Pseudexogone dineti ( Katzmann, Laubier & Ramos, 1974 ) Salazar-Vallejo & Bailey-Brock & Dreyer, 2007

Salazar-Vallejo, Sergio I., Bailey-Brock, Julie H. & Dreyer, Jennifer C., 2007, Revision of Pseudexogone Augener, 1922 (Annelida, Polychaeta, Syllidae), and its transfer to Pilargidae, Zoosystema 29 (3), pp. 535-553 : 542-544

Pseudexogone dineti ( Katzmann, Laubier & Ramos, 1974) n. comb.

( Figs 3 ; 4 )

Synelmis dineti Katzmann, Laubier & Ramos, 1974: 28-31 , fig. 11. — Amoureux 1982a: 41; 1982b: 211.

Litocorsa dineti – Darbyshire & Mackie 2003: 65, table 1.

TYPE MATERIAL. — Adriatic Sea. Holotype presumably lost.

Croatia. Adriatic Sea, off Dubronik, sandy bottom, RV Jean Charcot, 42°27’N, 17°01.8’E, no date, 275 m, 3 paratypes ( NHMW- 13078).

TYPE LOCALITY. — Adriatic Sea, off Dubrovnik, Croatia, 42°27’N, 17°01.8’E, sandy bottom, 275 m.

ADDITIONAL MATERIAL. — Northeastern Atlantic Ocean. Thalassa , stn Z-414, 48°05’00”N, 08°20’08”W, off Brest, France, gravel, 650 m, 11 specimens (complete specimen 11 mm long, 0.15 mm wide, 52 chaetigers; notospines from chaetiger 6) (MNHN-A488, As418; one gold-coated in ECOSUR) .

DISTRIBUTION. — Northeastern Atlantic Ocean to the Adriatic Sea, in sandy bottoms in 275-650 m depth.

REDESCRIPTION

Paratypes ( NHMW-13078 ) three anterior fragments (one beheaded) ; larger anterior fragment with 38 chaetigers, notospines from chaetiger 7; smaller one with 16 chaetigers, notospines from chaetiger 6; head-less fragment with 11 chaetigers.

Prostomium subtriangular (corrugated in SEM specimen, Fig. 4A ), about as long as wide, narrower than peristomium ( Fig. 3A ). Three cirriform antennae of about the same size; lateral antennae placed in the middle of prostomium, over a low elevation, slightly ahead of median antenna, do not reach palp tips; median antenna on posterior prostomial margin. No eyes. Palps anteriorly rounded, distally separated, with one pair of ventrolateral papillae ( Fig. 3B, C ), cirriform, as long as antennae (collapsed in SEM specimen).Two pairs of cirriform tentacular cirri, dorsal pair slightly longer ( Fig. 4B ). Ciliary bundles eroded.

Parapodia uniramous in chaetigers 1-6(7), thereafter biramous. Parapodial cirri cirriform throughout body; dorsal cirri twice as long, and three times wider than ventral ones. Anterior parapodia ( Fig. 4C ) with notospines slightly exposed. Chaetae include an emergent, brittle, sigmoid bidentate notospine ( Fig. 3D, E ), first present in chaetigers 6-7, continued to posterior end; each notospine slightly curved (not sigmoid), with proximal tooth larger than distal one; neurochaetae 3-4 denticulate capillaries, some pectinates in a few anterior chaetigers, one smooth straight capillary ( Fig. 3F ), and one furcate chaeta remaining in a few anterior chaetigers. Furcates ( Fig. 4D ) with unequal tines, longer tine with a flaring curved blade not reaching the smaller, tapering tine. Posterior parapodia with notospines more exposed ( Fig. 4E ), with 2 denticulate capillaries and one pectinate neurochaeta; dorsal cirri cirriform, longer than ventral cirri. Bidentate notospines from median chaetigers ( Fig. 4F ) slightly exposed, with larger subdistal tooth and blunt distal tooth.

Pygidium not seen in paratypes. The original description stated that it has two ventrolateral cirriform cirri ( Fig. 3G ), about as long as the last achaetous segment. Brain with posterior lobes separated and passing the level of chaetal lobes in chaetiger 3. Pharynx 4.5 chaetigers long.

VARIATION

Specimens from northeastern Atlantic Ocean mostly anterior fragments; complete specimen was 9.5 mm long, with 51 chaetigers; others were eight anterior fragments, and two median fragments. Most had two brown eyespots external to the lateral antennae bases. Furcates were mostly broken but they seem to appear in chaetigers 1-2, and there are two furcates per bundle in chaetigers 1-3, then only one until chaetiger 5 or 6, thereafter they apparently disappear. One anterior fragment had its pharynx everted, it is distally smooth, barely surpassing palps.

REMARKS

Pseudexogone dineti n. comb. resembles P. helmuti n. sp. by lacking eyes. They differ in the relative devel- opment of the furcates blade; in P.dineti n. comb. the blade is curved, and straight in P. helmuti . Katzmann et al. (1974: 28) stated that the holotype was a complete specimen with 29 segments and that it had been formally deposited (and catalogued as NHMW- 13078). However, none of the specimens (labeled as paratypes in a small paper tag) were complete, so the holotype might be regarded as missing. On the other hand, Katzmann et al. (1974: 30) made an interesting discovery regarding the variation in the start of the notospines, since they found that in 13 out of 16 specimens, bidentate notospines started in chaetiger 6; in the other three specimens they started in chaetiger 7. Thus, it is a rather conservative feature. On the other hand, Darbyshire & Mackie (2003: 65) included S. dineti as a member of Litocorsa , despite the fact it has bidentate notospines and lacks neurospines. This inclusion prompted them to modify the generic definition. However, S. dineti belongs in Pseudexogone , not in Litocorsa , and the latter genus should be restricted as to include only those similar species provided with straight simple notospines, and neurospines.

Figures

FIG. 3. — Pseudexogone dineti (Katzmann, Laubier & Ramos, 1974) n. comb.: A, anterior end in dorsal view; B, same, seen from the left; C, same, ventral view showing the ventrolateral papillae; D, E, notospines and notaciculae, in side view; F, denticulate capillary and pectinate chaetae; G, posterior end in right lateral view (redrawn and rearranged from the original illustration by Katzmann et al. 1974). Abbreviations: see p. 536. Scale bars: A-C, 40 µm; D-F, 20 µm; G, 100 µm.

FIG. 4. — Pseudexogone dineti (Katzmann, Laubier & Ramos, 1974) n. comb.: A, anterior end in dorsal view; B, same, seen from the right; C, anterior parapodium showing larger dorsal cirrus;D, furcate from an anterior chaetiger;E, posterior parapodium; F, notospine from a median chaetiger. Abbreviations: see p. 536. Scale bars: A, B, 25.0 µm; C, 6.66 µm; D, 2.5 µm; E, 10.0 µm; F, 3.33 µm.