INTRODUCTION

The worms (polychaetes and sipunculids) inhabiting the coral reefs of the Gorgona National Natural Park (Gorgona) (Figure 1) in Colombia are poorly known, mainly due to the difficulty of direct observation given the habitats they use or to the difficulty of collecting these animals. There are few studies (e.g. ^{Cantera et al., 2003}; ^{Londoño-Cruz et al., 2003}) that have mentioned some of these organisms, hence, only a few species have been identified. Some worms are considered borers (^{Hutchings, 1986}), i.e. they penetrate (by different means) the substrate (e.g. coral) to dwell in a safe refugium. The galleries produced may weaken the substrate hardness and hence make it more fragile and prone to break; when empty these galleries may also serve as openings for the colonization of other boring species (e.g. bivalve mollusks) (^{Londoño-Cruz et al., 2003}), which increases coral destruction.

Figure 1 Location of Gorgona Island in the TEP and the two coral reefs: Playa Blanca and La Azufrada, from which worms were collected. 

Gorgona (2.9689 °N-78.1819 °W), along with Gorgonilla islet, is the largest insular territory on the Colombian Pacific coast. This island is ~30 km from the closest mainland point (^{Zapata, 2001}; ^{Londoño-Cruz, et al., 2003}; ^{Giraldo, 2012}). Environmental conditions are marginal to coral reef formations. The mean annual precipitation is 8000 mm with concomitant low salinities that vary between 29 (during March) and 31 (during September). Water temperature varies annually and is affected by the ENSO cycle, reaching highs of 33 °C during El Niño and lows of 18 °C during La Niña. Tides are semidiurnal with a range of ~4.5 m. Finally, the concentration of total dissolved solids is relatively high, which is reflected in reduced water transparency (low visibility), this varies around 8 m year-round, with extremely low values during periods of heavy rain (^{Prahl and Erhardt, 1985}; Zapata, 2001; ^{Londoño-Cruz et al., 2003}; ^{Giraldo et al., 2008}). Regardless of these conditions, Gorgona holds some of the most developed and diverse coral reefs in the southern reach of coral reef distribution in the TEP (^{Zapata, 2001}; ^{Londoño-Cruz, et al., 2003}; Zapata and Vargas-Ángel, 2003; ^{Giraldo et al., 2008}).

The largest coral reefs of Gorgona, Playa Blanca and La Azufrada (9.8 and 9.4 ha, respectively), are located on the lee (southeastern side) of the island. These reefs are young and shallow (^{Zapata, 2001}; ^{Giraldo et al., 2008}), and are dominated by Indopacific coral species (Zapata and Morales, 1997; ^{Zapata, 2001}). Playa Blanca is formed by two reef patches, the smallest of which is located to the north; in turn, La Azufrada is north to Playa Blanca (^{Prahl and Erhardt, 1985}; ^{Zapata, 2001}) (Figure 1). These reefs show the typical zonation pattern of fringing coral reefs, with a navigation channel, followed by the back-reef, where live coral cover is less than 50%; the reef-flat, the reef-front, where live coral cover is highest, reaching more than 80 %, and the reef-slope, where live coral cover is as low as 20 % and there is abundant coral rubble (Prahl and Erhardt, 1985; ^{Díaz et al., 2000}; ^{Zapata, 2001}). Although coral richness in Gorgona is the highest in the Colombian Pacific, there is a dominance of corals of the genus Pocillopora (Prahl and Erhardt, 1985; ^{Zapata, 2001}). Given the importance of coral reef ecosystems, the scarcity in knowledge regarding worms in the Pacific coast of Colombia, and that certain species of worms may act as borers of coral substrates, the main purpose of this document was to identify the members of the boring worms associated to coral reefs of Gorgona Island (Colombian Pacific).

