Update on Benthic Scyphozoans from the Brazilian Coast (Cnidaria: Scyphozoa: Coronatae)

Members of the order Coronatae are considered the basal group of Scyphozoa, containing approximately 60 species. Observation of life cycle is critical to unravel the systematics and taxonomy of the order. However, recent studies related only to the polyp stage were able to promote progress using solely morphological characters of the periderm tube. The lack of knowledge about the actual number of coronate species occurring in Brazil and their distribution along the coast is a factor that limits more advanced approaches to interpret the biogeography of these animals. Our goal was to identify and describe the Coronatae polyps from N, SE and S Brazil, taking into account the bathymetric and longitudinal distribution of species. Measurements of the periderm tube under light microscopy and the organization and morphology of the internal cusps observed through Scanning Electron Microscopy allowed the recognition of three morphotypes, recognized only at the genus level: two morphotypes of Nausithoe (eight and 16 cusps) and one form of Atorella.


INTRODUCTION
The order Coronatae Vanhöffen, 1892 is considered the basal group of the class Scyphozoa Goette, 1887 (viz Marques & Collins, 2004;Collins, 2009). Members of this order have a polyp stage with a firm periderm tube that fully surrounds the soft parts (Werner, 1970;Arai, 1997;Mendoza-Becerril et al., 2016), distinguishing them from other Scyphozoa, the subclass Discomedusae Haeckel, 1880, that have only reduced exoskeleton at the base of the polyp stalk or at podocysts.
The diversity of coronates is estimated to be around 60 species (Morandini & Jarms, 2012; distributed all over the world. The group is widely known and represented in many general texts as being composed by deep-water medusae (Kramp, 1961). But since the mid 1960's the number of polyp species recognized for the group grew (e.g. Werner, 1966;Werner, 1973;Jarms, 1990), and also several shallow water forms were found (e.g. Silveira & Morandini, 1997).
The study of the life cycle, emphasizing both the benthic polyp and the pelagic medusa, is critical in addressing the systematics of the order (Werner, 1973;Silveira & Morandini, 1997) and understanding aspects of the group's evolution (Jarms, 2010). This statement is a consequence of the traditional systematics of coronates, which is mainly dependent on observation of adult and mature forms, i.e. the medusoid stage. In the past, many preserved polyp specimens were identified only as Coronatae polyps (see Jarms, 1990Jarms, , 1991 thus creating some instability in the systematics and taxonomy of the order. In general, there were two groups of species (Werner, 1973) mainly distinguished based on bathymetry: a shallow water form (Stephanoscyphus corniformis), and a deepwater species (Stephanoscyphus simplex) (Kramp, 1959). Jarms (1990) proposed to use a taxonomic resource to accommodate species with unknown medusa, creating the genus Stephanoscyphistoma. However, recent studies analyzing only the polyp stage promoted progress using morphological characters of the periderm tube for differentiating some species (Morandini & Jarms, 2005, 2010, 2012. These characters were available in the literature (Kramp, 1959;Naumov, 1959Naumov, , 1961, but their use for differentiating species were only proposed by Jarms describe samples of Coronatae polyps available from different parts along the Brazilian coast, based on morphometric measurements of the periderm tubes.

MATERIAL AND METHODS
Coronate polyps from different projects along the Brazilian coast were available. The material was collected from 4º27'54"N to 29º12'S and 43°51'12''W to 49º58'05"W, with dept varying from 84 m to 2,064 m (Table 1, Figure 1). The projects referred to BFZ (Project on Amazon Basin) -21 stations (Amapá  All periderm tubes were measured to check the total length. For standardization, only the tubes longer than 5 mm were measured in detail, because all measurements and relationships available in the literature address animals over this size (5 mm; Jarms, 1990Jarms, , 1991. Polyps were measured according to the standards presented by Jarms et al. (2002b): total length of tube, diameter at 2 mm above the base, diameter at 5 mm above the base, diameter of the basal disk, diameter immediately above the basal disk and the diameter of the tube opening. Additionally, the external arrangement of the periderm tube was noticed (considering the number of transverse rings in each 0.4 mm). To avoid variations in the number of transverse rings along the tube, two measurements were conducted for each tube: one at 2 mm and another at 5 mm above the base. and other with a smoother tube surface (genus Nausithoe). Such difference was found both at 2 mm as well as at 5 mm above the base. Differences in the number of internal cusps at each whorl and the contour of the cusp base were also observed (seen through the tubes and SEM). Based on this feature, we managed to distinguish two different morphotypes of Nausithoe.  tube aperture diameter from 0.309 -1.906 mm. Number of transversal rings at tube surface from 2 -6 in an interval of 0.4 mm, measured 2 mm above the base (Figure 2A). The number of whorls of cusps varies from 1 -11, and each whorl has eight spines. The contour of the attachment of the cusp into the tube wall is higher than broader when seen through the tube wall. Internally, cusps are arranged as four larger perradial and four smaller interradial ones, with smooth surface and no further ornamentation. At the most basal whorls, additional cusps can be observed at the free margin ( Figure 3A, B).

