Levinsenia tribranchiata Çinar, Dagli & Açik, 2011

Erdoğan-Dereli, Deniz & Çinar, Melih Ertan, 2021, Levinsenia species (Annelida: Polychaeta: Paraonidae) from the Sea of Marmara with descriptions of two new species, Zootaxa 4908 (2), pp. 151-180 : 167-169

Levinsenia tribranchiata Çinar, Dagli & Açik, 2011

( Figures 12–14 )

Levinsenia tribranchiata Çinar, Dagli & Açik, 2011:2136–2140 , Figs 11–12 .

Material examined. ESFM-POL/2013-103 , 07 June 2013, Y5, 40°20’55’’N, 26°40’38’’E, 25 m, mud, 1 specimen ; ESFM-POL/2013-1169 , 07 June 2013, Y7, 40°24’28’’N, 26°51’24’’E, 25 m, maerl bed, 9 specimens ; ESFM-POL/2013-1171, 09 June 2013, Y17, 40°39’58’’N, 27°41’08’’E, 50 m, mud, 44 specimens; ESFM-POL/2013-1173 , 16 June 2013, Y25, 40°24’48’’N, 28°20’41’’E, 25 m, sandy mud with Amphiura filiformis , 1 specimen .

Description. All specimens incomplete, 6.8–9.2 mm, 0.12–0.20 mm wide with 35–60 chaetigers. Color in alcohol dull white. Body long, fragile, slender and thin, anterior part of body wider and anterio-dorsal side slightly swollen, posterior part of body filiform ( Fig. 12A ).

Prostomium conical, wider than long (ratio length / width: 0.90), anterior part more or less rounded with a cylindrical palpode, without eyes. A pair of nuchal organs as narrow deep, short slits, vertically placed on dorso-lateral sides of posterior part of prostomium; with scarce internal cilia; without pigmentation ( Fig. 13A, D ). Cilia patches and cheek organ absent on lateral side of prostomium. Lateral organ (lo) located on lateral sides of prostomium, more or less elliptical, with irregularly arranged pores ( Fig. 13 D–E).

Peristomium indistinct on dorsal and lateral sides, only discernable under SEM, partly fused with anterior margin of chaetiger 1 on dorsal side. Mouth with three buccal lips; two placed anteriorly and one placed posteriorly with five longitudinal folds, extending to anterior margin of chaetiger 1. A pair of ciliary slits (csal) present on anterior margin of anterior lips, proboscis with dense cilia. ( Fig. 13 B–C).

Branchiae always three pairs, beginning on chaetiger 6; slightly flattened dorso-ventrally, cylindro-conical shaped, with a rounded tip; dense ciliary bands present on both sides of outer margin of branchiae until subdistal region ( Figs 12B ; 14 A–B); 71 μm long in anterior part, 60 μm in middle part, 41 μm in posterior part of branchial region. Notopodia completely fused with branchiae on first branchial chaetiger, partly fused on remaining branchial chaetigers ( Figs 14 A–B, D)

Interramal lobes and notopodial papilla absent. Notopodial postchaetal lobes short, cirriform on chaetigers 1–5; relatively long, digitiform on chaetigers 6–9; long, filiform in posterior region. Neuropodial postchaetal lobes absent ( Fig. 14 A–E).

Lateral sense organs present on all chaetigers, located between notopodia and neuropodia, just posterior to notopodial postchaetal lobes; elliptical with irregularly clustered pores from prebranchial region to end of branchial region; straight line-shaped with regularly clustered pores from posterior part of branchial region to end of body ( Fig. 14 C–E); with 7–8 pores in prebranchial region (long axis of organ: 3–4 μm), with 16–18 pores (long axis: 6–6.5 μm) in branchial region, with 14–16 pores (long axis: 6–6.5 μm) in posterior region; with flexible cilia distinctly protruding from opening or embedded into pore.

Three types of chaetae present on chaetigers: limbate, capillary and modified neurochaeta.

Limbate chaetae present in notopodia from chaetiger 1 to chaetiger 5–9 and in neuropodia from chaetiger 1 to chaetiger 10–13, long, thin and straight with fibrils along edge (hirsute), positioning straight, colorless; in notopodia, numbering 7–9, arranged in two rows, ca. 114 µm long; in neuropodia, numbering 8–10, arranged in two rows, ca. 130 µm long.

