Mesochaetopterus, 2008

Martin, Daniel, Gil, João, Carreras-Carbonell, Josep & Bhaud, Michel, 2008, Description of a new species of Mesochaetopterus (Annelida, Polychaeta, Chaetopteridae), with redescription of Mesochaetopterus xerecus and an approach to the phylogeny of the family, Zoological Journal of the Linnean Society 152 (2), pp. 201-225 : 207-212

MESOCHAETOPTERUS ROGERI SP. NOV.

( FIGS 1 , 4–6 )

Diagnosis: Large Mesochaetopterus with welldeveloped peristomium, with a pair of long peristomial palps with a successive series of dorsal transversal black stripes, alternating one thick and wide with one to several thin narrow ones, sometimes with two longitudinal dorsal and ventral, orange to light-brown stripes, and a lateral black stripe (most often present in the first basal half of the palp), and two longitudinal ciliated grooves. Second pair of palps and eyes are absent. Region A with usually nine (more rarely ranging from 10 to 12) chaetigerous segments. Parapodia with notopodial lobes only, bearing capillary and lanceolate (dorsally) to oar-like and sickle-like (ventrally) chaetae. Fourth notopodia with usually 18 (ranging from 13 to 19) lanceolate knife-like and stout modified chaetae. Ventral glandular shield long, pale brownish. Region B with three elongated, flattened segments with biramous parapodia. Notopodia winglike, bearing about 15 capillary chaetae. Neuropodia unilobed (segment 1) and bilobed (segments 2 and 3), bearing uncini with eight (nine) teeth. Associated feeding organs in segments 2 and 3. Region C with all segments nearly similar, bearing biramous parapodia with unilobed chaetigerous notopodia and bilobed uncinigerous neuropodia. Associated feeding organs absent. Tube longer than 2.5 m, parchmentlike internally, externally fully covered by grains of sand. Tube ending unknown.

Region A: Holotype with nine segments (N = 14), but also found with ten (N = 2) or 12 (N = 1) segments, 0.8–1-cm long. Prostomium small, triangular, lightbrown dorsally, with a rounded, entire anterior border. Eyespots absent. Peristomium extended, twice as long as, and completely surrounding, the prostomium, contracted in fixed worms. Two peristomial lips, separated by a mid-ventral notch, with variable brownish dorsal pigmentation. Two long dorsally grooved palps arise dorsally just behind the junction of the lateroposterior peristomial borders, up to five times as long as region A in preserved worms (up to 15-cm long ‘ in vivo ’). Palps with a characteristic colour pattern composed of: (1) two longitudinal orange to light-brown stripes (one dorsal and one ventral), covering the whole palp in the last third; (2) several successive series of dorsal or dorsolateral transversal black stripes, alternating one thick and wide with one to several thin and narrow ones (less than one third of the thickness, and from half to one third of the width of the broad stripes); and (3) a longitudinal black stripe of variable length, usually in the first basal half of the palps, just at the lateral limits of the orange ventral bands. Longitudinal orange bands absent in some specimens. Two longitudinal ciliated grooves (one dorsal and one ventral) on each palp. Second pair of small antennae or palps absent. Eyes absent. Mouth as a vertical slit, below the prostomium and surrounded by the peristomium. Anterior end of the dorsal ciliated groove just behind the prostomium, between the basis of the palps, forming a small triangular lip. Dorsal ciliated faecal groove running from the mouth, through the median line, to the posterior end. Ventral plastron long, pale brownish in colour (often darker posteriorly), restricted to the ventral side of region A, without secretory crescents, but showing a characteristic distinct epithelium.

Parapodia of region A uniramous, short, with notopodia only. Chaetae yellowish to pale orange (up to dark brown in A4), occurring dorsolaterally on two irregular question mark shaped rows on segments A1–A3 and A5–A6, and in a single, irregular, question mark shaped row on segments A4 and A7–A12. Chaetal arrangement changing in segments A1, A2–A6 (except A4) and A7–A12; notopodia with 15 (A1) to 70 (A7–A12) long and fine lanceolate dorsal chaetae, becoming progressively capillary when more dorsal; notopodia of A1 with about 30 small lanceolate, oarlike chaetae lateroventrally; notopodia of A2–A3 and A5–A6 with up to 35 oar-like chaetae lateroventrally, the ventralmost chaetae twice as wide and long as the lateral ones, and twice as wide as the A1 ventral chaetae; from A7 to A12, the ventral notopodial oarlike chaetae being replaced with sickle-like chaetae (up to 60 chaetae per parapodia).