MATERIALS AND METHODS

Branches of Pocillopora spp. colonies, with no signs of bioerosion, were collected and shaped into similar-sized cylinders (Experimental Units: EUs), using a handheld grinder. Each EU was drilled in one of the ends to anchor a 1.59 mm diameter stainless steel L-shaped rod using epoxy resin. Besides, larger (6.35 mm diameter x 2 m long) stainless steel rods were hammered, leaving around 50 cm outside, into the reef framework. The EUs were tied (using cable ties) to this portion of the rod (one EU per rod). Five EUs were randomly deployed along each reef zone of each reef and left there during one of five different exposure periods that ranged between 6 and 18 months (with 3 month intervals). In this manner, a good spatial and temporal representation was achieved. All EUs (n=200) were deployed the same day (2016/02/11). Once the exposure period ended for an EU, it was collected, stored in a plastic container with 10% formalin, and taken to the lab. All fouling was removed from the EU surface. After that, each EU was carefully fragmented using locking pliers to extract all organisms dwelling inside the coral matrix. All worms (polychaetes and sipunculids) were identified to the lowest taxonomic level possible using dichotomic keys (^{Cutler, 1994}; ^{de León-González et al., 2009}). Besides, original descriptions available in the Biodiversity Heritage Library were reviewed. Finally, all identified species were stored in the Reference Collection of Marine Organisms (CROM) of the Department of Biology at the Universidad del Valle, Cali (Colombia).

RESULTS

A total of 571 worm specimens (polychaetes + sipunculids) were collected (Table 1). These worms were allocated in 21 species: 18 polychaetes and 3 sipunculids (see Figure 2 for an example of some of the collected species). Polychaetes comprise 10 families and sipunculids comprise 2. New records are marked with superscripts as follows: ¹for Gorgona coral reefs only, ²for PNN Gorgona, and ³for the Colombian Eastern Tropical Pacific. The consulted literature for each species is listed right below the species name. The material examined presents the batch code of the CROM. All information related to distribution was obtained from the World Register of Marine Species (WoRMS, 2019). Finally, a brief discussion is added only to species that match original descriptions but differ in certain characters.

Table 1 Total number of specimens of each species from each coral reef and reef zone (BR: Back-reef, RP: Reef-flat, RF: Reef-front, and RS: Reef-slope) collected in Gorgona Island (Colombian ETP) during the five different exposure periods. 

Figure 2 Six of the most common species of worms found in Gorgona Island's coral reefs. Polychaetes: A) Euratellasalmacidis. B) Dodecaceria laddi. C) Dipolydora commensalis. D) Syllis gracilis. Sipunculids: E) Aspidosiphon (Aspidosiphon) cf. elegans. F) Phascolosoma (Phascolosoma) cf. perlucens. 

Annelida

Class Polychaeta

Family Amphinomidae Lamarck, 1818

Genus Chloeia Lamarck, 1818

Chloeia entypa ^{1Chamberlin, 1919}

Chloeia entypa:^{Chamberlin, 1919}; ^{Kudenov, 1975}; ^{Fauchald, 1977}; ^{Prahl et al., 1979}; ^{Laverde-Castillo, 1986}; ^{Hernández-Alcántara y Solís-Weiss, 1991}; ^{Salazar-Vallejo y Londoño-Mesa, 2004}; Valencia et al., 2014.

Material examined: APN0001.

Distribution: Pacific (Mexico) and TEP.

Discussion: The specimen matched the description by ^{Kudenov (1975)}, who mentions the presence of serrate and bifurcate neurosetae in the posterior part of the body. Although, ^{de León-González et al. (2009)} mention that lateral antennae are pigmented. This pigmentation was not observed, probably because it was lost due to the fixation method used. It is highly probable that the specimen is a juvenile due to the number of segments present (14).

Family Cirratulidae Ryckholt, 1851

Genus Dodecaceria Örsted, 1843

Dodecaceria fewkesi^{Berkeley & Berkeley, 1954}

Dodecaceria fewkesi:^{Berkeley y Berkeley, 1954}; ^{Salazar-Vallejo y Londoño-Mesa, 2004}.

Material examined: CIR0026, CIR0027, CIR0028, CIR0029.

Distribution: South of California, Coos Bay.

Genus Dodecaceria Örsted, 1843

Dodecaceria laddi ^{1Hartman, 1954}

Dodecaceria laddi:^{Hartman, 1954}; ^{Gibson, 1978}; ^{White, 1980}; ^{Abd-Elnaby, 2009}; ^{Magalhaes y Bailey-Brock, 2013}.

Material examined: CIR0030, CIR0031, CIR0032,

CIR0033, CIR0034, CIR0035.

