Thieleella kelseyi ( Dall, 1905 )

Geiger, Daniel L. & Mclean, James H., 2010, New species and records of Scissurellidae and Anatomidae from the Americas (Mollusca: Gastropoda: Vetigastropoda), Zootaxa 2356, pp. 1-35 : 22-28

Thieleella kelseyi ( Dall, 1905)

Figures 16–19

Scissurella (Schizotrochus) kelseyi Dall, 1905: 124 –125, not illustrated.

Scissurella kelseyi: Thiele, 1912: 18 .

Scissurella kelseyi: Dall, 1921a: 183 .

Scissurella kelseyi: Oldroyd, 1924: 180 .

Scissurella kelseyi: Oldroyd, 1927: 228 .

Scissurella kelseyi: Keen, 1937: 45 .

Scissurella kelseyi: Burch, 1946a: 27 .

Scissurella kelseyi: Burch, 1946b: 23 .

Scissurella kelseyi: Draper, 1973: 8 .

Misidentifications

Scissurella kelseyi non Dall, 1905: Talmadge, 1966: 83 [Identification fide McLean, 1967, is A. lamellata . McLean (1984) identified “ A. lamellata ” sensu McLean (1967) from the eastern Pacific as A. baxteri , but did not list the Talmadge record].

Anatoma crispata (non Fleming, 1828): McLean, 1996: 17, fig. 1.2 [is T. kelseyi ].

Scissurella (Anatoma) crispata: McLean, 1967: 405 , pl. 56, figs 1–4 [includes A. chiricova and A. japonica . Illustrated specimen is T. kelseyi ].

Type material. Holotype ( USNM 181820. Lost: McLean 1967: 405, Geiger pers. obs. 2. 2004), 5.5 × 6 mm (H × W). Neotype here designated ( SBMNH 3215: see remarks).

Type locality. California at U.S. Fish Commission Station 4353 [32.700˚N, 117.233˚W], also off San Diego (OD), 639 fms [= 1169 m], 15 mls from Pt. Loma, 47˚W ( USNM label). Neotype locality: 183 m, off La Jolla, California, USA [32.843˚N, 117.392˚W].

Etymology. Named in honor of Prof. F. W. Kelsey, of San Diego (OD).

Description. Shell large (to 6 mm: fide Dall, 1905), trochiform, biconical, white. Protoconch of 0.75 whorls, with reticulate sculpture, apertural varix barely connected to embryonic cap, apertural margin straight. TI of 0.75 whorls, with approximately 38 axial cordlets, one spiral cordlet in position of selenizone, interstices with flocculent sculpture. TII of 3.125 whorls in 3.2 mm specimen, space between suture and selenizone as wide as selenizone showing approximately the uppermost three spirals. Shoulder somewhat convex, suture lightly impressed, axials approximately of same density and strength as on TI, approximately 22 equispaced fine spiral lines running over cordlets. Base with slight constriction below selenizone, axials of same strength and density as on shoulder, crossed with approximately 32 equispaced spiral lines, interstices with fine irregular growth lines. Umbilicus very narrow, evenly curving with base, funiculus present. Selenizone slightly above periphery, keels of moderate strength and moderate elevation, growth marks rather weak; slit open with parallel margins. Aperture rounded, adumbilical portion flared, roof overhanging. Operculum corneous, thin, multispiral with central nucleus.

Radula. Rachidian tooth trapezoid, central denticle largest, approximately 6 denticles on each side. Lateral teeth 1–3 similar, apical denticle largest; 3–4 denticles on outer cutting edge; 1–2 denticles on along inner edge, half size of outer denticles. Lateral tooth 4 reduced, hookshaped, apical denticle largest, 3–4 minute denticles on inner edge. Lateral tooth 5 enlarged by elongation, apical denticle largest, approximately 12 denticles along inner edge, approximately 4 denticles along distal half of cusp’s outer edge. Inner marginal teeth with triangular cusp on long shafts, apical denticle largest, approximately 6 denticles on each side. Outer marginal teeth thin, broadened, with many small bristles along edge of cusp. Radular interlock of central field moderate.

Body. Tentacles in anterior-posterior order: cephalic tentacles papillate; ocular stalk without pigmented eye; two distinct, non-papillate tentacles in neck region in anterior-posterior alignment with cephalic tentacle and first epipodial tentacle; bifid papillate epipodial tentacles with single posterior blunt, stubby non-papillate structure about half as long as second epipodial tentacle, most likely elongated epipodial sense organ (ESO); two single papillate epipodial tentacles. Operculum attached to discrete fine flap of metapodium.

