Pista labruneae Lavesque & Daffe & Londoño-Mesa & Hutchings 2021, n. sp.

Pista labruneae n. sp.

Figure 18

Material examined. Holotype. MNHN-IA-TYPE 2031, posteriorly incomplete, Mediterranean Sea, Gulf of Lion, Redit F 20, 42°46’44”N 3°3’21”E, depth 20 m, August 2010. Paratypes. AM W.53329, posteriorly incomplete, Mediterranean Sea, Gulf of Lion, Redit F 20, 42°29’20”N 3°8’19”E, depth 17 m, October 2020. MNHN-IA-TYPE 2032, posteriorly incomplete, Mediterranean Sea, Gulf of Lion, Beauduc, 43°24’47”N 4°30’7”E, depth 14 m, 2012.

Description. Holotype posteriorly incomplete, 22.3 mm long (5.8 mm) and 1.5 mm wide (0.5 mm), for 29 segments.

Transverse prostomium attached to dorsal surface of upper lip; basal part without eyespots; distal part of prostomium convoluted. Buccal tentacles filiform and deeply grooved (Fig. 18B–F). Peristomium forming lips, upper lip hood-like, large, wider than long, rectangular, with convoluted margin, slightly pointed anteriorly; lower lip swollen, crescent-shaped, wider than long (Fig. 18B–C).

Segment I conspicuous, with one pair of rounded lateral lobes, connected to each other by a thin and smooth membrane with rounded ventral indentation, surrounding lower lip (Fig. 18B–C, E). Segment II with one pair of large ventro-lateral lobes, trapezoidal, with long ventral base and rounded margins, connected to each other by large mid-ventral crenulated crest. Segment III with one pair of auricular dorso-lateral lobes, much shorter than those of SG II, connected to each other by thin, slightly crenulated mid-ventral crest. Segment IV without lateral lobes.

Dorsal anterior margins of SG III as protruding crest (Fig. 18D). A single plume-shaped branchia present on SG II inserted mid-dorsally; with conspicuous, annulated basal stem, branches arranged in spiral around the main stem, with short filaments (Fig. 18A, C–E). Smooth mid-ventral shields present on SG V–XIX, rectangular shields, becoming progressively longer and wider posteriorly.

Notopodia beginning on SG IV, extending until SG XX; notopodia short, rectangular, first four pairs shorter, inserted progressively more laterally, then longitudinally aligned (Fig. 18C–D). Broadly-winged notochaetae in two rows, broader on one side (Fig. 18G), with first row shorter.

Neuropodia present from SG V, as low, almost sessile ridges until end of notopodia, as low rectangular pinnules thereafter (Fig. 18 C–D). Neurochaetae as long-handled uncini on SG V–X, with well-developed handles originating from heel, progressively thinner; uncini arranged in partially intercalated double rows on SG XI–XX in a faceto-face arrangement. Avicular uncini with slightly convex base, large rounded heel, distally rounded prow, dorsal button inserted halfway between base of main fang and prow, and well-developed pointed main fang, surmounted by crest with 5 rows of numerous and progressively shorter secondary teeth above the main fang (Fig. 18H–I).

Genital papillae on SG VI–VII, tubular, situated dorsally behind notopodia. Pygidium unknown.

Etymology. This species is dedicated to Céline Labrune, from the Banyuls-sur-Mer Arago Laboratory, for her friendship with NL for about 15 years and for providing the type material of eight new species since the beginning of the “ Spaghetti Project ”, including this new one.

Habitat. Fine sand, depth 17–20 m.

Type locality. Gulf of Lion, Western Mediterranean Sea, Gulf of Lion. 42°46’44”N 3°3’21”E.

Distribution. Only known from the type locality, but probably present in Italy and other parts of the Mediterranean Sea (see below).

Remarks. Among the European species, P. labruneae n. sp. is easily recognizable by the presence of a single branchia situated mid dorsally on SG II. The type material was carefully checked to ensure that only a single branchia was ever present, and that another one had been lost but no evidence of a branchial scar was ever found, so we are confident that only a single branchia was present. Moreover, specimens with only a single branchia are regularly found in this area (Labrune pers. com.) confirming that only a single branchia is present.

Pista labruneae n. sp. differs from P. colini recently described from the same area (Labrune et al. 2019). First, P. colini has one pair of branchiae instead of a single mid-dorsal branchia. The two species differ also by the number and shape of lateral lobes. The lateral lobes on SG II of P. labruneae n. sp. are larger than those of P. colini. Finally, P. colini has neurochaetae as long-handled avicular uncini on SG V–VI, short-handled thereafter while P. labruneae n. sp. has long-handled uncini at least until SG X.

Pista labruneae n. sp. has probably been previously confused and misidentified in the Mediterranean Sea as P. unibranchia Day, 1963, a species from South Africa also described as having a single branchia. However, as underlined recently by Langeneck et al. (2020), the presence of this last species as a non-indigenous species is doubtful. Moreover, P. unibranchia is characterised by the absence of long-handled uncini on SGV (Day 1963) and should be transferred to the genus Pistella Hartmann-Schröder, 1996. In addition to the different shape of uncini, Pista labruneae n. sp. differs from P. unibranchia by the absence of lateral lobes on SG IV.