Aricidea (Acmira) assimilis Tebble 1959
Creators: name: Erdoğan-Dereli, Deniz
name: Çinar, Melih Ertan
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Annelida
Polychaeta
Paraonidae
Aricidea
Aricidea assimilis

description: Aricidea (Acmira) assimilis Tebble, 1959
(Figures 4–6)
Aricidea assimilis Tebble 1959: 25–27, Figure 4.
Aricidea (Acmira) asimilis: Strelzov 1979: 108–110, fig. 39; Jung et al. 1996: 319–320, 329, fig. 7A–G; Lovell 2002: 44–45, fig. 6A–D; Aguirrezabalaga 2012: 167–168, fig. 58.
Aricidea mutabilis Laubier & Ramos 1974: 195–199, fig. 7 (in part).
Material examined. ESFM-POL/2013-42, 06 June 2013, station Y1, 40°00’27’’N, 26°13’24’’E, 10 m, mud, 2 specimens; ESFM-POL/2013-44, 06 June 2013, station Y1, 40°00’32’’N, 26°13’04’’E, 25 m, mud, 2 specimens; ESFM-POL/2013-52, 06 June 2013, station Y2, 40°06’28’’N, 26°22’51’’E, 10 m, mud with shell fragments, 3 specimens; ESFM-POL/2013-1350, 06 June 2013, station Y2, 40°06’59’’N, 26°22’04’’E, 50 m, muddy sand, 3 specimens, ESFM-POL/2013-68, 06 June 2013, station Y3, 40°12’03’’N, 26°26’21’’E, 10 m, mud with shell fragments, 5 specimens; ESFM-POL/2013-73, 06 June 2013, station Y3, 40°12’15’’N, 26°26’12’’E, 25 m, mud, 1 specimen; ESFM-POL/2013-77, 06 June 2013, station Y3, 40°13’10’’N, 26°25’45’’E, 50 m, sand, 8 specimens; ESFM-POL/2013-88, 07 June 2013, station Y5, 40°20’56’’N, 26°40’51’’E, 10 m, mud, 2 specimens; ESFM-POL/2013-1352, 07 June 2013, station Y5, 40°21’21’’N, 26°39’59’’E, 50 m, mud, 2 specimens; ESFM-POL/2013- 1190, 07 June 2013, station Y6, 40°26’10’’N, 26°41’51’’E, 10 m, mud, 4 specimens; ESFM-POL/2013-1354, 07 June 2013, station Y6, 40°26’03’’N, 26°41’59’’E, 25 m, mud, 1 specimen; ESFM-POL/2013-1191, 07 June 2013, station Y7, 40°24’28’’N, 26°51’24’’E, 25 m, maerl bed, 6 specimens; ESFM-POL/2013-1192, 07 June 2013, station Y8, 40°25’15’’N, 27°03’49’’E, 10 m, mud, 6 specimens; ESFM-POL/2013-1194, 07 June 2013, station Y8, 40°25’27’’N, 27°03’34’’E, 25 m, mud, 2 specimens; ESFM-POL/2013-1197, 08 June 2013, station Y9, 40°26’25’’N, 27°11’29’’E, 25 m, mud, 1 specimen; ESFM-POL/2013-1195, 08 June 2013, station Y9, 40°28’09’’N, 27°11’14’’E, 50 m, mud, 3 specimens; ESFM-POL/2013-1202, 07 June 2013, station Y10, 40°31’28’’N, 26°54’12’’E, 10 m, sand, 1 specimen; ESFM-POL/2013-1198, 07 June 2013, station Y10, 40°30’38’’N, 26°54’58’’E, 25 m, maerl bed, 4 specimens; ESFM-POL/2013-1200, 07 June 2013, station Y10, 40°28’24’’N, 26°57’30’’E, 50 m, maerl bed, 2 specimens; ESFM-POL/2013-1203, 08 June 2013, station Y11, 40°36’12’’N, 27°05’20’’E, 10 m, mud, 3 specimens; ESFM-POL/2013-1205, 08 June 2013, station Y12, 40°40’38’’N, 27°16’25’’E, 10 m, sand, 6 specimens; ESFM-POL/2013-1207, 08 June 2013, station Y12, 40°40’23’’N, 27°16’31’’E, 25 m, mud, 1 specimen; ESFM-POL/2013- 