Distribution: Kaneohe Bay (Hawaii), Marshall Islands, Pulo Boenda (Sumatra).

Discussion: The specimens matched the description by ^{Hartman (1954)}; however, it was not possible to observe the limbo that appears in the setae of the first seven segments (^{Hartman, 1954}, Figure 177H). This might be due to the position of the setae.

Genus Timarete Kinberg, 1866

Timarete luxuriosa ³ (^{Moore, 1904})

Timarete luxuriosa:^{Moore, 1904}; ^{Hernández-Alcántara y Solís-Weiss, 1991}; ^{Hernández-Alcántara, 2003}; ^{Salazar-Vallejo y Londoño-Mesa, 2004}; ^{Choi et al., 2018}.

Material examined: CIR0036, CIR0037.

Distribution: Gulf of California, Mexican Pacific, TEP.

Family Dorvilleidae ^{Chamberlin, 1919}

Genus Dorvillea Parfitt, 1866

Dorvillea rubra ^3, (Grube, 1856)

Dorvillea rubra: Grube, 1856; ^{Perkins, 1998}; ^{Salazar-Vallejo y Londoño-Mesa, 2004}; ^{Hernández-Alcántara et al., 2014}.

Material examined: DOR0001, DOR0002, DOR0003, DOR0003, DOR0004, DOR0005, DOR0006.

Distribution: Caribbean, Florida, Gulf of Mexico, TEP.

Family Eunicidae Berthold, 1827

Genus Eunice Cuvier, 1817

Eunice cedroensis ^{3Fauchald, 1970}

Eunice cedroensis:^{Fauchald, 1970}; ^{Salazar-Vallejo y Londoño-Mesa, 2004}.

Material examined: EUN0035, EUN0036, EUN0037, EUN0038.

Distribution: Gulf of Mexico, TEP.

Discussion: Although the specimens matched the description by ^{Fauchald (1970)}, the setae illustrated in Figure E (Plate 2) were not observed.

Genus Lysidice Lamarck, 1818

Lysidice ninetta ^{1 Audouin & H Milne Edwards, 1833}

Lysidice ninetta:^{Audouin y Milne, 1833}; ^{Monro, 1928}; ^{Fauchald, 1970}, 1977; ^{Laverde-Castillo, 1986}; ^{Hernández-Alcántara y Solís-Weiss, 1991}; ^{de León-González et al., 1993}; ^{Gómez et al., 1997}; ^{Cantera et al., 1999}; ^{Salazar-Vallejo y Londoño-Mesa, 2004}.

Material examined: EUN0040, EUN0041, EUN0042

Distribution: TEP, Colombia, Gulf of Mexico, Cuba, Belize, Belgium, Caribbean Sea, France, Greece, Jamaica, New Zealand, Red Sea, Spain, United Kingdom.

Genus Palola Gray in Stair, 1847

Palola paloloides ² (^{Moore, 1909})

Palola paloloides:^{Moore, 1909}; ^{Fauchald, 1970}, 1992; ^{Kudenov, 1975}; ^{Laverde-Castillo, 1986}; ^{Hernández-Alcántara y Solís-Weiss, 1991}; ^{Salazar-Vallejo y Londoño-Mesa, 2004}.

Material examined: EUN0043.

Distribution: San Diego, California; TEP, Colombian Pacific.

Family Flabelligeridae de Saint-Joseph, 1894

Genus Semiodera^{Chamberlin, 1919}

Semiodera cariboum ³ (^{Grube, 1859})

Semiodera cariboum:^{Hartman, 1956}; ^{Salazar-Vallejo y Londoño-Mesa, 2004}.

Material examined: FLA0006.

Distribution: Antilles, Caribbean Sea, Gulf of Mexico, TEP.

Discussion: ^{Salazar-Vallejo and Londoño-Mesa (2004)} register this as a dubious species for the TEP (S. cariboa); however, the observed specimen matched the descriptions by Grube (1858) and ^{de León-González et al. (2009)}.

Family Nereididae Blainville, 1818

Genus Eunereis Malmgre, 1865

Eunereis cf. longipes ^{3Hartman, 1936}

Eunereis cf. longipes:^{Hartman, 1936}; ^{Salazar-Vallejo y Londoño-Mesa, 2004}.

