Revision of Cirratulus ( Cirratulidae : Polychaeta ) from Argentina , with the description of three new species and a key to identify all species of the area Revisión de Cirratulus ( Cirratulidae : Polychaeta ) de Argentina , con la descripción de tres nuevas especies y una clave para identificar todas las especies del área

Introduction: The taxonomy of Cirratulidae is not easy due to the diagnostic characters currently accepted change through ontogeny, in some cases, there are even difficulties to separate juveniles from adults. Among the Cirratulus species cited, described and considered as valid for Argentina are Cirratulus jucundus (Kinberg, 1866), Cirratulus patagonicus (Kinberg, 1866) and Cirratulus mianzanii Saracho Bottero, Elías & Magalhães, 2017. Objetive: This study made a revision of Cirratulus includes material deposited in the Museo de Ciencias Naturales de La Plata (MLP) and specimens collected privately by J.M. Orensanz that was donated to the laboratory of Bioindicadores Bentónicos of the National University of Mar del Plata. Methods: The specimens were examined with optical equipment (microscope and stereomicroscope) and also by a scanning electron microscope (SEM). Results: A complete examination of the material, revealed a higher number of species than those already mentioned. In the present work, three new species are described from the intertidal and subtidal areas of the Argentine continental shelf: Cirratulus orensanzii n. sp.; Cirratulus knipovichana n. sp. and Cirratulus alfonsinae n. sp. Conclusions: The knowledge about the taxonomy of the family as well as the updating of the geographic registries contributes to the biodiversity of the region, which is of great importance to carry out both ecological studies and conservation plans.


Introduction
The taxonomy of Cirratulidae is not easy due to the diagnostic characters currently accepted change through ontogeny, in some cases, there are even difficulties to separate juveniles from adults. According to Blake (1996), the cirratulids who have groups of tentacular filaments (multitentaculates) instead of paired dorsal tentacles are organized into four genera: Cirratulus Lamarck, 1818, Timarete Kinberg, 1866, Cirriformia Hartman, 1936, and Protocirrineris Czerniavsky, 1881. Posteriorly another genus Fauvelicirratulus Çinar and Petersen, 2011 was added. These genera are distinguished on the basis of the kind(s) chaetae present, the segment(s) from which the tentacular filaments arise, segment(s) from which the branchiae arise, the position of the branchiae and shape of the prostomium. Cirratulus, Timarete and Cirriformia have a more or less wedge-shaped prostomium, capillary chaetae and acicular spines (aciculars). Fauvelicirratulus has a bluntly conical to wedge-shaped prostomium, long capillary chaetae and presence of long, straight spines instead of the short acicular ones. Protocirrineris has a bluntly conical to wedge-shaped prostomium and only capillary chaetae. The genus Cirratulus has almost 38 species currently reported worldwide (Blake & Magalhães, 2017). Among the species cited, described and valid for Argentina are Cirratulus jucundus (Kinberg, 1866), Cirratulus patagonicus (Kinberg, 1866) and Cirratulus mianzanii Saracho-Bottero, Elías, & Magalhães, 2017. As part of a recent revision of the material deposited in national collections, and private collections, a higher number of species than those already mentioned have been registered in Argentina. In the present work, we described three new species: Cirratulus orensanzii n. sp. is a species inhabiting intertidal salt-marshes in the patagonic subantarctic region, while Cirratulus knipovichana n. sp. is widely distributed in subtidal areas of the warm temperate continental shelf, including Uruguay. The last one, Cirratulus alfonsinae n. sp. is only known for the type locality among mussels on a centric beach of Mar del Plata city. The new species are described and compared with its closest congeners. An illustrated key for the species of Cirratulus from Argentina is presented.

Materials and methods
This revision of Cirratulus includes material deposited in the Museo de Ciencias Naturales de La Plata (MLP) and specimens collected privately by J.M. Orensanz that was donated to the laboratory of Bioindicadores Bentónicos of the National University of Mar del Plata. The specimens were examined with optical equipment (microscope and stereomicroscope) and also by a scanning electron microscope (SEM) JEOL, JSM-6460 LV. The material for SEM was prepared performing dehydration in ethyl alcohol (70, 80, 90, 95 and 100 %). Samples were dried in HMDS (hexamethyldisilazane), mounted on aluminium stubs and metalized with Au-Pd. Type materials of the three newly described species are deposited in the Invertebrate collection of the Museo de Ciencias Naturales de La Plata (MLP), Argentina. Zoobank link: LSIDurn:lsid:zoobank.org:pub:03AECCCD-CE01-48C4-A431-280584EAF90C Additionally, in order to help ecologists to identify Cirratulus species from the area, a key with illustrations have been made.  Blake & Magalhães, 2017): Prostomium wedge-shaped, elongate or blunt, usually with transverse rows of eyespots, with a pair of small slits or depressions nuchal organ at the postero-lateral edge; peristomium with two-three annulations. Two or more grooved tentacular filaments arising from between peristomium and first chaetiger or in a single anterior segment. The first pair of branchiae is found in the same chaetiger that the tentacular filaments, occurring singly, and continuing over most of the body to posterior end, above notopodium or becoming more dorsal in middle body segments. Parapodial rami well separated. Chaetae include capillaries with serrated or smooth edges and curved acicular spines. Pygidium with or without lobes surrounding anus.