1208, 10 June 2013, station Y13, 40°45’27’’N, 27°21’24’’E, 100 m, mud, 1 specimen; ESFM-POL/2013-1209, 08 June 2013, station Y14, 40°24’03’’N, 27°19’23’’E, 10 m, sandy mud with shell fragments, 2 specimens; ESFM-POL/2013-1210, 08 June 2013, station Y15, 40°19’11’’N, 27°33’51’’E, 10 m, sandy mud, 10 specimens; ESFM-POL/2013-1212, 09 June 2013, station Y17, 40°39’58’’N, 27°41’08’’E, 50 m, mud, 4 specimens; ESFM-POL/2013- 1213, 10 June 2013, station Y18, 40°54’28’’N, 27°33’24’’E, 100 m, mud with shell fragments, 28 specimens; ESFM-POL/2013-1216, 12 June 2013, station Y19, 40°59’52’’N, 27°41’59’’E, 10 m, maerl bed, 2 specimens; ESFM-POL/2013-1217, 12 June 2013, station Y19, 40°58’36’’N, 27°42’29’’E, 25 m, maerl bed, 1 specimen; ESFM-POL/2013-1218, 12 June 2013, station Y19, 40°56’10’’N, 27°44’16’’E, 100 m, sandy mud with shell fragments, 22 specimens; ESFM-POL/2013-1220, 12 June 2013, station Y20, 40°57’09’’N, 27°54’46’’E, 50 m, mud with shell fragments, 1 specimen; ESFM-POL/2013-1221, 16 June 2013, station Y22, 40°23’22’’N, 27°59’46’’E, 50 m, mud, 59 specimens; ESFM-POL/2013-1224, 16 June 2013, station Y24, 41°03’08’’N, 28°08’44’’E, 25 m, maerl bed, 18 specimens; ESFM-POL/2013-1227, 16 June 2013, station Y24, 41°00’16’’N, 28°07’50’’E, 50 m, mudy sand with shell fragment, 16 specimens; ESFM-POL/2013-1229, 15 June 2013, station Y24, 40°57’20’’N, 28°07’21’’E, 100 m, mudy sand with shell fragment, 37 specimens; ESFM-POL/2013-1233, 16 June 2013, station Y25, 40°24’48’’N, 28°20’41’’E, 25 m, sandy mud with Amphiura filiformis, 8 specimens; ESFM-POL/2013-1236, 16 June 2013, station Y26, 40°22’36’’N, 28°39’41’’E, 25 m, sand with mudy shell fragments, 2 specimens; ESFM-POL/2013-1237, 16 June 2013, station Y26, 40°24’30’’N, 28°38’50’’E, 50 m, sandy mud, 2 specimens; ESFM-POL/2013-1238, 17 June 2013, station Y28, 40°29’15’’N, 28°51’09’’E, 50 m, sandy mud, 7 specimens; ESFM-POL/2013-1239, 17 June 2013, station Y29 40°32’39’’N, 28°46’42’’E, 50 m, mudy sand, 3 specimens; ESFM-POL/2013-1241, 17 June 2013, station Y29, 40°33’32’’N, 28°44’58’’E, 100 m, muddy sand, 20 specimens; ESFM-POL/2013-1244, 17 June 2013, station Y29, 40°34’01’’N, 28°44’45’’E, 200 m, mudy sand with shell fragments, 4 specimens; ESFM-POL/2013-1245, 14 June 2013, station Y31, 41°01’25’’N, 28°26’23’’E, 25 m, maerl bed, 39 specimens; ESFM-POL/2013-1247, 14 June 2013, station Y31, 40°56’40’’N, 28°25’15’’E, 100 m, sandy mud with shell fragments, 2 specimens; ESFM-POL/2013-1248, 23 June 2013, station Y32, 41°00’28’’N, 28°34’27’’E, 10 m, mud, 45 specimens; ESFM-POL/2013-1251, 24 June 2013, 40°54’50’’N, 28°52’12’’E, station Y 34, 100 m, sandy mud with shell fragments, 5 specimens; ESFM-POL/2013-1253, 20 June 2016, station Y43, 40°41’32’’N, 29°35’34’’E, 25 m, mud, 5 specimens.
