Chaetacanthus ornatus, Salazar-Silva & López-Sánchez & Salazar-Vallejo, 2020

Salazar-Silva, Patricia, López-Sánchez, Daniel A. & Salazar-Vallejo, Sergio I., 2020, Revision of Chaetacanthus Seidler, 1922 (Annelida, Phyllodocida, Polynoidae), Zootaxa 4885 (3), pp. 395-422 : 407-411

Chaetacanthus ornatus n. sp.

urn:lsid:zoobank.org:act:8D720EB8-0DEE-4090-816F-1B22BDF989C3

Figures 10–12 , 13 A–C

Chaetacanthus magnificus: Monro 1928: 558 ; Hartman 1939a: 28–29 (non Grube, 1876).

Chaetacanthus cf. magnificus: Hernández-Moreno 2011: 28–32 , Fig. 9 A–O, Pls. 5D, 6F (non Grube, 1876).

Type material. Eastern Pacific. Holotype ECOSUR 233 , Puerto Escondido , Oaxaca, México, 10, associated with algae on thorny bivalve ( Spondylus Sowerby, 1847 ), 4 Jul. 2004, S. García, coll.

Diagnosis. Chaetacanthus with branchial filament digitiform with septate appearance; anterior eyes area bulky; elytral macrotubercles globular, amber-colour, sclerotized in large honeycomb like groups, outer area with fusiform macrotubercles distally blunt; numerous microtubercles dark, conical with thick spines on overlapping medially area.

Description. Holotype (ECOSUR 233) 2.9 cm long, 1.1 cm wide, 26 segments ( Fig. 10A ). Prostomium bilobed, facial tubercle small, round. Two pairs of dark eyes; anterior pair on widest prostomial bulky area; posterior pair near posterior prostomial margin; posterior eyes much smaller than anterior ones ( Fig. 10B ). Median antenna with thick, long ceratophore inserted frontally between prostomial lobes, style long, 1.5 times longer than prostomial length, thick, subdistally clavate, tip filiform, surface smooth, with pigmentation rings medially and subdistally. Lateral antennae with ceratophores inserted terminally on frontal prostomial border, brownish, styles similar in shape and pigmentation to median antenna. Palps robust, dark, taper into thin tips, surface with long rows of papillae. Pharynx everted with soft marginal papillae, 12 dorsally and 13 ventrally ( Figs 10A, B ; 11A, B ).

Tentacular segment not visible dorsally. Tentaculophores basally thick, inserted laterally to prostomium. Tentacular cirri with similar shape and pigmentation as median antenna. Segment two projected anteriorly over prostomium as a small round lobe ( Fig. 10B ). First pair of elytrophores long, not covering tentaculophores. Segment three narrower than successive segments.

All elytra with fringe of abundant, long papillae, and a bundle of long papillae in posterior inner margin ( Fig. 12 A–D). First pair of elytra with abundant hemispherical microtubercles along its surface, each with surface spinulose; globular macrotubercles arranged in a curved J-shaped row, smaller along posterior border ( Fig. 12A ) some pedunculated. From third segment, elytra bear globular macrotubercles with minute spines, mainly along posterior border, and sclerotized on central area forming a honeycomb patch ( Fig. 12 B–D). Towards dorsal midline, each elytron has dark microtubercles conical with thick peaks; fusiform macrotubercles long, thin, with short spines along their surface; along outer region numerous fusiform macrotubercles distally rounded.

Parapodia biramous; branchial filaments digitate, abundant, some appearing septate ( Fig. 10C ). Notopodia short with acicular tips emerging. Neuropodia distally truncate, acicular tips slightly projected. Elytrophores wide, dorsal tubercles inconspicuous. Dorsal cirri short, not reaching neurochaetal tips, distally clavate with cirrophores short, swollen. Ventral cirri thick, short with filiform tips. Nephridial papillae present from segment 11, cylindrical, long. Pygidium with two anal cirri, similar to dorsal cirri.

Notochaetae abundant, thin, short, as long as half neurochaetal length, tips filiform, surface with rows of denticles ( Fig. 10C ). Neurochaetae dark amber ( Fig. 10C ), thick, slightly curved, slender along first two segments ( Fig. 10C , inset), markedly larger and thicker thereafter; median segments with upper bundle with shorter chaetae, subdistally with scarce spines, tips entire.

