Auriculella minuta Cooke & Pilsbry, 1915

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 minuta Cooke & Pilsbry, 1915 Figures 1B , 3C, D , 4B , 5B

Auriculella minuta Cooke & Pilsbry in Pilsbry & Cooke, 1915: 90, pl. 25, figs 5-9; Cowie et al. 1995: 76; Johnson 1996: 190; Severns 2011: 210, pl. 82, fig. 1.

Type material.

Lectotype: USA • 1, H = 4.9 mm, W = 2.8 mm, AH = 2.2 mm, AW = 1.7 mm, WH = 5.7.; Honolulu County, Oahu, Koolau Mountains, Nuuanu; Nuuanu Valley Ridge 7, east, on ti, lehua, Passiflora foetida ; Cooke leg.; BPBM 42377, here designated

Paralectotypes: USA - Honolulu County, Oahu, Koolau Mountains • 1; Nuuanu Valley; Cooke leg.; BPBM 42377 • 1; Nuuanu Ridge; BPBM 13034 • 2; Nuuanu; BPBM 42379 • 1; Nuuanu Ridge; Cooke leg.; BPBM 42380 • 33; Nuuanu Ridge; Cooke leg.; BPBM 4238 • 1; Nuuanu Valley; Cooke leg.; BPBM 42382 • 82; Nuuanu Valley; Cooke leg.; BPBM 42383 • 5, Palolo Valley; Lyman leg.; BPBM 12808

Paralectotypes not examined. ANSP 91816 (11 spm), ANSP 113294 (10 spm), MCZ 73037 (5 spm), SMF 7127 (4 spm), BPBM 12808 (5 spm).

Possible paralectotype. USA - Honolulu County, Oahu, Koolau Mountains • 6; Palolo Valley; BPBM 16435.

Type locality.

Hawaiian Islands, Oahu, Nuuanu. See

Remarks.

Diagnosis.

Shell. Shell dextral, H = 4.4 ± 0.18 mm, W = 2.7 ± 0.11 mm, WH = 5.1 ± 0.08, AH = 1.9 ± 0.11 mm, AW = 1.3 ± 0.08 mm (N = 50; Table 2 ). Whorls inflated. Columella in juveniles with a strong lamella that is reduced and covered by a thickening of the inner edge of the lip in adults. Some adults show a short projection or angulation where the columellar lamella was located. Adult columella reflected, without an axial ridge. Parietal lamella is smooth and not undulate, extending 0.2 to 0.5 whorls into the aperture. Shell color is pale tan or dark brown, with or without a single peripheral color band of pale tan or dark brown (Fig. 3D , MCZ 73037).

Reproductive system. Phallus retractor muscle relatively long, attached apically to a short but well-defined epiphallus (Fig. 4B ). Appendix is nearly equal in length to the phallus. Appendix the diameter of the phallus at its attachment, narrowing abruptly at ⅓ its length and remaining narrow to its terminus. Apical ¾ of the phallus is broad, basal ¼ narrows abruptly remaining narrow to the junction with the moderately long atrium. Vagina is long and nearly half 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. 5B ). 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 105 teeth per row (N = 5; Table 2 ).

Distribution and ecology.

Auriculella minuta is endemic to Oahu’s Koolau Mountain Range (Fig. 1B ), found predominantly in the southern portion of the range with a few historical records from the southern edge of the northern Koolau Mountains. No elevational range information is available with these historical specimen records. The species is arboreal and found on vegetation, including Cordyline fruticosa , Dioscorea alata , Freycinetia arborea , Kadua affinis , Lobelia sp., Psidium guajava , and Touchardia latifolia . Live specimens recorded in the BPBM collection were last collected by Olaf Oswald in Waiahole in 1931 and is considered herein extinct.

Remarks.

A holotype was not designated in the original description and the type series came from two different localities: Nuuanu collected by Cooke, and Palolo collected by both Cooke and Lyman (Pilsbry and Cooke 1915: 90). Five figures were provided with the original description (Pilsbry and Cooke 1915: pl. 25, figs 5-9) from Nuuanu, which according to the figure caption were based on specimens from BPBM and ANSP. The figure caption did not indicate which museum lots the figured specimens came from but the BPBM ledger in Cooke’s handwriting lists: BPBM 42377 “holotype”, figs 5, 9 (see note for ANSP 91816 below); BPBM 42378, “cotype”, fig. 8 (not ANSP 113294 as stated in Severns, 2011: 210); BPBM 42379 “paratypes”; BPBM 42380, “cotype”, fig. 7; BPBM 42381, “paracotypes”; 42382, “cotype”, fig. 6; BPBM 42383, “paracotypes”. The BPBM ledger documents that BPBM lots were the source of other type material: BPBM 42379 - 83 were the source for SMF 7127 ( Zilch 1962: 78) and BPBM 42379, split from BPBM 13034, was the source lot for MCZ 73037. The ledger also indicated that two specimens were given to Dautzenberg whose collections were obtained by RBINS. Two ANSP lots 91816 and 113294 were received by Pilsbry from Cooke. The original label for ANSP 91816 is marked “cotype” and the source for fig. 9 in the description. Because the caption for figs 5-9 states that at least one of the figured specimens is from ANSP we believe this to be the source for fig. 9 rather than BPBM 42377 as stated in the BPBM ledger, although we do believe BPBM 42377 is the source for fig. 5. Johnson (1996) lists lot BPBM 42377 as the holotype citing the original BPBM specimen labelling. However, the species description is clearly based on multiple specimens all of which should be considered syntypes. In addition to the specimens from Nuuanu, the material from Palolo collected by both Lyman and Cooke are also part of the type series. There is only one lot of Auriculella minuta (BPBM 12808) collected by Lyman from Palolo and although it is not labelled as being part of the type series it is likely the lot collected by Lyman that was mentioned in the species description. A second lot, BPBM 16435, lacks information on the collector but may be the lot collected by Cooke. We here designate lot BPBM 42377 as the lectotype, restricting the type locality to Nuuanu.

Unlike the other species traditionally placed in the perpusilla group, the shell of A. minuta is dextral rather than sinistral. The columella does not bear an axially oriented ridge like the one found in A. perversa . The palatal lamella is smooth and not undulate unlike that of A. gagneorum sp. nov. The epiphallus is short and well defined similar to A. gagneorum sp. nov., but 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 the gently tapered appendix of 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.