A4 notopodia with up to 20 yellowish, transparent, finely pointed capillary chaetae in dorsal position (d); four or five yellowish, transparent knife-like chaetae more than five times wider than the lanceolate ones (ld1); between one and three dark yellow to brownish knife-like chaetae, stouter that the previous ones, with the tip of the curved edge slightly serrated (ld2); 13–19 (typically 18) asymmetrical, knob-like, stout modified chaetae having serrated tips, the ventral chaetae (v) smaller than the lateral ones (lv1–lv2). Modified chaetae dark brown, often partly embedded in the notopodia.

Region B: Always with three segments, 2.5–3.5-cm long, as a flat plate-like region. Flattened and elongated segments with their flanks dorsally glandular, all them similar in size, longer than the segments in region C; B1 slightly narrower than B2 and B3. Associated feeding organs on posterior part of B2 and B3, only one per segment. Parapodia of region B biramous. Notopodia unilobed: B1 long, pointed, digitiform, distally slightly swollen (d1); B2 and B3 wider than B1, triangular, with a groove on the anterior side, distally slightly swollen, and with a dark pigmented band just before the distal swelling (d2, d3). From 11 to 13 extremely long and thin notochaetae, scarcely protruding from the tip of the notopodia; about 11 have tape-like tips, whereas two or three are capillary. Neuropodia unilobed in B1, with a single low ventral lobe (v1), and bilobed in B2 and B3, with a short, slightly anteriorly orientated dorsolateral lobe, and an elongate, posteriorly orientated ventral lobe (v2, v3). Uncini roughly D- shaped, with a single row of eight or nine minute teeth (most commonly eight); dorsal lobe with fewer uncini (about 60) than in the ventral lobe (over 400) in B2 and B3. Uncini of dorsal and ventral lobes in three or more irregular rows, with adjacent uncini somewhat displaced either up or down in relation to each other. Uncini of dorsal lobes with teeth directed posteriorly, whereas those of ventral lobes have anteriorly directed teeth. Uncini of dorsal lobes smaller than those on the ventral ones.

Region C: Known only from the holotype, incomplete, consisting of ten segments for about 5 cm in length. First segment longer than the remaining ones, but shorter than those of region B. Parapodia biramous, as a flat plate-like region with glandular lateral epithelium. Gut markedly protruding from the body plan, dark green in living and recently preserved specimens. Notopodia poorly developed, nearly triangular or wing-like, with three types of chaetae: between five and ten very long and thin, scarcely protruding from the tip of the notopodia, between three and nine with tape-like tips, and between one and three capillary. Associated feeding organs absent. Neuropodia all bilobed, similar to B2 and B 3 in shape, distribution, and number of uncini. Uncini roughly D- shaped, with a single row of eight or nine minute teeth (most commonly eight), slightly smaller in posteriormost segments.

Tube: Known part of the tube straight, completely buried into the sediment, except for the aperture, which protruded 1–2 cm from the sediment surface and was completely coated with grains of sand ( Fig. 1A ). From the surface opening the tube followed a vertical path downward for more than 2.5 m. Total tube length and shape of end still unknown. Tube structure very similar all along its length, with a relatively thin-walled, parchment-like material embedded with a thick external layer of sand grains, with a few (often only one) ramifications of the main tube at nonregular intervals, shorter than the main tube, filled with sand and closed at the junction by the main tube wall. Tube colour changes from yellowish to blackish at around 30 cm below the surface of the sediment. Detached fragments of sediment-filled or collapsed tubes of different diameters occur around the inhabited ones. Tube surrounded by a thick cylinder of sand all along its length, about 6 cm in diameter, more compact than the remaining sediment, and particularly evident when drilling around the inhabited tubes.

Etymology: Species name dedicated to Roger Martin (the first author’s elder son).

Material examined: Holotype: incomplete specimen, with regions A and B, and only ten segments of region C, measuring 110-mm long by 11 mm of maximum width, MNCN 6.01/10145 . Paratypes: 16 incomplete specimens (lacking region C), 13–15-m deep, Punta del Tordera , Blanes (Girona, Catalunya, Spain, 41.40°N, 2.48°E), collected by D. Martin, MNCN 16.01/10146. One incomplete specimen (lacking regions B and C), 7–10-m deep at Badalona (Barcelona, Catalunya, Spain, 41.27°N, 2.15°E), collected by L. Dantart and G. Álvarez, MNCN 16.01/ 10147 .

