Mariansabellaria caribbea sp. nov.

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Figs 3–4

Diagnosis

More than 50 pairs of outer paleae per lobe. Outer paleae with irregularly expanded margins resembling small denticles. Four to five inner paleae per lobe. Inner paleae with conspicuous transverse thecae and slightly curved tip. Three pairs of buccal tentacles.

Etymology

The species name is referred to the Caribbean Sea, where the species was found.

Material examined

Holotype MEXICO • complete spec. (body length 10 mm); Quintana Roo, East of the Center Cay, Banco Chinchorro; RV Edwin Link, stn. 2782; 18°34.41′ N, 87°26.80′ W; depth 274 m; 23 Aug. 1990; ECOSUR-303.

Description

BODY. Holotype complete (ECOSUR-303), integument slightly eroded. Body light brown, 10 mm long, 2.5 mm wide, fourth parathoracic segments, 12 abdominal segments, caudal peduncle 5 mm long (Fig. 3).

OPERCULUM. Opercular disc truncates, two rows of translucent, amber paleae: outer row with 54–56 paleae on each lobe, inner row with 4–5 paleae on each lobe (Fig. 3A, C). Outer paleae cylindrical, 2 mm long (Fig. 4A). Proximal region with compact thecae partially surrounding the blade, margins slightly expanded, denticulate (Fig. 4B, E). Middle region with thecae partially surrounding the blade, margins expanded, pectinate (Fig. 4C). Tip pinnate (Fig. 4D). Inner paleae cylindrical, finely tapering, with conspicuous thecae partially surrounding subdistal margins and slightly curved, smooth tip (Fig. 4F– H). Opercular stalk light brown, twice as long as wide (Fig. 3A). Seven opercular papillae on right lobe, three papillae on left; fragile, easily detachable tissue. Three pairs of tentacles, simple, grooved (Fig. 3C). Nuchal spines cylindrical, embedded in opercular tissue; two on left lobe and three in right one (Fig. 3D). Median ridge short, with some marginal eyespots. Median organ absent.

THORAX. First thoracic segment with long, triangular-shaped lateral lobe and capillary neurochaetae. Second chaetiger with short, triangular-shaped lateral lobe, without chaetae (Fig. 3E).

PARATHORAX. With four segments, body wall eroded, branchiae translucent, fragile (Fig. 3E). Pigmented tissue, in dorsal view, with seven reddish transverse lines (Fig. 3A). Notopodia with lanceolate and capillary chaetae (Fig. 4I). Neuropodia with only capillary chaetae.

ABDOMEN. Abdominal region bent, body wall damaged, branchiae translucent, fragile, present only in first four segments. Abdominal segments colorless. Neurochaetae capillary, ornamented with irregular thecal laminar extensions (Fig. 4J–K). Notopodia with series of uncini with 9–10 transverse rows of teeth (Fig. 4L). Caudal peduncle whitish, slightly annulate (Fig. 3F).

Remarks

Mariansabellaria caribbea sp. nov. shares the presence of transverse margins on the inner paleae with M. chilena, M. tenhovei, and M. norvegica, and the outer paleae with thecae that do not surround the blade, also called ‘hemithecae’ by Kirtley (1994) for M. chilena . However, M. tenhovei, M. chilena and M. caribbea sp. nov. differ in the number of buccal tentacles. Kirtley (1994) described M. tenhovei with five pairs of buccal tentacles and M. chilena with six pairs, while M. caribbea sp. nov. only has three pairs.

Mariansabellaria caribbea sp. nov. is characterized by having more than 50 pairs of outer paleae with irregularly expanded margins resembling small denticles, 4–5 inner paleae, and only three pairs of buccal tentacles. Although the outer paleae of M. norvegica also have irregular margins resembling denticles, Strömgren (1971) did not describe the number of opercular paleae. However, the two species differ in the morphology of the thecae of the outer paleae, and in the number of teeth on the abdominal uncini, seven pairs in M. norvegica and 9–10 pairs in M. caribbea sp. nov.

Kirtley (1994) only provided the number of opercular paleae for M. harrisae, with 24 pairs of outer and 10 pairs of inner paleae. In addition to the difference in the number of opercular paleae, M. harrisae has smooth inner paleae and five buccal tentacles per lobe, while M. caribbea sp. nov. has inner paleae with conspicuous thecae and three tentacles.

Distribution

Banco Chinchorro, Quintana Roo, at 274 m depth. This is the first record of the genus Mariansabellaria in the western Atlantic (Fig. 22).