New Species of Cirratulidae (Annelida) from Continental Slope and Abyssal Depths off Eastern Australia Author Blake, James A. text Records of the Australian Museum 2023 Rec. Aust. Mus. 2023-05-17 75 3 249 270 http://dx.doi.org/10.3853/j.2201-4349.75.2023.1799 journal article 10.3853/j.2201-4349.75.2023.1799 2201-4349 10414165 7D3BDF25-010F-41A4-AD15-763C3F067D8A Chaetocirratulus glebalis sp. nov. urn:lsid:zoobank.org:act: 62BD4E47-1F83-46C5-BAFD-6BCF6AC4C2F8 Figs 5–6 Holotype : Abyssal plain off eastern Australia , between Victoria and Tasmania , Bass Strait Marine Park , RV Investigator , Sta. 031, coll. 23 May 2017 , Brenke sledge, 39.422°S 149.604°E to 39.391°S 149.597°E , 4170 m ( AM W.53524) . Paratypes (3): same data as holotype (3, AM W.53525) . Description . All specimens incomplete, including four anterior fragments and one posterior fragment. Holotype largest specimen, with 60 setigers, 10.6 mm long, 0.9 mm wide across anterior setigers; largest paratype with 25 setigers, 3.0 mm long, 1.0 wide. Body with thick, crowded segments along entire body ( Figs 5A–B , 6C–E ); individual segments up to ten times wider than long.Anterior segments with transverse lumpy dorsal ridge ( Fig. 5A ), but without longitudinal grooves or ridges; venter with prominent mid-ventral ridge along entire body composed of broad medial bulge on each segment ( Figs 5B , 6B ), connected mid-ventrally at intersegmental groove. One paratype a mature female with large eggs in two swollen posteriormost setigers of fragment ( Fig. 6C–D ). Eggs 160–200 µm in longest diameter. Colour in alcohol tan without any obvious pigment. Pre-setiger region broad, thickened, with prostomium curved ventrally, not visible in dorsal view ( Fig. 5A–B ). Prostomium a short, pear-shaped lobe, broadly rounded across anterior margin ( Figs 5B , 6B ); eyespots absent; nuchal organs curved grooves on lateral margins ( Fig. 5B ). Peristomium with two irregularly-shaped rings, each with unique morphology: (1) anteriormost ring bulbous, encircling prostomium and mouth ( Fig. 5B ), bearing fan-shaped dorsal crest ( Figs 5A , 6A, C ); (2) second ring consisting of an irregular series of lobes that overall merge with setiger 1; mid-dorsal lobe swollen, with a pair of grooves on anterior margin with notch containing scar representing origin of dorsal tentacles ( Fig. 5A ); ventral side with broad semi-circular crest extending posteriorly over setigers 1–2 ( Fig. 5B ). Parapodia of anterior setigers elongate rounded lateral lobes from which setae emerge; reduced to narrow ridge in middle and posterior setigers ( Fig. 5C ); pre- and post-setal lobes entirely absent. Branchiae from setiger 1, dorsal to notosetae, continuing to at least mid-body; branchiae mostly missing, but represented by scars and stubs. Noto- and neurosetae include long thin capillaries throughout, including a few long natatory-like setae ( Fig. 6C ) and few narrow acicular spines in far posterior setigers ( Fig. 5C ). Capillaries of anterior setigers numbering 6–8 in notopodia and 9–10 in neuropodia; middle setigers with 7–9 capillaries in notopodia and 8–10 in neuropodia. Acicular spines not present in short paratypes , but present from about setiger 55 in holotype , with 2–3 spines in neuropodia and 0–1 in notopodia. Posterior fragment with pre-pygidial segments with up to six spines in neuropodia and 2–3 in notopodia ( Fig. 5C ). Individual spines narrow, weakly curved, tapering to narrow rounded tip ( Fig. 5D ). Posterior fragment narrowing to short conical pygidial lobe. Methyl Green staining . No general pattern, however intersegmental grooves retain stain to varying degrees ( Fig. 6D–E, arrows), with dorsal surface of some middle and posterior segments staining lightly. Remarks . Chaetocirratulus glebalis sp. nov. is an entirely unique cirratulid in the nature of the numerous lobes and lumps on the pre-setiger region and on the body segments. The species is referred to Chaetocirratulus because of the relatively thickened body, short anteriorly rounded pre-setiger region and hidden nature of the prostomium. I know of no other cirratulids from deep water or shallower depths with a similar appearance. The morphology and arrangement of the acicular spines is, however, similar to some species of Chaetozone , except that posterior segments do not have cinctures and the spines are not large nor sigmoid in shape. Biology . The large protruding eggs (160–200 µm) on the paratype suggest direct or lecithotrophic development, which would be expected for an abyssal species. However, long natatory-like capillaries might suggest a mechanism for movement at the sediment-water interface at the time of spawning. The short, blunted pre-setiger region suggests that the species burrows by pushing particles out the way and opening cracks in the sediment rather than moving between particles. Etymology . The epithet is from the Latin, gleba for lump, in reference to the lumpy segmental appearance of the body of this species. Distribution . Abyssal plain between Victoria and Tasmania , eastern Australia , 4170 m .