Lepidasthenia brunnea sensu Knox, 1960

Lepidasthenia brunnea sensu Knox, 1960 View in CoL

Lepidametria brunnea Knox, 1960: 91–93 View in CoL , figs 58–63.

( Figures 4 View Figure 4 , 5 View Figure 5 )

Material examined

Solomon Sea, Papua New Guinea . One infected specimen ( MNHN IA 2015–1723 About MNHN ), MADEEP Expedition, Eastern New Britain, Induna Island , RV Alis, Sta . CP4266 ( 04°35 ʹ 07.1988” S, 152° 25 ʹ 03.5904” E), 575–616 m, 26 April 2014, L. Corbari et al., leg.

Description of host

Parasitised specimen ( MNHN IA 2015–1723) complete, pale, brownish along prostomium, ceratophores, and parapodial bases ( Figure 6 View Figure 6 (A)); very few dorsal cirri and elytra on site, first right elytron blackish, corrugated, longer than wide, two far posterior left elytra pale, corrugated. Venter pale. Body 14 mm long (excluding pharynx, 3 mm long), 3.5 mm wide, 48 chaetigers (chaetigers 15–28 with attached parasite copepods ( Figure 5 View Figure 5 (A,B)).

Prostomium oval, about 3 times wider than long ( Figure 4 View Figure 4 (B)). Eyes black, not marginal, anterior eyes 4–5 times larger than posterior ones. Median antenna with ceratophore twisted, about 3 times longer than prostomial length; lateral ceratostyles lost. Palps lost. Tentacular cirri lost, tentaculophores without chaetae. Pharynx with two pairs of jaws; marginal papillae partially eroded, 10 pairs ( Figure 4 View Figure 4 (D)).

Elytra almost completely lost. Elytrophores present in chaetigers 2, 4, 5, 7,... 21, 23, 26, 29, 32, 35, 38, 41, 44, 47. Last 2 left elytra corrugated, probably overlapping laterally, not covering dorsum. Each elytron longer than wide, surface smooth, margin smooth, with a small dark spot in insertion area, and a slightly darker margin area along anterior and external posterior margins ( Figure 4 View Figure 4 (C).

Parapodia sesquirramous. Dorsal cirri tapered, barely swollen subdistally ( Figure 4 View Figure 4 (E)). Notopodia reduced to notacicular lobe. Neuropodia with long prechaetal (acicular) lobe, and shorter postacicular lobe. Neurochaetae bidentate with series of petaloid denticles along pectinate area ( Figure 4F View Figure 4 ), becoming progressively smaller distally. Upper neurochaetae thinner, with a longer pectinate area, with about 40 series of denticles; median neurochaetae thicker with about 20 series of denticles; lower neurochaetae shorter with about 15 series of denticles. Ventral cirri tapered. Ventral neuropodial surface with 4 globose papillae (inset in Figure 4 View Figure 4 (E)). Nephridial lobes globular to truncate digitate, present along chaetigers 20–46, some basally swollen. Posterior region tapered; pygidium with anus terminal, right anal cirrus as long as last 4 chaetigers.

Remarks on host

The polynoid Lepidasthenia brunnea sensu Knox, 1960 , as we herein regard it, was described in Lepidametria Webster, 1879 , from a single specimen ( 45 mm long, 4 mm wide, 70 chaetigers) collected from sediments in the Chatham Islands, New Zealand, at 72 m water depth. It had elytra in simple sequence along 23 chaetigers; the following ones had 1 elytron every 3 chaetigers, and the parapodia have no notochaetae, such that it belongs in Lepidasthenia .

The Papuan–New Guinean host specimen resembles L. brunnea sensu Knox, 1960 by having ovoid, wider than long prostomium with eyes submarginal, first elytra blackish, parapodia with long prechaetal and postchaetal lobes, and by having papillae along ventral neuropodial surface. The main differences are that in L. brunnea the chaetae are uni- and bidentate, whereas they are all bidentate in our specimen, and that in the latter, the chaetal lobes are more elongate. A fine comparison requires the study of type material to clarify whether they are conspecific, but that is beyond our current objective.

If after the study of the type specimen of L. brunnea Knox, 1960 , it is shown that it belongs in Lepidasthenia , then it would be homonymous with L. brunnea Day, 1960 (published May 1960), and settling the publication dates would be needed to clarify which has priority. It is interesting that Lepidametria brunnea Knox, 1960 and Lepidasthenia brunnea Day, 1960 resemble each other and their main difference is that in the former, the neuropodium is shorter and longer in the latter.

Our host specimen also resembles L. brunnea Day, 1960 , originally described from two anterior fragments (longest 40 mm long, 48 chaetigers) dredged in False Bay, South Africa in sediments at 88 m water depth. The resemblance relies in the size of eyes and parapodial lobes, but these two species differ because in our specimen there are fewer papillae along the ventral neuropodial surface (4 vs 8), and all neurochaetae are bidentate (compared with uni- and bidentate).

Distribution

Papua New Guinea to New Zealand, in sediments at a depth range of 72– 616 m .