Ophelina margaleffi, 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 : 11

OPHELINA MARGALEFFI SP. NOV. ( Fig. 4A–F )

Type material: Holotype, complete specimen, with 22 chaetigers, and deposited at CMIMA-CSIC (ST01C21, trap 10; 41 °02′N, 01 °56′E; Nov. 1993). Paratypes, two specimens deposited at CMIMA-CSIC (ST08C13, trap 9; 41 °06′N, 01 °55′E; Aug. 1993), four specimens (NBI6B8, trap 6; 42 °26′N, 03 °33′E; Feb. 1994), four specimens (NBI6B11, trap 6; 42 °26′N, 03 °33′E; Mar. 1994). Non-type material: a total of 1142 specimens were collected; 1033 were sampled at Planier and Lacaze-Duthier submarine canyons, and 109 were sampled at Foix submarine canyon. Non-types deposited at the authors collection, and at the Museum of Natural Sciences in Madrid. Other material examined: 12 specimens of Ophelina modesta Støp-Bøwitz, 1958 from Langesundsfjord ( Norway), and a few specimens of Ophelina cf. modesta collected from the Bay of Roses ( Spain).

Etymology: The species is dedicated to Dr Ramon Margalef, an eminent ecologist who recently passed away, in gratitude for all his stimulating work.

Diagnosis: Species distinguished by the number of chaetigers and the size of the chaetae in relation to the size of the branchiae.

Description: Body fusiform, small, grooved ventrally and laterally, with 22 chaetigers (holotype), mostly 22–24 ( Fig. 4A–C ). Holotype: 3.2-mm long (ranging from 3.0 to 3.4 mm in paratypes, similar length in the rest of specimens), 0.32-mm wide (ranging from 0.28 to 0.32 mm in paratypes). Prostomium with acuminate tip. Two large nuchal organs located laterally on prostomium ( Fig. 4B ), eyespots absent. Branchiae: cirriform, small, laterally ciliated, present from chaetiger 2 to 20, shortest in first chaetigers. Ciliary bands distributed on every segment, starting on chaetiger 2 ( Fig. 4C ), one ciliary band observed at parapodial level. Between two consecutive parapodia, another ciliary band is observed dorsally, and two additional ones are observed ventrally ( Fig. 4A–C ). Parapodia occur as rounded lobes. No recognizable cirri. Lateral organ present in the middle of every parapodial lobe ( Fig. 4D ). Chaetae: all capillary and hirsute ( Fig. 4E ), with several chaetae longer than the prostomium width. Anal tube: cylindrical (maximum length about 0.14 mm), terminating in six subequal papillae, with the two ventralmost ones larger than the others ( Fig. 4F ).

Discussion: From all the known Ophelina species (about 60 species), O. modesta most closely resembles O. margaleffi sp. nov., especially in its size and the number of chaetigers. Unfortunately, the type material of this species could not be located in Scandinavian museums, but 12 specimens of O. modesta from Langesundsfjord, Norway (107 m depth) collected in 2003, close to the type locality, were available for study. The specimens from Lagesundsfjord were clearly different to O. margaleffi sp. nov.: they had distinct eyes on the prostomium, the chaetae of the parapodia were shorter and not hirsute, and were present in lower numbers, and its nuchal organs were very apparent, similar to that observed in the original illustrations in the description of O. modesta (Støp- Bøwitz, 1958). The specimens of O. margaleffi sp. nov. were also compared, using SEM, with several specimens identified as O. cf. modesta obtained from muddy sediments at a depth of 65 m in the Bay of Roses (Catalan Mediterranean region). The O. margaleffi sp. nov. specimens clearly differ from those of O. cf. modesta collected in the Bay of Roses, but the O. cf. modesta specimens from the Bay of Roses were similar to those from Langesundsfjord (eyes on the prostomium, shorter, non-hirsute chaetae, and no ciliary bands on the body). The anal funnel structure is quite similar in both species. Our observations and measurements, using a light microscope, on 126 individuals showed that O. margaleffi sp. nov. never had more than 24 chaetigers, and that even for small individuals (10–14 chaetigers), the length of the chaetae clearly surpassed the width of the prostomium and the length of its branchiae.

FAMILY LOPADORHYNCHYIDAE

Figures

Figure 4. Ophelina margaleffi sp. nov. A, general view. B, lateral view of anterior region. C, mid-region parapodia showing cirriform branchiae and ciliary bands. D, lateral organ observed in the middle of every parapodial lobe (from left to right dorsoventral orientation). E, hirsute capillary chaetae. F, pygidium with six subequal papillae. Scale bars: A, 1 mm; B, C, 100 Mm; F, 50 Mm; E, 10 Mm; and D, 5 Mm.