Deep-water polychaetes ( Annelida ) from the southeastern Gulf of California , Mexico

Polychaetes inhabiting deep-sea soft bottoms from the southeastern Gulf of California were collected during four oceanographic cruises during 2000 and 2001. Sampling of benthic organisms was performed with a benthic sledge to collect epifauna and a Karling dredge for epifauna and infauna, in a depth range from 732 to 2 250 m. A list of the polychaetes that were collected and their distribution are presented here. A total of 73 species (distributed among 33 families) were identified. Moreover, 11 species were identified only to genus level and 20 species only to family level. With the exception of Ancistrosyllis hartmanae and Melinnampharete eoa, all identified species have been previously reported in soft bottoms of the Gulf of California or in adjacent areas. Additional previously unreported information is provided herein regarding depth ranges, geographical distribution, morphology and tubes inhabited by the organisms. The morphology of the ampharetids Amage sp. and Samytha sp. does not coincide with that of other species in these genera reported for the Gulf of California, which suggests that they are probably undescribed species. Rev. Biol. Trop. 54 (3): 773-785. Epub 2006 Sept. 29.

by Sarti-Martínez (1984), Lezcano-Bustamante (1989), Hernández-Alcántara (1992) and Hernández-Alcántara and Solís-Weiss (1999).Literature of other studies in the area is included in Salazar-Vallejo et al. (1989).Nevertheless, polychaetes from deep-sea waters in the Gulf of California and adjacent areas have been hardly investigated.The first studies of the polychaetes from deep basins off southern California were by Hartman (1960Hartman ( , 1963)).Fauchald (1972) later identified 227 species (of which 66 were new) from material collected during the ALBATROSS expedition as reported by Chamberlin (1919a) and Treadwell (1923), and from material collected during two cruises with the VELERO IV in 1967 and1970.The most recent studies in the hydrothermal vents from the Guaymas basin were reported by Blake (1985), Solís-Weiss and Hilbig (1992) and Solís-Weiss and Hernández-Alcántara (1994).Other recent studies concerning deep-sea polychaetes in the northern Pacific were performed by Fauchald and Hanckock (1981) in Central Oregon, and Blake and Hilbig (1990) in the Juan de Fuca and the Explorer Ridge systems in the northeast Pacific.Recently, Blake andother collaborators (1994-2000) compiled information related to polychaetes from the Point Conception region of southern California at depths from 50 to 1 000 m, which includes four volumes of a Taxonomic Atlas of the benthic fauna of the Santa Maria Basin and Western Santa Barbara Channel.
The TALUD project, organized by the Laboratory of Invertebrates of the Mazatlán Marine Station (Instituto de Ciencias del Mar y Limnología, UNAM), is a multidisciplinary project encompassing the study of crustaceans, mollusks, polychaetes, fish and meiofauna in the southern Gulf of California.Prospective cruises were conducted in 1989-1991 (TALUD 1 to 3) wherein no grabs were used and the polychaete fauna was not studied.Four additional cruises (TALUD 4 to 7) were organized in 2000 and 2001, which did include the collection of polychaetes.
During the last decade, few studies of polychaetes inhabiting deep-water have been performed in southern California or the Gulf of California.The purpose of this paper is to contribute to the knowledge of the polychaete fauna occurring offshore in soft sediments at a depth range from 732 to 2 250 m in the Southeastern Gulf of California.