Mantle with papillate tentacle at posterior junction of slit near anal papilla. Two monopectinate gills, approximately 25–30 gill leaflets each, distinct bottle-shaped bursicles in distal half of each filament, opening of bursicles in middle of filament.

Differential Diagnosis. Anatoma keenae ( McLean, 1966) [= A. epicharis ( McLean, 1966) ] from the Panamic province has a protoconch with flocculent sculpture (reticulate in T. kelseyi ), on TI lacks a spiral cord in the position of the selenizone (present in T. kelseyi ), and forms small but distinct points at the intersection of spiral and axial cords on TII (no points in T. kelseyi ). Thieleella baxteri from the northeastern Pacific has a TI of approximately 0.5 whorls (0.75 in T. kelseyi ) and axial sculpture consisting of raised lamellae (simple cords in T. kelseyi ). Anatoma lyra (Berry, 1947) , from the northeastern Pacific has a protoconch with flocculent sculpture (reticulate in T. kelseyi ), overall stronger and less dense sculpture, and a distinct funiculus in the umbilicus (absent in T. kelseyi ).

Distribution. Queen Charlotte Islands, British Columbia, Canada, to South Coronado Island, northern Baja California, Mexico (Dall 1921).

Specimen records. USA: California. 1503 m, US Fish Comm. St. 2923, off San Diego (USNM 209412, 4). 1033–1244 m, 16 miles SW off Point Loma, 32.700˚N, 117.246˚W (USNM 211166, 4).

San Diego Trough: 1171–1241 m, 32.417˚N, 117.467˚W (SIO M1974, 1: complete). 1166–1222 m, 32.450˚N, 117.467˚W (SIO M1991, 1, 5: complete). 1207–1234 m, SIO69-487, 32.450˚N, 117.525˚W (SIO M2070, 3: complete). 1183–1216 m, R-28, 32.583˚N, 117.558˚W (SIO 2171, 1: complete). 1241 m, R-42, 32.440˚N, 117.483˚W (SIO M1778, 1: complete). 1199–1241 m, R-17, 32.447˚N, 117.467˚W (SIO M1834, 2: complete).

San Clemente Island: 390 m, off Tanner Bank, 32.683˚N, 119.234˚W (LACM 76-313, 6). 1047 m, 32.585˚N, 118.965˚W (LACM 76-378, 6). 933 m, 30.8 mi, 65˚T of China Point, 32.583˚N, 118.982˚W (LACM 76-377, 2). 973 m, California, USA, 32.569˚N, 118.984˚W (LACM 76-381, 5). 292 m, 32.566˚N, 119.131˚W (LACM 76-387, 4). 201 m, 32.772˚N, 118.379˚W (LACM AHF 1082, 1).

Between Tanner Bank and Cortez Bank, 32.450˚N, 119.250˚W (SBMNH 33350, 1). 1200 m, Off N. Coronado Island, 32.750˚N, 117.500˚W (USNM 208901, 3; USNM 209054, 3). 183 m, off La Jolla, 32.8430˚N, 117.392˚W (SBMNH 3215, 1).

Santa Rosa Island: 70 m, 33.531˚N, 119.982˚W (LACM 77-303, 1). 115 m, 33.865˚N, 119.917˚W (LACM 75-300, 6). 61 m, 33.865˚N, 120.030˚W (LACM 75-306, 1). 105 m, 33.934˚N, 119.901˚W (LACM 75-480, 1). 442 m, 33.884˚N, 120.316˚W (LACM 76-213, 8). 421 m, 33.850˚N, 120.183˚W (LACM 23129, 2: complete). 492 m, Off Point Sal, California, USA, 34.970˚N, 121.298˚W (SBMNH 350392, 1; SBMNH 350392, 2).

USA: Oregon. 1580 m, 45.828˚N, 125.233˚W (LACM 67-167, 1).

Canada: British Columbia. 2176 m, Estevan Point Light, Hesquiat Peninsula, Noetka Sound, Vancouver Island, 48.635˚N, 126.967˚W (LACM 71-374.7, 3: complete). 1602 m, off Queen Charlotte Sound, 51.500˚N, 129.000˚W (USNM 206690, 1). 55 m, Naden Harbor, N side of Graham Island, Queen Charlotte Island, 54.000˚N, 132.667˚W (LACM 66-66, 0). 260 m, Dixon Entrance, N of Graham Island, 54.483˚N, 133.200˚W (LACM 67-28, 2).

