Leodamas notoaciculatus, Blake, 2021

Blake, James A., 2021, New species and records of Orbiniidae (Annelida, Polychaeta) from continental shelf and slope depths of the Western North Atlantic Ocean, Zootaxa 4930 (1), pp. 1-123 : 67-70

Leodamas notoaciculatus new species

Figures 34–35

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Material examined. Atlantic Ocean, off New Jersey, coll. P.A. Neubert, Chief Scientist, 12 Aug 2008; Excalibur pipeline survey, Sta. 45B, 40°11.5618′N, 73°40.4949′W, 38 m, holotype ( MCZ 161598 ) .

Description. A small species, holotype complete, 2.5 mm long, 0.4 mm wide across thorax for 40 setigers. Body widest across thoracic setigers, gradually narrowing along abdominal segments ( Fig. 35A ). With nine thoracic setigers and branchiae from setiger 5 ( Fig. 34A ). Thoracic segments generally flattened, about five times wider than long; dorsum with narrow intersegmental grooves enlarged and elevated medially ( Fig. 34A ), grooves continuing on anterior abdominal setigers; venter with similar grooves and medial enlargement, but not as prominent ( Fig. 34B ). Abdominal segments about twice as wide as long along most of body, not as flattened as those of thorax and more rounded on venter; posterior setigers crowded. Color in alcohol opaque white.

Pre-setiger region oval, with large peristomium overlapping setiger 1 and part of setiger 2 dorsally and merging with setiger 1 ventrally ( Fig. 34 A–B). Prostomium relatively short, triangular; eyespots absent; nuchal organs not observed. Peristomium a single ring, with lateral folds and relatively smooth dorsal crest ( Figs. 34A , 35A ); ventrally surrounding mouth and forming upper and lower lips. Upper lip with two lateral and one medial lobe, not well defined; ventral lip a thick rim not divided into separate lobes ( Fig. 34B ). Proboscis not everted.

Thoracic notopodia with no postsetal lobes on setigers 1–2; a pair of long, thin, digitate postsetal lobes fully developed from setiger 3 ( Fig. 34A ); these continuing onto abdominal segments and along entire body. Thoracic neuropodia of setigers 1–6 with no visible postsetal lobe or lamellae; short, rounded, papillate postsetal lobe from setiger 7 ( Fig. 34A ), becoming longer and digitate by setiger 9. Transition to abdominal segments identified by loss of thoracic neuropodial uncini and thickening and elongation of neuropodium. Abdominal neuropodia initially a short thickened digitate lobe, entire apically; middle abdominal setigers developing short medially directed lobe; subpodial lobes absent; subpodial flanges short, closely adhering. Interramal cirri absent.

Branchiae from setiger 5, elongate, widest basally, tapering to narrow tip ( Fig. 34A ); subsequent thoracic and anterior abdominal branchiae elongate, widest basally, tapering to narrow apex ( Figs. 34A , 35A ), similar along entire length of body; all branchiae with lateral cilia along at least half their length.

Thoracic notosetae including long camerated capillaries ( Figs. 34A , 35 A–B) and 1–2 emergent acicular spines; capillaries numbering up to 5–8 in notopodia; acicular spines short, pointed ( Fig. 34I ). Thoracic neurosetae including 10–12 prominent uncini arranged into two rows ( Fig. 35 B–C) and 3–4 capillaries on posterior margin; uncini of first row of setigers 1–3 thinner, less robust than on following setigers; these uncini with 4–6 transverse rows of ribs along shaft ( Fig. 34D ); uncini of second row and all rows on setigers 4–9 larger, more robust, some with a distinct groove along concave margin and bordered with transverse ribs ( Fig. 34 E–F); some uncini smooth, lacking ribs ( Fig. 34G ). Abdominal notosetae including 3–7 capillaries, 1–2 emergent aciculae, and 1–2 furcate setae. Aciculae similar to those of thoracic notopodia; furcate setae with two unequal tynes, each tapering to pointed tip, with thin fibrils along inner margin extending inward toward opposite side ( Fig. 34J ). Abdominal neurosetae including 3–5 thin capillaries and 1–2 emergent aciculae, each acicula narrow, with narrow rounded tip ( Fig. 34H ). Flail setae not observed.

Pygidium with numerous elongate lobes surrounding anal opening; with two unusually long, thin anal cirri, these as long as one-third of entire body length ( Figs. 34C , 35A ).

Remarks. The single available specimen of Leodamas notoaciculatus n. sp. is likely a juvenile but has several unique characters not found heretofore in the genus: (1) the pre-setiger region is large, oval-shaped, and longer than the first five setigers, (2) setigers 1–2 entirely lack notopodial postsetal lobes; then long, digitate fully developed postsetal lobes appear on setiger 3 and continue along the entire body, (3) the furcate setae have unequal tynes that terminate in narrow, pointed tips. Most orbiniids have furcate setae with blunt-tipped tynes. While the presence of emergent and prominent aciculae in abdominal neuropodia is typical in the genus, L. notoaciculatus n. sp. also has emergent aciculae in both the thoracic and abdominal notopodia.

