A new species of the genus Aonides Claparède , 1864 ( Polychaeta : Spionidae ) from the Macaronesian region ( Eastern Central Atlantic )

The Spionidae is one of the families with the greatest number of species in midlittoral and shallow subtidal habitats worldwide, with over 1,000 species belonging to 33 genera (Sigvaldadóttir et al., 1997). In the Canary Islands (central Macaronesian region), the first records of Spionidae were by Langerhans (1881), Núñez et al. (1984), and Maciolek (1985, 2000). Recent works on endobiont polychaetes from demosponges (Pascual, 1996) and fauna associated with Cymodocea nodosa rhizomes (Brito-Castro, 1999), increased the number of species of the Spionidae from the central Macaronesia to 19 species. The genus Aonides Claparède, 1864 includes six species with a worldwide distribution (Blake et al., 1996): A. oxycephala (Sars, 1862), A. paucibranchiata Southern, 1914, A. californiensis Rioja, 1947, A. trifida Estcourt, 1967, A. mayaguezensis Foster, 1971, and A. glandulosa Blake, 1996. Until now, only one species has been recorded from the study area, A. oxycephala (Bellán, 1969). SCIENTIA MARINA 70S3 December 2006, 59-64, Barcelona (Spain) ISSN: 0214-8358


INTRODUCTION
The Spionidae is one of the families with the greatest number of species in midlittoral and shallow subtidal habitats worldwide, with over 1,000 species belonging to 33 genera (Sigvaldadóttir et al., 1997).In the Canary Islands (central Macaronesian region), the first records of Spionidae were by Langerhans (1881), Núñez et al. (1984), and Maciolek (1985Maciolek ( , 2000)).Recent works on endobiont polychaetes from demosponges (Pascual, 1996) and fauna associated with Cymodocea nodosa rhizomes (Brito-Castro, 1999), increased the number of species of the Spionidae from the central Macaronesia to 19 species.

MATERIAL AND METHODS
The samples were taken during 1994 from Ensenada de los Abades (SE of Tenerife, Canary Islands) in a sandy bottom of Cymodocea nodosa seagrass, and in a muddy sand bottom from Selvagens Islands (Fig. 1), during the "Macaronesia 2000" expedition in May 1999 on board the R.V. "Corvette".
Samples were collected by scuba-diving at depths of 13-18 m and drilling into the sediment with PVC tubes.The tubes employed were 45 cm long with a 4.5 cm inner diameter.The samples were preserved in buffered 10% seawater/ formaldehyde and sieved through a 100 μm mesh.Sorted specimens were preserved in 70% alcohol.Several specimens were mounted in glycerine gel and drawings were made using a camera lucida on a Leica DMLB microscope equipped with Nomarski interference contrast.Some specimens were examined with scanning electron microscopy (SEM, Jeol JSM-6300), after critical point drying and gold sputtering.
The specimens were deposited at the Museo de Ciencias Naturales de Madrid (MCNC), Museo de Ciencias Naturales de la Naturaleza y el Hombre de Tenerife (TFMC) and at the Departamento de Biología Animal (Zoología), Universidad de La Laguna (DBAULL).

Aonides Claparède, 1864
Diagnosis.Prostomium conical, narrow, and tapered anteriorly; occipital tentacle and eyes present or absent.Peristomium fused to the prostomium, without lateral wings.Branchiae beginning on chaetiger 2, present in the anterior region of the body; branchiae all cirriform, not fused to the dorsal lamellae.Chaetae of two types: limbate capillaries anteriorly, and bidentate, tridentate or tetradentate hooded hooks arranged in the notopodia and neuropodia of the median and posterior region.Pygidium with 2-12 acuminate anal cirri.
Etymology.The specific name selvagensis refers to the type locality (Selvagens Islands), where the species was collected for the first time.
Remarks.The new species Aonides selvagensis is characterized by the presence of tridentate hooded hooks, 6-8 pairs of branchiae, absence of eyes, and five anal cirri.Aonides selvagensis most closely resembles A. paucibranchiata Southern, 1914 in having tridentate hooded hooks and a similar number of branchial pairs.A. selvagensis differs in the absence of eyes, the first occurrence of the notopo- dial hooded hooks (chaetigers 22-36 in A. paucibranchiata and chaetiger 13 in A. selvagensis) and neuropodial hooks (chaetigers 17-30 in A. paucibranchiata and chaetiger 11 in A. selvagensis).
The pygidium has four anal cirri in A. paucibranchiata and five cirri in A. selvagensis (see Table 1).

DISCUSSION
Morphological studies concerning the variability of taxonomic characters in species of Aonides, have shown that the approaches to distinguishing the species of the genus are inadequate (Ramos, 1976).Ramos observed a great variability in populations of A. oxycephala, reaching the conclusion that A. californiensis and A. mayaguezensis are junior synonym of A. oxycephala.A comparative revision of the type material is needed to elucidate the validity of the species (see Table 1).Within the seven known species of the genus two groups can be distinguished based on the type of hooded hooks that are present.The first group, characterized by having bidentated hooks, contains the species: A. californiensis, A. mayaguezensis, A. oxycephala and A. glandulosa.The second group with tri-and tetradentated hooded hooks contains: A. paucibranchiata, A. trifida and the new species A. selvagensis.The apomorphic character of tetradentated hooks (three divisions in the distal tooth -Estcourt, 1967) in A. trifida, distinguishes this species from the others in the second group.A. paucibranchiata and A. selvagensis n. sp. are closely related, both having tridentate hooks.A. paucibranchiata is an amphiatlantic species with some records from the Atlantic-Mediterranean region and is possibly present in the Canaries sand-banks, since the polychaete fauna is similar throughout the region.Aonides selvagensis n. sp.possesses some adaptations for life in marine caves and other interstitial environments with low light intensity, e.g.small size, below 10 mm long, and lacks eyes while the other species are larger (10-20 mm long); and have eyes.

AKNOWLEDGEMENTS
This paper was partially supported by the project "Macaronesia 2000" of the Museum of Natural Sciences of Santa Cruz de Tenerife.Special thanks to Dr. J.J. Bacallado director of the project and to the crew of R.V. "Corvette".The comments and suggestions of two anonymous referees greatly improved the manuscript.
A NEW SPECIES OF SPIONIDAE FROM THE MACARONESIAN REGION • 63 FIG. 1. -Map of Selvagens Islands, showing sampling stations (circles 1-10) and the location of the Macaronesian Central region (Madeira, Selvagens and Canary Islands).