Aricidea (Acmira) pseudoassimilis, Erdoğan-Dereli & Çinar, 2020

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 : 36-43

Aricidea (Acmira) pseudoassimilis new species

( Figures 23–28 )

LSIDurn:lsid:zoobank.org:act: FB255513-A520-4155-9A9B-4D85059C5F31

Aricidea assimilis Laubier & Ramos 1974: 1117–1121 , fig. 7 (in part).

Material examined. Holotype: ESFM-POL/2013-1119 , 16 June 2013, station Y23, 40°23’55’’N, 28°09’49’’E, 10 m, mud with shell fragments . Paratypes: ESFM-POL/2013-1121 , 10 June 2013, station Y13, 40°45’27’’N, 27°21’24’’E, 100 m, mud, 1 specimen ; ESFM-POL/2013-1124 , 9 June 2013, station Y17, 40°39’58’’N, 27°41’08’’E, 50 m, mud with Amphiura sp., 5 specimens ; ESFM-POL/2013-1125 , 16 June 2013, station Y23, 40°23’55’’N, 28°09’49’’E, 10 m, sandy mud with shell fragments, 5 specimens ; ESFM-POL/2013-1128 , 16 June 2013, station Y25, 40°24’17’’N, 28°20’50’’E, 10 m, sandy mud with shell fragments, 2 specimens ; ESFM-POL/2013-1135 , 16 June 2013, station Y26, 40°22’06’’N, 28°39’55’’E, 10 m, sandy mud with shell fragments, 2 specimens .

Additional material examined: ESFM-POL/2015-264 , 12 August 2015, Aegean Sea, Enez , 40°42’40’’N, 26°01’42’’E, 21 m, sand with shell fragments, 1 specimen ; ESFM-POL/2016-262 , 13 August 2015, Aegean Sea, Bozcaada , 39°55’05’’N, 26°01’14’’E, 50 m, mud, 2 specimens ; ESFM-POL/2016-263 , 30 August 2015, Levantine Sea, Dalaman , 36°41’57’’N, 28°43’39’’E, 70 m, sandy mud with shell fragments, 1 specimen ; ESFM-POL/2016- 195 , 15 August 2016, Aegean Sea, Izmir Bay, near the opening of Gediz River , 38º34’82’’N, 26º47’79’’E, 11 m, mud, 2 specimens ; ESFM-POL/2016-196 , 15 August 2016, Aegean Sea, Aliağa , 38º49’39’’N, 26º57’07’’E, 21 m, mud with shell fragments, 1 specimen ; ESFM-POL/2016-197 , 19 August 2016, Aegean Sea, Güllük , 37º14’55’’N, 27º20’30’’E, 38 m, sandy mud, 6 specimens ; ESFM-POL/2018-123 , 15 September 2018, Black Sea, Kıyıköy , 41°39’03”N, 28°6’40”E, 27 m, sandy mud with shell fragments, 21 specimens ; ESFM-POL/2019-10 , 22 April 2019, Black Sea, Kıyıköy , 41°39’03”N, 28°6’40”E, 27 m, sandy mud with shell fragments, 155 specimens .

Description. Holotype incomplete (also all paratypes), 12.65 mm long (9.05–23.60 mm long in paratypes), 0.44 mm wide (0.29–0.53 mm wide in paratypes), with 94 chaetigers (32–128 chaetigers in paratypes). Color of holotype in alcohol yellowish to dull white (also in all paratypes); gamete bearing specimens with distinct red speckles/spots near notopodia and on several dorsal and ventral parts of body ( Fig. 25B, C , E–G); dorso-lateral red spots more conspicuous. Body cylindrical and stout; width of prebranchial and branchial regions nearly same, becoming thick on posterior region ( Figs 23A ; 25 A–C).

Prostomium subtriangular; much longer than wide (ratio length / width: 1.18); anterior margin rounded ( Figs 23A ; 24A ; 27A, C ); eyes absent in all specimens. Crown-like ciliary band (clcb) and a pair of ciliary slits (cs) present on anterior part of prostomium; ciliary slits placed just anterior to nuchal organs, weakly curved ( Figs 23A ; 24A ; 26C , E–F; 27A, C–E). Antenna short, digitiform (0.1 mm in holotype; 0.09–1.3 mm long in paratypes), located in mid-region of prostomium, extending to posterior part of prostomium; densely covered with cilia ( Figs 23A ; 24A ; 27 A–C). A pair of nuchal organs present as narrow, deep, short and slanted 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; light-orange pigmented ( Figs 25A, D ; 26E, F ; 27A, C ). Proboscis with dense cilia ( Figs 26C ; 27F ). Mouth with three buccal lips; two placed anteriorly, one placed posteriorly extending to anterior margin of chaetiger 2, with ten longitudinal folds; an I-shaped gap present between anterior lips (also in all paratypes).

