A catalogue of the scaleworm genus Lepidonotus (Polynoidae, Polychaeta) from South America, with two new records for Brazilian waters

Abstract The genus Lepidonotus is the largest in number of species within the Polynoidae, with more than 70 described species and subspecies. A catalogue of 18 nominal species and subspecies of Lepidonotus from South America is provided, with valid names, synonyms and original citations. Redescriptions and illustrations of two species based on new specimens collected along the littoral of the State of Paraíba, northeastern Brazil are included. Lepidonotus carinulatus and Lepidonotus natalensis are reported for the first time for Brazilian waters. A comparative table of characters for all reported species and subspecies of Lepidonotus from South America is provided.


Introduction
The scaleworm Lepidonotus belongs to the family Polynoidae, and contains more than 70 described species (Read and Fauchald 2015). They have been found from the intertidal to the bathyal zones, in diverse marine environments (Day 1967, Fauchald 1977, Salazar-Silva 2006, Wehe 2006. Leach (1816) established the genus Lepidonotus for the species Aphrodita clava Montagu (1808), which had been described earlier. This author did not provide identifying characters of the genus, which led to subsequent confusion in the literature, causing many synonyms. Later, Seidler (1923) made a very extensive review of the Lepidonotinae, presenting descriptions and keys to more than 50 species of Lepidonotus, but there are almost no illustrations to supplement the descriptions, nor is it clear from the text which specimens or types were examined (Wehe 2006). However, Wehe (2006) clarified that this paper is invaluable in providing base-line data and access to the literature on lepidonotid genera.
Lepidonotus has a short body with 26 segments, is dorsoventrally flattened, and subrectangular in the cross-section. The prostomium is bilobed, extending anteriorly into the ceratophores of the terminally-attached lateral antennae. The antennae and cirri are smooth. A facial tubercle is present; the buccal segment is with or without nuchal fold. Twelve pairs of elytra are present on segments 2, 4, 5, 7, 9, 11, 13, 15, 17, 19, 21 and 23; elytra are with or without tubercles and papillae. The notopodia small or vestigial, unidentate notochaetae are short. The neuropodia are large, with or without an acicular lobe; the neurochaetae are stout, long, with subdistal spines and unidentate or occasionally bidentate tips (Fauchald 1977, Amaral and Nonato 1982, Ruff 1995, Wehe 2006.
In this paper, a catalogue of the genus Lepidonotus from South America is provided, and L. carinulatus and L. natalensis are redescribed, collected in the intertidal region of the State of Paraíba, northeastern Brazil. These two species are reported for the first time for Brazilian waters.

