Amphictene cercusa, Zhang & Hutchings, 2019

Zhang, Jinghuai & Hutchings, Pat, 2019, A revision of Australian Pectinariidae (Polychaeta), with new species and new records, Zootaxa 4611 (1), pp. 1-70 : 19-23

Amphictene cercusa n. sp.

Figs 10–12 , Table 1

Material examined. Australia, Queensland: Holotype: AM W.18121, Pallarenda Beach, N of Townsville , 19°12’S, 146°46’E, intertidal, coll. R. Muffley, 11 Nov 1977.

Description. Holotype, pale reddish in colour after preservation, long barrel in shape ( Fig. 11A – B ). Body length 33.0 mm including paleae and scaphe, width 3.0 mm at cephalic regions ( Fig. 11A – B ).

Cephalic veil oval, broken, free from operculum, with smooth cirri on anterior margin and 2/3 lateral margin ( Figs 10B ; 11A, D ). Pair of ear-shaped lobes adjacent to both sides of dorsal base of cephalic veil. Buccal tentacles arising from posterior to cephalic veil, but most detached ( Figs 10B ; 11A, D ).

Operculum semicircular; dorsal and lateral margin well developed, with 27 triangular lappets or cirri; ventral margin (opercular ridge) with nine pairs of golden paleae, curved dorsally, acute with extended tips ( Figs 10A ; 11B – C, E ).

First pair of tentacular cirri extending beyond paleae, with annuli, arising from connection of opercular margin and paleal ridge ( Figs 10A – B ; 11A, C ). Pair of small ventral lappets present behind tentacular cirri, near cephalic veil, on segment 1 ( Figs 10B ; 11D ). Ventral region of segment 1 covered by ventral lobes of segment 2 ( Figs 10B ; 11D ).

Second pair of tentacular cirri with annuli, extending beyond opercular margin, on latero-median connecting ridge on segment 2, inserted more dorsally than 1 st pair of tentacular cirri ( Figs 10A ; 11C, E ). Segment 2 with ventral lobes as pair of broad ventro-lateral lobes separated by grooves from base of 2 nd pair of tentacular cirri, and narrow mid-ventral lobe with pair of swellings, about 1/2 width of ventro-lateral lobes ( Figs 10B ; 11A, D ). Dorsal lobe absent on segment 2 ( Figs 10A ; 11C, E ).

Comb-like branchiae on segments 3 – 4, consisting of series of dense, flat lamellae ( Figs 10A – B ; 11B – E ). Branchiae of similar size but those on segment 3 inserted more ventrally than those on segment 4. Pair of small dorso-lateral glandular pads present adjacent to branchiae on segment 3 ( Figs 10A ; 11B – C, E ).

Ventral glandular lobes present on segments 3 – 6, becoming progressively more lateral and broader from segments 3 – 5 ( Figs 10B ; 11C – D ). Hump present near branchiae on segment 4. Segment 3 with ventral lobe, curved anteriorly. Segment 4 with pair of ventro-lateral lobes and mid-ventral lobe almost 1/3 width of ventro-lateral lobes, separated from those by deep grooves. Segment 5 with pair of ventro-lateral lobes and mid-ventral lobe about 1/3 width of ventro-lateral lobes, separated from those by shallow grooves. Segment 6 with pair of broad ventral lobes, separated from each other by median shallow groove ( Figs 10B ; 11D ).

Notopodia other than those of segment 1 which bear paleae, on segments 5 – 21 (17 pairs), each bearing two kinds of notochaetae; one winged from anterior row, bordered with serrations along distal portion, covered progressively with more spines from middle to front of wing, on anterior surface; other from posterior row, stout, straight, tapering to an acute tip, covered progressively with more spines from mid-anterior portion to tip, on anterior surface ( Figs 10D ; 11A – B ; 12A, C ). Neuropodia, 13 pairs on segments 8 – 20, each with slightly raised torus with transverse row of uncini; each uncinus with U-shaped anterior peg embedded into torus, several rows of minor teeth, and three longitudinal rows of major teeth, each with 7 – 8 teeth ( Figs 10E – F ; 12B ). Segment 21 with pair of ventro-lateral lobes near notopodia ( Figs 10C ; 11 F ).

