Chaetozone Malmgren, 1867

Blake, James A., 2022, New species and records of Caulleriella, Chaetocirratulus and Chaetozone (Annelida, Cirratulidae) from continental shelf and slope depths of the Western North Atlantic Ocean, Zootaxa 5113 (1), pp. 1-89 : 30-31

Genus Chaetozone Malmgren, 1867

Type species: Chaetozone setosa Malmgren, 1867 , by monotypy.

Diagnosis. (Emended from Blake 2018). Prostomium conical to pointed, usually lacking eyespots, with a pair of small nuchal slits or depressions at posterior edge, sometimes pigmented. Peristomium with a single pair of grooved dorsal tentacles arising from posterior margin or sometimes more posterior on an achaetous anterior segment, or rarely on an anterior setiger. First pair of branchiae arising near dorsal tentacles, an achaetous segment or first setiger; sometimes with first two pairs of branchiae on a single anterior segment. Body usually expanded anteriorly and narrowed posteriorly, middle or posterior body segments sometimes moniliform; posterior end often expanded. Setae include capillaries on most setigers and acicular spines in neuropodia and notopodia, with spines typically concentrated in posterior segments, usually forming distinct armature with spines carried on cinctured segments with elevated membranes; cinctures with few to many spines sometimes encircling entire posterior end, accompanied with none to many alternating capillaries; bidentate spines sometimes present in juveniles or occasionally in ventral-most position of far posterior setigers of adults, accompanying unidentate spines in cinctures; some species with long, natatory-like capillary notosetae, sometimes limited to gravid individuals. Pygidium a simple lobe, disklike, with long terminal cirrus, or few short lobes.

Remarks. Species of Chaetozone are recognized by having acicular spines in both noto- and neuropodia and with those of posterior segments frequently numerous and arranged in conspicuous spreading fascicles that often entirely encircle the body providing a characteristic armature. However, the species identified from the Atlantic slope and Georges Bank MMS surveys in the 1980s were classified according to the genera as defined by Hartman (1961, 1969). Effectively, any bitentaculate species having unidentate spines were referred to the genus Chaetozone . Because of this, several of the provisional taxa that were referred to Chaetozone from those surveys are now included in the genera Chaetocirratulus or Tharyx . Nevertheless, several species encountered in this study do have a reduced number of acicular spines that are not superficially conspicuous and as such are peripheral to the above definition. As part of this study, 12 species of Chaetozone , nine new to science are reported. In order to simplify the presentation of the 12 species of Chaetozone being reported here, they are grouped and arranged according to three categories with shared morphological characteristics. Each of these three categories or groups are introduced and discussed in order. The following 12 species of Chaetozone are treated in the present study:

The Chaetozone curvata group:

Chaetozone adunca n. sp.

Chaetozone anasima Doner & Blake, 2006

Chaetozone brychiata n. sp.

The Chaetozone gracilis group:

Chaetozone artaspinosa n. sp.

Chaetozone castouria n. sp.

Chaetozone novagracilis n. sp.

Chaetozone paucispinosa n. sp.

The Chaetozone setosa group:

Chaetozone diodonta Doner & Blake, 2006

Chaetozone donerae n. sp.

Chaetozone hystricosa Doner & Blake, 2006

Chaetozone lophia n. sp.

haetozone profunda n. sp.

The Chaetozone curvata group

Remarks. Chaetozone curvata Hartmann-Schröder, 1965 from nearshore habitats in Chile was the first species of Chaetozone to be described having acicular spines with a narrow filamentous tip that curves back and merges with the shaft. Subsequently, six additional species were described with this type of spine ( Blake 1996, 2006, 2015, 2018; Doner & Blake 2006; Dean & Blake 2007); two new species representing the eighth and ninth species in this group are reported in the present study; additional specimens of C. anasima are also reported and described. The two new species are the first from deep-water belonging to this group. The morphology of all nine species in the C. curvata group is compared in Table 3 .