Laonice quadridentata Blake & Kudenov 1978

Laonice cf. quadridentata Blake & Kudenov, 1978

Figures 12–13

Material examined. Australia: Gulf of Carpentaria: 15°58.9056ʹ S, 139°44.0076ʹ E, 0 2 Mar 2005, 39.8 m, 1 specimen, QM G228999; 15°59.5044ʹ S, 139°33.4908ʹ E, 2 Mar 2005, 42.2 m, 1 specimen, QM G229007; 16°54.0ʹ S, 139°45.504ʹ E, 3 Mar 2005, 39.8 m, 1 specimen, QM G229008; 15°54.5952ʹ S, 139°25.5648ʹ E, 3 Mar 2005, 42.2 m, 1 specimen, QM G229010; 15°48.5046ʹ S, 139°45.5112ʹ E, 4 Mar 2005, 43.6 m, 1 specimen, QM G229014; 15°57.4908ʹ S, 139°36.5082ʹ E, 5 Mar 2005, 41.8 m, 1 specimen, QM G229021; 15°36.3282ʹ S, 137°56.607ʹ E, 7 Mar 2005, 46.0 m, 1 specimen, QM G229031; 13°20.67ʹ S, 136°50.6556ʹ E, 11 Mar 2005, 39.2 m, 3 specimens, QM G229052; 13°12.4962ʹ S, 136°50.4672ʹ E, 12 Mar 2005, 40 m, 2 specimens, QM G229056; 15°46.5420ʹ S, 138°14.5296ʹ E, 19 Mar 2005, 43 m, 1 specimen, QM G229099.

Additional material examined. Laonice quadridentata Blake & Kudenov, 1978. Australia: Victoria: Port Phillip Bay, Geelong Arm, 38°04.7´S, 144°36.1´E, 11 Feb 1970, 10 m, sand/clay/silt, 1 paratype, MV F42977; Central Port Phillip Bay, 38°09.3´S, 144°56.7´E, 21 Sep 1970, 22 m, clay, 3 paratypes, MV F42953. Laonice petersenae Radashevsky & Lana, 2009. SW Atlantic Ocean, Brazil, Paraná, Paranaguá Bay: mouth of Maciel River, 25°33.5´S, 48°25.5´W, 17 Jul 2002, 15 m, 8 paratypes, SMF 13960.

Description (based on Gulf of Carpentaria specimens of Laonice cf. quadridentata). All anterior fragments, with 39 chaetigers maximum, specimens 0.4–1.6 mm wide.

Prostomium anteriorly rounded, entire, fused to peristomium at anterior margin; laterally separated from peristomium by two grooves; posteriorly with caruncle merging into middorsal ridge, extending well into mid-body region, usually until end of fragment. Distinct finger-like occipital antenna present; arising at posterior part of prostomium behind eyes. Eyes one pair of two large reddish to dark brown patches across middle of prostomium; sometimes almost touching. Peristomium dorsoanteriorly fused with prostomium, well developed, forming moderate lateral bulges. Palps lost in all specimens. Nuchal organs as double ciliary bands running along each side of caruncle and middorsal ridge; maybe U-shaped but shape and posterior extension of ciliary bands not unambiguously discernible due to moderate to poor condition of material; in one specimen ciliary bands seem to reach chaetiger 15, in others visible to chaetiger 4, 7 or 10 (Fig. 12A).

Branchiae present from chaetiger 2, usually continuing along entire fragment; first branchiae small, cirriform or minute, stump-like (particularly in specimens with body widths <1 mm), thereafter quickly increasing in length; from chaetiger 4 cirriform branchiae same length as notopodial postchaetal lamellae, longest branchiae present in mid-body region, about twice as long as notopodial postchaetal lamellae, in larger specimens at least 2.5-times length of postchaetal lamella; branchiae completely free from notopodial postchaetal lamellae.

