Chaetacanthus pilosus (Treadwell, 1937)

Figures 14–16

Lepidonotus pilosus Treadwell, 1937: 141–143, Pl. 1, Figs. 1–7.

Lepidonotus pomareae panamensis Hartman, 1939a: 44–46, Pl. 6, Figs. 70–77 (partim).

Lepidonotus panamensis: Hartman 1948: 28 (n. status, partim).

Chaetacanthus magnificus: Salazar-Vallejo et al. 1990: 215, Fig. 37 (non Grube, 1876).

Chaetacanthus pilosus: Salazar-Silva 2006: 146 (reinst.).

Type material. Eastern Pacific. Holotype of Lepidonotus pilosus Treadwell, 1937, AMNH 3531, Arena Bank, Gulf of California, Sta. 136, D-13 (23°29’ N 109° 24’ W), 20 Apr. 1936. Holotype of Lepidonotus pomareae panamensis Hartman, 1939a, LACM 3, AHF-5, Poly 0039, Bahía Honda, Panama, off North Island, R / V Velero III, Sta. 863- 38, 54–90 m, 1 Mar.1938.

Additional material. Eastern Pacific, Panama. One specimen, LACM 863-38, off Bahía Honda, 54–90 m, rock sand mud, R/ V Velero, Sta. 863-38, 07°45’35” N, 81°35’35” W, 26 Jan. 1939, identified as Lepidonotus pomareae panamensis but separated from holotype.

Diagnosis. Chaetacanthus with branchial filaments digitiform, bifurcated; elytra with abundant pedunculated macrotubercles and microtubercles, spinous, hemispherical, amber in colour, larger over the elytrophore and on first pair of elytra.

Description. Holotype of Lepidonotus pilosus (AMNH 3531) robust, 2.5 cm long, 1.3 cm wide, 26 segments; body homogeneously yellowish without spots, integument wrinkled.

Prostomium longer than wide, slightly retracted into segment two; prostomial lobes laterally expanded. Two pairs of eyes, circular, dark, anterior pair on widest prostomial area, posterior pair hidden under anterior projection of segment two (Fig. 14A). Facial tubercle long, slender. Median antenna with ceratophore thick, long, inserted frontally, at same level of lateral antennae, style missing. Lateral antennae with ceratophores thick, long, inserted frontally on prostomial lobes, styles missing. Palps robust, long, two times longer than prostomial length, tapered into filiform tips, surface with rows of papillae. Pharynx not everted.

Tentacular segment not visible dorsally. Tentaculophores thick, long, inserted laterally to prostomium, with several chaetae; tentacular cirri missing. Second segment projected anteriorly over prostomium as a wide round lobe. First pair of elytrophores expanded laterally over tentaculophores, with large elytral scar. Segment three narrower than following ones.

Elytral margin with fringe of abundant long papillae (Fig. 14B), all with a distinctive bundle of papillae on posterior margin. Elytral surface with abundant spinous macrotubercles, and microtubercles. Macrotubercles pedunculate, distally hemispherical with abundant small spines, mostly scattered along elytral surface, but in first pair of elytra macrotubercles prominent, concentrated in elytral plug area (Fig. 14C, D). Microtubercles hemispherical or tapered, tips subconical.

Parapodia biramous, robust. Notopodia short. Neuropodia short, truncated, with acicular tips emergent (Fig. 14E, F). Notopodia with abundant brachial filaments (Fig. 14F), dorsally and laterally, each filament swollen, appearing septate, tips bifurcate. Dorsal cirri thin, long, slightly clavate, tips filiform. Cirrophores bulbous basally, elongate; elytrophores wide with large elytral scars. Ventral cirri short, not reaching neuropodial tips. Nephridial papillae thick, long.

Notochaetae abundant, thin, spinous capillaries, thinner and shorter than neurochaetae (Fig. 14E, F). Neurochaetae thick, dark amber (Fig. 14F), upper fascicle with shorter chaetae with long entire tips, lower ones curved, subdistally with short spines.

Remarks. Although Hartman (1939a) did not examine the type material of L. pilosus, she correctly regarded it as belonging to Chaetacantus but as a junior synonym of C. magnificus (Grube, 1876). Type material of both species was examined. Treadwell (1937) described and illustrated the type of L. pilosus indicating it has parapodial branchial filaments, and this confirms its belonging into Chaetacanthus. However, C. pilosus differs from C. magnificus (Grube, 1876), herein synonymized with C. brasiliensis (de Quatrefages, 1866). The main difference is that the elytra of C. pilosus do not have the prominent patch of sclerotized, amber macrotubercles arranged in honeycomb like patches, because of this difference C. pilosus is redescribed.

The nominal species, Lepidonotus pomareae, and the subspecies, L. p. panamensis, both have branchial filaments between successive parapodia (Fig. 16F). However, because the features of L. pomarae panamensis are the same as those shown by C. pilosus in prostomium (Fig. 16A), elytral ornamentation (Figs 15 A–D; 16B–E), notochaetae and neurochaetae (Fig. 16G, H), the subspecies deserved to be raised in status as a full species, as correctly indicated by Hartman (1948) as C. panamensis (Hartman, 1939). Nevertheless, this species shares the same morphological pattern with C. pilosus (Treadwell, 1937) and it is herein regarded as a junior synonym of the latter.

Furthermore, it is interesting to note that in the USNM in Washington (USNM 47981), there is another specimen incorrectly labeled as the holotype of Lepidonotus panamensis Hartman, 1939, collected in Honda Bay, near Coiba Island (R/V Velero III, Sta. 861-38). Hartman (1939: 44) included three specimens for her Lepidonotus pomareae panamensis, two from Station 863-38, and one from station 254-34, with no specimen from any other locality (station 861-38). Consequently, that additional USNM specimen cannot be the holotype (ICZN 1999, Art. 73.1).

It must be indicated that in C. pomareae (Kinberg, 1856), elytra of median segments only have bulbous microtubercles with thick tips, whereas in posterior elytra the prominent conical macrotubercles are basally spinous with long, smooth tips (see below), and these macrotubercles are not present in C. pilosus.

Type locality. Arena Bank (23°29’ N, 109°24’ W), Gulf of California.

Distribution. Gulf of California and Bahía Honda, Panama.