Owenia picta, Parapar, Julio & Moreira, Juan, 2015

Parapar, Julio & Moreira, Juan, 2015, The Oweniidae (Annelida; Polychaeta) from Lizard Island (Great Barrier Reef, Australia) with the description of two new species of Owenia Delle Chiaje, 1844, Zootaxa 4019 (1), pp. 604-620 : 613-616

Owenia picta n. sp.

( Figs 1 D, 2, 7–11)

Material examined. Holotype: AM W.45875, stn. 2.4.2., coarse to medium sand, 4.5 m. Paratypes: AM W.36972, MI QLD 2198, sand, 9 m, fixed in EtOH; AM W.36973, MI QLD 2205, coral rubble, 14.5 m, fixed in EtOH; AM W.36974, MI QLD 2148, sediment, 9 m, in 95% EtOH; AM W.41320, MI QLD 2205, coral rubble, 14.5 m, fixed in EtOH; AM W. 41321, MI QLD 2198 (6 fixed in EtOH), sand, 9 m; AM W.45219, MI QLD 2440, fixed in EtOH; AM W.45403, MI QLD 2441 (2 fixed in EtOH); AM W.45856 (4), medium sand, 3 m; AM.45864, coarse to medium sand, 4.5 m; AM W.45865, medium to fine sand, 18 m; AM W.45868, coarse to medium sand, 4.5 m; AM W.45873, coarse to medium sand, 4.5 m; AM W.45876 (3), filamentous algae, 12 m; AM W.45862, filamentous algae, 12 m; AM W.45917, filamentous algae, 12 m; AM W.47388 (5), sand, 6.5 m; AM W.47385 (3), 2 m; AM W.47390, filamentous algae, 12 m, on SEM stub; AM W.47391, medium sand, 3 m, on SEM stub; AM W.47392, sand, 6.5 m, on SEM stub.

Description. Based on holotype. Body elongated; 26 mm long, 0.5 mm wide, with 22 chaetigers. Branchial crown with four pairs of tentacles ( Figs 8 A, 9A–C). Each tentacle with no major divisions; tips of tentacles with multiple small lobes provided with a distal sulcus ( Fig. 10 A–B) separating inner ciliated side from outer nonciliated side. Crown almost as long as thorax (C/T ratio ≈ 0.85). Pair of pale eye spots at ventral base of crown ( Fig. 8 B). Junction between thorax and tentacle crown marked by a distinct, straight collar closely aligned with body wall, slightly overlapping base of crown. Thorax and crown of similar width. Thorax with three pairs of poorly developed notopodia with capillary chaetae. Collar sometimes expanded in a large dorsal lobe ( Fig. 9 B–D); a short bilobed ventral projection present in all specimens ( Figs 8 B, 9A, 10C–D). RLTS: 1−2.5−0.5. A deep groove at base of first thoracic uniramous chaetiger (u1) present in all specimens ( Figs 8 A–C, 9B–D). Notochaetae with shafts composed of densely packed scales ( Fig. 11 A). Thoracic neuropodia absent. Abdomen of uniform width, with about 16 chaetigerous segments with noto- and neuropodia; width of abdominal segments decreasing posteriorly, being posterior segments short and compact. First abdominal chaetiger (b1) about as long as all thoracic segments (u1–u3) together. Second abdominal chaetiger (b2) about 1.5 times b1; b3 = b4 and both about ¾ of b2; following segments progressively shorter. Abdominal notopodia poorly developed with capillary chaetae similar to thoracic notochaetae. Abdominal notochaetae arranged dorsally. Neuropodia consisting of wide sessile podia with several rows of neurochaetal hooks ( Fig. 11 B); tori almost encircling body except on dorsal surface between notochaetal bundles. Neurochaetal uncini similar through, consisting of hooks with shaft ending in two teeth side by side ( Fig. 11 C–D). Pygidium multilobed ( Figs 8 D, 11F).

Preserved animals creamy white with distinctive pigment marks consisting of diffuse brown speckles covering most of ventral part of peristomium and anterior part of first thoracic chaetiger (u1) ( Fig. 8 B). Tube coated by quartz grains and shell fragments.

Variations. One paratype of sample W.45403 is complete measuring 6 mm in length, 0.3 mm in width with 15 abdominal chaetigers. In one specimen of W.41321, RLTS is 1–3–0.5. Some paratypes show pigmentation more extended than in the holotype. For instance, in W.45219 coloration is also present dorsally in the peristomium and u1, but less marked than in the dorsal area. In paratype W. 36972 there is also coloration in the base of the branchial crown. One paratype of W.45856 shows the anterior end in process of regeneration; in the other the total length of the branchial crown is similar to that of thorax (C/T ratio ≈ 1.0).

