Chone americana Day 1973

Chone americana Day, 1973

Figures 1 A–J, 2A–E

Chone americana Day, 1973: 129, Fig. 17a–l.

Chone cf. americana sensu Uebelacker, 1984: 54 –12, Fig. 54–7, 8b–m.

Material examined

Type material: Paratypes [USNM 43137], North Carolina, off Beaufort, 34° 20’ N, 75° 57’ W, 80 m, June 4, 1965, Coll. BST, 25 W, sandy mud (50).

Non­type material: Eastern Florida [FSBC EJ71414] Cat. 34646, St. Lucie County, Hutchinson Island, East of F. P. & L. Electrical generating plant, 27° 21’ 23’’ N, 80° 13’ 24’’ W, 11.2 m (1 mounted in gold for SEM). [FSBC EJ71415] Cat. 34654, 27 ° 21’ 23’’ N, 80° 13’ 24’’ W, 11.2 m (1). [FSBC EJ71416] Cat. 34664, 27 ° 21’ 23’’ N, 80° 13’ 24’’ W, 11.2 m (1). [FSBC EJ71417] Cat. 34653, 27 ° 21’ 23’’ N, 80° 13’ 21’’ W, 11.2 m (1). [FSBC EJ71418] Cat. 34647, 27 ° 21’ 23’’ N, 80° 13’ 24’’ W, 11.2 m (3). [FSBC EJ71423] Cat. 34645, 27 ° 20’ 24’’ N, 80° 13’ 04’’ W, 12.1 m (1). [FSBC EJ71426] Cat. 34655, 27 ° 22’ 08’’ N, 80° 13’ 46’’ W, 11.2 m (1). [FSBC EJ71439] Cat. 34649, 27 ° 21’ 23’’ N, 80° 13’ 24’’ W, 11.2 m (1). [FSBC EJ71440] Cat. 34657, 27 ° 21’ 23’’ N, 80° 13’ 24’’ W, 11.2 m (1). [FSBC EJ72063] Cat. 34658, 27 ° 22’ 08’’ N, 80° 13’ 46’’ W, 10 m (2). [FSBC E J72066] Cat. 34648, 27 ° 22’ 08’’ N, 80° 13’ 46’’ W, 10 m (1). [FSBC EJ72121] Cat. 34659, 27 ° 22’ 08’’ N, 80° 13’ 46’’ W, 10.3 m (2). [FSBC EJ72122] Cat. 34651, 27 ° 22’ 08’’ N, 80° 13’ 46’’ W, 10.3 m (1). [FSBC EJ72125] Cat. 34652, 27 ° 22’ 08’’ N, 80° 13’ 46’’ W, 10.3 m (1). [FSBC EJ72151] Cat. 34660, 27 ° 22’ 08’’ N, 80° 13’ 46’’ W, 10.9 m (1). [FSBC EJ72152] Cat. 34661, 27 ° 22’ 08’’ N, 80° 13’ 46’’ W, 10.9 m (1). [FSBC E J73411] Cat. 34662, 27 ° 21’ 23’’ N, 80° 13’ 24’’ W, 10 m (1). [FSBC EJ73413] Cat. 34650, 27 ° 21’ 23’’ N, 80° 13’ 24’’ W, 10 m (2). [FSBC EJ73415] Cat. 34656, 27 ° 21’ 23’’ N, 80° 13’ 24’’ W, 10 m (1). [FSBC EJ73429] Cat. 34663, 27 ° 22’ 08’’ N, 80° 13’ 46’’ W, 9.7 m (1). [FSBC EJ73430] Cat. 34668, 27 ° 22’ 08’’ N, 80° 13’ 46’’ W, 9.7 m (2). [FSBC EJ73431] Cat. 34665, 27 ° 22’ 08’’ N, 80° 13’ 46’’ W, 9.7 m (4). [FSBC EJ73432] Cat. 34667, 27 ° 22’ 08’’ N, 80° 13’ 46’’ W, 9.7 m (6). [FSBC EJ73433] Cat. 34666, 27 ° 22’ 08’’ N, 80° 13’ 46’’ W, 9.7 m (2). [FSBC EJ81154] Cat. 43693, Dade County, North Biscayne Bay, in Safety Valve Coral Shoal are due east of station 24, 25 ° 38’ 28’’ N, 80° 09’ 57’’ W, 0.53 m (2). [FSBC EJ81159] Cat. 43695, 100’ W of ICW marker 8, 25 ° 54’ 01’’ N, 80° 08’ 02’’ W, 1.06 m (2). [FSBC EJ81160] Cat. 43694, 200’ E of piling just of mouth of New Arch Creek, 25° 53’ 59’’ N, 80° 08’ 30’’ W, 2.81 m (1). [FSBC EJ82170] Cat. 43692, 50’ S of day marker A on S side of Pelican Island, 25° 50’ 46’’ N, 80° 10’ 00’’ W, 2.43 m (1). [FSBC EJ81176] Cat. 43700, between Julia Turtle Causeway and San Marino Island, 25° 48’ 15’’ N, 80° 09’ 48’’ W, 2.05 m (2). [FSBC EJ81181] Cat. 43697, 20’ W of Claughton Island Channel marker 3, 25 ° 46’ 04’’ N, 80° 11’ 17’’ W, 2.20 m (1).

