Halosydna Kinberg, 1856

Salazar-Silva, Patricia, 2013, Revision of Halosydna Kinberg, 1856 (Annelida: Polychaeta: Polynoidae) from the Tropical Eastern Pacific and Grand Caribbean with descriptions of new species, Journal of Natural History 47 (17 - 18), pp. 1177-1242 : 1179-1180

Genus Halosydna Kinberg, 1856

Type species

Halosydna patagonica Kinberg, 1856: 385 .

Diagnosis

Body thin, sub-rectangular, with 36 segments. Prostomium bilobed, without cephalic peaks; two pairs of small eyes, both pairs on posterior half of prostomium; three antennae, median antenna with ceratophore inserted frontally, with long, thick, style, subdistally expanded and tip filiform, surface not papillose; lateral antennae with ceratophores inserted terminally as prolongations of prostomium, at same level of ceratophore of median antenna, style of similar shape to median antenna. Two palps. Pharynx with nine pairs of marginal papillae and two pairs of hard jaws. Tentacular segment not visible dorsally, tentaculophores lateral to prostomium, tentacular cirri similar to antennae. Body with 18 pairs of elytra on segments 2, 4, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 28, 30, 31, 33. Posteriormost three segments with dorsal cirri. Elytra imbricated; margins with or without papillae; surface with papillae and / or tubercles (sclerotized or vesicular). Elytrophores rounded. Parapodia biramous. Notopodia shorter than neuropodia. Neuropodia distally truncated, with small rounded lobe near acicula tip. Dorsal cirri subdistally expanded and distally with filiform tip; cirrophore basally expanded. Dorsal tubercle inconspicuous. Ventral cirri shorter than neuropodia, tapering to fine tip.

Notochaetae shorter than neurochaetae; with rows of spines; less abundant than neurochaetae; the smaller curved, with blunt tip, remaining ones slender tapering to capillary tips. Neurochaetae with rows of spines on upper region, tips entire or bidentate. Anus dorsal, between segments 35–36. Pygidium with one pair of anal cirri.

Remarks

Members of Halosydna were described by Kinberg (1858) as having 18–21 pairs of elytra. However, all specimens examined in this study have 18 pairs, as defined by Hartman (1938). In addition, members of Halosydna species are recognized by eytral insertion: elytra of segments 27 and 28 are contiguous, also elytra of segments 30 and 31. Elytral arrangement is constant and important to confirm generic placement. Members of Halosydna have robust bodies, which neither autotomize nor lose elytra when collected or fixed. Members of all species consistently bear a small rounded lobe near the neuroacicular tip.