A dense dorsal ciliary band (dcb) present on mid-dorsal transversal line of each prebranchial and branchial chaetigers ( Figs 23A ; 24A ; 26B ). A pair of short dorsal ciliary bands (sdcb) present, as a transversal line, just placed posterior to each branchial base ( Fig. 26A, D ). Ciliary bands absent on ventral side of body ( Fig. 26C ). A short ridge (sr) present on mid-dorsal side of chaetigers in branchial region. A pair of skin folds (sf) present at each dorso-lateral side of chaetigers in pre- and branchial regions ( Figs 25E ; 26 A–B). Irregularly distributed cilia present on body ( Fig. 28 E–F).

Branchiae numbering 16 pairs in holotype, 11–24 pairs in paratypes, starting in chaetiger 4 in all specimens; flattened, foliaceous with a rounded tip; branchial length usually shorter than segment width, becoming longer posteriorly; not elongated ( Figs 23A ; 24A, C ; 25B, C ; 26B ); branchial length / width 3.33–5; 232 μm long in anterior region, 318 μm long in middle region, 396 μm long in posterior region; dense ciliary band on both sides of branchiae.

Interramal lobes present between noto and neuropodia of chaetigers 1–14; as a rudimentary ridge in chaetiger 1, becoming thicker afterwards ( Figs 24 A–C; 27G; 28A).

Notopodial papilla and ventral lobe absent ( Fig. 28A ). Notopodial postchaetal lobes present in all chaetigers; short, digitiform, with a weak enlargement at base in first two chaetigers; stout, long, digitiform, with a weakly asymmetrical basal enlargement in branchial region; long, thin and filiform in posterior region; cilia present on notopodial lobes ( Figs 23A ; 24 A–C; 25D; 26A; 28A–B). Neuropodial postchaetal lobes present in chaetigers 1– 22; as short ridges on anterior chaetigers; getting stronger in branchial region; becoming as short ridges again in chaetigers 19–22 ( Figs 24 A–C; 28A).

Lateral sense organs present between notopodia and neuropodia of all chaetigers, posterior to notopodial postchaetal lobes; with flexible cilia distinctly protruding from opening or embedded into pore ( Fig. 28 C–D); elliptical with irregular clustered pores in prebranchial region to middle part of branchial region; straight lineshaped with regularly clustered pores in posterior part of branchial region to end of body ( Fig. 28 A–F); with 40 pores in prebranchial region (long axis of organ: ca. 6–12 μm), with 40–60 pores (long axis: 12.5–17 μm) in anterior and middle part of branchial region, with 40–70 pores (long axis: 15–20 μm) in posterior part of branchial region, with ca. 60–100 pores (long axis: 25–34 μm) in posterior region.

Three types of chaetae present in chaetigers: limbate, capillary and modified neurochaetae. Limbate chaetae of two types; first type present only on notopodia of chaetigers 1–14, numbering 35–60, arranged in four rows, ca. 191 µm long, thin, and straight with fibrils along edge (hirsute), tapering to tip, ventral to dorsal in fascicle, light-rose in type specimens, dark reddish in Black Sea specimens; second type present only in neuropodia of chaetigers 1–14, numbering 48–60, arranged in three rows, ca. 177 µm µm long, more or less sigmoid shape with fibrils along edge (hirsute), dorsal to ventral in fascicle, light-rose color in type specimens, light reddish in Black Sea specimens ( Figs 23 B–C; 26A–D; 27F–G; 28A–B).

Capillary chaetae starting in noto- and neuropodia of chaetiger 15 and present on all subsequent chaetigers; in middle notopodia numbering 8–10, arranged in 2–3 rows, 273 μm long; in posterior notopodia, numbering 6–9, arranged in one row, ca. 373 μm long; in middle neuropodia, numbering 12–20, arranged in two rows, ca. 230 μm long; in posterior neuropodia numbering 2–4, arranged in one row and ca. 369 μm long.

