Diopatra biscayensis, Fauchald, Kristian, Berke, Sarah Kosting & Woodin, Sarah Ann, 2012

Fauchald, Kristian, Berke, Sarah Kosting & Woodin, Sarah Ann, 2012, Diopatra (Onuphidae: Polychaeta) from intertidal sediments in southwestern Europe, Zootaxa 3395, pp. 47-58 : 49-50

Diopatra biscayensis , new species

Plate 1

Diopatra sp. A. Berke et al. 2010

Material examined: USNM 1128516, Chatelaillon Plage, France, 25 June 2006 (9); USNM 1128517, Chatelaillon Plage, France, 25 June 2006 (1); USNM 1128523 Tharon Plage, France, 16 June 2006 (holotype, position, ca 47°17’N, 2°16’E). USNM 1128522 Chatelaillon Plage, France. 25 June 2006, (paratype); USNM 1128521, Tharon Plage, France, 16 June 2006 (9 paratypes) USNM 1149420, Mont Saint-Michel Bay, France, 25 June 2010; USNM 1149421, Mont Saint-Michel Bay, France, 25 June 2010; USNM 1149422, Mont Saint-Michel Bay, France, 25 June 2010.

Diagnosis: Upper lip without median papilla and ridge. Dorsum without ornamentation. First four to five chaetigers with bidentate pseudocompound hooks; hoods moderately long and pointed. Two elongated postchaetal lobes in modified parapodia. Paired dorsal papillae absent. Subacicular hooks present from chaetiger 7–12 (chaetiger 9 in holotype). Pectinate chaetae with 18–20 or more teeth throughout body.

Description: All specimens anterior fragments with numbers of segments varying between 21 and 61 and length from 24 to 70mm; all with same width at chaetiger 10, 10 mm. Length proportionate to segments present. Total number of segments and structure of posterior end of the body unknown. Anterior end including first five chaetigers slightly narrower than next following segments dorsally strongly convex; ventrum less convex and tilted dorsally with mouth region and first pair of parapodia pointed anteriorly. Mid-body segments transversely narrowly rectangular with both dorsal and ventral side slightly convex. Longitudinal mid-ventral groove present in all chaetigers, but especially distinct in anterior segments. Prostomium and prostomial appendages brown; body color (as preserved) light ochre without distinct color patterns.

Fold between prostomium and peristomium semicircular in dorsal view. Antennae and palps enormous, covering most of dorsum of prostomium; attached along posterior edge of prostomium (Plate 1a). Frontal edge of prostomium with paired frontal lips varying in shape from ovoid to basally narrowed, distally conical and tapering. Upper lips medially distinctly separated (Plate 1b); each cushion-shaped with large distal papilla separated from rest of cushion by groove. Laterally mouth bordered by low ridges. Lower lip divided by shallow grooves into two narrowly triangular, flattened parts connected by frontally truncate low medial section. Two triangular sections projecting laterally as free, triangular flaps. Palps of holotype reach chaetiger 3, in other specimens reach from chaetigers 1–3. All antennae similar in length, reaching chaetiger 5–6 in holotype; in other specimens reaching chaetigers 4–13 depending on size of specimen. Palpophores with 12 rings in holotype; other specimens with up to 15 rings. Antennophores with12 rings in holotype, in other specimens with 11–15 rings. Palpophores and antennophores without lateral projections.

Peristomium slightly longer than first chaetiger in dorsal view; ventrally as a narrow ridge. Peristomial cirri present; about as long as peristomium. First five parapodia project mainly laterally, slightly anteriorly and ventrally; from chaetiger 6 parapodia projecting increasingly dorsally. First five parapodia with distinct, thick shafts slightly expanded distally (i.e., slightly clavate); more posteriorly parapodia conical; decreasing in length, but distinct as short cones in last chaetigers present. First several parapodia with wide prechaetal lobes; each with a bluntly triangular median distal end (Plate 1e); further posteriorly prechaetal lobes becoming low oblique ridges continuous around superior side with postchaetal lobes. Anterior postchaetal lobes low ridges covering chaetal bases, but with two elongated digitiform, tapering or subulate lobes (Plate 1f). Ventralmost lobe decreasing in size through modified parapodia and absent from an early unmodified parapodium. Dorsalmost lobe gradually decreasing in size but still distinct at posterior end of fragments; becoming increasingly flattened triangular in posteriormost segments. First four chaetigers with cirriform ventral cirri (Plate 1e–f); fifth ventral cirrus triangular and flattened; from chaetiger 6 ventral cirri replaced by thick glandular flattened pads. Pads reaching greatest size at about chaetiger 20; more posteriorly glandular areas decreasing in size and becoming rounded.

The first four or five parapodia with1–2 upper simple chaetae and 4–5 bidentate pseudocompound hooks. Hooks with short pointed hoods and smooth shafts (Plate 1c). Remaining parapodia mainly with strongly serrated limbate chaetae. Pectinate chaetae flat with straight distal margins, each with 18–20 teeth. Pectinate chaetae first present from chaetiger 6 in holotype, and from chaetigers 5–6 in other specimens. Starting from chaetiger 9 in holotype, and from chaetigers 7–12 in other specimens lower limbate chaetae replaced by thick bidentate subacicular hooks with very thin translucent guards (Plate 1d). Start of subacicular hooks weakly positively linked to increasing size of specimens.

PLATE 1. Diopatra biscayensis . USNM 118523, holotype.

a. dorsal view of anterior showing prostomium with palpophores and antennophores with proximal rings plus peristomium with peristomial cirri.

b. ventral view of anterior showing upper and upper lips and lower external lips with free lappets at the lateral ends.

c. and d. bidentate pseudocompound hooks from anterior modified parapodium.

e. anterior view of modified parapodium 1 with dorsal and ventral cirri and single, wide prechaetal lobe; the acicular lobe is represented by the rounded middle lappet.

f. posterior view of modified parapodium 2 with dorsal and ventral cirri and the double extended lobes of the postchaetal lobe of the parapodium.

Branchiae with up to six spiraled whorls of relatively short filaments present from chaetiger 4 and present through all segments in fragments.

Mandibles strongly sclerotinized with calcareous distal cutting plates. Distal indentations along edge of cutting plates distinct. Maxillae strongly sclerotinized with little evidence of calcifications. Maxillary formula: Mx I = 1 + 1; Mx II = 12+ 10; Mx III = 11 + 0; Mx IV = 6+ 8; Mx V = 1 + 1.

Tube basically cylindrical, upper end distally hooded and covered with debris consisting mostly of sea grass fragments and pieces of shells attached on all sides; permanently buried part of tube thin-walled and covered by fine sand.

Etymology. The name refers to the famously stormy bay along the coasts of France and Spain, the Bay of Biscay.

Discussion. Among the species reported in this paper, Diopatra biscayensis is uniquely characterized by the presence of double finger-shaped extensions of the postchaetal lobes in the modified anterior segments (Plate 1f). The free lappets at the lateral ends of the upper lips have not been mentioned in any other species (Plate 1b). Geographical distribution. Diopatra biscayensis is known from the French west coast as far north as Mont Saint Michel Bay south to Arcachon.