Auriculella auricula ( Ferussac , 1821)

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 auricula ( Ferussac, 1821) Figures 1A , 3A, B , 4A , 5A

Partula auricula Férussac, 1821: 66.

Auriculella auricula - Gulick 1872: 222; Gulick 1873: 91; Pilsbry and Cooke 1915: 78-80, pl. 24, figs 1-10; Cooke and Kondo 1960: 270-272, figs 113a-e, 114a-c; Cowie et al. 1995: 75; Severns 2011: 206, pl. 80, fig. 2.

Type material.

Neotype: USA • 1; H = 8.7 mm, W = 4.2 mm, AH = 4.6 mm, AW = 3.3 mm, with 6.4 WH; Honolulu County, Oahu, Koolau Mountains, Tantalus; 09 Jun 1943; Y. Tanada leg.; BPBM 189709.

Type locality.

"Sans doute les îles de la mer du Sud?" [without doubt the south sea islands?]; colloquially "sans doute" means probably; here restricted to Tantalus.

Diagnosis.

Shell. Shell dextral or sinistral with flat-sided whorls and an obtuse apex, H = 8.0 ± 0.4 mm, W = 4.3 ± 0.2 mm, WH 6.0 ± 0.2, AH = 4.1 ± 0.2 mm, AW = 3.1 ± 0.2 mm (N = 50; Table 2 ). Columella with a single strong lamella and without an axial ridge. Parietal lamella is strong and smooth and not undulate, extending 0.3 to 0.7 whorls into the aperture. Shell color is tan, brown, or yellowish, often with a single narrow brown or white band (Fig. 3B ). White bands are sometimes bordered by two darker brown bands and apical whorls are often darker brown. Lip reflected, thickened, white or brown in color.

Reproductive system. Phallus retractor muscle relatively long, attached apically to a short but well-defined epiphallus (Fig. 4A ). Appendix is longer than the phallus and about ⅔ the diameter of the phallus at its attachment. The appendix narrows abruptly at ⅕ its length and remains narrow to its terminus. Phallus is broad, narrowing only slightly apically and basally. Atrium is relatively short and broad. Vagina is about ⅓ the length of the phallus.

Radula . Radula with an irregular rachidian flanked on either side by rastriform marginal teeth, as diagnostic of the family (Fig. 5A ). 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. Number of teeth per row range from 177 to 183 (N = 6; Table 2 ).

Distribution and ecology.

Auriculella auricula is endemic to Oahu’s Koolau Mountains (Fig. 1A ), historically found across the range at elevations from 61 m to 305 m. The species is arboreal and found on vegetation including: Cordyline sp. Freycinetia arborea , Metrosideros polymorpha , Canna sp. (BPBM 34025, 49056, 51405), Aleurites moluccanus , Psychotria sp., Zingiber sp., Psidium cattleyanum , Musa sp., Asplenium sp., and unspecified ferns and shrubs. The species has also been recorded on the ground under stones, logs and dead leaves. Live specimens recorded in the BPBM collection were last collected by Y. Kondo in 1946 from Palolo Valley; the species has not been recorded in recent surveys and is considered here possibly extinct.

Remarks.

In the original description, Férussac (1821) provided measurements for a single shell of three lines (6.8 mm) in height and 1¾ lines (4.0 mm) in width. His collection is housed in MNHN where there are two lots labelled A. auricula that are attributed to Férussac. The first (MNHN IM-2000-34306, 34307, 34308) is from Férussac’s collection but does not contain original labels. The three dextral shells are identified as A. auricula from the Mariana Islands, but they are not A. auricula and instead appear to be a gerontic adult and two juveniles similar to Auriculella ambusta , a species not found on the same mountain range as A. auricula . The other lot (MNHN IM-2014-7009) is from the Deshayes collection. Its source is unknown but probably came from Férussac whose specimens Deshayes used to complete Férussac’s "Histoire naturelle des mollusques terrestres et fluviatiles" after Férussac’s death in 1836. The lot contains six specimens of Auriculella pulchra , two of which are sinistral and all of which are larger than 6.8 mm. The two lots are not consistent with Férussac’s description, and we exclude these lots as possible syntypes of A. auricula . We have not located any other type material of A. auricula and we consider the types to be lost. Stabilizing the nomenclature of this species is important because it is the type species of the genus Auriculella , a genus with many similar but conchologically variable and poorly resolved species, nearly all of which are highly endangered. We designate BPBM 18709 (Fig. 3A ) from Tantalus, Oahu as neotype of Auriculella auricula to stabilize the taxonomic status and type locality of the species as well as the genus Auriculella . The neotype matches Férussac’s original description in having an acute ovoid shell with an obtuse apex, strong parietal lamella, and single columellar lamella. The color of the neotype is more tan than yellowish as described in the original description but the species is known to be polymorphic for shell color and pattern as well as chirality. The shell used in Férussac’s description was sinistral while the neotype is dextral. We chose a dextral specimen with slightly different coloration because it was used by Cooke and Kondo (1961) to describe the nervous system and reproductive anatomy of Auriculella auricula thus clearly defining the species as well as the genus. The other four specimens from BPBM 189709 are re-cataloged as BPBM 285783. One of these is a broken shell presumably corresponding to the animal dissected by Cooke and Kondo (1961).

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.