Aricidea (Acmira) simonae Laubier & Ramos 1974

Aricidea (Acmira) simonae Laubier & Ramos, 1974

(Figures 13–16)

Aricidea simonae Laubier & Ramos 1974: 1123–1127, figs. 9–10.

Aricidea (Acmira) simonae: Aguirrezabalaga & Gil 2009: 662–664, fig. 21 B–C; Kurt-Şahin et al. 2019: 161–163, fig. 8.

Material examined. ESFM-POL/2012-495, 01 October 2012, station K15, 40°41’38’’N, 29°36’26’’E, 0,5 m, Mytilus galloprovincialis, 1 specimen; ESFM-POL/2013-1141, 08 June 2012, station Y15, 40°25’41’’N, 27°27’57’’E, 50 m, fine sand, 1 specimen; ESFM-POL/2013-1142, 09 June 2013, station Y17, 40°39’58’’N, 27°41’08’’E, 50 m, mud, 4 specimens; ESFM-POL/2013-1145, 11 June 2013, station Y18, 40°54’28’’N, 27°33’24’’E, 100 m, sand with mud shell fragments, 2 specimens; ESFM-POL/2013-1146, 12 June 2013, station Y19, 40°58’36’’N, 27°42’39’’E, 25 m, maerl bed, 1 specimen; ESFM-POL/2013-1147, 13 June 2013, station Y24, 41°03’55’’N, 28°09’12’’E, 10 m, sandy mud with shell fragments, 1 specimen; ESFM-POL/2013-1148, 16 June 2013, station Y24, 41°00’16’’N, 28°07’50’’E, 50 m, sand with mudy shell fragments, 4 specimens; ESFM-POL/2013-590, 23 June 2013, station Y32, 40°55’06’’N, 28°34’11’’E, 100 m, sandy mud, 1 specimen.

Description. Largest specimen incomplete, 26.5 mm long, 1.33 mm wide, with 85 chaetigers. Color in alcohol usually white, with brown speckles on body. Body stout; straight, anterior part and posterior part of body nearly same thickness (Fig. 13A).

Prostomium subtriangular, much wider than long (ratio length / width: 0.81); anterior margin rounded, with eversible palpode; eyes absent (Figs. 13B; 14 A–C). Crown-like ciliary band (clcb) present (Figs 14 B–C). M-shaped transversal ciliary band (cb) present, thin, placed just anterior to antenna and contacting nuchal organs (Fig. 14C). Antenna short, thin, reaching the end of prostomium; inflated on tip (antenna length / prostomium length: 0.35); with a central insertion (Figs 13E; 14 A–C). A pair of nuchal organs long, wide and slightly curved slits placed laterally in posterior part of prostomium; more or less concave shape; extending almost 3/5 of prostomium; without coloration (Figs 13E; 14C). Mouth with three buccal lips; two placed anteriorly, one placed posteriorly and extending to anterior margin of chaetiger 2, with five longitudinal folds.

A dorsal ciliary band (dcb) present on mid-dorsal transversal line of each prebranchial and branchial chaetigers (Fig. 14C). Short dorsal ciliary bands (sdcb) absent. Ciliary bands absent on ventral side of body.

Branchiae 20–24 pairs, starting on chaetiger 3; thin, cylindro-conical shaped and somewhat flattened, with a rounded tip; shape similar along branchial region; 710 μm long in anterior region, 860 μm in middle region and 645 μm in posterior region; ciliary bands on both sides of branchiae (Figs 13 A–B; 15A, C).

Interramal lobes present in branchial region, located between noto- and neuropodia as a distinct large ridge (Figs 13 B–C, F; 15A, C; 16B). Notopodial papilla absent (Fig. 15A, C). Notopodial postchaetal lobes long, thin and filiform on first two chaetigers; long and digitiform in branchial region; and becoming shorter in posterior region (Figs 13C, F; 15 A–C). Neuropodial postchaetal lobes absent. Ventral lobes present, from chaetiger 1 to chaetiger 14 (Figs 13F; 15A, C).

Lateral sense organs present, from chaetiger 1 to end of branchial chaetigers; located between notopodia and neuropodia, just posterior to notopodial postchaetal lobes; each sense organ in a straight line with regularly clustered pores; with 25–27 pores in prebranchial region (long axis of organ: 7–8 μm), and about 50–52 pores (long axis: 16–17 μm) in branchial region; with flexible cilia distinctly protruding from opening or embedded into pores (Fig. 16 A–D).

Two main types of chaetae present in chaetigers; capillary and modified neurochaetae (Figs 13D, F; 15 B–D; 16B). Capillary chaetae arranged in bundles, present on both neuropodia and notopodia of all chaetigers (Figs 15 B–D; 16B); approximately 355 μm long in anterior region, 494 μm long in middle region, 655 μm long in posterior region. Anterior notopodia with 22–34 capillary chaetae; middle notopodia with 28–37 capillary chaetae; posterior notopodia with 10–14 capillary chaetae. Anterior neuropodia with 28–37 capillary chaetae; middle neuropodia with 35–41 capillary chaetae; posterior neuropodia with 9–12 capillary chaetae. Modified neuropodial chaetae robust, long, with a slightly curved subterminal region (Fig. 13D); present from chaetiger 57 to posterior end, numbering 12–15; superior chaetae longer (about 115 μm).

Pygidium missing.

Remarks. The specimens of Aricidea simonae from the Sea of Marmara had interramal lobes between the noto- and neuropodia. These were not been mentioned in the original and subsequent descriptions of this species (Laubier & Ramos 1974; Hartmann-Schröder 1996; Aguirrezabalaga 2012; Kurt-Şahin et al. 2019). Although not described, Laubier & Ramos (1974) illustrated this character in the cross-section of a chaetiger from the branchial region (see Figure 10B).

In contrast to other Aricidea species found in the study area, which have more or less convex-shaped nuchal organs, Aricidea simonae has long concave-shaped nuchal organs (see Figs. 3C; 6D; 11C; 20B; 26F; 31B; 34C; 40B; 44C; 48A). This type of nuchal organ was previously illustrated on the prostomium of A. simplex Day, 1963 (Day 1963; Strelzov 1979; Blake 1996), A. longicornuta Berkeley & Berkeley, 1950 (Berkeley & Berkeley 1950), A. mirifica Strelzov, 1973 and A. pulchra Strelzov, 1973 (Strelzov 1979), and A. neosuecica nipponica Imajima, 1973 (Imajima 1973).

Among the other species found in the present study, the M-shaped ciliary band on the prostomium is unique for A. simonae and A. cerrutii. However, unlike A. cerrutii, this ciliary band is associated with the nuchal organs in A. simonae.

Habitat and Distribution. Aricidea simonea was found in soft substrata and Mytilus galloprovincialis biotope at depths ranging from 0.5 m to 100 m in the Sea of Marmara. The species was previously reported on similar habitats between 2 and 1113 m depths in the north-east Atlantic Ocean (Gil & Sard 1999; Aguirrezabalaga & Gil 2009), eastern (Çinar et al. 2014) and western Mediterranean Seas (Laubier & Ramos 1974; Katzmann & Laubier 1975), and the Black Sea (Kurt-Sahin et al. 2019).