Euphionella Monro, 1936
Euphionella patagonica Monro, 1936
Voucher. Sea Lion station: 24MFB and station 29MFB.
Diagnosis. Voucher specimens complete; large, 20 to 55mm long and up to 16mm wide (including parapodia), with 25 chaetigers (this number is constant), 12 pairs of elytra, fleshy pseudoelytra on cirrigerous segments and branchiae detected from chaetiger 4.
Prostomium bilobed, longer than wide; ceratophore of median antenna in anterior notch, lateral antennae inserted terminally, styles of antennae long, smooth, expanded subdistally then narrowing into slender tip; 2 pairs of very faint eyes situated posteriorly on prostomium. Large, thick palps densely papillated, reddish longitidunal line can be detected on each palp on inner side.
Twelve pairs of large leathery elytra, covering dorsum on segments 2, 4, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25; lateral margin of elytra dorso- and ventrolaterally with many long, very soft, dense papillae; elytral surface always covered with small flattened, rounded microtubercules, additional with various number (usually around 30) small, distally inflated and papillated macrobtubercules; from around 4th elytral pair, very large, distally inflated papillated macrotubercules appear located on raised area around the attachments, varying in number from around 1-2 anteriorly to around 7 posteriorly. Fleshy pseudoelytra present on cirrigerous chaetigers (those not carrying elytra), distally with crenulated edge with large median crenulation and pair of shorter crenulations on each side, surface transparent; with 5 (in smaller voucher) to 10 (in large voucher) transverse lines and small rounded vesicles.
Parapodia biramous. Notopodia extremely reduced; with acicula; from 4th notopodium with few, short branchial filaments attached basally (can be easily overlooked); dorsal cirri with long smooth styles. Neuropodia massive, appear inflated; with short acicular lobe; edges sparsely covered by small papillae; ventral cirri very short, smooth.
Notochaetae, numerous but extremely soft and fine, finely serrated. Neurochaetae dark red to brown, very stout, large, unidentate, smooth spines up to 20 per fascicle, with 2-3 lowermost modified into spear-shaped tip. Nephridial papillae distinct from chaetiger 5 (although small can be detected from chaetiger 4). Pygidium simple lobe with a pair of short lateral cirri.
Remarks. Genus Euphionella is represented by four large bodied species (all with 25 segments), so far found only from deep-waters off South American continent:
Euphionella lobulata (Seidler, 1922) from Calbuco, Chile; E. patagonica Monro, 1936 from Patagonia; E. robusta Wesenberg-Lund, 1962 from Chile and E. besnardi Amaral and Nonato, 1985 from Brazil. Of those species Falkland Island specimens agree with Euphionella patagonica Monro, 1936 as it is the only species in which spear-shaped (also referred to as spatulate) chaetae in neuropodial fascicle were reported. It also agrees in having palps densely covered by papillae, long median antenna in relation to lateral antennae, nephridial papilla and ornamentation of elytra (detailed description given by Monro can be accessed here:
http://www.biodiversitylibrary.org/item/28331#page/75/mode/1up). It is important to note that degree of ornamentation of elytra varies with the size of specimen and also in different body regions in each specimen. It is generally accepted that the first pair of elytra is not diagnostic in Polynoidae, however in large bodied Euphionella up to first 3-4 elytra can be without very large macrotubercules (possessing microtubercules and variable number of smaller papillataed macrotubercules only), which are mostly developed and present in greatest number in mid to posterior elytra. The transition between small and large papillated macrotubercules is gradual and determining the exact number of each type can be difficult. Monro's specimen is only about 20mm long, similar in size to smaller specimens encountered in Falklands collection, while the largest specimen collected from FI is 55mm long. The size variation was already noted by Wesenberg-Lund (1962) and Hartmann-Schröder (1965) who investigated specimens of 35 and 36mm in length respectively.