[FSBC EJ81183] Cat. 43698, Norris Cut, 25° 45’ 26’’ N, 80° 05’ 47’’ W, 4.72 m (3). [FSBC EJ81202] Cat. 43696, 100’ W of marker 1b located SW of Soldier Key, 25° 34’ 13’’ N, 80° 11’ 27’’ W, 2.59 m (1). [FSBC EJ77057] East coast of Florida, Rudolph 536 (1). Western Florida [USNM 90363] SOFLA, Sta. 16. 25° 45’ 42’’ N, 83° 11’ 04’’ W, Coll. BLM, November 1980, Sta. 16, 54 m (2). [USNM 90364] MAFLA, Sta. S–2854, 29 ° 24’00’’ N, 85° 42’ 02’’ W, Coll. BLM, August 1977, 42 m (1). [USNM 90365] SOFLA, Sta. 12, 29 ° 16’ 43’’ N, 83° 47’ 40’’ W, Coll. BLM, November 1980, Sta. 12, 90 m (1). [USNM 90366] MAFLA, Sta. V–2531, 29° 47’ 59’’ N, 86° 09’ 29’’ W, Coll. BLM, June 1975, 45 m (2). [FSBC EJ64017] Cat. 15474, Pinellas County, Boca Ciega Bay, 27° 48’ 17’’ N, 82° 45’ 53’’ W, 2 m (1). [FSBC] Off Treasure Island, Coll. Jack L. Taylor, September 1978, sand and shell, 3.04–4.57 m (2). [FSBC] West of Egmont Key, Transect 2, March 7, 1979, sand and shell, Coll. Jack L. Taylor, 6.09 m (4). [FSBC EJ73003] Florida Keys, Off Stock Island, KCP, 3–14–1 (1). Texas [USNM 90367] IXTOC, Sta. S–50, 26 ° 58’ N, 97° 20’ W, Coll. November 1979, 15 m (1). [USNM 90368] IXTOC, Sta. S–53, 26 ° 10’ N, 97° 08’ W, Coll. BLM, November 1979, 15 m (1).

Additional material: Chone infundibuliformis Krøyer, 1856. [CMN 3867] Eastern Canada, 1974–231, Byam Martin Channel, Sta. 10, 75 ° 01.4’ N, 106° 35’ W, R. K. S. Lee, July 14, 1974 (1). [SMNH 6861, 73073] W Greenland, Egedesminde, Coll. O. Torell (1). [SMNH 6862, 73074] W Greenland, Godhavn, 55 m, 69° 14’ N, Coll. C. T. Amondsen (2). [USNM 372] Greenland, locality unknown, Coll. Lütken (1). [ZMB 1986] Spitzbergen, Kükenthal S. G (2). [ZMB 3106] Grönland, Karajak Fjord, Coll. Vanhöffem (3). [ZMB 5167] Grönland, Coll. Grube–Ørsted (3). [ZMB 5168] Spitzbergen, Coll. Grube, Malmgren (1). [ZMB 6226] Spitzbergen, Exp. Rómer & Schaudinn, Sta. 13 (1), Sta. 36 (3), Sta. 13 (2), Sta. 41 (1), Sta. 513 (2), Sta. 12 (1), Sta. 41 (2), Sta. 34 (1), Sta. 14 (1), Sta. 32 (1). [ZMUC POL –1749] West of Greenland, Coll. Krøyer (1). [ZMUCPOL–1761] Lille Hellefiskebanke, 4 miles W. S. W. of Rifkol, July 10, 1912, 40 m, Coll. Bornemann (1). [ZMUC POL –1764] 4th Thule Expedition, East of Greenland, Sta. 26, Kangerolussuaq, August 20, 1933, 1–5 m (2).

Redescription

Color, body shape and size: Body pale in preserved material; cylindrical in thorax and anterior part of abdomen, depressed in posterior part of abdomen; BoL= 2.1–7.5 mm, W= 2.1–3.5 mm.

Branchial crown: BrCL= 1.5– 3 mm, RML/BrCL= 0.5/1. Radioles: 6–10 pairs, narrow flanges (Figure 1 B), pinnules long with similar length throughout radiole, RT= long­sized, tapered [20 pinnules]. BrL= small, insertion not exposed beyond collar. DL= 3 times longer than wide, without a discernable longitudinal ridge, with a basal plexus of blood vessels continuing distally as a single blood vessel (Figure 1 C). VL= rounded, as long as wide, about one half of DL length. VRA= 3–4 pairs, the inner one about a quarter of the BrCL, the remainder about one half of the BrCL.

