Armandia casuarina, Moreira, Juan & Parapar, Julio, 2017

Moreira, Juan & Parapar, Julio, 2017, New data on the Opheliidae (Annelida) from Lizard Island (Great Barrier Reef, Australia): five new species of the genus Armandia Filippi, 1861, Zootaxa 4290 (3), pp. 483-502 : 490-491

Armandia casuarina n. sp.

( Figs 1 , 5 )

Material examined: Two specimens in two samples. Holotype: AM W.49293, MI QLD 2433. Paratype: AM W.45932 (Patch Reef off Research Pt., LI, lagoon; shining torch in surface waters; 0 2 Dec 1985).

Diagnosis. Parapodia biramous, with prechaetal lobe, ventral lobe and small dorsal cirrus; prechaetal lobe asymmetrical; first two chaetigers with conspicuous elongated tip, directed postero-dorsally; subsequent chaetigers with shorter, rounded tip, ventrally displaced. Anal tube about 2.3 times longer than width at base, laterally compressed, as long as last five chaetigers; opening directed posteriorly, slightly oblique, lacking ventral incision. Posterior margin with about 6 pairs of digitiform marginal papillae of different sizes; one pair of large basal papillae, about 0.33 times length of tube, each provided with about 15 short, digitiform papillae; long unpaired anal cirrus, about 0.8 times length of anal tube.

Description. Based on holotype. Specimen complete, 7.4 mm long and 0.3 mm wide, with 39 chaetigers. Body slender, slightly tapering towards anterior end and truncated at posterior end ( Fig. 5 A). Prostomium conical; palpode well-developed, palpostyle bullet-shaped. Prostomium with one dorsal eye and two lateral small eyes. One pair of ring-shaped nuchal organs; oral tentacles not seen. Segmental limits among chaetigers not defined. Branchiae present from CH 2 to last chaetiger ( CH 39); branchiae long, surpassing parapodium of second following chaetiger, decreasing in length from CH 34, last two chaetigers with much short branchiae. Parapodia biramous, with prechaetal lobe and ventral lobe, small dorsal cirrus from CH 2 ( Fig. 5 D–I). Prechaetal lobe asymmetrical; CH 1–2 with conspicuous elongated tip, directed postero-dorsally, about 0.4 times length of prechaetal lobe; subsequent chaetigers with rounded tip, much shorter than prechaetal lobe, directed posteriorly and ventrally displaced. Ventral lobe rounded, increasing in size backwards. Lateral reddish eyespots anterior to parapodia on 11 chaetigers ( CH 7–17); those of CH 7 and CH 15–17 smaller than others. Ventral groove deep, well defined along all body ( Fig. 5 C). Simple capillary chaetae in two bundles, of about 7–9 each, 5–7 chaetae longer than other 2–3; notochaetae longer than neurochaetae, those of first three chaetigers longer than those of subsequent chaetigers. Anal tube about 2.3 times longer than width at base, rectangular, laterally compressed, as long as last five chaetigers ( Fig. 5 B, C); opening directed posteriorly, slightly oblique, lacking ventral incision. Posterior margin provided with at least 6 pairs of alternating short and elongate digitiform marginal papillae (some of any given pair lacking in right side); one of the dorsalmost papilla inflated and longer than others, about 0.25 times length of anal tube; one pair of basal papillae, cylindrical, narrower at base and distally pointed, about 0.33 times length of tube, each provided with about 15 small, digitiform papillae; long unpaired anal cirrus, about 0.8 times length of anal tube, thick at base and slightly tapered distally, inserted distally in anal tube.

Variation. The only paratype was collected in 1985 in an area close to the type locality, and is currently housed in the collections of the AM. This specimen is 5.25 mm long with 39 chaetigers; it is mostly similar to the holotype but its tegument is encrusted by some kind of crystals probably deposited during preservation. However, the parapodia are like those of the holotype and the anal tube still bears the pair of basal papillae with several distal secondary papillae.

Remarks. Armandia casuarina n. sp. is unique among the genus because of the combination of two characters, i.e. the shape of the prechaetal lobe of the first two chaetigers and the pair of basal papillae of anal tube that are provided in turn with small papillae. The only known species from the Indo-Pacific (see key below) with similar body appearance, parapodia features and presence of basal papillae is A. secundariopapillata from SW Australia. This species also presents a prechaetal lobe with elongated tip in several chaetigers of the anterior part of the body (at least up to CH8) and paired marginal papillae of different sizes, including at least one larger dorsal papilla similarly to the new species. Nevertheless, both species differ in the size and proportions of the anal tube; in A. secundariopapillata the anal tube is much wider at base than total length both in the holotype and paratypes (cfr.

Figs 46–47 in Hartmann-Schröder, 1984) while in A. casuarina n. sp. is at least twice as long as wide at base. Furthermore, in A. casuarina n. sp. the insertion of unpaired anal cirrus is at distal end instead of being clearly within the tube, the prechaetal lobe is not elongated in chaetigers following CH 1–2 and total number of chaetigers is 39 instead of 30 as it happens in A. secundariopapillata for specimens with a similar length range. Armandia parva n. sp. also described herein also presents similar paired basal papillae but differs from A. casuarina n. sp. in a number of features, e.g. the prostomium is short and truncated with anterior incision, and the prechaetal lobe of parapodia in CH 1–2 is much shorter and not conspicuously elongated.

Etymology. The name of the new species refers to Casuarina Beach that is the type locality of the species.

Habitat / Distribution. Holotype was collected in low tide sand in Casuarina Beach , in front of Lizard Island Research Station . Paratype belongs to a previous sampling campaign at LI; the label of the vial reads “Patch Reef off Research Pt., Lizard Is., lagoon” which corresponds to an area near Palfrey Island, in the Blue Lagoon, very close to the area where the holotype was found (P. Hutchings pers. comm.) ( Fig. 1 , Table 1). The paratype was collected in the water column near surface using a shining torch.

Figures

FIGURE 1. Map of the study area showing collecting sites of new species described herein. Arrow in Yonge Reef symbol facing to cross-shelf site.

FIGURE 5. Armandia casuarina n. sp. (holotype AM W. 49293). A, anterior end, left side, lateral view. (B – C) Posterior end and anal tube: B, lateral view; C, ventral view, anal tube resting on right side. (D – I) Parapodia, left side, lateral views: D, CH 1; E, CH 2; F, CH 3; G, CH 4; H, CH 6; I, CH 38. White arrows pointing prechaetal lobe tip; D – I, same scale.