Aricidea (Allia) longisetosa, Sardá & Gil & Taboada & Gili, 2009

Sardá, Rafael, Gil, João, Taboada, Sergi & Gili, Josep Maria, 2009, Polychaete species captured in sediment traps moored in northwestern Mediterranean submarine canyons, Zoological Journal of the Linnean Society 155 (1), pp. 1-21 : 4-8

GENUS ARICIDEA WEBSTER, 1879

ARICIDEA (ALLIA) LONGISETOSA SP. NOV.

( FIG. 2A– F )

Type material: Holotype, complete specimen with about 140 chaetigers, deposited at CMIMA-CSIC ( NBI1 A3, trap 1; 43 °06′N, 05 °13′E; Dec. 1993). Specimen set aside for SEM analysis and stored on a stub . Paratypes, one specimen (ST01C21, trap 10; 41 °02′N, 01 °56′E; Nov. 1993), two specimens (ST08C13, trap 9; 41 °06′N, 01 °55′E; Aug. 1993), one of these later specimens was also used for SEM analysis.

Etymology: The species name refers to the morphological characteristics of its chaetae.

Diagnosis: Species distinguished by long capillary chaetae, and absence of neuropodial lobes on anterior region of body.

Description (based on holotype): Body about 20-mm long, 4-mm wide ( Fig. 2A ). Rounded prostomium fused to achaetigerous peristomium. Nuchal grooves

*Larvae and some juveniles not identified beyond family level.

present ( Fig. 2B ). Unpaired prostomial antenna cirriform, not articulate, extending posteriorly to third chaetiger. Prostomium with row of cilia on either side of antenna, and peristomium with another two rows of cilia behind prostomial one ( Fig. 2B ). Sixteen pairs of marginally ciliated branchiae that are stout, and taper uniformly to a blunt point, beginning on chaetiger 4 ( Fig. 2B ). Branchial segments with rows of cilia on dorsal side ( Fig. 2B ); ciliated rows absent after branchial region. Cirriform notopodial lobes present on all chaetigers; lobes in branchial region about half the length of branchiae, shorter in abranchial region; lobes becoming thinner posteriorly, with a length of around half the segment width. Neuropodial lobes absent. Both parapodial rami of all segments with long hirsute capillary chaetae. Chaetae: thicker in branchial region than in post-branchial region, becoming long (more than 0.5 mm), distinctly longer than chaetigers, and not decreasing in number ( Fig. 2A–D ). Single type of modified neurochaeta after branchial region: not pseudocompound, distinctly shorter than capillaries, but thicker, with long hairs, and with distal terminal filament ( Fig. 2E, F ). Pygidium: rounded with three small anal cirri.

Discussion: Aricidea (Allia) longisetosa sp. nov. belongs to the subgenus Allia , erected by Strelzov (1973) to include all Aricidea species with modified neurochaetae that gradually grade from long enlarged capillaries, to thicker chaetae, with terminal spines or mucrons, and finally to shorter, curved chaetae, sometimes sigmoid, either with or without a thin terminal extension. This subgenus currently includes 25 valid species and one subspecies ( Table 3). Aricidea (Alia) longisetosa sp. nov. clearly differs from most other species in the length (reaching chaetiger 3) and shape (cirriform) of the antenna. Only the nominal species Aricidea suecica Eliason, 1920 and its subspecies Aricidea suecica meridionalis Laubier & Ramos, 1974 , as well as Aricidea bryani Gaston & McLelland, 1995 , have similar cirriform antennae reaching chaetigers 2–3. However, these three taxa have neuropodial lobes in the anterior region of the body, whereas in the new species they are absent. In addition, specimens of A. (Allia) longisetosa sp. nov. are large organisms (with around 150 chaetigers) when compared with the rest of the Allia species, but they have only 16 pairs of branchiae compared with a maximum number of around 30 in large specimens of A. suecica ( Hartley, 1984) or A. bryani . The modified neurochaetae of A. (Allia) longisetosa sp. nov. closely resemble the modified chaetae of A. suecica (see Hartley, 1984: figs 6b, 7). Finally, besides neuropodial lobes, and the number of branchiae, the new species can be easily separated from A. suecica by its long capillary chaetae, which can be more than 0.5-mm long in the post-branchial region (not reaching the width of the body in A. suecica ).

FAMILY PARAONIDAE

Figures

Figure 2. Aricidea (Allia) longisetosa sp. nov. A, general view. B, dorsal view of the anterior region. C, mid-region parapodia with long capillary chaetae. D, fascicle of capillary chaetae and modified neurochaetae in medium parapodia. E, detail of modified posterior-region neurochaeta. F, group of branchiae showing cilia. Scale bars: A, 1 mm; B, C, and F, 200 Mm; D, 20 Mm; and E, 10 Mm.