Peristomium: APRL= not exposed beyond collar, ventral margin distally entire, long, triangular (Figure 1 A). PPRC= antero­dorsal, lateral and ventral margins entire, ventral slightly higher than dorsal. VSC= swollen, horseshoe­shaped, 2 times wider than long (Figure 1 A). PPRCL/ Ch 1L= 1/1.

Thorax: Chaetiger 1= Notopodia: two groups of 4–6 elongate, narrowly hooded chaetae. Chaetigers 2 to 8= Notopodia: SG= 2 rows of 4–5 elongate, narrowly hooded chaetae (Figures 1 G, 2C); IG= 1 anterior row with 4–5 bayonet chaetae (Figures 1 F, 2A, C), 2 posterior rows with 6 symmetrical, paleate chaetae with short mucro (Figures 1 E, 2A, C). Neuropodia: 1 row of 8–20 acicular uncini per torus, MF= 5, covering three quarters of the MF length, teeth above MF unequal in size, basal tooth bigger than teeth in distal rows (Figures 2 B, D), hood present, handles long (Figure 1 H). GR2= narrow, of same width around the segment.

Abdomen: AS = 12–50. Anterior segments: 2 transverse rows of 8–10 elongate, narrowly hooded chaetae, chaetae from upper row 50% shorter than chaetae in lower one; 10–12 uncini per torus, MF= 3–4, covering one half of the MF length, teeth above MF equal in size, breast rectangular, well developed, main fang not extending beyond breast, handles absent (Figure 1 I). Posterior segments: 3–4 modified, elongate, narrowly hooded chaetae, 25% longer than in anterior segments; 5–8 modified uncini per tori, smaller MF= 6–7, covering three quarters of the MF length (Figure 2 E), teeth above MF equal in size, breast rectangular, poorly developed, main fang not extending beyond breast, handles absent (Figure 1 J). Pygidium triangular with long cirrus (Figures 1 A, D).

Gametes: Female paratypes with oocytes in thorax; male paratypes with sperm in posterior segments of abdomen, nucleus barrel­shaped, head mushroom­shaped (one quarter of the nucleus length).

MGS: Anterior end of VSC not colored, lateral sides dark. Dorsally, each segment is divided by 2 dark rectangles, except the faecal groove. Ventrally, each segment is colored uniformly, except intersegmental lines and both pre­ and post­chaetal lobes. Pygidium stays darker for several days.

Remarks: The original description of Chone americana Day (1973) did not include some details, and for others, incomplete or misleading information was provided. Thus, it has to be redescribed to be properly compared with the remaining species in the genus. The redescription provided here is to point out that in C. americana: 1) radiolar flanges are narrow; 2) branchial lobes are not exposed beyond the collar; 3) dorsal lips lack a discernable longitudinal ridge; 4) margins of the posterior peristomial ring collar are entire; 5) thoracic uncini with teeth above the main fang are unequal in size, basal tooth being bigger than teeth in distal rows; 6) uncini from posterior abdominal segments are modified; 7) females bear oocytes in the thorax, and males have sperm with barrel­shaped nuclei and mushroom­shaped heads.

Chone americana is unique among Western Atlantic Chone species in having a pygidial cirrus; the other species with a pygidial cirrus is C. filicaudata Southern, 1914, from Ireland, but this has the anterior peristomial ring lobe incised, whereas it is intact in C. americana.

Scanning Electronic Microscopy reveals an important character in C. americana and in the rest of the new species described in this manuscript: thoracic acicular uncini have the teeth above the main fang of unequal size (Figure 2 C). In his generic diagnosis Fitzhugh (1989) considered that teeth above the main fang are of the same size. However, the unequal­size feature was also found in specimens of Chone infundibuliformis, type species for the genus collected in Eastern Canada CMN 3867 (Figure 2 F). This observation was further corroborated with topotype material of C. infundibuliformis (see list of additional material). The presence of unequal­sized teeth above the main fang in thoracic uncinus is the synapomorphy for Amphicorina, according to Fitzhugh (1989). This character, however, is homoplasic, occurring in most of the fabriciin genera and its presence is now corroborated in some species of Chone.

The modified uncini from posterior abdominal segments in C. americana (Figure 2 E), and in the new species described in this manuscript, are rasp­shaped plates or Amphicorina ­ type (see Rouse 1994: Figure 17). This kind of uncini has a quadrangular, rectangular or sub­rectangular poorly developed breast, and a main fang covered by several rows of teeth equal in size (Figure 1 J), occupying at least three quarters of the main fang length. This manuscript is part of an ongoing revision of the genus Chone, and these important observations will be used in a future analysis to evaluate the phylogeny of the genus.