Amphictene uniloba, Hutchings & Peart, 2002

Hutchings, P. & Peart, R., 2002, A Review of the Genera of Pectinariidae (Polychaeta) Together with a Description of the Australian Fauna, Records of the Australian Museum 54, pp. 99-127 : 105-108

Amphictene uniloba n.sp.

Figs. 4C–D, 5C–D, 6, 7A–B, 8A–C, Tables 1, 6

Type material. HOLOTYPE: AM W25612*, 29 mm long, 4 & 2 mm wide . PARATYPES: 3, AM W25613*, 28–33 mm long, 5–6 & 2–3 mm wide; 2, BMNH 2001.68– 69 *, 31–32

mm long, 5–6 & 2–3 mm wide; 2, LACM-AHF POLY 2059*, 20–32 mm long, 5 & 3 mm wide; 2, USNM 187085 *, 28–35 mm long, 5 & 3 mm wide. All material collected by John McIntyre, 5.xii.1965.

Type locality. New South Wales: near Cronulla, Jibbon Beach , 34°03'S 151°09'E, 60–100 m.

Additional material examined. QUEENSLAND: Pallarenda Beach , N of Townsville, 19°12'S 146°46'E, 11.xi.1977, 0.1 m, 1, AM W18121 *. NEW SOUTH WALES: Port Stephens , 32°42'S 152°06'E, ix.1908, 1, AM G11197*. Material examined varied from 20 to 45 mm long & 4 to 6 mm & 2 to 3 mm wide .

Description. Preserved specimen grey to pale cream in colour; small, conical in shape. Tube straight, composed of cemented sand grains.

Rim of cephalic veil with 16 long, narrow, triangular cirri, tapering, with thread-like tips. Cephalic veil completely free from operculum forming dorsal semicircular lobe covering bases of numerous peristomial palps present. Raised opercular margin well developed, divided into 24 triangular lappets. Operculum with 14 pairs of paleae, long, yellow-gold, subacute, curved dorsally, with extended tips ( Fig. 7A).

First pair of tentacular cirri arise on anterior margin of segment 2. Second pair of tentacular cirri present on segment 3, arise from a connecting ridge which runs across the venter, margins of ridge incised forming glandular lobes. Segment 2 without anterodorsal lobe. Chaetiger 2 (segment 6) with large, anteroventral lobe, broad, with anterior margin of lobe smooth, lobe thin and almost transparent.

Two pairs of comb-like, stalked branchiae on segments 3 and 4, situated laterally and consisting of loose flat, lamellae.Anterior pair situated more ventrally than posterior pair, and larger than posterior pair. Branchiae lie flattened against the body.

Chaetigers 1 to 3 (segments 5 to 7) with notopodia only. Parapodia biramous with both notopodia, neuropodia, notochaetae and neurochaetae on chaetigers 4 to 16. Chaetiger 17 with notopodia and notochaetae only. Notopodia of chaetigers 1 to 3 and 15 to 17 reduced in size, and associated notochaetae also reduced in size and length compared to notosetae on chaetigers 4 to 14. All notochaetae simple, smooth-tipped capillaries, with finely hirsute surfaces, and varying from ones with finely pointed tips to those with strongly curved tips and some with pectinated margins ( Figs. 4C–D, 8A), all of which may be present in the same fascicle. Neuropodia wedge-shaped, slightly glandular, erect tori with numerous neurochaetae. Neurochaetal uncini with major teeth arranged in two longitudinal rows of teeth each with about 8 teeth per row, with size of teeth declining basally ( Figs. 5C, 8B–C).

Posterior 5 segments fused to form a flattened plate or scaphe, broader than long. Scaphe with an anal flap and dorsal papilla present, and with crenulated, lobed margins ( Fig. 7B). Scaphal hooks present, 6 pairs, fine, small and brown ( Fig. 5D).

Venter of segments 1 to 6 glandular, raised and corrugated. Chaetigers 7 to 20 with prominent oval to rectangular glandular patches present ventrolaterally. Nephridial papillae present on segment 5 (chaetiger 1), situated ventrolaterally just below base of second pair of branchiae.

Variation. The number of cirri on the cephalic veil ranges from 11 to 21; the number of triangular lappets on the raised opercular margin varies from 21 to 31 lappets; the relative size of the two pairs of branchiae differ, either being similar in size or with the anterior pair larger. The number of pairs of scaphal hooks varies from 4 to 10 and the development of the glandular areas varies between individuals. Larger animals have more cirri, lappets and scaphal hooks than smaller animals. The relative proportions of the scaphe varies between individuals. It may be as long as broad or longer than broad. This may be an artifact of preservation.

Remarks. Amphictene uniloba n.sp. can be distinguished from all other described species of Amphictene by the following combination of characters: relatively small number of cirri on the cephalic veil (11 to 21), 14 pairs of paleae and 4 to 10 pairs of scaphal hooks present (see Table 1). The species most closely resembles A. japonica Nilsson, 1928 , in terms of the number of cirri on the cephalic veil but differs in the number of pairs of paleae present. Table 1 shows that several described species are poorly known with no indication given of the amount of variation exhibited for individual characters. This study, which examined a large amount of material, revealed that some characters such as the number of cirri on the cephalic veil, the number of pairs of cirri on the opercular rim and the number of pairs of scaphal hooks vary according to size of the individual and thus presumably with age. Future studies of the group must consider these size related variations.

Amphictene uniloba can be distinguished from the other Australian species A. favona by the number of cirri present on the cephalic veil. Amphictene uniloba has fewer cirri (11 to 21) than A. favona , which has 23 to 28, and the number of pairs of paleae differs, A. uniloba having 14 and A. favona having 12 pairs. Both species occur on the east coast of Australia but A. favona also occurs on the northwest coast (see Fig. 6).

Etymology. The specific name uniloba refers to the single anteroventral lobe present on chaetiger 2 and is derived from the latin word unus.

Distribution. Eastern Australia; known only from Jibbon Beach, Port Stephens, NSW and Townsville, Qld ( Fig. 6).

Habitat. Intertidal to 100 m depth, no sediment data available.