Aricidea (Acmira) meridionalis Laubier & Ramos, 1974

Erdoğan-Dereli, Deniz & Çinar, Melih Ertan, 2020, The diversity of the genus Aricidea (Polychaeta: Paraonidae) from the Sea of Marmara, with descriptions of two new species and two new records for the Mediterranean fauna, Zootaxa 4844 (1), pp. 1-73 : 43-48

Aricidea (Acmira) meridionalis Laubier & Ramos, 1974 new status

( Figures 29–32 )

Aricidea suecica meridionalis Laubier & Ramos 1974: 1127–1131 , fig. 11.

Material examined. ESFM-POL/2013-1008 , 06 June 2013, station Y1, 40°00’32’’N, 26°13’04’’E, 25 m, mud, 1 specimen ; ESFM-POL/2013-1011 , 10 June 2013, station Y13, 40°45’27’’N, 27°21’24’’E, 100 m, mud, 1 specimen ; ESFM-POL/2013-1015 , 08 June 2013, station Y15, 40°19’11’’N, 27°33’51’’E, 10 m, sandy mud, 6 specimens ; ESFM-POL/2013-1016 , 09 June 2013, station Y16, 40°24’13’’N, 27°39’47’’E, 41 m, mud, 2 specimens ; ESFM-POL/2013-1020, 23 June 2013, station Y32, 40°55’06’’N, 28°34’11’’E, 100 m, sandy mud, 1 specimen; ESFM-POL/2013-1023, 24 June 2013, 40°54’50’’N, 28°52’12’’E, station Y 34, 100 m, sandy mud with shell fragments, 4 specimens.

Additional material examined. Aricidea suecica meridionalis , Holotype, MNHN-1261.

Description. Largest specimens incomplete, 4.19 mm, 0.14 mm wide with 76 chaetigers. Color in alcohol usually yellow or dark orange ( Figs 29 A–C, E, G; 30A–D). Body stout and long; anterior part of body slightly wider, posterior part of body gradually becoming thinner.

Prostomium subtriangular, width and length almost equal (ratio length / width: 0.96); anterior margin rounded; without eyes. Crown-like ciliary band (clcb) and a pair of ciliary short slits (cs) present ( Fig. 31 A–C). Antenna long, digitiform with a thick base gradually tapering, with a rounded tip (antenna length / prostomium length: 0.86), extending to posterior margin of chaetiger 1 ( Fig. 30A ); inserted centrally. A pair of nuchal organs as wide, deep, long and slanted slits placed on dorso-lateral sides of posterior prostomium; more or less convex in shape; dense internal ciliation present, cilia not reaching to outer margin of slits; without pigmentation ( Fig. 31 A–D). Mouth with three buccal lips; two placed anteriorly, one placed posteriorly and extending to anterior margin of chaetiger 3, with nine longitudinal folds; Y-shaped gap present between anterior lips ( Fig. 31E ). Proboscis without lobes, with cilia.

A dense 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 posterior to each branchial base ( Figs 31A ; 32A ). Ciliary bands absent on ventral side of body ( Fig. 31E ). A short ridge (sr) present on mid-dorsal side of chaetigers in branchial region. A pair of skin folds (sf) located on each dorso-lateral sides of pre- and branchial chaetigers ( Figs 29 B–C, G; 30B–C; 31A).

Branchiae 19 pairs, starting in chaetiger 4; very fragile, flattened and cylindro-conical, slightly bulbous with a rounded tip, becoming longer and with slightly elongated tips in middle and posterior parts of branchial region; posterior branchiae with asymmetrical basal enlargement; branchia usually shorter than segment width ( Figs 30B ; 31A ); approximately 417 μm long in anterior region, 475 μm long in middle region, 555 μm long in posterior region; a dense ciliary band on both sides of branchiae.

Notopodial postchaetal lobes long and digitiform in first two chaetigers; long, thick and digitiform with asymmetrical basal enlargement in chaetiger 3 and in branchial chaetigers; becoming longer and thicker in postbranchial region ( Figs 29D ; 30 A–D; 31A; 32C). Neuropodial postchaetal lobes present between chaetiger 1–19, short, digitiform anteriorly; short, cirriform posteriorly ( Figs 29 D–E; 30D; 32B). Notopodial papillae absent. Ventral lobe present on chaetigers 4–31, as a small, rounded tubercule, on posterior-ventral margins of each chaetiger ( Figs 29 D–E; 30D; 31E; 32B).

Lateral sense organs present on all chaetigers, located between notopodia and neuropodia, posterior to notopodial postchaetal lobes; straight line-shaped (long axis: 20–21 μm) with regularly clustered pores on posterior part of body, with ca. 80–85 pores ( Fig. 32F ).

Three types of chaetae present on chaetigers: limbate, capillary and modified neurochaetae. Limbate chaetae of two types; first type present only in notopodia of chaetigers 1–21, numbering 25–30, arranged in bundles, ca. 287– 360 μm, thin, long and straight with fibrils along edge (hirsute), colorless; second type only present in neuropodia of chaetigers 1–21, numbering 30–37, arranged in bundles, ca. 231–237 μm long, much wider and relatively shorter, sigmoid with fibrils along edge (hirsute), dorsal to ventral in fascicle, colorless ( Figs 30E ; 32C ).