Material and methods
The species accounts in the catalogue are given alphabetically. Each account contains author, publication year, number of pages, figures, types, and deposition numbers, together with the abbreviation of the museum or institution in which the type material is deposited, type locality with coordinatesand geographical distribution, when available. In some cases, remarks on taxonomic status of somes species are included. Synonyms are listed chronologically. A comparative table for all reported species and subspecies from South American is provided (Table 1).
Specimens were collected by handpicking during low tides from the intertidal region (0.0-0.2 m) and by snorkeling to a depth of up to 5 meters along the coast of the state of Paraíba. Specimens were fixed in formaldehyde (10% in seawater), and The nomenclature of appendages and other characteristics of polynoids mentioned in this paper follow Tebble and Chambers (1982), Hanley and Burke (1991), Ruff (1995), Imajima (1997), and Wehe (2006).
The following abbreviations are used in the text:
Remarks. The genus Lepidonotus contains more than 70 species distributed worldwide (Ruff 1995). However, only 18 species and subspecies have been reported for South America, including the two new records described here.
Remarks. Lepidonotus caeruleus presents a wide distribution. Futher studies are required to enable us to understand if it is a cryptogenic species, because there are no studies to show that it represents a species complex, and its origin was not determined.
Description. Body elongated, flattened dorsoventrally, subrectangular in cross-section; 2 mm in length, including palps and pygidial cirri; 26 chaetigerous segments, and pygidium ( Figure 2a-b). Prostomium bilobed, rounded to hexagonal, lateral antenna with terminal insertion (Figure 3a). Two pairs of eyes; anterior pair dorsolateral, near widest portion of prostomium, posterior pair near posterior end of prostomium, converging towards midline, buccal segment without nuchal fold, but with pair of nuchal nodules ( Figure  3a-b). Median and lateral antennae, tentacular and dorsal cirri with two dark rings ( Figure  2a), both having subdistal swelling, culminating abruptly in sharp point; ceratophores cylindrical, median antenna larger than lateral antennae. Pair of palps, slightly smaller than median antenna, culminating in thin point, with 8 longitudinal rows of papillae.
Tentacular segment with two pairs of cylindrical tentaculophores, with three prostomial chaetae on anterodorsal bases. Buccal cirri larger than ventral cirri, with cylindrical cirrophores. Pharynx with nine pairs of papillae and two pairs of maxillae. Facial tubercle present. Dorsal cirri with same coloration as median antenna, larger than ventral cirri, with cylindrical cirrophores.
Remarks. Zenetos et al. (2010) assigned L. carinulatus as an exotic species with an origin in the Indo-Pacific/Red Sea. Its establishment success in the Mediterranean is questionable, because its description, based on local specimens, was insufficient. It is an exotic species in Brazilian waters with casual establishment success; because only the present records are known, it is presumed to be non-established in the Mediterranean area (Zenetos et al. 2010).  Monro, 1928 Lepidonotus crosslandi Monro, 1928: 553-555
Diagnosis. Without nuchal fold; some elytrae with group of papillae in center, dark pigmentation and small tubercles after 4th or 5th pair, giving impression of smooth elytra; elytra margin and surface with long slender, digitiform papillae; notochaetae partially threadlike; neurochaetae unidentate.
Twelve pairs of elytra covering dorsum entirely, with dark or dark-brown pigmentation; pairs until last chaetiger segment following order: 2, 4, 5, 7, 9, 11, 13, 15, 17, 19, 21 and 23. First three pairs more ornate, with macro and microtubercles ( Figure  5f-h); these tubercles located more posteriorly on elytra after 4th or 5th pair, giving impression of smooth elytra; on 11th and 12th pairs ornamentation similar to that in first pairs. Most of macrotubercles on central region, surrounded by microtubercles (Figure 5i-j). Very long digitiform papillae along external edge, and group of papillae near inferior base of elytra or sometimes next to center (Figure 5k). Nephridial papillae starting from chaetiger 7, with peduncular aspect. Short ventral cirri with thin tip; one pair of short anal cirri with same coloration as median antenna; anus dorsal in 23rd chaetigerous segment (Figure 4b).
Remarks. Lepidonotus natalensis presents a wide distribution. Futher studies are required to enable us to understand if it is a cryptogenic species, because there are no studies to show that it is a species complex, and its origin was not determined.
Distribution. Western Atlantic from Massachusetts to Colombia, with one record for Antarctica. Eastern Pacific from Mexico. From 2 to10 m.
Type locality. Punta Arenas, Chile. Distribution. Eastern Pacific from Costa Rica and Chile. Western Atlantic from French Guyana.
Remarks. There is material in the USNM from the Galapagos Islands.

Discussion
Herein, all information on members of the genus Lepidonotus found around South American coasts in the literature have been gathered, and additional data on two species collected in northeastern Brazil is provided. Eighteen species and subspecies are catalogued from South America, and three of them represent endemic taxa: L. brasiliensis and the subspecies L. brasiliensis brevis are endemic for Bahia, Brazil, while L. margaritaceus is endemic from Ecuador. The subspecies L. brasiliensis brevis is very similar to the species L. brasiliensis. However, only a detailed review can confirm if the two taxa are synonyms.
The species L. caeruleus, L. carinulatus, L. hupferi, L. natalensis, and L. tenuisetosus have a broad distribution, and have been reported from several countries. According to Zenetos et al. (2010) and Çinar (2013), the species L. carinulatus and L. tenuisetosus are exotic species in the Mediterranean and have possibly originated in the Indo-Pacific region/Red Sea. Their introduction area was through the Mediterranean and Sea of Marmara. Despite the broad distributions of L. caeruleus, L. hupferi and L. natalensis, more studies are needed to indicate if they may possibly represent exotic species, their possible areas of introduction, and into which ecological category they belong accord-ing to the classification scheme of Çinar (2013). The possible origin of L. natalensis is Natal, South Africa, and it was possibly reported from the Suez Canal, Arabian Sea, and Karachi, Pakistan. It is herein reported from the southwest Atlantic, in the state of Paraíba. Lepidonotus caeruleus was first described off Rio de Janeiro, and was reported from the Pacific coast of North America and Japan. Lepidonotus hupferi was first described from the Eastern Atlantic from Senegal and Cape Verde, and later reported for the Pacific from New Caledonia, Australia, Mexico, and Ecuador. The remaining species present narrow distributions spanning few countries.
For some records essential features are not presented clearly, such as the ornamentation of the elytra, or the shape of the prostomium and chaetae. Some characters, such as form of nuchal folds, pigmentation of the antennae, and dorsal cirri, are not mentioned for the species Lepidonotus brasiliensis and L. panamensis. We are left with the view that species are very similar and difficult to distinguish. Therefore, revisionary studies of Lepidonotus are needed to establish whether cryptic species occur.