Remarks. Owenia picta n. sp. mostly resembles O. australis from SE Australia ( Fig. 7 D); both differ from any other Owenia in the region by the following features: 1) the larger size of the branchial crown when compared to the thorax (C/T ratio ≈ 0.85), 2) four pairs of branchial lobes, and 3) by lacking conspicuous major ramifications in the crown. However, O. picta n. sp. differs from O. australis in having conspicuous coloration in the anterior end and a deep dorsolateral groove behind notochaetal bundle of u1, which has not been reported in O. australis .

Specimens from Indonesia identified by Caullery (1944) as O. fusiformis ( Fig. 7 A) show likewise a large branchial crown but of a lesser C/T ratio. According to the description and illustrations by Caullery (1944), its length is about half of the thorax length, about 5/8 of the distance from the base to the first uncinigerous torus (C/T ratio ≈ 0.63; Caullery 1944). Furthermore, O. picta n. sp. and O. fusiformis sensu Caullery differ from each other in the pattern of branchial coloration; in O. fusiformis sensu Caullery , there are whitish spots in the tips of the branchial ramifications (see Fig. 41A–C in Caullery 1944) and dorsal white spots sometimes (not explicitly mentioned or illustrated in the description). Caullery (1944) also states that the lateral sides of thorax are uniformly reddish brown. On the contrary, in O. picta n. sp. the branchial and thoracic coloration is reddish and the pattern of pigmentation in the branchial crown is different.

Other oweniid species show a smaller C/T ratio (0.6) than that of O. picta n. sp., namely O. bassensis ( Australia) , O. mirrawa ( Australia) , O. petersenae ( New Zealand) and O. gomsoni ( South Korea) ( Fig. 7 ). Furthermore, O. bassensis has three branchial lobes instead of four as it happens in O. picta n. sp., O. mirrawa has conspicuous major divisions in the branchial crown close to its base, O. petersenae has major divisions in the branchial crown only at the distal end, and O. gomsoni has white dorsolateral bands of coloration in u1 and u2.

The Pacific species Owenia johnsoni Blake, 2000 , from the Gulf de California, has also a high C/T ratio ≈ 0.75. However, this species is colourless and the branchial crown has only one major ramification and each lobe end is divided in several (4–5) fine slender bifid tips of same length (see Fig. 5.10. in Blake 2000).

Etymology. The species name (“ picta ”) refers to the conspicuous brown pigmentation present in the anterior part of the body.

Habitat / Distribution. Species apparently restricted to NW of Lizard Island, Watson’s Bay to North Point from 3 to 15 m depth, on sandy bottoms ( Fig. 1 D). Three specimens were found at 5 m depth at Eagle Island, about 4 nautical miles SW from LIRS.

Figures

FIGURE 1. Map of the study area showing collecting sites of Galathowenia and Owenia species described or reported in this work. In (B − D) arrows facing to cross-shelf sampling sites: EI = Eagle Island; NDI = North Direction Island. Dots refer to material collected during LI Workshop held in August 2013; stars refer to AM material; white star refers to type locality of O. picta n. sp.

FIGURE 7. Anterior end in ventral view, of species of Owenia described or reported in the South East Asia and Australia, all redrawn from original; between brackets the collecting locality (A and B) or type locality (C – F). Organized alphabetically and by date. A. O. fusiformis (in Caullery 1944); B. O. fusiformis (in Imajima & Morita 1987); C. O. gomsoni (redrawn from a SEM micrograph in Koh & Bhaud 2001); D. O. australis (in Ford & Hutchings 2005); E. O. bassensis (in Ford & Hutchings 2005); F. O. mirrawa (in Ford & Hutchings 2005). O. petersenae Koh & Bhaud, 2003 was not included because it could not be redrawn from original pictures.

FIGURE 8. Owenia picta n. sp. (holotype AM W. 45875). A. Anterior end, dorsal view; B. Anterior end, ventral view; C. Anterior end, left lateral view; D. Posterior end, ventral view.

FIGURE 9. Owenia picta n. sp. SEM micrographs (AM W. 47392, W. 45876 and W. 45856). A. Anterior end, ventral view; B – C. Anterior end, dorsal view; D. Detail of u 1 and u 2 of (C).

FIGURE 10. Owenia picta n. sp. SEM micrographs (AM W. 47392, W. 45876 and W. 45856). A. Branchial crown, ventral view; B. Distal end of a lobe (framed on A), showing distal groove; C. Crown base, ventral view; D. Detail of bilobed structure (framed on C) between first pair of branchial lobes.

FIGURE 11. Owenia picta n. sp. SEM micrographs (AM W. 47392, W. 45876 and W. 45856). A. Scale covering of thoracic notopodial capillary chaetae; B. First abdominal chaetiger (b 1), ventral view; C – E. Abdominal neuropodial hooks, in top, lateral and oblique view; F. Posterior end, ventro-lateral view.