New records of polychaetes (Annelida: Polychaeta) from three locations of Oaxaca, Mexico Nuevos registros de poliquetos (Annelida: Polychaeta) de tres localidades de Oaxaca, México

Introduction: The knowledge of polychaetes from Oaxaca, Mexico, is represented by 41 families and 241 species, nevertheless, 148 species are considered questionable. The majority of taxonomic studies of polychaetes in Oaxaca have taken placed on estuarine zones or commercial ports, sidelining other marine ecosystems. Objective: To identify the polychaeta-fauna from three different marine ecosystems in Oaxaca, Mexico. Methods: Specimens analyzed came from the Sección de poliquetos de la Colección Científica at the Laboratorio de Sistemática de Invertebrados Marinos, Universidad del Mar. The material deposited in the collection was collected between 2007-2017; additionally, new collect were realized in 2017. For each locality, the family and species richness were estimated using the accumulation function of linear dependence model. Results: One hundred lots and 273 specimens were revised. Seventy-one taxa, belonging to 47 genera and 21 families were identified, only twenty of these taxa are confirmed species (28 %). Chacahua Lagoon had the highest richness and relative abundance with 37 taxa and 149 specimens, Agua Blanca was identified 21 taxa and 92 specimens, and from San Agustín 19 taxa and 32 specimens. Sabellariidae had the highest relative abundance (58 specimens), while Phyllodocidae presented the highest species richness (12 species). Conclusions: This study adds 75 new records of taxa of polychaetes to the coast Oaxaca, which increase the knowledge in this animal group, now represented by 304 species, belonging to 154 genera and 42 families.

The aim of this study was to identify the polychaetes from three different marine ecosystems from Oaxaca, Mexico. A checklist of polychaetes species recorded from Chacahua Lagoon, Agua Blanca and San Agustín, is included.

Materials and methods
Specimens analyzed came from the Sección de poliquetos de la Colección Científica (OAX-CC-249-11) at the Laboratorio de Sistemática de Invertebrados Marinos (LABSIM), Universidad del Mar (Puerto Ángel, Oaxaca, Mexico). This material was collected between 2007-2017 from three locations in Oaxaca, Mexican Pacific. Chacahua Lagoon (15°57'57" N -97°40'38" W), a coastal lagoon belonging to Lagunas de Chacahua National Park; Agua Blanca (15°43'58" N -96°48'50" W), an intertidal rocky shore; and San Agustín (15°41'09" N -96°14'05" W), a bay with a wide area of coral reef. Specimens were fixed in 10 % formalin solution and preserved in 70 % ethanol solution. In contrast, the material collected in 2017 (obtained through snorkeling in the intertidal zone to 3 m depth), was fixed and preserved in 96 % ethanol solution. The new specimens collected and all of the material examined was separated in glass vessels and labeled, and deposited in the Sección de poliquetos of LABSIM. The identification of the polychaetes was made using the keys of de León-González et al. (2009); it was also corroborated with specialized literature for each family. The checklist is shown in alphabetical order. Family and species richness by location was obtained using the accumulation function of linear dependence model (Moreno, 2001). The expected richness was estimated as the number of families or species, considering the sampling effort as number of sampling event for locality. The analyses were performed with EstimateS 9 (Colwell, 2013) and Statistica 8.0 (StatSoft, 2007) software. To avoid an overestimation of the values of richness, damaged polychaetes, juveniles or specimens with a non-defined taxonomic status were removed prior to the analysis.

Results
A total 100 lots and 271 specimens were revised. Seventy one taxa belonging to 47 genera and 21 families were recorded (Table 1). Among these records, 20 are confirmed species (28 %), 19 are close to nominal species due to present morphological peculiarities or type locality distant from Oaxaca (27 %), 14 have unclear systematic status since are incomplete, damaged or juvenile specimens (20 %), and 18 are possible new species (25 %) which will be formally described by the authors in upcoming papers. One family (Chaetopteridae), 18 genera and 37 species are new records for the coast of Oaxaca. Twenty-six species are new records for the Mexican Pacific. Depth in m = meters, SABI = Sabellariidae aggregation, Q = questionable record, ND = no data. Symbols: = possible new species, • = record. The number of specimens is indicated between parentheses.
In general, Sabellaridae presented the highest abundance with 58 specimens (Fig. 1A, Fig. 2E-F), perhaps due to the fact that its members are gregarious polychaetes. Phyllodocidae was the richest family with 12 species, followed by Syllidae with eight, Nereididae with seven and Spionidae with six species. As results for each site, Chacahua Lagoon had the highest richness and abundance with 37 taxa and 149 specimens. In Agua Blanca 21 taxa and 92 specimens were identified, and from San Agustín, 19 taxa and 32 specimens. Nereididae was the family with highest richness (six species) in Agua Blanca, whereas Sabellariidae presented the highest relative abundance (58 specimens) (Fig. 1A). In Chacahua Lagoon, Phyllodocidae was the richest family (10 species) and Spionidae had the highest abundance (53 specimens) (Fig. 1B). In San Agustín, Eunicidae had the highest richness and abundance (four species, seven specimens) (Fig. 1C). Lumbrineridae, Chaetopteridae, Capitellidae and Sabellidae had the lowest abundance in these locations, with only one specimen each one.
To avoid an overestimation of the values of the richness, the only specimens removed were Terebellinae sp. in Agua Blanca and Phyllodocidae sp. epitocus stage in San Agustín, since these could be duplicate data (Lanicola cf. carus and Phyllodoce sp., respectively). With the accumulation function, the expected richness was 14 families (R = 0.999, R 2 = 99.998 %, asymptote = 13.92, b = 0.141) and 44 species for Agua Blanca (R = 1.000, R 2 = 100 %, asymptote
In Oaxaca, before this study, there were only 20 recorded species of polychaetes from Chacahua Lagoon, Agua Blanca, and San Agustín (Hartman, 1944(Hartman, , 1950(Hartman, , 1961Ruiz-Cancino et al., 2011;Salazar-Vallejo, 2012;Cruz-Gómez & Bastida-Zavala, 2018). With this work, this has increased to 71 species, and 75 new records were added: 21 in Agua Blanca, 19 in San Agustín and 35 in Chacahua Lagoon. Particularly, the study by Gómez et al. (1997) found the highest values of richness (36 species) in coralline zone of La Entrega, Oaxaca. In contrast, among the three locations of study, the highest values of abundance (149 specimens) and richness (37 species) were found in Chacahua Lagoon; this might be due to the diversity of microhabitats studied in this locality: rocky zone, mangrove, sand and muddy zone. On the other hand, the coralline zone of San Agustín showed the lowest abundance (32 specimens) and richness (19 species); however, this location also presented the lowest sampling effort (Fig. 1D). The Polychaeta-fauna in Chacahua Lagoon, Agua Blanca and San Agustín only match in 9 % of their composition, which are six families and eight taxa (Chrysopetalum elegantoides, C. occidentale, Paleaonotus sp., Dorvillea cf. cerasina, Eunice chicasi, Eulalia sp., Hydroides brachyacantha, and Lanicola cf. guillermoi). This indicates that these three locations present particular environmental conditions with different types of marine biota. On the other hand, the results of this work coincide with Gómez et al. (1997) (Fig. 2). Ethical statement: authors declare that they all agree with this publication and made significant contributions; that there is no conflict of interest of any kind; and that we followed all pertinent ethical and legal procedures and requirements. All financial sources are fully and clearly stated in the acknowledgements section. A signed document has been filed in the journal archives.