Trophoniella radesiensis, Chaibi & Antit & Bouhedi & Meca & Gillet & Azzouna & Martin, 2019

Chaibi, Marwa, Antit, Mouna, Bouhedi, Marwa, Meca, Miguel A., Gillet, Patrick, Azzouna, Atf & Martin, Daniel, 2019, A new species of Flabelligeridae (Annelida), Trophoniella radesiensis n. sp., from Tunisia, Zootaxa 4571 (4), pp. 551-561 : 554-556

Trophoniella radesiensis n. sp. Chaibi and Gillet

Figures 3–6

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Material examined. Holotype: MNCN16.01 /18453, collected on 25 Nov 2015 in Radés Station , Gulf of Tunis (15°55′ N, 97°41′ W) by the first author . Paratypes: MNCN 16.01 /18454. 6 specimens, same data as for holotype ; UCO T FLA 025.1specimen, same data as for holotype .

Diagnosis. Body covered by sediments of different grain size (50–1000 µm of long axe) embedded on tunic, completely concealed except in posterior region. Tunic pale, dorsally smooth, ventrally rough, with large papillae, carrying sediment grains and particles. Body papillae arranged in two dorsal and four ventral rows. Branchial plate tongue-shaped. Unidentate anchylosed neurohooks from chaetiger 20.

Description. Holotype with some chaetae broken, non-reproductive adult, unknown sex. 35 mm long, 4 mm wide, with 60 chaetigers; paratypes varying from 30–43 mm long and 1–4 mm wide for 43–74 chaetigers ( Fig. 3 A– E). Anterior body sub-cylindrical in cross-section, tapering towards pygidium. Tunic transparent, dorsally smooth, ventrally rough with large papillae, carrying sediment grains and particles with long axes ranging from 50 to 1000 µm, totally embedded in tunic, completely concealing it dorsally and ventrally, absent in posterior region. Pale brown, slightly reddish anteriorly. Cephalic cage 12 mm long, with chaetae ca. 1.5 times longer than body width, formed by chaetigers 1–5; chaetiger 2 dorsolateral, chaetiger 3–4 lateral. Chaetal transition from cephalic cage to body chaetae gradual ( Fig. 3A, 3 C–E). Body papillae similar in colour to body wall, mostly eroded, arising in two dorsal and four ventral longitudinal rows from first chaetiger to posterior end, better preserved anterior-most body region ( Fig. 3A, 3 C–E). Parapodia well developed. Noto and neuropodia have four prechaetal papillae and five postchaetal papillae ( Fig. 3C ). Especially long papillae absent from anterior chaetigers. Gonopodial papillae not seen. Chaetiger 1 with about six notochaetae and eight neurochaetae; anterior dorsal margin with dorsal papillae, arising as a multifid cephalic veil ( Fig. 4A ). Chaetiger 5 widening posteriorly. Cephalic hood not exposed. Caruncle short and triangular ( Fig. 4C, 4D ). Branchiae cirriform, arising from tongue-shaped branchial plate, arranged in two lateral lobes ( Fig. 4A, 4D ), thin, long (0.5–3mm), whitish once preserved in ethanol, with ca. 60 filaments. Palp, long, corrugated, pale, as long as largest branchiae, 6 mm long ( Fig. 4B, 4C ). Prostomium lowcone, with two large and two small black eyes ( Fig. 3D, 3E ). Lateral lip expanded; dorsal and ventral lips not well developed ( Fig. 3D, 3E ). Notochaetae all multiarticulated capillaries; articles progressively longer towards falcate tips; medial ones in short longitudinal series, 4–7 per bundle; some yellowish some dark brown; unidentate tips ( Fig. 5 A–5D). Multiarticulated capillary neurochaeta from chaetiger 2 to 5, then short unidentate neurohooks from chaetiger 6 to 19 ( Fig. 6A ) and anchylosed hooks from chaetiger 20 to body end ( Fig. 6B ), darker than preceding ones, arranged in transverse series of 4–6 units per bundle, similarly wide along their length, subdistally not or slightly expanded, with short rings continued up to a subdistal, non-annulated hyaline region, hooked, tapering to roughly pointed, unidentate tips ( Fig. 5A , 6B ). Pygidium simple, with single anal cirrus. No intra-specific variability in morphological characters was observed, except for lacking sediment gains in some specimens.

Distribution. Known only from the type locality, Radés Station (Gulf of Tunisia, Mediterranean Sea). Collected from both soft and rocky bottoms, from 3–4 m to 10 m depth. Etymology. The species name radesiensis refers to the type locality, Radés Station.

Figures

FIGURE 3. Trophoniella radesiensis n. sp. A. Lateral view. B. Mid body region showing the attached sand grains, lateral view. C. Anterior region, lateral view. D. Anterior region, dorsal view. E. Anterior region, ventral view. A, C–D: Holotype MNCN 16.01/18453; B: Paratype MNCN 16.01/18454.

FIGURE 4. Trophoniella radesiensis n. sp., stained with methyl blue. A. Detail of the anterior end, ventral view, prostomium non-everted, showing the tips of the branchial plates, the position of the first four chaetigers (1 to 4) and the crenulated cephalic veil (white arrow). B. Palps of a dissected specimen, dorsal view, surrounded by branchiae. C. Whole ventral view of the anterior region of a dissected specimen. D. Detail of C indicate the relevant characters. BP: branchial plates; CA: caruncle; E: eyes; LL: lateral lips; PS: palp scars; Pr: prostomium. A: Holotype MNCN16.01/18453; B–E: Paratype MNCN16.01/18454.

FIGURE 5. Trophoniella radesiensis n. sp. A: Notopodium of chaetiger 16 (with two broken notochaetae). B–D. Notochaetae. Tip. C. Median region. D. Basal region. A–D: Paratype MNCN16.01/18454.

FIGURE 6. Trophoniella radesiensis n. sp. A. Neuropodium of chaetiger 15. A1, A2, A5. Detail of tips from three short neurochaetal hooks of chaetiger 15. B. Neuropodium of chaetiger 30. B1, B2, B3. Detail of tips from three anchylosed neurochaetal hooks of chaetiger 30. A–B: Paratype MNCN16.01/18454.