DISCUSSION
Up to now, eight species of coronates were reported along the Brazilian coast (Oliveira et al., 2016).
The medusae: Atolla wyvillei, Nausithoe atlantica, Nausithoe punctata and Periphylla periphylla; and the polyps: Linuche unguiculata, Nausithoe aurea, Stepahnoscyphistoma corniformis and Stephanoscyphistoma simplex. There are still four polypoid forms without specific identification; two belonging to the genus Atorella and two belonging to the genus Nausithoe (Jarms et al., 2002a). The exact number of coronate species on the Brazilian coast cannot be assured because of these unidentified polypoid forms, but also due to our widespread ignorance about the deep-water fauna (Morandini, 2003).
Considering the Atorella specimens, there is no record of any species of this genus along the Brazilian coast. Additionally, our knowledge of the diversity of species based on polyp forms is not satisfactory to precisely identify the present form, as happened in the past (Jarms et al., 2002a). The literature regarding the genus for the Atlantic Ocean reported only the medusa stage of Atorella octogonos Mills, Larson & Youngbluth, 1987 restricted to the region of the Bahamas (Mills et al., 1987;Morandini & Jarms, 2005) and two forms of polyps found on the Brazilian coast (Jarms et al., 2002a) -one with larger cusps presenting additional cusps and the other without further ornamentation on the internal cusps.
Taking into account members of the genus Nausithoe, the feature "presence of additional cusps" is clearly indicative of distinction between species. Unfortunately, there is no comprehensive study on the genus Atorella to evaluate the validity of this feature, partly due to the difficulties in collecting both medusa and polyp forms, partly for distinguishing the polypoid stage among polychaetes, anemones and other coronate tubes. Moreover, the polypoid form of A. octogonos is not known until now.
The studied specimens of the genus Nausithoe were also not possible to be identified to the species level. Although there are much more knowledge concerning the polyp forms of the genus (Morandini & Jarms 2005, 2010, 2012, most of the identification still relies on the medusa stage.
Considering the records and occurrence data of Nausithoe medusae along the Brazilian coast, there are only a few reports (Goy, 1979;Neumann-Leitão et al., 2008;Nogueira Jr. et al., 2014, 2015Oliveira et al., 2016). The listed species are Nausithoe punctata (Goy, 1979;Neumann-Leitão et al., 2008;Nogueira Jr. et al., 2014, 2015 and Nausithoe atlantica (Correia, 1983;Oliveira et al., 2016). However, those reports were made by non-specialists on scyphomedusae and due to the difficulty in distinguishing species, we consider them doubtful. The record of Nausithoe atlantica was based on plankton samples along southern states coast (Paraná and Santa Catarina), and included in a MSc thesis; the record was considered in the South American census of medusozoans published by Oliveira et al. (2016), but there is no picture or any voucher specimen to check the identity. The records of Nausithoe punctata were based on specimens from the northeast (Goy, 1979;Neumann-Leitão et al., 2008) and southern coasts (Nogueira Jr. et al., 2014, 2015. The traditional available descriptions of Nausithoe punctata (Mayer, 1910;Kramp, 1961) mention features that are so general that any Nausithoe species can fit in them. This makes the identification of the species extremely difficult and dependent on knowledge about the life cycle. The medusa of Nausithoe punctata comes from colonial polyps (Werner, 1973), and such polyps were never found in the Brazilian coast. The polyps of the species Nausithoe aurea were already found in the south (Santa Catarina), southeastern (Espírito Santo, Rio de Janeiro, and São Paulo) and northeastern (Bahia) regions (Morandini & Jarms, 2005 aurea (Brazil), N. maculata (Puerto Rico), and N. hagenbecki (only known from a Zoo aquarium; see Jarms, 2001). N. aurea and N. maculata have very similar features both as polyp and medusa stages, the only distinction between them, so far, is related to the pattern of asexual reproduction (Silveira & Morandini, 1997;Morandini & Silveira, 2001).
Although the literature on systematics and taxonomy of Coronatae rely mostly on life cycle observations, a few works stated that the polyp stage of families Nausithoidae and Atorellidae could be sufficient for identification of species. Unfortunately, the animals herein studied by us could only be identified up to genus level.