Chaetiger 1 not reduced, with well-developed parapodia; postchaetal lamellae rounded in both rami. From chaetiger 2 notopodial postchaetal lamellae leaf-like, initially tapered, from about chaetiger 4–6 rather elongate with rounded tip; neuropodial lamellae of chaetigers 2–4 subtriangular, becoming more rounded but usually with indistinct tip in subsequent chaetigers; in chaetigers of the mid-body region neuropodial lamellae elongate, often reaching ventral side of body (Fig. 12B–E). Distinct but low prechaetal lamella present in neuro- and notopodia. Dorsal crests absent. Interparapodial pouches from chaetiger 6, 8 or 13; continuing until end of fragment.

Chaetae in two rows in noto- and neuropodia of anterior and middle chaetigers; anterior row shorter and stouter than posterior row, granulated near tip; chaetae in posterior row long thin simple capillaries; in neuropodia of anterior body (first 10–15 chaetigers) number of chaetae in posterior row usually higher than in anterior row. Neuropodial hooded hooks present in few specimens only (Gulf of Carpentaria specimens are all anterior fragments only); usually starting as single hook in inferior position, hooks starting from chaetigers 26–33; two teeth above the main fang (Fig. 13B, see Remarks). Thin capillaries in addition to hooks present in superior position, 1– 5 in number, exceeding hooks in length. Start of sabre chaetae difficult to determine (see Methods: Description of characters and procedures); in smaller specimens supposedly from about chaetiger 16, later in larger specimens.

Pygidium unknown.

Colour. White in ethanol, usually with faint greyish or brownish pigment on parapodial postchaetal lamellae from about chaetiger 10–25; before chaetiger 10 and after chaetiger 25 very faint pigment only in notopodial lamellae.

Distribution. Australia, Gulf of Carpentaria, 39–43 m (Figs. 1-2).

FIGURE 12. Laonice cf. quadridentata Blake & Kudenov, 1978. A Anterior end from dorsal; back of specimen damaged after chaetiger 4 (QM G229031). B. Parapodium 5 (left) (QM G229014). C. Parapodium 16 (right) (QM G229031). D. Parapodium 35 (right) (QM G229014). E. 22nd parapodium (left) (QM G229031). Scales: A 0.5 mm; B–D 0.1 mm; E 0.2 mm.

Remarks. Laonice from the Gulf of Carpentaria were identified as L. cf. quadridentata based on the fusion between prostomium and peristomium, the beginning of interparapodial pouches after chaetiger 6, and the late start of neuropodial hooded hooks, not before chaetiger 26. Laonice quadridentata was described by Blake & Kudenov (1978), from Port Phillip Bay, Victoria, Australia. The most striking feature of L. quadridentata is the fusion of prostomium and peristomium. However, from the literature it is known that species morphologically similar to L.

quadridentata show great ontogenetic and individual variability (Sikorski 2002, 2003a, Radashevsky & Lana 2009, see Discussion). Such variability was not reported by Blake & Kudenov (1978) in the original description of L. quadridentata. This lack of variation is in good agreement with the results of our examination of four paratypes of L. quadridentata, with the exception that our SEM studies of the two paratypes possessing hooks revealed that the number of apical teeth in the neuropodial hooded hooks varied between 3–4 within a single individual (Fig. 13 C, D). Although our specimens of Laonice cf. quadridentata from the Gulf of Carpentaria were comprised of short anterior fragments, many in poor condition and only a few with hooks, our specimens exhibited considerable variability in regard to the extension of the nuchal organ, the beginning of interneuropodial pouches, and the start of hooded hooks in the neuropodia (see description above). Also, the start of sabre chaetae appeared to vary, though it was difficult to determine the exact position where sabre chaetae were first present (see Methods). Due to the limitations of available material, it is impossible to provide data on these characters in relation to the total number of chaetigers or to last branchiate chaetigers as did Sikorski (2002, 2003a) and Radashevsky & Lana (2009). Based on the available material and knowledge of the importance of size-related variability in understanding species boundaries in Laonice, we have to refrain from a formal assignment to one of the currently valid species and the material from the Gulf of Carpentaria is referred to here as Laonice cf. quadridentata.