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Description

Chlanidota (Pfefferia) palliata
(Strebel, 1908)
Figs. 17, 18, 19, 20; Table 7

 

 

Pfefferia palliata Strebel, 1908:34-5, pl. 3, fig. 39a–f; Thiele, 1912:pl. 16, fig. 20 (radula); Powell, 1951:143; Carcelles, 1953: 193.

 

Pfefferia elata Strebel, 1908:35, pl. 3, fig 40; Powell, 1951:142, 194, fig. L78 (radula), 196, fig. N 128 (operculum).

 

Pfefferia cingulata Strebel, 1908:36, pl. 3 fig. 42a–c; Powell, 1951:142-3, 194, fig L79 (radula); Carcelles, 1953: 193.

 

 

Description.—Shell (Fig. 18) large for genus (to 34.5 mm, Powell, 1951:142), thick, solid, ovate-rounded. Protoconch early teleoconch whorls eroded in all specimens. Teleoconch with up to 4 evenly inflated whorls. Shoulder not pronounced Suture deep, adpressed, narrowly channeled. Spiral sculpture of alternating broad, low cords (10-17 on body whorl, 3-5 on penultimate whorl) and fine threads (20-24 per 5 mm), spanning entire shell surface. Cords more clearly visible on young spec­imens with thinner periostracum. Axial sculpture limited to indistinct growth lines. Aperture tall, ovate, deflected from the shell axis by 16-18°. Siphonal canal is not pro­nounced. Outer lip evenly rounded, thick, weakly reflected in adults, very thin in ju­venile and some adult specimens. Columel­la <½ AL, weakly concave, with fine pus­tules. Siphonal fold strong. Callus thick, clearly demarcated, narrowly overlying pa­rietal region, siphonal fasciole in mature specimens. Siphonal notch broad, dorsally reflected, columellar margin straight, aper­tural margin rounded, reflected, forming pronounced ridge margin along adapical edge of fasciole. Shell color grayish white, translucent. Periostracum very thick, tightly adherent to shell surface, with evenly spaced, axially reflected lamellae with fringed edges evident on early whorls and juvenile specimens (Fig. 19C). Operculum (Fig. 16A, D) large, leaf-shaped, with api­cal nucleus, massive, raised, lamellose bor­der along posterior margin, 0.67-0.83 AL. Attachment area spans nearly entire inner surface, posterior, left margins thickened, glazed.

 

Ultrastructure.—(fig. 19E) Outermost layer prismatic (≈50 µm), middle layer comarginal crossed-lamellar (≈175 µm), inner layer radial crossed-lamellar (≈95 µm). Inner surface of the outer aperture lip with numerous, fine spherules (Fig. 17D).

 

External anatomy.—Body of 2½ whorls (Fig. 18A, B), mantle cavity spanning ≈½ whorl, kidney 1/5 whorl, digestive 1¾ whorl. Foot of preserved specimens short (L/W ≈1), with rounded posterior edge. Head narrow, with stout, conical tentacles, eyes on small lobes. Body lacks pigmentation.

 

 

Table 7. –Chlanidota (Pfefferia) palliata (Strebel, 1908). Measurements of shell characters. Linear measurements in mm (n = 10, type material not included).

                                                                                              
 

Character

 
 

Mean

 
 

σ

 
 

Range

 
 

Lectotype of C. palliata

 
 

Lectotype of C. cingulata

 
 

Holotype of C. elata (broken)

 
 

Shell Length (SL)

 
 

27.1

 
 

3.6

 
 

18.1-30.0

 
 

32.8

 
 

25.9

 
 

~37

 
 

Body Whorl Length (BWL)

 
 

24.6

 
 

3.4

 
 

16.4-27.1

 
 

29.2

 
 

23.7

 
 

~32

 
 

Aperture Length (AL)

 
 

19.3

 
 

2.0

 
 

14.4-20.4

 
 

23.5

 
 

19.8

 
 

~23

 
 

Shell Width (SW)

 
 

19.4

 
 

2.3

 
 

14.0-21.2

 
 

23.4

 
 

19.4

 
 

~22

 
 

Operculum Length (OL)

 
 

14.1

 
 

2.0

 
 

9.6-16.7

 
 

-

 
 

15.4

 
 

-

 
 

BWL/SL

 
 

0.91

 
 

0.02

 
 

0.86-0.95

 
 

0.89

 
 

0.92

 
 

~0.86

 
 

AL/SL

 
 

0.72

 
 

0.04

 
 

0.67-0.80

 
 

0.72

 
 

0.76

 
 

~0.62

 
 

SW/SL

 
 

0.72

 
 

0.03

 
 

0.68-0.78

 
 

0.71

 
 

0.75

 
 

~0.60

 
 

OL/AL

 
 

0.73

 
 

0.06

 
 

0.67-0.83

 
 

-

 
 

0.78

 
 

-

 
 

 

Mantle cavity.—Mantle edge smooth. Si­phon medium to long, muscular, extending substantially beyond mantle edge (≈⅓ AL). Osphradium dark greenish-brown, bipectinate, spans ≈½ mantle length. Hypobranchi­al gland of few, distinct, widely spaced folds. Ctenidium large, wide, spans ≈¾ mantle length, lamellae tallest in posterior ¼ of ctenidium, becoming shorter anterior­ly.