Scaphe rectangular with rounded posterior margin, flattened dorsally, divided into two anterior narrow lobes and four posterior broader rounded lobes on each lateral margin; posterior margin with contiguous rounded lappets near anal flap; each with one dorsal cirri under margins of lateral lobes 2 – 5, posterior cirri longer than anterior ones ( Figs 10C ; 11F – H ). Anal flap oblong tongue, with short dorsal cirrus ( Figs 10A ; 11H – I ). Scaphal hooks 11 pairs, amber, almost straight, with blunt tip, arranged in transverse row on dorsal margin of scaphe ( Figs 10G ; 12D ).

Tube not collected.

Methyl Green stained body distinctly green on cirri of cephalic veil, ventral lobes of segments 2–6, base of 2 nd pair of tentacular cirri, dorso-lateral pads of segment 3, neuropodia, regions between segment 21 and scaphe, margins of scaphe, and the last half of scaphal ventrum ( Fig. 11 A–G).

Type locality. Australia, N Queensland ( Fig. 1 ) .

Habitat. Collected intertidally on sandy beach.

Etymology. The species is named from a latin word “cercus” referring to posterior appendages, as the species has four pairs of dorsal cirri on lateral margins of scaphe.

Remarks. Paleae and cephalic veil of the specimen are damaged, presumably during collection and also segments 11 – 14 are slightly damaged. But Amphictene cercusa n. sp. can be easily distinguished from all other Amphictene species by having four pairs of dorsal cirri under the lateral lobes of the scaphe (Table 1). Other distinguishing characters are: rectangular scaphe; posterior part margin of scaphe with contiguous rounded lappets near anal flap; 11 pairs of straight scaphal hooks; dorso-lateral pads present only on segment 3 and uncini with three longitudinal rows of major teeth. The scaphal hooks of A. cercusa n. sp., are similar to those of A. alata Zhang, Zhang & Qiu, 2015 and A. japonica ( Nilsson, 1928) , but both of these two species lack scaphal dorsal cirri and have dorso-lateral pads on segments 3 – 4. The scaphal hooks resemble those of A. favona Hutchings & Peart, 2002 , but this species has a dorsal lobe on segment 2 and dorso-lateral pads on segments 3 – 4, and lacks dorsal cirri on the lateral lobes of the scaphe, and so can be easily distinguished from A. cercusa n. sp.

Figures

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

FIGURE 10. Amphictene cercusa n. sp. Holotype (AM W.18121): A. Dorsal view of anterior end; B. Ventro-lateral view of anterior end; C. Dorso-lateral view of posterior end; D. Notochaeta; E–F. Uncini; G. Tips of scaphal hooks. Abbreviations: ac, anal cirrus; af, anal flap; br, branchiae; bt, buccal tentacles; cv, cephalic veil; dcs, dorsal cirri of scaphe; dlp, dorso-lateral pad; lms, lateral margin of scaphe; nec, neurochaetae; noc, notochaetae; op, operculum; or, opercular rim; p, paleae; s, segment; sc, scaphe; sh, scaphal hooks; tc, tentacular cirri; vl, ventral lappet.

FIGURE 11. Amphictene cercusa n. sp. Methyl Green stained body of Holotype (AM W.18121): A. Ventral view of entire body; B. Lateral view of entire body; C. Lateral view of anterior end; D. Ventral view of anterior end; E. Dorsal view of anterior end; F. Lateral view of posterior end; G. Dorsal views of posterior end. Scaphe of Holotype (AM W.18121): H. Dorsal views of posterior end; I. Lateral view of anal flap. Abbreviations: ac, anal cirrus; af, anal flap; br, branchiae; bt, buccal tentacles; cv, cephalic veil; dcs, dorsal cirrus of scaphe; dlp, dorso-lateral pad; op, operculum; or, opercular rim; p, paleae; s, segment; sc, scaphe; sh, scaphal hooks; tc, tentacular cirri; vl, ventral lappet.

FIGURE 12. Amphictene cercusa n. sp. chaetae of Holotype (AM W.18121): A, C. Close up of notochaetae, segment 11. B. Uncini, segment 11. D. Scaphal hooks.