Protoariciella cf. oligobranchia Hobson, 1976

Zhadan, Anna, 2020, Review of Orbiniidae (Annelida, Sedentaria) from Australia, Zootaxa 4860 (4), pp. 451-502 : 496

Protoariciella cf. oligobranchia Hobson, 1976

Figure 27

Protoariciella oligobranchia Hobson, 1976: 591–593 , fig. 1 a–g.

Material examined. Queensland: Lizard Island , fringing reef between Bird Islet and South Island, 14°40’S, 145°28’E; depth 12 m, 06.11.1976, coll. P.A. Hutchings, AM W.43255, 1 specimen on SEM stub; Lizard Island, off Chinamans Head , 14°40’S, 145°27’E, depth 7 m, 08.01.1977, coll. P.A. Hutchings & P.B. Weate, 1 specimen .

Type locality. Canada, British Columbia .

Description. Specimens entire, body length 7–8 mm, 58–67 chaetigers, width 0.25–0.3 mm ( Fig. 27A, J ). Prostomium short, round, without eyes; two peristomial segments ( Fig. 27B, D ). Transition from thorax to abdomen indistinct ( Fig. 27A, B, D, J ). Branchiae from chaetiger 5; triangular with pointed tips; longer than notopodia in anterior part, shorter or same length in middle; absent on posteriormost segments ( Fig. 27 B–D). Notopodial postchaetal lobes triangle-digitiform; neuropodial lobes oval with broad bases ( Fig. 27B, D, E, G, H ). Pygidium with four short cirri ( Fig. 27C ). Notochaetae crenulated capillaries in all segments, in abdominal notopodia also forked chaetae present ( Fig. 27G, I , K–M). Neurochaetae crenulated capillaries and few curved serrated uncini in thorax, crenulated capillaries and straight or slightly curved smooth or partially finely serrated hooks in abdomen; some hooks bidentate both in thorax and abdomen ( Fig. 27 E–H, K–M).

Remarks. Protoariciella oligobranchia was described from British Columbia ( Canada, East Pacific) ( Hobson, 1976). It differs from other species of the genus owing to the starting-point of the branchiae segment (chaetiger 4–5, not 6–8), absence of branchiae from many posterior segments, and chaetal characteristics (bidentate uncini and forked chaetae in each segment). The specimens studied here are similar, with branchiae starting on chaetiger 5 and the presence of bidentate uncini. But based only on the literature. However, they differ owing to having fewer forked chaetae, as there are only 1–2 present in the middle and posterior notopodia and are absent in the anterior notopodia. It was not possible to establish the number of posterior abranchiate segments because of the poor condition of the worms. The specimens studied here likely represent a new species; but due to the few poorly preserved specimens and the limited knowledge of the important taxonomic characters in this genus, it is not described as a new species.

Figures

FIGURE 27. Protoariciella cf. oligobranchia, AM W.43255. A–I, SEM, J–M: compound microscope. A. general dorsal view; B. Anterior end, dorsal view; C. Posterior end, dorsal view; D. Anterior end, lateral view; E. Neuropodium of chaetiger 7; F. Neurochaetae of chaetiger 7; H. Neurochaetae of abdominal chaetiger; I. Notochaetae of abdominal chaetiger; J. General view; K. Thoracic parapodia; L, M: Abdominal parapodium. cc, crenulated capillaries; fc, forked chaeta; h, hook.