.4833°N , 34.1833°E ). Although all specimens show unidentate chaetae with all spines of a similar size, the eyes are not in dorsolateral position and the elytra show filiform papillae, which allow us confirming them as not belonging to L. tenuisetosus , being likely a different introduced or undescribed species that will require further analyses to be defined ( M.E. Çinar , personal communication). Finally, the specimens included in the faunal list of the invertebrates from the bottoms surrounding mammal bones experimentally deployed in Blanes Bay (Appendix S 1 in Taboada et al. , 2016 ) are probably lost and their identification was just tentative (S. Taboada, personal communications). Therefore, its real identity cannot be currently determined and further sampling is required to confirm which species is present in Blanes Bay. However, it must be taken into account that previous studies only reported L. clava (e.g., Camp, 1976 ; Campoy & Jordana, 1978 ; Martin, 1987 ; Plyuscheva & Martin, 2009 ). Distribution . Gulf of Aden, Red Sea, and Arabian Sea ( Gravier, 1902 ; Wehe, 2006 ); Gulf of Tunisia , Mediterranean Sea (present study). Doubtful records: India , Vietnam , South China Sea, and New Caledonia ( Uschakov, 1982 ; Hanley, 1992 ; Barnich et al. , 2004 ; Wehe, 2006 ). Previous records from Croatia ( Mikac, 2015 ; Mikac et al. , 2020 ), Greece ( Chatzigeorgiou et al. , 2016 ; Faulwetter et al. , 2017 ), Turkey ( Çinar, 2009 ; Çinar et al. , 2021 ), and Israel ( Barnich & Fiege, 2003 ; Zenetos et al. , 2010; Çinar, 2013 ) are discarded according to our results. Habitat . Common on rocks (Red Sea); found on a rocky bottom among algae ( Tunisia ). 0-0.5 m depth.