Caulleriella Chamberlin 1919

Genus Caulleriella Chamberlin, 1919

Type species: Cirratulus viridis Langerhans, 1881. Original designation by Chamberlin 1919.

Diagnosis. (after Blake & Magalhães 2019). Prostomium elongate, conical to pointed; peristomium elongated to short, dorsal tentacles usually beginning anterior to setiger 1. Middle body segments not beaded; parapodia often with noto- and neuropodia widely separated laterally. Modified setae including capillaries and bidentate, crotchetlike hooks, not arranged into modified cinctures. In some species, unidentate hooks may occur in some regions of the body in addition to bidentate hooks. Pygidium either a simple conical lobe or with one or two anal cirri.

Remarks. To date, approximately 45 species of Caulleriella are known (Read & Fauchald 2020; Blake & Magalhães 2019). The current definition of the genus essentially dates from Blake (1996), who, among other things, determined that in addition to having bidentate hooks, most species of Caulleriella differ from other bitentaculate cirratulids in having the noto- and neuropodia widely separated from one another along the body; this generalization, however, does not hold up in species that have long, narrow threadlike bodies.

Bidentate hooks. Three types of bidentate hooks have been reported for species of Caulleriella. (1) One type is a typical bidentate crotchet, found in most species, where the apical tooth appears to emerge directly from the end of shaft with no hood or flange along the shaft. This type of hook is characteristic of most species. (2) A second type of hook has a hood or flange on the convex side of the shaft that extends apically forming the apical tooth. This type of seta was first described for C. alata by Southern (1914). Although not stated, Southern’s name for the species appears to be derived from alatus, Latin for winged and refers directly to the transparent hood on the convex side of the shaft that merges with the apical tooth. These ‘alate’ hooks have been reported in nine species of Caulleriella (see list in Discussion section) and likely occur in others where details of the bidentate teeth are not well described. (3) A third type of hook has a transparent hood that extends from the main fang to the concave side of the shaft, similar to hoods found in some spionids and paraonids. This type of hook is only known from C. bathytata Blake, 2019 an abyssal species from the Pacific Ocean.

The nature of the ‘alate’ hooks is not well understood. There is some evidence that the so-called hood or flange on the convex side of the shaft is actually an artifact of the shaft having a groove on the lateral or convex side and that a change in thickness along the shaft produces a lighter or more transparent area that is the ‘hood’ observed in light microscopy. Likewise, details of ‘alate’ hooks suggest that the apical tooth may actually be a projecting ridge or an extension of the shaft that only appears as a tooth when observed in lateral view. Caulleriella kacya e Blake, 2018 from the Weddell Sea, Antarctica has a broad accessory sheath on the convex side of the shaft that terminates on the tip of the shaft as a ridge above the main fang; in some views this sheath appears to be divided producing a tridentate appearance (Blake 2018). The ‘alate’ bidentate hooks of C. pacifica E. Berkeley, 1929 were illustrated with SEM by Magalhães & Bailey-Brock (2015). The convex side of the curved shaft has a distinct channel or groove that could appear as the hood in light microscopy at certain angles. In addition, the apical tooth is short and appears to be a low ridge. In contrast the SEMs of the bidentate hooks of C. venefica Doner & Blake, 2006 (see Figure 8 in C. venefica section below) show no evidence of a groove along the shaft and the apical tooth is narrow and pointed. These observations suggest that an in-depth investigation of these hooks may yield additional characters useful in species delimitation.

Parapodia. Most species of Caulleriella have the noto- and neuropodia widely separated along the body (Blake 1996; Blake & Magalhães 2019); in some species such C. quadrata Blake & Dean, 2019, the podia are so widely separated they appear at four corners of the body when viewed in cross section (Blake & Dean 2019). This generalization, however, is not as obvious in deep-water species where the bodies are long and thin; however, even in these taxa, the podial lobes are distinctly separated from one another rather than being close as in species of Tharyx.

Bathymetry. Recent studies have added numerous new species of Caulleriella and expanded descriptions of others (Blake 2018, 2019; Blake & Dean 2019). However, only five of the 45 previously known species of Caulleriella, four from around Antarctica and one from the abyssal Pacific, are known from depths of 500 m or greater (Blake 2018, 2019): C. antarctica (Hartman, 1978) (1120 m), C. bathytata Blake, 2019 (4877 m), C. eltaninae Blake, 2018 (870 m), C. fimbriata Blake, 2018, (1884 m), and C. kacyae Blake, 2018 (1035 m). Three additional deepwater and one shallow water species of Caulleriella are newly described in the present study bringing the number of known species for the genus to 49 of which only eight occur in deep water. Additional records and descriptive comments for Caulleriella venefica, a widespread nearshore and continental shelf species along the U.S. Atlantic coast, are also provided. In addition several specimens of an additional small species of Caulleriella, are reported from rocky habitats in Cape Cod Bay. These specimens are not named but may be conspecific with or related to C. fragilis (Leidy, 1855), which has not been described since the original report. The following species are treated in this study.

1. Caulleriella filiformia n. sp.

2. Caulleriella nobska n. sp.

3. Caulleriella pintada n. sp.

4. Caulleriella rodmani n. sp.

5. Caulleriella venefica Doner & Blake, 2006

6. Caulleriella sp.