Description. Largest specimen incomplete, 17.33 mm long, 0.5 mm wide, with 108 chaetigers. Color in alcohol usually light yellow. Body thick, dorsal side of anterior part slightly swollen, posterior part thick and cylindrical (Fig. 4A); red speckles present between notopodia and neuropodia along body of specimens with gametes (Fig. 4F).
Prostomium triangular, longer than wide (ratio length / width: 1.2); anterior margin rounded (Figs 4 A–B; 5A; 6D); without eyes.A crown-like ciliary band (clcb), present on posterior part of nuchal organs, complete except for a gap in dorsal side (Figs 5A; 6D). A pair of C-shaped ciliary slits (cs) located on lateral part of prostomium at level of antenna, with flexible cilia distinctly protruding from pore (Fig. 6D). Antenna long, almost three times longer than length of prostomium, reaching up to chaetiger 6, slender, tapering, with a central insertion and cilia (Figs 4 A–B; 5A–B). A pair of nuchal organs as deep, long slits placed on dorso-lateral side of posterior prostomium, more or less convex in shape; dense internal ciliation present, cilia not reaching outer margin of slits; without pigmentation (Fig. 6D). Mouth with three buccal lips; two placed anteriorly, one posteriorly and extending to anterior margin of chaetiger 1, with nine longitudinal folds; a Y-shaped gap present between anterior lips.
A dense dorsal ciliary band (dcb) present on mid-dorsal transversal line of each prebranchial and branchial chaetiger. A short dorsal ciliary band (sdcb) present, associated with base of each branchia (Fig. 6 A–C). Ciliary bands absent on ventral side of body.
Branchiae 20 pairs, starting from chaetiger 4; each, cylindro-conical and slighlty flattened; becoming longer to posterior parts along body; tips elongated with rounded tips in last 5–6 branchial chaetigers; dense ciliary bands on both sides of branchiae (Fig. 6 A–B), 376 μm long in anterior region, 484 μm in middle region and 591 μm in posterior region. Interramal lobes absent (Fig. 5C).
Notopodial papilla absent. Notopodial postchaetal lobes short, cirriform on first two chaetigers; long, thick, digitiform, with a distinct basal swelling between chaetigers 3–16 (Figs 5C, D; 6C); filiform on posterior chaetigers (Fig. 4F). Neuropodial postchaetal lobes absent (Figs 4B; 5C). Ventral lobes absent.
Three main types of chaetae present in chaetigers; limbate, capillary and modified neurochaetae.Limbate chaetae on both notopodia and neuropodia of chaetigers 1–20, long, thin and straight with fibrils along edge (hirsute), light rose colored; in notopodia, numbering 40–42 arranged in three rows, 272–313 µm long, positioning ventral to dorsal in fascicle; in neuropodia, numbering 47–50 arranged in 3–4 rows, 286–336 µm long, positioning dorsal to ventral in fascicle (Fig. 5A, C, D).
Capillary chaetae starting in noto- and neuropodia of chaetiger 21 and present in all subsequent chaetigers; in middle notopodia numbering 19–21, arranged in two rows, ca. 436 μm long; in posterior notopodia numbering 10–12, arranged in one row, ca. 169 μm long; in middle neuropodia numbering 10–12, arranged in 2–3 rows and ca. 231 μm long; in posterior neuropodia numbering 4–5, arranged in one row, ca. 267 μm long.
