Amphictene helenae, Garcia-Garza, Maria E. & de Leon-Gonzalez, J. A., 2014

Garcia-Garza, Maria E. & de Leon-Gonzalez, J. A., 2014, A new species of Amphictene (Annelida, Pectinariidae) from the Gulf of Mexico, with a redescription of Amphictene guatemalensis (Nilsson, 1928), ZooKeys 367, pp. 1-9 : 3-4

Amphictene helenae sp. n. Figure 2

Amphictene sp. A.Wolf, 1984: 50-4-6 fig. 50-1, 2 a-j.

Type material.

Holotype (UANL-7824); Paratype (LACM-AHF-Poly 5741) Bahamintas Beach, Ciudad del Carmen, Campeche, México, St. 2, [18°41'60"N, 91°41'00"W], 0.50 m deep, January 3, 2011, coll. ME García-Garza and JH Landín-Delgado.

Additional material.

Amphictene sp. A (USMN 86826) St. I-4, off Port O’Connor Texas [28°22'60"N, 96°47'60"W], STOCS expedition, 10 m deep, May 1976; (USMN 86827) St. M-21, off Texas [27°53'60"N, 97°21'60"W], IXTOC expedition, 10 m deep, December 1980; (USMN 86828) St. IV 2419, off Apalachicola river, Texas [30°18'00"N, 84°08'00"W], MAFLA expedition, 10 m deep, November 1977.

Description.

Holotype complete, 25.7 mm long, 5.3 mm wide, with 19 segments, body robust and soft, light brown in color. Cephalic veil formed by one semicircular lobe inserted at base of paleae, forming shelf on buccal tentacles. Rim of cephalic veil with 38 long, thin cirri; each cirrus with subtriangular base, tapering toward distal end; curved toward dorsum (Fig. 2A4). Operculum covered by numerous papilliform structures randomly distributed; nine pairs of long and slightly curved paleae, sharply pointed. Opercular margin with 19 subtriangular cirri (Fig. 2B).

First segment with two pairs of tentacular cirri: first pair inserted on antero-posterior margin of segment; second pair arising from posterior middle part of segment, below first pair. Second segment with one pair of tentacular cirri inserted on lateral margin of segment, larger than cirri of first segment (Fig. 2C). Second segment dorsally indistinguishable, aerolated; with 8 pairs of thin and subtriangular ventral glandular cirri, attenuated distally; one plate with numerous small papillae in central part segment. Third segment with one middle ventral lobe and one pair of shorter lateral expansions. Fourth segment with six glandular lobes, robust and subtriangular, fused in pairs (Fig. 2A). Two pairs of latero-ventral branchiae inserted on segments 3 and 4, forming series of flat and free lamellae, fused only at base, anterior pair larger than posterior one (Fig. 2C).

Chaetigers 1-3 (segments 5-7) only with notopodia. Chaetigers 4-15 biramous with notopodia and neuropodia. Capillary notochaetae on chaetigers 1-15, some small, thinner, with external margin slightly denticulate, others bent with smooth margin, distally thin, slightly hirsute; bayonet-shaped notochaetae appear on chaetigers 4-15, with well-developed middle tooth, blade serrated throughout (Fig. 2D). Neuropodia wedge-shaped, slightly glandular, torus with numerous uncini arranged in single row. Neuropodial uncini with a group of 6-7 small apical teeth randomly placed, and two longitudinal rows, each one consisting of 5-6 larger teeth, and small group of basal teeth with undefined arrangement, decreasing in size towards base (Fig. 2E-F).

Last three posterior segments, without noto- or neurochaetae, followed by five fused segments forming scaphe, clearly separated from abdomen, wider than longer, with 21 pairs of short and thick scaphodal hooks, golden in color, with brown margins (Fig. 2G). Five marginal lobes triangular-shaped, with one fold in antero-dorsal end, and margin somewhat crenulate; anal lobe with large anal papilla and three pairs of lateral papillae, in middle dorsal region (Fig. 2H).

Tube cone-shaped, made of cemented shell fragments of similar sizes, most of them clear, with few dark fragments (Fig. 2I).

Remarks.

Amphictene helenae sp. n., is similar to Amphictene guatemalensis (Nilsson, 1928) and Amphictene catharinensis (Grube, 1870) by having a glandular cirrus on the second segment and lobes on segment 4. Nevertheless, these species differ in some morphological characters: Amphictene helenae sp. n., has three pairs of tentacular cirri, two pairs on the first segment, and a pair in the second one, while Amphictene guatemalensis and Amphictene catharinensis have only one pair in the first segment and a pair in the second one; Amphictene helenae sp. n., has eight pairs of glandular cirri on the second segment, and six robust glandular lobes on the fourth segment, subtriangular, fused in pairs. Amphictene guatemalensis has six pairs of glandular cirri in the second segment, two pairs of glandular subtriangular lobes in the fourth segment. Amphictene catharinensis has17 or 18 glandular cirri on the second segment, in the fourth a central lobe with subtriangular lateral extensions and two pairs of free subtriangular broad lobes. Furthermore, Amphictene catharinensis and Amphictene helenae can be distinguished by the presence of a circular group of small glandular papillae between both lines of glandular cirri on the ventral side of the second segment, which is absent in Amphictene catharinensis .

Examination of the material described by Wolf (1984) as Amphictene sp. A, from Florida and Texas, USA, and deposited at the USNM, indicated that it belongs to this new species, however, the specimens were found to be in poor condition.

Type locality.

Bahamintas Beach, Ciudad del Carmen, Campeche, México.

Distribution.

Gulf of Mexico.

Etymology.

The species is named in honour of Helena Landín García, daughter of the first author.