USA: Alaska. 88 m, NW of Gibson Island, off NE side Attu Island, Near Islands, 52.958˚N, 173.237˚W (LACM 86-312, 5). 179 m, S of Coronation Island, W of N end Dall Island, 55.143˚N, 134.210˚W (LACM 87-377, 2).

Baranof Island: 278 m, W of gulf of Esquibel, S of Byron Bay, 55.537˚N, 134.891˚W (LACM 87-369, 27). 205 m, W of N end Baker Island, S of Cape Ommany, 55.394˚N, 134.675˚W (LACM 87-370, 20). 443 m, W of Nation Point, Coronation Island, SW of Cape Ommaney, 55.925˚N, 135.438˚W (LACM 87-365, 8). 252 m, SW of Cape Ommaney, S end, 56.000˚N, 135.000˚W (LACM 87-357, 2). 364 m, W of Pt. Howard, Kulu Island, S of Sitka, 56.037˚N, 135.307˚W (LACM 87-364, 13). 362 m, W of Pt. Crowley, Kulu Island, S. of Necker Bay, 56.090˚N, 135.150˚W (LACM 87-363, 9). 240 m, S of Kruzof Island, W of Necker Bay, 56.598˚N, 135.782˚W (LACM 87-358, 100). W of Whale Bay, SSW of Biorka Island, 56.514˚N, 135.661˚W (LACM 87-395, 29).

390 m, SW of mouth of Sitka Sound, SSW of Cape Edgecumbe, S end of Kruzof Island, 56.778˚N, 135.970˚W (LACM 87-356, 25). 274 m, S of Cape Edward, W of Gilmer Bay, Kruzof Island, 57.219˚N, 136.234˚W (LACM 87-354, 17). 408 m, S of Icy Point, W of Point Theodore, Yakobi Island, 57.853˚N, 137.111˚W (LACM 87-346, 1). 214 m, SSW of Cape Fairweather, Chichagof Island, W of Cape Bingham, 58.073˚N, 138.476˚W (LACM 87-330, 3). 384 m, W of Yakobi Island, S of Yakutat Bay, 58.000˚N, 140.000˚W (LACM 87-335, 1). 178 m, SE of Icy Bay, SW of Yakutat Bay, 59.453˚N, 141.150˚W (LACM 87- 336, 1). 353 m, S of Icy Bay, E of Dry Bay, 59.118˚N, 141.495˚E (LACM 87-333, 10).

Remarks. Although well figured by McLean (1996), the identification of this familiar species must be changed, as it is clearly not conspecific with A. crispata (Fleming, 1828) with type locality in Europe. Given the controversial nature of the name, it is prudent for taxon stabilization to designate a neotype. A specimen collected near to the type locality is here so designated. The specimen agrees in all aspects with the original description, though the latter lacks much specific detail. Specimens in the original type repository (USNM) originally identified as kelseyi were examined, and the best specimen was imaged by SEM (USNM 209054). Unfortunately, its protoconch is eroded, which makes generic assignment impossible (see Geiger 2003 for discussion of genera in Anatomidae ). A specimen with preserved protoconch sculpture, agreeing in all aspects of teleoconch morphology with the USNM kelseyi specimens and obtained from near the original type locality, was chosen instead. The generic placement of kelseyi follows from the reticulate sculpture of the protoconch.

Anatoma chiricova (Dall, 1919) had been placed in synonymy with the Pacific A. “ crispata , ” under which also kelseyi was synonymized ( McLean 1967). We do not consider chiricova a synonym of kelseyi either given the more biconical overall shape of the shell of chiricova . The taxon chiricova requires further investigation. The type specimen (USNM 206509) was shown by McLean (1967: pl. 56, fig. 2) as a complete specimen, but has since fragmented most likely due to glass disease (cf. Geiger et al. 2007) as evidenced by crystalline precipitations particularly on the largest fragment of the base (Geiger pers. obs. 3/2007).