Modified neuropodial chaetae present from chaetiger 32 to pygidium, numbering 12–13 in each neuropodium; superior chaetae much longer and more curved; distal part abruptly bending almost at 90°, with a pointed tip; with 3–4 long fibrils on convex side of terminal region; pubescence on convex side of subterminal region (Figs 4C, E; 5E).
Pygidium missing.
Reproduction. Eggs were present in some specimens of Aricidea assimilis collected from the Sea of Marmara. They usually first occurred at chaetiger 34 and continued to the posterior end, and numbered 2–4 in each chaetiger (Fig. 4A, D). The egg diameter varied between 170 and 380 μm. The gamete bearing specimens had distinct reddish speckles between notopodia and neuropodia along the body (Fig. 4F).
Remarks. The specimens of A. assimilis from the Sea of Marmara are very similar to the original description of the species from Israel (Tebble 1959). The specimens from the Israeli coast have a relatively longer antenna, reaching to chaetiger 6–13, whereas the antenna of our specimens only extends to chaetiger 4 or 5, although the shape of the antenna is identical in the two regions. However, one should keep in mind that the tip of the antenna is very fragile in this species and often broken off, potentially causing a mistake in the estimation of its length.
Based on the length of the antenna and branchiae of the specimens A. mutabilis (a junior synonym of A. assimilis) found in the Gulf of Rosas (France, Mediterranean), Laubier and Ramos (1974) identified two groups within this species. Group 1 encompassed the specimens with a long antenna and bearing long posterior branchiae with pointed tip, and group 2 that included the specimens with a short antenna and short posterior branchiae without pointed tip. They observed that only the larger specimens had a longer antenna and longer posterior branchiae, and concluded that this character could be an ontogenetic modification. In this work, we demonstrate that the specimens falling into the group 2 infact belong to a new species described below.
The notopodial postchaetal lobes of A. assimilis have remarkable asymmetrical basal swellings (i.e. swelling present only one side of lobe) in the branchial region (Fig. 5 C–D). Since this structure is located latero-ventrally, it is quite difficult to notice it during the examination of specimens from the dorsal side. According to our observations, symmetrical (i.e. swelling present both sides of lobe) or asymmetrical swellings at the base of the notopodial postchaetal lobes in the branchial region are quite common in Aricidea species. For example, A. wassi and A. katzmanni n. sp. have symmetrical swellings in the base of the notopodial postchaetal lobes (Figs 17A; 20A; 36 C–D; 37B; 38A–B, E), whereas A. assimilis, A. pseudoarticulata n. sp. had an asymmetrical swelling (Figs 5 C–D; 28A). In contrast, A. simonae and A. cerrutii do not have any swelling in the base of the notopodial postchaeta lobes (Figs 12A; 13F; 15 B–C).
Some specimens from the Sea of Marmara had gametes in their coelomic cavities. In contrast to the inmature specimens, these ones have remarkable reddish speckles located between notopodia and neuropodia along the body (Fig. 4F). This character is not unique for A. assimilis, we observed such reddish speckles in the ripe specimens of the most of the Aricidea species found in the studied area (Figs 4F; 7C; 19I; 25B, C, E–G). In addition, such coloration was also noted in the ripe specimens of Paraonis fulgens from the Levantine Sea (Erdoğan-Dereli & Çinar 2020). It seems that this is a common shared character in the genera Aricidea and Paraonis.
Habitat and Distribution. Aricidea assimilis was found in different types of soft substrata (sandy mud, maerl beds, etc.) at depths ranging from 10 and 200 m in the Sea of Marmara. It was previously reported from similar habitats between 0 and 1155 m depths in the Pacific Ocean (Jung et al. 1996; León-González et al. 2006), eastern Atlantic Ocean (Gil & Sardá 1999; Aguirrezabalaga 2012) and eastern (Tebble 1959; Çinar et al. 2014) and western Mediterranean Sea (Laubier & Ramos 1974).
description: Published as part of 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, pp. 1-73 in Zootaxa 4844 (1) on pages 8-13, DOI: 10.11646/zootaxa.4844.1.1, http://zenodo.org/record/4405867