Paleanotus Schmarda, 1861

Watson, Charlotte, 2015, Seven new species of Paleanotus (Annelida: Chrysopetalidae) described from Lizard Island, Great Barrier Reef, and coral reefs of northern Australia and the Indo-Pacific: two cryptic species pairs revealed between western Pacific Ocean and the eastern Indian Ocean, Zootaxa 4019 (1), pp. 707-732 : 710-711

Genus Paleanotus Schmarda, 1861

Type-species. Paleanotus chrysolepis Schmarda, 1861

Diagnosis. Elongate body (to 70 segments) with partly retractile anterior three segments in conjunction with flexible nuchal fold. Prostomium with two pairs of large red eyes, single subulate median antenna, two lateral antennae, two short, ovoid palps insert ventrally. Broad, barrel-shaped proboscis with terminal papillae, pair of brown tipped stylets, triangular mouth flap. Segment 1 reduced, achaetous, with two pairs of dorsal and ventral tentacular cirri. Segments 2 and 3 fused in part. Segment 2 biramous with dorsal cirri, small notochaetal fascicle, neuropodia with spinigerous neurochaetae; ventral cirri absent. Segment 3 onwards with all notochaetal and neurochaetal types, dorsal and ventral cirri. Mid-body notopodia with dorsal cirri, lateral, main and median notochaetal paleal fascicles. Main paleae in single fan; paleae broad, asymmetrical with small hooked apices, with or without raised denticulate ribs. Median paleae interlock in mid-dorsal line forming shallow but distinct convex median ridge. Median palae asymmetrical or symmetrical in shape; with or without raised, denticulate ribs. Midbody neuropodia with short, subulate ventral cirri, falcigerous neurochaetae with blades grading in size from longer in superior position to shorter, slender blades in inferior position. Pygidium quadrate with two small anal cirri. Cilia present inter-ramally; horizontal or ‘flower’ shaped enlarged glands occur adjacent to dorsal ceratophore in mature specimens.

Remarks. Paleanotus was incorrectly synonymised with Chrysopetalum by Day (1967). The two genera are clearly distinguished by differences of the anterior end and characteristic notochaetal types. Perkins (1985) recognized Paleanotus and Chrysopetalum as distinct genera and created two new chrysopetalid genera, Treptopale and Hyalopale from Florida reefs. These latter two taxa are closely related to Paleanotus with similar anterior end configurations and chaetal types. Species of Paleanotus are distinguished from Treptopale by the possession of predominantly asymmetrical notochaetal paleae and from species of Hyalopale with a full complement of paleal notochaetal types ( Perkins 1985; key, this paper).

Paleanotus species are found among interstices of coral and rocky reefs; dead shell middens on sand or mud; fouling accretions on wooden platforms or hulls of boats; branchial chambers of molluscs and crustaceans; among Mytilus , bryzoan, tunicate and algal encrusting communities on jetty piers; and associated with tubiculous polychaete colonies. Paleanotus species possess a pair of stylets with brown-coloured roughened distal tips, like sandpaper, that can rasp away at prey. Habitat and stylet structure indicates both a scavenging and quasicommensal mode of life (CW, per.obs.).

Paleanotus has a specific arrangement of cirri of the anterior three segments and a degree of retractability of these segments in association with a flexible nuchal fold; a pattern in common with that observed in the majority of Chrysopetalinae taxa. The prostomium appears fused between the anterior three segments with the following cirri pattern: segment 1 with two pairs of cirri; segment 2 with dorsal cirri, notochaetae, neurochaetae but ventral cirri absent; segment 3 with dorsal cirri, notochaetae, neurochaetae and ventral cirri present ( Fig. 8 A). Retraction of the anterior end makes the position of tentacular ventral cirri variable; anterior, adjacent or slightly posterior to the palps.

Distinctive glands in mature Paleanotus males and females are described for the first time. Horizontal, elongate, granular textured glands and ‘flower’ shaped glands are observed within the notopodia posterior to the dorsal ceratophore; associated oil globules are also found ( Figs 2 H, I; 4A, I; 6D). Inter-ramal cilia appear longer in mature specimens and parapodial white pigmentation and ‘white granules’ are seen in the males of one species. These latter structures have been described for mature specimens in the related taxon Treptopale ( Watson 2010) .

Figures

FIGURE 2. Paleanotus inornatus n. sp. A. Notopodium in part and neuropodium, NTM W. 23684: MacGillivray Reef, GBR; B. Median paleae and medial main paleae, NTM W. 25390: Day Reef, GBR; C – G: Neurochaetal types, NTM W. 23684: MacGillivray Reef, GBR; H. Male, notopodium and neuropodium (neurochaetae omitted), NTM W. 23726: Ningaloo Reef, WA; I. Ovigerous female, notopodium, CAS 185685: Philippines. Abbreviations: e = egg, gl = gland, la = lateral paleae, me = median paleae, sp = sperm. Scale bars: B = 30 µm, C – G = 10 µm, H = 100 µm.

FIGURE 8. Paleanotus chrysos n. sp. A – E: NTM W. 23688: Yonge Reef, GBR. A. Anterior end, dorsal view (paleal notochaetae omitted); B. Paleae, segment 2; C. Detail lateral paleae, spine and main paleae; D. Median paleae and medial main palea; E. Micropic, median palea; F – J: Neurochaetal types, NTM W. 23203: North Direction Island, GBR; K. Micropic of midbody segment, SMNH 97309: New Caledonia; L. Detail of median paleae, medial-most main palea, NTM W. 23190: Heron Island, GBR. Abbreviations: ca = caruncle, la = lateral paleae, me = median paleae. Scale bars: A = 200 µm, B – D, F – J, L = 30 µm.