Capillary chaetae starting from chaetiger 6–14 to posterior-most chaetiger, arranged as rows; in middle notopodia, numbering 7–8 in each ramus, two rows and 90 μm; in posterior notopodia, numbering 4–5 in each ramus, two rows and 73 μm long; in middle neuropodia, numbering 13–15 in each ramus, two rows and 150 μm long; in posterior neuropodia, numbering 2–3 in each ramus, one row and 52 μm long.

Modified neuropodial chaetae starting from chaetigers 13–15 to posterior-most chaetiger, numbering 3–5 in each neuropodium, arranged in one row, superior chaetae relatively straight and long, inferior chaetae much shorter and curved, about 17 μm long, hook-shaped, slightly curved, with a distinct, fibrillar hood on convex side, not reaching to tip ( Figs 12C ; 14E ).

Pygidium missing.

Reproduction. Some specimens of Levinsenia tribranchiata from the Sea of Marmara had eggs in their coelomic cavities from chaetiger 15 to the end of the body; each chaetiger had 10 eggs. The egg diameter varied between 60 and 134 μm. Çinar et al. (2011) reported egg-bearing specimens of this species in April from the Sea of Marmara, with diameters varying between 45 and 95 μm.

Remarks. The specimens Levinsenia tribranchiata collected during the present study closely coincided with the original description of the species.

Compared to other Levinsenia species, L. tribranchiata has a different sensory organ, the lateral organ, placed on the lateral sides of the prostomium. This type of lateral organ is first described for the genus Levinsenia , although it was previously described for Paradoneis longifurcata ( Erdoğan-Dereli & Çinar 2019) . It is noteworthy that these two species belonging to different genera share the same morphological structure.

Habitat and Distribution. This species was found on soft substrata between 25 and 50 m depths in the present study. This species was also reported from similar habitats between 17 and 100 m depths in the Sea of Marmara, and the Aegean and Levantine Seas ( Çinar et al. 2011; 2014).

Figures

FIGURE 11. Levinsenia materi (ESFM-POL/2013-1111). A, Lateral view of first two branchial chaetigers; B, Lateral view of second branchial chaetiger, with notopodial postchaetal lob emerging on branchiae; C, Lateral view of middle branchial region; D, Parapodium from posterior region with modified neurochaetae, notopodial postchaetal lobe and lateral sense organ. Scale bar: A, 51 µm; B, 16 µm; C, 42 µm; D, 19 µm. Abbreviations: ant, anterior region; bran, branchiae; lso, lateral sense organ; ntpcl, notopodial postchaetal lobe; post, posterior region.

FIGURE 12. Levinsenia tribranchiata (ESFM-POL/2013-1175). A, General view of body, stained with Shirlastain-A; B, Dor- sal view of anterior part of body, stained with Shirlastain-A; C, Modified neurochaeta from posterior chaetiger. Scale bar: A, 575 µm; B, 240 µm; C, 34 µm.

FIGURE 13. Levinsenia tribranchiata (ESFM-POL/2013-1171). A, Dorsal view of prostomium and first chaetiger; B, Ventral view of prostomium and first chaetiger with a ciliated proboscis; C, Ventral view of prostomium and first chaetiger with ciliary slits on anterior lips (csal); D, Lateral view of prostomium with lateral organ, nuchal organ and eversible palpode; E, Lateral organ on lateral side of prostomium. Scale bar: A, 52 µm; B, 87 µm; C, 63 µm; D, 40 µm; E, 7 µm. Abbreviations: csal, ciliary slits of anterior lips; ep, eversible palpode; lo, lateral organ; no, nuchal organ.

FIGURE 14. Levinsenia tribranchiata (ESFM-POL/2013-1171). A, B, Antero-lateral view of branchial chaetigers; C, No- topodium of first chaetiger with lateral sense organ and notopodial postchaetal lobe; D, First branchial chaetiger with lateral sense organ and notopodial postchaetal lobe emerging on branchia; E, Parapodium from a posterior chaetiger with modified neurochaetae, lateral sense organ and notopodial postchaetal lobe. Scale bar: A, 71 µm; B, 38 µm; C, 13 µm; D, 14 µm; E, 10 µm. Abbreviations: ant, anterior; bran, branchiae; lso, lateral sense organ; ntpcl, notopodial postchaetal lobe; mneuc, modified neurochaetae; post, posterior.