New records of native and non-indigenous polychaetes ( Annelida : Polychaeta ) in the Galapagos Islands

The biofouling community on Santa Cruz and Baltra Islands, Galapagos, was surveyed in 2016 based on samples from settlement plates deployed in 2015 and 2016 at three different sites. We report numerous new records for the Galapagos fauna: one novel family (Opheliidae), nine novel genera, and 15 novel species records were documented in a total of seven families. Six introduced species were found, the syllid Myrianida pachycera, the sabellids Branchiomma bairdi, Branchiomma sp. and Pseudobranchiomma schizogenica, and the serpulids Hydroides elegans, Hydroides sanctaecrucis, along with one cryptogenic species, the spionid Dipolydora armata. Non-native species come from either the warm waters of the Western Atlantic or Indo-West Pacific Oceans.


Introduction
The polychaete annelid fauna of the Galapagos Islands is remarkably poorly known.Blake (1991) summarized all known polychaete records.The earliest collections appear to be those from the Swedish frigate Eugenie expedition of the 1850s, followed by other research vessel visits in the early decades of the 1900s.Between 1933 and1938 the Velero expeditions of the Allan Hancock Foundation resulted in extensive collections, not all of which have been worked up (Blake 1991).Surprisingly little work ensued for the rest of the 20 th century (Blake 1991).Since Blake's excellent summary that listed 192 species, Bastida-Zavala and ten Hove (2003), Nishi et al. (2009) and Blake (2017) added Hydroides ochotereana Rioja, 1941, five species of Chaetopterus, two species of Mesochaetopterus, and Naineris setosa (Verrill, 1900).We have found no reports of prior collections of polychaetes from the biofouling communities of Galapagos ports and harbors.
We report here new records of non-indigenous, cryptogenic, and presumably native polychaetes from Santa Cruz and Baltra Islands.No previous work on Galapagos polychaetes has reported the presence of nonindigenous species (NIS).

Materials and methods
Polyvinylchloride (PVC) settlement plates (14 × 14 cm) were suspended horizontally 1 m below mean low water to survey for both NIS and native species in February 2015 and January 2016.Some plates were caged with a 5 mm mesh for predator-exclusion studies but most plates were uncaged; analysis of exposed versus caged experimental panels will be reported elsewhere.In some cases, specimens were collected directly from the rope hanging the plates.Plates were deployed on Santa Cruz Island at two stations, Puerto Ayora's Main Passenger Dock (0°44′52.04″S;90°18′44.98″W)and in Franklin's Bay (0°45′18.72″S;90°18′45.56″W),and on adjacent Baltra Island (0°26′9.52″S;90°17′5.29″W)(Figure 1, Supplementary material Table S1).The plates were retrieved 14 and three months later in April 2016.Temperature and salinity at 1 m depth were measured with a YSI temperature-conductivity meter.Plates were transported in seawater and analyzed at the Charles Darwin Research Station's (CDRS) marine biological laboratory (BioMar) in Puerto Ayora.
All material was preserved in 95% ethanol, and specimens have been deposited in the CDRS invertebrate collections.

Water Parameters
In April 2016 at the Santa Cruz and Baltra sites, the temperature at 1 m depth ranged from 22.9 to 23.9 °C, and salinity ranged from 33 to 35.3 psu.

Systematic Account
We report numerous new records for the Galapagos fauna: one novel family (Opheliidae), nine novel genera, and 15 novel species records were documented in a total of seven families.