MATERIALS AND METHODS
Benthic organisms associated with deep soft bottoms (732 to 2 250 m depth) were collected aboard the R/V "El Puma" (Universidad Nacional Autónoma de México) during four oceanographic cruises: TALUD 4 in August 2000 (11 stations), TALUD 5 during December 2000 (ten stations), TALUD 6 in March 2001 (12 stations), andTALUD 7 in June 2001 (13 stations).Two types of gear were used at most stations: a) a 2.35 m wide by 0.95 m high modified benthic sledge equipped with a collecting net of ca.5.5 cm (2 1/4") stretch mesh lined with ca. 2 cm (3/4") mesh net in the mouth area, and b) a 110x40x14 cm Karling dredge used to collect sediments to a depth of 7 cm, with a capacity of 851.
Polychaetes retained in the benthic sledge were directly collected with forceps and fixed with 10 % formaldehyde solution.The sediment collected with the Karling dredge was washed through a 0.5 mm sieve and the polychaetes were sorted and fixed on board.Specimens found inside thick muddy tubes were fixed by adding 10 % formaldehyde solution through one of the tube openings using a syringe.

RESULTS
The position and depth range of stations in which polychaetes were collected are included in Table 1.
The families best represented in the study area are Ampharetidae (13 taxa), Maldanidae (11 taxa), and Cirratulidae and Phyllodocidae (eight taxa each).Based on their occurrence for different stations and cruises, the most representative species for the study area are: Melinna exilia, Melinnampharete eoa, Thelepus hamatus, Mexamage corrugata, Terebellides stroemi, Fauveliopsis rugosa, Nothria iridiscens, Califia calida, Neoheteromastus lineus and Maldane cristata.Except for Ancistrosyllis hartmanae and M. eoa, all identified species have been previously reported for the Gulf of California or adjacent areas in soft bottoms.
Only species for which new information was obtained were treated individually.New data related to depth range, distribution, morphology or tube description (or other protective structures in which the animals were found) are provided here.

Family Chaetopteridae
Phyllochaetopterus limicolus.This species lives in a slender, smooth, cylindrical, unbranched tube measuring 20 cm long by 0.5-0.6 cm wide

Serpulidae indeterminable 34
The numbers in columns correspond to the collection stations (KD= Karling dredge; BS= Benthic sledge).
TABLE 2 (…continued) List of polychaete species collected during the four cruises (Hartman 1969).One specimen from station 4 (TALUD 6) was found inside a 1.8 cm long tube with a mucoid base, externally covered by mud.It is probable that the worm abandoned its own tube (a typical chaetopterid tube was found in the same sample) and invaded this empty tube, which may have been produced by another polychaete.

Family Maldanidae
Maldane cristata.The tubes are thick and mucoid, covered with compact mud (0.5 cm external diameter).
Maldanidae sp. 1 to sp. 8. Several maldanids lacked the posterior end which made species identification impossible.According to the characteristics of the prostomium, eight different species were tentatively distinguished.

Family Phyllodocidae
Eteone cf.dilatae.One specimen fits the description of E. dilatae but appears to be a juvenile because the tentacular and dorsal cirri are not well developed.The eyes are absent, while E. dilatae has two small eyes.Although this species has been reported from the intertidal zone to 177 m (Hartman 1936, 1963, 1968, Reish 1968), our sample was collected at a depth range of 1 580 to 1 600 m.
Steggoa gracilior.This species has been reported for the Gulf of California by Chamberlin (1919b) and Hartman (1968), but depth of occurrence was not provided.The unique specimen found during this study was collected at 1 244 m depth.
Polynoidae sp. 1, sp. 2, sp. 3. Three different species of polynoids were recognised but they were too incomplete to make identification possible.

Family Pilargidae
Ancistrocyllis hartmanae.Two specimens were collected in depths ranging from 1 500 to 2 040 m, while this species had been reported in the Chesapeake Bay at 12.8 m by Pettibone (1966) and by Fiege and Bogemann (1999).

