Gesaia

Diagnosis (from Capa & Hutchings, 2019). Operculum completely divided into two elongate lobes and distal disc perpendicular to operculum. Few (4 – 8) pairs of long and conical papillae spirally arranged from nuchal hook to ventral distal end of opercular lobes. Three to five tentacular filaments along margins of buccal cavity. Buccal flaps absent. Pair of fine palps longer than operculum. Median organ at dorsal junction of opercular lobes. Outer paleae arranged in semicircle or spiral, with cylindrical or slightly flattened blades, with frayed thecae and distal ends rolled inward. Inner paleae arranged on dorsal inner margin of opercular lobes, with straight cylindrical and smooth blades. Pair of nuchal hooks without limbation. Neuropodia of segment 1 with two to three pairs of cirri. Thoracic branchiae present. Four parathoracic segments. Parathoracic notopodia with robust lanceolate chaetae and fine capillaries, neuropodia with capillaries only.

Remarks. Kirtley (1994) erected the genus Gesaia with eight species collected from depths 770 – 5790 m (Table 2). The genus differs from other sabellariid genera by having a pair of elongated and well separated elongate opercular lobes and cylindrical outer paleae with distal ends rolled inward, distal disc of opercular lobes positioned perpendicular to longitudinal axis of operculum, few (generally one) pairs of nuchal hooks without limbation, and four parathoracic segments. Kirtley (1994) described seven new species of Gesaia mainly based on the ornamentation of the outer paleae, but did not provide any details of the body. The genus Gesaia has only previously been recorded from Australian waters as a larva collected in plankton samples at Lizard Island (Capa et al. 2012), although Hutchings et al. (2012) indicated that the genus was absent from Australian waters.

Type locality. Off Madeira Archipelago, in 1968 m.

Type species. Phalacrostemma elegans Fauvel, 1911.