Based on the review presented by Blake (2017) and more recent species described by Sun et al. (2018) and Blake (2020) there are no close relatives to L. notoaciculatus n. sp. The lack of specimens of this species is surprising given the long timeframe of benthic studies along the US Atlantic coast. However, the species was collected from sediments having high sand content and these non-depositional sediments are not routinely sampled as part of offshore monitoring and reconnaissance programs.

Biology. Sediment grain size at Station 45B where Leodamas notoaciculatus n. sp. was collected consisted of 98% coarse sand, 0.7% silt, and 1.3% clay. The site was dominated by filter feeding amphipods and the polychaete Polygordius jouinae Ramey et al., 2006 .

Etymology. The epithet is derived from the Greek, noto for back or dorsum, and the Latin acicula for pin, referring to the notopodial acicula found in this species.

Distribution. U.S. Atlantic continental shelf, off New Jersey, 38 m.

Genus Califia Hartman, 1957 Emended

Type-species: Califia calida Hartman, 1957 , by monotypy.

Diagnosis. Prostomium pointed on anterior margin. Peristomium consisting of a single achaetous ring. Transition from thorax to abdomen abrupt due to distinct change in neuropodia. Branchiae from setiger 8–10; each branchia simple, lanceolate, may be lacking in most of abdominal region. Thoracic setae all capillaries; abdominal setigers 1–3 (rarely 4) with dense fascicles of thickened uncini in neuropodia and none to a few capillaries; subsequent thoracic neuropodia usually with all capillaries; one species with a few thin uncini and capillaries continuing to end of thorax. Neuropodial uncini of setigers 1–3 with shafts either smooth or with ribs; tip of shaft with distinct sheath, often frayed, appearing bristled in light microscopy. Neuropodia with or without postsetal lobe; subpodial lobes absent. Abdominal segments lacking interramal and ventral cirri. Abdominal setae including capillaries, furcate setae, and flail setae; no uncini. Pygidium a rounded lobe with two anal cirri.

Remarks. Califia is a small genus with only five known species ( Blake 2017, 2020). Species of Califia are characterized by having heavy spines or uncini in the first three thoracic neuropodia and few transitional spines in setiger 4 (or typically, spines lacking). One species, C. bilamellata Blake, 2017 , has a few thin thoracic neuropodial uncini with ribs along the shaft and capillaries continuing from setiger 4 to the end of the thorax. The heavy spines provide setigers 1–3 with a different appearance relative to the subsequent thoracic segments that have only capillaries or only a few similar spines. Pettibone (1957) noted that a few transitional spines were sometimes present among the capillaries of the unmodified setiger 4 of C. schmitti (Pettibone, 1957) ; Blake (2017) observed extra spines on setigers 4–5 of the holotype of C. chilensis Hartman, 1967 and transitional spines have been observed in setiger 4 of C. calida by Blake (1996, 2020). However, the presence and number of extra neuropodial spines after setiger 3 is variable. In the present study, numerous specimens of C. schmitti were collected as part of the ACSAR program in slope depths off the U.S. Atlantic coast. One specimen was observed with extra spines on setiger 4 ( Fig. 37C ).

Figures

FIGURE 34. Leodamas notoaciculatus n. sp. Holotype (MCZ 161598): A, anterior end, dorsal view; B, anterior end, ventral view; C, posterior end, dorsal view; D–G, neuropodial uncini from thoracic setigers: setiger 1 (D), setiger 3 (E), setiger 5 (F); setiger 7 (G); H, abdominal neuropodial acicula; I, thoracic notopodial acicula; J, abdominal notopodial furcate seta.

FIGURE 35. Leodamas notoaciculatus n. sp. Holotype (MCZ 161598): A, entire worm, dorsal view; B, setigers 1–7, dorsal view of neuropodial uncini; C, setigers 3–4, dorsal view of neuropodial uncini. All stained with Shirlastain A.

FIGURE 37. Califia schmitti (Pettibone, 1957). A, anterior end, left lateral view; B, same, detail of thoracic setigers 2–3; C, Anterior end, ventral view of first 7 setigers of specimen with modified neurosetae on setigers 1–4 on one side and setigers 1–3 on other side; D, thoracic setiger 9, anterior view; E, modified neuropodial uncini from anterior row of setiger 2; F–G, modified neuropodial uncini from posterior row, setiger 2. A–B (USNM 1622247); C, (USNM 1622217); D–G (USNM 1622247). All stained with Shirlastain A. Numbers identify setigers with modified neurosetae.