Auriculella tenella Ancey, 1889

Yeung, Norine W., Slapcinsky, John, Strong, Ellen E., Kim, Jaynee R. & Hayes, Kenneth A., 2020, Overlooked but not forgotten: the first new extant species of Hawaiian land snail described in 60 years, Auriculella gagneorum sp. nov. (Achatinellidae, Auriculellinae), ZooKeys 950, pp. 1-31 : 1

Auriculella tenella Ancey, 1889 Figures 1E , 3I, J , 4E , 5E

Auriculella tenella Ancey, 1889: 232-233; Pilsbry and Cooke 1915: 99-100, pl. 19, figs 7, 8; Cowie et al. 1995:77; Wood and Gallichan 2008: 88, pl. 2, fig. 8, ix; Severns 2011: 204, pl. 79, fig. 5.

Type material.

Lectotype: USA • 1; H = 6.2 mm, W = 3.5 mm, AH = 2.3 mm, AW = 1.6 mm, WH = 6.6 whorls; Honolulu County, Oahu, Waianae Mountains; Baldwin leg.; BPBM 18943, here designated.

Paralectotypes: USA • 2; Honolulu County, Oahu, Waianae Mountains; Baldwin leg.; BPBM 285811.

Paralectotypes not examined: NMW 1955.158.24126 (1 spm); RBINS 10591 (accession, 1 spm).

Type locality.

"Waianae, dans la partie occidentale de l’île d’Oahu.” [Waianae, western part of Oahu Island].

Diagnosis.

Shell. Shell sinistral with inflated whorls, H = 5.6 ± 0.8 mm, W = 3.0 ± 0.4 mm, WH = 6.5 ± 0.3, AH = 2.0 ± 0.3 mm, AW = 1.9 ± 0.3 mm (N = 50; Table 2 ). Columella in juveniles with two lamellae that are reduced and visible only deep within the aperture of adults. Columellar reflection lacks an axially oriented ridge. Parietal lamella is smooth and not undulate, extending 0.3 to 0.5 whorls into the aperture. Shell color straw to brown, indistinctly streaked with red, with or without a single darker brown marginal spiral band.

Reproductive system. Phallus retractor muscle relatively long attached apically to a short but well-defined epiphallus (Fig. 4E ). Appendix ⅓ longer and about half the diameter of the phallus at its attachment, narrowing abruptly at ⅓ its length and remaining narrow to its terminus. Phallus is broad, narrowing by half at the junction with the short atrium. Vagina is of moderate length.

Radula . Radula with an irregular rachidian flanked on either side by rastriform marginal teeth, as diagnostic of the family (Fig. 5E ). Each tooth has a long narrow base that expands slowly for ¾ of the length of the tooth before reaching the forward curving cusps, which comprise the remaining ¼ of the tooth. There are three long cusps at mesocone, endocone, and ectocone positions with two or more alternating larger and smaller cusps intercalated between them. There are roughly 129 teeth per row (N = 3; Table 2 ).

Distribution and ecology.

Auriculella tenella is endemic to Oahu’s Waianae Mountains, historically found throughout the range between 518 and 1227 m in elevation (Fig. 1E ). This species is arboreal and found on Broussaisia sp., Cordyline sp., Freycinetia arborea , Lantana sp., Pelea sp., Sadleria cyatheoides , Bidens sp., Coprosma sp., Euphorbia sp., Metrosideros sp., Psychotria sp., Ilex sp., Philodendron sp., and unspecified ferns, grasses, tree trunks, and small plants on stream banks. Occasionally, this species has been recorded on the ground on stones, dead leaves, and bark. The last live specimens in the BPBM collection were recorded in 1948. Our recent surveys documented the species in only three locations in the southern Waianae range.

Remarks.

A holotype was not designated in the original description, however, the type locality is listed as “Waianae” and collected by Baldwin. Ancey provided measurements in the original description, "Long., 6; diam., 3; alt. ap., 2 2/3 millim.", which agree well with the designated lectotype. The ledger entry for BPBM 18943 lists four “types” collected by Baldwin from Waialae [sic]. However, only three specimens were found. The material probably came from Paul Geret who acquired Ancey’s collection after his death and subsequently sold it. Much of Ancey’s Hawaiian land and freshwater material was purchased by BPBM in 1908 (Johnson, 1996) but some was sold to other buyers. Both NMW 1955.158.24126 and RBINS 10591 (accession number) have Geret “cotype” labels ( Wood and Gallichan 2008:88). Tomlin, the source of the NMW lot, had a sales list confirming purchase from the Ancey collection.

The shell of A. tenella has approximately seven nearly flat-sided whorls unlike A. auricula , A. minuta , A. perpusilla and A. perversa , which have approximately five whorls, and are inflated in all but A. auricula . Auriculella tenella is sinistral unlike A. minuta and does not bear an axially oriented columellar ridge like A. perversa or an undulating palatal lamella like A. gagneorum sp. nov. The epiphallus is short and well defined unlike the long epiphallus of A. perpusilla or the poorly defined epiphallus of A. perversa . The appendix narrows abruptly at approximately ⅓ its length unlike A. gagneorum sp. nov.

Figures

Figure 1. Distributional map of Auriculella spp. A Auriculella auricula B Auriculella minuta C Auriculella perpusilla D Auriculella perversa E Auriculella tenella and F Auriculella gagneorum sp. nov. Dark grey circle = historical; light grey triangle = since 2010.

Figure 3. Comparative shell morphology of A Auriculella auricula neotype BPBM 18709 B Auriculella auricula shell variation (left to right) BPBM 12651, BPBM 12666 C Auriculella minuta lectotype BPBM 42377 D Auriculella minuta shell variation (left to right) BPBM 12804, paralectotype MCZ 73037 E Auriculella perpusilla holotype MCZ 39912 F Auriculella perpusilla (left to right) BPBM 285806, BPBM 134341 (2 spm), BPBM 134280 white one, BPBM 122643, BPBM 13443 G Auriculella perversa lectotype BPBM 42384, 3 shells H Auriculella perversa shell variation (left to right) paralectotype ANSP 91817 I Auriculella tenella lectotype BPBM 18943 J Auriculella tenella shell variation paralectotype BPBM 109679 K Auriculella gagneorum sp. nov. holotype (BPBM 285843) and L Auriculella gagneorum sp. nov. paratypes, left to right (BPBM 285797, 285794, 285795, 285798). Scale bar: 5 mm.

Figure 4. Comparative reproductive anatomy of A Auriculella auricula BPBM 119141 B Auriculella minuta BPBM 99146 C Auriculella perpusilla BPBM 93626 D Auriculella perversa BPBM 97904 E Auriculella tenella BPBM 211034 F Auriculella gagneorum sp. nov. paratype BPBM 285800. Abbreviatons for reproductive structures are: AG = albumen gland; AP = penial appendix; BC = bursa copulatrix; EP = epiphallus; GP = gonopore; P = penis; OV = free oviduct; PG = prostate gland; PR = penial retractor muscle; UT = uterus; VD = vas deferens. Scale bar: 1 mm.

Figure 5. Comparative radular morphology of A A. auricula B A. minuta C A. perpusilla D A. perversa E A. tenella F A. gagneorum sp. nov. Scale bar: 10 μm.