Capillary chaetae arranged in bundles, from noto- and neuropodia of chaetiger 22 to posterior end; in middle notopodia numbering 20–30, ca. 423 μm long; in posterior notopodia numbering 8–10, ca. 382 μm long; in middle neuropodia numbering 18–24, ca. 410 μm long; in posterior neuropodia numbering 5–12, ca. 354 μm long.

Modified neuropodial chaetae starting in chaetiger 37–55 and present on all suqsequent chaetigers, numbering 4–8 in each neuropodium; slender and tapering, slightly curved towards terminal region, with a distinctly rounded tip; pubescence present on terminal and subterminal regions; bearing a very strong and long arista on tip, superior ones longer (about 190 μm) ( Figs 29F ; 30 F–G; 32D–E).

Pygidium missing in all specimens.

Remarks. The specimens identified as Aricidea meridionalis n. stat. from the Sea of Marmara are similar to the holotype of Aricidea suecica meridionalis . Aricidea meridionalis n. stat. was originally described as a subspecies of Aricidea suecica , but it has a number of different characters when compared to A. suecica Eliason, 1920 ; so we raised it from the subspecies to the species level. The main diagnostic characters are: (1) Antenna long, digitiform, with an enlarged base, tapering and with a rounded tip in A. meridionalis n. stat. vs. long, stout, without an enlarged base, obovoid in shape in A. suecica ; (2) First two notopodial postchaetal lobes: digitiform and very long in A. meridionalis n. stat. vs. cirriform and very short in A. suecica ; (3) Modified neurochaeta: one type (hook-shaped) in A. meridionalis n. stat. vs. two types ( Strelzovia -type and hook-shaped) in A. suecica ; (4) Ventral lobe: present in A. meridionalis n. stat. vs. absent in A. suecica .

Habitat and Distribution. Aricidea meridionalis n. stat. was found in soft substrata at depths ranging from 10 and 100 m in the Sea of Marmara. According to the previous studies, this species was reported from similar habitats between 20 and 80 m depths in the northeast Atlantic Ocean ( Aguirrezabalaga 2012), western ( Laubier & Ramos 1974; Castelli 1988) and eastern Mediterranean ( Çinar et al. 2014).

Subgenus Aricidea (Aricidea) [ Webster, 1879 , sensu stricto]

Figures

FIGURE 29. Aricidea (Acmira) meridionalis n. stat. (ESFM-POL/2013-1015).A, Dorsal view of anterior end; B, Dorsal view of anterior end; C, Dorsal view of anterior end; D, Cross section of chaetiger 5; E, Ventral view of chaetigers 12-14; F, Modified neurochaetae of posterior chaetiger; G, Dorsal view of mid-branchial region. Abbreviations: neupcl, neuropodial postchaetal lobe; ntpcl, notopodial postchaetal lobe; sf, skin fold; sr, short ridge; vl, ventral lobe. Scale bar: A, 408 µm; B, 440 µm; C, 220 µm; D, 217µm; E, 111 µm; F, 73 µm; G, 264 µm.

FIGURE 30. Aricidea (Acmira) meridionalis n. stat. Holotype MNHN-1261.A, Dorsal view of anterior end; B, Dorsal view of mid-branchial chaetigers; C, Dorsal view of posterior region; D, Dorsal view of branchial chaetigers and lobes; E, Notopodial limbate chaetae of chaetigers 1–2; F, Modified neurochatea of posterior chaetiger; G, Modified neurochatea on posterior chaetiger. Abbreviations: neupcl, neuropodial postchaetal lobe; ntpcl, notopodial postchaetal lobe; sf, skin fold; sr, short ridge; vl, ventral lobe. Scale bar: A, 276 µm; B, 225 µm; C, 236 µm; D, 65 µm; E, 38 µm; F, 56 µm; G, 28 µm.

FIGURE 31. Aricidea (Strelzovia) meridionalis n. stat. (ESFM-POL/2013-1015). A, Dorsal view of anterior end; B, Dorsal view of prostomium; C, Dorsal view of half prostomium; D, Nuchal organ; E, Ventral view of anterior end.Abbreviations: clcb, crown-like ciliary band; cs, ciliary slits; dcb, dorsal ciliary band; neupcl, neuropodial postchaetal lobe; no, nuchal organ; sdcb, short dorsal ciliary band; sf, skin fold; sr, short ridge; vl, ventral lobe. Scale bar: A, 366 µm; B, 112 µm; C, 89 µm; D, 32 µm; E, 565 µm.

FIGURE 32. Aricidea (Strelzovia) meridionalis n. stat. (ESFM-POL/2013-1015). A, Dorsal view of mid-branchial chaetigers, short dorsal ciliary bands; B, Ventral view of neuropodia of mid-branchial chaetigers; C, Cross section of a mid-branchial chaetiger, different limbate chaetae types; D, Modified neurochaetae of posterior chaetiger; E, Subdistal part of modified neurochaeta; F, Lateral sense organ of posterior chaetiger.Abbreviations: dcb, dorsal ciliary band; ntpcl, notopodial postchaetal lobe; neupcl, neuropodial postchaetal lobe; sdcb, seconder dorsal ciliary band; sf, skin fold; sr, short ridge; vl, ventral lobe. Scale bar: A, 140 µm; B, 88 µm; C, 123 µm; D, 19 µm; E, 8 µm; F, 9 µm.