Orbinia papillosa ( Ehlers, 1907 )

Zhadan, Anna, 2020, Review of Orbiniidae (Annelida, Sedentaria) from Australia, Zootaxa 4860 (4), pp. 451-502 : 485-487

Orbinia papillosa ( Ehlers, 1907)

Figures 19 , 20

Aricia papillosa Ehlers, 1907: 16 , figs.7–14.

Orbinia papillosa: Day 1977: 233 .

Material examined. New Zealand: South Island , Christchurch , Heathcote Estuary, Banks Peninsula, 43°32’S, 172°42’E, 22.10.1961, coll. I. Estcourt, AM W.7459, 1 complete specimen .

Type locality. Waiheke , Auckland, New Zealand .

Description. Thoracic width 2 mm. Body long, thorax slightly flattened, abdomen cylindrical, thoracic chaetigers numbering 27 ( Fig. 19A ). Prostomium conical, short and wide, with sharply pointed tip ( Fig. 19C, D ). Branchiae from chaetiger 5, triangular with filiform tips; in abdomen becoming long, strap-like with tapering tips, longer than notopodia ( Figs 19C, D, G , 20 A–C). Thoracic notopodial postchaetal lobes developed from first chaetiger, digitate, in abdomen becoming wider and lanceolate ( Figs 19C, D, G , 20 A–C). Thoracic neuropodial postchaetal lobes as ridges with papillae: chaetigers 1–4 with one papilla, chaetigers 5–6 with 2 papillae, then their number increasing up to 10–12 podal papillae ( Figs 19D, E , 20A ). Subpodal papillae from chaetiger 20 to 33; on chaetigers 22–29 extending ventrally to near mid-ventral line ( Fig. 19A, E, F ). Maximum number of foot and subpodal papillae combined per segment about 35. Abdominal neuropodia bilobed with outer lobe longer than inner lobe; subpodal flange well developed, with cirriform flange papillae (ventral cirrus) and scalloped margin ( Figs 19B, G, H , 20B, C ). Interramal cirrus short, knob-like, not always well marked ( Figs 19G, H , 20B, C ). Pygidium with two long thin anal cirri ( Fig. 19B ). Notopodial chaetae crenulate capillaries, in abdominal notopodia also forked chaetae present ( Fig. 20B ). Thoracic neuropodia bearing 3–4 rows of curved to almost straight smooth uncini and few thin capillaries in upper part of posterior row ( Figs 19D , 20A ). Abdominal neuropodia with capillary and flail chaetae ( Fig. 20B ). Both rami supported by thin aciculae in abdomen ( Fig. 20B, C ).

Distribution. Australia, Victoria, New Zealand.

Habitat. Intertidal, sand, seagrass.

Remarks. Orbinia papillosa was described from New Zealand ( Ehlers 1907) and later recorded from Victoria by Day (1977). The specimen studied here is in agreement with the original description. The short knob-like interramal cirrus is reported for the first time for this species.

Figures

FIGURE 19. Orbinia papillosa, AM W.7459, stereomicroscope, methylene blue staining; A. General view; B. Posterior end with pygidium; C. Anterior end, dorsal view; D. Anterior end, lateral view; E. Thorax-abdomen transition, lateral view; F. Thorax-abdomen transition, ventral view; G. Abdomen, dorsal view; H. Abdomen, lateral view.

FIGURE 20. Orbinia papillosa, AM W.7459, compound microscope.A. Parapodium of chaetiger 16; B. Parapodium of chaetiger 32; C. Posterior abdominal parapodium. a, acicula; br, branchia; cc, crenulated capillaries; ic, interramal cirrus; fc, forked chaeta; flc, flail chaeta; ne, neuropodium; no, notopodium; u, uncini.