Material examined: NER0001, NER0002, NER0003, NER0004.

Distribution: California, TEP.

Discussion: Observed specimens matched the description by ^{Hartman (1936)}; however, although having notopodial laminar homogonfous falcigerous ending in an acute tip (^{Hartman, 1936}, Figure 53), the falcigerous lamina is longer and the tooth more acute. Likewise, in Figure 53F (^{Hartman, 1936}), teeth can be seen along the whole setae sheet, while in the Colombian specimens, the teeth were only observed in the distal portion of the setae and the first tooth is longer and surrounds the falcigerous tooth.

Family Phyllodocidae Örsted, 1843

Genus Eteone Savigny, 1822

Eteone cf. pacifica ^{3Hartman, 1936}

Eteone cf. pacifica:^{Reish, 1963}; ^{Salazar-Vallejo y Londoño-Mesa, 2004}.

Material examined: PHY0008, PHY0009.

Distribution: Friday Harbor (San Juan Island), TEP.

Discussion: Observed specimens matched the description by ^{de León-González et al. (2009)}; however, ventral and dorsal cirri differ in longitude and lack a well-defined auricular shape. This can be due to slight changes in soft tissues during fixation.

Family Sabellidae Latreille, 1825

Genus Euratella^{Chamberlin, 1919}

Euratella salmacidiss (^{Claparède, 1869})

Euratella salmacidis:^{Claparède, 1869}; ^{de León-González et al., 1993}; ^{Salazar-Vallejo y Londoño-Mesa, 2004}.

Material examined: SAL0005, SAL0006, SAL0007, SAL0008, SAL0009, SAL0010.

Distribution: Mediterranean Sea, North Atlantic Ocean, Spain, TEP.

Family Spionidae Grube, 1850

Genus Dipolydora Verril, 1881

Dipolydora commensaliss (^{Andrews, 1891})

Dipolydora commensalis:^{Andrews, 1891}; ^{Hartman, 1941}; ^{Salazar-Vallejo y Londoño-Mesa, 2004}.

Material examined: SPI0011, SPI0012, SPI0013, SPI0014, SPI0015, SPI0016.

Distribution: North Carolina, Japan Sea, North Atlantic Ocean, TEP.

Genus Polydora Bosc, 1802

Polydora ciliata ³ (Johnston, 1838)

Polydora ciliata: Johnston, 1838; ^{Hartman, 1941}; ^{Mustaquim, 1986}; ^{Salazar-Vallejo y Londoño-Mesa, 2004}.

Material examined: SPI0019.

Distribution: United Kingdom, French, Gulf of Naples, Black Sea, Gulf of Aden, North Atlantic Ocean, Belgium, Bay of Fundy, English Channel, Greece, Ireland, Madagascar, Mozambique, Netherlands, North Sea, Red Sea, Spain, Ukraine, TEP.

Discussion: The observed specimen matched the descriptions by Johnston (1838) and ^{Mustaquim (1986)}, with the only exception that the four eyes reported by ^{Mustaquim (1986)} were not observed in our specimen.

Family Syllidae Grube, 1850

Genus Cicese^{Díaz-Castañeda & San Martín, 2001}

Cicese cf. sphaerosylliformis ^{3 Díaz-Castañeda & San Martín, 2001}

Cicese cf. sphaerosylliformis:^{Díaz-Castañeda y San Martín, 2001}; Díaz-Castañeda et al., 2005; ^{Hernández-Alcántara et al., 2008}.

Material examined: SYL0011.

Distribution: Pacific Coast of Baja California (Mexico).

Discussion: The observed specimen matched the description in ^{Díaz-Castañeda and San Martín (2001)}, but the distance between distal and basal falcigerous teeth is shorter than the one presented in their illustration. Besides, in the simple setae, there are no teeth present as shown in the illustration by ^{Díaz-Castañeda and San Martín (2001}, Figure 5G, 5H, 5I).

Genus Dentatisyllis Perkins, 1981

Dentatisyllis cf. carolinae ¹ (^{Day, 1973})

Dentatisyllis cf. carolinae:^{Day, 1973}; ^{Perkins, 1980}; ^{de León-González et al., 2009}.

