Laonice pectinata, Greaves, Elizabeth & Wilson, Robin, 2011

Greaves, Elizabeth & Wilson, Robin, 2011, New Laonice species (Polychaeta: Spionidae) from western and northern Australia, Zootaxa 2903, pp. 1-20 : 10-12

Laonice pectinata sp. nov.

Figures 8–9

Material examined. Holotype: Australia: Indian Ocean, west of Perth, Stn SS 082005 25BS02, 32º51.267ʹ S, 114º15.417ʹ E, 14 Oct 2005, 1440 m, MV F 150655. Paratypes: Indian Ocean, west of Perth, Stn SS 082005 25BS02, 32º51.267ʹ S, 114º15.417ʹ E, 14 Oct 2005, 1440 m, 1 specimen, MV F 110722; Indian Ocean, west of Perth, Stn SS 082005 25BS02, 32º51.267ʹ S, 114º15.417ʹ E, 14 Oct 2005, 1440 m, 3 specimens, MV F 110724; Indian Ocean, Ningaloo North region, T2 100, Stn SS 07/2005 17, 21º58.75ʹ S, 113º50.583ʹ E, 23 Jan 2005, 99 m, 1 specimen, MV F167424.

Description. All anterior fragments, longest 27 chaetigers; in relatively poor condition, 3.5–5.5 mm long, 0.5– 1 mm wide.

Peristomium separate from prostomium, narrow, approximately half length of prostomium. Prostomium blunt, somewhat rounded, entire, extending posteriorly to chaetiger 1, terminating with occipital antenna, not fused to dorsum for posterior third of length; dorsal ridge extending posteriorly at least 12 chaetigers, uncertain due to specimen condition. Short occipital antenna present. Eyes present or absent; two pairs of eyes visible on one specimen (MV F167424); absent from remaining specimens. Palps lost from all specimens.

Dorsal branchiae from chaetiger 2 to end of fragments; free and separate from notopodial lamellae throughout; slender, up to twice length of notopodial postchaetal lamellae, appear to fall off more easily than in some other species.

First notopodial postchaetal lobe small, increasing in size until about chaetiger 4, leaf-shaped, somewhat pointed dorsally, becoming larger and more rounded, ultimately becoming kidney-shaped. Neuropodial postchaetal lamellae small rounded lobes throughout. Dorsal crests absent. Interparapodial pouches present, beginning chaetiger 3, until at least chaetiger 13 (after which they are difficult to recognise due to preservation).

Notopodial capillary chaetae in three rows, becoming more dense until about chaetiger 10, then reducing in number until end of fragment. Anterior neuropodial capillaries in three rows, stout; reduced to two rows, more slender and confined to upper part of neuropodium posteriorly. Neuropodial hooded hooks begin from chaetiger 21–27, up to 20 per fascicle, with many accessory teeth and no discernable main fang ( Fig. 9 A–B). Neuropodial sabre chaetae present, in ventral-most position, beginning chaetiger 9–14, two per fascicle, occasionally only a single sabre chaeta present.

Pygidium unknown.

Colour. White (unpigmented) in ethanol.

Distribution. Western Australia, 99–1440 m ( Figs. 1-2 ).

Remarks. This species is easily distinguished from other Australian species by the presence of up to 20 neuropodial hooded hooks per fascicle, each with numerous teeth. Hood removal by ultrasound was unsuccessful and due to limited hooks on the few available fragments, further attempts were not undertaken and hence SEM studies could not be conducted. Unfortunately this means that the exact number of teeth remains unknown, but the shape is clearly distinguishable under a light microscope. It is most similar to Laonice blakei Sikorski, Jirkov & Tsetlin, 1988 , which is known only from the Arctic; that species also has interparapodial pouches regularly starting from chaetiger 3 and three rows of chaetae on anterior chaetigers. However, hooks in L. blakei possess a distinct main fang. The species is also described as having a large occipital antenna and a caruncle to chaetiger 10–14, whereas L. pectinata sp. nov. lacks a distinct caruncle but has a dorsal ridge to about chaetiger 12.

The sole specimen in which two pairs of eyes visible (MV F167424), was collected at 99 m; the remaining specimens were from 1440 m and we cannot find any other morphological differences other than the absence of eyes in the specimens from the deeper locality. We thus treat the material as conspecific.

Laonice pectinata sp. nov. can also be characterised by having pouches consistently starting from chaetiger 3 (this feature does not appear to differ with size; however, there are only four specimens), pouches that end relatively early (about chaetiger 9–13), three rows of anterior notochaetae and often two sabre chaetae per fascicle.

Etymology: Latin for ‘comblike, toothed’, pectinata refers to the appearance of the neuropodial hooded hooks.

Figures

FIGURE 1. Locations in Australia where Laonice specimens were collected. Cross: L. insolita. White circle: L. cf. quadridentata. Grey circle: L. quadridentata. White square: L. lemniscata. Grey square: L. pectinata. Black square: L. hermaphroditica (data from unpublished Museum Victoria data). Grey diamond: Laonice cf. weddellia. Black diamond: L. bassensis (data from Blake & Kudenov 1978).

FIGURE 2. Bathymetric distribution of Australian Laonice species. L. hermaphroditica data based on the depth of Morton Bay, L. bassensis data from Blake & Kudenov 1978, L. weddellia data from OBIS (http: // www. obis. org. au /)

FIGURE 8. Laonice pectinata sp. nov. (MV F 150655 except where noted). A. Anterior end, dorsal view; branchiae lacking on chaetigers 2 (right side only) and 3, 4, 6 (left side only) (MV F 110724). B. Parapodium 5 (right). C. Parapodium 23 (right, notopodial lobe lost during dissection). Scales: A 0.5 mm; B – C 0.05 mm.

FIGURE 9. Laonice pectinata sp. nov. (MV F 150655). A, B. Neuropodial hooded hooks, chaetiger 23. Scales: A – B 0.01 mm.