Variation. Elytral variation will be better understood in a comparison between C. ornatus n. sp. and C. brasiliensis . Chaetacanthus ornatus has swollen macrotubercles and larger honeycomb-like groups than those present in C. brasiliensis . In first elytra, C. ornatus macrotubercles are about twice as large and mostly arranged in a single row ( Fig. 13A ), whereas in C. brasiliensis they are smaller, arranged in a row with 1–2 macrotubercles ( Fig. 13D ). By segment 9 in C. ornatus , the honeycomb groups are 3–4 times larger and occupy about ¼ elytral surface ( Fig. 13B ), whereas in C. brasiliensis they extend for about 1 / 6 of elytral surface and macrotubercles are smaller ( Fig. 13E ). In segment 24, the individual macrotubercles in C. ornatus have enlarged about 3–4 times more than in segment 9, and now they extend for about 1 / 3 elytral surface ( Fig. 13C ), whereas in C. brasiliensis the macrotubercles have doubled their size and expanded over elytra such that now they occupy about ¼ elytral surface ( Fig. 13F ).

Etymology. The specific epithet is derived from the Latin word ornatus (masculine), meaning furnished, equipped, adorned, or decorated, in reference to the large honeycomb group of macrotubercles on elytral surfaces.

Remarks. Members of Chaetacanthus ornatus n. sp. were compared with the type material of C. brasiliensis ; C. ornatus n. sp. differs because its dorsal cirri are short, the facial tubercle is short and round, not elongate. The globular tubercles present on first pair of elytra are similar in shape to those of middle and posterior elytra; each is globular with spinous surface. Further, C. ornatus differs from C brasiliensis because the macrotubercles of the central patch are not depressed and the patch is wider, covering a region larger than the elytrophoral plug. The long fusiform tubercles are distally blunt, without a sharp tip, and the microtubercles along the inner surface have thicker peaks.

Monro (1928) recorded C. magnificus from Coiba and Gorgona Islands, in the Eastern Pacific, and indicated his accounts were the first records for the Caribbean species into the Pacific Ocean. Monro materials were not examined, but they are regarded as conspecific with C. ornatus . Hartman (1939a) recorded C. magnificus for the Pacific with specimens from Ecuador, Panamá and México, The specimens from Socorro Island, Colima (sta. 132-34), and from Petatlan Bay, Guerrero (sta. 264-34) require corroboration, but might also belong to this new species.

Type locality. Puerto Escondido , Oaxaca, México .

Distribution. Puerto Escondido, Oaxaca, México; probably also present in Coiba, Panama; Isla Gorgona, Colombia.

Figures

FIGURE 9. Chaetacanthus harrisae n. sp., holotype (LACM 245). A. First elytron, dorsal view. B. Same, spiny microtubercles. C–E. Same, close up of spiny microtubercles. F. Elytron of middle segment, dorsal view. G. Globular central macrotubercles from first elytron. Scale bars: A, F: 1.1 mm; B, G: 0.1 mm; C: 0.3 mm; D, E: 0.01 mm.

FIGURE 10. Chaetacanthus ornatus n. sp., holotype (ECOSUR 233), fixed in formalin solution. A. Dorsal view, pharynx everted. B. Anterior end, dorsal view pharynx everted. C. Left parapodium, anterior view (inset: segment 3, neurochaetal tip). Scale bars: A: 2.8 mm; B: 0.2 mm; C: 0.06 mm.

FIGURE 11. Chaetacanthus ornatus n. sp., holotype (ECOSUR 233), fixed in formalin solution. A. Pharynx everted, left lateral view. B. Same, frontal view. Scale bars: A: 0.45 mm; B: 0.50 mm.

FIGURE 12. Chaetacanthus ornatus n. sp., holotype (ECOSUR 233), fixed in formaline, elytra in dorsal view. A. Left elytron from first pair. B. Left elytron of middle segment. C. Left elytron from middle segment. D. Left elytron, from posterior segment. Scale bars: A, B: 0.6 mm; C: 0.8 mm; D: 0.7 mm.

FIGURE 13. A–C. Chaetacanthus ornatus n. sp., holotype (ECOSUR 233) elytra in dorsal view. D–F. C. brasiliensis, nontype specimen (ECOSUR P 3100) elytra; A, D. Elytra of first pair. B, E. Right elytra of middle segment. C, F. Right elytron of posterior segment. Scale bars: A, B: 0.6 mm; C, D: 0.7 mm; E: 1.4 mm; F: 2 mm.