Exogone (Parexogone) canyonincolae, Sardá & Gil & Taboada & Gili, 2009, 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 : 15-17

EXOGONE (PAREXOGONE) CANYONINCOLAE

SP. NOV. ( FIG. 7A–F )

Type material: Holotype, complete specimen (ST01C22, trap 10; 41 °02′N, 01 °56′E; Nov. 1993). Specimen set aside for SEM analysis and deposited at CMIMA-CSIC. Paratype, complete specimen ( NBII6 B10, trap 6; 42 °26′N, 03 °33′E; Sep. 1994) .

Etymology: The name of the species refers to its habitat, within submarine canyons.

Diagnosis: Species characterized by having long median antenna and very small lateral antennae, several aristae on dorsal simple chaetae, and compound chaetae with bidentate blades with long spines not extending beyond tips, and shafts with long spines extending beyond hinges.

Description: Holotype (50 chaetigers) and paratype (34 chaetigers), both complete specimens. Holotype about 0.1-mm wide, 2.5-mm long ( Fig. 7A ). Prostomium: triangular, broader than long. No recognizable eyes in paratype. Median antenna: long and fusiform, longer than prostomium. Lateral antennae clearly shorter and not longer than prostomium ( Fig. 7B ). Palps: long, broad, fused along entire length, and longer than prostomium ( Fig. 7B ). Tentacular and dorsal cirri minute; dorsal cirri present in chaetiger 2 ( Fig. 7B ). First five anterior chaetigers containing about 15–17 compound chaetae, with marked dorsoventral gradation in length; 25–27 Mm above, 5–6 Mm below ( Fig. 7B, C ). Compound chaetae with thick, broad shafts, ending with numerous spines at their articulation with blades ( Fig. 7F ). Blades with numerous long fine spines, not reaching beyond their bidentate tips. Subdistal tooth of blade smaller than distal one. Simple chaetae absent from anterior chaetigers. From chaetiger 6, number of chaetae per parapodium reduced to six or seven ( Fig. 7D ). One dorsal simple chaeta with bidentate tip, slightly curved, with several aristae clearly extending beyond tip, and other distally long fine spines ( Fig. 7E ), one compound chaeta with elongate, spiniger-like blade (around 30 Mm), with bidentate tip and long fine spines not reaching beyond tip, and five compound chaetae with shorter blades (around 10 Mm), and similar shape as the longer one ( Fig. 7F ). In all cases, the subdistal tooth was smaller than the distal one, and the shafts of falcigers had long, fine, spines clearly extending beyond the hinge. Posterior parapodia with only five chaetae: one dorsal, simple one, one compound with spiniger-like blade, longer than those present in mid-body parapodia (around 40 Mm), and three compound shorter chaetae; all of them with similar forms to the ones present in the mid-body parapodia. Ventral simple chaetae: not seen. Holotype and paratype bearing long, smooth, natatory chaetae in posterior part. Aciculae observed in paratype: solitary, one per chaetal bundle, and distally rounded. Pharynx and proventriculus: visible in paratype. Pharynx: short, through about three chaetigers; pharyngeal tooth on anterior rim. Proventriculus: short, through three chaetigers, with about 14 muscle cell rows. Pygidium: semicircular with two anal cirri.

Discussion: Exogone (Parexogone) canyonincolae sp. nov. is similar to Exogone (Parexogone) wolfi San Martín, 1991 , Exogone (Parexogone) panelopeae San Martín, 2005 , or Exogone (Parexogone) patriciae San Martín, 2005 , all of which have a long median antenna, and dorsal simple chaetae with long aristae, clearly surpassing the teeth. However, in E. (Parexogone) canyonincolae sp. nov., the absence of long spiniger chaetae in the parapodia of the mid-body and posterior regions, the long spines of its shafts, and the absence of ventral chaetae similar to the dorsal ones, are clear differences from E. (Parexogone) wolfi , whereas the presence of a subdistal tooth smaller than the distal one in falciger chaetae distinguishes it from E. (Parexogone) panelopeae and E. (Parexogone) patriciae . Other species of Exogone have been described recently from the Capbreton submarine canyon, Bay of Biscay, North Atlantic Ocean ( San Martín, Ceberio & Aguirrezabalaga, 1996). Although they show distinct morphological characters when compared with E. (Parexogone) canyonincolae sp. nov., all of them can be characterized by the presence of aristae, and long spines sometimes extending beyond the tips of the blades.

Figures

Figure 7. Exogone (Parexogone) canyonincolae sp. nov. A, general view. B, dorsal view of the prostomium and the first chaetigers. C, posterior chaetigers showing smooth natatory chaetae. D, mid-region parapodia showing the simple dorsal chaeta and the compound chaetae: one with a spiniger-like blade, and the rest with shorter blades. E, end of the dorsal simple chaeta. F, compound chaetae of mid-region parapodia. Scale bars: A, B, 50 Mm; C, D, 30 Mm; F, 5 Mm; and E, 3 Mm.