Pseudexogone williamsae, 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 : 550-552

Pseudexogone williamsae n. sp.

( Fig. 8 )

TYPE MATERIAL. — Eastern Pacific Ocean. USA, Bureau of Land Management Southern California Baseline Studies, off Southern California, Allan Hancock Foundation cruise 1341, RV Velero IV, stn 22979, 33°50.88’N, 119°59.91’W, 6.1 miles, 13° T to East Point, Santa Rosa Island, 78 m, box core, coarse biogenic sand with occasional pebbles, 15.X.1975, holotype ( LACM-AHF POLY 2184) and paratype ( LACM-AHF POLY 2185). — Allan Hancock Foundation cruise 1341, RV Velero IV, stn 23039, 33°52.97’N, 120°01.05’W, 4.5 miles, 34° T to East Point, Santa Rosa Island, 57 m, box core, muddy fine sand with shell, 17.X.1975, 1 paratype (23039 ECOSUR). — RV Thomas G. Thompson, stn 80901, 33°46.2’N, 119°50.9’W, NW slope Santa Cruz Basin, 22 km SSW of Gull Island, Santa Cruz Island, BLM 80, 222- 271 m, sand, 21.VIII.1977, 2 paratypes ( LACM-AHF POLY 2186, another one ECOSUR).

ADDITIONAL MATERIAL. — Eastern Pacific Ocean. California, Allan Hancock Foundation cruise 1341, RV Velero IV, stn 22943, 32°44.05’N, 119°06.17’W, 35.7 miles, 83.5° T to China Point, San Clemente Island, 319 m, box core, indurated mud and fine sand with rocks, 12.X.1975, 1 specimen ( LACM-AHF). — RV Thomas G. Thompson, stn 818-10, 32°53.3’N, 119°23.4’W, 34 km NW of pinnacle, Tanner Bank, California Channel Islands, 113 m, box core, shell and coarse sand, 24.VIII.1977, anterior fragment ( LACM-AHF).

Western Mexico. Seamount studies (see Levin et al. 1994 for details; most in LACM-AHF), Alvin Dive 2318, Fieberling Guyot , 992 km W of San Diego, Sea Pen Rim , on northeast perimeter of top, box 1, Rep. 6, 0-1 cm, SPR, 32°27.631’N, 127°49.489’W, 636 m, basaltic and calcareous sands, 4.XII.1990, 3 specimens ( LACM-AHF). — Alvin dive 2318, box 1, Rep. C, 5-10 cm, SPR, 32°27.631’N, 127°49.489’W, 636 m, basaltic and calcareous sands, 4.XII.1990, 1 specimen ( LACM-AHF). — Alvin dive 2327, box 1, Rep. 8, 5- 10 cm, 32°27.631’N, 127°49.489’W, 636 m, basaltic and calcareous sands, 13.XII.1990, 1 specimen ( LACM-AHF). — Alvin dive 2401, box 3, 1- 2 cm, SPR, 32°27.631’N, 127°49.489’W, 636 m, basaltic and calcareous sands, 23.X.1991, 1 specimen (LACM- AHF). — Alvin dive 2401, box 1, Rep. 8, 0-1 cm, SPR, 32°27.631’N, 127°49.489’W, 636 m, basaltic and calcareous sands, 27.X.1991, 2 specimens (one gold-coated, ECOSUR, the other LACM-AHF). — Alvin dive 2322, White Sand Swale, 32 box 2, Rep. 1, 2- 5 cm, WSS, 32°27.581’N, 127°47.839’W, 579 m, nearly white foraminiferal and calcareous sands, 8.XII.1990, 1 specimen ( LACM-AHF). — Alvin dive 2326, White Sand Swale, 32 box 2, Rep. C, 1-2 cm, 32°27.581’N, 127°47.839’W, 582 m, nearly white foraminiferal and calcareous sands, 12.XII.1990, anterior fragment ( LACM-AHF). — Alvin dive 2322, White Sand Swale, 32 box 5, Rep. A, 2-5 cm, WSS, 32°27.581’N, 127°47.839’W, 579 m, nearly white foraminiferal and calcareous sands, 8.XII.1990, 2 specimens ( LACM-AHF) .