A fully extended preserved body was available for examination of external anatomy by light and scanning electron microscopy. The operculum is not attached to the main portion of the metapodium, but to a rather small tissue flap. The attachment area only occupies approximately a wedge of 60˚, or 1/6 of the total area of the operculum. A similar attachment area is also evident in T. peruviana n. sp. and A. n. sp. of Sasaki et al., in press, from which the operculum had been removed. We are unaware of any other gastropod in which the operculum is attached in such a fashion.

The two smooth tentacles located between the cephalic tentacle and the first epipodial tentacles are most likely homologous to what Quinn (1983), Sasaki (1998) and Kano (2009) called the accessory cephalic tentacle. A single suboptic tentacle can be found in some species, but it is more closely associated with the eye, and usually significantly smaller. As these accessory cephalic tentacles are paired, and as fertilization is most likely external and no ciliary tracks are associated with them, it is unlikely that they have any penial function.

The existence of an epipodial sense organ (ESO) in Anatomidae has been uncertain. Here, the nonpapillate stubby projection associated with the first two epipodial tentacles is interpreted as the ESO. Its nonpapillate, blunt nature agrees with typical ESO, which usually, however, are located ventrally to epipodial tentacles and are only about has high as wide (here 3–4 times as high as wide). Sasaki et al. (in press) interpreted the homologous structure in Anatoma n. sp. also as an ESO.

The presumably chemosensory bursicles (see Geiger et al. 2008 for review) were found by Sasaki (1998) in Anatomidae and their presence in the family is here confirmed. The bursicles are distinct, with their typical bottle shape and the opening to the chamber could be seen in several cases.

Figures

FIGURE 16. Thieleella kelseyi. A. Neotype, here designated. 183 m, off La Jolla, California, USA, 32.843 ˚ N, 117.392 ˚ W (SBMNH 3215). Radula shown in Figure 13 A – C. B. Between Tanner Bank and Cortez Bank, California, USA, 32.450 ˚ N, 119.250 ˚ W (SBMNH 33350). Radula shown in Figure 13 D – E. Scale bar shell = 1 mm. Scale bar protoconch = 100 µm.

FIGURE 17. Radula of Thieleella kelseyi. A – C. From here designated neotype, 183 m, off La Jolla, California, USA, 32.843 ˚ N, 117.392 ˚ W (SBMNH 3215). For shell see Figure 12 A. D – E. Between Tanner Bank and Cortez Bank, California, USA, 32.450 ˚ N, 119.250 ˚ W (SBMNH 33350). For shell see Figure 12 B. Scale bars A, D = 500 µm. Scale bars B, C, E. = 50 µm.

FIGURE 18. Preserved body of Thieleella kelseyi. 421 m, 2.3 miles, 48 ˚ T, to S Pt. Light, Santa Rosa Island, California, 33.850 ˚ N, 120.183 ˚ W (LACM 23129). Stereomicroscope images, z-stacked with HeliconFocus. Scale bar = 1 mm. A. Ventral view. B. Lateral view. ct: cephalic tentacle; es: eye stalk; et: epipodial tentacle; j: jaws; m: mantle; mp: metapodium; op: operculum; pp: propodium; sn: snout; st: suboptic tentacle.

FIGURE 19. Preserved body of Thieleella kelseyi. 421 m, 2.3 miles 48 ˚ T to S Pt. Light, Santa Rosa Island, California, 33. 850 ˚ N, 120. 183 ˚ W (LACM 23129). A. Operculum. Scale bar = 1 mm. B. Entire preserved body, hexamethyldisilizane treated. Scale bar = 1 mm. C. Ventral view of anterior portion. Scale bar = 1 mm. D. Ventral view of anterior epipodial tentacles plus ESO. Scale bar = 200 µm. E. Dorsal view of epipodial tentacles and ESO; note biserial papillation of epipodial tentacles. Scale bar = 200 µm. F. Mantle tentacle at posterior end of mantle enlarged. Scale bar = 100 µm. G. Overview of gill and mantle. Fat arrow: direction of view of H. Scale bar = 1 mm. H. Bursicles with openings. Scale bar = 100 µm. Abbreviations: act: accessory cephalic tentacle. b: bursicle. bo: bursicle opening. ct: cephalic tentacle. es: eyestalk. ESO: epipodial sense organ. et: epipodial tentacles. gf: gill filaments. j: jaw. mp: metapodium. mt: mantle tentacle. oaf: operculum attachment flap. op: operculum. opg: opening of propodial gland. pp: propodium. rp: rectal papilla. sn: snout. st. suboptic tentacle.