Order Phyllodocida
Family Syllidae Grube, 1850 Subfamily Autolytinae Langerhans, 1879 We report two new records in two genera in the Autolytinae for the Galapagos.
Material.Puerto Ayora (3 specimens, 25 April 2016, vial 232806, on caged plate 16465, deployed for 14 months).Taxonomic Remarks.A species with a distinct color patterns, dorsal cirri thick and digitiform.The morphology of our Galapagos material agrees with the detailed description in Nygren (2004).Distribution and remarks.A widespread Indo-West Pacific, to which region it is held to be native.It is considered to be introduced to the Hawaiian Islands and to the northern east Pacific coast, as well as to Florida (Carlton and Eldredge 2009).It could possibly be a complex of cryptic species, but to test this hypothesis molecular analyses are needed.Material.Puerto Ayora (1 specimen, 25 April 2016, vial 233528, on caged plate 30237 deployed for three months).Diagnosis.Anterior and posterior part of proventricle orange in living specimen (color lost in preserved material), eyes confluent, orange (Figure 2).Trepan in chaetiger 1, but the teeth were not sufficiently visible to count.Proventricle equal in length to 3-4 segments between chaetigers 6-9, with 30-35 rows of muscle cells.Taxonomic remarks.We refer the present material provisionally to Proceraea rubroproventriculata because of the characteristic proventicle color pattern (in the red-orange spectrum), but we are unable to verify the trepan teeth number (12 large, 12 small) considered distinctive for this species.Nygren (2004) noted that, "P.rubroproventriculata is most similar to P. paraurantiaca, P. filiformis and P. misakiensis, but may be separated from these taxa on its trepan with 12+12 teeth."Our Puerto Ayora material is neither P. paraurantiaca nor P. misakiensis, whose color patterns are distinct in the North East Atlantic and North West Pacific respectively (the color of P. filiformis from South West Pacific is not known).Distribution and remarks.Proceraea rubroproventriculata is an Atlantic species, known from Florida, USA to Paranaguá Bay, Brazil (Nygren 2004).If the Galapagos specimens prove to be this species, we would regard it as an introduction from the Atlantic.Westheide (1974) reported two Proceraea species from the Galapagos, the Atlantic species P. fasciata Langerhans, 1879(now P. madeirensis Nygren, 2004), and Proceraea sp. from Academy Bay, Santa Cruz Island.Westheide's description of this second Proceraea species was based upon preserved (and thus colorless) material; he reported similar difficulties in viewing the pharynx teeth, but nevertheless reported 11-12 teeth, with the middle teeth apparently shorter than the lateral teeth.Both Westheide's and our material probably represent an undescribed species, as may his P. madeirensis, which (unless introduced) would be unlikely to occur naturally in the tropical Eastern Pacific.
Order Sabellida Family Sabellidae Latreille, 1825 The family Sabellidae in Galapagos has been minimally investigated in the past.Blake (1991) noted that there was only one record of an identified sabellid, Acromegalomma quadrioculatum (Willey, 1905) (originally reported from the Galapagos in the 1930s as Branchiomma mushaensis Gravier, 1906, although Blake noted that the Galapagos specimens have never been reexamined).We identify three genera here, all new records for the Islands.

Diagnosis.
A small sabellid of a few millimeters in length, body with eight thoracic and five abdominal chaetigers, three pairs of radioles, radiolar skeleton with two rows of cells, radioles with external flanges and palmate membrane (Figure 3A).Eyes present in the peristomium but not visible in the pygidium; a pair of statocysts in the first chaetiger (Figure 3B).Thoracic superior chaetae, with varying but narrow hoods, and an inferior row of smaller, thinned bayonet chaetae.Thoracic uncini acicular, with teeth of unequal sizes in first arc above main fang.Abdominal uncini quadrangular, handles absent, toothed margin with a more or less enlarged basal fang.Abdominal neurochaetae needle-like, elongate.Taxonomic remarks.We are unable to resolve our material to species level.It may be a new species long been present but not detected earlier due to its small size.Distribution.Amphicorina species are known from the Mediterranean, the southwest Atlantic, and the Western and Eastern Pacific Oceans.shield, composed of avicular uncini with the crest surmounted by 2-3 rows of teeth.Radiolar eyes orange.The colour of the radiolar crown varied from brownish to orange, often with stripes in cream or dark brown.The colour of the body of live specimens varied from pale, yellow, olive green to brownish.Distribution and remarks.Branchiomma bairdi is a warm-water Western Atlantic species known from Bermuda and throughout the Caribbean to Panama (Keppel et al. 2015;Del Pasqua et al. 2018).It has been introduced to the Eastern Atlantic, to the Mediterranean Sea, to the Eastern Pacific (California to Panama) and to Australia (Keppel et al. 2018).It was found in 1998 on the Pacific coast of Panama (Capa and Lopez 2004), from where it may have been introduced to the Galapagos.It is a conspicuous component of benthic communities, largely in confined environments and areas degraded by anthropogenic impacts (Arias et al. 2013).Branchiomma bairdi appears to be abundant and well-established in the Galapagos.The identification was also confirmed from molecular analysis (Del Pasqua et al. 2018).

