Amphictene favona Hutchings & Peart, 2002

Zhang, Jinghuai & Hutchings, Pat, 2019, A revision of Australian Pectinariidae (Polychaeta), with new species and new records, Zootaxa 4611 (1), pp. 1-70 : 7-14

Amphictene favona Hutchings & Peart, 2002

Figs 4–5 , Table 1

Amphictene favona Hutchings & Peart, 2002: 99 – 127 , figs 2 – 5.

Material examined. Australia, Western Australia: AM W.25611 (Holotype), Houtman Abrolhos, Wallabi Group, 28°32’35”S 113°46’32”E, 45 m, white bleached coral algal nodules (rhodoliths), coll. P.A. Hutchings, 28 May 1994 ; AM W.25403 (Paratypes), 11 specs, Wallabi Group, Houtman Abrolhos, 28°36’31”S 113°44’56”E, 46 m, bleached rubble and sponges, coll. P.A. Hutchings, 28 May 1994 .

Additional material examined. Australia, Western Australia: AM W.2842, 1 spec., between Broome & Wallal, 18°58’S 121°14’E, 13 m, coll. R. Bourne, Sep 1931 ; AM W.5493, 1 spec., Point Samson , 20°38’S 117°12’E, low tide, sandy mud, coll. N. Coleman, 26 Sep 1972 . Queensland: AM W.2317, 2 specs, Michaelmas Cay, off Cairns , 16°30’S 146°02’E, coll. T. Iredale & F.A. McNeill, Jun 1926 ; AM W.25404, 1 spec., Michaelmas Reef, No. 2 Sandbank , near Cairns , 16°35’S 146°02’E, coll. I. Loch, 07 Aug 1971 ; AM W.3150, 1 spec., Hayman Island , 20°03’S 148°53’E ; AM W.5611, 1 spec., Brampton Island , 20°49’S 149°17’E, 1949 ; AM W.25405, 1 spec., Capricorn Group, One Tree Island, First lagoon, 23°30’S 152°05’E, 1 m, near piecrust, coll. F. Talbot & Party, 04 Oct 1967 .

Description. Based on all specimens examined. Preserved specimens pale reddish in colour, conical in shape ( Fig. 4B, C ). Body length 37.6 – 97.0 mm (holotype 52.0 mm) including paleae and scaphe, width 9.0 – 23.0 mm (holotype 15.0 mm) at cephalic regions.

Cephalic veil oval, free from operculum, with 21 – 33 (holotype 23) smooth cirri on anterior margin and present on about 2/3 of lateral margins ( Fig. 4C ). Pair of ear-shaped lobes adjacent to both sides of dorsal base of cephalic veil. Buccal tentacles with deep median longitudinal grooves, arising posterior to cephalic veil ( Fig. 4C ).

Operculum semicircular; dorsal and lateral margin well developed, with 44 – 63 (holotype 62) triangular lappets; ventral margin (opercular ridge) with 10 – 16 (holotype 12) pairs of stout, short and golden paleae, weakly curved dorsally, blunt end without extended tips ( Fig. 4B – D ).

First pair of tentacular cirri short not extending beyond tips of paleae, with annuli, arising from connection of opercular margin and paleal ridge ( Fig. 4B – C ). Pair of small ventral lappets present behind tentacular cirri, near cephalic veil, on segment 1. Ventral region of segment 1 covered by buccal tentacles and ventral lobes of segment 2 ( Fig. 4C ).

Second pair of tentacular cirri extending to opercular margin, with annuli, on latero-median connecting ridge on segment 2, inserted more dorsally than 1 st pair of tentacular cirri ( Fig. 4B – C ). Segment 2 with ventral lobes as pair of narrow ventro-lateral lobes separated by shallow grooves from base of 2 nd pair of tentacular cirri, and pair of broad mid-ventral lobes about twice as wide as ventro-lateral lobes ( Fig. 4C ). A dorsal lobe with slightly crenulate margin present on segment 2, separated by grooves from base of 2 nd pair of tentacular cirri ( Fig. 4B, D ).

Comb-like branchiae on segments 3 – 4, consisting of series of dense, flat lamellae ( Fig. 4B – C ). Branchiae on segment 3 larger and inserted more ventrally than those of segment 4. Pair of small dorso-lateral glandular pads present adjacent to branchiae on segments 3 and 4 ( Fig. 4B, D ).

Distinct ventral glandular lobes present on segments 3 – 6, becoming progressively more lateral and broader on segments 3 – 5 ( Fig. 4C ). Hump present near branchiae on segment 4. Segment 3 only with broad ventral lobe ( Fig. 4C ). Segment 4 with pair of broad ventro-lateral lobes near branchiae and narrow mid-ventral lobe about 2/3 width of ventro-lateral lobes, separated from those by shallow grooves. Segment 5 with pair of broad ventro-lateral lobes and narrow mid-ventral lobe about 1/3 width of ventro-lateral lobes, separated from those by shallow grooves, usually covered by ventral lobes of segment 6 ( Fig. 4C ). Segment 6 with pair of ventral lobes with contiguous rounded papillae, separated from each other by broad and deep medial groove ( Fig. 4C ).

