Review of the Capitellidae (Annelida, Polychaeta) from the Eastern Tropical Pacific region, with notes on selected species

Abstract The main objective of this work is to contribute to the taxonomic knowledge of the species of Capitellidae reported for the Eastern Tropical Pacific. This catalogue includes the original name of each species, new names, synonymies, type localities, the museum or institution where the type material is deposited, revision of the material reported for the region by different authors, new examined material, previous reports from other regions of the world, and comments on systematics and distributions. The catalogue lists 43 species in 19 genera. Of these, 6 species were erroneously recorded for the region (Decamastus gracilis Hartman, 1963; Decamastus nudus Thomassin, 1970; Mastobranchus variabilis Edwing, 1984; Notomastus aberans Day, 1957; Notomastus americanus Day, 1973; Notomastus latericeus Sars, 1851) and 5 species are found here to be questionable records for the Eastern Tropical Pacific (Capitella capitata (Fabricius, 1780); Dasybranchus glabrus Moore, 1909; Decamastus lumbricoides Grube, 1878; Notomastus lineatus Claparède, 1870 and Notomastus tenuis Moore, 1909).


Introduction
Capitellids are typical inhabitants of marine soft bottom sediments. They are important in the energy budgets of the environments due to their feeding habits and usually high abundances. Their morphology is very simple; most of the species are similar morpho-logically to earthworms. Generally they live buried in sand or mud and feed by assimilating the organic matter adhering to sediments and are thus regarded as non-selective deposit feeders . Capitellids are distributed from the intertidal zone to the deep sea and are often dominant components of the infaunal community, especially in organically enriched sediments. For their importance as indicators of changes in the ecosystems, the capitellids have been the subject of numerous ecological studies. However, there are only a few taxonomic publications in which their morphological variations have been analyzed. For this reason there has been a great number of errors made in the identification of species and many species distributions are considered doubtful.
The taxonomy of the Capitellidae is based almost entirely on the distribution, orientation, and structure of chaetae for identification at all levels (Doyle 1991). The recognition of the genera in this family has been based traditionally on the chaetal formula, in other words, the number of segments with capillary chaetae and, if present, the mixture of capillary chaetae and hooded hooks (Fauchald 1977, Amaral 1980. Although there are certain ontogenetic variations, the chaetal formula is useful in identifing adult stages. The capitellids of the Eastern Tropical Pacific have been studied by numerous authors included in the checklist of Salazar-Vallejo and Londoño Mesa (2004). In addition the capitellids of the Pacific in Costa Rica have been studied by .

Methods
In first instance the list of species was taken from a checklist of polychaetes of the Tropical Oriental Pacific (Salazar-Vallejo SI, Londoño-Meza MH 2004), and other published literature. Whenever possible, the species included in collections of different institutions previously reported for the region were revised. Genera and species are listed in alphabetical order, and the following information was provided for each species: name, authorship and date of publication, synonymy, type material, material examined from the region (most of it collected and analyzed by the authors), records, and Remarks. The abbreviations of institutions where type material may be found are given.
Remarks. The material examined by Fauvel (1943) was not found in the MNHN, and the specimens reported for México by Rioja (1947) are lost (Salazar-Vallejo 1989). In both cases Fauvel and Rioja, did not provide a complete description or illustrations of the morphological structures. Lara & Vargas-Zamora, 1995;Rivera & Romero 2008); Costa Rica: Gulf of Nicoya .
Remarks. Dasybranchus lumbricoides was described from the Philippine Islands and  reported it for Carmen Island in the Gulf of California. Upon examination of Fauchald's specimens it was determined that they were actually Notodasus harrisae . This was also the case for material identified as D. lumbricoides by  from Corona del Mar, Newport Harbor The record of Hartman 1947 from Tiburón Island was not available for examination and we believe that her identification should also be considered doubtful. Kudenov, 1975 http://species-id.net/wiki/Dasybranchus_parplatyceps Dasybranchus parplatyceps Kudenov, 1975: 218, figs   Records. México: Sonora, Station Beach, Puerto Peñasco (Kudenov, 1975). Baja California Sur, continental shelf (Hernández-Alcántara & Solís-Weiss 2003). Baja California Sur (Bastida-Zavala, 1993, 1995, Baja California Sur, Sonora and Nayarit (present study).