 

Alimentary system.—Proboscis (Fig. 19C, D, pr) thick (L/D ≈ 3.5), of moderate length (0.9 AL). Mouth opening, triangular slit. Buccal mass muscular, large, nearly equal to retracted proboscis in length. Odontophoral cartilages paired, fused an­teriorly, spanning ≈⅔ of proboscis length. Radular ribbon (Fig. 18A, B) of moderate length, 10.6 mm (0.66 AL), ≈760 µm wide (0.05 AL), triserial, consisting of 60-65 rows of teeth, posteriormost 5 nascent. Rachidian teeth with arched base, nearly straight lateral sides, 3 large, robust cusps of equal length. Central cusp longer than flanking cusps in one specimen (Fig. 18A, B). Lateral teeth with 3 cusps, outer cusp longest, intermediate cusp shortest, adjacent to inner cusp. Intermediate cusp nearly fused to inner cusp in one specimen (fig. 18A, arrow). Salivary glands small, fused (Fig. 19G), situated above nerve ring. Right salivary gland completely covering valve of Leiblein. Salivary ducts run loosely along both sides of oesophagus, entering esopha­geal wall near posteriormost portion of re­tracted proboscis. Valve of Leiblein (Fig. 18E, vL) well defined, large, without cili­ated cone. Gland of Leiblein (Fig. 18C–E, gL) long, tubular, coiled anteriorly, tapering posteriorly. Oesophagus wide, muscular, expanding posteriorly to form crop (Fig. 18I, poe) lined with tall longitudinal folds. Stomach (Fig. 18H, I) U-shaped, without caecum. Ducts of digestive gland paired, closely spaced, transverse fold slightly raised. Typhlosoles present, poorly defined. Rectum terminating with well defined anal papilla.

 

Female reproductive system.—Typically buccinoidean. Oviduct opens into medium-sized albumen gland. Ingesting gland sin­gle. Capsule gland large, occupies ≈½ of mantle cavity. Bursa copulatrix present, simple, hemispherical.

 

Male reproductive system.—Very similar to that of C. (C.) densesculpta, penis has the same size, overall shape, terminal pa­pilla.

 

Type locality.—[Pfefferia palliata & P. elata] South Georgia, 54°17'S, 36°28'W, in 75 m (Sveska Südpolarexp., Sta. 22); [Pfef­feria cingulata] Cumberland Bay, South Georgia, 54°11'S, 36°18'W, in 252-310 m. (Sveska Südpolarexp., Sta. 34).

 

Type material.—[Pfefferia palliata] Lec­totype (here designated) SMNH (fig. 17A–C), and 2 paralectotypes SMNH (fig. 17E); [Pfefferia elata] Holotype, SMNH 3661 (Fig. 171), broken specimen; [Pfefferia cin­gulata] Lectotype (here designated) (Fig. 16F–H) and juvenile paralectotype, SMNH.

 

Material examined.—Type material. R/V Islas Orcadas: Sta. 31, 19 May 1975, 54°05.36'S, 36°30.48'W, 130-143 m, 1 shell, USNM 887863; Sta. 32, 19 May 1975, 54°21.36'S, 35°58.42'W, 141-164 m, 1 shell, USNM 887872; 9 shells, USNM 887867; Sta. 33, 19 May 1975, 54°30.7'S, 35°35.9'W, 261-267 m, 27 specimens, USNM 901676.

 

Published records.—R/V Discovery II, Sta. 30, West Cumberland Bay, South Georgia, 2.8 miles S, 24°W of Jason Light [16 Mar 1926], 251 m (Powell, 1951:142).

 

Distribution.—Known only from off the northeastern coast of South Georgia (Fig. 19). Live material was collected between 75 and 310 m.

 

Remarks.—The type specimens of Chlanidota (Pfefferia) palliata and C. (P.) elata were taken from the same dredge haul. Strebel (1908) distinguished these taxa primarily on the difference in their spire height and the strength of their spiral sculpture, but questioned whether these dif­ferences merited specific recognition. We were able to examine a larger sample than was available to Strebel (USNM 901676, n = 27) and found it to contain specimens spanning a morphological continuum be­tween these two forms. The type series of C. (P.) cingulata was collected very near the type locality of C. (P.) palliata, but at slightly greater depth. The specimen select­ed as lectotype of C. (P.) cingulata is, in our opinion, conspecific with the specimen selected as lectotype of C. (P.) palliata, as both fall within the range of morphological variation found in a single population (USNM 901676). Since Powell (1951) des­ignated P. palliata to be the type species of Pfefferia, we retain this name for this spe­cies, and synonymize the remaining nomi­na.

 

Powell (1951:142) noted that the only radula he examined was abnormal, with two small, "incipient" cusps flanking the nor­mally tricuspid rachidian teeth. The radulae we examined were typical of Chlanidota.

 

Juvenile specimens are bicolored, with the periostracum being dark chestnut brown above the periphery, and a pale, olive green below the periphery. The periostracum of adult specimens is thicker and uniformly chestnut brown in color. Conchologically this species is similar to C. (C.) dense­sculpta, but may be readily distinguished on by the presence of weakly raised spiral cords, as well as by its distinctive opercu­lum.”

 

 

(Harasewych, 1999: 281-285)

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© National Museum of Natural History, Smithsonian Institution

Source: Antarctic Invertebrates Website (NMNH)

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