Known geographical distribution: Distributional area of the species ( Fig. 2 ) based on underwater observations. Andalucía, south-western Iberian Penninsula: 20–30-m deep on the west coast near Hotel La Parra, Almería (observed by A. Svoboda, see George & George, 1979); 5-m deep at Cabo de Gata, Almeria (observed by J. Junoy). Valencia, western Iberian Penninsula: 10–15-m deep at Cullera, south of the river Jucar (observed by J. Tena’s team); 11-m deep at Canet d’En Berenguer (observed by J. Tena’s team). Alicante, western Iberian Penninsula: 20-m deep at Punta del Rincón de Lois, Benidorm (observed by J. Tena’s team). Catalunya, north-western Iberian Penninsula: 5–7-m deep at Punta de la Mora, Garraf (observed by B. Weitzmann); 10–15-m deep at Badalona (observed by L. Dantart, G. Álvarez, and X. Turón); 30-m deep at Mataró (observed by L. Dantart); 20-m deep at Arenys de Mar (observed by B. Weitzmann); 10-m deep at Malgrat (observed by L. Dantart); 6-m deep at Blanes Harbour (observed by D. Martin); 6–10-m deep at Cala Sant Francesc, Blanes (observed by different CEAB divers); 6–15-m deep at Cala S’Aguia, Pinya de Rosa, Blanes (observed by different CEAB divers); 10–15-m deep at Cala Pola, Tossa de Mar (observed by the CEAB Caulerpa team); west of Urbanization Rosamar, Sant Feliu de Guixols, 20–30-m deep (observed by A. Svoboda).

Figures

Figure 1. Mesochaetopterus rogeri sp. nov. A, B, Two typical positions of the protruded tentacles in living worms (underwater pictures taken by L. Dantart). C, Regions A, B, and C (preserved worm, morphotype with reddish bands). D, Ventral view of region A (preserved worm, morphotype without reddish bands). E, Detail of the anterior end (dorsal view). F, Detail of the anterior end (dorsal view, tentacles removed). Ar, region A; b1–b3, segments of region B; d1–d3, dorsal rami of region-B segments; v1–v3, ventral rami of region-B segments; Cr, region C. Scale bars are in cm.

Figure 2. Mesochaetopterus rogeri sp. nov., location of reports. A, Iberian Peninsula. B, Catalan coast. C, Blanes litoral. Key:, seasonal monitoring at the Punta del Tordera; 1, Almería; 2, Alicante; 3, Valencia.

Figure 4. Mesochaetopterus rogeri sp. nov. A, Dorsalmost capillary chaeta from A1. B, Tip for the dorsalmost capillary chaeta from A1. C, Dorsal fine-lanceolate chaeta from A1. D, Tip of the dorsal fine-lanceolate chaeta from A1. E, Ventral oar-like chaeta from A1. F, Tip of the ventral oar-like chaeta from A1. G, Ventral oar-like chaeta from A3. H, Tip of the ventral oar-like chaeta from chaetiger A3. I, Dorsal fine-lanceolate chaeta from A8. J, Tip of the dorsal fine-lanceolate chaeta from A8. K, Ventral sickle-like chaeta from A8. L, Tip of the ventral sickle-like chaeta from A8. Scale bars are in Mm.

Figure 5. Mesochaetopterus rogeri sp. nov. A, Chaetal arrangement of the modified A4 chaetiger. B–L, Chaetae. B, Tip of the dorsal finely pointed capillary chaeta ‘d’. (C) Dorsolateral transparent knife-like chaeta ‘ld1’. D, Tip of the dorsolateral transparent knife-like chaeta ‘ld1’. E, Dorsolateral brownish knife-like chaeta ‘ld2’. F, Tip of the dorsolateral brownish knife-like chaeta ‘ld2’. G, I, K, Whole view of the typical modified chaetae ‘lv1’ (lateral), ‘lv2’ (lateroventral), and ‘v’ (ventralmost). H, J, L, Tips of G, I, K, respectively. Scale bars are in Mm.

Figure 6. Mesochaetopterus rogeri sp. nov. A, Dorsalmost uncini from neuropodia B1. B, Ventralmost uncini from neuropodia B1. C, Uncini from notopodia B2. D, Uncini from neuropodia B2. E, Uncini from notopodia B3. F, Uncini from neuropodia B3. G, Uncini from the anterior region of notopodia C2. H, Uncini from the posterior region of notopodia C2. I, Uncini from the anterior region of neuropodia C2. J, Uncini from the posterior region of neuropodia C2. Scale Bars are in Mm.