Genus Decamastus Hartman, 1963
Decamastus gracilis Hartman, 1963 http://species-id.net/wiki/Decamastus_gracilis Decamastus gracilis Hartman, 1963: 27;1969:375;Bastida-Zavala, 1995: 12 Records. USA: California (Hartman 1963). Remarks. Decamastus gracilis was described from Southern California (USA) and Bastida-Zavala (1995) reported it from La Paz Bay. After examination of Bastida-Zavala's materials we conclude that they correspond to Dasybranchus parplatyceps and that the record of D. gracilis from México is erroneous. Thomassin, 1970 http://species-id.net/wiki/Decamastus_nudus Decamastus nudus Thomassin, 1970: Thomassin 1970), Costa Rica  Remarks. Decamastus nudus, described from Madagascar, was reported by Hernández-Alcánatra & Solís-Weiss (1993,1998,1999) for the Gulf of California, but these specimens differ from the original description of Thomassin (1970), in having prostomium with palpode, dark brown eyespots, epithelium smooth on first segments, and hooded hooks with a main fang with four rows of small teeth. D. nudus lacks a palpode, has orange pigment spots, the first 3-4 segments are slightly tessellated, and hooded hooks with a main fang and 2-3 rows of small teeth. We consider that these specimens belong to a different species not previously described. For that the record of D. nudus from Gulf of California is erroneous.  , California, Florida, North Carolina and Massachusetts (Hartman 1947), Iranian Gulf (Wesenberg-Lund, 1949), Japan Sea and Okhotsk Sea (Ushakov, 1965), Southern Africa (Day, 1967), California , Germany (Hartmann-Schröder, 1971), Australia Rainer 1979, 1981), Costa Rica ; Thailand  Remarks. After examination of the specimens reported by Bastida-Zavala (1995) as L. glabra it was found that this corresponds to Dasybranchus parplatyceps . Therefore this species is only known from the original description locality in the Gulf of California.

Mediomastus glabrus
Remarks.  described Neonotomastus, including the species N. glabrus, but in his description of the genus he mentioned that the thorax had 10 segments with capillary chaetae. When examining the type material we found 11 thoracic segments with capillary chaetae. We consider this genus as valid. It is characterized by thoracic segments with capillaries, by the presence of a unirramous first chaetiger, a first abdominal chaetiger with notopodial capillary chaetae and the presence of neuropodial capillary chaetae and hooded hooks, the presence of capillary chaetae and hooded hooks in the notopodium and hooded hooks only in the neuropodium in the second abdominal segment.
Remarks. The material of Hernández-Alcántara & Solís-Weiss (1998) identified as Mastobranchus? variabilis was analyzed and was found to be Neopseudocapitella brasil-iensis. This record, and our collections from Puerto Peñasco, Sonora, constitutes the first record for this species in the Mexican Pacific.

Notomastus Sars, 1851
Notomastus Sars, 1851:199 Type species. Notomastus latericeus Sars, 1851. Day, 1957 http://species-id.net/wiki/Notomastus_aberans Notomastus aberans Day, 1957: 105, fig. 7 a-b;Day, 1967: 599, fig. 28.1 m-q;de León González, 1994 Records. South Africa (Day 1957(Day , 1967. Remarks. Notomastus aberans was described from South Africa and de León-González (1994) reported it for the western coast of the Baja California Peninsula. Examination of the Mexican material, found that this was Notomastus polyodon  described from Vietnam. This was corroborated after the revision of the holotype of that species. The Mexican specimens as well as the type material of N. polyodon have a mid-dorsal lobe between the thoracic notopodia on chaetiger 8 to 11 and the abdominal notopodia and neuropodia have expanded edges appearing as triangular lobes. Furthermore, methyl green staining patterns are similar in both specimens, with the prostomium and first three segments staining light green, segments 4 to 8 intensely green, segments 9 to 11 with a wide prechaetal dark green band moderately staining, abdominal segments, and two   from the Gulf of California. Following examination of the Mexican specimens, they were found to belong instead to the species N. hemipodus .   , Baja California Sur, Sonora (material reported in this study).

Conclusion
In this study we first found 43 species of Capitellidae from Eastern Tropical Pacific belonging to 19 genera. Following analysis of type and non-type material we conclude that this list should be reduced to 32 valid species in 17 genera. Of these, 14 species were originally described from the Eastern Tropical Pacific.