Modified neuropodial chaetae starting from chaetiger 34 (22–42 in paratypes) to posterior end, numbering 4–8 in each neuropodium, accompanied by capillary chaetae, brownish color in most specimens; hook-shaped, becoming subterminally thinner and with a round tip; pubescence on convex side of terminal and subterminal regions, with a long arista and terminal hairs; superior ones longer (about 169 μm) ( Figs 23 D–E; 25F, H–I; 28G).

Pygidium missing.

Reproduction. Some specimens of Aricidea pseudoassimilis n. sp. from the Sea of Marmara and Black Sea had sperm packages (two in each segment) within chaetigers from 27–32 to the end of the body. The gamete bearing specimens had red speckles near notopodia as well as two distinct additional red spots on the dorso-lateral sides and two small ones on the ventro-lateral sides of all chaetigers. In addition, a dashed red-line is present on the dorsal side of the chaetigers in the postbranchial region ( Fig. 25B , E–G).

Most of the specimens collected in the Black Sea in 2019 were mature and presented additional reddish speckles on the body. Therefore, this coloration seems to be associated with the reproduction.

Remarks. Aricidea (Acmira) pseudoassimilis n. sp. is mainly characterized by having a short, thick and digitiform antenna covered with dense cilia; by possessing interramal lobes between notopodia and neuropodia in the pre- and branchial regions; by its branchiae becoming longer towards the posterior part of the branchial region but without elongation of the tip; by the presence of small ridges on the mid-dorsal part of chaetigers; by having a pair of skin folds located in the dorso-lateral sides of each chaetiger; and by its modified neurochaeta with a rounded tip and long arista. The modified neurochaetae are distinctly amber coloured in the specimens of Aricidea pseudoassimilis n. sp. collected from the Black Sea in 2019 ( Figs 25 B–C, F–G). However, the specimens collected from the same locality in 2018 and from the Sea of Marmara lacked such coloration ( Fig. 25 A–B).

The species morphologically most similar to A. pseudoassimilis n. sp. are A. assimilis , A. flava and A. laubieri . However, these species differ from each other in terms of the following characters: (1) Antenna: short, stout with a rounded tip, extending barely to the end of the prostomium in A. pseudoassimilis n. sp.; slender, extending to the chaetiger 3 in A. flava ; long, thin, with a rounded tip, extending to the mid-line of chaetiger 1 in A. laubieri ; long, tapering to tip, extending to chaetiger 13 in A. assimilis ; (2) Interramal lobes: present in A. pseudoassimilis n. sp. and A. laubieri ; absent in A. assimilis and A. flava ; (3) Branchiae: up to 21 pairs, getting longer but not elongated posteriorly in A. pseudoassimilis n. sp.; 18 pairs, elongated posteriorly in A. flava ; up to 27 pairs, last few pairs shorter in A. laubieri ; 19 pairs and elongated posteriorly in A. assimilis ; (4) Modified neurochaetae: with distal part becoming slightly thinner, a rounded tip and terminal and subterminal pubescence, bearing a very long arista and terminal hairs on the convex side of the tip in A. pseudoassimilis n. sp.; with distal part getting slightly thinner, a rounded tip, and pubescence only on the convex side of the terminal part, lacking arista and hairs on the tip in A. flava ; with distal part getting strongly thinner and bent upward, without pubescence, bearing a very long arista and terminal hairs on the convex side of the tip in A. laubieri ; with distal part getting slighlty thinner and with undulate tip (curved at nearly 90°), having terminal and subterminal pubescence, bearing long terminal hairs on the tip in A.assimilis .

Habitat and Distribution. This species was found in soft substrata between 10 and 100 m depths in the Sea of Marmara; between 11 and 70 m depths in the Levantine, Aegean, and Black Seas.

Etymology. The epithet pseudoassimilis was selected due to morphological and habitat similarity with Aricidea assimilis .

Figures

FIGURE 23. Aricidea (Acmira) pseudoassimilis n. sp. (Holotype, ESFM-POL/2013-1119). A, Dorsal view of anterior part of body; B, Hirsute limbat chaetae (type II, sigmoid with fibrlis along edge) of neuropodium of chaetiger 5; C, Hirsute limbat chaeta (type I, straight with fibrlis along edge) of notopodium of chaetiger 5; D, Modified neurochaeta of chaetiger 35; E, Modified neurochaeta of chaetiger 47. Scale bar: A, 500 µm; B, 80 µm; C, 102 µm; D, 47 µm; E, 44 µm.

