A new species of Claviramus (Annelida, Sabellida, Sabellidae) from the Ariake Inland Sea, Kyushu, Japan

Abstract A new species of the sabellid polychaete genus Claviramus Fitzhugh, 2002, is described from Ariake Inland Sea, Kyushu, Japan. Claviramus is a small genus, composed of three species worldwide. Its distinctive feature is the presence of foliaceous flanges at the distal ends of the radioles. Claviramus kyushuensissp. nov. here described is characterized by the presence of a glandular ridge on chaetiger 2, glandular shields on the abdomen, thoracic uncini bidentate, and the presence of a short, distal filament in some radioles. A key and a comparative table of diagnostic characters for species of Claviramus are provided.


Introduction
Japanese waters are represented by approximately 40 species of sabellid polychaetes (Nishi et al. 2017). Among them, eight species from soft bottoms belonging to plesiomorphic genera Chone Krøyer, 1856, Dialychone Claparède, 1870, Jasmineira Langerhans, 1880and Paradialychone Tovar-Hernández, 2008, have been reported (Nishi et al. 2009). In this study, a new species of Claviramus Fitzhugh, 2002 is described from Ariake Inland Sea, Kyushu, Japan. It was found co-occurring with Jasmineira kikuchii Nishi, Tanaka, Tovar-Hernández & Giangrande, 2009. The sabellid genus Claviramus is currently composed of three species worldwide. Claviramus candelus (Grube, 1863), the type species of the genus, was originally described as Sabella candela Grube, 1863, from the northern Adriatic Sea, but Langerhans (1884) transferred it to the genus Jasmineira. Claviramus oculatus (Langerhans, 1884) was described as Jasmineira oculata Langerhans, 1884, from Madeira. Cochrane (2000 redescribed both species within Jasmineira in detail based on type and additional specimens. Fitzhugh (2002) established the genus Claviramus based on the presence of prominent foliaceous flanges at the distal ends of the radioles, and transferred J. candelus and J. oculatus to Claviramus. The third known species, Claviramus grubei Fitzhugh, 2002, was described from Thailand, Andaman Sea. A thorough revision and synthesis of these three species was provided by Cochrane (2000) and Fitzhugh (2002).

Materials and methods
Specimens were measured to record width of the middle of the thorax, trunk length (chaetiger 1 or collar to pygidium), radiolar crown length, number of radiolar pairs, number of thoracic and abdominal segments, and presence of gametes. The diagnosis and a full description of the new species were based on the holotype, with variation in the paratypes indicated in parentheses. The thoracic and abdominal glandular pattern was revealed by staining the worms with methyl green. Parts of thorax and abdomen of one paratype CBM-ZW 1124 were observed on the scanning electron microscope JSM-6500 at the Yokohama National University. Digital photographs were taken with an attached Canon EOS Rebel T7i digital camera. Type materials were deposited at the Natural History Museum and Institute, Chiba, Japan (catalogue code CBM-ZW) and at the Colección Poliquetológica, Universidad Autónoma de Nuevo León (catalogue code UANL). A key and a comparative table of diagnostic characters for species of Claviramus are also included; the information is as complete as available based on original descriptions and redescriptions provided by Cochrane (2000) and Fitzhugh (2002). Description. Sabellid worm with eight thoracic (eight in all types) and ten abdominal chaetigers (9-16 in paratypes CBM ZW 1124-1126, UANL 8130). Trunk length 2.5 mm (1.6 mm in paratype CBM-ZW 1125, 3.2-4.7 mm in paratypes UANL 8130), body width 0.7 mm (0.3 mm in paratype CBM-ZW 1126, 0.5-1.3 mm in paratypes UANL 8130). Radiolar crown 1.1 mm length (1.3-2.1 mm in paratypes UANL 8130), with seven radioles in each branchial lobe (7-9 in paratypes UANL 8130).
Etymology. The specific epithet is named after type locality, Kyushu, Japan.   Remarks. Among the species currently recognized in Claviramus, C. kyushuensis sp. nov., is unique by having a collar shield rectangular, divided transversally into three nearly equal-sized sections; a glandular ridge on chaetiger 2; abdominal shields well developed; main fang of thoracic uncini with bifid tips and the presence of a short, distal filament in some radioles.
Claviramus grubei has also a glandular ridge on chaetiger 2, a short mid-ventral incision of distal radiolar flanges and radiolar tip filaments, but it differs of C. kyushuensis sp. nov., by lacking abdominal shields (present in C. kyushuensis sp. nov.) (Table 1).
Claviramus kyushuensis sp. nov., differs from C. oculatus and C. candelus mainly by lacking pygidial eyes (present in C. oculatus and C. candelus) and having a collar shield rectangular, divided transversally into three nearly equal-sized sections (entire in C. candelus, divided into two areas in C. oculatus) ( Table 1).
In addition, SEM images used in this study reveals that tips of main fangs of thoracic uncini are bifid (Fig. 3C, D). This peculiarity has been only reported in Amphicorina triangulata López &Tena, 1999 by Cepeda andLattig (2017). However, in A. triangulata, the presence of a large tooth above the main fang in the midline, followed by a third tooth offset from midline, and then followed by series of smaller teeth, is remarkable. In Claviramus kyushuensis sp. nov., all rows of teeth above the main fang are nearly equal-sized (Fig. 3C, D).

Discussion
Claviramus was erected based on the presence of prominent foliaceous flanges, at the distal ends of radioles (Fitzhugh 2002). However, in specimens reviewed here, these leaf-like structures are easily broken off and are present only in some radioles (other radioles have entire filiform tips revealed by presence of skeleton cells). Cochrane (2000) also showed broken radioles in some specimens belonging to C. candelus. Under this scenario, it is evident that many specimens were wrongly identified under Jasmineira. However, Jasmineira and Claviramus may also distinguishable based on the presence of inferior thoracic bayonet notochaetae (absent in Claviramus), uncinial morphology (Fitzhugh 1989;Cochrane 2000) and presence of a breaking plane sensu Cochrane (2003) or abscission zone sensu Tovar-Hernández (2008). The abscission zone refers to crowns where there is a distinct point immediately above the radiolar bases, where the radioles become detached from the branchial basis.