Notopodia other than those of segment 1 which bear paleae, on segments 5 – 21 (17 pairs), each bearing two kinds of chaetae; one winged, bordered with serrations along distal portion, covered progressively with more spines from about middle to front of wing, on anterior surface; other stout and straight, tapering to an acute tip, covered progressively with more spines from mid-anterior portion to tip, on anterior surface ( Figs 4B – C ; 5A – C ). Neuropodia, 13 pairs on segments 8 – 20, each with a slightly raised torus with transverse row of uncini; each uncinus with U-shaped anterior peg embedded into torus, several rows of minor teeth, and two longitudinal rows of major teeth, each with about eight teeth ( Figs 4B – C ; 5D – E ). Segment 21 with pair of ventro-lateral lobes near notopodia ( Fig. 4B – C ).

Scaphe wide ovoidal, flattened dorsally, divided anteriorly into four narrow lobes and posteriorly with two rounded lobes on each lateral margin ( Fig. 4B – C ). Anal flap wide, fused forming tongue-like structure with short anal cirrus, distal margin with contiguous rounded lappets ( Fig. 4F ). Scaphal hooks 11 – 20 (holotype 11) pairs, amber, with blunt end, straight and slightly bent towards tip ( Fig. 4E ).

Tube with wide opening, slightly curved, solid wall made of large coral sand grains ( Fig. 4A ).

Methyl Green stained body distinctly green on cirri on cephalic veil, ventral lobes of segments 2–6, dorsal lobe of segment 2, dorso-lateral pads of segments 3–4, neuropodia, ventro-lateral regions adjacent to neuropodia, dorsolateral and ventro-lateral regions of segment 21, margins of scaphe, and dorsum of anal flap except for anal cirri and margin ( Fig. 4 B–C). Additionally, ventro-lateral regions with continuous transverse green dots on segments 20–21 ( Fig. 4B ).

Distribution. NW Western Australia, Queensland ( Fig. 1 ).

Habitat. Found amongst rhodoliths, sandy mud or rubble from low tide to 46 m depth.

Remarks. We have expanded the original description of Amphictene favona Hutchings & Peart, 2002 , and provided additional images of the holotype and details on some morphological characters which were not included in the original description. These include a pair of lateral ear-shaped lobes adjacent to both sides of dorsal base of cephalic veil, pair of small ventral lappets on segment 1, pair of small dorso-lateral glandular pads on segments 3 and 4, ventral lobes on segments 3–6, U-shaped anterior peg on uncini and a more complete description of the scaphal lateral lobes. The number of paleae significantly increase with increasing body size, but the number of cirri on cephalic veil and scaphal hooks does not significantly vary with body size ( Fig. 6 ). Amphictene favona can be easily distinguished from all other Australian Amphictene species by having blunt paleae, a dorsal lobe on segment 2, segment 6 with ventral lobes having contiguous rounded papillae, uncini with two longitudinal rows of teeth and 11 – 20 pairs of blunt straight scaphal hooks (Table 1). The tubes of A. favona are robust, white and made up of large coral sand grains. Amphictene favona is similar to Amphictene crassa ( Grube, 1870) described from New Caledonia, which also has blunt paleae, a dorsal lobe on segment 2, as well as ventral lobes with contiguous rounded papillae, uncini with two longitudinal rows of major teeth and a tube made from coral sand grains, but differs in the number of pairs of scaphal hooks present, less than nine pairs in A. crassa whereas A. favona has 11 – 20 pairs.

Figures

FIGURE 1. Distribution of the species of Amphictene, Lagis and Pectinaria in Australia.

FIGURE 4. Amphictene favona Hutchings & Peart, 2002. A. Tube (AM W.2317). Methyl Green stained body of Holotype (AM W.25611); B. Dorso-lateral view of entire body; C. Ventral view of entire body; D. Dorsal view of anterior end; E. Scaphal hooks; F. Close up of anal flap. Abbreviations: ac, anal cirrus; af, anal flap; br, branchiae; bt, buccal tentacles; cv, cephalic veil; dl, dorsal lobe; dlp, dorso-lateral pads; nec, neurochaetae; noc, notochaetae; op, operculum; or, opercular rim; p, paleae; s, segment; sc, scaphe; sh, scaphal hooks; tc, tentacular cirri.

FIGURE 5. Amphictene favona Hutchings & Peart, 2002. Chaetae (Paratype AM W.25403): A–C. Close up of notochaetae, segment 11; D–E. Uncini, segment 11.

FIGURE 6. Relationship between body width and body length, number of cirri on cephalic veil, number of paleae, number of scaphal hooks, on Amphictene favona Hutchings & Peart, 2002.