Trophoniella enigmatica, SALAzAR-Vallejo, 2012

SALAzAR-Vallejo, Sergio I., 2012, Revision of Trophoniella Hartman, 1959 (Polychaeta, Flabelligeridae), Zoosystema 34 (3), pp. 453-519 : 453-519

Trophoniella enigmatica n. sp.

( Fig. 9 )

Stylarioides eruca – Fauvel 1934: 49 (non Claparède 1869).

T YPE MATERIAL. — Mediterranean Sea, Adriatic Sea. Holotype ♀ ( MNHN A457 ), off Rovigno, Croatia, stn 83 (no further data), A. Vatova.

ADDITIONAL MATERIAL. — Eastern Atlantic. 1 specimen ( MNHN 457 ), complete, Concarneau, France, 23.V.1923, P. Fauvel (39 mm long, 2.5 mm wide, cephalic cage 5 mm long, 68 chaetigers; 6 - 7 notochaetae per bundle in median chaetigers; first anchylosed neurohooks in chaetiger 25; all neurohooks anchylosed from chaetiger 55). — 2 specimens ( MNHN 508 ), anterior fragments, R/ V Andrée 1922 expedition, stn 8, off Bretagne, France, M. Monod .

Adriatic Sea. 1 specimen ( ECOSUR), stn SJ7 (45°17’N, 13°16’E), 31 m, silty sand, 27.II.2003, B. Mikac, without posterior end, blackish anterior region extending for chaetigers 1 and 2 ; 1 specimen ( ECOSUR), same data, but 18.XII.2003, anterior fragment, head with 10 branchial filaments, palps lost ; 1 specimen ( ECOSUR), same data, but 28.V.2003, mature ♀, without posterior end, broken in 3 pieces, oocytes 150-175 µm in diameter ; 1 specimen ( ECOSUR), same data, but 29.I.2004, anterior fragment, anterior end blackish extending for 5 or 6 chaetigers .

TYPE LOCALITY. — Off Rovinj, Croatia ( Herzegovina), in shallow water.

DISTRIBUTION. — Apparently disjunt, living in the Atlantic western coast of France and in the upper Adriatic Sea, in shallow water.

ETYMOLOGY. — The specific name derives from the Latin word “enigma”, meaning enigma, puzzle, or mystery. It is used as an adjective to indicate the unexpected branchial features, which differ from all other species in the genus. DESCRIPTION

Holotype (MNHN A457) a mature female, posteriorly incomplete, breaking in two parts, many chaetae broken ( Fig. 9A ). Body subcylindrical, tapering posteriorly, 36 mm long, 4 mm wide, cephalic cage 5 mm long, 49 chaetigers. Tunic dorsally and ventrally covered by large sediment grains, not immersed in the tunic (only sand grains, no forams or molluscs shell fragments). Papillae long, capitate, sparse, arranged in longitudinal rows, three dorsally, four ventrally, difficult to detect because of the size and colour of the adherent particles.

Anterior end observed by dissection. Cephalic hood short, margin finely papillated. Prostomium low cone, eyes large, dark; caruncle poorly developed, not reaching the branchial plate posterior margin ( Fig. 9A , insert). Palps large, corrugated; palp keels low, rounded. Branchiae cirriform, thick, arranged as a continuous row with 10 filaments, some branchiae as long as palps. Nephridial lobes placed between the branchial row and the prostomium, short, rounded.

Cephalic cage chaetae about 5⁄₄ as long as body width, arranged in short transverse series. Chaetigers 1 - 2 involved in the cephalic cage; 5 - 6 noto- and 6 - 7 neurochaetae per side. Anterior margin of chaetiger 1 with a cirriform lobe, partially eroded ( Fig. 9B ); anterior chaetigers with small dorsal tubercles and one elongated postchaetal papillae, larger in notopodia. Dorsal tubercles low, in chaetigers 2 - 9.

Chaetigers 1 - 3 of about the same length. Chaetal transition from cephalic cage to body chaetae gradual; multiarticulate neurohooks from chaetiger 2,decreasing in size to chaetiger 5. Falcate anchylosed hooks from chaetiger 40. Gonopodial lobes not seen ( Fig. 9C ).

Parapodia well developed, placed on the body corners. Median neuropodia ventrolateral. Notopodia elongate, lobate, with a single large, capitate postchaetal papilla.

Median notochaetae arranged in short transverse series, 7 - 8 per bundle, as long as ½ body width; all notochaetae multiarticulated capillaries, short articles basally, medium-sized medially, long distally ( Fig. 9D ). Neurochaetae multiarticulated capillaries in chaetiger 1, from chaetiger 2 multiarticulated bidentate neurohooks, shorter neurohooks appear by chaetiger 5. From chaetiger 40, falcate bidentate anchylosed neurohooks. By chaetiger 48, two out of five neurohooks anchylosed ( Fig. 9E ). Multiarticulate neurohooks arranged in short transverse series, 5 - 6 in anterior chaetigers, 4 - 5 in posterior ones; each with short anchylosed articles basally, long medially, medium-sized distally. Distal piece with fang curved, bidentate, accessory tooth reaching fang’s tip, leaving a wide inner area ( Fig. 9E , insert). Anchylosed neurohooks with short rings, continued to the subdistal slightly expanded region, blade unpigmented, bidentate, fang curved, accessory tooth straight, often eroded.

Posterior end unknown. Oocytes dark, about 150-175 µm in diameter.

REMARKS

Trophoniella enigmatica n. sp. has been included in this genus because most of its morphological features fit the generic diagnosis. There is one discrepancy, however, and it relates to the branchial plate; in most species of the genus, the branchial plate is tongue-shaped with thin, abundant filaments separated in two lateral groups by a posteriorly prolonged caruncle. In T. enigmatica n. sp. the branchial plate is barely projected and there are instead 10 thick filaments, arranged in a single row, and the caruncle is reduced, not reaching the branchial plate’s posterior margin. Nevertheless, the relative tunic development and especially the chaetal pattern, because this species has anchylosed neurochaetae in posterior chaetigers, indicates it must be placed in Trophoniella .

Besides the above differences, T. enigmatica n. sp. is more closely related to T. indica n. comb., n. stat., from the Indian Ocean. The main differences between them, besides the branchial features, are the relative start of anchylosed neurohooks, and the size relationships between the fang and accessory tooth; thus, in T. enigmatica n. sp. these neurohooks start by chaetiger 40, whereas they start by chaetiger 14 in T. indica n. comb., n. stat. and the accessory tooth is as long as fang in T. enigmatica n. sp., whereas it is longer than fang in T. indica n. comb., n. stat.

Several specimens were also recorded from the same region as the holotype, in stations 9, 17, 38, 41, 43, 83, 95, 98, 109, 123. Some of them might be kept in the Museo di Zoologia, Centro di Ateneo per i Musei, Università degli Studi di Padova, Italia (http://www.unipd.it/musei/zoologia/collezioni/ rovigno.html). Regretfully, they were not available, such that there is no way to precise which belong to the same species.

Figures

FIG. 9. — Trophoniella enigmatica n. sp.,holotype (MNHN A457):A, dorsal view (insert:dissected head,branchiae and palps removed); B, anterior end,dorsal view; C, anterior end,ventral view;D, chaetiger 13,basal,medial and distal notochaetal regions; E, chaetiger 48, neurohooks (insert: tip of anchylosed neurohook). Scale bars: A, 2 mm; B, C, 1 mm; D, 50 µm; E, 110 µm.