Chaetozone gracilis

The Chaetozone gracilis group

Remarks. Chaetozone gracilis (Moore, 1923) from deep-water off southern California was redescribed by Blake (1996) and represents an atypical species of Chaetozone in that the acicular spines in the noto- and neuropodia are reduced in number and not formed into the distinctive cinctures or the posterior armature typical of most species in the genus. Other atypical species of Chaetozone having reduced numbers of acicular spines not forming prominent posterior cinctures are Chaetozone homosetosa (Hartmann-Schroder & Rosenfeldt, 1989) from Antarctica and Chaetozone castanea Blake, 1918 from off Peru. These species are not included among species of Chaetocirratulus because their bodies are elongate and only expanded in the anterior segments rather than having thickened fusiform or sausage-shaped bodies. In addition, the prostomium is long, narrow and pointed rather than broad, rounded, or wedge-shaped as in species of Chaetocirratulus. Blake (2018: 121) prematurely referred Chaetozone gracilis to Chaetocirratulus. However, it is evident this species does not have the prostomium and body shape typical of Chaetocirratulus and is here retained in Chaetozone.

In the present study, four new species having a reduced number of acicular spines not forming cinctures in posterior parapodia were discovered off the U.S. Atlantic coast and are referred to Chaetozone. One is from shallow subtidal sediments in Boston Harbor whereas three others were discovered in deep water on the U.S. Atlantic continental slope. All four are described here.