Branchiomma sp.
(Figure 5) Material.Franklin's Bay and Puerto Ayora (many specimens, 25 April 2016; two specimens were examined, collected in Puerto Ayora from vial 236733, on caged plate deployed for 12 months).Diagnosis.Dorsal collar with well-separated margins, dorsal lips with a distinctive white tip and about 1/3 as long as the radiole (Figure 5A).Ventral lappets well-developed triangular or overlapping with a distinctive internal orange spot that remains after preservation (Figure 5B).Crown united at the base by a low web, and 8-12 pairs of radioles on each side.Radioles have apinnulate tips and stylodes.Stylodes strap-like, radiolar eyes orange.The colour of the radiolar crown varied from olive green to white, often with yellow stripes.The colour of the body of live and preserved specimens is bright green.Distribution and remarks.Further studies are required to determine if this is a described or undescribed species; some specimens have been provided to Maria Capa for DNA analysis.This is likely an introduction and first record for the Galapagos.Material examined.Puerto Ayora and Franklin's Bay, 2016, building large colonies (many specimens; vial 233551 from caged plate 30273 deployed for three months; vial 233575 from uncaged plate 16607 deployed for 14 months; vial 233580 from caged plate 16462 deployed for 14 months).Diagnosis.Pseudobranchiomma schizogenica is a gregarious sabellid with a short body (Figure 6A, B).Our material matches the original description.Radioles with short, digitiform serrations (Figure 6C) along the entire radiolar length.No radiolar eyes.Lateral margins of collar oblique, covering anterior peristomial ring.Eleven pairs of radioles arranged in two semicircles.Eight pairs of short, digitiform serrations (6-9 pairs) along the entire length of radioles.Dorsal margins of collar not fused to faecal groove, peristomium exposed dorsally.Ventral lappets triangular, distally rounded, not overlapping.Five thoracic segments: thoracic uncini with four teeth.Body bright yellow in live specimens, anteriorly speckled with few purple spots.Radioles with four or more purple bands separated by orange and translucent bands (Figure 6D).Interramal eyespots purple, larger anteriorly, decreasing gradually towards posterior end.Distribution and remarks.Pseudobranchiomma schizogenica was recently described from "dock fouling" in shallow water in the southern Gulf of California.Capa and Murray (2016) have suggested that it may not be native to Mexico, given the discovery of other P. schizogenica populations or closely related clades widely distributed around the Pacific (including Australia and Hawaii).It would appear unlikely that this abundant, gregarious sabellid would have been overlooked in Western Mexico (including the Gulf of California) for decades prior to its detection and first collection in 2011 in Baja California Sur.Equally compelling is that among nearly 20 known species of Pseudobranchiomma, widely distributed in the Western Pacific and Indo-West Pacific as well as the Atlantic Oceans, P. schizogenica, is the only representative of the genus in the Eastern Pacific.Given its strong association with fouling communities, we concur that P. schizogenica is not native to the Eastern Pacific.

Genus Hydroides Gunnerus, 1768
Hydroides elegans and H. sanctaecrucis, treated below, are well-known introduced species; both appear to be undergoing major expansions from Panama to the Pacific Mexican coast (Bastida-Zavala et al. 2016, 2017).