FIGURE 24. Aricidea (Acmira) pseudoassimilis n. sp. (Paratype,ESFM-POL/2013-1125).A, Dorso-lateralview of prostomium; B, Cross section of chaetiger 2; C, Cross section of chaetiger 6. Scale bar: A, 200 µm; B, 118 µm; C, 234 µm.

FIGURE 25. Aricidea (Acmira) pseudoassimilis n. sp. A, Lateral view of anterior end, paratype (ESFM-POL/2013-1128); B, Lateral view of anterior end of a specimen from the Black Sea with amber-coloured modified neurochaetae and red speckles on dorsal side of body (ESFM-POL/2019-10); C, Lateral view of anterior end of a specimen from the Black Sea with ambercoloured modified neurochaetae and red speckles on dorsal side of body, stained with Shirlastain-A (ESFM-POL/2019-10); D, Dorso-lateral view of anterior end, paratype, stained with Shirlastain-A (ESFM-POL/2013-1125); E, Dorsal view of anterior end of a specimen from the Black Sea with amber coloration on dorsal side (ESFM-POL/2019-10); F,Amber-coloured modified neurochaetae and red speckles on a parapodium in posterior chaetiger of specimen from the Black Sea (ESFM-POL/2019- 10); G, Amber-coloured modified neurochaetae and red speckles in posterior chaetigers of the a specimen from the Black Sea (ESFM-POL/2019-10); H, Modified neurochaetae of chaetiger 37, holotype (ESFM-POL/2013-1119); I, Modified neurochaeta of chaetiger 58 of a specimen from the Black Sea (ESFM-POL/2019-10). Abbreviations: sf, skin fold; sr, short ridge. Scale bar: A, 750 µm; B, 1200 µm; C, 745 µm; D, 200 µm; E, 400 µm; F, 53 µm; G, 187 µm; H, 53 µm; I, 46 µm.

FIGURE 26. Aricidea (Acmira) pseudoassimilis n. sp. (Paratype, ESFM-POL/2013-1125). A, Dorsal view of anterior end; B, Dorsal view of anterior end; C, Ventral view of anterior end, with proboscis everted; D, Notopodium of branchial chaetiger with short dorsal ciliary band; E, Lateral view of prostomium with ciliary band; F, Lateral view of prostomium and anterior part of chaetiger 1. Abbreviations: clcb, crown-like ciliary band; cs, ciliary slits; dcb, dorsal ciliary band; no, nuchal organ; sdcb, second dorsal cililary band; sf, skin fold; sr, short ridge. Scale bar: A, 175 µm; B, 320 µm; C, 199 µm; D, 71 µm; E, 39 µm; F, 16 µm.

FIGURE 27. Aricidea (Acmira) pseudoassimilis n. sp. (Paratype, ESFM-POL/2013-1125). A, Dorsal view of prostomium; B, Antenna with dense cilia; C, Dorso-lateral view of anterior end; D, Crown-like ciliary band and ciliary slit from lateral side of prostomium; E, Cilia on crown-like ciliary band; F, Dorso-lateral view of anterior end with proboscis everted; G, Lateral view of mid-branchial region, interramal lobes. Abbreviations: bran, branchia; clcb, crown-like ciliary band; cs, ciliary slits; dcb, dorsal ciliary band; irl, interramal lobes; no, nuchal organ; ntpcl, notopodial postchaetal lobe; prob, proboscis. Scale bar: A, 80 µm; B, 26 µm; C, 66 µm; D, 20 µm; E, 1 µm; F, 138 µm; G, 91 µm.

FIGURE 28. Aricidea (Acmira) pseudoassimilis n. sp. (Paratype, ESFM-POL/2013-1125). A, Lateral view of mid-branchial chaetigers; B, Notopodial postchaetal lobe on chaetiger 1; C, Lateral sense organ on posterior chaetiger; D, Pore with cili on lateral sense organ from posterior chaetiger; E, Lateral sense organ of posterior chaetiger; F, Lateral sense organ of posterior chaetiger, arrows pointing irregular cilia on body; G, Modified neurochaetae on posterior chaetiger. Abbreviations: bran, branchia; irl, interramal lobe; lso, lateral sense organ; neupcl, neuropodial postchaetal lobe; ntpcl, notopodial postchaetal lobe. Scale bar: A, 73 µm; B, 21 µm; C, 11 µm; D, 1 µm; E, 14 µm; F, 5 µm; G, 28 µm.