Family Amphinomidae
Pareurythoe (?) sp.Three specimens were found: two from 778-800 m and one from 1 060-1 090 m.Placement of these specimens in this genus is dubious since they have slender notoseate, suggesting that all of them are epitokous forms.All specimens have bifid neurosetae, yellow aciculae, three smooth antennae and smooth dorsal cirri, which fits with P. californica, described from the Gulf of California (Hartman 1968).Nevertheless, the presence of dendritic branchiae from setiger three to the end of the body, and the absence of eyes suggests that they could be a different species.
Pseudeurythoe (=Linopherus; Salazar-Vallejo 1987) ambigua.It was collected at several stations: one specimen from station 14 at 2 080-2 140 m (TALUD 5), two specimens from station 18 at 890-950 m (TALUD 6) and one individual from station 18 at 950-1 010 m (TALUD 7).The species is reported from southern California from 1 645 to 1 900 m by Hartman (1968).This author indicates that two different branchial arrangements can be found in this species: a) branchiae present at setiger four and continuing for seven segments, and b) branchiae present at setiger three and continuing for 43 segments.The specimens collected at station 18 (both cruises) correspond to the first branchial arrangement, while those from station 14 correspond to the second branchial arrangement, perhaps due to clinal variation.

Family Onuphidae
Anchinothria fissurata.The tube had not been previously described.In cross section, it consists of a series of transparent hyaline layers with a very hard consistency.It measures about 12 cm long and 0.5 cm external diameter.Sometimes, they have attached anemones or serpulid tubes.

Family Eunicidae
Eunice megabranchia.The specimens were found inside the oscula of sponges and a tube with the specimen was found inside a sponge attached to a tube of the ampharetid Shistocomus hiltoni.

Family Fauveliopsidae
Fauveliopsis rugosa.Members of the genus Fauveliopsis have been found inside shells of mollusks and tubular tests of foraminifera (Petersen 2000).In the present study, F. rugosa was found inside shells of the scaphopods Fissidentalium megathyris and Rhabdus dalli, surrounded by mud.

Family Ampharetidae
Paramage scutata.The tube consists of an inner hyaline layer covered with mud, conically shaped, with incrustations of large foraminifera.The animal occupies 1/3 to 1/2 the length of the tube.
Ampharete acutifrons.The tube is a hard mucoid inner layer externally covered with compact mud.It is thick (about 1.5 cm external diameter) and tapers proximally.The animal occupies about 1/7 of the tube length.
Ampharete arctica.The tube was described by Hartman (1969) as long, tapering proximally, externally covered with fragments of algae, small sticks and debris.Most of the tubes found in the present study are covered with mud, and are similar to those described by Hartman (1969), but specimens were also found in tubes constructed with sand with bands of algae or debris, similar to typical onuphid tubes.
Amphicteis scaphobranchiata.This species builds tubes which are up to 25 cm long and about 1 cm external diameter, with a thick mucoid inner layer covered with ring-like compact mud of different colour.The tubes taper proximally and the animal occupies about 1/3 its length.
Egamella quadribranchiata.The tube is thin, made on a mucoid layer covered with bands of mud and fine sand and foraminifera attached to the outer surface.Animals occupy about 1/6 of the tube.
Melinna exilia.The tubes are made of mud, with an external diameter of about 0.3 cm.
Melinnampharete eoa.This species builds tubes that are up to 30 cm long and about 0.2 cm external diameter made of fine sand and mud.Animals occupy 1/5 to 1/10 of tube length.M. eoa has been reported in deep-water of the Northwest Pacific (Hartman 1960), thus this is the first record of this species in the Gulf of California.
Mexamage corrugata.This species has a tube about 1 cm external diameter with a mucoid layer covered with compact mud.
Schistocomus hiltoni.Chamberlin (1919b) described the tube of this species as 3.3 cm long, with the wall thickened by the adhesion of fine particles of sand, shell fragments, etc. Hartman (1969) described the tube as having a mucoid inner layer, externally covered with sticks set crosswise.The tubes found in the present study are about 15 cm long and about 1 cm external diameter, and the animal occupies about 1/10 the length.Some tubes have attached fragments of sponges and foraminifera.
Two species of the ampharetid genera Amage and Samytha have not been reported from the Gulf of California, and their detailed description will be reported elsewhere.Five ovigerous females of Amage sp. were collected at depths between 830-850 m.They differ from the six species previously reported by Hartman (1969) and Fauchald (1972) from the Gulf of California and northeast Pacific.The specimens have 14 thoracic segments, and setigers one to three are asetigerous (as A. anops, but different from the other species).They have eleven thoracic segments with notosetae and neuropodial uncini, two pairs of short branchiae (different from A. longibranchiata, which has long branchiae), ten abdominal setigers (as A. scutata and A. sculpta and different from A. delus (=perfecta), A. arieticornuta and A. anops), notopodia with notopodial lobes (as A. arieticornuta and A. anops), and prostomium trilobed (as A. arieticornuta and A. anops and different from A. delus and A. longibranchiata, which is bifid).The tubes are thick and mudwalled (as A. anops and different from A. arieticornuta).
Fourteen individuals of Samytha sp. were collected at depths of 850-870 m.They have three pairs of smooth branchiae; 17 thoracic setigers of which 14 are uncinigerous and seven to eight abdominal setigers.The prostomium is trilobed and paleae are absent.The specimens differ from the two species reported from California (Hartman 1969) in the number of abdominal setigers (S. californiensis with 20 and S. sexcirrata with 13).The tubes (about 55 cm long) are covered with mud and have attached anemones and foraminifera.The animal occupies about 1/7 part of the tube.