SYSTEMATICS
Remarks: Taxonomic problems with the genus Cirratulus include the incorrect determinations of Cirratulus cirratus (O. F. Müller, 1776) from widespread areas. Upon a comprehensive study of Cirratulus from various parts of the world, it was seen that it consisted of multiple species. Blake (1996) evaluated records of Cirratulus cirratus and others in the NE Pacific and was able to separate five species, one new, none of which agreed with species he had seen from the North Atlantic. He hypothesized a great diversity in Cirratulus species in the world. In the SW Atlantic, a similar pattern can be seen. Cirratulus jucundus (Kinberg, 1866) and Cirratulus patagonicus (Kinberg, 1866) were cited for Argentina from the analysis of material deposited in collections by Saracho Bottero et al. (2017). Cirratulus mianzanii Saracho Bottero, Elías & Magalhães, 2017 was described for Argentina from the analysis of material collected in Peninsula Valdez, Argentina. Specimens of Cirratulus of numerous areas from Argentina that was collected and identified by Description: Body fusiform, short and stout, anterior region without shoulders, rounded in cross section, dorsally inflated, ventrally grooved (Fig. 1A, B). Pygidium simple lobe with anus terminal. Color yellowish in alcohol. Prostomium conical, round, as long as two first chaetigers; with lateral oblique nuchal organs (Fig.  1C), and one oblique row of black eyespots (five-eight) almost continue (Fig. 1D), not observed under SEM. Peristomium with three annuli, as long as two-three chaetigers, first annulus distinctly separated from prostomium ( Fig. 1A, B). Two oblique groups of four-six tentacular filaments, arising from chaetiger 1; first pair of branchial filaments from anterior part of chaetiger 1 (Fig.  1B). Branchiae a pair per chaetiger, less abundant in middle region and absent in last chaetigers. Branchial filaments arise close to notopodium in first chaetigers, at the same distance between noto-and neuropodium, then slightly more dorsal to on middle region of the body. The distance between branchial insertion in respect to notopodium is twice and a half the distance between notoand neuropodium or more from the chaetiger 8. Noto-and neuropodium very close and with differentiation in chaetes; chaetigers with a simple row of capillaries in the notopodium (5-6) and in the neuropodium (3-4). Capillary chaetae with one edge with blade distinctly striated at base, and a serrated edge seen in optical microscope (100x) and SEM. Acicular spines slightly curved distally, present from middle chaetigers in notopodium (10-13), alternated with serrated capillaries; two-four neuropodial acicular spines from chaetiger 1 (Fig. 1E) intercalated by capillaries.
Methyl green staining pattern: No distinctive staining pattern. Whole worm stained with light green.

Habitat: Tidal flats inhabited by Spartina sp.
Reproduction: There is no available information about sexual or asexual reproduction for this species. However, specimens with eggs were observed in the coelomic cavity. (Fig. 1F).
Distribution: This species is only known for the locality of Puerto Deseado (47.75° S -65.9° W) in intertidal areas of the SW Atlantic Ocean, Argentina.
Remarks: Cirratulus orensanzii n. sp. is similar to Cirratulus jucundus and Cirratulus patagonicus in the general body morphology, including the number and position of eyespots but differs in respect to the number of tentacular filaments: C. jucundus has eight-10 and C. patagonicus 15-20 in each fascicle but Cirratulus orensanzii n. sp. has four-six. In addition, the position of the first pair of branchiae is in the posterior end of the first chaetiger in both C. jucundus and C. patagonicus but in Cirratulus orensanzii n. sp., it is in the anterior end of the first chaetiger. The neuropodial spines appear from the first chaetiger, and the notopodial spines from chaetigers 6-9 in C. jucundus whereas in Cirratulus orensanzii n. sp. neuropodial spines are from the first chaetiger and notopodial spines from middle chaetigers (10-13). The anus is terminal in C. jucundus, C. patagonicus, and Cirratulus orensanzii n. sp. Other similar species is Cirratulus mianzanii with similar body morphology, however the first pair of branchial filaments in Cirratulus orensanzii n. sp. arise from the anterior end of the first chaetiger below the tentacular filaments whereas in C. mianzanii they arise between the peristomium and the first chaetiger below the tentacular filaments. Neuropodial and notopodial spines start from the first chaetiger and middle chaetigers in both species, respectively. The pygidium has a ventral lobe and anus sub-terminal (dorsal) in C. mianzanii while it is terminal lacking lobes in Cirratulus orensanzii n. sp. The cross-section of these species also shows differences, mostly in respect to the position of branchiae throughout the body.
Ethymology: This species is dedicated to José María Orensanz  who was the father of the polychaetes of Argentina. He collected polychaetes from all the SW Atlantic, including a lot of the material described in this work.  Description: Body fusiform, short and stout, anterior region with first five-eight chaetigers crowded with incipient shoulders ventrally flat; then rounded in cross section, dorsally inflated, ventrally grooved ( Fig. 2A, B). Pygidium simple lobe with anus terminal (Fig. 2A, F). Color brown-reddish in alcohol, with iridescent reflections. Prostomium conical, round, as long as two first chaetigers; with lateral oblique nuchal organs (Fig.  2C), and one pair of black eyespots, not observed under SEM. Peristomium with three annuli, as long as three-four chaetigers, first annulus distinctly separated from prostomium ( Fig. 2A, B). Two oblique groups of two-four tentacular filaments, arising from posterior end of peristomium and about the anterior end of first chaetiger (Fig. 2B). First pair of branchial filaments from posterior end of peristomium (Fig. 2D). Branchiae a pair per chaetiger, less abundant in middle region and absent in last chaetigers. Branchial filaments arise close to notopodium in first chaetigers, at same distance between noto-and neuropodium. Distance between branchial insertion in respect to the notopodium similar to distance between noto-and neuropodium. Notopodium and neuropodium very close together; anterior and middle chaetigers with a single row of three-seven serrated capillary chaetae in notopodium, two-four serrated capillary chaetae in neuropodium, number of capillaries reducing towards posterior region. Capillary chaetae with one serrated edge (Fig. 2D). Acicular spines slightly curved distally, present from middle chaetigers in notopodium, alternated with serrated capillaries; two-four neuropodial acicular spines from chaetiger 1 (Fig. 3D) with one capillary chaeta between spines.
Methyl green staining pattern: No distinctive staining pattern. Whole worm stained with light green. Habitat: Sand bottoms in subtidal depths.