Hydroides elegans (Haswell, 1883)
Eupomatus elegans Haswell 1883: 633, pl. 12, Figure 1 (type locality: Port Jackson, Australia).Hydroides elegans: Bastida-Zavala and ten Hove 2002: 164-166, Figures 35A-J  Taxonomic remarks.Our specimens agree in all details with the description in Bastida-Zavala and ten Hove (2003).Distribution and remarks.Widely distributed in tropical-to-warm temperate marine waters.It is presumed to be native to the Indo-Pacific.Of interest is that it appeared in our samples only at the Ecuadorian Navy floating dock on Baltra Island, where the panels were deployed, and where this species was found on ropes as well as on five different plates deployed for three months.Its apparent restriction, at least as of 2016, may be due to a direct introduction from the mainland to the naval base in the Galapagos.The distribution of Hydroides elegans is generally limited to polluted harbours and eutrophic lagoons, except in the type locality and a few other locations (ten Hove 1974; Bastida-Zavala 2008).Material.Franklin's Bay (1 specimen, 27 April 2016, vial 233681 from uncaged plate 16424, deployed for 14 months).Taxonomic remarks.The overall morphology and the operculum (Figure 7) agree with the descriptions in Bastida-Zavala and ten Hove (2003).Material.Many specimens retrieved on 28 April 2016 from Baltra, on many plates, cage and uncaged, exposed for 3 months.Diagnosis.Tube violet, with prominent longitudinal ridge.Anteriormost section of tube forms robust spine extending over opening of tube, usually this spine and opening are violet, pinkish or bluish in colour; lacking peristomes or alveoli.Opercular peduncle with wide wings.Operculum calcareous, circular or pear-shaped.Opercular surface bears three spines, emerging from dorsalmost part of opercular plate.Two latero-dorsal spines thin, with an additional 6-10 spinules and one small and thin basal branch; the medio-ventral third spine widely bifurcated.Distribution and remarks.Tropical Eastern Pacific.Baja California Sur (Mexico) to Panama and Colombia.Galapagos Islands (herein) common, and presumably native, in the Islands.Blake (1991) and all subsequent literature cited only one species of this genus in the Galapagos, misidentified as the Caribbean Spirobranchus giganteus (Pallas, 1766).We also found in the present survey an anomalous operculum of S. incrassatus (Figure 8), similar to that described for S. polycerus var.augenerii ten Hove, 1970, where the upper operculum is the oldest and the lower the youngest.
Material.Baltra (1 juvenile, 28 April 2016, vial 237624 from caged plate deployed for three months).Taxonomic remarks.Remarkably, this is the first record of the genus from the Galapagos, perhaps due to the lack of earlier collections in shallow biofouling habitats, although it is a taxon that should also be present in soft sediment habitats.Our material is a member of the Capitella capitata (Fabricius, 1780) complex, but it cannot be assigned to species at this time.Capillary chaetae on the first three chaetigers.This specimen is a juvenile with no genital chaetae, and a missing pygidium.Taxonomic remarks.We provisionally consider Capitella to be cryptogenic, based upon its biofouling habitat, and its treatment as cryptogenic in the Central (Carlton and Eldredge 2009) and Eastern Pacific (Cohen and Carlton 1995).Material.Baltra (3 specimens, 28 April 2016, from two different uncaged plates deployed for three months: vial 237608 from plate 30278; vial 237639 from plate 30290).Diagnosis.Prostomium short, rounded, two eyes, ventral groove present along the entire body, characteristic dorsal pigmentation with brown streaks and variable spots, branchiae absent.The lateral parapodial eyespots present are very distinct (Figure 10A, C) but another specimen has faintly lateral eyespots.Anal funnel with eight papillae: in one specimen they are long and more or less equal except for the ventral papillae, while another specimen has 6 small papillae and two ventral bigger of different shape, one pointed and one rounded (Figure 10B).The papillae in the present Galapagos material differ from the drawings of Japanese populations in Imajima and Gamo (1970).Distribution and remarks.There are no previous records of Opheliidae in the Galapagos, so this should be the first one.Polyophthalmus pictus is reported around the world as a nearly cosmopolitan species, suggesting that it is, in fact, a species complex, with few reliable morphological characters.Although the subject of intensive studies in the Iberian Peninsula, in the Atlantic and the Mediterranean (Monticelli 1896;Rioja 1917Rioja , 1931;;Alós 1983Alós , 1984;;Aguirrezabalaga 1984;Aguirrezabalaga et al. 1984;San Martín andViéitez, 1984, 1991;Acero and San Martín 1986) the taxonomy of species remains tangled.For Mediterranean populations, Fauvel (1927) described it as variable in pigmentation and number of pygidial papillae.Imajima and Hartman (1964) described Japanese populations as having a pygidium with two lobes each ringed with digitate processes, but provided no illustrations of this feature.Parapar (2012) reported a dorsal transverse line and barely visible lateral eyespots for Mediterranean specimens, but his illustration of the color pattern, as well the anal papillae, differ from our Galapagos material.Choi et al. (2015) reported Polyophthalmus qingdaoensis Purschke, Ding and Müller, 1995 from Korea, distinguished by a prostomium with a brain bearing dark pigment-spots, distinct lateral eyespots, only dark pigment-streaks on the dorsal side of the body, and with papillae represented as 8-10 small cirri on the posterior margin with the dorsal papillae being smaller than ventral papillae.Our Galapagos specimens have the typical dorsal color pattern of P. pictus, but with very distinct lateral eyespots in the anterior body and eight pygidial papillae.We suggest that body and lateral eyespot color patterns likely vary too much to be useful for identification.Molecular studies are required to sort out this complex around the world.
Genus Polydora Bosc, 1802 The presence of Polydora in the Galapagos Islands, previously unreported, is supported by the identification of two specimens clearly belonging to two different species: one collected in 1964 and one incomplete specimen from the present survey.Diagnosis.This very small (1 mm) specimen is in poor condition; it was collected incidentally to excavations in marine wood searching for boring isopods (Limnoria).This specimen was found amongst wood particles as isopods were being sorted in 2016 from the sample while on loan to J.T. Carlton.Prostomium weakly bifid, caruncle extending to beginning of chaetiger 3; four eyes; no occipital tentacle.Chaetiger 5 with major spines falcate with weakly lateral flange (Figure 12).Bidentate hooded hooks on neuropodium starting from chaetiger 7 with constriction.Branchiae from chaetiger 7. The pygidium is missing.Taxonomic Remarks.The specimen resembles Polydora websteri Hartman in Loosanoff and Engle, 1943 but the flange on the falcate spines is very weak.P. websteri is considered a species complex (Blake 1971;Radashevsky 1999;Read 2010).Polydora hoplura Claparède, 1868 and P. websteri are similar, but the present specimen does not appear to have the heavy recurved spines on the posterior notopodia characteristic of the former species.

