Acoetes congoensis Pettibone 1989

Acoetes congoensis

Panthalis bicolor Grube, 1877:517 [part].

Polyodontes mortenseni.—Monro, 1930:69. [Not Polyodontes mortenseni Monro, 1928 (= Acoetes mortenseni (Monro), new combination).]

MATERIAL EXAMINED.—WEST AFRICA. Belgian Congo, Gazelle Expedition, holotype (ZMB 3252, as syntype of Panthalis bicolor); 2 paratypes (ZMB 840, as syntype of Panthalis bicolor). French Congo, off Cape Lopez, 58–67 m, mud and fine sand, Discovery sta 279, 10 Aug 1927, paratype (BMNH 1930.10.8.1176, as Polyodontes mortenseni by Monro, 1930).

TYPE MATERIAL.—Holotype (ZMB 3252) with 42+ segments, 30+ mm long, 13 mm wide with setae. Two paratypes (ZMB 840) with 39+, 33+ segments, 26+, 32+ mm long, 13, 15 mm wide. Paratype (BMNH 1930.10.8.1176) with 36+ segments, 23+ mm long, 8 mm wide.

DESCRIPTION.—Elytra oval, delicate, compactly areolate on most of surface, without lateral pocket (Figure 56C). Prostomium bilobed, oval, with pair of bulbous ommatophores with distinct neck; ceratophore of median antenna in middle of prostomium, with few lateral papillae, with tapered style not extending to tips of ommatophores; lateral antennae attached ventral to ommatophores and hidden from view dorsally; posterior pair of small eyespots lateral to ceratophore of median antenna; ventral palps stout, long, tapered, up to 2 times length of prostomium, with longitudinal rows of short papillae (Figure 56A,B). Tentacular segment distinct dorsally; tentaculophores lateral to prostomium, each with 2 acicula, bundle of slender setae on inner side, and pair of dorsal and ventral tentacular cirri, similar to median antenna (Figure 56A,B,D).

Second segment with first pair of elytrophores, ventral buccal cirri longer than following ventral cirri and biramous parapodia; notopodia bilobed with longer upper digitiform acicular lobe and shorter rounded lower lobe, with bundle of long finely spinous capillary notosetae; neuropodia larger, conical, with prominent ventral bract; neurosetae long, finely spinous, slender, slightly wider basally, tapering to capillary tips, lower ones shorter (Figure 56A,E–H). Distal border of extended pharynx with 15 pairs of papillae, middorsal one largest, on somewhat lobulated base, midventral one only slightly larger than others; 2 pairs of hooked jaws, each with 4–5 lateral teeth.

Third segment with first pair of dorsal cirri with short cirrophores and styles extending almost to tips of setae; ventral cirri similar in length; notosetae fewer and shorter; upper neurosetae similar to those of segment 2, middle ones stout, aristate, lower ones slightly curved, with prominent spines basally and close-set spines distally, with capillary tips (Figure 56I–L). Parapodia of segment 8 larger, with tapering dorsal cirri, short notosetae, and similar but stouter neurosetae (Figure 57A–D).

Beginning with segment 9, notopodium rounded, flattened, on anterodorsal half of larger neuropodium, with notoaciculum, spinning gland and row of short notosetae emerging from inner side of notopodium; neuropodium truncate, with slightly distinct anteroventral bract; lower neurosetae numerous, within anteroventral bract, similar to those of more anterior parapodia; middle row of stout acicular aristate neurosetae, some with subdistal spines on one side; upper group of neurosetae, emerging from low anterodorsal bract, hidden by notopodium, of 2 types: (a) slender, long, tapering abruptly to slender tip with subdistal long hairs on one side and short spines basally; (b) short, more slender, bipinnate, hidden by notopodium (Figure 57F–J). Ventral cirri short, subulate (Figure 57E,G,H). Branchiae indistinct, anterior and posterior borders of parapodia thin-walled; thin-walled inflated areas ventrally medial to ventral cirri.

ETYMOLOGY.—The species is named for the type locality, that of the Belgian Congo.

DISTRIBUTION.—West Africa. Up to 67 meters.