Reproduction:
There is no available information about sexual or asexual reproduction for this species.
Distribution: This species is distributed in the continental shelf off Argentina including the Rio de la Plata (SW Atlantic Ocean, Argentina).
Remarks: Cirratulus knipovichana n. sp. is similar to Cirratulus jucundus in the general body morphology, but differs in respect to the number of tentacular filaments: C. jucundus has eight-10 in each fascicle but two-four in C. knipovichana n. sp. In addition, the position of the first pair of branchiae is in the first chaetiger in C. jucundus, but in posterior end of peristomium in C. knipovichana n. sp.; the neuropodial spines appear from the first chaetiger, and the notopodial spines from chaetigers 6-9 in C. jucundus, whereas in C. knipovichana n. sp. neuropodial spines are from first chaetigers and notopodial spines from middle chaetigers. Other similar species is Cirratulus patagonicus with similar body morphology; however, it has two groups of 15 or more tentacular filaments whereas C. knipovichana n. sp. has only two-four tentacular filaments. The first pair of branchial filament in C. knipovichana n. sp. arises from the groove between the peristomium and chaetiger 1 below the tentacular filaments whereas in C. patagonicus they are from the posterior region of chaetiger 1. Neuropodial spines start from chaetiger 1 in Cirratulus patagonicus and notopodial spines from chaetigers 10-12, whereas

Discussion
The diversity of cirratulids in Argentina is increasing as the studies of this family are deepened. A first step occurred when the studies focused on the bitentaculate species (Elias & Rivero, 2008), and now occurs in the multitentaculate species. This trend is expected to be similar in other areas of the southern hemisphere. Table 1 was realized to bring together the morphology and distributional records of 10 accepted species of Cirratulus in Atlantic Ocean waters in order to assist non-specialists with the identification of specimens. It is noteworthy, that Cirratulus cirratus, the type species, is included in this table because it is one of the most conflicting species within the genus both for its taxonomy and its wide distribution. This distribution is probably due to wrong identifications. This study was favored by two reasons, one reviewing the material deposited in the two largest natural science museums of Argentina, and the other by the review of the material collected by Lobo Orensanz throughout his life . This collection was lost for several years, but it was found among the belongings of our remembered Mary E. Petersen , and shipped back to Argentina. In a relatively little time we have described four new Cirratulus species, that added to the two previously described species. In the annotated catalogue of J. M. Orensanz (unpublished) he mentioned the two species described by Kinberg (1866) for Antarctica, C. patagonicus, C. jucundus, and a Cirratulus near cirratus species. The latter is most probably a misidentification rather than an enlargement of the distribution of this European species. Probably, more additions will rise when deepen studies reveal the real diversity of Cirratulids in austral waters. Argentina has more than 4500 km of costal lines, mostly unexplored. The continental shelf, extending more than 350 km offshore in some austral regions, is also poorly known, perhaps the new initiative of Argentine government, the Pampa Azul project (Comité Coordinador Interministerial, 2019), intending to explore the submarine areas, allows knowing more about the polychaetes and in particular about Cirratulids.
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.