Diagnosis.
A second Polydora species is in hand, but it is also indeterminate based upon an incomplete specimen (Figure 13).Round prostomium; caruncle reaches the end of chaetiger 3; no scattered small dark spots; no occipital tentacle; major spines on chaetiger 5 with secondary tooth; branchiae and hooded hooks with constriction starting from chaetiger 7; pygidium missing.Order Terebellida Family Cirratulidae Carus, 1863 Six genera of cirratulids are known from the Galapagos (Blake 1991); Dodecaceria is newly reported here.
(Figure 14) Material.Franklin's Bay (5 specimens, 27 April 2016: vial 237621; vial 233657, both from caged plate 16387, deployed for 14 months).Diagnosis.Live specimens red-green to black; when preserved, these turn dark or brown; prostomium blunt, without eyes; all the specimens have the first segment with a pair of thick grooved palps that are inserted laterally and a pair of slenderer, shorter tentacles (Figure 14).The first chaetiger has a pair of filamentous tentacles.There are no other tentacles.The pointed setae are delicately serrated along one side.The hooks starts from the 6 th and 7 th chaetiger.Hartman (1954) notes that the hooks start from the 8 th chaetiger, but this character may be size dependent.More posteriorly the neurohooks come to be increasingly stronger and acquire a strong lateral boss.
Taxonomic remarks.The specimens resemble Dodecaceria laddi Hartman, 1954, a species distinctive for its very limited number of tentacles that could be mistaken for the Chilean D. gallardoi Carrasco, 1977, especially relative to the disposition of the hooks, but the latter is distinguished by having two pairs of branchiae on the first branchial segment.The characteristics of our specimens do not fit any described Dodecaceria species (Aguilar-Camacho and SalazarVallejo 2011).This is the first record of the genus from Galapagos.The specimens were not boring into calcareous substrates.