Material examined: SYL0012, SYL0013.

Distribution: Gulf of Mexico, North Atlantic Ocean.

Discussion: ^{de León-González et al. (2009)} register a trepan with approximately 10 teeth, while in our specimens, only 8 teeth were observed. For the articulated dorsal cirri, they mention 30 segments, while in our specimens we observed only approximately 20 segments. Finally, the simple setae illustrated by ^{Day (1973}, Figure 4E) and ^{Perkins (1980}, Figure 38A) were not observed in our specimens.

Genus Syllis Lamarck, 1818

Syllis gracilis ^{1Grube, 1840}

Syllis gracilis:^{Grube, 1840}; ^{Monro, 1933}; ^{Fauchald, 1977}; ^{Laverde-Castillo, 1986}; ^{Salazar-Vallejo et al., 1990}; ^{Estape y San Martín, 1991}; ^{Hernández-Alcántara y Solís-Weiss, 1991}; ^{de León-González et al., 1993}; ^{Bastida-Zavala, 1995}; ^{Capa et al., 2001}; Hernández-Alcántara et al., 2003; Salazar-Vallejo y Londoño-Mesa, 2004.

Material examined: SYL0018, SYL0019, SYL0020, SYL0021, SYL0022.

Distribution: Gulf of Naples, Mediterranean Sea, Black Sea, Chilean part of the South Pacific Ocean, Djiboutian region of the Gulf of Aden, Djiboutian region of the Red Sea, Antilles, West Africa Coast, Gulf of Mexico, Caribbean Sea, Trinidad and Tobago, Spain, United Kingdom, Italy, Ireland, Greece, TEP.

Genus Syllis Lamarck, 1818

Syllis prolifera ³ Krohn, 1852

Syllis prolifera:^{López et al., 1997}; ^{Capa et al., 2001}; ^{Salazar-Vallejo y Londoño-Mesa, 2004}.

Material examined: SYL0017.

Distribution: Antilles, Black Sea, Djiboutian part of the Gulf of Aden, Djiboutian part of the Red Sea, Caribbean Sea, Cuba, Gulf of Mexico, Italy, Madagascar, New Zealand, North Atlantic Ocean, Spain, Trinidad and Tobago, United Kingdom, Greece, TEP.

Sipuncula

Class Phascolosomatidea

Family Aspidosiphonidae Quatrefages, 1865

Genus Aspidosiphon Diesing, 1851

Aspidosiphon (Aspidosiphon) cf. elegans ³ (^{Chamisso & Eysenhardt, 1821})

Aspidosiphon (Aspidosiphon) cf. elegans:^{Chamisso y Eysenhardt, 1821}; ^{Cutler, 1994}.

Material examined: ASP0001, ASP0002, ASP0003,

ASP0004, ASP0005, ASP0006, ASP0007.

Distribution: Mediterranean Sea-Eastern Basin, Aegean Sea, Gulf of Mexico, Madagascar, North Atlantic Ocean, Red Sea, South Pacific Ocean.

Family Phascolosomatidae Stephen & Edmonds, 1972

Genus Phascolosoma Leuckart, 1828

Phascolosoma (Phascolosoma) cf. nigrescens ³ (Keferstein, 1865)

Phascolosoma (Phascolosoma) cf. nigrescens:^{Fisher, 1952}; ^{Cutler, 1994}.

Material examined: PHS0001, PHS0002, PHS0003. Distribution: Madagascar, Red Sea, Gulf of Mexico.

Phascolosoma (Phascolosoma) cf. perlucens Baird, 1868

Phascolosoma (Phascolosoma) cf. perlucens:^{Cutler, 1994}; ^{Cantera et al., 2003}; ^{Kawauchi y Giribet, 2010}.

Material examined: PSH0004, PSH0005, PSH0006, PSH0007, PSH0008, PSH0009, PSH0010.

Distribution: Madagascar, Gulf of Mexico, Gorgona Island (Colombia).

Discussion: The observed specimens matched the description by ^{Kawauchi and Giribet (2010)}; however, we use cf. because, according to the aforementioned authors, there is a need for molecular analyses to discern this specie within the genus since morphological characters are highly variable and not fully useful for the correct identification of species.