DISCUSSION
Few studies about deep-water polychaetes from the Gulf of California or adjacent areas have been performed, thus results found here are a contribution to their knowledge.This study comprises a list of polychaete taxa collected between 732 and 2 250 m depth, most of them previously collected and described by other authors.Nevertheless, new distribution and depth information is provided.All the species determined at the specific level found in this study have been previously reported for the Gulf of California or adjacent areas except for the pilargid A. hartmanae and the ampharetid M. eoa, which constitute new distribution records.New depth records are provided for E. cf.dilatae, E. sanguinea, S. gracilior, H. johnsoni, A. hartmanae, and P. ambigua.
In order to facilitate further taxonomic studies, the descriptions of the tubes or other protective structures, which had not been previously mentioned in the literature are provided for M. cristata, A. fissurata, E. megabranchia, P. scutata, A. acutifrons, A. scaphobranchiata, E. quadribranchiata, M. exilia, M. eoa, and M. corrugata This study also includes new descriptions of the tubes of P. limicolus, F. rugosa, A. arctica, and S. hiltoni, which differ from previous descriptions.
The descriptions of ampharetids belonging to the genera Amage and Samytha and comparisons with species reported from adjacent areas suggest that they are probably undescribed species.
Based on the number of taxa found during this study, the Karling dredge was more effective than the benthic sledge for collecting polychaetes inhabiting soft bottom, since it is able to collect species representing both, infauna and epifauna, while the benthic sledge only collects mostly large specimens from the epifauna.Moreover, the smaller mesh used for sieving sediments collected with the Karling dredge allowed the capture of smaller animals.

ACKNOWLEDGMENTS
This study is part of the project CONACyT number 31805-N with support from PAPIIT-IN217306-3.I want to thank Michel Hendrickx, director of the projects, for his advice and review of the manuscript.Collection of samples was performed thanks to the crew members of the R/V "El Puma", students and technical staff from the Mazatlan Marine Station (Instituto de Ciencias del Mar y Limnología, UNAM).I am especially grateful to Arturo Toledano, José Salgado, Héctor Nava, Benjamín Yáñez, Ernesto Sánchez and Alejandro Nava for their help during sampling.Thanks are also given to Leslie Harris, Kristian Fauchald, Sergio Salazar and Luis Carrera for their help in identification of dubious polychaete specimens.Arturo Toledano identified the scaphopods F. megathyris and R. dalli.

TABLE 1
Position and sampling depth range of the stations where polychaetes were collected