Discussion
The number of new records (one family and nine novel genera and fifteen species) reported here is not surprising, given the absence of previous studies on the polychaetes associated with port and harbor fouling communities in the Galapagos Islands.Thus also not surprising is our discovery of six introduced species not previously reported from the Galapagos (Table 1, Table S1): the syllid Myrianida pachycera, the sabellids Branchiomma bairdi, Branchiomma sp. and Pseudobranchiomma schizogenica, and the serpulids Hydroides elegans, Hydroides sanctaecrucis, as well as one cryptogenic species, the spionid Dipolydora armata.Ship biofouling, either on the hull, in sea chests, or in seawater pipe systems (Fofonoff et al. 2003;Farrapeira et al. 2011;Frey et al. 2014), are likely the primary vectors that brought these species to the Galapagos.The non-native species have been introduced from either the warm waters of the Western Atlantic or Indo-West Pacific Oceans (Table 1).We do not as yet know the exact sources of Galapagos populations in the absence of population genetic studies.Thus, it is uncertain whether the Western Atlantic species Branchiomma bairdi and Hydroides santaecrucis arrived through the Panama Canal (in, for example, as fouling even if ballast water cannot be excluded totally, and thus not exposed as hull fouling organisms during transit through the freshwater Gatun Lake), or from secondary populations that have also been introduced elsewhere in the Pacific Ocean.For species transported through the Canal, and if the sources of Galapagos populations are the Atlantic, it may be that they first became established on the Central or South American mainland, and were then brought to the Islands in hull fouling.
Much remains to be learned about the native, introduced, and cryptogenic polychaetes of the Galapagos Islands.Our samples represent only three stations sampled in April 2016; the striking results suggest that further studies will yield a more complete picture contributing to the history of marine invasions in the Galapagos Islands.

Figure 1 .
Figure 1.Map of Galapagos Islands showing the location of the three sampling sites: 1, Baltra Island Ecuadorian Navy dock; 2, Puerto Ayora Main Passenger dock in Academy Bay and 3, Franklin's Bay dock, both on Santa Cruz Island.Map courtesy of Linda McCann.

Figure 5 .
Figure 5. Branchiomma sp.: A) Live specimen with details of color and dorsal lips; B) Preserved specimen and details of ventral lappets (photographs by E. Keppel).

Figure 8 .
Figure 8. Living specimen of Spirobranchus incrassatus; the upper is the oldest operculum and the lower the youngest: A) dorsal view, B) ventral view (photographs by E. Keppel).
Puerto Ayora (1 specimen, 24 January 1964, California Academy of Sciences 196211, collected by Robert C. Miller, in wood on old boat near Angermeyers Residence).

Table 1 .
Introduced and cryptogenic Polychaeta of the Galápagos Islands treated in the present study.Status: I, Introduced; C, Cryptogenic.