Syllidae (Annelida, Polychaeta) from the Caribbean coast of Venezuela

Abstract Venezuela possesses a great variety of coastal environments allowing for a high diversity of marine species. However, systematic studies on marine invertebrates are scarce, especially on polychaetes. The family Syllidae is poorly known, and only 14 genera and 42 species have been reported from this country. A total of 13 genera and 26 species the Syllidae were identified from benthic samples collected on different substrata of the northeastern coast of Venezuela. Of these, seven genera and 16 species constitute new records for Venezuela: Odontosyllis guillermoi, Syllides floridanus, Salvatoria clavata, Salvatoria limbata, Sphaerosyllis longicauda, Parapionosyllis longicirrata, Trypanosyllis parvidentata, Trypanosyllis vittigera, Opisthosyllis sp., Syllis amica, Syllis armillaris, Syllis gracilis, Syllis pseudoarmillaris, Syllis vittata, Parasphaerosyllis indica and Myrianida convoluta.


introduction
There have been very few studies done on the benthic macrofauna, especially polychaetes, along the Caribbean coast of South America. Syllidae is one of the most abundant within the polychaete families. It is constituted by about 55 valid genera and approximately 667 species (San Martin 2003), of which a total of 31 genera and 167 species have been described from the Great Caribbean Region (Salazar-Vallejo 1996). In soft and hard bottoms of the eastern coasts of Mexico (Gulf of Mexico and Caribbean), 45 species of syllids were identified by Granados-Barba et al. (2003). In nearby Trinidad and Tobago islands, Syllidae was both the most abundant (70%) and diverse (30 species) family collected from hard bottom substrates (Gobin 2010). In Venezuela, very little is known about this family, and only two systematic studies have been carried out, both by San Bone (1999, 2001) on Thalassia testudinum (Bank & Köning, 1805) meadows. In 1999 these authors described two new species and in 2001 they reported 13 genera and 40 species, of which 35 constituted new records for Venezuela. In this study, syllid species collected from different localities and substrata of the northeastern coast of Venezuela are reported.

Materials and methods
The examined material belongs to samples from the Benthos Laboratory polychaete collection at the Instituto Oceanográfico de Venezuela, collected from 1984 until the present. Samples were collected manually or by using dredges and corers on different substrata: rocky shores, sandy and muddy bottoms, on dock piles of PVC and in dead of the fire coral Millepora alcicornis Linnaeus in Mochima Bay (Isla Larga, Punta León, Ensenada de Reyes, Mangle Quemado, Cabruta, and La Virgen) and the Gulf of Cariaco (Turpialito, Guacarapo and La Bruja), inside sponges Aplysina fistularis (Pallas, 1766), Ircinia felix (Duchassaing & Michelotti, 1864), and Chondrila nucula Schmidt, 1862 (Porifera: Demospongiae) in Mochima Bay (Isla Larga, Punta León); from Rhizophora mangle Linnaeus root mats covered with the bivalve Crassostrea rhizophorae (Gmelin) in La Restinga Lagoon, Margarita Island, from sandy bottoms at the mouth of Bocaripo Lagoon, and as epibionts on tubes of Americonuphis magna (Andrews, 1891) from Chacopata Beach (see coordinates and dates of collections in Table 1).
Description. Length to 2.3 mm, width to 0.12 mm. Body small, slender; complete specimens with up to 33 chaetigers. Subulate antennae with enlarged median zone and long distal one. Median antenna longer than lateral ones. Prostomium with a pair of eyespots and two posterior pairs of eyes in trapezoidal arrangement. Compound unidentate falcigers with serrated blades (Fig. 1.18) and with smooth blades 1.19). In each parapodium one bidentate compound falciger with long basal serrations ( Fig. 1.20). Slender, unidentate dorsal simple chaeta with slight serrations, from chaetiger 1-2. Ventral simple chaeta unidentate, only present on posterior chaetigers. Acicula subdistally enlarged with pointed tip (Fig. 1.21). Pharynx extending through 3 chaetigers, with dorsal rhomboidal tooth located near anterior margin; proventriculus through 3-4 chaetigers with 16-18 rows of muscle cells. Pygidium with a pair of cirriform anal cirri.

Sphaerosyllis piriferopsis
Remarks. From hard bottom substrats of Trinidad and Tobago islands is the most abundant species (Gobin 2010).

Exogone (Exogone) lourei
Remarks. According to San Martín (1991) T. zebra from the Mediterranean Sea is very similar to T. vittigera, differing only in the number of teeth on the trepan and in the length of the proventriculus, thus suggesting the need for a revision of T. zebra and related species.

Genus
Remarks. This species is one of the most abundant syllid in the Great Caribbean region in both soft and hard bottoms (Granados- Barba et al. 2003); Gobin (2010) pointed out that is one of the most abundant species from hard bottoms of Trinidad and Tobago. Martin et al. (2003) based on the wide variability observed within the Haplosyllis species, pointed out that the so-called H. spongicola must be considered as a pseudo-sibling species-complex. Martin et al. (2003) and Lattig et al. (2007) pointed out that records in temperate and tropical seas must be reviewed.
Remarks. Opisthosyllis sp. resembles O. brunnea Langerhans 1991, in having compound chaetae with unidentate blades, and in the location of the pharyngeal tooth; it differs in the absence of an occipital flap, having a wider proventriculus, and in the number of rows of muscle cells in the proventriculus.