Aricidea (Strelzovia) mirunekoa Aguirrezabalaga & Gil 2009

Aricidea (Strelzovia) mirunekoa Aguirrezabalaga & Gil, 2009

(Figures 47–49)

Aricidea (Strelzovia) mirunekoa Aguirrezabalaga & Gil 2009: 655, 658–659, 661, figs. 18, 19 C–D; Aguirrezabalaga 2012: 199–201, figs. 79–80.

Material examined. ESFM-POL/2013-1002, 10 June 2013, station Y13, 40°46’23’’N, 27°23’43’’E, 500 m, mud, 1 specimen; ESFM-POL/2013-637, 11 June 2013, station Y18, 40°59’52’’N, 27°41’59’’E, 1000 m, mud with shell fragmetns, 15 specimens; ESFM-POL/2013-1005, 15 June 2013, station Y21, 40°45’24’’N, 27°58’12’’E, 1100 m, mud, 12 specimens; ESFM-POL/2013-1004, 23 June 2013, station Y32, 40°53’32’’N, 28°34’16’’E, 500 m, mud, 4 specimens.

Description. Largest specimen incomplete, 4.95 mm long, 0.50 mm wide, with 33 chaetigers. Color in alcohol white. Body stout and wide in anterior part of body; gradually becoming slender towards posterior segments (Fig. 47A).

Prostomium subtriangular, without annulations, much wider than long (ratio length / width: 0.82), anterior margin rounded, without eyes (Figs 47 A–B; 48C). Crown like ciliary band (clcb) present, ciliary slits (cs) absent (Fig. 48 A–C). Antenna short and bottle-shaped, with a rounded tip (ratio antenna length / prostomium length: 0.30) and central insertion, reaching end of prostomium (Figs 47B; 48A, C). A pair of nuchal organs as wide and deep short slits placed on dorso-lateral sides of posterior prostomium, more or less convex in shape; dense internal ciliation present, cilia not reaching outer margin of slits; without pigmentation; a pair of ridges located inner side of nuchal slits (Figs 47B; 48A, C). Mouth with four lips; two placed anteriorly and two placed posteriorly and extending to anterior margin of chaetiger 1 (Figs 47 C–D; 48D).

Dorsal ciliary band (dcb) present on mid-dorsal transversal line of each prebranchial and branchial chaetigers. A pair of short dorsal ciliary bands (sdcb) present just posterior to each branchial base (Fig. 48B). Ciliary bands absent on ventral side of body (Fig. 48D).

A short swelling (ss) present on mid-dorsal side of chaetigers in prebranchial (except for chaetiger 1) and branchial regions; a pair of weakly developed skin folds (sf) located on dorso-lateral sides of each chaetiger in pre- and branchial regions (Figs 47A, E; 48B).

Branchiae 19 pairs, starting in chaetiger 4. Branchiae flattened and tapering; becoming longer with elongated pointed tips in posterior branchial region (Figs 47A, E; 48B); approximately 344 μm long in anterior region, 538 μm long in middle region and 570 μm long in posterior region.

Notopodial postchaetal lobes present, short and cirriform in first chaetiger; becoming long and digitiform with an asymmetrical swelling on base from chaetiger 2 to middle part of branchial chaetigers; long and digitiform, without any swelling basally, from middle part to posterior part of branchial chaetigers; thin and filiform in posterior chaetigers (Figs 47B, E–G; 48A–B; 49A, C–D). Neuropodial lobes small, only present in first 11 chaetigers. Ventral lobe present on chaetigers 3–18, rounded (Figs 48D; 49B). Notopodial papillae absent.

Three types of chaetae present on chaetigers: limbate, capillary and modified neurochaetae. Limbate chaeta of two types; first type present in notopodia of chaetigers 1–15, numbering 18–20, arranged in three rows, ca. 286 µm long, thin and straight with fibrils along edge (hirsute), directed posterio-dorsal side, light rose colored; second type present in neuropodia of chaetigers 1–15, numbering 25–30, arranged in five rows, ca. 237 µm long, much wider and sigmoid with fibrils along edge (hirsute), directed posterio-ventral side, light rose-colored (Fig. 49 A–D).

Capillary chaetae starting in noto- and neuropodia of chaetiger 16 and present on all subsequent chaetigers; in middle notopodia numbering 13–20, arranged in 2–3 rows, ca. 360 μm long; in posterior notopodia numbering 5–6, arranged in one row, 223 μm long; in middle neuropodia numbering 15–20, arranged in two rows, 231 μm long; in posterior neuropodia numbering 6–10, arranged in one row, 218 μm long.

Two types of modified neuropodial chaetae present, from chaetigers 23–31 to posterior end; each neuropodium bearing 2–3 modified chaetae; gradation in lenght from short inferior to long superior (Fig. 47G); first type Strelzoviatype, very long (average length: 115 µm), becoming gradually thinner with numerous fibrils on convex side; second type like Strelzovia - type relatively short (average length: 88 µm), becoming abruptly thinner, with numerous fibrils on convex side (Figs 47 G–H; 48E).

Pygidium missing.

Remarks. The morphology of the specimens of Aricidea mirunekoa from the Sea of Marmara resembles the original description of the species by Aguirrezabalaga & Gil (2009). Aricidea mirunekoa is most similar to A. mariannae, which is also a deep-water Mediterranean species (Katzmann & Laubier 1975). The only difference between these two species is the length of the notopodial lobe on chaetigers 2 and 3; with longer lobes in chaetiger 2 in A. mirunekoa and longer ones in chaetiger 3 in A. mariannae.

Habitat and Distribution. Aricidea mirunekoa is a deep-sea species, found on muddy bottoms at 500–1100 m depths in the Sea of Marmara. It is a new species for the Mediterranean fauna. According to Aguirrezabalaga & Gil (2009), this species was collected from similar habitats and between 480 and 968 m depth in northeast Atlantic Ocean.