TYPE LOCALITY. — Off Santa Rosa Island, Southern California, in shallow water.

ETYMOLOGY. — This species name is made after Susan Williams who has worked during many years on Californian polychaetes, and who indicated that some of these specimens belong to an undescribed genus and species.

DESCRIPTION

Holotype complete, 32 mm long, 0.3 mm wide, 101 chaetigers. Prostomium corrugated in SEM specimens ( Fig. 8A, B ), with palps irregularly wrinkled, free from each other; ventrolateral papillae directed laterally, slightly shorter than lateral antennae. All antennae cirriform, median one slightly longer than laterals; lateral antennae placed medially on prostomium, slightly ahead of median, median antennae placed over projected border on posterior margin of prostomium. One pair of eyes, each one placed on the inner side of the lateral antennae; original brown pigment faded, retina and lens visible. Tentacular segment biannulate, first ring laterally reduced; tentacular cirri ventrolaterally placed, dorsal cirrus slightly longer than ventral one. Ciliary bundles eroded.

Chaetiger 1 biannulate, then mostly 3-annulated to chaetiger 10, thereafter with 6-8 rings, continued to posterior end; less clearly noticeable in elongated segments. Parapodia uniramous in chaetigers 1-5, biramous thereafter.Dorsal and ventral cirri cirriform, dorsal ones longer. Chaetal lobe rounded with 4-6 neurochaetae;two elongated denticulate capillaries, two shorter pectinates, and two shorter furcates.Anterior parapodia ( Fig. 8C ) with cirriform cirri, dorsal and ventral cirri of about same length; 1 or 2 denticulate capillaries and 1 or 2 pectinates; single furcate per bundle, with longer tine flared, blade margin straight, not reaching smaller digitate tine. Median chaetigers ( Fig. 8D ) with bidentate curved notospines, clearly exposed along all body, present to last chaetiger; each notospine ( Fig. 8E, F ) markedly curved with larger subdistal tooth and tiny distal tooth. Furcates apparently restricted to chaetigers 3-8. From chaetiger 6, slightly exposed bidentate curved notospine, becomes more exposed in posterior chaetigers.

Posterior end with one achaetous segment (without it in SEM specimen, Fig. 8G ); pygidium rounded, as long as last two segments, anus dorsal, with two ventrolateral cirriform cirri, as long as pygidium. Brain posterior lobes long, separated, reaching the level of chaetal lobes of chaetiger 3. Pharynx not everted, about 1.5 chaetigers long. Few oocytes, singly in chaetigers 65-97, each about 30 µm.

VARIATION

Type and non-type specimens were 5-32 mm long, 0.23-0.30 mm wide, with 37-110 chaetigers. Most were thin but a few were markedly contracted showing highly annulated integument; other morphological features were unaltered. All had pale brown eyes placed at the inner side of lateral antennae, and bifid curved notospines from chaetiger 6. Mature females with large oocytes in posterior third of body; some specimens were small (AD2318, Rep. C), being only 7.5 mm long with 39 chaetigers; one paratype (BFI 23039) being 11 mm long with 55 chaetigers, had oocytes in chaetigers 37-55. Oocytes were ovoid, about 30 µm long, with a small nucleus and showing different content and size of granules, or even hyaline, but always irregularly wrinkled (probably due to preservation). There was some variation in the amount of eggs per segment and these differences could be related to the steps between maturation and spawning.

REMARKS

Pseudexogone williamsae n. sp. resembles P.backstromi and P.imajimai n. sp. It differs from them by having furcates with a thick smaller tine.

Figures

FIG. 8. — Pseudexogone williamsae n. sp.: A, anterior end, lateral view, the left ventrolateral papilla is bent posteriorly; B, same, dorsal view; C, chaetae from chaetiger 8; D, median chaetiger; E, F, notospines from posterior chaetigers; G, posterior end in dorsal view, anal cirri are bent over the pygidial posterior margin. Abbreviations: see p. 536. Scale bars: A, 50 µm; B, 12.5 µm; C, 5.0 µm; D, 14.0 µm; E, 8.33 µm; F, 5.0 µm; G, 25.0 µm.